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Updated: Apr 25, 2026
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Central and Divided Visual Field Presentation of Emotional Images to Measure Hemispheric Differences in Motivated Attention
Published on: November 16, 2017
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Within-hemifield competition in early visual areas limits the ability to track multiple objects with attention.
Viola S Störmer1, George A Alvarez2, Patrick Cavanagh3
1Department of Psychology, Harvard University, Cambridge, Massachusetts 02138, and vstormer@fas.harvard.edu.
Summary
Dividing attention across visual hemifields enhances early visual processing, unlike within a single hemifield. This suggests early visual cortex modulation aids target tracking, but within-hemifield competition limits this effect.
Area of Science:
- Neuroscience
- Cognitive Psychology
- Visual Perception
Background:
- Dividing attention is easier across separate visual hemifields than within the same hemifield.
- Early cortical processing stages are crucial for visual attention and target tracking.
- Understanding attentional modulation in early visual processing is key to explaining behavioral benefits.
Purpose of the Study:
- To investigate if the benefit of dividing attention across visual hemifields is present at early cortical processing stages.
- To determine if attentional modulations differ when attention is divided across versus within hemifields.
- To explore the impact of attention on both early and later visual processing stages.
Main Methods:
- Measured steady-state visual evoked potentials (ssVEPs) to flickering targets and distractors during a tracking task.
- Compared ssVEP amplitude differences between target and distractor frequencies across hemifield conditions.
- Examined the P3 component of event-related potentials for later processing stages.
Main Results:
- Attention modulated early visual processing (ssVEPs) when targets were in separate hemifields, but not within the same hemifield.
- Task performance (accuracy) was matched across conditions to rule out behavioral confounds.
- Later processing (P3 component) showed target-enhancement regardless of hemifield division, indicating higher-level processes were not constrained.
Conclusions:
- Early visual cortex processing is modulated by attention divided across hemifields, facilitating efficient target tracking.
- Competition within a single visual hemifield limits the ability to modulate multiple target representations in early visual cortex.
- Hemifields provide a functional separation that benefits attentional allocation at early sensory stages.
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