Properties of spontaneous and evoked synaptic activities of thalamic ventrobasal neurons.

Publisher Website
Google Scholar
Abstract
Intracellular recordings were obtained from thalamic neurons of the ventrobasal (VB) complex Inencephaleisoleand lightly anesthetized cats. Intracellularly applied depolarizing currents produced high-frequency repetitive discharges. VB cells did not exhibit spike decomposition during these discharges providing the cells were free from significant injury effects of impalement. The vast majority of lemniscal VB neurons examined exhibited evoked EPSP''s [excitatory post synaptic potentials] which were uninfluenced by membrane hyperpolarization to levels in excess of the reversal potential for IPSP''s [inhibitory post synaptic potentials]. Small increases in EPSP amplitude during membrane hyperpolarization were observed in relatively few elements. Changes in duration of EPSP''s during membrane hyperpolarization were related to the addition of IPSP''s inverted to depolarizing potentials by hyperpolarizing currents. The least traumatized cells of the present series exhibited spontaneous rapid depolarizing potentials as well as slow depolarizing and hyperpolarizing potentials. Rapid depolarizing potentials occasionally triggered spikes below the firing level for spikes initiated by lemniscal-evoked EPSP''s or slow spontaneous EPSP''s. The rapid depolarizing potentials often had a faster time course than the lemniscal-evoked EPSP and were uninfluenced by membrane hyperpolarization.