Behavioral Neuroscience

Variability in odor hedonic perception: A challenge for neurosensory and behavioral research.
Odor hedonic perception (pleasant/unpleasant character) is considered to be the first and one of the most important dimensions in olfaction and is known to be highly variable and dependent on several factors related to the stimulus, individual characteristics, and context. Although numerous experimental studies have been published on this topic, there is no comprehensive general review on the variability in odor hedonic perception. Therefore, the aim of this article was to describe and detail all the factors involved in the variability in odor hedonic perception. Stimulus properties-related variability includes the concentration/intensity and the physicochemical properties. Individual-related variability includes sex, age, and physiological state characteristics, while context-related variability involves factors associated with the stimulation context, such as stimulation pathway, exposure frequency, verbal influences, cross-modal associations, hedonic contrast, and cultural background. Subsequently, a section is devoted to the brain processing of odor hedonicity, although its role in odor hedonic variability is largely unknown. Finally, the article discusses the relationship between the hedonic qualities of odors and the resulting behavioral responses in both animals and humans. (PsycInfo Database Record (c) 2024 APA, all rights reserved)
N-tert-butoxycarbonyl-methylenedioxymethamphetamine, an methylenedioxymethamphetamine derivative, exhibits rewarding and reinforcing effects by increasing dopamine levels.
An N-protected methylenedioxymethamphetamine (MDMA), N-tert-butoxycarbonyl-3,4-methylenedioxymethamphetamine (t-BOC-3,4-MDMA), contains tert-butoxycarbonyl and can remain undetected in the illicit drug market. It is a new type of precursor substance that is not a chemical intermediate and can be converted into a controlled substance, MDMA, by deprotection of the N-tert-butoxycarbonyl group. Categorization of this chemical into a precursor or psychotropic substance is an issue because it is an unprecedented precursor that could have misuse potential. Although MDMA causes rewarding and reinforcing effect through dopaminergic transmission, the misuse potential of t-BOC-3,4-MDMA has not yet been characterized. Here, we aim to evaluate the misuse potential of t-BOC-3,4-MDMA. The response to the drug at a dose of 5 mg/kg was determined by a climbing test, and its rewarding and reinforcing properties were assessed through conditioned place preference and self-administration tests. In the conditioned place preference test, intraperitoneal administration of t-BOC-3,4-MDMA (5 mg/kg) significantly altered place preference in mice. In the self-administration models, t-BOC-3,4-MDMA induced drug-taking behavior at the dose of 0.5 mg/kg/infusion (intravenous) during 2 hr sessions under fixed-ratio schedules in mice. In addition, microdialysis experiments verified that t-BOC-3,4-MDMA impacted the dopamine levels of the brain (striatum) of rats. These experimental results indicate that t-BOC-3,4-MDMA has a potential for misuse. (PsycInfo Database Record (c) 2024 APA, all rights reserved)
Sex differences in behavior and glutamic acid decarboxylase in Long Evans rats after prolonged social isolation beginning in adolescence.
Social isolation can have long-term effects on brain development and behavior and increases the risk of developing clinical conditions, including anxiety disorders. One modulator of the stress response is gamma-aminobutyric acid, an inhibitory neurotransmitter synthesized by glutamic acid decarboxylase (GAD). This study examined sex differences in behavior and GAD expression following prolonged social isolation beginning in adolescence in Long Evans rats. Males and females were equally divided into group-housed (GH) and socially isolated conditions on Postnatal Day 28 (n = 8 per group). Beginning 5 weeks later, tests were conducted for anxietylike behaviors (open-field test and elevated plus maze), social interactions (sociability test), and spatial memory (novel object location). Sex differences in behavior were observed, with GH females showing fewer anxietylike behaviors in the open-field test and elevated plus maze and spending more time with objects (sociability task) compared to GH males. Isolation had no effect on males but increased anxiety and reduced neophilic measures in females, removing sex differences. On the sociability task, all groups spent more time with novel rats compared to objects, suggesting social interest was retained after isolation. In the hippocampus, isolation reduced GAD in both sexes, and sex differences were seen (F > M). However, no group differences in behavior were observed in the hippocampal-dependent novel object location task. Our findings suggest that prolonged social isolation beginning in adolescence is anxiogenic for female Long Evans rats. Furthermore, sex and housing impact hippocampal GABA-ergic activity, which may have important implications in the treatment of anxiety disorders. (PsycInfo Database Record (c) 2024 APA, all rights reserved)
Electrophysiological and hemodynamic mechanisms underlying load modulations in visuospatial working memory: A functional near-infrared spectroscopy (fNIRS) and electroencephalogram (EEG) study.
