Biology subjects

Ramirez, L. A.

Publications and source records attributed to Ramirez, L. A..

3 recordsLinked to original sources

bioRxiv2026

Functional bipartition of medial prefrontal cortex into salience detection and movement gain

Reward prediction error (RPE) is a key function putatively realized by brain-wide neural states to drive learning and adaptive responding. The medial prefrontal cortex (mPFC) is among the many areas canonically implicated in RPE computation. Yet, whether mPFC RPE processing differs as a function of valence, value, and sign is not well-understood. Here, we performed in vivo mPFC calcium imaging in male and female rats engaged in an appetitive or aversive Pavlovian task designed to elicit RPE, along with continuous, unbiased behavioral monitoring. We found that short-latency bulk mPFC activity reports salience independent of valence, value, or RPE. Surprisingly, as subsequently validated with in vivo bidirectional optogenetics, we show that salience-null mPFC activity modulates generalized movement in a valence- and task-agnostic fashion. Together, these results challenge the pervasive notion of a unitary, region-wide representation of cognitive processes, including RPE signaling, by bulk mPFC activity, and instead, support a functional bipartition schema combining reactive detection of integrated salience and dynamic modulation of movement gain.

neuroscience↗

bioRxiv2023

Attenuated incubation of ethanol-induced conditioned taste aversion in a model of dependence

RationalePreclinical studies report attenuated ethanol-induced conditioned taste aversion (CTA) following chronic ethanol exposure, suggesting that tolerance develops to the aversive properties of ethanol. However, these studies are confounded by pre-exposure to the unconditioned stimulus (US; ethanol), which is well known to hinder conditioning. ObjectivesThis study was designed to determine whether chronic ethanol exposure produces tolerance to the aversive properties of ethanol in the absence of a US pre-exposure confound. MethodsCTA was performed in adult male and female Long-Evans rats by pairing 0.1% ingested saccharin with an intraperitoneal injection of ethanol (1.5 or 2.0 g/kg) or saline. Rats were then rendered ethanol dependent using chronic intermittent ethanol (CIE) vapor exposure. Controls were exposed to room air (AIR). The effect of chronic ethanol on CTA expression and reconditioning were examined following vapor exposure. ResultsPrior to vapor exposure, both sexes developed CTA to a comparable degree with 2.0 g/kg producing greater CTA than 1.5 g/kg ethanol. Following vapor exposure, AIR controls exhibited an increase in CTA magnitude compared to pre-vapor levels. This effect was absent in CIE-exposed rats. These group differences were eliminated upon re-conditioning after vapor exposure. ConclusionsThese data suggest that chronic ethanol does not facilitate tolerance to the aversive properties of ethanol but rather, attenuates incubation of ethanol-induced CTA. Loss of CTA incubation suggests that CIE exposure disrupts circuits encoding aversion.

neuroscience↗

bioRxiv2023

A translational rodent model of individual differences in sensitivity to the aversive properties of ethanol

BackgroundA strong relationship exists between individual sensitivity to the aversive properties of ethanol and risk for alcohol use disorder (AUD). Despite this, our understanding of the neurobiological mechanisms underlying subjective response to ethanol is relatively poor. A major contributor to this is the absence of preclinical models that enable exploration of this individual variability similar to studies performed in humans. MethodsAdult male and female Long-Evans rats were trained to associate a novel tastant (saccharin) with acute exposure to either saline or ethanol (1.5 g/kg or 2.0 g/kg i.p.) over three conditioning days using a standard conditioned taste aversion (CTA) procedure. Variability in sensitivity to ethanol-induced CTA was phenotypically characterized using a median split across the populations studied. ResultsWhen examining group averages, both male and female rats that had saccharin paired with either dose of ethanol exhibited reduced saccharin intake relative to saline controls of ethanol-induced CTA. Examination of individual data revealed a bimodal distribution of responses uncovering two distinct phenotypes present in both sexes. CTA-sensitive rats exhibited a rapid and progressive reduction in saccharin intake with each successive ethanol pairing. In contrast, saccharin intake was unchanged or maintained after an initial decrease from baseline levels in CTA-resistant rats. While CTA magnitude was similar between male and female CTA-sensitive rats, CTA-resistant females were more resistant to the development of ethanol-induced CTA than their male counterparts. Phenotypic differences were not driven by differences in baseline saccharin intake. CTA sensitivity correlated with behavioral signs of intoxication in only a subset of rats. ConclusionsThese data parallel work in humans by revealing individual differences in sensitivity to the aversive properties of ethanol that emerge immediately after initial exposure to ethanol in both sexes. This model can be leveraged in future studies to investigate the neurobiological mechanisms that confer risk for AUD.

neuroscience↗