Sexual experience in male rats modulates sexual motivation through learning processes that enhance responsiveness to female stimuli and facilitate copulatory behavior. These processes involve mesocorticolimbic areas such as the medial prefrontal cortex (mPFC) and nucleus accumbens (NAc). Sexual experience has been associated with changes in dendritic spine density in these regions, but it is unclear whether such modifications are modulated by re-exposure to female-derived stimuli. We explored how sexual experience and exposure to an inaccessible female stimulus interacted to modulate dendritic spine density in these two cerebral regions of male rats. Dendritic spines were analyzed after sexually-naïve and sexually-experienced males were exposed to either an ovariectomized or receptive female. Sexual experience was found to reduce copulatory latencies and was associated with increased attentional responses toward a receptive female. Under basal conditions, the sexually-experienced males showed higher total spine density in the mPFC, with a lower proportion of thin spines but a higher proportion of mushroom spines in both the mPFC and NAc. Exposure to a receptive female also induced region-specific plasticity. In the mPFC, exposure reduced total spine density and mushroom spine proportion regardless of sexual experience. In contrast, the NAc showed an interaction between sexual experience and the female stimulus characterized by changes in the proportions of thin and mushroom spines, but with no changes in total spine density. These findings suggest that sexual experience establishes a consolidated synaptic state that is modified by female stimuli, thus providing evidence of adaptive sexual motivation and behavior.

Systemic administration of NMDA induces stereotyped behavior followed frequently, but not always, by generalized epileptiform seizures. Increased NMDA activity provokes overstimulation of NMDA glutamate receptors in neurons with dendritic spines. Systemic administration of 100 mg/kg of NMDA i.p. induced stereotyped behavior in adult male rats 5-10 min post-injection. Then, the density and proportion of the various types of spines were counted in pyramidal neurons of the hippocampus and prefrontal cortex of two groups: NMDA-treated rats and a Saline control. Dendritic spine density increased in the experimental rats in both study regions, manifested in a higher proportion of stubby and wide (neckless) types. This type of spine showed a significant interaction between groups and brain structures. No changes were observed in the thin or mushroom spines. BDNF increased in the prefrontal cortex but remained unchanged in the hippocampus, suggesting that differential modulatory BDNF-mediated mechanisms are involved in synaptic plasticity in these two brain areas. The predominance of neckless (stubby, wide) spines suggests their involvement in synaptic overstimulation in both the hippocampus and prefrontal cortex. This possibility requires further research using diverse methodologies. This is the first study of the synaptic plasticity -mediated by dendritic spines- that underlie the pre-convulsive, stereotyped behavior in an experimental model based on epileptiform seizures.

Activity of the medial prefrontal cortex (mPFC) and nucleus accumbens (NAcc) during perception of sexual stimuli and states of sexual motivation are not yet well understood. This study explored the relation among electroencephalographic (EEG) activity, sexual experience, and attention in male rats during the detection of sexual stimuli while near a receptive female. Before and after three copulatory sessions until ejaculation, EEGs from the mPFC and NAcc of male rats were recorded while they were attentive to a receptive female but had no direct access to her. The sexually-experienced males displayed more attention responses and longer permanence near an inaccessible receptive female than the naïve rats. A lower power of the slow theta (4-7 Hz) band, but a higher power of the fast frequencies was observed in both the mPFC and NAcc of the sexually-experienced males in response to sexually-relevant stimuli compared to the naïve group. The correlation between the power of theta activity and attention parameters showed an inverse relation, indicating that once the males gained sexual experience, the longer duration of their nose pokes was related to a decrease in the RP of the 4-7 Hz band in both structures. It is likely that EEGs change in the theta range and fast frequences observed in the mPFC and NAcc reflect consolidation of the association between sexual stimuli and reward, thus facilitating adequate performance of the attentional and approach behaviors characteristic of sexual motivation.

