The contralateral organization of the forebrain (Latin: contra‚ against; latus‚ side; lateral‚ sided) is the property that the hemispheres of the cerebrum and the thalamus
represent mainly the contralateral side of the body. Consequently, the
left side of the forebrain mostly represents the right side of the body,
and the right side of the brain primarily represents the left side of
the body. The contralateral organization involves both executive and
sensory functions (e.g., a left-sided brain lesion may cause a right-sided hemiplegia). The contralateral organization is only present in vertebrates.
According to the current theory, the forebrain is twisted about the long axis of the body, so that not only the left and right sides, but also dorsal and ventral sides, are interchanged.
Anatomy
Some afferent decussations.Pyramidal decussations.
Two of the cranial nerves show chiasmas: (1) the chiasm of the optic tract (i.e., cranial nerve II), which originates from the eyes and inserts on the optic tectum of the midbrain; and (2) the trochlear nerve
(i.e., cranial nerve IV), which originates in the ventral midbrain and
innervates one of the six muscles that rotate the eye (i.e., the superior oblique muscle).
Although
the forebrain of all vertebrates shows a contralateral organization,
this contralaterality is by no means complete. Some of these exceptions
are worth mentioning:
Olfaction (i.e., smelling sense) is a noteworthy exception. Each olfactory lobe connects to the ipsilateral centers of the frontal cerebrum.
In chondrichthyans (e.g., sharks and skates), the thalamus does not retrieve a branch from the optic tract but only from the contralateral optic tectum, so that the optic path decussates twice, and the forebrain represents the ipsilateral eye.
Most afferent and efferent
connections of the forebrain have bilateral components, especially
outside the primary sensory and motor regions. As a result, a hemiplegia
that is acquired at very young age can sometimes be completely
compensated over time.
According to current understanding, the contralateral organization is due to an axial twist (explained below). A number of other explanations have been published, the most popular of which is the visual map theory (explained below). A short review of existing hypotheses is given by reference. A popular-science video explains these theories in brief.
The Visual Map Theory and the Axial Twist Theory have been formulated in detail and can be regarded as scientific theories, and are explained in detail below.
Other hypotheses tend to explain specific aspects of the
phenomenon. One proposes that crossing generally provides better
geometrical mapping. According to another view, the crossing is a coincidence that has been conserved by parcellation. A third hypothesis proposes that the crossing results directly from optical inversion on the retina of the eye.
An old notion, first worked out by Jacques Loeb, is that the contralateral organisation might have an advantage for motor control,
but simulations by Valentino Braitenberg have shown that both ipsi- and contralateral connections are of major importance for control.
Further studies have asked if there is a topological
or functional advantage of the decussations.
Visual map theory by Cajal
Cajal's
schema of the visual map theory. O=Optic chiasm; C=Visual (and motor)
cortex; M, S=Decussating pathways; R, G: Sensory nerves, motor ganglia.
Social and behavior change communication
From Wikipedia, the free encyclopedia
SBCC by health practitionerSBCC on the Development-Entertainment spectrum.
Social and behavior change communication (SBCC), often also only "BCC" or "Communication for Development (C4D)" is an interactive process of any intervention with individuals, group or community (as integrated with an overall program) to develop communication
strategies to promote positive behaviors which are appropriate to their
settings and thereby solving the world's most pressing health problems.
This in turn provides a supportive environment which will enable people
to initiate, sustain and maintain positive and desirable behavior outcomes.[1]
SBCC is the strategic use of communication to promote positive health outcomes, based on proven theories and models of behavior change.