The n-back task has been widely used to study working memory. Previous studies investigating the electrophysiological (electroencephalogram [EEG]) and hemodynamic correlates (functional near-infrared spectroscopy [fNIRS]) of the n-back task have been generally based on verbal stimuli and only investigated EEG frequency bands. We simultaneously acquired the EEG and fNIRS in 35 participants (16 males; age = 26.4 ± 4.3 years; educational attainment = 18 ± 2 years) during a visuospatial n-back task. The task encompassed a control condition and a low (requiring to recall one previous stimulus) and a high (requiring to recall two previous stimuli) working memory load experimental conditions. Accuracy decreased and reaction times slowed in the high compared to both low load and control conditions. Regarding EEG, P3a showed higher amplitude in the experimental conditions compared to the control one, and P3b exhibited higher amplitude in the low compared to the high load condition. Regarding fNIRS, the high load condition showed higher deoxygenated hemoglobin compared to the control one. Moreover, the central frontopolar cortex showed higher activation compared with the left frontal cortex. Our study showed that working memory load during a visuospatial n-back task influenced behavioral and electrophysiological indices. Even if the load effect was only observed for deoxygenated hemoglobin on hemodynamic data, this was in line with previous studies and coherent with its electrophysiological correlates. Thus, our study confirms that EEG and fNIRS can be successfully used in multimodal acquisitions, but also highlights that future studies are needed to develop a novel version of the task. (PsycInfo Database Record (c) 2024 APA, all rights reserved)
Brain electrical patterns associated with pleasure and emotion induced by tonal and atonal music.
Several studies in the last 40 years have used electroencephalography (EEG) to recognize patterns of brain electrical activity correlated with emotions evoked by various stimuli. For example, the frontal alpha and theta asymmetry models to distinguish musical emotions and musical pleasure, respectively. Since these studies have used mainly tonal music, in this study, we decided to incorporate both tonal (n = 8) and atonal (n = 8) musical stimuli to observe the subjective and electrophysiological responses associated with valence, arousal, pleasure, and familiarity, from 25 nonmusician Mexican adults (10 females, 15 males; M = 37.8 years old, SD = 15.1). Our results showed that atonal music was perceived as less familiar and pleasurable than tonal music, according to the average subjective ratings. Interestingly, greater right hemispheric activity (alpha suppression) was associated with atonal music listening. Additionally, there was an increase of theta power at the right frontal cortex (F4) correlated with a decrease of pleasure ratings, in line with the frontal theta asymmetry (FTA) model. Finally, according to the model of frontal alpha asymmetry (FAA) to distinguish musical emotions, activation (alpha suppression) of the left frontal cortex (F3) was correlated with greater valence and arousal—that is, joyful music. (PsycInfo Database Record (c) 2024 APA, all rights reserved)
Impact of supplementation with omega-3 fatty acids after maternal dietary deficiency on adolescent anxiety and microglial morphology.
Dietary maternal deficiency in omega-3 polyunsaturated fatty acids (n-3 PUFA) is a potential risk factor for the development of anxiety and other mood disorders in children and adolescents. Here, we used a previously characterized maternal n-3 PUFA dietary deficiency model in rats to determine the impact of postweaning supplementation on adolescent anxiety-like behaviors. We focused on two models of anxiety: innate anxiety tested by the elevated plus maze and a novel operant model of learned anxiety where animals learn that actions may be associated with a variable probability of harm. Given that recent basic and clinical studies have associated anxiety and other adverse effects of n-3 PUFA deficiency on inflammatory processes and microglial structure and function, we also assessed the impact of our dietary deficiency model and supplementation on adolescent microglial morphology in multiple brain regions. We found that the male and female adolescent n-3 PUFA-deficient groups exhibit increased innate anxiety, but only females showed enhanced learned anxiety. Supplementation after weaning did not significantly affect innate anxiety but ameliorated learned anxiety in females. Thus, the beneficial effects of supplementation on adolescent anxiety may be sex-specific and depend on the type of anxiety. We also found that n-3 PUFA deficiency influences microglia function in adolescents in the amygdala and nigrostriatal, but not mesolimbic, brain regions. Collectively, these data suggest that while n-3 PUFA dietary supplementation may be effective in reducing adolescent anxiety, this effect is context-, sex-, and brain network-specific. (PsycInfo Database Record (c) 2024 APA, all rights reserved)
Renewal of conditioned fear in male and female rats.
Pavlovian extinction reduces the performance of conditioned responses and occurs when the conditioned stimulus (CS) is repeatedly presented in the absence of the unconditioned stimulus (US). However, when the CS is experienced in a context that is different from the extinction context, there is a recovery of the conditioned response, a phenomenon known as renewal. There is some evidence that the renewal of appetitive conditioning is influenced by sex, with females failing to exhibit renewed responding. Further, there is recent evidence that renewal of fear might also not occur in female rats. In both appetitive and fear preparations, the lack of renewal in females has been postulated to be related to cycling ovarian hormones. Therefore, in Experiments 1 and 2, we directly compared fear renewal in males and females (Experiment 1) as well as ovariectomized (OVX) females (Experiment 2) when conditioning occurred in Context A, extinction in B, and testing in A (ABA renewal). Experiments 3 and 4 examined renewal when conditioning and extinction occurred in A and testing occurred in B (AAB renewal). In all experiments, renewal was not significantly different between male and female rats. Further, in Experiments 2 and 4, renewal did not differ between males, intact females, and OVX females. Additionally, in each experiment, there was no evidence that context excitation and/or inhibition contributed to renewal; instead suggesting that renewal was controlled by an occasion-setting mechanism. Overall, these results suggest little evidence for the role of sex in renewal of conditioned freezing and also indicate that cycling ovarian hormones have little role in the strength of renewal in female rats. (PsycInfo Database Record (c) 2024 APA, all rights reserved)

Behavioral Neuroscience - Vol 138, Iss 5