Behavioral neuroscience最新文献

The ability to remember sequences of events is fundamental to episodic memory. While rodent studies have examined sex and estrous cycle in episodic-like spatial memory tasks, little is known about these biological variables in memory for sequences of events that depend on representations of temporal context. We investigated the role of sex and estrous cycle in rats during training and testing stages of a cross-species validated sequence memory task (Jayachandran et al., 2019). Rats were trained on a two four-odor sequence memory task delivered on opposite ends of a linear track. Training occurred in six successive stages starting with learning to poke in a nose-port for ≥ 1.2 s; eventually demonstrating sequence memory by holding their nose in the port ≥ 1 s for in-sequence odors and < 1 s for out-of-sequence odors. Performance was analyzed across sex and estrous cycle (proestrus, estrus, metestrus, and diestrus), the latter being determined by cellular composition of a daily vaginal lavage. We found no evidence of sex differences in asymptotic sequence memory performance, similar to humans performing an analogous task (Reeders et al., 2021). Likewise, no differences in sequence memory performance were found across the estrous cycle. Some caveats are that males acquired out-of-sequence trials faster during training with a 3-odor sequence, but this apparent advantage did not carry over to the 4-odor sequence. Additionally, males had shorter poke times overall which seem consistent with a decreased overall response inhibition because they occurred regardless of sequence demands. Together, these results suggest sex and estrous cycle are not major factors in sequence memory capacities. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

The involvement of the cerebellum in suprasecond interval timing (i.e., timing in the seconds to minutes range) is controversial. A limited amount of evidence from humans, nonhuman primates, and rodents has shown that the lateral cerebellum, including the lateral cerebellar nucleus (LCN), may be necessary for successful suprasecond timing performance. However, many existing studies have pitfalls, such as limited timing outcome measures and confounded task demands. In addition, many existing studies relied on well-trained subjects. This approach may be a drawback, as the cerebellum is hypothesized to carry out ongoing error correction to limit timing variability. By using only experienced subjects, past timing studies may have missed a critical window of cerebellar involvement. In the experiments described here, we pharmacologically inactivated the rat LCN across three different peak interval timing tasks. We structured our tasks to address past confounds, collect timing variability measures, and characterize performance during target duration acquisition. Across these various tasks, we did not find strong support for cerebellar involvement in suprasecond interval timing. Our findings support the existing distinction of the cerebellum as a subsecond interval timing brain region. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

The ability to predict and prepare for near- and far-future events is among the most fundamental computations the brain performs. Because of the importance of time for prediction and sensorimotor processing, the brain has evolved multiple mechanisms to tell and encode time across scales ranging from microseconds to days and beyond. Converging experimental and computational data indicate that, on the scale of seconds, timing relies on diverse neural mechanisms distributed across different brain areas. Among the different encoding mechanisms on the scale of seconds, we distinguish between neural population clocks and ramping activity as distinct strategies to encode time. One instance of neural population clocks, neural sequences, represents in some ways an optimal and flexible dynamic regime for the encoding of time. Specifically, neural sequences comprise a high-dimensional representation that can be used by downstream areas to flexibly generate arbitrarily simple and complex output patterns using biologically plausible learning rules. We propose that high-level integration areas may use high-dimensional dynamics such as neural sequences to encode time, providing downstream areas information to build low-dimensional ramp-like activity that can drive movements and temporal expectation. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Animals routinely learn to associate environmental stimuli and self-generated actions with their outcomes such as rewards. One of the most popular theoretical models of such learning is the reinforcement learning (RL) framework. The simplest form of RL, model-free RL, is widely applied to explain animal behavior in numerous neuroscientific studies. More complex RL versions assume that animals build and store an explicit model of the world in memory. To apply these approaches to explain animal behavior, typical neuroscientific RL models make implicit assumptions about how real animals represent the passage of time. In this perspective, I explicitly list these assumptions and show that they have several problematic implications. I hope that the explicit discussion of these problems encourages the field to seriously examine the assumptions underlying timing and reinforcement learning. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Studies of instrumental responding often include the delivery of a cue that is coincident with the delivery of the reinforcer. One purpose of this is for the cue to be removed during extinction and then presented later to assess whether responding returns (cue-induced reinstatement). In two experiments, we examined the effects of having a cue associated with reinforcement present or absent during extinction. In Experiment 1, the cue was associated with fixed ratio responding for intravenous cocaine or food pellets in one context (Context A), followed by extinction in another context (Context B), where responding produced the cue in one group but did not produce the cue in the other group. Afterward, contextual renewal was assessed with and without the cue in Context A. During extinction, a cue previously associated with cocaine reinforcement caused an increase in responding initially (an extinction burst) and throughout 16 2-hr extinction sessions, as well as weakened contextual renewal when animals were tested with the cue in Context A. In contrast, there were few detectable effects of the cue on extinction and contextual renewal when food pellets were the reinforcer. In Experiment 2, effects of a cue during extinction of progressive ratio responding were revealed with food pellets when animals showed weakened responding on the initial trials of postextinction reacquisition sessions. These experiments demonstrate that the presence of a cue associated with reinforcement during extinction may prolong responding in the short term while creating a more persistent form of extinction that resists relapse. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Hormonal contraceptives (HCs) containing synthetic ovarian hormones are commonly used among reproductive aged women; HCs alter the physiological state of the user by interfering with endogenous hormone concentrations and their actions on the reproductive tract. As ovarian hormones modulate the incidence of substance abuse disorders in women, this experiment explores how modulating female rat ovarian hormonal states with an HC containing the synthetic progestin levonorgestrel influences measures of drug preference and responsivity. First, rats underwent food-light Pavlovian conditioning to measure conditioned orienting, a known predictor of amphetamine (AMP) place preference. Then, rats were conditioned and tested for AMP place preference with either an HC implant or during estrous cycle stages associated with opposing ovarian hormone levels, that is, proestrus (P) or metestrus/diestrus (M/D), while recording ultrasonic vocalizations (USVs) as an index of he donic drug responsivity. Because of dopamine's (DA's) role in reward learning and memory, DA cell number and activity were examined using tyrosine hydroxylase and FOS immunohistochemistry after a final AMP challenge. Conditioned orienting did not differ between cycling and HC-implanted rats. HC rats emitted fewer USVs in response to AMP, showed marginally less AMP place preference, and had lower DA cell activity in the substantia nigra after AMP compared to P rats. M/D rats showed a similar behavioral profile and neural response as HC rats. This experiment suggests ovarian hormones affect drug preference and responsivity, while providing novel insight into how hormone-altering contraceptives may reduce these measures. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Surprising violations of outcome expectancies have long been known to enhance the associability of Pavlovian cues; that is, the rate at which the cue enters into further associations. The adaptive value of such enhancements resides in promoting new learning in the face of uncertainty. However, it is unclear whether associability enhancements reflect increased associative plasticity within a particular behavior system, or whether they can facilitate learning between a cue and any arbitrary outcome, as suggested by attentional models of conditioning. Here, we show evidence consistent with the latter hypothesis. Violating the outcome expectancies generated by a cue in an appetitive setting (feeding behavior system) facilitated subsequent learning about the cue in an aversive setting (defense behavior system). In addition to shedding light on the nature of associability enhancements, our findings offer the neuroscientist a behavioral tool to dissociate their neural substrates from those of other, behavior system- or valence-specific changes. Moreover, our results present an opportunity to utilize associability enhancements to the advantage of counterconditioning procedures in therapeutic contexts. (PsycInfo Database Record (c) 2022 APA, all rights reserved).