A transition from unimodal to multimodal activations in four sensory modalities in humans: An electrophysiological study

Background: To investigate the long-latency activities common to all sensory modalities, electroencephalographic responses to auditory (1000 Hz pure tone), tactile (electrical stimulation to the index finger), visual (simple figure of a star), and noxious (intra-epidermal electrical stimulation to the dorsum of the hand) stimuli were recorded from 27 scalp electrodes in 14 healthy volunteers. Results: Results of source modeling showed multimodal activations in the anterior part of the cingulate cortex (ACC) and hippocampal region (Hip). The activity in the ACC was biphasic. In all sensory modalities, the first component of ACC activity peaked 30-56 ms later than the peak of the major modality-specific activity, the second component of ACC activity peaked 117-145 ms later than the peak of the first component, and the activity in Hip peaked 43-77 ms later than the second component of ACC activity. Conclusion: The temporal sequence of activations through modality-specific and multimodal pathways was similar among all sensory modalities.