Peter Janssen

KU Leuven | ku leuven · Department of Neurosciences

Background Preserved cycling capabilities in patients with Parkinson's disease, especially in those with freezing of gait are still poorly understood. Previous research with invasive local field potential recordings in the subthalamic nucleus has shown that cycling causes a stronger suppression of β oscillations compared to walking, which facilitat...

Object recognition and categorization are essential cognitive processes which engage considerable neural resources in the human ventral visual stream. However, the tuning properties of human ventral stream neurons for object shape and category are virtually unknown. We performed the first large-scale recordings of spiking activity in human Lateral...

Object recognition and categorization are essential cognitive processes which engage considerable neural resources in the human ventral visual stream. However, the tuning properties of human ventral stream neurons for object shape and category are virtually unknown. We performed the first large-scale recordings of spiking activity in human Lateral...

Objective: Basic, translational and clinical neuroscience are increasingly focusing on large-scale invasive recordings of neuronal activity. However, in large animals such as nonhuman primates and humans - in which the larger brain size with sulci and gyri imposes additional challenges compared to rodents, there is a huge unmet need to record from...

To perform real-world tasks like grasping, the primate brain has to process visual object information so that the grip aperture can be adjusted before contact with the object is made. Previous studies have demonstrated that the posterior subsector of the Anterior Intraparietal area (pAIP) is connected to frontal area 45B, and the anterior subsector...

Theta-burst transcranial magnetic stimulation (TBS) has become a standard non-invasive technique to induce offline changes in cortical excitability in human volunteers. Yet, TBS suffers from a high variability across subjects. A better knowledge about how TBS affects neural activity in vivo could uncover its mechanisms of action and ultimately allo...

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 limited. We recorded from face-selective neurons in human visual cortex in a region characterized by...

The cortical network controlling the arm and hand when grasping objects consists of several areas in parietal and frontal cortex. Recently, more anterior prefrontal areas have also been implicated in object grasping, but their exact role is currently unclear. To investigate the neuronal encoding of objects during grasping in these prefrontal region...

Efficient object grasping requires the continuous control of arm and hand movements based on visual information. Previous studies have identified a network of parietal and frontal areas that is crucial for the visual control of prehension movements. Electrical microstimulation of 3D shape-selective clusters in AIP during fMRI activates areas F5a an...

The neural mechanisms underlying the effects of continuous Theta-Burst Stimulation (cTBS) in humans are poorly understood. Animal studies can clarify the effects of cTBS on individual neurons, but behavioral evidence is necessary to demonstrate the validity of the animal model. We investigated the behavioral effect of cTBS applied over parietal cor...

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 ch...

Visual information reaches the amygdala through the various stages of the ventral visual stream. There is, however, evidence that a fast subcortical pathway for the processing of emotional visual input exists. To explore the presence of this pathway in primates, we recorded local field potentials in the amygdala of four rhesus monkeys during a pass...

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 o...

Efficient object grasping requires the continuous control of arm and hand movements based on visual information. Previous studies have identified a network of parietal and frontal areas that is crucial for the visual control of prehension movements. Electrical microstimulation of 3D shape-selective clusters in AIP during fMRI activates areas F5a an...

To perform real-world tasks like grasping, the primate brain has to process visual object information so that the grip aperture can be adjusted before contact with the object is made. Previous studies have demonstrated that the posterior subsector of the Anterior Intraparietal area (pAIP) is connected to frontal area 45B, and the anterior subsector...

[This corrects the article DOI: 10.1371/journal.pbio.3000280.].

Background: Recently, large-scale semi-chronic recording systems have been developed, unique in their capability to record simultaneously from multiple individually moveable electrodes. As these recording systems can cover a large area, knowledge of the exact location of each individual electrode is crucial. Currently, the only method of keeping t...

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 2 patients and obtained highly selective single-unit, multi-unit, and high-gamma responses to images of ob...

Transcranial magnetic stimulation (TMS) can non-invasively modulate neural activity in humans. Despite three decades of research, the spatial extent of the cortical area activated by TMS is still controversial. Moreover, how TMS interacts with task-related activity during motor behavior is unknown. Here, we applied single-pulse TMS over macaque par...

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...

The concept of functional modularity in human visual processing was proposed 25 years ago with the distinction between a ventral pathway for object recognition and a dorsal pathway for action processing. Lesions along these pathways yield selective deficits. A 15-year-old patient (MW) presented with a seizure due to a lesion in the left occipitotem...

In order to perform real-world tasks like grasping efficiently, the primate brain has to process visual object information so that the grip aperture can be adjusted before contact with the object is made. For this reason, extensive research has been conducted to assess the way in which different brain areas contribute to 3D shape perception and how...

Brain connectivity in non-human primates (NHPs) has been mainly investigated using tracer techniques and functional connectivity studies. Data on structural connections are scarce and come from diffusion tensor imaging (DTI), since gross anatomical white matter dissection studies in the NHP are lacking. The current study aims to illustrate the cour...

