Temporally evolving gain mechanisms of attention in macaque area V4

Ilaria Sani, Elisa Santandrea, Maria Concetta Morrone, Leonardo Chelazzi

Research output: Contribution to journalArticlepeer-review

Abstract

Cognitive attention and perceptual saliency jointly govern our interaction with the environment. Yet, we still lack a universally accepted account of the interplay between attention and luminance contrast, a fundamental dimension of saliency. We measured the attentional modulation of V4 neurons’ contrast response functions (CRFs) in awake, behaving macaque monkeys and applied a new approach that emphasizes the temporal dynamics of cell responses. We found that attention modulates CRFs via different gain mechanisms during subsequent epochs of visually driven activity: an early contrast-gain, strongly dependent on prestimulus activity changes (baseline shift); a time-limited stimulus-dependent multiplicative modulation, reaching its maximal expression around 150 ms after stimulus onset; and a late resurgence of contrast-gain modulation. Attention produced comparable time-dependent attentional gain changes on cells heterogeneously coding contrast, supporting the notion that the same circuits mediate attention mechanisms in V4 regardless of the form of contrast selectivity expressed by the given neuron. Surprisingly, attention was also sometimes capable of inducing radical transformations in the shape of CRFs. These findings offer important insights into the mechanisms that underlie contrast coding and attention in primate visual cortex and a new perspective on their interplay, one in which time becomes a fundamental factor. NEW & NOTEWORTHY We offer an innovative perspective on the interplay between attention and luminance contrast in macaque area V4, one in which time becomes a fundamental factor. We place emphasis on the temporal dynamics of attentional effects, pioneering the notion that attention modulates contrast response functions of V4 neurons via the sequential engagement of distinct gain mechanisms. These findings advance understanding of attentional influences on visual processing and help reconcile divergent results in the literature.

Original languageEnglish
Pages (from-to)964-985
Number of pages22
JournalJournal of Neurophysiology
Volume118
Issue number2
DOIs
Publication statusPublished - Aug 1 2017

Keywords

  • Contrast response functions
  • Gain mechanisms of attention
  • Macaque area V4
  • Spatial attention
  • Temporal dynamics

ASJC Scopus subject areas

  • Neuroscience(all)
  • Physiology
  • Medicine(all)

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