LATERALIZED THALAMIC-STIMULATION - EFFECTS ON VERBAL MEMORY

This study was concerned with the effects of left- or right-thalamic s timulation on a simple verbal memory task, involving immediate free re call of lists of common words presented dichotically. The subjects wer e patients with Parkinson's disease undergoing stereotaxic thalamotomy . As a clinical routine, the patients also underwent a brief period of thalamic electrical stimulations before the lesion was made. The memo ry tests were performed during the stimulation phase of the operation and were accomplished inside the operating room. The main finding was a general deterioration of performance during thalamic stimulation com pared with preoperative and postoperative testing. However, this gener al effect was modulated by stimulation intensity and side of stimulati on. High-intensity stimulation of the left thalamus resulted in signif icantly fewer words being recalled compared with right thalamus stimul ation and low-intensity stimulation. Finally, words presented in the f irst list were recalled better than words from the second and third li sts, particularly during stimulation and at follow-up. The findings ar e discussed in relation to the thalamic activating-gating model origin ally proposed by Ojemann.