Rosenzweig and Bennet

Rosenzweig and Bennet

1. Aim: 1972 Animals raised in highly stimulating environments will demonstrate differences in brains growth and chemistry when compared with animals reared in dull environments.

   • Carried out to measure the effects of wither enrichment or deprivation to the development of neurons in the cerebral cortex.

2. Method:

   • Male rats randomly assigned into 12 sets of 3 (each from the same litter).
   • Put into 1 of 3 circumstances to create a control group, and 2 experimental groups: enriched cage, deprived cage. Here they spent 4-12 weeks.
   • Cages:
     • The control group were placed in the standard laboratory colony cage which contained several rats in a adequate space with food and water always available.
     • The enriched environment 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 killed and autopsies were carried out on their brains to determine differences between the brains of the enriched rats vs the deprived rats.
   • The examinations were done in random order by code number.
   • The rats various brain sections were measured, weighed and analysed to determine amount of cell growth and levels of neurotransmitter activity.

3. Findings:

   • The cerebral cortext (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 was greater for the enriched rats (higher levels of chemical activity in the enriched rats brains).
   • The synapses of the enriched rats brains were 50% larger than those of the deprived rats.

4. Problems:

   • Animal cruelty.
   • Androcentric.
   • Rats cannot be generalised to humans.
   • Small sample size.