Middle temporal cortical visual area and visuospatial function in Galago senegalensis.

Bushbabies with lesions restricted to the middle temporal (MT) area and animals with larger extrastriate lesions including area MT were compared with normal control animals on test of visuospatial localization and discrimination learning. Ablation of area MT was sufficient to produce impairments in directing behavior appropriately on the basis of visuospatial cues. Extension of the lesion into areas 18 and 19 produced more profound deficits. Retardation in learning a stripe discrimination problem was correlated with the extent of damage to the geniculostriate system. It is hypothesized that area MT is important in achieving and maintaining fixation on a target whereas cortical areas 18 and 19 are necessary for establishing the location of stimulation in visual space.