Tactile Shape Discrimination Recruits Human Lateral Occipital Complex During Early Perceptual Processing

Neuroimaging studies investigating somatosensory-based object recognition in humans have revealed activity in the lateral occipital complex, a cluster of regions primarily associated with visual object recognition. To date, determining whether this activity occurs during or subsequent to recognition per se, has been difficult to assess due to the low temporal resolution of the hemodynamic response. To more finely measure the timing of somatosensory object recognition processes we employed high density EEG using a modified version of a paradigm previously applied to neuroimaging experiments. Simple geometric shapes were presented to the right index finger of 10 participants while the ongoing EEG was measured time locked to the stimulus. In the condition of primary interest participants discriminated the shape of the stimulus. In the alternate condition they judged stimulus duration. Using traditional event-related potential analysis techniques we found significantly greater amplitudes in the evoked potentials of the shape discrimination condition between 140 and 160 ms, a timeframe in which LOC mediated perceptual processes are believed to occur during visual object recognition. Scalp voltage topography and source analysis procedures indicated the lateral occipital complex as the likely source behind this effect. This finding supports a multisensory role for the lateral occipital complex during object recognition.