Combining event-related potentials and eye-tracking to assess the effect of attention on cortical responses L Kulke, J Wattam-Bell |
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Department of Developmental Science, University College London, United Kingdom
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| Directing attention towards a stimulus enhances brain responses to that stimulus (e.g. Morgan et al, 1996, PNAS, 93, 4770–4774). Methods for investigating these effects usually involve instructing subjects to voluntarily direct attention towards a particular location, making them unsuitable for infants and other groups with poor communication. Here, we describe an approach based on fixation shifts (Atkinson et al, 1992, Perception, 21, 643), a method for behavioural assessment of attention in infants that does not depend on explicit instruction. We used event-related potentials (ERPs) to measure cortical activity preceding fixation shifts to peripheral targets. A remote eye-tracker was used to determine which target was fixated and the timing of the eye-movement towards it. With two identical targets presented at equivalent locations in left and right visual fields, adults showed an enhanced response at around 100 msec in occipital ERP channels contralateral to the subsequently fixated target, consistent with an effect of covert attention prior to the overt switch. Our initial results suggest this is a promising approach to investigating the effects of attention on cortical activity in infants and other populations who cannot follow instructions. |
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