Little is known about the neural correlates of tics and associated urges. In the present study, we aimed to explore the neural basis of tics in patients with Tourette syndrome by using event-related functional MRI (fMRI). Ten patients (6 women, 4 men; age: mean +/- SD = 31 +/- 11.2) were studied while spontaneously exhibiting a variety of motor and vocal tics. On the basis of synchronized video/audio recordings, fMRI activities were analysed 2 s before and at tic onset irrespective of the clinical phenomenology. We identified a brain network of paralimbic areas such as anterior cingulate and insular cortex, supplementary motor area (SMA) and parietal operculum (PO) predominantly activated before tic onset (P < 0.05, corrected for multiple comparisons). In contrast, at the beginning of tic action, significant fMRI activities were found in sensorimotor areas including superior parietal lobule bilaterally and cerebellum. The results of this study indicate that paralimbic and sensory association areas are critically implicated in tic generation, similar to movements triggered internally by unpleasant sensations, as has been shown for pain or itching.

Perceptual organization of auditory information is influenced by both the physical characteristics and the categorization of irrelevant information. This study sought to determine the degree to which schizophrenia patients could utilize acoustic properties and contextual cues (top-down factors) to segregate relevant from irrelevant material in an auditory stream. On a modification of I. Neath, A. M. Surprenant, and R. G. Crowder's (1993) auditory suffix task, both schizophrenia and control participants demonstrated better recall of relevant information when irrelevant information had different physical characteristics, compared with when both arose from the same source. In contrast, schizophrenia patients were unaffected by a contextual manipulation that allowed controls to reduce the interfering effect of an irrelevant stimulus. These data suggest that a reduced ability to utilize contextual information plays a role in the perceptual organization dysfunction in schizophrenia.

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