SBCC employs a systematic process beginning with formative research and
behavior analysis, followed by communication planning, implementation,
and monitoring and evaluation. Audiences are carefully segmented,
messages and materials are pre-tested, and mass media (which include
radio, television, billboards, print material, internet), interpersonal
channels (such as client-provider interaction, group presentations) and
community mobilisation are used to achieve defined behavioral
objectives.[2]
Providing
people with information and teaching them how they should behave does
not lead to desirable change in their response/behavior. However, when
there is a supportive environment with information and communication
(teaching) then there is a desirable change in the behavior of the
target group. Thus, SBCC is proved to be an instructional intervention
which has a close interface with education and communication. It is a
strategic and group oriented form of communication to perceive a desired
change in behavior of target group.[3]
However, it is not as easy as it sounds, as there is no
one-size-fits all strategy for any intervention. Interventions are
context specific. Therefore, there is a need for proper information
management and sharing. It is advised to document and report the
interventions that worked somewhere, for example, the kind of messages,
the medium and the audience.[4]
Steps
SBCC is the comprehensive process in which one passes through the stages:
Define SBCC strategy & monitoring and evaluation plan
Develop communication products
Pretest
Implement and monitor
Evaluate
Analyze feedback and revise
Enabling factors
Behavior
change is influenced by motivation from others (external influence) as
well as from within oneself (internal influence). Internal influence
plays a significant role in creating more enjoyment of a behavior
change, instilling a sense of ownership of the new behavior, which in
turn instills a sense of ownership of the changed behavior.[6]
When designing SBCC strategies, enabling factors that affect the
outcome must be considered. The following are some of the factors:[5]
Effective communication
Enabling environment, which include policies, human rights community values and norms
User-friendly, accessible services and commodities
Theories
SBCC
has several levels at which it can be implemented. Each level includes
several theories. Each level (and each theory) employs specific
communication channels.
The SBCC Summit 2018 in Bali, Indonesia, focusing on social and behavior change communication and featuring Entertainment-Education.Over
1,200 attendees came to the 2018 SBCC Summit, where
Entertainment-Education was a main topic among Social and Behavior
Chance Communications professionals.
Strategies
SBCC
is different from the ordinary instructional method of communication
and is target specific. A society consists of many sub-groups. The
strategy for SBCC will vary from group to group. The following points
are important while considering the SBCC strategy.[7]
Vulnerability/risk factor of the target group
The vulnerability/risk factor of the group which is to be addressed
The conflict and obstacles in the way to desired change in behavior
Type of message and communication media which can best be used to reach the target group
Type of resources available and assessment of existing knowledge of
the target group about the issue which is going to be dealt with
There can be several more points in this list. A successful SBCC
requires much research and meticulous planning about the knowledge
content of the subject and behavior/attitude pattern of the target
group.
Implications
SBCC
has proven effective in several health areas, such as increasing the
use of family planning methods, reducing the spread of malaria and other
infectious diseases, and improving newborn and maternal health.
SBCC is an effective tool for dealing with many community and
group related problems. BCC has been adapted as an effective strategy
for community mobilization, health and environmental education and various public outreach programs.
Enhanced knowledge about the behavior change process has facilitated the
design of communications programs to reduce the risk of HIV
transmission and AIDS. A wide variety of health promotion strategies use
communication as either an educational or norm-forming strategy. In
addition, specific strategies must be designed for high-risk groups such
as women, young people, injecting drug abusers, homosexuals and HIV
positive groups.
Role in HIV/AIDS
SBCC
consists of effective communication which is central to the success of
interventions to reduce the risk of HIV infection. It plays a role to:
Increase knowledge
Stimulate community dialogue
Promote essential attitude change
Advocate for policy changes
Create a demand for information and services
Reduce stigma and discrimination
Promote services for prevention and care
The visual map theory was published by the famous neuroscientist and pioneer Santiago Ramón y Cajal (1898). According to this theory, the function of the
optic chiasm is to repair the retinal field image on the visual cortex.
The pupil in the vertebrates’ eyes inverts the image on the retina, so
that the visual periphery projects to the medial side of the retina. By
the chiasmatic crossing, the visual periphery is again on the outside,
if one assumes that the retinal map is faithfully maintained throughout
the optic tract.
The theory has a number of weaknesses. For example, the visual tracts spiral their way from the thalamic LGN to the visual cortex. (See figure; this path is known as the optic radiation.)
As a result, the retinal map shows the visual periphery on the medial
side. However, the central objective of the theory was to obtain a
precise, faithful visual map with the medial field projecting to the
medial sides of the visual cortex.
Two twist hypotheses have been proposed independently: the axial twist by de Marc Lussanet and Jan Osse and the somatic twist by Marcel Kinsbourne. Both of them propose that the rostral
part of the head, including the forebrain, is in fact effectively
completely turned around. As a consequence, the left and right in the
brain are reversed, but also
Social and behavior change communication
From Wikipedia, the free encyclopedia
SBCC by health practitionerSBCC on the Development-Entertainment spectrum.
Social and behavior change communication (SBCC), often also only "BCC" or "Communication for Development (C4D)" is an interactive process of any intervention with individuals, group or community (as integrated with an overall program) to develop communication
strategies to promote positive behaviors which are appropriate to their
settings and thereby solving the world's most pressing health problems.
