Search This Blog

Tuesday, April 22, 2025

Speech–language pathology

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Speech%E2%80%93language_pathology
 
Speech–language pathology
Broca's area (speech production) and Wernicke's area (language comprehension)

Speech–language pathology, also known as speech and language pathology or logopedics, is a healthcare and academic discipline concerning the evaluation, treatment, and prevention of communication disorders, including expressive and mixed receptive-expressive language disorders, voice disorders, speech sound disorders, speech disfluency, pragmatic language impairments, and social communication difficulties, as well as swallowing disorders across the lifespan. It is an allied health profession regulated by professional bodies including the American Speech-Language-Hearing Association (ASHA) and Speech Pathology Australia. The field of speech-language pathology is practiced by a clinician known as a speech–language pathologist (SLP) or a speech and language therapist (SLT). SLPs also play an important role in the screening, diagnosis, and treatment of autism spectrum disorder (ASD), often in collaboration with pediatricians and psychologists.

History

The development of speech-language pathology into a profession took different paths in the various regions of the world. Three identifiable trends influenced the evolution of speech-language pathology in the United States during the late 19th century to early 20th century: the elocution movement, scientific revolution, and the rise of professionalism. Groups of "speech correctionists" formed in the early 1900s. The American Academy of Speech Correction was founded in 1925, which became ASHA in 1978.

Profession

Speech–language pathologists (SLPs) provide a wide range of services, mainly on an individual basis, but also as support for families, support groups, and providing information for the general public. SLPs work to assess levels of communication needs, make diagnoses based on the assessments, and then treat the diagnoses or address the needs. Speech/language services begin with initial screening for communication or swallowing disorders and continue with assessment and diagnosis, consultation for the provision of advice regarding management, intervention, and treatment, and providing counseling and other followup services for these disorders. Services are provided in the following areas:

  • Developmental language and early feeding neurodevelopment and prevention;
  • Cognitive aspects of communication (e.g., attention, memory, problem-solving, executive functions);
  • Speech (phonation, articulation, fluency, resonance, and voice including aeromechanical components of respiration);
  • Language (phonology, morphology, syntax, semantics, and pragmatic/social aspects of communication) including comprehension and expression in oral, written, graphic, and manual modalities; language processing; preliteracy and language-based literacy skills, phonological awareness;
  • Augmentative and alternative communication (AAC) for individuals with severe language and communication impairments;
  • Swallowing or other upper aerodigestive functions such as infant feeding and aeromechanical events (evaluation of esophageal function is for the purpose of referral to medical professionals);
  • Voice (hoarseness, dysphonia), poor vocal volume (hypophonia), abnormal (e.g., rough, breathy, strained) vocal quality. Research demonstrates voice therapy to be especially helpful with certain patient populations; individuals with Parkinson's Disease often develop voice issues as a result of their disease.
  • Sensory awareness related to communication, swallowing, or other upper aerodigestive functions.

Speech, language, and swallowing disorders result from a variety of causes, such as a stroke, brain injury, hearing loss, developmental delay, a cleft palate, cerebral palsy, or emotional issues.

A common misconception is that speech–language pathology is restricted to the treatment of articulation disorders (e.g., helping English-speaking individuals enunciate the traditionally difficult r) or the treatment of individuals who stutter but, in fact, speech–language pathology is concerned with a broad scope of speech, language, literacy, swallowing, and voice issues involved in communication, some of which include:

  • Word-finding and other semantic issues, either as a result of a specific language impairment (SLI) such as a language delay or as a secondary characteristic of a more general issue such as dementia.
  • Social communication difficulties involving how people communicate or interact with others (pragmatics).
  • Language impairments, including difficulties creating sentences that are grammatical (syntax) and modifying word meaning (morphology).
  • Literacy impairments (reading and writing) related to the letter-to-sound relationship (phonics), the word-to-meaning relationship (semantics), and understanding the ideas presented in a text (reading comprehension).
  • Voice difficulties, such as a raspy voice, a voice that is too soft, or other voice difficulties that negatively impact a person's social or professional performance.
  • Cognitive impairments (e.g. attention, memory, executive function) to the extent that they interfere with communication.
  • Parent, caregiver, and other communication partner coaching.

Primary pediatric speech and language disorders include: receptive and expressive language disorders, speech sound disorders, childhood apraxia of speech (CAS), stuttering, and language-based learning disabilities. Speech-language pathologists (SLPs) work with people of all ages.

Swallowing disorders include difficulties in any phase of the swallowing process (i.e., oral, pharyngeal, esophageal), as well as functional dysphagia and feeding disorders. Swallowing disorders can occur at any age and can stem from multiple causes.

Multi-discipline collaboration

SLPs collaborate with other health care professionals, often working as part of a multidisciplinary team. They can provide information and referrals to audiologists, physicians, dentists, nurses, nurse practitioners, occupational therapists, rehabilitation psychologists, dietitians, educators, behavior consultants (applied behavior analysis), and parents as dictated by the individual client's needs. For example, the treatment for patients with cleft lip and palate often requires multidisciplinary collaboration. Speech–language pathologists can be very beneficial in helping resolve speech problems associated with cleft lip and palate. Research has indicated that children who receive early language intervention are less likely to develop compensatory error patterns later in life, although speech therapy outcomes are usually better when surgical treatment is performed earlier. Another area of collaboration relates to auditory processing disorders, where SLPs can collaborate in assessments and provide intervention where there is evidence of speech, language, and/or other cognitive-communication disorders.

