Spatial attention decorrelates intrinsic activity fluctuations in macaque area V4.
Attention typically amplifies neuronal responses evoked by task-relevant stimuli while attenuating responses to task-irrelevant distracters. In this context, visual distracters constitute an external source of noise that is diminished to improve attended signal quality. Activity that is internal to the cortex itself, stimulus-independent ongoing correlated fluctuations in firing, might also act as task-irrelevant noise. To examine this, we recorded from area V4 of macaques performing an attention-demanding task. The firing of neurons to identically repeated stimuli was highly variable. Much of this variability originates from ongoing low-frequency (<5 Hz) fluctuations in rate correlated across the neuronal population. When attention is directed to a stimulus inside a neuron's receptive field, these correlated fluctuations in rate are reduced. This attention-dependent reduction of ongoing cortical activity improves the signal-to-noise ratio of pooled neural signals substantially more than attention-dependent increases in firing rate.
Systems Neurobiology Lab, The Salk Institute, La Jolla, CA 92037-1099, USA.
Jude F
JF
Mitchell
Kristy A
KA
Sundberg
John H
JH
Reynolds
D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D001288:Attention / Q000502:physiology*; D008251:Macaca / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D009483:Neuropsychological Tests; D010775:Photic Stimulation / Q000379:methods; D011930:Reaction Time; D013028:Space Perception / Q000502:physiology*; D013223:Statistics as Topic; D013997:Time Factors; D014793:Visual Cortex / Q000166:cytology* / Q000502:physiology; D014794:Visual Fields; D014795:Visual Pathways