Investigating the Features of the M170 in Congenital Prosopagnosia

Face perception generates specific neural activity as early as 170 ms post-stimulus onset, termed the M170 when measured with Magnetoencephalography (MEG). We examined the M170 in six people with congenital prosopagnosia (CP) and 11 typical controls. Previous research indicates that there are two neural generators for the M170 (one within the right lateral occipital area - rLO and one within the right fusiform gyrus - rFG), and in the current study we explored whether these sources reflect the processing of different types of information. Individuals with CP showed face-selective M170 responses within the rLO and right rFG, which did not differ in magnitude to those of the controls. To examine possible links between neural activity and behavior we correlated the CPs' MEG activity generated within rLO and rFG with their face perception skills. The rLO-M170 correlated with holistic/configural face processing, whereas the rFG-M170 correlated with featural processing. Hence, the results of our study demonstrate that individuals with CP can show an M170 that is within the normal range, and that the M170 in the rLO and rFG are involved in different aspects of face processing

Experimental Induction of a Perceived “Telescoped” Limb Using a Full-Body Illusion

Phantom limbs refer to the sensation that an amputated or missing limb is still attached to the body. Phantom limbs may be perceived as continuous with the stump so as to resemble a normal limb, or as “telescoped” with the more distal portion of the phantom being perceived as having withdrawn within the stump. Telescoping tends to be related to increased levels of phantom pain, making it a clinically relevant phenomenon to investigate. In the current study we show that a full-body illusion can be used to induce the sensation of a telescoped limb in healthy individuals. For the induction of the full-body illusion, participants saw the body of a mannequin from a first person perspective while being subjected to synchronized visuo-tactile stimulation through stroking. Crucially, the mannequin was missing its left hand so as to resemble an amputee. By manipulating the positioning of the strokes applied to the mannequin's stump with respect to the participants’ hand we were able to evoke the sensation of the participants’ hand being located either below the stump or, more crucially, “inside” the stump, i.e., telescoped. In three separate experiments these effects were supported by complementary subjective data from questionnaires, verbally reported perceived location of the hand, and manual pointing movements indicating hand position (proprioceptive drift). Taken together our results show that healthy individuals can experience the body of an upper limb amputee as their own, and that this can be associated with telescoping sensations. This is a theoretically important observation as it shows that ownership of an entire body can be evoked in the context of gross anatomical incongruence for a single limb, and that telescoping sensations occur as a consequence of the body representation system trying to reduce this incongruence. Furthermore, the present study might provide a new platform for future studies of the relationship between telescoping and phantom pain in amputees

From Head to Toe: Evidence for Selective Brain Activation Reflecting Visual Perception of Whole Individuals

Our ability to recognize other people’s faces and bodies is crucial for our social interactions. Previous neuroimaging studies have repeatedly demonstrated the existence of brain areas that selectively respond to visually presented faces and bodies. In daily life, however, we see “whole” people and not just isolated faces and bodies, and the question remains of how information from these two categories of stimuli is integrated at a neural level. Are faces and bodies merely processed independently, or are there neural populations that actually code for whole individuals? In the current study we addressed this question using a functional magnetic resonance imaging adaptation paradigm involving the sequential presentation of visual stimuli depicting whole individuals. It is known that adaptation effects for a component of a stimulus only occur in neural populations that are sensitive to that particular component. The design of our experiment allowed us to measure adaptation effects occurring when either just the face, just the body, or both the face and the body of an individual were repeated. Crucially, we found novel evidence for the existence of neural populations in fusiform as well as extrastriate regions that showed selective adaptation for whole individuals, which could not be merely explained by the sum of adaptation for face and body respectively. The functional specificity of these neural populations is likely to support fast and accurate recognition and integration of information conveyed by both faces and bodies. Hence, they can be assumed to play an important role for identity as well as emotion recognition in everyday life

Movement-Based Embodied Contemplative Practices: Definitions and Paradigms

Over the past decades, cognitive neuroscience has witnessed a shift from predominantly disembodied and computational views of the mind, to more embodied and situated views of the mind. These postulate that mental functions cannot be fully understood without reference to the physical body and the environment in which they are experienced. Within the field of contemplative science, the directing of attention to bodily sensations has so far mainly been studied in the context of seated meditation and mindfulness practices. However, the cultivation of interoceptive, proprioceptive and kinesthetic awareness is also said to lie at the core of many movement-based contemplative practices such as Yoga, Qigong, and Tai Chi. In addition, it likely plays a key role in the efficacy of modern somatic therapeutic techniques such as the Feldenkrais Method and the Alexander Technique. In the current paper we examine how these practices are grounded in the concepts of embodiment, movement and contemplation, as we look at them primarily through the lens of an enactive approach to cognition. Throughout, we point to a series of challenges that arise when Western scientists study practices that are based on a non-dualistic view of mind and body

