BEACON Seminar: The geometry of the representation of decision variable and stimulus difficulty in the parietal cortex
Roozbeh Kiani (NYU)
BEACON Seminar Series
Tuesday, 19 October 2021, 2pm to 3pm
Hosted by Nima Khalighinejad
Find out more about the speaker: https://as.nyu.edu/faculty/roozbeh-kiani.html.
Seminars this term will be held remotely on Zoom. Links for joining will be sent out before each seminar. Please contact the host if you would like to set up a remote meeting with a speaker. If you have suggestions for future speakers, please contact Lauren (firstname.lastname@example.org), or Nima (email@example.com).
Lateral intraparietal (LIP) neurons represent formation of perceptual decisions involving eye movements. In circuit models for these decisions, neural ensembles that encode actions compete to form decisions. Consequently, decision variables (DVs) are represented as partially potentiated action plans, where ensembles increase their average responses for stronger evidence supporting their preferred actions. As another consequence, DV representation and readout are implemented similarly for decisions with identical competing actions, irrespective of input and task context differences. In my talk, I will challenge those core principles using a novel face-discrimination task, where LIP firing rates decrease with supporting evidence, contrary to conventional motion-discrimination tasks. These opposite response patterns arise from similar mechanisms in which decisions form along curved, one-dimensional population-response manifolds misaligned with action representations. These manifolds rotate in state space based on task context, necessitating distinct readouts. I will show similar manifolds in lateral and medial prefrontal cortices, suggesting a ubiquitous representational geometry across decision-making circuits.