York research finds new brain mechanism for perception during eye movements

Research undertaken at York University has shown, for the first time, areas of the brain that are sensitive to whether an object looks the same, or different, after making an eye movement.

Recently published in the journal Cortex, the findings in “Trans-saccadic interactions in human parietal and occipital cortex during the retention and comparison of object orientation” give York credit as the first to pinpoint where in the brain these signals appear.

Image: Modified from Dunkley et al. (2016), and depicting Ben Dunkley and Bianca Baltaretu

Image: Modified schematic of the hypothesized functional connections mediating the trans-saccadic integration of visual information from Dunkley et al. (2016). Below: Ben Dunkley and Bianca Baltaretu

The research was conducted out of Professor Doug Crawford’s Visuomotor Neuroscience Lab, with first author Ben Dunkley, a former post-doctoral fellow, and second author Bianca Baltaretu, a PhD candidate, taking the lead.

Drawing on what’s already known about how the brain keeps track of where things are, and how the brain perceives where and what things are, the team set out to determine how these two functions integrate.

“The challenge is understanding how these two things link together,” said Crawford, “especially when we keep moving our eyes all the time.

“When you see something happen, and then make a rapid eye movement (a saccade) to another location, how does your brain piece it all together to retain what things were, and where they were?”

A hypothetical example of this function would be a witness remembering which face matched which location at a crowded crime scene.

Using a variant of functional MRI (fMRI) adaptation, according to the study, the team recorded brain activity when a subject fixated to the left or right of a briefly presented visual grating, maintained fixation or saccaded to the opposite side, then judged whether a re-presentation of the grating has the same or different orientation.

“We found a couple of specific areas show this same/different modulation,” said Crawford. “One area is more in the visual part of the brain (occipital cortex), and one area is more in the spatial integration area (parietal cortex).

“We are the first to show these signals in the human brain.”

Doug Crawford

Doug Crawford

Crawford said while the findings are significant, past studies from his lab indicate these processes are not guaranteed, and could be susceptible to things like fatigue, brain damage, disease.

“Any of these could disrupt the function,” said Crawford, who added the research could spark investigations into health applications for the findings.

Studies on the subject will continue in Crawford’s lab with a focus on identifying whether these areas of the brain are “the” special trans-saccadic areas. Their future research will look at how the brain responds to different stimuli and different types of eye movement.

Full Reference: BT Dunkley, B Baltaretu, and JD Crawford (2016) Trans-saccadic interactions in human parietal and occipital cortex during the retention and comparison of object orientation. Cortex 82, pp 263-276

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