Working environments

SLPs work in a variety of clinical and educational settings. SLPs work in public and private hospitals, private practices, skilled nursing facilities (SNFs), long-term acute care (LTAC) facilities, hospice, and home healthcare. SLPs may also work as part of the support structure in the education system, working in both public and private schools, colleges, and universities. Some SLPs also work in community health, providing services at prisons and young offenders' institutions or providing expert testimony in applicable court cases.

Some SLPs' working environments include one-on-one time with the client.

Following ASHA's 2005 approval of the delivery of speech/language services via video conference or telepractice, SLPs in the United States have begun to use this service model.

Children with speech, language, and communication needs (SLCN) are particularly at risk of not being heard because of communication challenges. Speech-language pathologists (SLPs) can explain the significance of supporting communication as a tool for the child to shape and influence choices available to them in their lives, even though it is advised that children with SLCN can and should be actively involved as equal partners in decision-making about their communication needs. Building these skills is especially crucial for SLPs working in settings related to traditional education.

Research

SLPs conduct research related to communication sciences and disorders, swallowing disorders, or other upper aerodigestive functions.

Experimental, empirical, and scientific methodologies that build on hypothesis testing and logical, deductive reasoning have dominated research in speech-language pathology. Other types of research in the field are complemented by qualitative research.

Education and training

United States

In the United States, speech–language pathologists must hold a master's degree from an ASHA-accredited program. Following graduation and passing a nation-wide board exam, SLPs typically begin their Clinical Fellowship Year, during which they are granted a provisional license and receive guidance from their supervisor. At the end of this process, SLPs may choose to apply for ASHA's Certificate of Clinical Competence and apply for full state licensure. SLPs may additionally choose to earn advanced degrees such as a clinical doctorate in speech–language pathology, PhD, or EdD.

Methods of assessment

Many approaches exist to assess language, communication, speech and swallowing. Two main aspects of assessment can be to determine the extent of breakdown (impairment-level), or how communication can be supported (functional level). When evaluating impairment-based level of breakdown, therapists are trained to use a cognitive neuropsychological approach to assessment, to precisely determine what aspect of communication is impaired. Some therapists use assessments that are based on historic anatomical models of language, that have since been shown to be unreliable. These tools are often preferred by therapists working within a medical model, where medics request a 'type' of impairment, and a 'severity' rating. The broad tools available allow clinicians to precisely select the aspect of communication that they wish to assess.

Because school-based speech therapy is run under state guidelines and funds, the process of assessment and qualification is more strict. To qualify for in-school speech therapy, students must meet the state's criteria on language testing and speech standardization. Due to such requirements, some students may not be assessed in an efficient time frame or their needs may be undermined by criteria. For a private clinic, students are more likely to qualify for therapy because it is a paid service with more availability.

Clients and patients

Speech–language pathologists work with clients and patients who may present with a wide range of issues.

Infants and children

United States

In the US, some children are eligible to receive speech therapy services, including assessment and lessons through the public school system. If not, private therapy is readily available through personal lessons with a qualified speech–language pathologist or the growing field of telepractice. Teleconferencing tools such as Skype are being used more commonly as a means to access remote locations in private therapy practice, such as in the geographically diverse south island of New Zealand. More at-home or combination treatments have become readily available to address specific types of articulation disorders. The use of mobile applications in speech therapy is also growing as an avenue to bring treatment into the home.

United Kingdom

In the UK, children are entitled to an assessment by local NHS speech- and language-therapy teams, usually after referral by health visitors or education settings, but parents are also entitled to request an assessment directly. If treatment is appropriate, an educational plan will be drawn up. Speech therapists often play a role in multi-disciplinary teams when a child has speech delay or disorder as part of a wider health condition. The Children's Commissioner for England reported in June 2019 that there was a postcode lottery; £291.65 a year per head was spent on services in some areas, while the budget in some areas was £30.94 or less. In 2018, 193,971 children in English primary schools were on the special educational needs register needing speech-therapy services. Speech and language therapists work in acute settings and are often integrated into the MDT in multiple areas of speciality for neonatal, children and adult services. Areas include but not limited to; neonatal care, respiratory, ENT, gastrointestinal, stroke, Neurology,ICU, oncology and geriatric care

Children and adults

Adults

  • Adults with aphasia
  • Adults with mild, moderate, or severe eating, feeding and swallowing difficulties, including dysphagia
  • Adults recovering from significant tumors in the bronchus, lung, oropharynx, breast, and brain
  • Adults with mild, moderate, or severe language difficulties as a result of:
  • Adults seeking transgender-specific voice training, including voice feminization and voice masculinization
    • at

    Speech repetition

    From Wikipedia, the free encyclopedia
    https://en.wikipedia.org/wiki/Speech_repetition

    Children copy with their own mouths the words spoken by the mouths of those around them. That enables them to learn the pronunciation of words not already in their vocabulary.

    Speech repetition occurs when individuals speak the sounds that they have heard another person pronounce or say. In other words, it is the saying by one individual of the spoken vocalizations made by another individual. Speech repetition requires the person repeating the utterance to have the ability to map the sounds that they hear from the other person's oral pronunciation to similar places and manners of articulation in their own vocal tract.

    Such speech imitation often occurs independently of speech comprehension such as in speech shadowing in which people automatically say words heard in earphones, and the pathological condition of echolalia in which people reflexively repeat overheard words. That links to speech repetition of words being separate in the brain to speech perception. Speech repetition occurs in the dorsal speech processing stream, and speech perception occurs in the ventral speech processing stream. Repetitions are often incorporated unawares by that route into spontaneous novel sentences immediately or after delay after the storage in phonological memory.

