Ejaculation latency determines susceptibility to stress in the male rat.

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.

Cortical functionality during reversal learning on a decision-making task in young men.

The evaluation of external and internal stimuli permits the ongoing actualization of choice-related information and, thus, the association between stimuli and outcomes. This process is essential to decision-making as it allows constant adaptation to environmental changes in order to maximize gains and minimize losses. Reversal learning paradigms are used to study this process, which has been associated with prefrontal cortex activity (frontopolar, dorsolateral) in conjunction with posterior areas (parietal, temporal), due to their participation in integrating and processing the stimuli-reward relation. The aim of this study was to assess the cortical functionality associated with reversal learning during the decision-making process. The EEG activity of 22 young men was recorded while performing a decision-making task in a reversal learning condition compared to an initial learning condition. EEG data were analyzed during evaluation of the stimuli, before motor execution (formation of preferences), and during task feedback (outcome evaluation). The formation of preferences stage was characterized by a higher correlation of the alpha2 band between the parietal cortices. In the feedback stage of the reversal learning condition, a higher absolute power of the theta band in the left dorsolateral (F3), and a lower correlation of the alpha1 band between the right frontopolar and dorsolateral (Fp2-F4), as well as between the right frontopolar and temporal (Fp2-T4), were observed. The data obtained show that the EEG activity of the areas recorded changed in the evaluation of the stimuli information in the reversal learning condition during a decision-making task.

Effect of reward and punishment on no-risk decision-making in young men: An EEG study.

Decision-making is a process that allows adapting behavior in response to feedback to achieve a goal. Previous studies have suggested that the cerebral cortex shows different activation patterns in response to feedback. However, the effects of reward and punishment on learning contexts and decision-making are not clear. Thus, this experiment compared the effects of reward and punishment on behavior and the electroencephalographic activity of cortical areas related to decision-making in a no-risk context. Twenty healthy males were asked to perform a decision-making task under two conditions in which the goal was to finish in the shortest time possible. In the reward condition, the more points the participant accumulated the sooner the task ended, while in the punishment condition, the more points accumulated the longer the task lasted. Lower reaction times were found in the reward condition, characterized by a higher absolute power of the slow bands in almost all the cortices recorded. Changes in the interhemispheric correlation were also obtained in the comparison of the two feedback conditions. Results suggest that changes in the type of feedback affect cortical functionality and behavioral execution during decision-making, with the reward being related to a quick emotional response strategy and punishment associated with slower and, likely, more reasoned responses.

Temporal division of the decision-making process: An EEG study.

Decision-making is a process that allows individuals to choose an option or alternative in order to maximize a subjective gain or achieve a set goal by evaluating and establishing a preference based on contextual and internal information. Ernst and Paulus proposed a three-stage temporal division of this process: 1) the assessment and formation of preferences among possible options; 2) the selection and execution of an action; and 3) the experience or evaluation of an outcome. Each stage involves the participation of several brain regions, including the prefrontal, parietal, and temporal cortices. There are reports of distinct functionalities of these cortices for each stage of decision-making, but those studies focus on individual stages and do not provide any direct comparisons among them. Therefore, using a task that allows the clear temporal separation of the three stages of decision-making, we characterized the electroencephalographic activity (EEG) of those cortices in 30 healthy right-handed men during preference changes that occurred while performing a decision-making task. As the trials progressed, the preference for the stimulus shifted towards maximizing gains on the task. Forty trials sufficed to maintain these behavioral changes. Specific EEG patterns for each stage of decision-making were obtained, and it was possible to associate them with the cognitive processes involved in each one. These EEG data support the temporal division of the decision-making process proposed by Ernest and Paulus and show that the task designed could be a useful tool for determining behavioral and cerebral changes associated with stimuli preference during decision-making.

Topographic distribution of the EEG ad hoc broad bands during sleep and wakefulness in the spider monkey (Ateles Geoffroyi).

There is evidence that research on sleep among New World monkeys may provide important knowledge related to the evolution of sleep more broadly in the primate order. Digital electroencephalographic (EEG) analyses provide essential knowledge on sleep in the spider monkey. Recently, specific EEG bands related to sleep in these animals have been obtained using principal component analysis, but the exact spatio-temporal distribution of these EEG bands in this species has not yet been analyzed. This study determined the topographic distribution of the EEG spectral power of ad hoc broad bands during rapid eye movement sleep, nonrapid eye movement sleep, and wakefulness. Superficial EEG activity was obtained from the occipital, frontal, and central areas of six young adult male monkeys housed in a laboratory. During wakefulness, occipital areas showed high absolute power in the 1-3, 3-12, and 11-30 Hz ranges, while during nonrapid eye movement 1 sleep the highest absolute power was in the 13-30 Hz range. During nonrapid eye movement 3 sleep, frontal and central areas showed a high absolute power in the 18-19 Hz range. Finally, the right central area showed a high absolute power in the 20-30 Hz range during rapid eye movement sleep. This topographic distribution of EEG bands could represent the brain organization required for arousal and mnemonic processing during sleep in the spider monkey.

