Morphological correlates of persistent potentiation in the chick brain slice

: In an in-vitro slice preparation of the chick brain it is possible to induce persistent potentiation of responses to single electrical stimuli by giving two bursts of 300 stimuli at 5 Hz separated by ten minutes of control stimulation at 0.1 Hz. We investigated the morphological correlates of this potentiation in a group of 2 day old chicks using quantitative electron microscopical techniques. It was found that in slices which showed a clearly potentiated response there was a significant increase in the size of the postsynaptic densities of synapses on spines in the left hyperstriatum ventrale (IMHV). No such increases were seen in a control group nor in slices which failed to potentiate. These results provide further evidence for the lability of synapses in the IMHV.