OBJECTIVES:Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by amyloid-β plaque accumulation, tau pathology, and cortical atrophy, leading to widespread synaptic dysfunction and cognitive decline. Sleep disturbances are highly prevalent in AD and are thought to both reflect and exacerbate underlying neurodegenerative processes. Melatonin, an indoleamine synthesized by the pineal gland, is central to the regulation of circadian rhythms and sleep - wake cycles. In healthy individuals, melatonin enhances non-rapid eye movement (NREM) sleep and attenuates beta activity during wakefulness. In AD populations, it has been associated with improved sleep quality and potential neuroprotective effects against amyloid-related pathology. Electroencephalography (EEG) offers a non-invasive method to monitor neurophysiological changes associated with AD. Principal component analysis (PCA), a dimensionality reduction technique, enables the identification of latent neural patterns within complex EEG data. METHODS:In this preliminary study, PCA was applied to EEG recordings from eight individuals with mild-to-moderate AD during both wakefulness and sleep under placebo and melatonin conditions. EEG derivations included bipolar (F7-T3, F8-T4, F3-F4, O1-O2) and referential (C3-A1, C4-A2) configurations. RESULTS:Preliminary PCA suggests that melatonin administration may induce a stage-dependent reorganization of EEG spectral activity, characterized by a relative enhancement of slow-frequency activity and an apparent increase in spectral segregation during NREM sleep. DISCUSSION:These preliminary findings suggest that melatonin could optimize stage-specific neural dynamics, supporting its therapeutic potential in AD-related sleep disruption.

The primate order has received considerable interest in studies on lateralized behaviour due to their hemisphere specialization and potentially major implications for the evolution of the human cerebral cortex. The development of the prefrontal and association regions is required for complex behaviours, and there is evidence that some species show hemispheric specialization in the performance of executive functions. However, laterality in relation to working memory in New World monkeys has received little attention. The main aim of this study was to explore the use of the hands and the tail in spider monkeys (Ateles geoffroyi) while performing two visual-spatial delayed match-to-sample (DMTS) tasks. Eight juvenile male spider monkeys raised in outdoor rain forest enclosures were studied. They were tested on two tasks over a period of 20 days. The first DMTS task had a 15-sec delay and used two different containers to hide a reward. The second had a 60-sec delay and used four different containers. Spider monkeys showed a robust and consistent left-hand preference during both acquisition and execution of DMTS tasks, occasionally accompanied by left-side tail use. The left-hand preference provide evidence for lateralized motor control and contribute to understanding hemispheric specialization to working memory in nonhuman primates.

Obsessive-compulsive disorder (OCD) is a mental affliction characterized by compulsive behaviors often manifested in intrusive thoughts and repetitive actions. The quinpirole model has been used with rats to replicate compulsive behaviors and study the neurophysiological processes associated with this pathology. Several changes in the dendritic spines of the medial prefrontal cortex (mPFC) and dorsolateral striatum (DLS) have been related to the occurrence of compulsive behaviors. Dendritic spines regulate excitatory synaptic contacts, and their morphology is associated with various brain pathologies. The present study was designed to correlate the occurrence of compulsive behaviors (generated by administering the drug quinpirole) with the morphology of the different types of dendritic spines in the mPFC and DLS. A total of 18 male rats were used. Half were assigned to the experimental group, the other half to the control group. The former received injections of quinpirole, while the latter rats were injected with physiological saline solution, for 10 days in both cases. After the experimental treatment, the quinpirole rats exhibited all the parameters indicative of compulsive behavior and a significant correlation with the density of stubby and wide neckless spines in both the mPFC and DLS. Dendritic spines from both mPFC and DLS neurons showed plastic changes correlatively with the expression of compulsive behavior induced by quinpirole. Further studies are suggested to evaluate the involvement of glutamatergic neurotransmission in the neurobiology of OCD.

