Biology subjects

Redish, A. D.

Publications and source records attributed to Redish, A. D..

5 recordsLinked to original sources

bioRxiv2023

Distinct mesoscale cortical dynamics encode search strategies during spatial navigation

Spatial navigation is a complex cognitive process that involves neural computations in distributed regions of the brain. Little is known about how cortical regions are coordinated when animals navigate novel spatial environments or how that coordination changes as environments become familiar. We recorded mesoscale calcium (Ca2+) dynamics across large swathes of the dorsal cortex in mice solving the Barnes maze, a 2D spatial navigation task where mice used random, serial, and spatial search strategies to navigate to the goal. Cortical dynamics exhibited patterns of repeated calcium activity with rapid and abrupt shifts between cortical activation patterns at sub-second time scales. We used a clustering algorithm to decompose the spatial patterns of cortical calcium activity in a low dimensional state space, identifying 7 states, each corresponding to a distinct spatial pattern of cortical activation, sufficient to describe the cortical dynamics across all the mice. When mice used serial or spatial search strategies to navigate to the goal, the frontal regions of the cortex were reliably activated for prolonged durations of time (> 1s) shortly after trial initiation. These frontal cortex activation events coincided with mice approaching the edge of the maze from the center and were preceded by temporal sequences of cortical activation patterns that were distinct for serial and spatial search strategies. In serial search trials, frontal cortex activation events were preceded by activation of the posterior regions of the cortex followed by lateral activation of one hemisphere. In spatial search trials, frontal cortical events were preceded by activation of posterior regions of the cortex followed by broad activation of the lateral regions of the cortex. Our results delineated cortical components that differentiate goal- and non-goal oriented spatial navigation strategies.

neuroscience↗

bioRxiv2023

Reward prediction-errors weighted by cue salience produces addictive behaviors in simulations, with asymmetrical learning and steeper delay discounting

Dysfunction in learning and motivational systems are thought to contribute to addictive behaviours. Previous models have suggested that dopaminergic roles in learning and motivation could produce addictive behaviours through pharmacological manipulations that provide excess dopaminergic signalling towards these learning and motivational systems. Redish 2004 suggested a role based on dopaminergic signals of value prediction error, while Zhang et al. 2009 suggested a role based on dopaminergic signals of motivation. Both these models present significant limitations. They do not explain the reduced sensitivity to drug-related costs/negative consequences, the increased impulsivity generally found in people with a substance use disorder, craving behaviours, and non-pharmacological dependence, all of which are key hallmarks of addictive behaviours. Here, we propose a novel mathematical definition of salience, that combines aspects of dopamines role in both, learning and motivation, within the reinforcement learning framework. Using a single parameter regime, we simulated addictive behaviours that the Zhang et al. 2009 and Redish 2004 models also produce but we went further in simulating the downweighting of drug-related negative prediction-errors, steeper delay discounting of drug rewards, craving behaviours and aspects of behavioural/non-pharmacological addictions. The current salience model builds on our recently proposed conceptual theory that salience modulates internal representation updating and may contribute to addictive behaviours by producing misaligned internal representations (Kalhan et al., 2021). Critically, our current mathematical model of salience argues that the seemingly disparate learning and motivational aspects of dopaminergic functioning may interact through a salience mechanism that modulates internal representation updating.

neuroscience↗

bioRxiv2022

Differential processing of decision information in subregions of rodent medial prefrontal cortex

Decision-making involves multiple cognitive processes requiring different aspects of information about the situation at hand. The rodent medial prefrontal cortex (mPFC) has been hypothesized to be central to these abilities. Functional studies have sought to link specific processes to specific anatomical subregions, but past studies of mPFC have yielded controversial results, leaving the precise nature of mPFC function unclear. To settle this debate, we recorded from the full dorso-ventral extent of mPFC in each of 8 rats, as they performed a complex economic decision task. These data revealed four distinct functional domains within mPFC that closely mirrored anatomically-identified subregions, including novel evidence to divide prelimbic cortex into dorsal and ventral components. We found that dorsal aspects of mPFC (ACC, dPL) were more involved in processing information about active decisions, while ventral aspects (vPL, IL) were more engaged in motivational factors. Impact StatementDiehl and Redish describe how the rodent medial prefrontal cortex is composed of functionally distinct subregions that process economic decision information differentially along a dorso-ventral gradient.

neuroscience↗

bioRxiv2021

Sunk cost sensitivity in mice, rats, and humans on the Restaurant Row and WebSurf tasks cannot be explained by attrition biases alone

In a recent bioRxiv preprint, Ott et al. argue that sensitivities to sunk costs that have been reported in two serial foraging tasks (the Restaurant Row task in mice and rats, and the Web-Surf task in humans) may be due to simple consequences of the way that subjects perform these tasks and not due to an actual sensitivity to sunk costs. However, several variants of these tasks have been studied, in which the sensitivity to sunk costs changes. In order to test the Ott et al. model against these experimental observations, we simulated the model under these additional experimental conditions. We find that it is incompatible with the actual data. While we applaud the simplicity of the Ott et al. model, we must reject it as an explanation for the observed sensitivity to sunk costs seen in these tasks. We thus conclude that the alternative explanation - that mice, rats, and humans are sensitive to actual sunk costs in these tasks - is a better explanation for the data.

neuroscience↗

bioRxiv2019

Divergent strategies for learning in males and females

A frequent assumption in value-based decision-making tasks is that agents make decisions based on the feature dimension that reward probabilities vary on. However, in complex, multidimensional environments, stimuli can vary on multiple dimensions at once, meaning that the feature deserving the most credit for outcomes is not always obvious. As a result, individuals may vary in the strategies used to sample stimuli across dimensions, and these strategies may have an unrecognized influence on decision-making. Sex is a proxy for multiple genetic and endocrine influences that can influence decision-making strategies, including how environments are sampled. In this study, we examined the strategies adopted by female and male mice as they learned the value of stimuli that varied in both image and location in a visually-cued two-armed bandit, allowing two possible dimensions to learn about. Female mice acquired the correct image-value associations more quickly than male mice, and they used a fundamentally different strategy to do so. Female mice constrained their decision-space early in learning by preferentially sampling one location over which images varied. Conversely, male strategies were inconsistent, changing frequently and strongly influenced by the immediate experience of stochastic rewards. Individual strategies were related to sex-gated changes in neuronal activation in early learning. Together, we find that in mice, sex is linked with divergent strategies for sampling and learning about the world, revealing substantial unrecognized variability in the approaches implemented during value-based decision-making.

animal behavior and cognition↗