|
Abstract:
Abstract: Neuropsychological and functional imaging studies
have demonstrated hemispheric specialization for global and local
processing. This could be influenced by several factors including
attentional set. We have demonstrated differential activation of
two hemispheres during attention shift to global and local features
in a task using visual cues. In this study we investigated whether
the attentional hemispheric activation depends on the stimulus
feature of a cue. We recorded event-related brain potential (ERP)
during a task in which subjects were engaged in target selection at
either the global or local level. The target level was designated
by vocal cues delivered binaurally 800ms before the hierarchical
letter stimuli in a trial-by-trial fashion. Reaction time data
indicated a faster response to the global target compared to the
local one. Neural activity associated with cue-derived attention
shift to either global or local level was accessed by ERP changes
after cue presentation. The interaction between the target level
and hemisphere of recordings was observed biphasically from 250 to
350 ms and from 450 to 700 ms post cue onset. The topographical
analysis showed that the potential was more negative over the right
hemisphere for the global shift and more negative over the left
hemisphere for the local shift. The results confirmed the cerebral
asymmetry in top-down allocation of attention to the global and
local features independent of cue modalities.
|