    In humans, the ability to map heard input vocalizations into motor output is highly developed because of the copying ability playing a critical role in children's rapid expansion of their spoken vocabulary. In older children and adults, that ability remains important, as it enables the continued learning of novel words and names and additional languages. That repetition is also necessary for the propagation of language from generation to generation. It has also been suggested that the phonetic units out of which speech is made have been selected upon by the process of vocabulary expansion and vocabulary transmissions because children prefer to copy words in terms of more easily imitated elementary units.

    Properties

    Automatic

    Vocal imitation happens quickly: words can be repeated within 250-300 milliseconds both in normals (during speech shadowing) and during echolalia. The imitation of speech syllables possibly happens even more quickly: people begin imitating the second phone in the syllable [ao] earlier than they can identify it (out of the set [ao], [aƦ] and [ai]). Indeed, "...simply executing a shift to [o] upon detection of a second vowel in [ao] takes very little longer than does interpreting and executing it as a shadowed response". Neurobiologically this suggests "...that the early phases of speech analysis yield information which is directly convertible to information required for speech production". Vocal repetition can be done immediately as in speech shadowing and echolalia. It can also be done after the pattern of pronunciation is stored in short-term memory or long-term memory. It automatically uses both auditory and where available visual information about how a word is produced.

    The automatic nature of speech repetition was noted by Carl Wernicke, the late nineteenth century neurologist, who observed that "The primary speech movements, enacted before the development of consciousness, are reflexive and mimicking in nature..".

    Independent of speech

    Vocal imitation arises in development before speech comprehension and also babbling: 18-week-old infants spontaneously copy vocal expressions provided the accompanying voice matches. Imitation of vowels has been found as young as 12 weeks. It is independent of native language, language skills, word comprehension and a speaker's intelligence. Many autistic and some mentally disabled people engage in the echolalia of overheard words (often their only vocal interaction with others) without understanding what they echo. Reflex uncontrolled echoing of others words and sentences occurs in roughly half of those with Gilles de la Tourette syndrome. The ability to repeat words without comprehension also occurs in mixed transcortical aphasia where it links to the sparing of the short-term phonological store.

    The ability to repeat and imitate speech sounds occurs separately to that of normal speech. Speech shadowing provides evidence of a 'privileged' input/output speech loop that is distinct to the other components of the speech system. Neurocognitive research likewise finds evidence of a direct (nonlexical) link between phonological analysis input and motor programming output.

    Effector independent

    Speech sounds can be imitatively mapped into vocal articulations in spite of vocal tract anatomy differences in size and shape due to gender, age and individual anatomical variability. Such variability is extensive making input output mapping of speech more complex than a simple mapping of vocal track movements. The shape of the mouth varies widely: dentists recognize three basic shapes of palate: trapezoid, ovoid, and triangular; six types of malocclusion between the two jaws; nine ways teeth relate to the dental arch and a wide range of maxillary and mandible deformities. Vocal sound can also vary due to dental injury and dental caries. Other factors that do not impede the sensory motor mapping needed for vocal imitation are gross oral deformations such as hare-lips, cleft palates or amputations of the tongue tip, pipe smoking, pencil biting and teeth clinching (such as in ventriloquism). Paranasal sinuses vary between individuals 20-fold in volume, and differ in the presence and the degree of their asymmetry.

    Diverse linguistic vocalizations

    Vocal imitation occurs potentially in regard to a diverse range of phonetic units and types of vocalization. The world's languages use consonantal phones that differ in thirteen imitable vocal tract place of articulations (from the lips to the glottis). These phones can potentially be pronounced with eleven types of imitable manner of articulations (nasal stops to lateral clicks). Speech can be copied in regard to its social accent, intonation, pitch and individuality (as with entertainment impersonators). Speech can be articulated in ways which diverge considerably in speed, timbre, pitch, loudness and emotion. Speech further exists in different forms such as song, verse, scream and whisper. Intelligible speech can be produced with pragmatic intonation and in regional dialects and foreign accents. These aspects are readily copied: people asked to repeat speech-like words imitate not only phones but also accurately other pronunciation aspects such as fundamental frequency, schwa-syllable expression, voice spectra and lip kinematics, voice onset times, and regional accent.

    Language acquisition

    Vocabulary expansion

    In 1874 Carl Wernicke proposed that the ability to imitate speech plays a key role in language acquisition. This is now a widely researched issue in child development. A study of 17,000 one and two word utterances made by six children between 18 months to 25 months found that, depending upon the particular infant, between 5% and 45% of their words might be mimicked. These figures are minima since they concern only immediately heard words. Many words that may seem spontaneous are in fact delayed imitations heard days or weeks previously. At 13 months children who imitate new words (but not ones they already know) show a greater increase in noun vocabulary at four months and non noun vocabulary at eight months. A major predictor of vocabulary increase in both 20 months, 24 months, and older children between 4 and 8 years is their skill in repeating nonword phone sequences (a measure of mimicry and storage). This is also the case with children with Down's syndrome . The effect is larger than even age: in a study of 222 two-year-old children that had spoken vocabularies ranging between 3–601 words the ability to repeat nonwords accounted for 24% of the variance compared to 15% for age and 6% for gender (girls better than boys).

