Biology subjects

Gacoin, M.

Publications and source records attributed to Gacoin, M..

5 recordsLinked to original sources

bioRxiv2026

α-synuclein pathology drives multi-scale reorganization of fronto-limbic networks and cognitive flexibility in the common marmoset

Understanding how -synuclein misfolding and spreading affect brain systems is central to synucleinopathy research, yet evidence from primate models remains limited. Here, we combined histology, awake structural MRI, awake resting-state fMRI, regional homogeneity, actimetry and touchscreen behavioral testing to longitudinally track the consequences of striatal -synuclein seeding in the common marmoset. Phosphorylated -synuclein inclusions were detected from 2 months post-injection and spread progressively to distributed cortical and subcortical regions bilaterally, accompanied by regionally specific structural atrophy. Functional imaging revealed widespread disruption of large-scale networks, particularly within fronto-limbic circuits, alongside reductions in local functional coherence. Despite the absence of overt motor or sleep deficits, animals exhibited a selective impairment in cognitive flexibility, with preserved learning and task engagement. These findings indicate that striatal -synuclein seeding induces a multi-scale reorganization of brain networks preferentially affecting circuits supporting cognitive flexibility and limbic processing, establishing a primate platform for studying early stages of synucleinopathy.

animal behavior and cognition↗

bioRxiv2022

Fluoxetine degrades luminance perceptual thresholds while enhancing motivation and reward sensitivity

Selective serotonin reuptake inhibitors (SSRIs) increase serotonin activity in the brain. While they are mostly known for their antidepressant properties, they have been shown to improve visual functions in amblyopia and impact cognitive functions ranging from attention to motivation and sensitivity to reward. Yet, a clear understanding of the specific action of serotonin to each of bottom-up sensory and top-down cognitive control components and their interaction is still missing. To address this question, we characterize, in two adult macaques, the behavioral effects of fluoxetine, a specific SSRI, on visual perception under varying bottom-up (luminosity, distractors) and top-down (uncertainty, reward biases) constraints while they are performing three different visual tasks. We first manipulate target luminosity in a visual detection task, and we show that fluoxetine degrades luminance perceptual thresholds. We then use a target detection task in the presence of spatial distractors, and we show that under fluoxetine, monkeys display both more liberal responses as well as a degraded perceptual spatial resolution. In a last target selection task, involving free choice in the presence of reward biases, we show that monkeys display an increased sensitivity to reward outcome under fluoxetine. In addition, we report that monkeys produce, under fluoxetine, more trials and less aborts, increased pupil size, shorter blink durations, as well as task-dependent changes in reaction times. Overall, while low level vision appears to be degraded by fluoxetine, performance in the visual tasks are maintained under fluoxetine due to enhanced top-down control based on task outcome and reward maximization.

neuroscience↗

bioRxiv2022

Macaque amygdala, claustrum and pulvinar support the cross-modal association of social audio-visual stimuli based on meaning

Social communication draws on several cognitive functions such as perception, emotion recognition and attention. In a previous study, we demonstrated that macaques associate audiovisual information when processing their species-specific communicative signals. Specifically, cortical activation is inhibited when there is a mismatch between vocalisations and social visual information whereas activation is enhanced in the lateral sulcus, superior temporal sulcus as well as a larger network composed of early visual and prefrontal areas when vocalisations and social visual information match. Here, we use a similar task and functional magnetic resonance imaging to assess the role of subcortical structures. We identify three subcortical regions involved in audio-visual processing of species-specific communicative signal: the amygdala, the claustrum and the pulvinar. Like the cortex, these subcortical structures are not activated when there is a mismatch between visual and acoustic information. In contrast, the amygdala and claustrum are activated by visual, auditory congruent and audio-visual stimulations. The pulvinar responds in a task-dependent manner, along a specific spatial sensory gradient. Anterior pulvinar responds to auditory stimuli, medial pulvinar is activated by auditory, audio-visual and visual stimuli and the dorsal lateral pulvinar only responds to visual stimuli in a pure visual task. The medial pulvinar and the amygdala are the only subcortical structures integrating audio-visual social stimuli. We propose that these three structures belong to a multisensory network that modulates the perception of visual socioemotional information and vocalizations as a function of the relevance of the stimuli in the social context. Significance StatementUnderstanding and correctly associating socioemotional information across sensory modalities, such that happy faces predict laughter and escape scenes screams, is essential when living in complex social groups. Using functional magnetic imaging in the awake macaque, we identify three subcortical structures - amygdala, claustrum and pulvinar - that only respond to auditory information that matches the ongoing visual socioemotional context, such as hearing positively valenced coo calls and seeing positively valenced grooming monkeys. We additionally describe task-dependent activations in the pulvinar, organizing along a specific spatial sensory gradient, supporting its role as a network regulator.

