►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.

Neural activity throughout the cortex is correlated with perceptual decisions, but inactivation studies suggest that only a small number of areas are necessary for these behaviors. Here we used virtual reality combined with optical recording and perturbation methods to show that the number of required cortical areas and their dynamics vary across related tasks with different cognitive computations.

► February 2018: Postdoc Athena Akrami publishes in Nature on Parametric Working Memory and Sensory History

Congratulations to Athena Akrami, whose paper in Nature is now out (link here).

Athena Akrami

In this paper, Athena combined formal algorithmic behavioral analysis, optogenetic inactivations, and electrophysiological recordings in rats to show that Posterior Parietal Cortex (PPC) is specifically involved in the representation and use of prior sensory experience in Parametric Working Memory (PWM) tasks, where rats compare two sequential auditory stimuli, separated by a delay.

Here’s two fantastic pieces, both on Athena’s paper, one a News and Views piece in Nature by Prof. Laura Busse: Working memory freed from the past, and the other in Neuron by Prof. f. Miguel Maravall : Cortical Lifelogging: The Posterior Parietal Cortex as Sensory History Buffer.