This in turn provides a supportive environment which will enable people
to initiate, sustain and maintain positive and desirable behavior outcomes.[1]
SBCC is the strategic use of communication to promote positive health outcomes, based on proven theories and models of behavior change.
SBCC employs a systematic process beginning with formative research and
behavior analysis, followed by communication planning, implementation,
and monitoring and evaluation. Audiences are carefully segmented,
messages and materials are pre-tested, and mass media (which include
radio, television, billboards, print material, internet), interpersonal
channels (such as client-provider interaction, group presentations) and
community mobilisation are used to achieve defined behavioral
objectives.
Providing
people with information and teaching them how they should behave does
not lead to desirable change in their response/behavior. However, when
there is a supportive environment with information and communication
(teaching) then there is a desirable change in the behavior of the
target group. Thus, SBCC is proved to be an instructional intervention
which has a close interface with education and communication. It is a
strategic and group oriented form of communication to perceive a desired
change in behavior of target group.
However, it is not as easy as it sounds, as there is no
one-size-fits all strategy for any intervention. Interventions are
context specific. Therefore, there is a need for proper information
management and sharing. It is advised to document and report the
interventions that worked somewhere, for example, the kind of messages,
the medium and the audience.
Steps
SBCC is the comprehensive process in which one passes through the stages:
Define SBCC strategy & monitoring and evaluation plan
Develop communication products
Pretest
Implement and monitor
Evaluate
Analyze feedback and revise
Enabling factors
Behavior
change is influenced by motivation from others (external influence) as
well as from within oneself (internal influence). Internal influence
plays a significant role in creating more enjoyment of a behavior
change, instilling a sense of ownership of the new behavior, which in
turn instills a sense of ownership of the changed behavior.
When designing SBCC strategies, enabling factors that affect the
outcome must be considered. The following are some of the factors:
Effective communication
Enabling environment, which include policies, human rights community values and norms
User-friendly, accessible services and commodities
Theories
SBCC
has several levels at which it can be implemented. Each level includes
several theories. Each level (and each theory) employs specific
communication channels.
The SBCC Summit 2018 in Bali, Indonesia, focusing on social and behavior change communication and featuring Entertainment-Education.Over
1,200 attendees came to the 2018 SBCC Summit, where
Entertainment-Education was a main topic among Social and Behavior
Chance Communications professionals.
Strategies
SBCC
is different from the ordinary instructional method of communication
and is target specific. A society consists of many sub-groups. The
strategy for SBCC will vary from group to group. The following points
are important while considering the SBCC strategy.
Vulnerability/risk factor of the target group
The vulnerability/risk factor of the group which is to be addressed
The conflict and obstacles in the way to desired change in behavior
Type of message and communication media which can best be used to reach the target group
Type of resources available and assessment of existing knowledge of
the target group about the issue which is going to be dealt with
There can be several more points in this list. A successful SBCC
requires much research and meticulous planning about the knowledge
content of the subject and behavior/attitude pattern of the target
group.[1]
SBCC
has proven effective in several health areas, such as increasing the
use of family planning methods, reducing the spread of malaria and other
infectious diseases, and improving newborn and maternal health.
SBCC is an effective tool for dealing with many community and
group related problems. BCC has been adapted as an effective strategy
for community mobilization, health and environmental education and various public outreach programs.
Enhanced knowledge about the behavior change process has facilitated the
design of communications programs to reduce the risk of HIV
transmission and AIDS. A wide variety of health promotion strategies use
communication as either an educational or norm-forming strategy. In
addition, specific strategies must be designed for high-risk groups such
as women, young people, injecting drug abusers, homosexuals and HIV
positive groups.
Role in HIV/AIDS
SBCC
consists of effective communication which is central to the success of
interventions to reduce the risk of HIV infection. It plays a role to:
Increase knowledge
Stimulate community dialogue
Promote essential attitude change
Advocate for policy changes
Create a demand for information and services
Reduce stigma and discrimination
Promote services for prevention and care
Whereas the somatic twist hypothesis focuses purely on the morphological
phenomenon of the inversions of the forebrain, the axial twist theory
also addresses the development and the evolution. Also, the axial twist
theory is at present the only theory that has produced predictions that have been tested independently.
