Oculomotor studies provide a novel strategy for evaluating the functional inte grity of multiple brain systems and cognitive processes in autism. The current s tudy compared pursuit eye movements of 60 highfunctioni...Oculomotor studies provide a novel strategy for evaluating the functional inte grity of multiple brain systems and cognitive processes in autism. The current s tudy compared pursuit eye movements of 60 highfunctioning individuals with aut ism and 94 intelligence quotient, age and gender matched healthy individuals usi ng ramp and oscillating target tasks. Individuals with autism had normal pursuit latency, but reduced closedloop pursuit gain when tracking both oscillating a nd ramp targets. This closedloop deficit was similar for leftward and rightwar d pursuit, but the difference between individuals with autism and their agemat ched peers was more apparent after midadolescence, suggesting reduced maturati onal achievement of the pursuit system in autism. Individuals with autism also h ad lower openloop pursuit gain (initial 100 ms of pursuit) and less accurate i nitial catchup saccades during a foveofugal stepramp task, but these deficit s were only seen when targets moved into the right visual field. Pursuit perform ance in both openand closedloop phases was correlated with manual praxis in individuals with autism. Bilateral disturbances in the ability to use internally generated extraretinal signals for closedloop pursuit implicate frontostriata l or cerebellar circuitry. The hemifield specific deficit in openloop pursuit demonstrates a lateralized disturbance in the left extrastriate areas that extra ct visual motion information, or in the transfer of visual motion information to the sensorimotor areas that transform visual information into appropriate oculo motor commands.展开更多
Background: The role of the striatum in language remains poorly understood. I ntraoperative electrical stimulation during surgery for tumours involving the ca udate nucleus or putamen in the dominant hemisphere might ...Background: The role of the striatum in language remains poorly understood. I ntraoperative electrical stimulation during surgery for tumours involving the ca udate nucleus or putamen in the dominant hemisphere might be illuminating. Objec tives: To study the role of these structures in language, with the aim of avoidi ng postoperative definitive aphasia. Methods: 11 patients with cortico- subcort ical low grade gliomas were operated on while awake, and striatal functional map ping was done. Intraoperative direct electrical stimulation was used while the p atients carried out motor and naming tasks during the resection. Results: In fiv e cases of glioma involving the dominant putamen, stimulations induced anarthria , while in six cases of glioma involving the dominant caudate, stimulations elic ited perseveration. There was no motor effect. The striatum was systematically p reserved. Postoperatively, all patients except one had transient dysphasia which resolved within three months. Conclusions: There appear to be two separate basa l ganglia systems in language, one mediated by the putamen which might have a mo tor role, and one by the caudate which might have a role in cognitive control. T hese findings could have implications for surgical strategy in lesions involving the dominant striatum.展开更多
Functional neuroimaging in human subjects and single cell recordings in monkeys show that several extra-striate visual areas are activated by visual motion. However, the extent to which different types of motion are p...Functional neuroimaging in human subjects and single cell recordings in monkeys show that several extra-striate visual areas are activated by visual motion. However, the extent to which different types of motion are processed in different regions remains unclear, although neuropsychological studies of patients with circumscribed lesions hint at regional specialization. We, therefore, studied four patients with unilateral damage to different regions of extrastriate visual cortex on a series of visual discrimination tasks that required them, to a different extent, to integrate local motion signals in order to correctly perceive the direction of global motion. Performance was assessed psychophysically and compared with that of control subjects and with the patients’performance with stimuli presented in the visual field ipsilateral to the lesion. The results indicate considerable regional specialization in extra-striate regions for different aspects of motion processing, namely the largest displacement from frame to frame (D-max) that can sustain perception of coherent motion; perception of relative speed; the amount of coherent motion needed to sustain a percept of global motion in a particular direction; the detection of discontinuities within a moving display; the extraction of form from motion. It was also clear that a defect in local motion, i.e. D-max, can be overcome by integrating local motion signals over a longer period of time. Although no patient suffered from only one defect, the overall pattern of results strongly supports the notion of regional specialization for different aspects of motion processing.展开更多
文摘Oculomotor studies provide a novel strategy for evaluating the functional inte grity of multiple brain systems and cognitive processes in autism. The current s tudy compared pursuit eye movements of 60 highfunctioning individuals with aut ism and 94 intelligence quotient, age and gender matched healthy individuals usi ng ramp and oscillating target tasks. Individuals with autism had normal pursuit latency, but reduced closedloop pursuit gain when tracking both oscillating a nd ramp targets. This closedloop deficit was similar for leftward and rightwar d pursuit, but the difference between individuals with autism and their agemat ched peers was more apparent after midadolescence, suggesting reduced maturati onal achievement of the pursuit system in autism. Individuals with autism also h ad lower openloop pursuit gain (initial 100 ms of pursuit) and less accurate i nitial catchup saccades during a foveofugal stepramp task, but these deficit s were only seen when targets moved into the right visual field. Pursuit perform ance in both openand closedloop phases was correlated with manual praxis in individuals with autism. Bilateral disturbances in the ability to use internally generated extraretinal signals for closedloop pursuit implicate frontostriata l or cerebellar circuitry. The hemifield specific deficit in openloop pursuit demonstrates a lateralized disturbance in the left extrastriate areas that extra ct visual motion information, or in the transfer of visual motion information to the sensorimotor areas that transform visual information into appropriate oculo motor commands.
文摘Background: The role of the striatum in language remains poorly understood. I ntraoperative electrical stimulation during surgery for tumours involving the ca udate nucleus or putamen in the dominant hemisphere might be illuminating. Objec tives: To study the role of these structures in language, with the aim of avoidi ng postoperative definitive aphasia. Methods: 11 patients with cortico- subcort ical low grade gliomas were operated on while awake, and striatal functional map ping was done. Intraoperative direct electrical stimulation was used while the p atients carried out motor and naming tasks during the resection. Results: In fiv e cases of glioma involving the dominant putamen, stimulations induced anarthria , while in six cases of glioma involving the dominant caudate, stimulations elic ited perseveration. There was no motor effect. The striatum was systematically p reserved. Postoperatively, all patients except one had transient dysphasia which resolved within three months. Conclusions: There appear to be two separate basa l ganglia systems in language, one mediated by the putamen which might have a mo tor role, and one by the caudate which might have a role in cognitive control. T hese findings could have implications for surgical strategy in lesions involving the dominant striatum.
文摘Functional neuroimaging in human subjects and single cell recordings in monkeys show that several extra-striate visual areas are activated by visual motion. However, the extent to which different types of motion are processed in different regions remains unclear, although neuropsychological studies of patients with circumscribed lesions hint at regional specialization. We, therefore, studied four patients with unilateral damage to different regions of extrastriate visual cortex on a series of visual discrimination tasks that required them, to a different extent, to integrate local motion signals in order to correctly perceive the direction of global motion. Performance was assessed psychophysically and compared with that of control subjects and with the patients’performance with stimuli presented in the visual field ipsilateral to the lesion. The results indicate considerable regional specialization in extra-striate regions for different aspects of motion processing, namely the largest displacement from frame to frame (D-max) that can sustain perception of coherent motion; perception of relative speed; the amount of coherent motion needed to sustain a percept of global motion in a particular direction; the detection of discontinuities within a moving display; the extraction of form from motion. It was also clear that a defect in local motion, i.e. D-max, can be overcome by integrating local motion signals over a longer period of time. Although no patient suffered from only one defect, the overall pattern of results strongly supports the notion of regional specialization for different aspects of motion processing.
