The effects of age on eyeblink conditioning in the freely moving Fischer-344 rat.

The effects of age were assessed on the ability of male Fischer-344 rats to acquire a classically conditioned eyeblink using the "delay" paradigm. Using a 350 ms white noise conditioning stimulus and a 100 ms coterminating periorbital shock (2 mA, 60 Hz, AC) we have demonstrated that these rats exhibit deficits as early as middle age. Middle-aged and senescent rats (18 and 30 months) exhibited significantly fewer conditioned responses than young rats (3 and 12 months). Since all of the rats responded to a test noise, and there were no differences in threshold to evoke a blink, this result is likely to be due to an associative deficit. Thus, our results indicate that eyeblink conditioning in the freely moving rat is a useful model system for behavioral and neurobiological analyses of the effects of age on associative learning and memory.