Topic: rhesus macaques

Recognizing others’ emotions based on facial expressions is a core component of human social interactions. Previous studies (Wang and Adolphs 2017) have suggested that autistic individuals show differences in their facial emotion recognition compared to neurotypical adults. What are the neural mechanisms that account for these observed differences? Here we lay the groundwork for a new approach combining cutting-edge computational and empirical non-human primate work to test theories of atypical facial emotion recognition in autistic adults. In a recent study, the author(s) observed that artifi

When making choices, we allocate our fixations to each contemplated option, and tend to look longer at more valued ones (1-5). The purpose of fixation during choice remains unknown. Here we examined behavioral and neural activity of rhesus macaques (Macaca mulatta) performing a two-options risky choice task in which offers occurred in sequence, each followed by a long (600 ms) blank screen delay period. As expected, we found that subjects allocated their gaze towards offer presentation locations and spent more time looking at most valuable offers; after factoring out value, we found that more

In uncertain environments, we balance exploitation and exploration: we generally exploit rewarding opportunities, but sometimes explore uncertain alternatives that could be even better. Exploration is associated with a sudden disorganization of neuronal activity patterns in the prefrontal cortex, which could be a powerful way to promote discovery and learning. Although the mechanisms behind this disorganization remain unknown, one possibility is pupil-linked neuromodulatory systems. However, it is not clear whether pupil size predicts the neural signatures of exploration, much less the sudden

Identifying situations in which exploration could be beneficial, and learning from such choices, is critical for survival in complex environments. Nonetheless, it is still unclear how animals adapt their choice strategies depending on the potential benefits of exploration and what the neural underpinning of this ability is. We thus adapted a 2-option forced-choice task in which 3 rhesus macaques made choices while the information and the feedback they received was being manipulated: (i) feedback was given about either just the chosen option or both the chosen and unchosen counterfactual option

Balancing exploration and exploitation is crucial for navigating unpredictable, ever-changing environments. Exploitation stabilizes decision-making to maximize rewards while exploration introduces variability, destabilizing behavior to search for new opportunities. Previous studies have implicated the dorsal anterior cingulate cortex (dACC) in exploratory decision-making, but also in tracking important decision-making variables like reward. Critically, the relationship between dACC and these variables remains ambiguous because neither link has been tested causally. Here, we stimulated dACC dur

When engaged with a specific task, humans and other animals occasionally make seemingly irrational decisions known as "lapses", even in static and well-learned environments. Given they serve no obvious reward-maximizing purpose, these choices are commonly attributed to disengagement, distraction or sensorimotor noise. However, "lapses" could also be related to a decision-makers' own, hidden objectives. We know, for example, that exploratory objectives can better account for lapses than undirected noise in certain models. Critically, however, there are multiple mechanisms for exploration and we

Efficient contingent learning requires actions and outcomes to be closely associated in time. Extensive prior work indicates that interaction between amygdala, frontal cortex, and striatum is critical for this type of learning. Here, we conducted neurophysiology recordings and applied computational approaches to understand how activity in this circuit varies when choice and reward are separated in time, intentionally decreasing animals’ ability to associate the two together. We trained 3 rhesus macaques to perform a probabilistic reward-learning task. In each session, animals learn the probabi

Traditionally, the processing of object motion and form has been attributed to the dorsal and ventral visual pathways, respectively. However, recent studies challenge this strict dichotomy. For example, Hong et al. (2016) demonstrated that the ventral stream represents spatial information, while Ramezanpour et al. (2024) showed that object motion could be decoded from the inferior temporal (IT) cortex. These findings prompt further exploration of how the ventral pathway supports the integration of motion and form, particularly in naturalistic environments. In our study, we aimed to investigate

It is not unusual to tacitly conflate conjectured inhibitory processes in cognition with inhibitory neural mechanisms. Here, we investigate whether resolution of memory interference, which is thought to entail cognitive inhibition, could be modulated by systemically administered GABAergic pharmacons in non-human primates.Twelve healthy adult rhesus macaques had been extensively trained in the PAL object-location working memory task on the Monkey CANTAB touchscreen test device. In each trial of the PAL task, the animals had to recall the locations of 3-7 distinct sequentially presented schemati

Hedonic overeating is usually derived from overriding homeostatic food intake (FI) and is thought to be mainly responsible for modern age obesity. Glucagon-like peptide 1 (GLP-1) is a major signal of reaching energy balance and satiety, having a major role in normal FI behaviour.We investigated the effects of the GLP-1 agonist exenatide on palatability-driven feeding regulation in adult male rhesus macaques (n=5) using a novel operant FI paradigm. In each session, one of two available food pellets with different palatability values was offered as meal in all combinations with two daily feeding

Learning information and making flexible, appropriate choices are essential in everyday life. Animal model studies indicate the mediodorsal thalamus (MD) plays an important role in learning and decision-making. It is proposed to be an active partner supporting communication between the frontal and medial temporal lobes and other subcortical structures. To understand the contribution of each brain structure, it is critical we know its function and its anatomical connectivity. The latter helps inform which cortical and subcortical structures interact and how information travels throughout the br

Social interactions in primates are possible through the ability to extract relevant information from voices, for example their identity. The anterior Temporal Voice Area (aTVA) is a region in the anterior temporal lobe of humans, macaques and marmosets specialized in the processing of voices, but the exact voice information represented by individual neurons in the aTVA remains obscure.Here we asked how aTVA neurons encode voice identity information, separating different identities and grouping together calls from a same identity. We implanted two rhesus macaques with high-density multi-electr

Cochlear Implants (CI) have been successful at restoring meaningful hearing perception in many deaf patients. However, rehabilitation for patients with damaged auditory nerves are scarce: the only alternative is the Auditory Brainstem Implant (ABI), which presents poor clinical outcomes and difficult surgical approach.Here, we propose to target the auditory cortex directly, using a soft auditory cortex implant, for hearing restoration. By leveraging microfabrication techniques, we developed soft Electrocorticography (ECoG) arrays that would conform the curvilinear surface of the cortex, suppor

Disruption in the excitatory and inhibitory (E/I) balance of cortical networks is well-characterised in age-related neurocognitive disorders (NCD), impacting functional cognitive decline. Thus, utilising non-invasive transcranial magnetic stimulation (TMS) and electroencephalography (EEG) methods, similarly applicable in both patients and translationally relevant preclinical animal models, we established baseline cortical excitability in rhesus macaques, followed by modulation of the E/I balance by diazepam (GABAA PAM).We recorded scalp-EEG from 27 electrodes by a telemetric amplifier system d

Nutrients and oral-sensory food qualities influence the subjective valuation of food. We recently showed that monkeys prefer sugar- and fat-rich foods, consistent with the integration of nutrient and oral-sensory properties into economic values to guide choice (Huang et al., 2021) and reinforcement learning (Huang & Grabenhorst, 2023). However, it is unclear how amygdala neurons, which encode subjective values during economic choice (Grabenhorst et al., 2012, Jezzini & Padoa-Schioppa, 2020), process nutrients and oral-sensory food attributes during choice. Here, we recorded the activit