neuroscience↗

bioRxiv2021

Neural correlates of audio-visual integration of socially meaningful information in macaque monkeys

Social interactions rely on the ability to interpret semantic and emotional information, often from multiple sensory modalities. In human and nonhuman primates, both the auditory and visual modalities are used to generate and interpret communicative signals. In individuals with autism, not only are there deficits in social communication, but in the integration of audio-visual information. At present, we know little about the neural mechanisms that subserve the interpretation of complex social events, including the audio-visual integration that is often required with accompanying communicative signals. Based on heart rate estimates and fMRI in two macaque monkeys (Macaca mulatta), we show that individuals systematically associate affiliative facial expressions or social scenes with corresponding affiliative vocalizations, aggressive facial expressions or social scenes with corresponding aggressive vocalizations and escape visual scenes with scream vocalizations. In contrast, vocalizations that are incompatible with the visual information are fully suppressed, suggesting top-down regulation over the processing of sensory input. The process of binding audio-visual semantic and contextual information relies on a core functional network involving the superior temporal sulcus (STS) and lateral sulcus (LS). Peak activations in both sulci co-localize with face or voice patches that have been previously described. While all of these regions of interest (ROIs) respond to both auditory and visual information, LS ROIs have a preference for auditory and audio-visual congruent stimuli while STS ROIs equally respond to auditory, visual and audio-visual congruent stimuli. To further specify the cortical network involved in the control of this semantic association, we performed a whole brain gPPI functional connectivity analysis on the LS and STS cumulated ROIs. This gPPI analysis highlights a functional network connected to the LS and STS, involving the anterior cingulate cortex (ACC), area 46 in the dorsolateral prefrontal cortex (DLPFC), the orbitofrontal cortex (OFC), the intraparietal sulcus (IPS), the insular cortex and subcortically, the amygdala and the hippocampus. Comparing human and macaque results, we propose that the integration of audio-visual information for congruent, meaningful social events involves homologous neural circuitry, specifically, an emotional network composed of the STS, LS, ACC, OFC, and limbic areas, including the amygdala, and an attentional network including the STS, LS, IPS and DLPFC. As such, these networks are critical to the amodal representation of social meaning, thereby providing an explanation for some of deficits observed in autism.

neuroscience↗

bioRxiv2020

Automated video-based heart rate tracking for the anesthetized and behaving monkey

Background Heart rate is extremely valuable in the study of complex behaviours and their physiological correlates in non-human primates. However, collecting this information is often challenging, involving either invasive implants or tedious behavioural training.New Method In the present study, we implement a Eulerian Video Magnification (EVM) heart tracking method in the macaque monkey combined with wavelet transform. This is based on a measure of image to image fluctuations in skin reflectance due to changes in blood influx.Results We show a strong temporal coherence and amplitude match between EVM-based heart tracking and ground truth ECG, from both color (RGB) and infrared (IR) videos, in anesthetized macaques, to a level comparable to what can be achieved in humans. We further show that this method allows to identify consistent heart rate changes following the presentation of conspecific emotional voices or faces.Comparison with Existing Method(s) Eulerian Video Magnification (EVM) is used to extract heart rate in humans but has never been applied to non-human primates. Video photoplethysmography allows to extract awake macaques heart rate from RGB videos. In contrast, our method allows to extract awake macaques heart rate from both RGB and IR videos and is particularly resilient to the head motion that can be observed in awake behaving monkeys.Conclusions Overall, we believe that this method can be generalized as a tool to track heart rate of the awake behaving monkey, for ethological, behavioural, neuroscience or welfare purposes.HighlightsHeart rate varies during complex non-human primate (NHP) behaviour and cognition.We apply Eulerian Video Magnification to track NHP heart rate (EVM-HR).EVM-HR can be used with RGB & IR videos, and anesthetized or awake NHPs.NHP EVM-HR vary with emotional content of presented stimuli.EVM-HR is of interest to ethology, behavioural, neuroscience & welfare purposes.Competing Interest StatementThe authors have declared no competing interest.View Full Text

animal behavior and cognition↗