    Nonvocabulary expansion uses of imitation

    Imitation provides the basis for making longer sentences than children could otherwise spontaneously make on their own.[35] Children analyze the linguistic rules, pronunciation patterns, and conversational pragmatics of speech by making monologues (often in crib talk) in which they repeat and manipulate in word play phrases and sentences previously overheard.[36] Many proto-conversations involve children (and parents) repeating what each other has said in order to sustain social and linguistic interaction. It has been suggested that the conversion of speech sound into motor responses helps aid the vocal "alignment of interactions" by "coordinating the rhythm and melody of their speech".[37] Repetition enables immigrant monolingual children to learn a second language by allowing them to take part in 'conversations'.[38] Imitation related processes aids the storage of overheard words by putting them into speech based short- and long-term memory.[39]

    Language learning

    The ability to repeat nonwords predicts the ability to learn second-language vocabulary.[40] A study found that adult polyglots performed better in short-term memory tasks such as repeating nonword vocalizations compared to nonpolyglots though both are otherwise similar in general intelligence, visuo-spatial short-term memory and paired-associate learning ability.[41] Language delay in contrast links to impairments in vocal imitation.[42]

    Speech repetition and phones

    Electrical brain stimulation research upon the human brain finds that 81% of areas that show disruption of phone identification are also those in which the imitating of oral movements is disrupted and vice versa;[43] Brain injuries in the speech areas show a 0.9 correlation between those causing impairments to the copying of oral movements and those impairing phone production and perception.[44]

    Mechanism

    Spoken words are sequences of motor movements organized around vocal tract gesture motor targets.[45] Vocalization due to this is copied in terms of the motor goals that organize it rather than the exact movements with which it is produced. These vocal motor goals are auditory. According to James Abbs[46] 'For speech motor actions, the individual articulatory movements would not appear to be controlled with regard to three- dimensional spatial targets, but rather with regard to their contribution to complex vocal tract goals such as resonance properties (e.g., shape, degree of constriction) and or aerodynamically significant variables'. Speech sounds also have duplicable higher-order characteristics such as rates and shape of modulations and rates and shape of frequency shifts.[47] Such complex auditory goals (which often link—though not always—to internal vocal gestures) are detectable from the speech sound which they create.

    Neurology

    Dorsal speech processing stream function

    Two cortical processing streams exist: a ventral one which maps sound onto meaning, and a dorsal one, that maps sound onto motor representations. The dorsal stream projects from the posterior Sylvian fissure at the temporoparietal junction, onto frontal motor areas, and is not normally involved in speech perception.[48] Carl Wernicke identified a pathway between the left posterior superior temporal sulcus (a cerebral cortex region sometimes called the Wernicke's area) as a centre of the sound "images" of speech and its syllables that connected through the arcuate fasciculus with part of the inferior frontal gyrus (sometimes called the Broca's area) responsible for their articulation.[6] This pathway is now broadly identified as the dorsal speech pathway, one of the two pathways (together with the ventral pathway) that process speech.[49] The posterior superior temporal gyrus is specialized for the transient representation of the phonetic sequences used for vocal repetition.[50] Part of the auditory cortex also can represent aspects of speech such as its consonantal features.[51]

    Mirror neurons

    Mirror neurons have been identified that both process the perception and production of motor movements. This is done not in terms of their exact motor performance but an inference of the intended motor goals with which it is organized.[52] Mirror neurons that both perceive and produce the motor movements of speech have been identified.[53] Speech is mirrored constantly into its articulations since speakers cannot know in advance that a word is unfamiliar and in need of repetition—which is only learnt after the opportunity to map it into articulations has gone. Thus, speakers if they are to incorporate unfamiliar words into their spoken vocabulary must by default map all spoken input.[54]

    Sign language

    Words in sign languages, unlike those in spoken ones, are made not of sequential units but of spatial configurations of subword unit arrangements, the spatial analogue of the sonic-chronological morphemes of spoken language.[55] These words, like spoken ones, are learnt by imitation. Indeed, rare cases of compulsive sign-language echolalia exist in otherwise language-deficient deaf autistic individuals born into signing families.[55] At least some cortical areas neurobiologically active during both sign and vocal speech, such as the auditory cortex, are associated with the act of imitation.[56]

    Nonhuman animals

    Birds

    Birds learn their songs from those made by other birds. In several examples, birds show highly developed repetition abilities: the Sri Lankan Greater racket-tailed drongo (Dicrurus paradiseus) copies the calls of predators and the alarm signals of other birds[57] Albert's lyrebird (Menura alberti) can accurately imitate the satin bowerbird (Ptilonorhynchus violaceus),[58]

    Research upon avian vocal motor neurons finds that they perceive their song as a series of articulatory gestures as in humans.[59] Birds that can imitate humans, such as the Indian hill myna (Gracula religiosa), imitate human speech by mimicking the various speech formants, created by changing the shape of the human vocal tract, with different vibration frequencies of its internal tympaniform membrane.[60] Indian hill mynahs also imitate such phonetic characteristics as voicing, fundamental frequencies, formant transitions, nasalization, and timing, through their vocal movements are made in a different way from those of the human vocal apparatus.[60]

    Nonhuman mammals

    Apes

    Apes taught language show an ability to imitate language signs with chimpanzees such as Washoe who was able to learn with his arms a vocabulary of 250 American Sign Language gestures. However, such human trained apes show no ability to imitate human speech vocalizations.
    at

    Monday, April 21, 2025

    Introduction to genetics

    From Wikipedia, the free encyclopedia
    https://en.wikipedia.org/wiki/Introduction_to_genetics

    Genetics is the study of genes and tries to explain what they are and how they work. Genes are how living organisms inherit features or traits from their ancestors; for example, children usually look like their parents because they have inherited their parents' genes. Genetics tries to identify which traits are inherited and to explain how these traits are passed from generation to generation.

