fMRI results: normal subjects, intraparietal
In intraparietal sulcus, we found something rather unexpected:
the activation is ipsilateral to the attended hemifield, instead of contralateral.
When we first saw this, we thought, `great, but why is it on the wrong side?' So we did what any good scientist would do: we ran some more subjects and hoped it would go away. In fact, the effect didn't go away, it got stronger.

In line with a couple of recent studies which have found that intraparietal sulcus activity varies as a function of the irrelevant information in the stimulus, we suggest that intraparietal sulcus is involved in active suppression of irrelevant stimuli.

In this type of experiment, in which subjects are constantly anticipating another shift and attention therefore may not settle fully on one hemifield or the other, early attentional selection and late attentional suppression may act in complementary roles: any input from the unattended field that manages to squeak through the early attentional gate would be actively suppressed at this later stage.

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`Physiological Studies of Attention in Autism: Implications for Autistic Cognition and Behaviour', Matthew Belmonte, 26 January 2002