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Abstract:
Biases of spatial attention are a common outcome of
unilateral brain injury in humans. Such biases may manifest as
spatial neglect or extinction for contralesional stimuli. We
examined the effect of attentional load at fixation on responses to
peripheral targets made by patients with right parietal damage.
Patients had to detect brief peripheral visual targets (left, right
or below central fixation), while monitoring a central RSVP stream
containing alphanumeric characters. In the 'no report' condition,
patients could devote their covert attention exclusively to the
peripheral target-detection task. In the 'low central-load'
condition, patients had to report the presence of any green item in
the central stream of red items; in the 'high central-load'
condition they reported the presence of any red letter in a central
stream of red-digits. In all three conditions, patients were worse
in accuracy and speed for peripheral targets on the left versus the
right or below fixation. This spatial gradient became steeper with
increases in the attentional load of the central RSVP task.
Moreover, the different spatial gradients associated with the low-
and high-load tasks applied regardless of whether a target appeared
in the RSVP stream. This suggests that mere expectancy of a
particular central target modulated the lateral gradient of spatial
attention.
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