Training-induced increases in neuronal activity recorded from the forebrain of the day-old chick are time dependent

Spontaneous neuronal bursting occurs in many areas of chick forebrain. Day-old chicks trained using a one-trial task to avoid a methylanthranilate-coated bead (methyl-chicks) show a significant increase in bursting when compared to chicks trained to peck a water-coated bead (water-chicks). This increase occurs in two forebrain areas: the intermediate medial hyperstriatum ventrale and the lobus parolfactorius. Bursting was recorded from the intermediate medial hyperstriatum ventrale of anaesthetized methyland water-chicks at eight time-points over the period 1–9 h post-test. Data merged over this period showed that methyl-chicks displayed an overall increase in bursting in both left and right hemispheres when compared to water-chicks. When burst activity was compared against time, bursting in methyl-chicks was significantly elevated only during the period 3–7 h post-test. Maximal bursting in methyl-chicks was seen 6–7 h post-test. These results suggest that the training-induced increase in bursting seen in the intermediate medial hyperstriatum ventrale of methyl-chicks is not a simple, generalized increase with time but rather has a significant temporal aspect. These results may have particular relevance to previously proposed models of memory formation in the chick.