Neural correlates of the rubber hand illusion in amputees: a report of two cases

One of the current challenges in the field of advanced prosthetics is the development of artificial limbs that provide the user with detailed sensory feedback. Sensory feedback from our limbs is not only important for proprioceptive awareness and motor control, but also essential for providing us with a feeling of ownership or simply put, the sensation that our limbs actually belong to ourselves. The strong link between sensory feedback and ownership has been repeatedly demonstrated with the so-called rubber hand illusion (RHI), during which individuals are induced with the illusory sensation that an artificial hand is their own. In healthy participants, this occurs via integration of visual and tactile signals, which is primarily supported by multisensory regions in premotor and intraparietal cortices. Here, we describe a functional magnetic resonance imaging (fMRI) study with two upper limb amputees, showing for the first time that the same brain regions underlie ownership sensations of an artificial hand in this population. Albeit preliminary, these findings are interesting from both a theoretical as well as a clinical point of view. From a theoretical perspective, they imply that even years after the amputation, a few seconds of synchronous visuotactile stimulation are sufficient to activate hand-centered multisensory integration mechanisms. From a clinical perspective, they show that a very basic sensation of touch from an artificial hand can be obtained by simple but precisely targeted stimulation of the stump, and suggest that a similar mechanism implemented in prosthetic hands would greatly facilitate ownership sensations and in turn, acceptance of the prosthesis

“Pulling Telescoped Phantoms Out of the Stump”: Manipulating the Perceived Position of Phantom Limbs Using a Full-Body Illusion

Most amputees experience phantom limbs, or the sensation that their amputated limb is still attached to the body. Phantom limbs can be perceived in the location previously occupied by the intact limb, or they can gradually retract inside the stump, a phenomenon referred to as “telescoping”.  Telescoping is relevant from a clinical point of view, as it tends to be related to increased levels of phantom pain. In the current study we demonstrate how a full-body illusion can be used to temporarily revoke telescoping sensations in upper limb amputees. During this illusion participants view the body of a mannequin from a first person perspective while being subjected to synchronized visuo-tactile stimulation through stroking, which makes them experience the mannequin’s body as their own. In Experiment 1 we used an intact mannequin, and showed that amputees can experience ownership of an intact body as well as referral of touch from both hands of the mannequin. In Experiment 2 and 3 we used an amputated mannequin, and demonstrated that depending on the spatial location of the strokes applied to the mannequin, participants experienced their phantom hand to either remain telescoped, or to actually be located below the stump. The effects were supported by subjective data from questionnaires, as well as verbal reports of the perceived location of the phantom hand in a visual judgment task. These findings are of particular interest, as they show that the temporary revoking of telescoping sensations does not necessarily have to involve the visualization of an intact hand or illusory movement of the phantom (as in the rubber hand illusion or mirror visual feedback therapy), but that it can also be obtained through mere referral of touch from the stump to the spatial location corresponding to that previously occupied by the intact hand. Moreover, our study also provides preliminary evidence for the fact that these manipulations can have an effect on phantom pain sensations

Perceptual and Memorial Contributions to Developmental Prosopagnosia

Developmental prosopagnosia (DP) is commonly associated with the failure to properly perceive individuating facial properties, notably those conveying configural or holistic content. While this may indicate that the primary impairment is perceptual, it is conceivable that some cases of DP are instead caused by a memory impairment, with any perceptual complaint merely allied rather than causal. To investigate this possibility, we administered a battery of face perception tasks to 11 individuals who reported that their face recognition difficulties disrupt daily activity and who also performed poorly on two formal tests of face recognition. Group statistics identified, relative to age- and gender-matched controls, difficulties in apprehending global-local relations and the holistic properties of faces, and in matching across viewpoints, but these were mild in nature and were not consistently evident at the level of individual participants. Six of the 11 individuals failed to show any evidence of perceptual impairment. In the remaining five individuals, no single perceptual deficit, or combination of deficits, was necessary or sufficient for poor recognition performance. These data suggest that some cases of DP are better explained by a memorial rather than perceptual deficit, and highlight the relevance of the apperceptive/associative distinction more commonly applied to the allied syndrome of acquired prosopagnosia

Multi-voxel pattern analysis (MVPA) reveals abnormal fMRI activity in both the 'core' and 'extended' face network in congenital prosopagnosia

The ability to identify faces is mediated by a network of cortical and subcortical brain regions in humans. It is still a matter of debate which regions represent the functional substrate of congenital prosopagnosia (CP), a condition characterized by a lifelong impairment in face recognition, and affecting around 2.5% of the general population. Here, we used functional Magnetic Resonance Imaging (fMRI) to measure neural responses to faces, objects, bodies, and body-parts in a group of seven CPs and ten healthy control participants. Using multi-voxel pattern analysis (MVPA) of the fMRI data we demonstrate that neural activity within the “core” (i.e., occipital face area and fusiform face area) and “extended” (i.e., anterior temporal cortex) face regions in CPs showed reduced discriminability between faces and objects. Reduced differentiation between faces and objects in CP was also seen in the right parahippocampal cortex. In contrast, discriminability between faces and bodies/body-parts and objects and bodies/body-parts across the ventral visual system was typical in CPs. In addition to MVPA analysis, we also ran traditional mass-univariate analysis, which failed to show any group differences in face and object discriminability. In sum, these findings demonstrate (i) face-object representations impairments in CP which encompass both the “core” and “extended” face regions, and (ii) superior power of MVPA in detecting group differences