Orienting of visual attention was studied in 8 patients with progressive supranuclear palsy (PSP) and 8 parkinsonian control subjects. While maintaining fixation on the centre of a visual display, subjects made simple reaction time (RT) key press responses on detecting visual targets which appeared above, below, to the left or right, equidistant from fixation. On each trial the target was preceded by a preparatory cue, either a peripheral luminance change or a central arrow, to summon attention to one of the four locations. The orienting of attention was measured as a facilitation in detection RI at the cued location. For the parkinsonian controls, this facilitation was equal for horizontal and vertical directions, whereas for both types of cues, PSP patients were slower moving attention in the vertical than in the horizontal plane. Midbrain retinotectal pathways are important not only for controlling eye movements, but also for orienting attention.

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