Frequency analysis of EEG during milk drinking

Abstract

1. 1. When cats were presented a small amount of milk in a plastic feeder cup, their tongue movements made during lapping were recorded concomitantly with EEG records from posterior lateral gyri, suprasylvian gyri, and mid-ectosylvian gyri. Frequency analysis of the records revealed that a 7.5 c/sec activity was present only in the posterior lateral gyri during the lapping (7.5 was one of the center frequencies of the total ten 5-cycle bands of frequencies analyzed). The 7.5 c/sec activity was of relatively large amplitude and occurred only with repetitive lapping. Its initiation was approximately 300 msec or longer after the onset of lapping. 2. 2. The synchronous oscillatory EEG activity did not occur with ingestion of solid cat food by the animals. Therefore, the fact that the slow wave EEG occured due to the reinforcing properties of the milk hardly seems tenable. Solid cat food should be as reinforcing as milk. 3. 3. The 7.5 c/sec synchronous rhythm occurred in both normal and split-brain animals. With visual occlusion of the split-brain cat with an opaque contact lens over one eye, and recording from the ipsilateral striate cortex, there was no reliable difference in the EEG record when compared with a record from the same animal and electrode without visual occlusion. Therefore, the 7.5 c/sec synchrony in striate cortex associated with lapping was definitely not visually mediated. 4. 4. It is proposed that the synchronous slow wave EEG is initiated by a massive inhibition of cells in the striate cortex effected by the non-visual inputs associated with lapping. Microelectrode data showing inhibition in single cells correlated with movement and non-visual stimuli are cited as ancillary evidence for such an interpretation.