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Abstract:
Relatively little is known about the temporal dynamics and
representations that mediate object- and location-based attentional
cueing effects. Additive object- and location-based Inhibition of
Return (IOR) effects have been demonstrated in static displays
(Jordan and Tipper, 1998), providing a powerful tool to examine the
temporal dynamics of these inhibitory mechanisms. Event-related
potentials (ERPs), associated with the onset of a target in
locations that were either empty (Location condition) or marked by
modally completed objects (Object+Location condition), were
acquired across 128 sites. Reliable IOR effects were observed in
both conditions, with an increase in the magnitude of the cueing
effect in the Object+Location compared to the Location condition.
This increase was larger in the left compared to the right visual
field (Jordan and Tipper, under review). Consistent with a previous
report, IOR (McDonald et al, 1999) did reduce early ERP components.
Removing the object (location compared to object+location)
specifically modulated the cueing effects on negative ERP
components. Using substractive logic, specific cueing effects
associated with inhibiting objects were also identified in temporal
cortical regions, tentatively Frontal Eye Fields. Finally,
consistent with the behavioral responses, a differential
time-course for the inhibition of objects appearing in left/right
visual hemifields was observed. This study provides confirmatory
evidence for left/right hemifield asymmetries as a marker for
object-based IOR and suggests differential dynamics and cortical
substrates for attentional inhibitory effects associated with
object and locations.
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