The effect of stimuli deprivation on neuroplasticity

By Katie and Laura

Terms Used• Neuroplasticity is the capacity of the nervous system, in particular the

brain, to modify its organization. This can occur during normal development and maturation, and also after damage to the nervous system

• Sensory deprivation is the deliberate reduction or removal of stimuli from one of more of the senses

• A stroke is the interruption of the blood supply to any part of the brain. It usually induces some sort of paralysis or aphasia which results in sensory deprivation.

• The primary motor cortex (M1) is a region in the posterior portion of a human’s frontal lobe. It is in control of planning and executing movements.

• The ventral motor cortex (PMV) is front portion of the primary motor cortex.

• Intracortical microstimulation (ICM) is a technique that stimulates a small group of neurons just outside organs by passing a small electrical current through a nearby electrode

• Researcher: Frost et al. 2003• Subject: 5 adult squirrel monkeys• Aim: To determine if neuroplasticity occurs in the secondary cortical area (ventral

premotor cortex ,PMV) or primary cortical area (primary motor cortex M1) after a stroke is induced in the primary cortical area.

• Protocol: Firstly intracortical microstimulation (ICM) (a form of microelectrode stimulation)was used to map the PMV and M1 areas. After determining each squirrels dominant hand, a stoke was induced in the M1 region contra parallel to the to the dominant hand. This would cause each squirrel to lose function when the stroke was induced. Three months later the M1 and PMV regions were remapped for structural and blood flow differences.

• Findings: The PMV grew significantly, between .3-1.9 mm after the stroke, with no change to the M1 region. The M1 region effectively lost all blood flow, and blood flow to PMV was dramatically increased.

• Conclusion: That the degree of neuroplasticity in secondary cortical areas (PMV) is directly proportional to the damage done to the primary cortical area (M1). The second cortical area as an adaption area for new motor activities after stroke recovery.

The extent of neuroplasticity after a stroke

LIMITATIONS • Cannot use humans as it would be extremely unethical to cause stokes on humans • Technically using the monkeys cannot be generalised to humans until certain

behaviours are similarly demonstrated. • Only 5 adult squirrel monkeys were used.• As the sample size is small, generalizations on this experiment cannot be made.

STRENGTHS • Brain dominance was determined before the start of the experiment as

a control/ base line of the monkey’s original brain functions, therefore ruling out inaccurate data.

• Two areas of the brain are being compared after a time of 3 months, which shows the certain regions of the brain adaptable to change after a stroke and regions not adaptable and able to undergo neuroplasticity.

ETHICS • Causing strokes in monkeys is detrimental to their health• monkeys cannot give permission for participation• Will not receive any type of compensation for becoming permanently

damaged and possibly sacrificed.

Strengths and weaknesses of this study

• Researcher: Büchel et al. 1998• Subjects: Six subjects blinded pre-puberty (EC) and three subjects blinded

post-puberty (BC)• Aim: To determine if brain plasticity occurs in the visual cortex of BC and EC

subjects• Protocol: A pet scan recorded the subjects reading (brail) or listening to

words and responding to specific targets. Targets were words that had a raised dot during the Braille task (tactile stimuli,) and words that a high pitch tone in the auditory task (auditory stimuli.)

• Findings: EC subjects showed no significant primary visual cortex activation, where as LC subjects showed significant primary visual cortex activation.

• Conclusion: Subjects blinded post puberty were able to imagine the stimuli in a quasi-visual way, and neurons were able to form new connections in the visual cortex (neuroplasticity.) However subjects blinded pre puberty never or insufficiently activated their visual cortex no new connections were able to be formed in the visual cortex (no neuroplasticity.)

The extent of neuroplasticity after blinding

Strengths and weaknesses of this studyLIMITATIONS • There are only 9 subjects• There are double (6) the pre-puberty blinded subjects than the post puberty (3) blind

subjects• This experiment is not able to be generalized

STRENGTH S• Shows how more exposure to stimuli before becoming blind helps

increase neuroplasticity as the visual cortex has had more time to be stimulated -therefore helping the post puberty group to imagine any stimuli in a ‘semi-visual’ way and build new pathways throughout their brains.

• The same types of testing were used for each set of the blind subjects therefore the results are more accurate as the variables of testing remaining the same.

ETHICS • Using blind children in an experiment, could cause them physiological or

psychological trauma from the copious testing and pet scans.• Their parents may give consent to perform the trails even if they children

don’t want to be apart of it.

How to organize this essay• Paragraph 1- Introduction• It is thought that the environment can influence behaviour on cognitive, socio-cultural,

and biological levels. It is therefore implied that the environment can change physiological processes. This is shown when sensory deprivation influences neuroplasticity.

• Paragraph 2- Neuroplasticity• Paragraph 3- Stimuli deprivation including stroke and blindness• Paragraph 4- Neuroplasticity after stroke

• In 2003 Frost and al. aimed to _[aim]_. To do this, they used 5 adult squirrel monkeys. They _[protocol]_. They found that _[findings]_. They concluded that _[conclusion]_. However this may not be valid as _[strengths and weaknesses]_. This has been proven by further studies.

• Paragraph 5- Neuroplasticity after blindness• In 1998 Büchel et al. aimed to ___[aim]___. To do this, they used

Six subjects blinded pre-puberty and three subjects blinded post-puberty. They ___[protocol]___. They found that ___[findings]___. They concluded that ___[conclusion]___. However this may not be valid as _[strenghts and weaknesses]_. This has been proven by further studies.

• Paragraph 6- Conclusion