    Some traits are part of an organism's physical appearance, such as eye color or height. Other sorts of traits are not easily seen and include blood types or resistance to diseases. Some traits are inherited through genes, which is the reason why tall and thin people tend to have tall and thin children. Other traits come from interactions between genes and the environment, so a child who inherited the tendency of being tall will still be short if poorly nourished. The way our genes and environment interact to produce a trait can be complicated. For example, the chances of somebody dying of cancer or heart disease seems to depend on both their genes and their lifestyle.

    Genes are made from a long molecule called DNA, which is copied and inherited across generations. DNA is made of simple units that line up in a particular order within it, carrying genetic information. The language used by DNA is called genetic code, which lets organisms read the information in the genes. This information is the instructions for the construction and operation of a living organism.

    The information within a particular gene is not always exactly the same between one organism and another, so different copies of a gene do not always give exactly the same instructions. Each unique form of a single gene is called an allele. As an example, one allele for the gene for hair color could instruct the body to produce much pigment, producing black hair, while a different allele of the same gene might give garbled instructions that fail to produce any pigment, giving white hair. Mutations are random changes in genes and can create new alleles. Mutations can also produce new traits, such as when mutations to an allele for black hair produce a new allele for white hair. This appearance of new traits is important in evolution.

    Genes and inheritance

    A section of DNA; the sequence of the plate-like units (nucleotides) in the center carries information.

    Genes are pieces of DNA that contain information for the synthesis of ribonucleic acids (RNAs) or polypeptides. Genes are inherited as units, with two parents dividing out copies of their genes to their offspring. Humans have two copies of each of their genes, but each egg or sperm cell only gets one of those copies for each gene. An egg and sperm join to form a zygote with a complete set of genes. The resulting offspring has the same number of genes as their parents, but for any gene, one of their two copies comes from their father and one from their mother.

    Example of mixing

    The effects of mixing depend on the types (the alleles) of the gene. If the father has two copies of an allele for red hair, and the mother has two copies for brown hair, all their children get the two alleles that give different instructions, one for red hair and one for brown. The hair color of these children depends on how these alleles work together. If one allele dominates the instructions from another, it is called the dominant allele, and the allele that is overridden is called the recessive allele. In the case of a daughter with alleles for both red and brown hair, brown is dominant and she ends up with brown hair.

    A Punnett square showing how two brown haired parents can have red or brown haired children. 'B' is for brown and 'b' is for red.
    Red hair is a recessive trait.

    Although the red color allele is still there in this brown-haired girl, it doesn't show. This is a difference between what is seen on the surface (the traits of an organism, called its phenotype) and the genes within the organism (its genotype). In this example, the allele for brown can be called "B" and the allele for red "b". (It is normal to write dominant alleles with capital letters and recessive ones with lower-case letters.) The brown hair daughter has the "brown hair phenotype" but her genotype is Bb, with one copy of the B allele, and one of the b allele.

    Now imagine that this woman grows up and has children with a brown-haired man who also has a Bb genotype. Her eggs will be a mixture of two types, one sort containing the B allele, and one sort the b allele. Similarly, her partner will produce a mix of two types of sperm containing one or the other of these two alleles. When the transmitted genes are joined up in their offspring, these children have a chance of getting either brown or red hair, since they could get a genotype of BB = brown hair, Bb = brown hair or bb = red hair. In this generation, there is, therefore, a chance of the recessive allele showing itself in the phenotype of the children—some of them may have red hair like their grandfather.

    Many traits are inherited in a more complicated way than the example above. This can happen when there are several genes involved, each contributing a small part to the result. Tall people tend to have tall children because their children get a package of many alleles that each contribute a bit to how much they grow. However, there are not clear groups of "short people" and "tall people", like there are groups of people with brown or red hair. This is because of the large number of genes involved; this makes the trait very variable and people are of many different heights. Despite a common misconception, the green/blue eye traits are also inherited in this complex inheritance model. Inheritance can also be complicated when the trait depends on the interaction between genetics and environment. For example, malnutrition does not change traits like eye color, but can stunt growth.

    How genes work

    Genes make proteins

    Main article: Genetic code

    The function of genes is to provide the information needed to make molecules called proteins in cells. Cells are the smallest independent parts of organisms: the human body contains about 100 trillion cells, while very small organisms like bacteria are just a single cell. A cell is like a miniature and very complex factory that can make all the parts needed to produce a copy of itself, which happens when cells divide. There is a simple division of labor in cells—genes give instructions and proteins carry out these instructions, tasks like building a new copy of a cell, or repairing the damage. Each type of protein is a specialist that only does one job, so if a cell needs to do something new, it must make a new protein to do this job. Similarly, if a cell needs to do something faster or slower than before, it makes more or less of the protein responsible. Genes tell cells what to do by telling them which proteins to make and in what amounts.

    Genes are expressed by being transcribed into RNA, and this RNA then translated into protein.

    Proteins are made of a chain of 20 different types of amino acid molecules. This chain folds up into a compact shape, rather like an untidy ball of string. The shape of the protein is determined by the sequence of amino acids along its chain and it is this shape that, in turn, determines what the protein does. For example, some proteins have parts of their surface that perfectly match the shape of another molecule, allowing the protein to bind to this molecule very tightly. Other proteins are enzymes, which are like tiny machines that alter other molecules.

