EEG and the Anterior Thalamic Nucleus

This chapter summarizes the experience in recording field potentials from electrodes stereotaxically placed in AN and recording evoked responses on the scalp resulting from low frequency stimulation of anterior thalamic nuclei (AN). Deep brain stimulation microelectrodes produce reliable recruiting responses on surface EEG using bipolar stimulation. A variety of targets have been pursued, including the vagus nerve, hypothalamus, basal ganglia and the subthalamic, centro-median and AN. The AN is a component of the circuit of Papez, a group of interconnected structures in the limbic system demonstrated to have a role in cognition, memory and epilepsy. Thresholds for producing a visible recruiting rhythm were determined as a function of stimulation voltage, frequency and pulse width. A single American Board of Clinical Neurophysiology certified expert reader interpreted EEGs in the operating room for the presence of the recruiting rhythm. A larger pulse width provides more stimulation energy for a given frequency, stimulating more nuclear neurons.