Behavioral/Cognitive Anticipation of Appetitive Operant Action Induces Sustained Dopamine Release in the Nucleus Accumbens The mesolimbic dopamine system is implicated in signaling reward-related information as well as in actions that generate rewarding outcomes. These implications are commonly investigated in either pavlovian or operant reinforcement paradigms, where only the latter requires instrumental action. To parse contributions of reward- and action-related information to dopamine signals, we directly compared the two paradigms: male rats underwent either pavlovian or operant conditioning while dopamine release was measured in the nucleus accumbens, a brain region central for processing this information. Task conditions were identical with the exception of the operant-lever response requirement. Rats in both groups released the same quantity of dopamine at the onset of the reward-predictive cue. However, only the operant-conditioning group showed a subsequent, sustained plateau in dopamine concentration throughout the entire 5 s cue presentation (preceding the required action). This dopamine ramp was unaffected by probabilistic reward delivery, occurred exclusively before operant actions, and was not related to task performance or task acquisition as it persisted throughout the 2 week daily behavioral training. I
Understanding the neural architecture of emotion regulation by comparing two different strategies: A meta-analytic approach The space surrounding the body (i.e., peripersonal space, PPS) has a crucial impact on individuals’ interaction with the environment. Research showed that interaction within the PPS increases individuals’ behavioral and neural responses. Furthermore, individuals’ empathy is affected by the distance between them and the observed stimuli. This study investigated empathic responses to painfully stimulated or gently touched faces presented within the PPS depending on the presence vs. absence of a transparent barrier erected to prevent interaction. To this aim, participants had to determine whether faces were painfully stimulated or gently touched while their electroencephalographic (EEG) signals were recorded Brain activity (i.e., event-related potentials [ERPs], source activations) was separately compared for the two types of stimuli (i.e., gently touched vs. painfully stimulated faces) across two barrier conditions: (a) no barrier between participants and the screen (i.e., no-barrier) and (b) a plexiglass barrier erected between participants and the screen (i.e., barrier).
Listening Effort Contributes to Cortical Tracking of Speech in Adverse Listening Conditions Cortical tracking of speech is vital for speech segmentation and is linked to speech intelligibility. However, there is no clear consensus as to whether reduced intelligibility leads to a decrease or an increase in cortical speech tracking, warranting further investigation of the factors influencing this relationship. One such factor is listening effort, defined as the cognitive resources necessary for speech comprehension, and reported to have a strong negative correlation with speech intelligibility. Yet, no studies have examined the relationship between speech intelligibility, listening effort, and cortical tracking of speech. The aim of the present study was thus to examine these factors in quiet and distinct adverse listening conditions.
Human-Like Modulation Sensitivity Emerging through Optimization to Natural Sound Recognition Natural sounds contain rich patterns of amplitude modulation (AM), which is one of the essential sound dimensions for auditory perception. The sensitivity of human hearing to AM measured by psychophysics takes diverse forms depending on the experimental conditions. Here, we address with a single framework the questions of why such patterns of AM sensitivity have emerged in the human auditory system and how they are realized by our neural mechanisms. Assuming that optimization for natural sound recognition has taken place during human evolution and development, we examined its effect on the formation of AM sensitivity by optimizing a computational model, specifically, a multilayer neural network, for natural sound (namely, everyday sounds and speech sounds) recognition and simulating psychophysical experiments in which the AM sensitivity of the model was assessed.
Generating parallel representations of position and identity in the olfactory system In Drosophila, a dedicated olfactory channel senses a male pheromone, cis-vaccenyl acetate (cVA), promoting female courtship while repelling males. Here, we show that separate cVA-processing streams extract qualitative and positional information. cVA sensory neurons respond to concentration differences in a 5-mm range around a male. Second-order projection neurons encode the angular position of a male by detecting inter-antennal differences in cVA concentration, which are amplified through contralateral inhibition. At the third circuit layer, we identify 47 cell types with diverse input-output connectivity. One population responds tonically to male flies, a second is tuned to olfactory looming, while a third integrates cVA and taste to coincidentally promote female mating. The separation of olfactory features resembles the mammalian what and where visual streams; together with multisensory integration, this enables behavioral responses appropriate to specific ethological contexts.
Antihypertensives in dementia: Good or bad for the brain? Should we treat high blood pressure in people with dementia with antihypertensives? To answer this question, we must weigh the benefits and risks of antihypertensive treatment in this population. In the absence of clinical trial evidence, we pose that the benefits and risks of treatment in people with dementia do not markedly differ from those in healthy peers. The majority (>80%) of people with dementia are relatively old (age >75 years), and have a high prevalence of cardiovascular comorbidity, including hypertension (∼50%).1 There is a reduced risk of cardiovascular disease or mortality associated with antihypertensive treatment (Supplementary reference [SR] #1), even in people aged >80 years (SR #2), many of whom may be at risk of dementia. Moreover, intensive treatment (i.e. systolic blood pressure target <140 mmHg) is superior to a more conservative approach, provided that the life expectancy at the onset of treatment is ≥3 years.2 However, this is based on trials in healthy older individuals, which questions the applicability in vulnerable patient groups, e.g. patients with dementia (SR #3).
Molecular changes in hippocampal energy metabolism in mice selectively bred for extremes in stress reactivity: Relevance of mitochondrial dysfunction for affective disorders Affective disorders, such as major depression, are frequently associated with metabolic disturbances involving mitochondria. Although dysregulation of the hypothalamic–pituitary–adrenal (HPA) axis is known to alter energy metabolism, the precise mechanisms linking stress and metabolic disturbances are not sufficiently understood. We used a mouse model of affective disorders to investigate the impact of a genetic predisposition for extremes in stress reactivity on behavioural and metabolic phenotypes as well as energy metabolism. Adult males of three independent mouse lines selectively bred for high, intermediate or low HPA axis reactivity were tested for exploratory and locomotor activity as well as stress-coping behaviour. Additionally, basal and stress-induced plasma corticosterone levels, body weight, food intake and body composition were measured.
Sex and estrous cycle stage shape left-right asymmetry in chronic hippocampal seizures in mice Lateralization of hippocampal function is indicated by varied outcomes of patients with neurological disorders that selectively affect one hemisphere of this structure, such as temporal lobe epilepsy (TLE). The intrahippocampal kainic acid (IHKA) injection model of TLE allows for targeted damage to the left or right hippocampus, enabling systematic comparison of effects of left-right asymmetry on seizure and non-seizure outcomes. Although varying non-seizure phenotypic outcomes based on injection side in dorsal hippocampus were recently evaluated in this model, differences in chronic seizure patterns in left- (IHKA-L) vs. right-injected (IHKA-R) IHKA animals have yet to be evaluated. Here, we assessed hippocampal seizure incidence in male and female IHKA-L and IHKA-R mice. Females displayed increased electrographic seizure activity compared to males at both 2 and 4 months post-injection.