Sharply timed and lateralised events at time of establishment of long term memory

In the chick long term memory is known suddenly to become more resistant to disturbance 25 minutes after training. This was investigated using two bead pecking tasks: training involved either presentation of an ill-tasting bead (causing inhibition of spontaneous pecking) or habituation by prolonged presentation. Retention tests revealed two brief periods of improved recall, centred at 25 and at 30-32 minutes after learning. The first appeared to be associated with systems fed by the left eye and the second with right eye systems. In a final experiment memory formation in right or left hemisphere was directly disturbed by intracranial injection of the amnesic beta-antagonist sotalol. The first (and perhaps also second) period of improved recall was associated with interaction between the hemispheres. Right- and left-eyed birds differed markedly, both in the character of such interaction and in the outcome of learning.