An intracellular analysis of EEG arousal in cat motor cortex

1. Changes in the resting potential and the effective membrane resistance were measured in 77 cells in cat precruciate cortex during the transition from cortical slow wave phase to EEG arousal. 2. These 77 neurones were classified into the recipient cells of the following five different actions on the EEG arousal: (1) postsynaptic excitation (E cells), (2) postsynaptic inhbition (I cells), (3) disinhibition (DI cells), (4) disfacilitation (DF cells) and (5) disfacilitation followed by excitation (DF-E cells). 3. The location of E cells ranged from laminae I to V, but the majority was found in lamina II. Most I cells were located in the upper half of lamina III, and a few in lamina V. DF, DI and DF-E cells existed deeply from the lower half of lamina III to laminae V-VI. 4. Slow pyramidal tract (PT) cells (n = 6) all belonged to the E cell group, whereas fast PT cells were divided into the DF (n = 10) and DF-E cell groups (n = 4). 5. It is postulated that the EEG arousal is initiated with a direct excitation of laminae I-II cells, followed by excitation and inhibition to the upper lamina III cells and further processed to laminae III-VI cells with indirect excitation, inhibition, disinhibition and disfacilitation. The model of four vertical transmission relays is proposed to depict the casade pattern of information being processed through the cortex during the EEG arousal.