Biomedical subjects

R Egly

Publications and source records attributed to R Egly.

8 recordsLinked to original sources

PubMed1998

Spatial attention deficits in humans: a comparison of superior parietal and temporal-parietal junction lesions.

Although clinical evidence of spatial attention deficits, such as neglect and extinction, is typically associated with lesions of the right temporal-parietal junction, recent evidence has suggested an important role for the superior parietal lobe. Two groups of patients, selected for lesions at the temporal-parietal junction including the superior temporal gyrus (TPJ group), or for lesions involving the parietal but not the superior temporal region (PAR group), performed cued-target detection tasks in 2 experiments. An extinction-like response time pattern was found for the TPJ but not the PAR group. In addition, both groups were able to use expectancy information, in the form of cue predictiveness, suggesting that separate mechanisms mediate exogenous and endogenous processes during attention shifts.

Adult↗

PubMed1997

Object-based facilitation and inhibition from visual orienting in the human split-brain.

Object-based attention was examined in 2 split-brain patients. A precued object could move within a visual field or cross the midline to the opposite field. Normal individuals show an inhibition in detecting signals in the cued object whether it moves within or between fields. Both patients showed this effect when the cued object moved within a visual field. When it crossed the midline into the opposite visual field, however, detection was faster in the cued box. These results reveal both facilitatory and inhibitory effects on attention that are object based and may last for several hundred milliseconds. However, the inhibition requires an intact corpus callosum for interhemispheric transfer, whereas the facilitation is transferred subcortically.

Adult↗

PubMed1996

Response channel activation and the lateral prefrontal cortex.

The role of lateral prefrontal cortex in transducing perception into action was studied in 10 patients with chronic, unilateral lesions. They identified colors in the center of a visual display, while a flanking, distractor color was presented simultaneously in either the ipsilesional or contralesional field. The flanker could be either the same color as the target, or incompatible with the correct response. The effects of compatible and incompatible flankers on reaction time (RT) served as a measure of response channel activation by the flanker. Flankers in the contralesional field influenced RT less than did those in the ipsilesional field. These results suggest that the lateral prefrontal cortex is involved in maintaining stimulus-response channels.

Adult↗

PubMed1994

Shifting visual attention between objects and locations: evidence from normal and parietal lesion subjects.

Space- and object-based attention components were examined in neurologically normal and parietal-lesion subjects, who detected a luminance change at 1 of 4 ends of 2 outline rectangles. One rectangle end was precued (75% valid); on invalid-cue trials, the target appeared at the other end of the cued rectangle or at 1 end of the uncued rectangle. For normals, the cost for invalid cues was greater for targets in the uncued rectangle, indicating an object-based component. Both right- and left-hemisphere patients showed costs that were greater for contralesional targets. For right-hemisphere patients, the object cost was equivalent for contralesional and ipsilesional targets, indicating a spatial deficit, whereas the object cost for left-hemisphere patients was larger for contralesional targets, indicating an object deficit.

Adult↗

PubMed1994

Effects of inhibition of return on voluntary and visually guided saccades.

Four experiments examined the effects of inhibition of return on endogenously generated and visually guided saccades. In Experiments 1-3, subjects responded to a peripheral target by making either a prosaccade (toward the target) or an antisaccade (toward the field opposite the target). Prior to the appearance of the target, one of the two equiprobable target locations was activated by presenting a peripheral precue (Experiments 1 and 2), or by executing an endogenous saccade in response to a central precue (Experiment 3). In Experiment 1, the eyes remained fixed when the cue appeared; in Experiment 2 subjects made a saccade to the peripheral cue, and returned their eyes to the centre before the target appeared. In both experiments, saccade latencies were longer for targets appearing at the precued location for both prosaccade and antisaccade tasks. In Experiment 3, saccade latencies were longer for targets appearing at the precued location only in the prosaccade task; no effect of the precue was obtained in the antisaccade task. These results suggest that endogenously generated saccades activate both an inhibition of target detection and a motor alternation bias. Experiment 4 showed that inhibition of return generated by a peripheral precue increased the latency for a subsequent endogenous saccade (from a central, arrow target) toward the precued location. Inhibition of return may affect perceptual processing and also produce a motor alternation bias dependent upon whether it is activated exogenously or endogenously.

Attention↗

PubMed1993

Spatial attention and cuing to global and local levels of hierarchical structure.

Five experiments investigated the role of attention in identifying global and local targets in hierarchically structured patterns. Hierarchical patterns were presented at a variable stimulus onset asynchrony (SOA) either after a cue (4 arrows or shaded boxes) or after no cue. Targets occurred at the cued level 80% of the time and at the uncued level 20%. On uncued trials, target level probability was .5. Global cues produced benefits for both global and local targets over SOA on cued trials. Local cues produced benefits only for local targets. For uncued trials, responses favored local targets overall when interspersed with locally cued trials but favored global targets when interspersed with globally cued trials. The role of an attentional window and discrete distribution of attention over global and local levels of hierarchical patterns are discussed.

Adult↗

PubMed1991

Reallocation of visual attention.

Attentional movement time was investigated within and across hemifields in a discrimination task in which retinal acuity was controlled. Ss discriminated targets in a two-alternative, forced-choice latency paradigm. In Experiments 1-3, costs were mediated by distance, even though it was varied independently of acuity. In Experiments 4 and 7, with distance held constant, costs were equivalent for crossing the vertical and horizontal meridians and for crossing 1 and 2 meridians. However, crossing 1 meridian produced costs that were less than the costs for shifts to unexpected locations in the same quadrant, partially replicating the inhibitory aftereffect of Tassinari, Aglioti,Chelazzi,Marzi,and Berlucchi (1987). An explanation based on a combination of analog movement (Tsal, 1983) and attentional distribution (Downing & Pinker, 1985; Hughes & Zimba, 1987; Tassinari et al., 1987) models was discussed.

Adult↗

PubMed1984

Sensitization of the visual field.

Three experiments investigated the identification or localization of a letter that was displaced from the fixation point by 1 degree-3 degrees. The subject's task was to identify a fixated letter and identify (Experiment 1) or localize (Experiments 2 and 3) the displaced letter. On uncued trials, the displaced letter could appear at any of eight locations on any of three rings surrounding the fixated letter; on cued trials, the ring containing the displaced letter was specified. The results indicated that cuing improved subjects' identification and localization of the displaced letter. Invalid cuing (Experiment 3) produced costs comparable in magnitude to the benefits. The distance of the target from the cued ring determined cost, but costs were unaffected by the appearance of a target within the presumed beam of attention. It was proposed that attention should be viewed as a general, rather than feature-specific, resource that can be voluntarily allocated to multiple regions of the visual field.

Attention↗