Transcript Sensory Deprivation on Neuroplasticity

The Effect of Sensory
Deprivation on Neuroplasticity
Neuroplasticity: refers to the brain’s ability
to rearrange the connection between its
neurons – that is, the changes that occur in
the structure of the brain as a result of
learning or experience.
Sensory deprivation: a deliberate reduction
or removal of stimuli from one or more of the
senses.
Rosenzweig and
Bennett (1972)
Aim: In the belief that animals
raised in highly stimulating
environments will demonstrate
differences in the brain growth and
chemistry when compared with
animals reared in dull circumstance,
the experiment was carried out to
measure the effect of either
enrichment or deprivation to the
development of neurons in the
cerebral cortex.
Method: Male Rats were randomly assigned into 12 sets of three
(each set from the same litter) and put into one of three
circumstance to create a control group, and two experimental
groups(enriched cage, deprived cage), here they spent 4-12 weeks.
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The standard laboratory colony cage contained several rats in
an adequate space with food and water always available.
The enriched, stimulating environment was virtually a rat’s
Disneyland where 6-8 rats lived in a “large cage furnished with a
variety of objects with which they could play”
The deprived environment was a slightly smaller cage isolated
in a separate room in which the rat was placed alone with
adequate food and water.
The rats were then sacrificed and autopsies were taken out on their
brains to determine differences between the brains of the enriched
rats versus the deprived rats. The examinations were done in
random order by code number. The rat’s various brain sections
were measured, weighed, and analysed to determine amount of cell
growth and levels of neurotransmitter activity.
Findings:
• The cerebral cortex (responds to experience and is responsible
for movement, memory, learning, and all sensory input) of the
enriched rats was significantly heavier and thicker.
• There was greater activity of the nervous system enzyme
acetylcholinesterase found in the brain tissue of the enriched rats.
• Cortical thickness increases even further if the rats are placed with
other rats. The combination of having company and many
interesting toys created the best conditions for developing cerebral
thickness.
• There were no significant differences found between the two
groups of rats in the number of brain cells (neurons) but the
enriched rats produced larger neurons.
• The ratio of RNA to DNA (the two most important brain chemicals
for cell growth) was greater for the enriched rats (higher level of
chemical activity in the enriched rat’s brains).
• The synapses of the enriched rat’s brains were 50% larger than
those of the deprived rats.
Conclusion: Many aspects of brain anatomy and brain chemistry are changed by
experience. The cortex increases in weight quite readily in response to experience
whereas the rest of the brain changes little.
Strengths:
• Can be replicated easily
• Control group
• Two experimental groups
• Random order
• The duration of the experiment
• Replicated studies had supporting
results
Limitations:
• Ethics
• Rats can’t be generalised to humans
• Only male rats
• Not recent
• Sample size
For: The results which were obtained
from the Rosenzweig study, could not
be obtained by any other method. If
humans were used in this study, long
term psychological and physical harm
could have occurred. The treatment
of the rats, until they were sacrificed,
was to an acceptable standard.
Against: It could be seen as unethical
for animals to be sacrificed to obtain
a result that may not even be
applicable to humans. The rats in the
deprived cage endured unfair
treatment, lacked social contact and
lived in small cages.
The Mozart Study by Rauscher et al.
(1993)
• Aim: To find out whether listening to Mozart or complex
structured music would increase your spatial-reasoning ability.
• Method: Participants (36 college students) were given three
standard tests of spatial reasoning after experiencing free
listening conditions: a Mozart sonata, repetitive relaxation
music and silence. Participants underwent different tests after
different conditions during a 5 day period.
• Results: A temporary increase was found in spatial reasoning
ability after listening to Mozart and completing the StanfordBinet IQ test, with participants scoring 8-9 points higher after
completing the test.
• Conclusion: Effects only lasted 15 minutes
• and they only affected spatial-reasoning
• ability. It did not increase IQ in general.
• Strengths:
• The study went for 5 days
• Each participant was tested under all
three conditions
• Practice effect was eliminated by
having different tests each time
• Follow up studies years later
supported the evidence
Limitations:
• Small sample size of limited
population (26 college students)
• Effect was temporary (doesn’t
support the theory of
neuroplasticity)
• After the 2nd day the Mozart effect
stopped working
• Tested in a laboratory situation
(harder to generalize to real life
situations)
Discussion
• Other studies following Rauscher et al. 1993 were not able to
replicate the findings. Additionally, many critics say that the
generally positive findings are due to ‘enjoyment arousal’
caused by music appreciation.
• Rauscher stressed that the effect of the music was only
related to spatial reasoning skills and that the benefits only
lasted 10-15 minutes after listening. Therefore, it cannot be
concluded that this environmental factor has an effect on
neuroplasticity. However, the effect of the music has been
shown to increase activity in the right frontal and left
temporoparietal regions of the brain. While this is not
necessarily affecting neuroplasticity it still has an effect on the
psychological processes of an individual.
Essay Plan
Introduction:
Essay Plan
Definition of sensory deprivation and neuroplasticity
Sensory deprivation: is a deliberate reduction or removal of stimuli from one or more of the senses
Neuroplasticity: the brain’s ability to develop and change in response to the environment
*Link sensory deprivation (environment) to neuroplasticity (physiological process)
Main body Paragraphs
Study one: Rosenzwig and Bennett (1972)
Include: Aim
Method
Findings and conclusions
Strengths and weaknesses (i.e. rats not humans, ethics, only male rats, large sample
size)
Study two: Mozart, Rausher et al. (1993) <page 248 of textbook>
Include: Aim
Method
Results & Conclusion
Strengths & Limitations (i.e. Mozart’s theory may not be due to plasticity)
Conclusion
-Balance review on findings & review on wether sensory deprivation causes neuroplasticity & changes in
the brain, or to what degree.