| dc.description | In the adult raccoon, neurons in somatosensory cortex acquire new receptive fields during denervation-induced reorganization. Furthermore, RF size changes considerably during reorganization. Infra-cortical inhibition has been shown to regulate the RFs of cortical neurons in the normal cat and primate. The central question of the present thesis was whether infra-cortical inhibition could account for differences between control neurons and neurons studied at different stages of reorganization. To examine this possibility, bicuculline methiodide (BM[), a specific antagonist of the GABAA receptor was applied to cortical neurons in 12 normal raccoons and 10 raccoons that had previously undergone amputation of the fourth forepaw digit 2 weeks to 37 weeks earlier. BMI application altered the receptive fields in 62/102 neurons in the control animals and 64/103 neurons in denervated cortex. In reorganized cortex, simple receptive field expansion that preserved the shape of the original receptive field was seen in 39 neurons. In 22 cells BMI produced more complex changes such as a transition from single digit to multi-digit fields after BMI application, a degree of expansion that was never produced in the normal animal. These data indicate that pre-existing anatomical connections cannot account for the appearance of new RFs after amputation and suggest that cortical inhibitory synapses shape or focus the RF in the normal cortex as well as during reorganization. | en_US |
