FIG. 11.

“Inhibitory dominance” of corticothalamic feedback on thalamic relay cells. A: intracellular recording of a TC cell in the lateral posterior (LP) thalamic nucleus while stimulating the anatomically related part of the suprasylvian cortex in cats during barbiturate anesthesia. Cortical stimulation (arrow) evoked a small excitatory postsynaptic potential (EPSP) followed by a powerful biphasic inhibitory postsynaptic potential (IPSP). The IPSP gave rise to a rebound burst in the TC cell. This example was representative of the majority of recorded TC cells. B: simulation of cortical EPSPs (AMPA-mediated) in a circuit of 4 interconnected thalamic cells. Cortical EPSPs were stimulated by delivering a presynaptic burst of 4 spikes at 200 Hz to AMPA receptors. The maximal conductance was similar in TC and RE cells (100 nS in this case), and no rebound occurred after the stimulation (arrow). C: simulation of dominant IPSP in TC cell. In this example, the AMPA conductance of stimulated EPSPs in the TC cell was reduced to 5 nS. The stimulation of AMPA receptors evoked a weak EPSP followed by strong IPSP, then by a rebound burst in the TC cells, as observed experimentally. [Modified from Destexhe et al. (100).]