Perceptual experience in somatosensory temporal discrimination is indexed by a mid-latency fronto-central ERP difference

Abstract

The neural correlates of conscious somatosensory perception are usually investigated using threshold detection tasks. However, it is largely unclear how other aspects of conscious somatosensory experience, such as localization, discrimination, and identification, are processed in the brain. Here, we go beyond mere stimulus detection and analyze the EEG data of 34 participants to investigate the event-related potential correlates of somatosensory experience in a temporal discrimination task. We show that the perceptual experience of feeling one vs. two pulses for identical pairs of electrical stimuli is reflected in positive fronto-central ERP activity after ~ 150 ms, even when controlling for task-relevance and post-perceptual processes such as decision-making and response preparation. This effect is a modulation of an ERP component that peaks considerably later at 170 ms and in a different sensor region than the detection-related so-called N140, which was not modulated by our task. Distributed source reconstruction of the sensor-level effect suggested the contralateral primary somatosensory cortex as its origin. We therefore propose that conscious detection and temporal discrimination are likely to both involve early sensory areas but recruit different neuronal processes. Our result adds to the growing body of research investigating the mechanisms underlying different aspects of conscious experience.