TORONTO, December 15, 2011 – Why is it so hard to suppress a glance at an attractive person? Why do we find ourselves rubbernecking at traffic accidents? According to a York University study, the brain’s primitive “inner eye” is to blame.
The study, published yesterday in the Journal of Neuroscience, focuses on the superior colliculus, a structure buried deep within the brain, inherited from animals like frogs and toads. This ancient visual system orients primitive animals toward food, danger, and sexual partners.
“We found that the superior colliculus performs a similar function in higher animals such as humans,” says study co-author Joseph DeSouza, assistant professor of psychology in York’s Faculty of Health. “This ‘inner eye’ is oriented towards survival, feeding and reproduction. As such, these types of gazes are more difficult to suppress,” he says.
Working with a team of investigators at the university’s Centre for Vision Research (CVR), DeSouza and fellow York professor Doug Crawford found that superior colliculus neurons produce a burst of activity during combined eye-and-head gaze shifts.
Crawford explains that they determined what the superior colliculus codes by recording neural activity during natural, variable eye and head movements. They then compared this activity to target locations (briefly-displayed visual stimuli) and gaze end-points (where the subjects actually looked), measured relative to the eye, head, or body.
“Despite being movement-related, superior colliculus neurons gave the most consistent activity compared to one simple variable: target location relative to the eyes. In this sense the superior colliculus provides an ‘inner eye' that drives eye and neck muscles toward the target,” says Crawford, professor of psychology in York’s Faculty of Health and Canada Research Chair in Visuomotor Neuroscience.
In previous work at the University of Western Ontario, DeSouza showed that a much newer system, the prefrontal cortex, is required to suppress these primitive responses.
Refreshingly, both sexes are equally “toad-like” when it comes to wandering eyes.
“The superior colliculus is gender neutral. Both women and men have trouble suppressing these primitive gazes. There is, however, the question of whether one gender tends to be more obvious about it,” DeSouza says.
The study, “Intrinsic Reference Frames of Superior Colliculus Visuomotor Receptive Fields during Head-Unrestrained Gaze Shifts,” was funded by a Canadian Institutes of Health Research (CIHR) grant to Crawford and DeSouza. The article’s other authors are: Gerald Keith, CVR post doc; Xiaogang Yan, CVR Research Associate, Gunnar Blohm, professor of neuroscience at Queen’s University, former CVR post doc; and Hongying Wang, CVR research associate.
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Media Contact:
Melissa Hughes, Media Relations, York University, 416 736-2100 ext. 22097, mehughes@yorku.ca
