Write a short note on neuroplasticity?

WRITE A SHORT NOTE ON NEUROPLASTICITY ?

A 10 DEFINITION

1 It is the brain’s ability to reorganize itself by forming new neural connections throughout life.

2 It allows the neurons (nerve cells) in the brain to compensate for injury and disease and to adjust their activities in response to new situations or to changes in their environment.

3 Developmental plasticity occurs when neurons in the young brain rapidly sprout branches and form synapses.

4 Then, as the brain begins to process sensory information, some of these synapses strengthen and others weaken.

5 Eventually, some unused synapses are eliminated completely, a process known as synaptic pruning,

TYPES

A ) homologous area adaptation -

1 occurs during the early critical period of development.

2 If a particular brain module becomes damaged in early life, its normal operations have the ability to shift to brain areas that do not include the affected module.

3 The function is often shifted to a module in the matching, or homologous, area of the opposite brain hemisphere.

4 The downside to this form of neuroplasticity is that it may come at costs to functions that are normally stored in the module but now have to make room for the new functions.

5 An example of this is when the right parietal lobe (the parietal lobe forms the middle region of the cerebral hemispheres) becomes damaged early in life and the left parietal lobe takes over visuospatial functions at the cost of impaired arithmetical functions, which the left parietal lobe usually carries out exclusively.

6 Timing is also a factor in this process, since a child learns how to navigate physical space before he or she learns arithmetic.

B ) compensatory masquerade -

1 can simply be described as the brain figuring out an alternative strategy for carrying out a task when the initial strategy cannot be followed due to impairment.

2 One example is when a person attempts to navigate from one location to another. Most people, to a greater or lesser extent, have an intuitive sense of direction and distance that they employ for navigation. However, a person who suffers some form of brain trauma and impaired spatial sense will resort to another strategy for spatial navigation, such as memorizing landmarks. The only change that occurs in the brain is a reorganization of preexisting neuronal networks.

C ) cross-modal reassignment -

1 entails the introduction of new inputs into a brain area deprived of its main inputs.

2 A classic example of this is the ability of an adult who has been blind since birth to have touch, or somatosensory, input redirected to the visual cortex in the occipital lobe (region of the cerebrum located at the back of the head) of the brain—specifically, in an area known as V1.

3 Sighted people, however, do not display any V1 activity when presented with similar touch-oriented experiments.

A ) This occurs because neurons communicate with one another in the same abstract “language” of electrochemical impulses regardless of sensory modality.

B ) Moreover, all the sensory cortices of the brain—visual, auditory, olfactory (smell), gustatory (taste), and somatosensory—have a similar six-layer processing structure.

C ) Because of this, the visual cortices of blind people can still carry out the cognitive functions of creating representations of the physical world but base these representations on input from another sense—namely, touch.

D ) This is not, however, simply an instance of one area of the brain compensating for a lack ofvision. It is a change in the actual functional assignment of a local brain region.

D ) map expansion -

1 entails the flexibility of local brain regions that are dedicated to performing one type of function or storing a particular form of information.

A ) The arrangement of these local regions in the cerebral cortex is referred to as a “map.”

B ) When one function is carried out frequently enough through repeated behaviour or stimulus, the region of the cortical map dedicated to this function grows and shrinks as an individual “exercises” this function.

1 This phenomenon usually takes place during the learning and practicing of a skill such as playing a musical instrument.

2 Specifically, the region grows as the individual gainsimplicit familiarity with the skill and then shrinks to baseline once the learning becomes explicit.

Vv imp (Implicit learning is the passive acquisition of knowledge through exposure to information, whereas explicit learning is the active acquisition of knowledge gained by consciously seeking out information.) But as one continues to develop the skill over repeated practice, the region retains the initial enlargement.

2 Map expansion neuroplasticity has also been observed in association with pain in the phenomenon of phantom limb syndrome.

A ) The relationship between cortical reorganization and phantom limb pain was discovered in the 1990s in arm amputees.

B ) Later studies indicated that in amputees who experience phantom limb pain, the mouth brain map shifts to take over the adjacent area of the arm and hand brain maps.

C ) In some patients, the cortical changes could be reversed with peripheralanesthesia.

MECHANISM

Brain reorganization takes place by mechanisms such as -

1 “axonal sprouting” in which undamaged axons grow new nerve endings to reconnect neurons whose links were injured or severed.

A ) Undamaged axons can also sprout nerve endings and connect with other undamaged nerve cells, forming new neural pathways to accomplish a needed function.

B ) For example, if one hemisphere of the brain is damaged, the intact hemisphere may take over some of its functions. The brain compensates for damage in effect by reorganizing and forming new connections between intact neurons. In order to reconnect, the neurons need to be stimulated through activity.

2 Thru cortical remapping

3 thru activity dependent by the help of behaviour , environmental stimuli , thought and emotion

DISADVANTAGES

1 Neuroplasticity sometimes may also contribute to impairment.

For example, people who are deaf may suffer from a continual ringing in their ears (tinnitus), the result of the rewiring of brain cells starved for sound. For neurons to form beneficial connections, they must be correctly stimulated.

2 Contribution to phantom limb pain