ELECTROCORTICAL AND BEHAVIORAL-RESPONSES PRODUCED BY ACUTE ELECTRICAL-STIMULATION OF THE HUMAN CENTROMEDIAN THALAMIC NUCLEUS

Incremental, desynchronizing and spike-wave electrocortical responses and concomitant symptoms to acute electrical stimulation of the centro median thalamic nucleus (CM) were studied in 12 patients with intracta ble complex partial and tonic-clonic generalized seizures. Low-frequen cy (6/s), 320-800 mu A stimulation of the caudal-basal and central por tions of CM elicited incremental recruiting and augmenting-like respon ses with a bilateral regional scalp distribution, with emphasis at the ipsilateral frontal (recruiting) and central (augmenting) regions, wh ile ventral-basal CM stimulation elicited primary-like responses with a focal distribution at the ipsilateral parietal region. High-frequenc y (60/s), 320-800 mu A stimulation of caudal-basal and central, but no t ventral-basal CM, elicited EEG desynchronization and a slow negative shift of the EEG baseline with scalp distribution similar to that sho wed by recruiting- and augmenting-like responses. Neither incremental nor desynchronization EEG responses were accompanied by evident patien t sensory or motor responses. Low-frequency (3/s), high-intensity (30 V = 2400 mu A) combined stimulation of the right CM and left non-speci fic mesencephalic ascending pathways elicited a response similar to th e typical absence attack with all EEG and clinical ingredients: S1, S2 , P1 and W components of the individual spike-wave complex and general ized spike-wave discharges followed by sleep spindle EEG afterdischarg es, accompanied by motionless stare, 3/s eye blinking, lip smacking an d total failure to respond to visual stimuli in patients under a simpl e responding task. (C) 1997 Elsevier Science Ireland Ltd.