Cortical polarization and experimentally produced delta waves in the cat

Abstract

1. 1. Localized and diffuse delta activity induced, respectively, by acute lesions in the medial geniculate body (22 cats) and in the posterior hypothalamus (29 cats) were investigated using the midpontine pretrigeminal preparation. 2. 2. Both localized and diffuse delta waves were enhanced by application of surface negative polarizing current, and reduced by surface positive polarizing current. From these findings and those derived from the literature it was inferred that delta waves are chiefly surface positive potentials. 3. 3. The study of laminar distribution of delta waves within the cortex revealed two different potential distributions. The localized delta waves were larger at superficial than at deeper layers. The phase reversal occurred at about 1400 μ or less below the cortical surface. The diffuse delta waves were smaller at superficial than at deep layers. The phase reversed at 500 μ below the surface. This potential distribution of diffuse delta waves was closely correlated with that of the surface positive component of the primary response evoked by stimulation of the thalamic relay nucleus. 4. 4. Interaction between delta waves induced by posterior hypothalamic lesion and the surface positive component of the primary response showed that the amplitude of the positive component of the primary response was enhanced in the falling phase of a delta wave. 5. 5. Possible structures and synaptic events which might subserve the production of these delta waves were discussed.