Sexual arousal (SA) is a multidimensional experience that includes cognitive, emotional, motivational and physiological components. Texts with erotic content have been used to generate a state of SA. Erotic texts often include aggressive content that has not been evaluated in relation to SA. The aim of this work was to compare cortical functionality in women when reading a sexually explicit text (SET) and a sexually explicit text with aggression (SETA). Twenty-seven women participated. The EEG activity of the frontal, temporal and parietal locations was recorded during the reading of both texts. The participants found the SET to be more pleasant than the SETA. Both texts were identified as triggers of general and SA. While reading the SETA, there was an increase in absolute power in the frontal and parietal locations, a higher intrahemispheric correlation between the left frontal and temporal locations in fast frequency bands and a greater interhemispheric correlation between the frontal locations in the delta and alpha1 bands. These findings indicate that cortical functionality during SA in women differs based on the content and context of the erotic material being read, possibly associated with mechanisms that underlie the processing and incentive value assignment of stimuli with sexual and aggressive connotations.

Since several cortical areas participate in the processing of sexual stimuli, this study characterized the electroencephalographic activity of prefrontal, temporal and parietal areas in men with different sexual orientation while observing erotic videos with homosexual (HOV) and heterosexual (HEV) content. The homosexual group presented lower absolute power of theta band in the right temporal cortex and higher right fronto-temporal correlation of beta band when observing the HOV. While the heterosexual group rated only the HEV as pleasant, also presented a higher left fronto-temporal correlation of beta band while watching the HEV, and a lower right fronto-parietal correlation of theta band during observation of the HOV. These results show a characteristic cortical functionality involved in the processing of sexually-relevant stimuli and its possible association with sexual orientation.

Breastfeeding is recognized worldwide as the best option for infant feeding. Expressing breast milk is an alternative for mothers to provide their infants all the benefits of maternal milk. During breast milk expression, mothers receive a distinct kind of sensory stimulation, because there is no direct bodily or affective interaction with their infants, many women report feeling isolated, generating a love-hate relation with pumping, and even low levels of satisfaction while expressing breast milk. While it is well known that the prefrontal, parietal, and temporal cortices play important roles in the emotional and cognitive processing of maternal stimuli, knowledge about how these cortical areas function during breastfeeding is lacking. This study was designed to characterize EEG activity in the prefrontal and parietal cortices and the affective scores of primiparous breastfeeding mothers during two conditions of milk expression: breast milk expression and direct breastfeeding. Participants reported higher valence and arousal and a pleasant state during direct breastfeeding. In the direct breastfeeding condition, both prefrontal areas showed a higher absolute power (AP) of the slow bands, with a lower AP of the alpha band in the parietal cortex. A lower correlation between frontopolar and dorsolateral areas with a higher correlation between prefrontal and parietal cortices was obtained mainly in the right hemisphere. This EEG activity could be linked to an internal state of focused attention and, simultaneously, open monitoring of the environment that suggests an integration of the motive-emotional and cognitive processes necessary for adequate mother-baby interaction during direct breastfeeding.

Introduction. Young people are highly susceptible to manifesting the various dimensions of anxiety, which have been associated with certain personality traits. Objective. To determine the association between personality traits (PT) and the dimensions of clinical anxiety (CA), trait anxiety (TA), and state anxiety (SA) in young students in the areas of health sciences in the state of Jalisco, Mexico. Method. Five hundred and twenty-one students (with an average age of 20.5 years) enrolled in psychology, nursing, and nutrition degree programs participated, 75.2% of whom were women. From Abril 2020 to May 2021, a cross-sectional design was used to virtually evaluate CA (Beck’s inventory), TA and SA (the Spielberger inventory), and PT (Eysenck’s inventory). Linear regression analysis was used to calculate correlations (R) and determination coefficients (R2) to predict the dimensions of anxiety in relation to PT. Results. 25.7% and 24.8% of participants scored for severe and moderate CA respectively, while 54.3% obtained high scores for TA and SA. For CA, the neuroticism PT yielded an R of .607 and an R2 of .367; for TA, an R of .803 and an R2 of .644; and for SA, an R of .735 and an R2 of .540. Discussion and conclusion. The high correlation between the neuroticism PT and anxiety in young people was probably exacerbated by the restrictive conditions of the COVID-19 pandemic. In young students, the neuroticism PT is a predictor for the development of various dimensions of anxiety.

