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Ramezanpour H, Blizzard S, Kehoe DH, Fallah M. Oculomotor system can differentially process red and green colors during saccade programming in the presence of a competing distractor. Exp Brain Res 2022; 240:2847-2860. [PMID: 36100754 DOI: 10.1007/s00221-022-06459-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Accepted: 09/03/2022] [Indexed: 11/26/2022]
Abstract
Selective attention filters irrelevant information entering our brain to allow for fine-tuning of the relevant information processing. In the visual domain, shifts of attention are most often followed by a saccadic eye movement to objects and places of high relevance. Recent studies have shown that the stimulus color can affect saccade target selection and saccade trajectories. While those saccade modulations are based on perceptual color space, the level in the visual processing hierarchy at which color selection biases saccade programming remains unclear. As color has also been shown to influence manual response inhibition which is a key function of the prefrontal cortex, we hypothesized that the effects of color on executive functions would also inherently affect saccade programming. To test this hypothesis, we measured behavioral performance and saccade metrics during a modified saccadic Stroop task which reflects competition between color words ("RED" and "GREEN") and their color at the level of the prefrontal cortex. Our results revealed that the oculomotor system can differentially process red and green colors when planning a saccade in the presence of a competing distractor.
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Affiliation(s)
- Hamidreza Ramezanpour
- Centre for Vision Research, York University, Toronto, ON, Canada.
- School of Kinesiology and Health Science, Faculty of Health, York University, Toronto, ON, Canada.
- VISTA: Vision Science to Application, York University, Toronto, ON, Canada.
| | - Shawn Blizzard
- Centre for Vision Research, York University, Toronto, ON, Canada
- School of Kinesiology and Health Science, Faculty of Health, York University, Toronto, ON, Canada
| | - Devin Heinze Kehoe
- Centre for Vision Research, York University, Toronto, ON, Canada
- School of Kinesiology and Health Science, Faculty of Health, York University, Toronto, ON, Canada
- VISTA: Vision Science to Application, York University, Toronto, ON, Canada
| | - Mazyar Fallah
- Centre for Vision Research, York University, Toronto, ON, Canada.
- School of Kinesiology and Health Science, Faculty of Health, York University, Toronto, ON, Canada.
- VISTA: Vision Science to Application, York University, Toronto, ON, Canada.
- Department of Psychology, Faculty of Health, York University, 4700 Keele Street, Toronto, ON, M3J 1P3, Canada.
- Department of Human Health and Nutritional Sciences, College of Biological Science, University of Guelph, Guelph, ON, Canada.
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Abstract
Oculomotor target selection often requires discriminating visual features, but it remains unclear how oculomotor substrates encoding saccade vectors functionally contribute to this process. One possibility is that oculomotor vector representations (observed directly as physiological activation or inferred from behavioral interference) of potential targets are continuously re-weighted by task-relevance computed elsewhere in specialized visual modules, while an alternative possibility is that oculomotor modules utilize local featural analyses to actively discriminate potential targets. Strengthening the former account, oculomotor vector representations have longer onset latencies for ventral- (i.e., color) than dorsal-stream features (i.e., luminance), suggesting that oculomotor vector representations originate from featurally-relevant specialized visual modules. Here, we extended this reasoning by behaviorally examining whether the onset latency of saccadic interference elicited by visually complex stimuli is greater than is commonly observed for simple stimuli. We measured human saccade metrics (saccade curvature, endpoint deviations, saccade frequency, error proportion) as a function of time after abrupt distractor onset. Distractors were novel, visually complex, and had to be discriminated from targets to guide saccades. The earliest saccadic interference latency was ~110 ms, considerably longer than previous experiments, suggesting that sensory representations projected into the oculomotor system are gated to allow for sufficient featural processing to satisfy task demands. Surprisingly, initial oculomotor vector representations encoded features, as we manipulated the visual similarity between targets and distractors and observed increased vector modulation response magnitude and duration when the distractor was highly similar to the target. Oculomotor vector modulation was gradually extinguished over the time course of the experiment.
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Affiliation(s)
- Devin Heinze Kehoe
- Department of Psychology, York University, Toronto, Ontario, Canada.,Centre for Vision Research, York University, Toronto, Ontario, Canada.,VISTA: Vision Science to Applications, York University, Toronto, Ontario, Canada
| | - Jennifer Lewis
- Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, Ontario, Canada
| | - Mazyar Fallah
- Department of Psychology, York University, Toronto, Ontario, Canada.,Centre for Vision Research, York University, Toronto, Ontario, Canada.,VISTA: Vision Science to Applications, York University, Toronto, Ontario, Canada.,School of Kinesiology and Health Science, York University, Toronto, Ontario, Canada
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