Biology subjects

Townsend, E. S.

Publications and source records attributed to Townsend, E. S..

3 recordsLinked to original sources

bioRxiv2025

Phasic dopamine encodes persistent attraction to reward cues

Reward-predictive cues can become attractive themselves due to incentive salience attribution. This manifests as persistent engagement with cues, known as sign-tracking. Cue-evoked phasic dopamine in the nucleus accumbens core (NAc) is critical for sign-tracking and cue-evoked reward craving, yet is also known to follow learning rules requiring outcome value updating. Would cue-evoked dopamine track incentive salience persistence, or change in accord with reward value alteration while failing to encode persistent behaviors? We assessed NAc dopamine activity using fiber photometry in sign-tracking rats during an omission task, in which physical cue interaction cancels reward. Animals adapted to reward loss while maintaining non-physical cue interaction reflective of persistent incentive salience. Cue-evoked dopamine remained unchanged during omission, mirroring robust incentive salience but not behavioral adaptations occurring with learning. In contrast, outcome-related dopamine reflected reward gain or loss. Therefore, cue-related dopamine encodes persistence of cue value, independent of outcome-related dopamine signals tracking reward occurrence.

neuroscience↗

bioRxiv2024

Habit learning shapes activity dynamics in the central nucleus of the amygdala

As animals perform instrumental tasks, they may develop a habit response with extended experience. Habits are automatic, inflexible, outcome value insensitive behaviors that are regulated by a network of brain regions including the central nucleus of the amygdala (CeA). Prior work has demonstrated that the CeA governs motivational pursuit and is necessary for habit formation. However, the behavioral features that CeA neurons encode in habit formation remain relatively unknown. To address this, we first used male and female Long-Evans rats to quantify CeA cFos expression after performance of a maze task. There, we found that animals with extended training show elevated cFos expression. Then, we implanted animals with drivable silicon probes to record in-vivo single unit electrophysiological activity from the CeA as animals developed habit responding on the maze. We observed significant activity during outcome consumption late in training while also observing elevated unit activity when animals consumed outcomes of larger magnitudes. Outcome related activity did not persist during probe tests following outcome devaluation, despite animals continuing to perform the task. Together, these data add to growing evidence that suggests that the CeA is involved in motivational processes that contribute to the development of habit formation.

neuroscience↗

bioRxiv2022

Nucleus accumbens acetylcholine receptors modulate the balance of flexible and inflexible cue-directed motivation

Sign-tracking is a conditioned response where animals interact with reward-predictive cues and can be used as a means to approximate a cues motivational value. The nucleus accumbens core (NAc) has been highly implicated in mediating the sign-tracking response. Additionally, acetylcholine (ACh) transmission throughout the striatum broadly has been attributed to both incentive motivation and behavioral flexibility. Here, we show that sign-tracking responses are indeed flexible in the face of a contingency change in the form of an omission schedule, and that this flexibility is mediated by NAc ACh. Using behavioral and pharmacological methods, we show that blockade of NAc nicotinic receptors (nAChRs) augmented sign-tracking persistence, while blockade of muscarinic receptors (mAChRs) enhanced response flexibility following introduction of the omission schedule. Further, we detail how mAChR or nAChR antagonism impacted the microstructure of sign-tracking responses. These results indicate that NAc ACh receptors have opposing roles in the regulation of sign-tracking response flexibility without altering the motivational value of the cue.

neuroscience↗