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Isabel Dombrowe, Mieke Donk, Hayley Wright, Cristian NL Olivers, Glyn Humphreys; The time course of saccadic visual selection in patients with parietal damage.. Journal of Vision 2011;11(11):124. doi: 10.1167/11.11.124.
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© ARVO (1962-2015); The Authors (2016-present)
Previous research with healthy observers has shown that saccades with short latencies are predominantly stimulus-driven, whereas saccades with longer latencies become increasingly goal-driven. The parietal lobes may play a crucial role in this time course. The aim of the present study was to investigate whether patients with parietal damage have deficits in stimulus-driven processing, goal-driven processing, or both. To this end, we asked a group of patients with unilateral and bilateral parietal lesions and a group of healthy, age-matched controls to make a saccade to one of two oriented lines presented amongst homogeneous background lines. We systematically varied the salience of these lines by changing the orientation of the background elements. Saccadic target selection of the patient group was clearly impaired in the hemi-field contralateral to the main lesion. Although saccades with short latencies were mainly stimulus-driven, performance with longer latency saccades seemed to be at chance level. Performance with stimuli in the hemi-field ipsilateral to the main lesion was similar to that of the controls. We fitted a multinomial model, which allowed us to decompose the individual speed-accuracy functions into the underlying stimulus-driven and goal-driven functions. We found that stimulus-driven processing of stimuli in the more affected hemi-field decreased faster for patients than for controls, whereas goal-driven processing tended to set in later and increase slower. Stimulus-driven processing in the less affected hemi-field was intact. Some patients additionally showed impaired goal-driven processing in the less affected hemi-field. Our results show that stimulus-driven and goal-driven processes are differentially affected by parietal damage, suggesting that both processes are distinctly represented in the parietal lobes.
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