Abstract
Introduction. Damage to the temporal parietal junction is commonly linked to deficiencies in spatial attention, particularly in contralateral space. Other studies, however, have shown patients with unilateral parietal damage to have bilateral deficits in attention, particularly for those tasks that measure the temporal aspects of attention (Battelli et al., 2003; Husain and Rorden, 2003). This study seeks to measure the neural correlates of temporal attention using fMRI. Methods. In a blocked fMRI design, subjects viewed a quartet of disks (2 in each hemifield symmetric around the midline) flickering black and white for 1000 msec at a frequency of 8 Hz, with one disk in opposite phase relative to the other three. For 350 msec before and after the flicker, the disks consisted of stationary high contrast texture, with one disk having lower contrast than the others. Subjects were instructed to attend to the disks in either the left or right hemifield, and, in the temporal order task, report whether the disks were in or out of phase. In the texture task the subjects were instructed to report whether the disks in the attended hemifield had equivalent contrast. Results. GLM analysis on the individual subjects revealed a main effect of task in the TPJ for six of the ten subjects, with three additional subjects showing unilateral right TPJ activation during the temporal order judgments. A group analysis measuring for hemifield effects found stronger contralateral TPJ activation during the temporal order judgments as compared to the texture task. Conclusions. Our findings support the notion that the TPJ is involved in selectively attending to temporal features of visual stimuli. Our group analysis also suggests a bias towards the contralateral TPJ when these judgments are made on lateralized visual stimuli.
This work was supported in part by NSF BCS0748314 to EG.