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.

• 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 resultsLimitations:• 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 Stanford-Binet 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 PlanIntroduction: Essay Plan

Definition of sensory deprivation and neuroplasticitySensory deprivation: is a deliberate reduction or removal of stimuli from one or more of the sensesNeuroplasticity: 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.