Attentional modulation strength in cortical area MT depends on stimulus contrast.
The attentional modulation of sensory information processing in the visual system is the result of top-down influences, which can cause a multiplicative modulation of the firing rate of sensory neurons in extrastriate visual cortex, an effect reminiscent of the bottom-up effect of changes in stimulus contrast. This similarity could simply reflect the multiplicity of both effects. But, here we show that in direction-selective neurons in monkey visual cortical area MT, stimulus and attentional effects share a nonlinearity. These neurons show higher response gain for both contrast and attentional changes for intermediate contrast stimuli and smaller gain for low- and high-contrast stimuli. This finding suggests a close relationship between the neural encoding of stimulus contrast and the modulating effect of the behavioral relevance of stimuli.
Martínez-Trujillo
Julio
J
Center for Vision Research, York University, Toronto Ontario, Canada.
Treue
Stefan
S
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D001288:Attention / Q000502:physiology; D015350:Contrast Sensitivity / Q000502:physiology*; D008029:Lighting; D008253:Macaca mulatta / Q000033:anatomy & histology / Q000502:physiology*; D009039:Motion Perception / Q000502:physiology*; D009474:Neurons / Q000166:cytology*; D010775:Photic Stimulation; D013702:Temporal Lobe / Q000166:cytology / Q000502:physiology*; D014793:Visual Cortex / Q000166:cytology / Q000502:physiology*; D014794:Visual Fields / Q000502:physiology; D014795:Visual Pathways / Q000166:cytology / Q000502:physiology*