Do the two cerebral hemispheres have independent tracking resources? Evidence from undergraduate populations and a sample of video gamers and non-gamers

Date
2013
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University of Delaware
Abstract
Information in each visual field is initially processed in visual areas located in the contralateral hemisphere. This segregation of information between the two hemispheres quickly gives way to integrated representations that result from the rapid sharing of information across the corpus callosum. An exception to this integration process is provided by split brain patients who have had their corpus callosum severed (Myers and Sperry, 1958). This operation results in superior performance of split-brain patients compared to controls on several visual tasks, such as the ability to search for targets in the two visual fields simultaneously resulting in a doubling of search speed compared to controls (Luck, Hillyard, Mangun and Gazzaniga, 1989). In contrast, presenting bilateral displays to normal observers generally results in an advantage relative to unilateral presentation but one that is considerably less than the doubling of performance seen in split-brain patients. An exception to this rule was reported by Alvarez & Cavanagh (2005) who found that bilateral presentation in a multiple object tracking task (MOT) allowed observers to track twice as many objects relative to unilateral presentation. They suggested that the two cerebral hemispheres acted as independent object tracking systems in MOT. In the first experiment evidence for independent tracking systems were investigated. However, only a bilateral advantage that fell well short of the doubling of performance predicted by independent tracking systems was found. In a second experiment a population with extensive experience playing video games was compared to non-gamers on measures of independent tracking resources. Video gamers have increased visual skills in tasks such as MOT (Green and Bavelier, 2006). Our results show video gamers outperformed non-gamers during bilateral tracking. This suggests that some individual differences may be associated with the bilateral hemispheric advantage. However, evidence for completely independent resources in the two cerebral hemispheres is still lacking. Video gamers in our study only showed a bilateral advantage for tracking objects in two visual fields and not independence. Examining individual differences in a population shown to have high performance on MOT was insufficient to replicate results of Alvarez and Cavanagh (2005).
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