Biology subjects

Sleezer, B. J.

Publications and source records attributed to Sleezer, B. J..

4 recordsLinked to original sources

bioRxiv2022

Irrational choices via a curvilinear representational geometry for value

We make decisions by comparing values, but how is value represented in the brain? Many models assume, if only implicitly, that the representational geometry of value is linear. However, in part due to a historical focus on noisy single neurons, rather than neuronal populations, this hypothesis has not been rigorously tested. Here, we examined the representational geometry of value in the ventromedial prefrontal cortex (vmPFC), a part of the brain linked to economic decision-making. We found that values were encoded along a curved manifold in vmPFC. This curvilinear geometry predicted a specific pattern of irrational decision-making: that decision-makers will make worse choices when an irrelevant, decoy option is worse in value, compared to when it is better. Indeed, we observed these irrational choices in behavior. Together, these results not only suggest that the representational geometry of value is nonlinear, but that this nonlinearity could impose bounds on rational decision-making.

neuroscience↗

bioRxiv2021

Orthogonal but linked neural codes for value

Our ability to effectively choose between dissimilar options implies that information regarding the options values must be available, either explicitly or implicitly, in the brain. Explicit realizations of value involve single neurons whose responses depend on value and not on the specific features that determine it. Implicit realizations, by contrast, come from the coordinated action of neurons that encode specific features. One signature of implicit value coding is that population responses to offers with the same value but different features should occupy semi- or fully orthogonal neural subspaces that are nonetheless linked. Here, we examined responses of neurons in six core value-coding areas in a choice task with risky and safe options. Using stricter criteria than some past studies have used, we find, surprisingly, no evidence for abstract value neurons (i.e., neurons with the response to equally valued risky and safe options) in any of these regions. Moreover, population codes for value resided in orthogonal subspaces; these subspaces were linked through a linear transform of each of their constituent subspaces. These results suggest that in all six regions, populations of neurons embed value implicitly in a distributed population.

neuroscience↗

bioRxiv2021

Tonic activity in lateral habenula neurons promotes disengagement from reward-seeking behavior

Survival requires both the ability to persistently pursue goals and the ability to determine when it is time to stop, an adaptive balance of perseverance and disengagement. Neural activity in the lateral habenula (LHb) has been linked to aversion and negative valence, but its role in regulating the balance between reward-seeking and disengaged behavioral states remains unclear. Here, we show that LHb neural activity is tonically elevated during minutes-long disengagements from reward-seeking behavior, whether due to repeated reward omission or following sufficient consumption of reward. Further, we show that LHb inhibition extends ongoing reward-seeking behavioral states but does not prompt re-engagement. We find no evidence for similar tonic activity fluctuations in ventral tegmental area (VTA) dopamine neurons. Our findings implicate the LHb as a key mediator of disengagement from reward-seeking behavior in multiple contexts and argue against the idea that the LHb contributes to decisions solely by signaling aversion.

neuroscience↗

bioRxiv2018

Exploratory noise governs both flexibility and spontaneous errors and is regulated by cocaine

In many cognitive processes, lapses (spontaneous errors) are attributed to nuisance processes like sensorimotor noise or disengagement. However, some lapses could also be caused by exploratory noise: behavioral randomness that facilitates learning in changing environments. If so, strategic processes would need only up-regulate (rather than generate) exploration to adapt to a changing environment. This view predicts that lapse rates should be correlated with flexibility because they share a common cause. We report that when macaques performed a set-shifting task, lapse rates were negatively correlated with perseverative error frequency. Furthermore, chronic exposure to cocaine, which impairs cognitive flexibility, increased perseverative errors, but, surprisingly, improved overall performance by reducing lapse rates. We reconcile these results with a model in which cocaine decreased exploration by deepening attractor basins corresponding to rules. These results support the idea that exploratory noise contributes to lapses, meaning that it affects rule-based decision-making even when it has no strategic value.

neuroscience↗