Nonhuman primates have proven to be a valuable animal model for exploring neuronal mechanisms of cognitive control. One important aspect of executive control is the ability to switch from one task to another, and task-switching paradigms have often been used in human volunteers to uncover the underlying neuronal processes. To date, however, no stud...

Both dorsal and ventral visual pathways harbor several areas sensitive to gradients of binocular disparity (i.e., higher-order disparity). Although a wealth of information exists about disparity processing in early visual (V1, V2, and V3) and end-stage areas, TE in the ventral stream, and the anterior intraparietal area (AIP) in the dorsal stream,...

Transcranial Magnetic Stimulation (TMS) can non-invasively modulate neural activity in humans. Despite three decades of research, the spatial extent of the cortical area activated by TMS is still controversial. Moreover, how TMS interacts with task-related activity during motor behavior is unknown. We applied single-pulse TMS over the macaque parie...

The primate dorsal visual stream processes object shape to guide actions involving an object, but the transmission of shape information beyond posterior parietal cortex remains largely unknown. To clarify the information flow between parietal and frontal cortex, we applied electrical microstimulation during functional Magnetic Resonance Imaging (fM...

Previous studies have shown that neurons in parieto-frontal areas of the macaque brain can be highly selective for real-world objects, disparity-defined curved surfaces, and images of real-world objects (with and without disparity) in a similar manner as described in the ventral visual stream. In addition, parieto-frontal areas are believed to conv...

Objective We investigated changes in the endocannabinoid system and glucose metabolism during temporal lobe epileptogenesis. Methods Because it is rarely possible to study epileptogenesis in humans, we applied the electrical amygdala kindling model in nonhuman primates to image longitudinal changes in type 1 cannabinoid receptor (CB1R) binding and...

The cortical network processing three-dimensional (3D) object structure defined by binocular disparity spans both the ventral and dorsal visual streams. However, very little is known about the neural representation of 3D structure at intermediate levels of the visual hierarchy. Here, we investigated the neural selectivity for 3D surfaces in the mac...

2nd International Brain Stimulation Conference

The division of labor between the dorsal and the ventral visual stream in the primate brain has inspired numerous studies on the visual system in humans and in nonhuman primates. However, how and under which circumstances the two visual streams interact is still poorly understood. Here we review evidence from anatomy, modelling, electrophysiology,...

The primate brain processes objects in the ventral visual pathway. One object category, faces, is processed in a hierarchical network of interconnected areas along this pathway. It remains unknown whether such an interconnected network is specific for faces or whether there are similar networks for other object classes. For example, the primate inf...

One of the most powerful forms of depth perception capitalizes on the small relative displacements, or binocular disparities, in the images projected onto each eye. The brain employs these disparities to facilitate various computations, including sensori-motor transformations (reaching, grasping), scene segmentation and object recognition. In accor...

Epileptic seizures are network-level phenomena. Hence, epilepsy may be regarded as a circuit-level disorder that cannot be understood outside this context. Better insight into the effective connectivity of the seizure onset zone and the manner in which seizure activity spreads could lead to specifically-tailored therapies for epilepsy. We applied t...

Brain areas critical for stereopsis have been investigated in non-human primates but are largely unknown in the human brain. Microelectrode recordings and functional MRI (fMRI) studies in monkeys have shown that in monkeys the inferior temporal cortex is critically involved in 3D shape categorization. Furthermore, some human fMRI studies similarly...

Combination of overlap between SPECT and EM-fMRI changes and its relation to the seizure-specific activity. This figure combines Fig. 4, Fig. 5 to indicate that most areas that are part of the conjunction between the perfusion and EM-fMRI changes (red and blue) are only a part of the perfusion changes. Therefore, most seizure-specific changes (oran...

The primate visual system consists of a ventral stream, specialized for object recognition, and a dorsal visual stream, which is crucial for spatial vision and actions. However, little is known about the interactions and information flow between these two streams. We investigated these interactions within the network processing three-dimensional (3...

Methods. A. Stimuli used in the fMRI-inactivation experiments. We used a 2x2 design with factors curvature (curved or flat) and disparity (stereo or control). Above the anaglyphs are icons illustrating the depth structures of the stimuli (red dot represents the fixation point). The control stimuli were the monocular images of the stereo stimuli pre...

Effect of CIP inactivation on percent signal change (PSC) in two paths. A. CIP-inactivation effect on PSC (curvature x disparity interaction effect) on a path drawn along the IPS (left panel) and along the ITC (right panel). Green: saline sessions; red: muscimol sessions. * = p < 0.05 uncorrected, ** = p < 0.01 uncorrected. Injection syringe indica...

Effect of CIP inactivation on PSC in the IPS. The bar graph (top panel) shows the PSC of the curvature x disparity interaction effect calculated on consecutive coronal slices from posterior (caudal IPS) to anterior (anterior IPS ROI). For every coronal slice, we considered all voxels that were significantly activated (at p < 0.05 corrected for mult...

