Authors:

MANLY, T., OWEN, A.M., Datta, A., Lewis, G., Scott, S., Rorden, C., Pickard, J. & Robertson, I.

Reference:

Year of publication:

2001

CBU number:

5037

Abstract:

Patients with lesions to the right prefrontal cortex have been reported to show impairments in the voluntary maintenance of attention to tasks which lack sufficient stimulation to exogenously capture such resources. To date, functional imaging studies with healthy participants have shown increased activation in right frontal and parietal cortices during sustained attention tasks relative to rest. Here we present a functional imaging demonstration that reducing the challenge within a task to an apparently trivial level is accompanied by increased activation in the right frontal and parietal cortices in healthy human subjects. Participants performed a task in which they were required to make a response to each regularly presented visual digit (1 to 9) with the exception of a nominated target. In the challenging condition, the sequence was randomised such that a target might appear on any trial. In the unchallenging condition the sequence was fixed into a conventionally ascending order such that the presentation of a target was entirely predictable. Significant increases in regional cerebral blood flow in right dorsolateral prefrontal and posterior parietal cortices were associated with this condition. The results are consistent with a right hemisphere dominant system for the top-down maintenance of an alert, attentive state in the absence of sufficient exogenous stimulation for such continued processing - and with recent studies showing significant deficits in traumatically brain injured patients (in whom frontal damage is probable) on the task.