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Computational models have been be used to estimate the electric and magnetic fields induced by transcranial magnetic stimulation (TMS) and can provide valuable insights into the location and spatial distribution of TMS stimulation. However, there has been little translation of these findings into practical TMS research. This study uses the International 10-20 EEG electrode placement system to position a standard figure-of-eight TMS coil over 13 commonly adopted targets. Using a finite element method and an anatomically detailed and realistic head model, this study provides the first pictorial and numerical atlas of TMS-induced electric fields for a range of coil positions. The results highlight the importance of subject-specific gyral folding patterns and of local thickness of subarachnoid cerebrospinal fluid (CSF). Our modelling shows that high electric fields occur primarily on the peaks of those gyri which have only a thin layer of CSF above them. These findings have important implications for inter-individual generalizability of the TMS-induced electric field. We propose that, in order to determine with accuracy the site of stimulation for an individual subject, it is necessary to solve the electric field distribution using subject-specific anatomy obtained from a high-resolution imaging modality such as MRI.

Cerebellar functions in two types of perceptual timing were assessed: the absolute (duration-based) timing of single intervals and the relative (beat-based) timing of rhythmic sequences. Continuous transcranial magnetic theta-burst stimulation (cTBS) was applied over the medial cerebellum and performance was measured adaptively before and after stimulation. A large and significant effect was found in the TBS (n = 12) compared to the SHAM (n = 12) group for single-interval timing but not for the detection of a regular beat or a deviation from it. The data support the existence of distinct perceptual timing mechanisms and an obligatory role of the cerebellum in absolute interval timing with a functional dissociation from relative timing of interval within rhythmic sequences based on a regular beat.

These findings are consistent with previous evidence for left hemisphere and frontal disturbances in the schizophrenia group. However, the syndrome results point to more distinctive patterns of dysregulation in network integration: widespread and excessive in Disorganisation, localised and enhanced in Reality Distortion, versus localised and diminished in Psychomotor Poverty.

In three experiments, we investigated the role of the cerebellum in sub- and suprasecond time perception by using repetitive transcranial magnetic stimulation (rTMS). In Experiment 1, subjects underwent four 8-min 1-Hz rTMS sessions in a within-subject design. rTMS sites were the medial cerebellum (real and sham rTMS), left lateral cerebellum, and right lateral cerebellum. Following each rTMS session, subjects completed a subsecond temporal bisection task (stimuli in the range 400-800 msec). Compared with sham rTMS, rTMS applied over the right lateral or medial cerebellum induced a leftward shift of the psychophysical function (perceived lengthening of time). In Experiment 2, a separate sample of subjects underwent the identical rTMS procedure and completed a suprasecond bisection task (stimuli in the 1000-2000 msec range). In this experiment, rTMS to the cerebellar sites did not produce any significant changes compared with sham rTMS. Experiment 3 employed a within-subject design to replicate findings from Experiments 1 and 2. Subjects underwent four rTMS conditions (sub- and suprabisection tasks following medial cerebellar and sham rTMS). rTMS induced a significant leftward shift of psychophysical function in the subsecond bisection, but not in the suprasecond bisection. In this study, we have demonstrated that transient cerebellar stimulation can differently affect the ability to estimate time intervals below and above a duration of 1 sec. The results of this study provide direct evidence for the role of the cerebellum in processing subsecond time intervals. This study further suggests that the perception of sub- and suprasecond intervals is likely to depend upon distinct neural systems.

Disordered time perception has been reported in schizophrenia. We investigated time perception dysfunction and its neuropsychological correlates in patients with schizophrenia. Thirty-eight patients and thirty-eight age and sex matched healthy volunteers were compared in an auditory temporal bisection paradigm using two interval ranges (a 400/800ms condition and a 1000/2000ms condition). In the temporal bisection, subjects were required to categorise a probe duration as short or long, based upon the similarity with two reference durations. All subjects also completed a battery of neuropsychological tests measuring sustained attention, shortand long-term memory and executive function. In the 400/800ms condition, patients judged durations significantly shorter than did control subjects. Patients also exhibited decreased temporal sensitivity in both conditions. We found in both groups a negative association between temporal sensitivity and sustained attention for the 400/800ms condition, and between temporal sensitivity and long-term memory for the 1000/200ms condition. In patients, short-term memory performance was negatively associated with duration judgement in both conditions, while executive dysfunction was correlated to a general performance deficit in the 400/800ms condition. These findings suggest the possibility that time perception abnormalities in schizophrenia are part of neuropsychological dysfunction and are likely to adversely impact upon activity of daily living.

Our ability to interact physically with objects in the external world critically depends on temporal coupling between perception and movement (sensorimotor timing) and swift behavioral adjustment to changes in the environment (error correction). In this study, we investigated the neural correlates of the correction of subliminal and supraliminal phase shifts during a sensorimotor synchronization task. In particular, we focused on the role of the cerebellum because this structure has been shown to play a role in both motor timing and error correction. Experiment 1 used fMRI to show that the right cerebellar dentate nucleus and primary motor and sensory cortices were activated during regular timing and during the correction of subliminal errors. The correction of supraliminal phase shifts led to additional activations in the left cerebellum and right inferior parietal and frontal areas. Furthermore, a psychophysiological interaction analysis revealed that supraliminal error correction was associated with enhanced connectivity of the left cerebellum with frontal, auditory, and sensory cortices and with the right cerebellum. Experiment 2 showed that suppression of the left but not the right cerebellum with theta burst TMS significantly affected supraliminal error correction. These findings provide evidence that the left lateral cerebellum is essential for supraliminal error correction during sensorimotor synchronization.

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