Percent signal change for individual sessions. PSC for the contrast [CS-CC]-[FS-FC] was calculated in the functionally defined ROIs aIPS, cIPS, and AIT for each individual no-injection, saline, and muscimol session. The PSC for each muscimol session was compared with the average over all saline sessions in the same animal to check for significance;...

A. Depth structure activations in the anterior IPS in individual monkeys plotted on their average EPIs during saline (left panels) and muscimol (right panels) sessions. B. Depth structure activations in the ITC in individual monkeys plotted on their average EPIs during saline (left panels) and muscimol (right panels) sessions. C. Coronal sections d...

EM-fMRI results. A. Anatomical MRIs showing electrode locations in CIP for the two animals used (monkey M and monkey D). Below the MRIs are peristimulus-time histograms (PSTHs) of a CIP neuron (recorded at that location), which responded selectively to a planar tilted surface (top part inclined toward the observer) at different positions in depth (...

Individual data. Effect of CIP inactivation on PSC of the curvature x disparity interaction effect in eight functionally-defined ROIs (in both hemispheres) in three animals (upper panel: monkey M, middle panel: monkey S, lower panel: monkey R). Green bars: saline sessions; red bars: muscimol sessions. * = p < 0.05, ** = p < 0.01. Black lines indica...

Effect of CIP inactivation in the right hemisphere on the main effect of disparity. A. Flat map showing the fMRI activations in the main effect of stereo (all stereo conditions–all control conditions). Blue outlines: saline sessions; hot colors: muscimol sessions. B. PSC in the main effect of stereo in saline sessions (green bars) and in muscimol s...

Effect of CIP inactivation on behavior. A. Percent concave responses was plotted as a function of the percent coherence, for control (red) and muscimol (blue) sessions. Behavioral data were fitted with a logistic function. Raw values in [27], monkey_percentcorrect.xls. B. Average horizontal eye position signal (right eye only) for convex (red) and...

Visual object information is necessary for grasping. In primates, the Anterior Intraparietal area (AIP) plays an essential role in visually-guided grasping. Neurons in AIP encode features of objects, but no study has systematically investigated the receptive field (RF) of AIP neurons. We mapped the RF of posterior AIP (pAIP) neurons in the central...

The anterior intraparietal area (AIP) of rhesus monkeys is part of the dorsal visual stream and contains neurons whose visual response properties are commensurate with a role in three-dimensional (3D) shape perception. Neuronal responses in AIP signal the depth structure of disparity-defined 3D shapes, reflect the choices of monkeys while they cate...

Amygdala kindling is a widely used animal model for studying mesial temporal lobe epileptogenesis. In the macaque monkey, electrical amygdala kindling develops slowly and provides an opportunity for investigating ictal perfusion changes during epileptogenesis. Two rhesus monkeys were electrically kindled through chronically implanted electrodes in...

The primate visual system extracts object shape information for object recognition in the ventral visual stream. Recent research has demonstrated that object shape is also processed in the dorsal visual stream, which is specialized for spatial vision and the planning of actions. A number of studies have investigated the coding of 2D shape in the an...

Humans and other primates possess a unique capacity to grasp and manipulate objects skillfully, a facility pervasive in everyday life that has undoubtedly contributed to the success of our species. When we reach and grasp an object, various cortical areas in the parietal and frontal lobes work together effortlessly to analyze object shape and posit...

Previous functional magnetic resonance (fMRI) studies in humans and monkeys have demonstrated that the anterior Intraparietal Sulcus (IPS) is sensitive to the depth structure defined by binocular disparity. However, in the macaque monkey, a single large activation was measured in the anterior lateral bank of the IPS, whereas in human subjects two s...

Single neurons in the frontal eye fields (FEFs) and lateral intraparietal area (LIP) of macaques are preferentially activated by saccade- versus reach-related processes. fMRI studies focusing on saccade- and reach-specific activity in human cortex, however, provided conflicting evidence for effector specificity. To gain further insights into effect...

In this review, we discuss the impact (or lack thereof) biologically motivated vision has had on computer vision in the last decades. We then summarize a number of computer vision and robotic problems for which biological models can give indications for how these can be addressed. Then we summarize important findings about the primate’s visual syst...

Extrastriate cortical areas are frequently composed of subpopulations of neurons encoding specific features or stimuli, such as color, disparity, or faces, and patches of neurons encoding similar stimulus properties are typically embedded in interconnected networks, such as the attention or face-processing network. The goal of the current study was...

The anterior intraparietal area (AIP) of macaques contains neurons that signal the depth structure of disparity-defined 3-D shapes. Previous studies have suggested that AIP's depth information is used for sensorimotor transformations related to the efficient grasping of 3-D objects. We trained monkeys to categorize disparity-defined 3-D shapes and...

Primates use vision to guide their actions in everyday life. Visually guided object grasping is known to rely on a network of cortical areas located in the parietal and premotor cortex. We recorded in the anterior intraparietal area (AIP), an area in the dorsal visual stream that is critical for object grasping and densely connected with the premot...