    The information in DNA is held in the sequence of the repeating units along the DNA chain. These units are four types of nucleotides (A, T, G and C) and the sequence of nucleotides stores information in an alphabet called the genetic code. When a gene is read by a cell the DNA sequence is copied into a very similar molecule called RNA (this process is called transcription). Transcription is controlled by other DNA sequences (such as promoters), which show a cell where genes are, and control how often they are copied. The RNA copy made from a gene is then fed through a structure called a ribosome, which translates the sequence of nucleotides in the RNA into the correct sequence of amino acids and joins these amino acids together to make a complete protein chain. The new protein then folds up into its active form. The process of moving information from the language of RNA into the language of amino acids is called translation.

    DNA replication. DNA is unwound and nucleotides are matched to make two new strands.

    If the sequence of the nucleotides in a gene changes, the sequence of the amino acids in the protein it produces may also change—if part of a gene is deleted, the protein produced is shorter and may not work anymore. This is the reason why different alleles of a gene can have different effects on an organism. As an example, hair color depends on how much of a dark substance called melanin is put into the hair as it grows. If a person has a normal set of the genes involved in making melanin, they make all the proteins needed and they grow dark hair. However, if the alleles for a particular protein have different sequences and produce proteins that can't do their jobs, no melanin is produced and the person has white skin and hair (albinism).

    Genes are copied

    Main article: DNA replication

    Genes are copied each time a cell divides into two new cells. The process that copies DNA is called DNA replication. It is through a similar process that a child inherits genes from its parents when a copy from the mother is mixed with a copy from the father.

    DNA can be copied very easily and accurately because each piece of DNA can direct the assembly of a new copy of its information. This is because DNA is made of two strands that pair together like the two sides of a zipper. The nucleotides are in the center, like the teeth in the zipper, and pair up to hold the two strands together. Importantly, the four different sorts of nucleotides are different shapes, so for the strands to close up properly, an A nucleotide must go opposite a T nucleotide, and a G opposite a C. This exact pairing is called base pairing.

    When DNA is copied, the two strands of the old DNA are pulled apart by enzymes; then they pair up with new nucleotides and then close. This produces two new pieces of DNA, each containing one strand from the old DNA and one newly made strand. This process is not predictably perfect as proteins attach to a nucleotide while they are building and cause a change in the sequence of that gene. These changes in the DNA sequence are called mutations. Mutations produce new alleles of genes. Sometimes these changes stop the functioning of that gene or make it serve another advantageous function, such as the melanin genes discussed above. These mutations and their effects on the traits of organisms are one of the causes of evolution.

    Genes and evolution

    Further information: Introduction to evolution, History of evolutionary thought, and Evolutionary developmental biology
    Mice with different coat colors

    A population of organisms evolves when an inherited trait becomes more common or less common over time. For instance, all the mice living on an island would be a single population of mice: some with white fur, some gray. If over generations, white mice became more frequent and gray mice less frequent, then the color of the fur in this population of mice would be evolving. In terms of genetics, this is called an increase in allele frequency.

    Alleles become more or less common either by chance in a process called genetic drift or by natural selection. In natural selection, if an allele makes it more likely for an organism to survive and reproduce, then over time this allele becomes more common. But if an allele is harmful, natural selection makes it less common. In the above example, if the island were getting colder each year and snow became present for much of the time, then the allele for white fur would favor survival since predators would be less likely to see them against the snow, and more likely to see the gray mice. Over time white mice would become more and more frequent, while gray mice less and less.

    Mutations create new alleles. These alleles have new DNA sequences and can produce proteins with new properties. So if an island was populated entirely by black mice, mutations could happen creating alleles for white fur. The combination of mutations creating new alleles at random, and natural selection picking out those that are useful, causes an adaptation. This is when organisms change in ways that help them to survive and reproduce. Many such changes, studied in evolutionary developmental biology, affect the way the embryo develops into an adult body.

    Inherited diseases

    Some diseases are hereditary and run in families; others, such as infectious diseases, are caused by the environment. Other diseases come from a combination of genes and the environment. Genetic disorders are diseases that are caused by a single allele of a gene and are inherited in families. These include Huntington's disease, cystic fibrosis or Duchenne muscular dystrophy. Cystic fibrosis, for example, is caused by mutations in a single gene called CFTR and is inherited as a recessive trait.

    Other diseases are influenced by genetics, but the genes a person gets from their parents only change their risk of getting a disease. Most of these diseases are inherited in a complex way, with either multiple genes involved, or coming from both genes and the environment. As an example, the risk of breast cancer is 50 times higher in the families most at risk, compared to the families least at risk. This variation is probably due to a large number of alleles, each changing the risk a little bit. Several of the genes have been identified, such as BRCA1 and BRCA2, but not all of them. However, although some of the risks are genetic, the risk of this cancer is also increased by being overweight, heavy alcohol consumption and not exercising. A woman's risk of breast cancer, therefore, comes from a large number of alleles interacting with her environment, so it is very hard to predict.

    Genetic engineering

    Main article: Genetic engineering

    Since traits come from the genes in a cell, putting a new piece of DNA into a cell can produce a new trait. This is how genetic engineering works. For example, rice can be given genes from a maize and a soil bacteria so the rice produces beta-carotene, which the body converts to vitamin A. This can help children with Vitamin A deficiency. Another gene being put into some crops comes from the bacterium Bacillus thuringiensis; the gene makes a protein that is an insecticide. The insecticide kills insects that eat the plants but is harmless to people. In these plants, the new genes are put into the plant before it is grown, so the genes are in every part of the plant, including its seeds. The plant's offspring inherit the new genes, which has led to concern about the spread of new traits into wild plants.

