Control of protein intake is essential for numerous biological processes as several amino acids cannot be synthesized de novo, however, its neurobiological substrates are still poorly understood. In the present study, we combined in vivo fiber photometry with nutrient-conditioned flavor in a rat model of protein appetite to record neuronal activity in the VTA, a central brain region for the control of food-related processes. In adult male rats, protein restriction increased preference for casein (protein) over maltodextrin (carbohydrate). Moreover, protein consumption was associated with a greater VTA response, relative to carbohydrate. After initial nutrient preference, a switch from a normal balanced diet to protein restriction induced rapid development of protein preference but required extensive exposure to macronutrient solutions to induce elevated VTA responses to casein. Furthermore, prior protein restriction induced long-lasting food preference and VTA responses. This study reveals that VTA circuit...

Negah Rahmati, Kieran P. Normoyle, Joseph Glykys, Volodymyr I. Dzhala, Kyle P. Lillis, et al. (see pages [4957–4975][1]) GABAergic receptors form the cornerstone of inhibitory synaptic signaling in the brain. Classically, ionotropic GABAA receptors pass inward chloride-dominated currents,

There is a major debate regarding the function of the thalamus: does the thalamus solely gate the transmission of information or is it actively involved in processing information? [Sherman and Guillery (2006)][1] argued that thalamic nuclei function as bidirectional relays for the flow of

Nociceptive stimuli disrupt sleep, but may, or may not, entail an arousal. While arousal reactions go along with the activation of a widespread cortical network, the factors enabling such activation remain unknown. Here we used intracranial EEG in humans to test the relation between the cortical activity immediately preceding a noxious stimulus and the capacity of such a stimulus to trigger arousal. Intracranial EEG signals were analyzed during all-night sleep in 14 epileptic patients (4 women), who received laser stimuli slightly above their individual pain threshold. During 5 s preceding each stimulus, the functional correlation (spectral phase-coherence) between the main spinothalamic sensory area (posterior insula) and 12 other brain regions, grouped in four networks, as well as their spectral contents, were contrasted according to the presence of a stimulus-induced arousal, and then fed into a logistic regression model to assess their predictive value. Enhanced prestimulus phase-coherence between the ...

Associating natural rewards with predictive environmental cues is crucial for survival. Dopamine (DA) neurons of the ventral tegmental area (VTA) are thought to play a crucial role in this process by encoding reward prediction errors (RPEs) that have been hypothesized to play a role in associative learning. However, it is unclear whether this signal is still necessary after animals have acquired a cue-reward association. In order to investigate this, we trained mice to learn a Pavlovian cue-reward association. After learning, mice show robust anticipatory and consummatory licking behavior. As expected, calcium activity of VTA DA neurons goes up for cue presentation as well as reward delivery. Optogenetic inhibition during the moment of reward delivery disrupts learned behavior, even in the continued presence of reward. This effect is more pronounced over trials and persists on the next training day. Moreover, outside of the task licking behavior and locomotion are unaffected. Similarly to inhibitions durin...

The overexpression of calcineurin leads to astrocyte hyperactivation, neuronal death, and inflammation, which are characteristics often associated with pathologic aging and Alzheimer's disease. In this study, we tested the hypothesis that tacrolimus, a calcineurin inhibitor, prevents age-associated microstructural atrophy, which we measured using higher-order diffusion MRI, in the middle-aged beagle brain ( n = 30, male and female). We find that tacrolimus reduces hippocampal ( p = 0.001) and parahippocampal ( p = 0.002) neurite density index, as well as protects against an age-associated increase in the parahippocampal ( p = 0.007) orientation dispersion index. Tacrolimus also protects against an age-related decrease in fractional anisotropy in the prefrontal cortex ( p < 0.0001). We also show that these microstructural alterations precede cognitive decline and gross atrophy. These results support the idea that calcineurin inhibitors may have the potential to prevent aging-related pathology if administere...

Forrest Gump or The Matrix ? Preference-based decisions are subjective and entail self-reflection. However, these self-related features are unaccounted for by known neural mechanisms of valuation and choice. Self-related processes have been linked to a basic interoceptive biological mechanism, the neural monitoring of heartbeats, in particular in ventromedial prefrontal cortex (vmPFC), a region also involved in value encoding. We thus hypothesized a functional coupling between the neural monitoring of heartbeats and the precision of value encoding in vmPFC. Human participants of both sexes were presented with pairs of movie titles. They indicated either which movie they preferred or performed a control objective visual discrimination that did not require self-reflection. Using magnetoencephalography, we measured heartbeat-evoked responses (HERs) before option presentation and confirmed that HERs in vmPFC were larger when preparing for the subjective, self-related task. We retrieved the expected cortical va...

In humans, impaired response inhibition is characteristic of a wide range of psychiatric diseases and of normal aging. It is hypothesized that the right inferior frontal cortex (rIFC) plays a key role by inhibiting the motor cortex via the basal ganglia. The electroencephalography (EEG)-derived β-rhythm (15–29 Hz) is thought to reflect communication within this network, with increased right frontal β-power often observed before successful response inhibition. Recent literature suggests that averaging spectral power obscures the transient, burst-like nature of β-activity. There is evidence that the rate of β-bursts following a Stop signal is higher when a motor response is successfully inhibited. However, other characteristics of β-burst events, and their topographical properties, have not yet been examined. Here, we used a large human (male and female) EEG Stop Signal task (SST) dataset ( n = 218) to examine averaged normalized β-power, β-burst rate, and β-burst “volume” (which we defined as burst duration...

Everyday decision-making commonly involves assigning values to complex objects with multiple value-relevant attributes. Drawing on object recognition theories, we hypothesized two routes to multiattribute evaluation: assessing the value of the whole object based on holistic attribute configuration or summing individual attribute values. In two samples of healthy human male and female participants undergoing eye tracking and functional magnetic resonance imaging (fMRI) while evaluating novel pseudo objects, we found evidence for both forms of evaluation. Fixations to and transitions between attributes differed systematically when the value of pseudo objects was associated with individual attributes or attribute configurations. Ventromedial prefrontal cortex (vmPFC) and perirhinal cortex were engaged when configural processing was required. These results converge with our recent findings that individuals with vmPFC lesions were impaired in decisions requiring configural evaluation but not when evaluating the...

Developmental, cellular, and subcellular variations in the direction of neuronal Cl– currents elicited by GABAA receptor activation have been frequently reported. We found a corresponding variance in the GABAA receptor reversal potential (EGABA) for synapses originating from individual interneurons onto a single pyramidal cell. These findings suggest a similar heterogeneity in the cytoplasmic intracellular concentration of chloride ([Cl–]i) in individual dendrites. We determined [Cl–]i in the murine hippocampus and cerebral cortex of both sexes by (1) two-photon imaging of the Cl–-sensitive, ratiometric fluorescent protein SuperClomeleon; (2) Fluorescence Lifetime IMaging (FLIM) of the Cl–-sensitive fluorophore MEQ (6-methoxy- N -ethylquinolinium); and (3) electrophysiological measurements of EGABA by pressure application of GABA and RuBi-GABA uncaging. Fluorometric and electrophysiological estimates of local [Cl–]i were highly correlated. [Cl–]i microdomains persisted after pharmacological inhibition of c...