Electrocorticograms (ECoGs) were evaluated in young rats and in middle-aged (19 months) rats housed under three different environments. The standard condition (SC, N=5) indicated the condition where two rats stayed in a standard cage, enriched condition (EC, N=5) meant keeping 6-8 rats in a large cage and impoverished condition (IC, N=5) was referred to as housing a single rat in a small cage. All middle-aged rats were kept under one of these cage conditions for 12 months, starting at 7 months of age. An ECoG was recorded simultaneously from 6 different locations on the scalp and was subjected to comparisons among the SC, EC and IC by means of spectral analysis. The power of the occipital α band (8.1-10.0 Hz) was significantly increased in IC rats. Total occipital power in IC rats was also enhanced as compared to SC and EC rats. These findings demonstrate that ECoG changes are present in the neocortex of middle-aged rats in different environments. In addition, social interaction seems to have a stronger effect than the differences in living capacity. These results indicate that the aging process should be studied from the viewpoint of environmental influences.