"Impoverished" and "enriched" living conditions influence the proliferation and survival of neurons in crayfish brain

New neurons are added to two bilateral clusters of neurons in crayfish brai n throughout their lives. These interneurons are associated with the olfact ory and accessory lobes, areas of the brain that receive primary olfactory information and higher order Inputs from the visual and tactile receptor sy stems. The rate of cell proliferation in these four clusters, revealed by B rdU labeling, is sensitive to the living conditions of the animals: individ uals isolated in small spaces (impoverished condition) exhibit a lower rate of cell proliferation in comparison to their siblings living together in l arger areas (enriched condition), although both groups were fed to satiatio n. Reduction in the rate of proliferation can he measured 1 to 2 weeks afte r the animals are subjected to the impoverished condition. Counts of the la beled neurons that survive after 1 weeks of subjection to the two condition s show that fewer new neurons survive in the brains of animals that have li ved for 2 weeks in the impoverished condition in comparison to their siblin gs living in the enriched conditions. Factors such as surface area, depth o f water, and social interaction can all play a role in determining both the rate of new neuron production and the incorporation of the new neurons int o the brain of freshwater crayfish, The results indicate a high degree of n euronal plasticity in the crayfish brain that is highly sensitive to the co nditions under which the animals are kept. (C) 2000 John Wiley & Sons. Inc.