The spatio-temporal dynamics of somatosensory shape discrimination.
Joshua Nelson Lucan
Symposium Talk
Last modified: 2008-05-13
Abstract
Functional imaging studies have revealed a number of cortical regions associated with somatosensory shape recognition in humans. These include somatosensory association cortex, as would be expected, but activity is also often found in the so-called lateral occipital complex, a cluster of regions primarily associated with visual object processing. We measured high density EEG to investigate the timing of somatosensory shape discrimination processes using a modified version of a paradigm previously employed in functional imaging experiments. Simple geometric shapes were presented to the right index finger of ten participants while the ongoing EEG was measured time locked to the stimulus. In the experimental condition participants discriminated the shape of the stimulus. In the control 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 80 and 100ms. Scalp voltage topography and source analysis procedures indicated a greater involvement of contralateral somatosensory association cortex in the shape discrimination condition. Conventional analyses failed to reveal clear stimulus locked activation of lateral occipital areas during sensory–perceptual processing timeframes. We will discuss possible methodological reasons for this apparent divergence from findings in the imaging literature, including differences in the timeframes considered, and explore several approaches toward a resolution.