Annual changes in the copulatory behavior of male rats maintained under constant laboratory conditions.

The objective of the present study was to evaluate the sexual behavior of male rats kept under constant laboratory conditions for one entire year. A total of 213 sexually-inexperienced, male Wistar rats were maintained in controlled environmental conditions from birth. Depending the month in which they reached the age 3-month-old, the male rats were divided into 12 groups, one for each month of the year, and their sexual behavior was evaluated. Records of their sexual behavior were made from 09:00 to 11:00 hrs am. The following parameters were recorded: mount (latency and number), intromission (latency and number), ejaculation latency, and intromission rate. During the months of March, June, July and September, the rats showed lower mount and intromission latencies than in January, February, April, May and October-to-December. Similarly, in March, June, July and August they had higher copulatory efficiency than in January, February, April and December. Results suggest that male rats exposed to controlled environmental conditions could have endogenous mechanisms that regulate sexual behavior but are independent of seasonal environmental signals. The annual variability in the sexual behavior of male rats maintained under constant laboratory conditions should be considered when planning research and experiments.

Modelo animal de motivación y activación sexual: efectos del alcohol / Animal Model of Sexual Motivation and Arousal: Effects of Alcohol

Resumen La motivación y la activación sexual son dos procesos semi-independientes fundamentales para la ejecución de la conducta sexual. Empleando a la rata macho Wistar como modelo animal, se determinó el efecto de diferentes dosis de alcohol (0.75 g/kg; 1.0 g/kg; 1.25 g/kg etanol), sobre el acicalamiento genital, los toques de narina (índices de motivación sexual) y las erecciones peneanas sin contacto (índices de activación sexual). Dosis altas y moderadas de alcohol provocaron un efecto deletéreo sobre ambos procesos, mientras que dosis bajas facilitaron la activación sexual. Los resultados de este trabajo confirman que la motivación y activación sexual son dos procesos semi-independientes y muestran que el alcohol ejerce un efecto diferencial sobre cada uno de ellos.

Abstract Sexual motivation and arousal are two semi-independent processes that are fundamental to the performance of sexual behavior. In this study, male Wistar rats were used as an animal model to determine the effects of different doses of alcohol (0.75, 1.0 and 1.25 g/kg ethanol) on genital-grooming and nose-touching (two indices of sexual motivation), and non-contact penile erections (an index of sexual arousal). The moderate and high doses of alcohol had deleterious effects on both processes, while the low dose, in contrast, facilitated sexual activation. The results of this study confirm that sexual motivation and arousal are two semi-independent processes, and show that alcohol exerts differential effects on each one.

Effects of inactivation of the ventral tegmental area on prefronto-accumbens activity and sexual motivation in male rats.

Sexual motivation requires the processing of sexual stimuli. The prefrontal cortex (PFC) and nucleus accumbens (NAcc) receive dopaminergic innervation from the ventral tegmental area (VTA). Both structures participate in processing stimuli, and their adequate functioning is modulated by dopamine and other neurotransmitters. This study was designed to determine the effect of inactivation of the VTA on sexual motivation, relative power (RP) and electroencephalographic (EEG) correlation of the PFC and NAcc in male rats. A total of 20 rats implanted with electrodes in the left medial prefrontal cortex (mPFC) and NAcc, and with bilateral cannulae in the VTA, were divided into two groups of 10 rats each, one injected with tetrodotoxin (TTX), the other with a vehicle solution (VEH). EEGs from the mPFC and NAcc were recorded during the awake-quiet state in the presence of either a receptive or non-receptive female. The TTX group showed a lower preference for the receptive female accompanied by a lower RP of the 8-13 and 14-30 Hz bands in the mPFC. Also, in the presence of the receptive female, the TTX group had a lower RP of the 8-13 Hz band in the NAcc, but a higher prefronto-accumbens correlation in the same band. These results provide evidence that VTA activity is necessary for the adequate functioning of the mPFC and NAcc and, therefore, also for the adequate processing of sexually-relevant stimuli that allows the induction and maintenance of sexual motivation in male rats.