S. Treue et Jhr. Maunsell, Effects of attention on the processing of motion in macaque middle temporal and medial superior temporal visual cortical areas, J NEUROSC, 19(17), 1999, pp. 7591-7602
The visual system is continually inundated with information received by the
eyes. Only a fraction of this information appears to reach visual awarenes
s. This process of selection is one of the functions ascribed to visual att
ention. Although many studies have investigated the role of attention in sh
aping neuronal representations in cortical areas, few have focused on atten
tional modulation of neuronal signals related to visual motion. We recorded
from 89 direction-selective neurons in middle temporal (MT) and medial sup
erior temporal (MST) visual cortical areas of two macaque monkeys using ide
ntical sensory stimulation under various attentional conditions. Neural res
ponses in both areas were greatly influenced by attention. When attention w
as directed to a stimulus inside the receptive field of a neuron, responses
in MT and MST were enhanced an average of 20 and 40% compared with a condi
tion in which attention was directed outside the receptive field. Even stro
nger average enhancements (70% in MT and 100% in MST) were observed when at
tention was switched from a stimulus moving in the nonpreferred direction i
nside the receptive field to another stimulus in the receptive field that w
as moving in the preferred direction. These findings show that attention mo
dulates motion processing from stages early in the dorsal visual pathway by
selectively enhancing the representation of attended stimuli and simultane
ously reducing the influence of unattended stimuli.