Abstract
Using 36 lightly anesthetized cats we studied the characteristics of a quite brief duration evoked midbrain potential. This was recorded from a discrete region of the reticular substance caudal and ventral to centre median, lateral to the oculomotor nucleus and dorsal to the rostral nucleus ruber. It was found to have a latency approximating that of the centre median potential previously identified and studied by Magoun and McKinley (1942), though the latter has a significantly longer duration. The midbrain potential we describe has a threshold corresponding to that of the gamma axons of the superficial radial nerve and is activated through the contralateral ventrolateral sector of the cord principally. The fastest peripheral axons that activate it have a conduction rate of about 45 m/sec. as compared with 85 for the posteroventral thalamic potential. Like the centre median potential (French, Verzeano and Magoun 1953b) it is sensitive to anesthesia. It tends to potentiation by noxious stimuli applied by natural means. Other data upon centre median and posteroventral thalamic potentials obtained in the same animals is presented for comparison.
Published Version
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