Visual search and visual working memory in patients with chronic focal cortical lesions

Abstract

Visually guided behavior is known to involve temporo-parietal, inferotemporal, and prefrontal cortex and each of these areas appears to contribute to visual working memory. We explored the extent to which chronic lesions in one of these cortical areas affect visually guided oculomotor performance. We also explore whether possible impairments become more pronounced with increasing memory load. With this aim we recorded saccadic eye movements in 19 patients with a chronic focal postsurgical lesion in either temporo-parietal, inferior temporal or prefrontal cortex. Their results are compared to those of 19 age-matched volunteers. The subjects performed three different visual search tasks with increasing memory load: Instructed search, cue-guided search and memory-guided search. In addition, the latter task was performed with a short (1 s) and a long (6 s) delay. All tasks required the subjects to make a saccade to a single target presented together with one or three distractors. The results indicate that patients with inferotemporal lesions make the most task-related errors. Saccadic reaction times (SRTs) were significantly prolonged in patients with temporo-parietal and prefrontal lesions, but were unaffected in the patients with lesions in the inferotemporal cortex. The spatial accuracy of saccades was lowest in patients with temporo-parietal lesions. An increase in memory load led to more errors, to longer reaction times and to lower saccadic precision. However, the effect was similar across the three patient groups and the controls. An error analysis indicated that both patients and controls tended to weight global (luminance contrast and form) features higher than local features (line-segment orientation) when making difficult perceptual decisions.

Effect of Vibration Stimulation to Neck Extensor Muscles on Reaction Time in Various Saccadic Eye Movements

“…Furthermore, the reaction time in anti-saccade was longer than that in memory-guided saccade. These findings are similar to those of other studies (Ettinger et al, 2005;Evdokimidis et al, 1996;Everling et al, 1997;Greenlee et al, 2000;Müller et al, 1999).…”

Human Frontal Eye Fields and Visual Search

“…These results show that the human FEFs are essential for normal visual search performance in the absence of the requirement for eye movements. The absence of a FEF effect on the simple feature search is not surprising since the high saliency and predictability of feature targets is detectable with redundancy in several visual areas (Greenlee et al 2002), many of which are connected with FEFs (Bullier 2001;Bullier et al 1996). The modulation of performance in the conjunction task is consistent with neuronal recording evidence that has implicated FEFs in forming a saliency map during tasks that present complex visual scenes (Thompson et al 1997(Thompson et al , 2001.…”

Morphological Correlates of Corticosteroid-Induced Changes in Prefrontal Cortex-Dependent Behaviors

“…This concept, originally based on studies in humans and other primates (Greenlee et al, 2000;Petrides, 2000;Rowe and Passingham, 2001), has been shown to apply to rats using a variety of rigorous tests, including the radial-arm maze (Fritts et al, 1998), a matching-to-sample task on a T-maze (Dias and Aggleton, 2000), a delayed-response task (Mizoguchi et al, 2000), or the spatial working memory version of the Morris water maze (Kesner, 2000). The key feature of these tests is that the information presented is manipulated before the subject is tested for its ability to make an appropriate behavioral response; these tasks therefore contrast sharply with simple short-term memory tasks involving recognition and recall, abilities that are spared from impairment after PFC damage (Lacroix et al, 2002).…”