Single pulse electrical stimulation of the medial thalamic surface induces narrower high gamma band activities in the sensorimotor cortex.

The human thalamus projects nerve fibers to all cortical regions and propagates epileptic activity. However, opportunities to directly record thalamic and cortical neural activities simultaneously are extremely limited and their electrophysiological interactions remain largely unexplored. Therefore, in this study, we recruited six patients who underwent awake craniotomy with opened lateral ventricles. The electrodes were placed on the thalamic surface over the ventricular wall and brain surface around the central sulcus. Electrical stimulation was applied to each electrode to record the evoked responses. Furthermore, we performed time-frequency and statistical analyses to investigate the cortical responses induced by electrical stimulation. High gamma activity was elicited in the cerebral cortex following thalamic stimulation. However, regarding frequency bands, the cortical spectral response induced by thalamic stimulation (TCSR) showed power increases in more restricted bands at approximately 100 Hz compared with the cortical spectral response induced by cortical stimulation (CCSR). In contrast, more electrodes in CCSRs showed a power decrease after the power increase than those in TCSRs. Finally, compared with the cortex, thalamic projections evoked localized neural activity in the cortex. Adjusting stimulus intensity and comparison with deep thalamic electrode stimulation will further clarify thalamocortical linkages.