Biology subjects

Decramer, T.

Publications and source records attributed to Decramer, T..

8 recordsLinked to original sources

bioRxiv2025

An intracortical brain-machine interface based on macaque ventral premotor activity

The majority of brain-machine interface (BMI) studies have focused on decoding intended movements based on neural activity of primary motor (M1) and dorsal premotor cortex (PMd). The ventral premotor cortex (PMv), and more specifically area F5c, has been implicated in object grasping and action observation, and may represent an alternative for motor BMI control due to its phasic modulation during action observation. Using chronically implanted Utah arrays in F5c, PMd, and M1 in two male macaques, we compared the efficacy of controlling a motor BMI based on neural activity of each area. PMv decoding reached similar or even higher success rates than M1 and PMd in a 2D cursor control task, especially when controlling for the number of motion selective channels that were used by the decoder. We found similar results during a 2D robot avatar control task in a simulated 3D environment. At both the multi-unit and the population level, neural responses were highly similar during the training phase (passive observation of cursor movements) and the online decoding phase, and only a small subset of neurons modulated its selectivity for the direction of motion. Thus, ventral premotor area F5c may represent an alternative for online motor BMI control. Significance statementWe present the first study on online cursor and robot avatar control using neural activity of ventral premotor cortical area F5c. Known for decades for the presence of mirror neurons, which are active during both action execution and action observation, area F5c can support online BMI control with performance comparable to that of dorsal premotor and primary motor cortex. The population dynamics in all three areas were highly similar between the training phase and the online decoding phase.

neuroscience↗

bioRxiv2025

Action observation responses in macaque frontal cortex

Neurons that are active during action execution and action observation (i.e. Action Observation/Execution Neurons, AOENs) are distributed across the brain in a network of parietal, motor, and prefrontal areas. In a previous study, we showed that most AOENs in ventral premotor area F5c, where they were discovered three decades ago, responded in a highly phasic way during the observation of a grasping action, did not require the perception of causality or a meaningful action, and even responded to static frames of the action videos. To assess whether these characteristics are shared with AOENs in other areas of the AOE network, we performed the first large-scale neural recordings during action execution and action observation in multiple frontal areas including dorsal premotor (PMd) area F2, primary motor (M1) cortex, ventral premotor area F5p, frontal eye field (FEF) and 45B. In all areas, AOENs displayed highly phasic responses during specific epochs of the action video and strong responses to simple movements of an object, similar to F5c. In addition, the population dynamics in PMv, PMd and M1 showed a shared representation between action execution and action observation, with an overlap that was as large as the overlap between action execution and passive viewing of simple translation movements. These results pose important constraints on the interpretation of action observation responses in frontal cortical areas.

neuroscience↗

bioRxiv2025

An intracortical brain-computer interface for navigation in virtual reality in macaque monkeys

We present an innovative intracortical Brain-Computer Interface (BCI) to bridge the gap between laboratory settings and real-world applications. This BCI approach introduces three key advancements. First, we utilized neural signals from three macaque brain regions - primary motor, dorsal and ventral premotor cortex - enabling precise and flexible decoding of real-time three-dimensional (3D) sphere/avatar velocities. Second, we developed a realistic, immersive 3D virtual reality setup with dynamic camera tracking, allowing continuous navigation and obstacle avoidance that closely mimic real-world scenarios. Finally, our BCI approach is very well suited for use by paralyzed patients, featuring a brief passive fixation without overt movements and closed-loop operation without retraining of the decoder during online decoding, relying on the users neural plasticity and the decoders robust generalization across tasks. Our BCI adapted to different environments, targets, and obstacles, illustrating its potential to substantially enhance the quality of life for paralyzed patients by enabling natural, reliable and flexible control in complex settings.

