Cerebral Glycoprotein Synthesis and Long-term Memory Formation in the Chick (Gallus domesticus) Following Passive Avoidance Training Depends on the Nature of the Aversive Stimulus.

Chicks that peck a small bright bead coated in a distateful substance can learn in a single trial to subsequently avoid a similar bead. The taste aversant commonly used is methyl anthranilate, which also has a strong pervasive odour. We have compared the efficacy of methyl anthranilate and the apparently odourless quinine as aversants. Methyl anthranilate-trained chicks learnt the task and the memory apparently persisted undiminished for at least 24 h. Quinine-trained chicks exhibited a memory for the task similar to that of methyl anthranilate-trained chicks 45 min after training, this thereafter declined until, at 24 h after training, they showed no recall. We investigated the incorporation of a radio-labelled synaptic membrane glycoprotein precursor, [3H]fucose, into three regions of the chick forebrain; two of these regions have previously been implicated in learning using methyl anthranilate as the aversant. There was a significant increase in [3H]fucose incorporation into the left lateral cerebral area and numerically similar, but non-significant, increases in the intermediate part of the medial hyperstriatum ventrale and lobus parolfactorius. There were no such increases in the right hemisphere of methyl anthranilate-trained chicks or any region of either hemisphere of quinine-trained chicks. Thus, the memory for methyl anthranilate is longer-lasting than that for quinine and is associated with increased fucosylation in the left cerebral hemisphere and although in the short-term, chicks can retain a memory of the one-trial passive avoidance task with quinine as the aversant, this does not result in a localized increase in cerebral [3H]fucose incorporation.