Axial twist theory
lSchema
of the developmental twist, according to the axial twist hypothesis. A,
B: The early embryo turns onto its left side; B, C: Symmetry is
retained by a further left turn in the anterior head region and a
compensating right turn in the rest of the body. D, E: Growth of the
optic tract leading to the optic chiasm. Colors refer to early embryo:
Red=right side, blue=left side, black=dorsal, white=ventral.
The axial twist theory was designed to explain how the pattern of contralateral organization, decussations and chiasms develops, and why this pattern is so evolutionarily stable,
having no known exceptions throughout the 500 million years of
vertebrate evolution. According to the theory, the contralateral
organization develops as follows: The early embryo is turned onto its
left side, such that its left is turned to the yolk and its right is
turned away from the yolk. This asymmetric orientation is compensated by
asymmetric growth, to regain superficial bilateral symmetry. The
anterior head region turns to the left, as shown in the schema. The
forebrain is not a superficial structure, but it is so intimately
associated with superficial body structures that it turns along with the
anterior head. These structures will later form the eyes, nostrils and
mouth.
The body behind the head compensates the asymmetric body
orientation in the opposite direction, by turning to the right. (See
schema.) Due to these oppositely directed compensations of the anterior
head and the rest of the body, the animal becomes twisted.
The optic tract grows from the retina to the optic tectum.
Because dorsal and ventral are inverted in the anterior head region, the
tracts grow at first toward the ventral side, to meet in the midline to
form a chiasma. Since the optic tectum lies on the dorsal midbrain,
each tract then continues dorsally to the contralateral optic tectum.
The heart and bowels are internal organs with no strong
integration in external body structures, so there is no evolutionary
pressure to make them turn in a similar way. Rather, these organs retain
their original asymmetric orientation in the body.
The axial twist hypothesis predicts that small asymmetries of the
face and brain—as well as those found in the opposite direction in the
trunk—remain into adulthood, and this has been confirmed scientifically.
Comparing inversion, somatic twist and axial twist
According to the dorsoventral inversion hypothesis, an ancestral deuterostome turned on its back. As a result, vertebrates have a dorsal nervous system, whereas protostomes
have a ventral one. According to the somatic twist hypothesis, not the
entire animal turned on its back but just the somatic part—i.e.,
everything behind the eyes, mouth and nostrils, including the forebrain.
The somatic twist hypothesis was proposed as an improvement to
the inversion hypothesis, and thus has a much wider explanatory power
than its predecessor, but is also more complicated. It not only explains
the inversion of the body but additionally the contralateral forebrain.
It does not explain, however, how the twist might develop in the
vertebrate embryo, nor does it address the possible evolution.
The axial twist theory was defined independently of the
other two. In addition to providing rationale for the inverted body and
the contralateral forebrain, it explains why the heart and bowels are
asymmetric. Moreover, it is the only one of the three theories that is
supported by evidence from embryological growth, and it is the only
theory that has been tested independently.
Evolution
A remarkable property of the contralateral organization is that it is present in every vertebrate. Even the most distant clades—agnathans—possess an optic chiasm, and even the skull impressions of early vertebrates from the Ordovician show the presence of an optic chiasm: this idea was worked out by Kinsbourne.
There is molecular evidence for the inversion hypothesis in almost all groups of deuterostomes.
It is not known, however, what exactly was the selective pressure that
caused the inversion. Twisting and asymmetric development are well known
from other deuterostomes—such as Hemichordata, Echinodermata, Cephalochordata and Tunicata. Turning toward the side or upside-down also occurs frequently in these clades (e.g. sea stars which turn their mouth downwards after the larva has briefly settled with the mouth turned up, or the adult lancelet which buries obliquely with its mouth turned up, or many fish which tend to turn around when feeding from the water surface).
Developmental malformations
In holoprosencephaly,
the hemispheres of the cerebrum or part of it are not aligned on the
left and right side but only on the frontal and occipital sides of the
skull, and the head usually remains very small. According to the axial
twist hypothesis, this represents an extreme case of Yakovlevian torque, and
may occur when the cerebrum does not turn during early embryology.
Cephalopagus or janiceps twins are conjoined twins
who are born with two faces, one on either side of the head. These
twins have two brains and two spinal cords, but these are located on the
left and the right side of the body.
According to the axial twist hypothesis, the two nervous systems could
not turn due to the complex configuration of the body and therefore
remained on either side.
l
