Robust coding of eye position in posterior parietal cortex despite context-dependent tuning

Jamie R. Mcfadyen, Barbara Heider, Anushree N. Karkhanis, Shaun Cloherty, Fabian Muñoz, Ralph M. Siegel, Adam P. Morris

Research output: Contribution to journalArticleResearchpeer-review


Neurons in posterior parietal cortex (PPC) encode many aspects of the sensory world (e.g., scene structure), the posture of the body, and plans for action. For a downstream computation, however, only some of these dimensions are relevant; the rest are “nuisance variables” because their influence on neural activity changes with sensory and behavioral context, potentially corrupting the read-out of relevant information. Here we show that a key postural variable for vision (eye position) is represented robustly in male macaque PPC across a range of contexts, although the tuning of single neurons depended strongly on context. Contexts were defined by different stages of a visually guided reaching task, including (1) a visually sparse epoch, (2) a visually rich epoch, (3) a “go” epoch in which the reach was cued, and (4) during the reach itself. Eye position was constant within trials but varied across trials in a 3 × 3 grid spanning 24° × 24°. Using demixed principal component analysis of neural spike-counts, we found that the subspace of the population response encoding eye position is orthogonal to that encoding task context. Accordingly, a context-naive (fixed-parameter) decoder was nevertheless able to estimate eye position reliably across contexts. Errors were small given the sample size (∼1.78°) and would likely be even smaller with larger populations. Moreover, they were comparable to that of decoders that were optimized for each context. Our results suggest that population codes in PPC shield encoded signals from crosstalk to support robust sensorimotor transformations across contexts.
Original languageEnglish
Pages (from-to)4116-4130
Number of pages15
JournalThe Journal of Neuroscience
Issue number20
Publication statusPublished - 18 May 2022


  • Bayesian
  • decode
  • eye position
  • gaze
  • orthogonal
  • PPC

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