SLOW AND SPIKE COMPONENTS OF THE DIRECT CORTICAL RESPONSE IN THE CEREBRAL CORTEX

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Abstract
A potential oscillation appears superimposed on the slow potential in the olfactory epithelium of the toad, when an odorous vapour is applied. The magnitudes and in many cases the frequencies of the oscillations increased with increasing stimulus intensity or increasing stimulus velocity. The frequency decreased linearly or exponentially towards the end during a stimulation. The shapes, frequencies, durations and magnitudes of the oscillations are different not only in each toad but also at various sites on the olfactory epithelium of the same toad. The durations of the oscillations were elongated with an exponential relation to the durations of olfactory stimulation. During repetitive olfactory stimulation the magnitude, duration and frequency gradually decreased, and even the shape was changed. Eventually, the oscillation disappeared. The oscillation easily shows a fatigue-phenomenon. The potential oscillations appeared differently depending on the kinds of odours. The potential oscillation was neither produced nor affected by a single or repetitive electrical stimulation of the olfactory epithelium or nerve. By covering a part of the epithelium with a vinyl membrane, it was shown that the medial and anterior part of the eminentia was most important for the generation of the oscillation and that the oscillation was not produced by the activity of only a small olfactory area. It was always found that the potential oscillation appears when the slow potential reaches a certain magnitude. Small potential discharges were found in the epithelium by micro-electrode. They increased in number and seemingly became synchronized into a potential oscillation with increasing stimulus intensity. It was concluded that the potential oscillations of various magnitudes and shapes are produced by the interaction and summation of the potential discharges recorded by micro-electrode in the olfactory epithelium. However the potential oscillation does not play any active role in olfactory sensation.

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