Author Archives: carlos

►November 2020: Sue Ann Koay publishes in eLife on amplitude modulations of pulsatile sensory responses during evidence accumulation in mice

Sue Ann Koay

Sue Ann Koay, Stephan Thiberge, Carlos Brody, David Tank, “Amplitude Modulations of Cortical Sensory Responses in Pulsatile Evidence Accumulation.” eLife 2020.

How does the brain internally represent a sequence of sensory information that jointly drives a decision-making behavior? Studies of perceptual decision-making have often assumed that sensory cortices provide noisy but otherwise veridical sensory inputs to downstream processes that accumulate and drive decisions. However, sensory processing in even the earliest sensory cortices can be systematically modified by various external and internal contexts. We recorded from neuronal populations across posterior cortex as mice performed a navigational decision-making task based on accumulating randomly timed pulses of visual evidence. Even in V1, only a small fraction of active neurons had sensory-like responses time-locked to each pulse. Here, we focus on how these ‘cue-locked’ neurons exhibited a variety of amplitude modulations from sensory to cognitive, notably by choice and accumulated evidence. These task-related modulations affected a large fraction of cue-locked neurons across posterior cortex, suggesting that future models of behavior should account for such influences.

►October 2020: Thomas Luo, Adrian Bondy, et al. publish in eLife on chronic Neuropixel recording methods in freely moving rats

Thomas Luo
Adrian Bondy
Adrian Bondy

Thomas Luo*, Adrian Bondy*, Diksha Gupta, Verity Elliott, Charles Kopec, Carlos Brody, “An approach for long-term, multi-probe Neuropixels recordings in unrestrained rats”, eLife 2020

The use of Neuropixels probes for chronic neural recordings is in its infancy and initial studies leave questions about long-term stability and probe reusability unaddressed. Here, we demonstrate a new approach for chronic Neuropixels recordings over a period of months in freely moving rats. Our approach allows multiple probes per rat and multiple cycles of probe reuse. We found that hundreds of units could be recorded for multiple months, but that yields depended systematically on anatomical position. Explanted probes displayed a small increase in noise compared to unimplanted probes, but this was insufficient to impair future single-unit recordings. We conclude that cost-effective, multi-region, and multi-probe Neuropixels recordings can be carried out with high yields over multiple months in rats or other similarly sized animals. Our methods and observations may facilitate the standardization of chronic recording from Neuropixels probes in freely moving animals.

► Aug 2017: grad student Alex Piet’s paper is out in Neural Computation

Alex Piet

Congratulations to graduate student Alex Piet, whose paper in Neural Computation is now out (link here).

In this paper Alex uses two-node attractor network models to  figure out what neural mechanisms could lead to FOF (a rat cortical region) contributing to decision-making as the lab found in Erlich et al. eLife 2015 and Erlich et al. Neuron 2011. Alex’s results point to specific mechanisms in which the FOF contributes “post-categorization” memory, and make some predictions that Alex then confirmed as correct in a post-hoc analysis of the data.

► June 2017: postdocs Ben Scott and Christine Constantinople publish in Neuron on calcium imaging during accumulation of evidence


Christine Constantinople

Ben Scott

Congratulations to Ben Scott and Christine Constantinople, co-first authors of a paper in Neuron describing how calcium imaging recordings during accumulation of evidence reveal that evidence is encoded in heterogeneous neural responses that have a wide diversity of timescales.