    The kind of technology used in genetic engineering is also being developed to treat people with genetic disorders in an experimental medical technique called gene therapy. However, here the new, properly working gene is put in targeted cells, not altering the chance of future children inheriting the disease causing alleles.

    at

    Transcortical sensory aphasia

    Transcortical sensory aphasia (TSA) is a kind of aphasia that involves damage to specific areas of the temporal lobe of the brain, resulting in symptoms such as poor auditory comprehension, relatively intact repetition, and fluent speech with semantic paraphasias present. TSA is a fluent aphasia similar to Wernicke's aphasia (receptive aphasia), with the exception of a strong ability to repeat words and phrases. The person may repeat questions rather than answer them ("echolalia").

    In all of these ways, TSA is very similar to a more commonly known language disorder, receptive aphasia. However, transcortical sensory aphasia differs from receptive aphasia in that patients still have intact repetition and exhibit echolalia, or the compulsive repetition of words. Transcortical sensory aphasia cannot be diagnosed through brain imaging techniques such as functional magnetic resonance imaging (fMRI), as the results are often difficult to interpret. Therefore, clinicians rely on language assessments and observations to determine if a patient presents with the characteristics of TSA. Patients diagnosed with TSA have shown partial recovery of speech and comprehension after beginning speech therapy. Speech therapy methods for patients with any subtype of aphasia are based on the principles of learning and neuroplasticity. Clinical research on TSA is limited because it occurs so infrequently in patients with aphasia that it is very difficult to perform systematic studies.

    TSA should not be confused with transcortical motor aphasia (TMA), which is characterized by nonfluent speech output, with good comprehension and repetition. Patients with TMA have impaired writing skills, difficulty speaking and difficulty maintaining a clear thought process. Furthermore, TMA is caused by lesions in cortical motor areas of the brain as well as lesions in the anterior portion of the basal ganglia, and can be seen in patients with expressive aphasia.

    Affected brain areas

    Damage to the inferior left temporal lobe, which is shown in green, is associated with TSA.

    Transcortical sensory aphasia is caused by lesions in the inferior left temporal lobe of the brain located near Wernicke's area, and is usually due to minor hemorrhage or contusion in the temporal lobe, or infarcts of the left posterior cerebral artery (PCA). One function of the arcuate fasciculus is the connection between Wernicke’s and Broca’s area. In TSA Wernicke’s and Broca’s areas are spared, meaning that lesions do not occur in these regions of the brain. However, since the arcuate fasciculus, Wernicke's area, and Broca's area are secluded from the rest of the brain in TSA, patients still have intact repetition (as information from the arcuate fasciculus is relayed to Broca’s area), but cannot attach meaning to words, either spoken or heard.

    Characteristics

    Transcortical sensory aphasia is characterized as a fluent aphasia. Fluency is determined by direct qualitative observation of the patient’s speech to determine the length of spoken phrases, and is usually characterized by a normal or rapid rate; normal phrase length, rhythm, melody, and articulatory agility; and normal or paragrammatic speech. Transcortical sensory aphasia is a disorder in which there is a discrepancy between phonological processing, which remains intact, and lexical-semantic processing, which is impaired.[6] Therefore, patients can repeat complicated phrases, however they lack comprehension and propositional speech. This disconnect occurs since Wernicke’s area is not damaged in patients with TSA, therefore repetition is spared while comprehension is affected. Patients with intact repetition can repeat both simple and complex phrases spoken by others, e.g. when asked if the patient would like to go for a walk, he or she would respond "go for walk." Although patients can respond appropriately, due to the extent of their TSA, it is most likely that they do not comprehend what others ask them. In addition to problems in comprehension, transcortical sensory aphasia is further characterized based on deficits in naming and paraphasia.

    Verbal comprehension

    Impaired verbal comprehension can be the result a number of causes such as failure of speech sound discrimination, word recognition, auditory working memory, or syntactic structure building. When clinically examined, patients with TSA will exhibit poor comprehension of verbal commands. Based on the extent of the comprehension deficiency, patients will have difficulty following simple commands, e.g. “close your eyes.” Depending on the extent of affected brain area, patients are able to follow simple commands but may not be able to comprehend more difficult, multistep commands, e.g. “point to the ceiling, then touch your left ear with your right hand." Verbal commands as such, that require the patient to cross over the midline of their body are typically more taxing than commands that involve solely the right or left side. When increasing the complexity of verbal commands comprehension is often tested by varying the grammatical structure of the command to determine whether or not the patient understands different grammatical variations of the same sentence. Commands involving the passive voice or possessive, e.g. "If the snake killed the mouse, which one is still alive," usually result in comprehension problems in those who can understand simple questions.

    Naming

    Naming involves the ability to recall an object. Patients with TSA, as well as patients with all other aphasia subtypes, exhibit poor naming. Clinical assessment of naming involves the observer first asking the patient to name high frequency objects such as clock, door, and chair. TSA patients who name common objects with ease generally have difficulty naming both uncommon objects and specific parts of objects such as lapel, or the dial on a watch.

    Paraphasia

    Patients with TSA typically exhibit paraphasia; their speech is fluent but often error-prone. Their speech is often unintelligible as they tend to use the wrong words, e.g. tree instead of train or uses words in senseless and incorrect combinations.

