Abstract
The cerebral cortex of curarized, non-anesthetized dogs responded to a single stimulation of the thalamic somatosensory nucleus with an evoked potential consisting of a primary positive-negative diphasic complex (P-and N-waves) followed by a slow negative wave (SN-wave) of 100-150 msec in duration. The properties of the SN-wave were studied in comparison with those of the P-and the N-waves.
1, The localization of the SN-wave was limited within the somatoscnsory cortex, and its threshold was slightly lower than that of the primary complex. When the thalamic stimuli were applied at an appropriate frequency, the SN-wave responded in a waxing and waning fashion.
2. In light barbiturate anesthesia, the SN-wave became unstable more readily than did the primary complex. By high frequency stimulation of the midbrain reticular formation the P-wave was more or less suppressed, but the effects on the N-and the SN-waves were quite variable.
3. The SN-wave was more resistant to systemic asphyxia or topically applied KCl than was the N-wave. Strychnine augmented the primary complex, especially its N-wave, whereas the SN-wave was little affected. By topical treatment with GABA the N-wave was abolished and the SN-wave was extremely enhanced.
4. The intracortical recording revealed that the SN-wave originated from some deeper points of the cortex than those producing the primary complex.