neuroscience↗

bioRxiv2024

Fine-grained neural coding of bodies and body parts in human visual cortex

The visual image of a human body provides a valuable source of socially relevant information. However, our understanding of the neuronal mechanisms underlying body perception in humans remains limited given the spatiotemporal constraints of functional imaging. Here we recorded multi-unit spiking activity in two neurosurgical patients in or near the extrastriate body area (EBA), a critical region for body perception. Our recordings revealed a strong preference for human bodies over a large range of control stimuli. Notably, this preference was driven by a distinct selectivity for body parts. Moreover, the observed body selectivity generalized to non-photographic depictions of bodies such as silhouettes and stick figures. Overall, our study provides an unprecedented access into the representation of bodies in the human visual cortex to bridge the gap between human neuroimaging and macaque electrophysiology studies, and form a solid basis for computational models of human body processing.

neuroscience↗

bioRxiv2023

Visual selectivity and motor role of action observation/execution neurons in macaque ventral premotor cortex

Neurons responding during action execution and action observation were discovered in the ventral premotor cortex three decades ago. However, neither the minimum visual features nor the motor involvement of Action Observation/Execution Neurons (AOENs) have been revealed at present. We investigated the minimal visual stimulus for activation and the involvement in motor behavior of AOENs in ventral premotor area F5c of four macaques. The large majority of AOENs showed highly phasic responses during the action videos, and also responded to an abstract shape moving towards but not interacting with an object, even when the shape moved on a scrambled background, implying that most AOENs in F5c do not require the perception of causality or a meaningful action. Additionally, electrical microstimulation of AOEN sites invariably elicited motor responses and frequently interfered with visually guided object grasping. Our findings suggest that an important role of F5c AOENs in visuomotor control during object grasping.

neuroscience↗

bioRxiv2020

Face neurons in human visual cortex

The exquisite capacity of primates to detect and recognize faces is crucial for social interactions. Although disentangling the neural basis of human face recognition remains a key goal in neuroscience, direct evidence at the single-neuron level is virtually nonexistent. We recorded from face-selective neurons in human visual cortex, in a region characterized by functional magnetic resonance imaging (fMRI) activations for faces compared to objects (i.e. the occipital face area, OFA). The majority of visually responsive neurons in this fMRI activation showed strong selectivity at short latencies for faces compared to objects. Feature scrambled faces and face-like objects could also drive these neurons, suggesting that the OFA is not tightly-tuned to the visual attributes that typically define whole human faces. These single-cell recordings within the human face processing system provide vital experimental evidence linking previous imaging studies in humans and invasive studies in animal models.

neuroscience↗

bioRxiv2020

Temporal dynamics of neural activity in macaque frontal cortex assessed with large-scale recordings

We make eye movements to objects before grasping these objects, and the gaze direction generally indicates where the object will be grasped. Hence, the brain has to coordinate eye-, arm- and hand movements. We performed large-scale recordings (more than 2000 responsive sites) in frontal cortex of monkeys during a saccade-reach-grasp task. When an object appeared in peripheral vision, the first burst of activity emerged in prearcuate areas (the FEF and area 45B), followed by dorsal and ventral premotor cortex, and a buildup of activity in primary motor cortex. After the saccade, prearcuate activity remained elevated while primary motor and premotor activity rose in anticipation of the upcoming arm and hand movement. Some premotor and prearcuate sites were equally active when the object appeared in peripheral vision and at the fovea, suggesting a role in eye-hand coordination. Thus, a large part of lateral frontal cortex is active during a saccade-reach-grasp task.

neuroscience↗

bioRxiv2019

Single-cell selectivity and functional architecture of human lateral occipital complex.

The human lateral occipital complex (LOC) is more strongly activated by images of objects compared to scrambled controls, but detailed information at the neuronal level is currently lacking. We recorded with microelectrode arrays in the LOC of two patients, and obtained highly selective single-unit, multi-unit and high-gamma responses to images of objects. Contrary to predictions derived from functional imaging studies, all neuronal properties indicated that the subsector of LOC we recorded from occupies an unexpectedly high position in the hierarchy of visual areas. Notably, the response latencies of LOC neurons were long, the shape selectivity was spatially clustered, LOC receptive fields were large and bilateral, and a number of LOC neurons exhibited 3D-structure selectivity (a preference for convex or concave stimuli), which are all properties typical of end-stage ventral stream areas. Thus, our results challenge prevailing ideas about the position of the LOC in the hierarchy of visual areas.

neuroscience↗