Desde el nacimiento del grupo de Bioseñales (el año 1997), un grupo de aprendices de la ciencia del cerebro, hemos dedicado nuestro tiempo a desentrañar los misterios que esconden las funciones del cerebro. Después de haber escrito 19 libros científicos, decidimos aventurarnos a una nueva experiencia, escribiendo un libro dirigido a quienes tienen una curiosidad sin límites y una energía inmensa para aprender, a las mentes jóvenes, ávidas por descubrir los secretos que guarda nuestro órgano más asombroso, el cerebro. Así, surgió el presente texto, donde Lucy, una neurocientífica, realiza un fantástico viaje al cerebro para explicar a niños y niñas cómo funciona éste maravilloso órgano durante las diferentes actividades divertidas y no divertidas, así como durante los estados de tristeza, temor, agresión, aprendizaje y memoria. Este libro es una invitación a un viaje lleno de descubrimientos asombrosos; preguntas intrigantes y respuestas que, esperamos, lleven al lector a ver el mundo de una manera totalmente nueva. A lo largo de estas páginas, exploraremos juntos cómo trabaja el cerebro, cómo los pensamientos se convierten en acciones y cómo cada pequeña parte de este órgano increíble contribuye a lo que somos. Esperamos que este libro contribuirá a que los niños comprendan la relevante función del cerebro, y se despierte en ellos el interés por estudiarlo.

Sexual experience improves copulatory performance in male rats. Copulatory performance has been associated with dendritic spines density in the medial prefrontal cortex (mPFC) and nucleus accumbens (NAcc), structures involved in the processing of sexual stimuli and the manifestation of sexual behavior. Dendritic spines modulate excitatory synaptic contacts, and their morphology is associated with the ability to learn from experience. This study was designed to determine the effect of sexual experience on the density of different types or shapes of dendritic spines in the mPFC and NAcc of male rats. A total of 16 male rats were used, half of them were sexually experienced while the other half were sexually inexperienced. After three sessions of sexual interaction to ejaculation, the sexually-experienced males presented shorter mount, intromission, and ejaculation latencies. Those rats presented a higher total dendritic density in the mPFC, and a higher numerical density of thin, mushroom, stubby, and wide spines. Sexual experience also increased the numerical density of mushroom spines in the NAcc. In both the mPFC and NAcc of the sexually experienced rats, there was a lower proportional density of thin spines and a higher proportional density of mushroom spines. Results show that the improvement in copulatory efficiency resulting from prior sexual experience in male rats is associated with changes in the proportional density of thin and mushroom dendritic spines in the mPFC and NAcc. This could represent the consolidation of afferent synaptic information in these brain regions, derived from the stimulus-sexual reward association.

According to the different stages of the estrous cycle, female rats exhibit behavioral changes associated with variations in sex hormone levels that affect the functionality of certain brain regions. In this study, we characterized the attention that female rats paid to a sexually-experienced male and the degree of electroencephalographic (EEG) activation and coupling between the medial prefrontal and posterior parietal cortices during antagonistic phases of the estrous cycle (proestrus-estrus vs. diestrous). The degree of attention paid to the stimulus was measured by the number of nose pokes performed while the rats were in a sexual incentive motivation box. EEGs were recorded in two conditions: a) awake-quiet state with no male rat present; and b) awake-quiet state in the presence of a male. Only during proestrus-estrus did the females show lower latency with a higher frequency and duration of nose pokes. In both cortices, the receptive females presented higher absolute power in all EEG bands recorded in the presence of the male, regardless of the phase of the estrous cycle. They also had greater EEG coupling between the medial prefrontal and posterior parietal cortices of the left hemisphere in all EEG bands regardless of the presence of a male. The higher synchronization between prefronto-parietal areas could be associated with the greater attention paid to, and adequate processing of, the sexual stimuli emitted by the male. Hence, it is probable that manifesting the proceptivity and receptivity behaviors characteristic of the proestrus-estrus phase requires a higher functional coupling between the prefrontal and parietal cortices.

