Neural correlates of tactile orientation discrimination: An fMRI study

In the present study, using event-related functional magnetic resonance imaging (fMRI) we measured the tactile memory related brain activations with tactile orientation discrimination task. For each trial, two of three tactile grating domes with same or different orientations (0, 45 and 90° against the proximal-distal line of right index finger) were presented to the subjects' right index fingertip. Nine health young subjects were asked to discriminate whether the orientations of two tactile stimuli was the same or not. Compared to the resting period, the most prominent activation areas evoked by the orientation discrimination tasks were in the primary and secondary somatosensory areas in the bilateral parietal operculum (SI and SII), posterior parietal cortex (PPC), prefrontal cortex (PFC), supplementary motor area (SMA), lateral occipital complex (LOC), insula and cerebellum. But we found that both of the activation in intensity and size were higher during tactile orientation discrimination process compared to these of encoding process. The result suggested that the tactile orientation discrimination process may raise more brain activations since this process include the high level processing such as recall and decision making.