Richard B. Ivry

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The brain localization of motor sequence learning was studied in normal subjects with positron emission tomography. Subjects performed a serial reaction time (SRT) task by responding to a series of stimuli that occurred at four different spatial positions. The stimulus locations were either determined randomly or according to a 6-element sequence that(More)
The representation of temporal information can be examined from both a neurological and a computational perspective. Recent evidence suggests that two subcortical structures, the cerebellum and basal ganglia, play a critical role in the timing of both movement and perception. At a computational level, models of an internal clock have been developed in which(More)
This study investigated the effects of different types of neurological deficits on timing functions. The performance of Parkinson, cerebellar, cortical, and peripheral neuropathy patients was compared to age-matched control subjects on two separate measures of timing functions. The first task involved the production of timed intervals in which the subjects(More)
PET revealed the effects of stimulus characteristics on the neural substrate of motor learning. Right-handed subjects performed a serial reaction time task with colour-coded stimuli to eliminate the potential for learned eye-movements. The task was performed with the right hand under two different conditions. In one condition, subjects simultaneously(More)
Positron emission tomography was used to identify neural systems involved in the acquisition and expression of sequential movements produced by different effectors. Subjects were tested on the serial reaction time task under implicit learning conditions. In the initial acquisition phase, subjects responded to the stimuli with keypresses using the four(More)
Patients with cerebellar damage are known to exhibit deficits in the temporal control of movements. We report that these deficits are restricted to discontinuous movements. Cerebellar patients exhibited no deficit in temporal variability when producing continuous, rhythmic movements. We hypothesize that the temporal properties of continuous movements are(More)
Study participants performed time perception and production tasks over a set of 4 intervals ranging from 325 to 550 ms. In 3 experiments, variability on both the production and perception tasks was found to be linearly related to the square of the target intervals. If the perception and production of short temporal intervals use a common timing mechanism,(More)
We report a series a three psychophysical experiments designed to differentiate the contributions of the neocerebellar and prefrontal cortex to time perception. Comparison of patients with focal, unilateral neocerebellar or prefrontal lesions on temporal discrimination of 400-ms and 4-s intervals (Expt. 1) indicated that neocerebellar damage impaired timing(More)
The question of whether language affects perception has been debated largely on the basis of cross-language data, without considering the functional organization of the brain. The nature of this neural organization predicts that, if language affects perception, it should do so more in the right visual field than in the left visual field, an idea unexamined(More)
Two general frameworks have been articulated to describe how the passage of time is perceived. One emphasizes that the judgment of the duration of a stimulus depends on the operation of dedicated neural mechanisms specialized for representing the temporal relationships between events. Alternatively, the representation of duration could be ubiquitous,(More)