Stress induces diverse effects on sexual behavior, ranging from enhanced execution to the complete abolishment of sexual interaction. However, it is not clear whether some characteristics intrinsic to the individual that experiences stress could also explain this differential effect. This study seeks to relate sexual execution to susceptibility to stress (as post-stress sexual motivation). To this end, we designed a three-session experimental paradigm. In the first session, male rats were allowed to copulate with a female. In the second, the male rats received electric foot shocks as they attempted to approach the female. The third and final session was used to determine the effects of stress on sexual behavior by separating the rats into two groups: a motivation-impaired group (rats that did not cross to achieve copulation), and an unimpaired group (rats that did cross). Mount latency was affected immediately by stress in both groups, though only the non-crossing group presented a reduced number of copulatory events. The rats that did not cross showed slower-paced sexual execution even before stress was applied compared to the rats that crossed. These results show that rats that are more susceptible to stress present higher ejaculation latency even before the application of stress.

Major depressive disorder (MDD) is a complex illness that is arising as a growing public health concern. Although several brain areas are related to this type of disorders, at the cellular level, the parvalbumin-positive cells of the hippocampus interplay a very relevant role. They control pyramidal cell bursts, neuronal networks, basic microcircuit functions, and other complex neuronal tasks involved in mood disorders. In resistant depressions, the efficacy of current antidepressant treatments drops dramatically, so the new rapid-acting antidepressants (RAADs) are being postulated as novel treatments. Ketamine at subanesthetic doses and its derivative metabolites have been proposed as RAADs due to their rapid and sustained action by blocking N-methyl-d-aspartate (NMDA) receptors, which in turn lead to the release of brain-derived neurotrophic factor (BDNF). This mechanism produces a rapid plasticity activation mediated by neurotransmitter homeostasis, synapse recovery, and increased dendritic spines and therefore, it is a promising therapeutic approach to improve cognitive symptoms in MDD.

The study of electroencephalographic (EEG) signals in nonhuman primates has led to important discoveries in neurophysiology and sleep behavior. Several studies have analyzed digital EEG data from primate species with prehensile tails, like the spider monkey, and principal component analysis has led to the identification of new EEG bands and their spatial distribution during sleep and wakefulness in these monkeys. However, the spatial location of the EEG correlations of these new bands during the sleep-wake cycle in the spider monkey has not yet been explored. Thus, the objective of this study was to determine the spatial distribution of EEG correlations in the new bands during wakefulness, rapid eye movement (REM) sleep, and non-REM sleep in this species. EEG signals were obtained from the scalp of six monkeys housed in experimental conditions in a laboratory setting. Regarding the 1-21 Hz band, a significant correlation between left frontal and central regions was recorded during non-REM 2 sleep. In the REM sleep, a significant correlation between these cortical areas was seen in two bands: 1-3 and 3-13 Hz. This reflects a modification of the degree of coupling between the cortical areas studied, associated with the distinct stages of sleep. The intrahemispheric EEG correlation found between left perceptual and motor regions during sleep in the spider monkey could indicate activation of a neural circuit for the processing of environmental information that plays a critical role in monitoring the danger of nocturnal predation.

This study evaluates, through artificial neural network (NN) simulations, the roles of amygdala (AMG) and orbitofrontal cortex (OFC) in reversal learning as responsible for assigning and updating incentive values, respectively, by taking into account some of its physiological characteristics and its connections with mesolimbic system structures. An architecture was built which contained modules of nodes representing OFC, amygdala (AMG), ventral tegmental area (VTA) and nucleus accumbens (NACC). Simulations were based on experimental responses of rats during a discrimination and reversal learning task in a T-maze. During simulations, intact NN responded similar to control rats. OFC showed retarded encoding in afferent connections as comparing with AMG nodes and an increase in the recruitment of neural nodes during reversal tasks. Activity of neural nodes plausibly emulates reinforcer preference during discriminations and reversals in AMG, COF and NACC. All these findings were disrupted by OFC’s inactivation. NN with OFC nodes inactivated (RN), just like rats with OFC inactivated, achieved discrimination learning although its reversal was impaired. As with rats, perseveration of incorrect responses was not found because subjects stop responding after a few incorrect trials. These findings are in accordance with the hypotheses of AMG as key in encoding novel predicting-outcome cues and OFC as critical for incentive value updating and the crucial role this prefrontal region plays for correct performance in discrimination tasks.

