INTERACTION ON CEREBRAL CORTEX OF ACOUSTIC OR OPTIC WITH NOCICEPTIVE IMPULSES: THE PROBLEM OF CONSCIOUSNESS

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Abstract
In lightly anesthetized cats nociceptive stimuli induced by the immersion of a hind leg in water of 55-65[degree] C increase the responsiveness of the auditory and visual projection areas to acoustic and optic stimuli, respectively. This increased reactivity is thought to be due to the interaction at the cortical level of impulses originating in the hypothalamic-cortical system activated by nociception and those originating in the specific projection systems. Even subthreshold nociceptive stimuli, i.e., those which do not cause asynchrony in the electrocorticogram, are effective. The increased responsiveness of the specific projection areas is indicated by increased amplitude and/or greater tendency to multiple potentials on stimulation with a series of clicks or optic flashes and also by extension of the cortical area from which the response to a given optic or acoustic stimulus can be obtained. If strychnine is applied to the auditory projection area the interaction between nociceptive and acoustic stimulation may result in convulsive responses in synchrony with the acoustic stimuli, whereas without nociception only small auditory potentials are evoked. Moreover, this interaction leads to a spread of convulsive activity to other parts of the auditory area. It is assumed that the interaction between the hypothalamic- cortical system and a specific cortical projection area is the physiological basis of sensation and perception.