The effect of visual disconnection of the cerebellum upon visual Pavlovian conditioning and the failure of interocular transfer in the rabbit.

Abstract

This thesis was concerned with examining the differential role of the ipsilateral and contralateral optic fibre systems in: (a) oculomotor control, and (b) interocular transfer in the rabbit. The first experiment was concerned to test the notion that the ipsilaterally projecting ganglion cell fibres constitute a retino-geniculo-striate system that is mainly concerned with pattern vision; and that the contralateral fibre system is both concerned with vision and oculomotor control. Transection of the contralateral optic fibre system was used to visually disconnect the cerebellum and examine the effect of this on both optokinetic nystagmus (OKN) responding and on Pavlovian conditioning of the nictitating membrane (NM) response. The results showed that both OKN and NM conditioning were lost following chiasma section. The second experiment was concerned to examine the role of oculomotor scanning strategies in interocular transfer (IOT) in the rabbit. A comparison was made of the amount of IOT found for monocular learning of a two choice visual discrimination compared with monocular learning of visual NM conditioning. The first task involves extensive oculomotor scanning and is believed to be mediated mainly by the ipsilateral optic fibre system; whereas the second entails no oculomotor scanning and depends entirely on the contralateral optic fibre system. The results showed there was a complete absence of IOT in the rabbit using either procedure.