    Diagnosis

    Clinical assessment

    Sensory aphasia is typically diagnosed by non-invasive evaluations. Neurologists, neuropsychologists or speech pathologists will administer oral evaluations to determine the extent of a patient’s comprehension and speech capability. Initial assessment will determine if the cause of linguistic deficiency is aphasia. If the diagnosis is then confirmed, testing will next address the type of aphasia and its severity. The Boston Diagnostic Aphasia Examination specializes in determining the severity of a sensory aphasia through the observation of conversational behaviors. Several modalities of perception and response are observed in conjunction with the subject’s ability to process sensory information. The location of the brain lesion and type of the aphasia can then be inferred from the observed symptoms. The Minnesota Test for Differential Diagnosis is the most lengthy and thorough assessment of sensory aphasia. It pinpoints weaknesses in the auditory and visual senses, as well as reading comprehension. From this differential diagnosis, a patient’s course of treatment can be determined. After treatment planning, the Porch Index of Communicative Ability is used to evaluate prognosis and the degree of recovery.

    Imaging

    fMRI is a measure of the increase in blood flow to localized areas of the brain that coincide with neural activity and is used to image brain activity related to a specific task or sensory process. It is a commonly used method for imaging brain activity in aphasia patients.

    Sensory aphasia cannot be diagnosed through the use of imaging techniques. Differences in cognition between asymptomatic subjects and affected patients can be observed via functional magnetic resonance imaging (fMRI). However, these results only reveal temporal differences in cognition between control and diagnosed subjects. The degree of progression during therapy can also be surveyed through cognition tests monitored by fMRI. Many patients’ progress is assessed over time via repeated testing and corresponding cerebral imaging by fMRI.

    Management

    Due to advances in modern neuroimaging, scientists have been able to gain a better understanding of how language is learned and comprehended. Based on the new data from the world of neuroscience, improvements can be made in coping with the disorder.

    Therapists have been developing multiple methods of improving speech and comprehension. These techniques utilize three general principles: maximizing therapy occurrences, ensuring behavioral and communicative relevance, and allowing patients to focus on the language tools that are still available in his or her repertoire.

    Many of the following treatment techniques are used to improve auditory comprehension in patients with aphasia:

    • Using common words
    • Using concrete nouns is more effective than using adjectives, adverbs, or verbs
    • Using action verbs that are easily imagined
    • Concise and grammatically simple sentences as opposed to lengthy sentences
    • Speaking slowly, repeating oneself several times when conversing with aphasic patients
    • Using gestures

    A relatively new method of language therapy involves coincidence learning. Coincidence learning focuses on the simultaneous learning of two or more events and stipulates that these events are wired together in the brain, strengthening the learning process. Therapists use coincidence learning to find and improve language correlations or coincidences that have been either damaged or deleted by severe cases of aphasia, such as transcortical sensory aphasia. This technique is important in brain function and recovery, as it strengthens associated brain areas that remain unaffected after brain damage. It can be achieved with intensive therapy hours in order to maximize time where correlation is emphasized.

    Through careful analysis of neuroimaging studies, a correlation has been developed with motor function and the understanding of action verbs. For example, leg and motor areas were seen to be activated words such as "kick", leading scientists to understand the connection between motor and language processes in the brain. This is yet another example of using relationships that are related in the brain for the purpose of rehabilitating speech and comprehension.

    Of huge importance in aphasia therapy is the need to start practicing as soon as possible.[citation needed] Greater recovery occurs when a patient attempts to improve their comprehension and speaking soon after aphasia occurs. There is an inverse relationship between the length of time spent not practicing and level of recovery. The patient should be pushed to their limits of verbal communication in order for them to practice and build upon their remaining language skills.

    One effective therapy technique is using what are known as language games in order to encourage verbal communication. One famous example is known as "Builder's Game", where a 'builder' and a 'helper' must communicate in order to effectively work on a project. The helper must hand the builder the tools he or she may need, which requires effective oral communication. The builder succeeds by requesting tools from the assistant by usually using single word utterances, such as 'hammer' or 'nail'. Thus, when the helper hands the tool to the builder, the game incorporates action with language, a key therapy technique. The assistant would then hand the builder the requested tool. Success of the game occurs when the builder's requests are specific to ensure successful building.

    Ultimately, regardless of therapy plan or method, improvement in speech does not appear overnight; it requires a significant time investment by the patient as well as a dedicated speech therapist seeking to ensure that the patient is focusing on the correct speech tasks outside of the clinic. Furthermore, the patient must collaborate with friends and family members during their free time in order to maximize the efficacy of the treatment.

    at
    Subscribe to: Posts (Atom)

    Ethics

    From Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Ethics Ethics is the philosophical ...

    • Islamic State and the Levant
      From Wikipedia, the free encyclopedia Islamic State of Iraq and the Levant Ų§Ł„ŲÆŁˆŁ„Ų© Ų§Ł„Ų„Ų³Ł„Ų§Ł…ŁŠŲ© ŁŁŠ Ų§Ł„Ų¹Ų±Ų§Ł‚ ŁˆŲ§Ł„Ų“Ų§Ł…   ( ...
    • Heart Sutra
      From Wikipedia, the free encyclopedia A reproduction of the palm -leaf manuscript in Siddham script ...
    • Wiki
      From Wikipedia, the free encyclopedia Ward Cunningham , inventor of the wiki   A wiki is a website on whi...