Biomedical subjects

James M Intriligator

Publications and source records attributed to James M Intriligator.

4 recordsLinked to original sources

PubMed2003

Developmental prosopagnosia: a study of three patients.

We studied perception in three patients with prosopagnosia of childhood onset. All had trouble with other 'within-category' judgments. All were deficient on face matching tests and severely impaired on tests of perception of the spatial relations of facial features and abstract designs, indicating a deficit in the encoding of coordinate relationships, similar to adult-onset prosopagnosia with lesions of the fusiform face area. Two had difficulty perceiving feature colour, which correlated with reduced luminance sensitivity. In contrast to adult-onset patients, saturation discrimination was spared in two and spatial resolution impaired in two. Curvature discrimination was relatively spared. Contrast sensitivity showed variable reductions at different spatial frequencies. We conclude that developmental prosopagnosia is similar to the adult-onset form in encoding deficits for the spatial arrangement of facial elements. Deficits in luminance perception and spatial resolution are more associated with defective encoding for basic object-level recognition, as shown on tests of object and spatial perception.

Adult↗

PubMed2002

Blindsight modulation of motion perception.

Monkey data suggest that of all perceptual abilities, motion perception is the most likely to survive striate damage. The results of studies on motion blindsight in humans, though, are mixed. We used an indirect strategy to examine how responses to visible stimuli were modulated by blind-field stimuli. In a 26-year-old man with focal striate lesions, discrimination of visible optic flow was enhanced about 7% by blind-field flow, even though discrimination of optic flow in the blind field alone (the direct strategy) was at chance. Pursuit of an imagined target using peripheral cues showed reduced variance but not increased gain with blind-field cues. Preceding blind-field prompts shortened reaction times to visible targets by about 10 msec, but there was no attentional crowding of visible stimuli by blind-field distractors. A similar efficacy of indirect blind-field optic flow modulation was found in a second patient with residual vision after focal striate damage, but not in a third with more extensive medial occipito-temporal damage. We conclude that indirect modulatory strategies are more effective than direct forced-choice methods at revealing residual motion perception after focal striate lesions.

Adult↗

PubMed2002

Antisaccades and task-switching: interactions in controlled processing.

Smaller latency costs for switching from dominant (habitual) to non-dominant (unusual) tasks compared to the reverse direction have been noted in some studies of task-switching. This asymmetry has been cited as evidence of inhibitory effects from the prior trial. We examined accuracy and latency costs of task-switching between prosaccades and antisaccades, where task-switching is limited to stimulus-response re-mapping and occurs between tasks highly asymmetric in dominance. Eighteen subjects executed prosaccades and antisaccades in single-task and mixed-task blocks. In mixed-task blocks, antisaccade and prosaccade trials were ordered randomly, resulting in 'repeated' trials that were preceded by the same type of trial (i.e. antisaccade-antisaccade), and 'switched' trials that were preceded by the opposite type of trial. Comparisons of the single-task blocks and repeated trials of the mixed-task blocks indexed the mixed-list costs, which were small for prosaccades and insignificant for antisaccades. Comparison of the repeated and switched trials from the mixed-task blocks indexed the residual task-switch cost. Accuracy costs of task-switching and antisaccades were equivalent. The accuracy of trials incorporating both switching and antisaccades in a single response (i.e. switched antisaccade) equalled the product of the accuracies of doing each operation alone, supporting independence of these two functions. In contrast, the latency cost of antisaccade performance was 3 times greater than that of task-switching. Task-switching from prosaccades to antisaccades resulted in a paradoxical decrease in antisaccade latency. This decrease correlated with other indices of vigilance, with the paradoxical effect minimized in more attentive observers. The latency data suggest that either an antisaccade on the prior trial perturbs saccadic responses more than a task-switch, or concurrent task-switching specifically facilitates antisaccades. In either case, the paradoxical benefit of task-switching for antisaccades challenges current models of task-switching.

Adolescent↗

PubMed2002

Antisaccades and task switching: studies of control processes in saccadic function in normal subjects and schizophrenic patients.

Executive functions allow us to respond flexibly rather than stereotypically to the environment. We examined two such functions, task switching and inhibition in the antisaccade paradigm, in two studies. One study involved 18 normal subjects; the other, 21 schizophrenic patients and 16 age-matched controls. Subjects performed blocks of randomly mixed prosaccades and antisaccades. Repeated trials were preceded by the same type of trial (i.e., an antisaccade following an antisaccade), and switched trials were preceded by a trial of the opposite type. We measured accuracy rate and latency as indices of processing costs. Whereas schizophrenic patients had a threefold increase in error rate for antisaccades compared to normals, the effect of task switching on their accuracy did not differ from that in normal subjects. Moreover, the accuracy rate of trials combining antisaccade and task switching was equivalent to a multiplication of the accuracy rates from trials in which each was done alone. Schizophrenic latencies were disproportionately increased for antisaccades, but again they were no different from normal subjects in the effect of task switching. In both groups the effect of task switching on antisaccades was a paradoxical latency reduction. We conclude that the executive dysfunction in schizophrenia is not generalized but selective, sparing task switching from exogenous cues, in which the switch is limited to a stimulus-response remapping. The accuracy data in both groups support independence of antisaccade and task-switching functions. The paradoxical task-switching benefit in antisaccadic latency effects challenges current models of task switching. It suggests either carryover inhibition by antisaccadic performance in the prior trial or facilitation of antisaccades by simultaneous performance of other cognitive operations.

Attention↗