► June 2021: Ann Duan, Marino Pagan, and Alex Piet publish in Nature Neuroscience on the Superior Colliculus and Executive Control

Chun-Yu (Ann) Duan
Chun-Yu (Ann) Duan
Marino Pagan
Alex Piet

We’re very excited to see this paper out! How does SC contribute to executive control? Our data suggests that the SC can be at the very heart of executive control, responsible for combining cognitive control signals with sensory inputs to compute context-appropriate responses. Remarkably, the fully context-appropriate responses can be decoded from SC neurons almost 200 ms faster than from cortical neurons (wow!), suggesting the computation may be led, and happen, in the SC itself. Circuit modeling supports this idea, with large-scale searches revealing a wide variety of possible SC circuits that would achieve this and that are compatible with the experimental data.

Abstract: Context-based sensorimotor routing is a hallmark of executive control. Pharmacological inactivations in rats have implicated the midbrain superior colliculus (SC) in this process. But what specific role is this, and what circuit mechanisms support it? Here we report a subset of rat SC neurons that instantiate a specific link between the representations of context and motor choice. Moreover, these neurons encode animals’ choice far earlier than other neurons in the SC or in the frontal cortex, suggesting that their neural dynamics lead choice computation. Optogenetic inactivations revealed that SC activity during context encoding is necessary for choice behavior, even while that choice behavior is robust to inactivations during choice formation. Searches for SC circuit models matching our experimental results identified key circuit predictions while revealing some a priori expected features as unnecessary. Our results reveal circuit mechanisms within the SC that implement response inhibition and context-based vector inversion during executive control.

►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.