The heuristic approach to decision-making holds that the selection process becomes more efficient when part of the information available is ignored. One element involved in selecting information is emotional valence. If emotional congruency is related to simplified decision-making strategies, then the interaction of this factor with task complexity should exist. The present study explored how factors of this nature influence decision-making efficiency. We hypothesized that emotional congruency would have a positive effect on task execution and that the magnitude of that effect would increase with greater task complexity because in that condition the amount of information to be processed is greater, meaning that a heuristic approach to the problem would be more efficient. We design a decision in browser decision-making task in which participants had to select emotional images to gain points. Depending on the correlation between emotional valence and in-task image value, we defined three emotional congruency conditions: direct, null, and inverse. Our results show that distinct types of emotional congruency have differential effects on behavior. While direct congruency-enhanced overall decision-making performance, inverse congruency interacted with task complexity to modify the pace at which task feedback affected behavior.

Pentylenetetrazol (PTZ) blocks the inhibitory action of GABA, triggering a Glu-mediated hyperexcitation of the dendritic spines in hippocampal CA1 pyramidal neurons that leads to the generation of epileptiform seizures. The aim of this work was to determine the effect of PTZ on the electrical activity of the hippocampal pyramidal neurons in male rats. Bipolar electrodes were implanted stereotaxically in the right and left hippocampal CA1 fields of adults, and PTZ (65 mg/kg) was administered i.p. Simultaneous recordings of the field activity and the firing rate (multiunitary activity, MUA) were analyzed at 10, 20, and 30 min post-administration of PTZ. Only rats that presented tonic-clonic seizures during the first 1-5 min after PTZ treatment were included in the study. The recordings of the field activity were analyzed in 4 frequency bands. In both the right and left hippocampal CA1 fields, the relative power corresponding to the slow waves (4-7 Hz) increased, while in the bands 13-30 Hz and 31-50 Hz, it decreased at 10, 20, and 30 min post-PTZ. MUA recordings were analyzed at four levels. The highest levels corresponded to larger amplitudes of the action potentials in the pyramidal neurons. The firing rates of the PTZ-treated rats did not differ from baseline but presented a significant decrement at 10, 20, and 30 min post-PTZ. The decreased firing rate of the hippocampal CA1 pyramidal neurons after PTZ treatment could be associated with plastic changes of dendritic spines along with some microenvironmental adaptations at synaptic level, after neuronal PTZ-mediated hyperexcitation.

Sexual motivation (SM) is a physiological state generated by the adequate processing of sexually-relevant stimuli. Induction and maintenance of this state requires the coordinated functioning of various cortical and subcortical areas. The medial prefrontal (mPFC, the prelimbic area in rats) and posterior parietal cortices (pPC) form an attentional network involved in processing incentive stimuli. Given that the sexual incentive stimuli emitted by a receptive female are highly relevant for the male rat, it is probable that these cortices interact functionally in processing the sexual stimuli that produce SM. Thus, the objective of this study was to characterize the cortical activation and degree of electroencephalographic coupling (coherence, hEEG) between the mPFC and pPC during a sexually-motivated state in male rats. Only rats that reached this state after 1 intromission prior to EEG recording, presented a higher frequency and duration of nose pokes, and showed higher prefronto-parietal activation and EEG synchronization while close to an inaccessible receptive female. Results show that both cortices are activated and that they are functionally coupled during the processing of sexually-relevant stimuli mainly in the right hemisphere, a key condition for inducing SM. We conclude that the attentional network made up of the prefrontal and parietal cortices participates in the adequate attention to, and processing of, sexual incentive stimuli and, hence, in inducing SM in male rats.