Biology subjects

Farne, A.

Publications and source records attributed to Farne, A..

17 recordsLinked to original sources

bioRxiv2026

Detecting movement preparation with HYDRE: a hybrid model of temporal and spectral brain signals

Previous research on brain-computer interfaces (BCIs) has demonstrated the feasibility of decoding different movements. However, less attention has been given to detecting motor preparation (i.e., decoding from brain signals whether or not a participant is about to perform a given movement). In this study, we wanted to assess the performance of a new model, rooted in motor preparation physiology, in detecting an upcoming movement across the period preceding a voluntary action. Participants (n=18, including 7 females) performed a simple self-paced motor task where they either pressed a button to change an image shown on screen, or let the computer change the image. Participants' brain activity was recorded using magnetoencephalography and submitted to a newly developed linear ensemble classifier that relies on features extracted using PCA from the temporal, spectral and Riemannian domain. We then compared its performance against other classifiers used in BCIs. Our HYbrid Domain Riemannian Ensemble (HYDRE) classifier emerged as the best-performing method, achieving average above-chance decoding up to 1400ms before the action, with a maximum ROC score of 76% at the time of the button press. Moreover, decoding performance in the temporal and Riemannian domains was respectively predictive of Readiness Field and Event-Related Desynchronization magnitudes, two well-known motor preparation markers. Combining features from the temporal, spectral, and Riemannian domains significantly improved motor preparation decoding compared to single-domain approaches. By leveraging the most discriminative features from each domain, HYDRE yielded consistent performance gains across participants with varying baseline decoding performance, effectively addressing inter-individual variability in motor preparation markers.

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bioRxiv2025

The sense of agency in near and far space: where do we stand?

Modern technology frequently places the consequences of our actions at a distance (e.g., remote surgery, smart-home control, virtual reality). Does spatial distance between an action and its outcome weaken the sense of agency (SoA) - the feeling of control over ones actions and consequences? Two recent studies answered "yes", reporting stronger temporal binding (TB) in near than far space and interpreting this as greater implicit agency (Jenkins & Obhi, 2021; Mariano et al., 2024). A third study - our own work with a similar paradigm - found no distance effect (Kong et al., 2024). Here we (i) provide a rigorous side-by-side methodological comparison of the three studies, (ii) argue why a direct test to establish a distance modulation of TB (the Near - Far difference of the Active - Passive delta) should be performed in order to reach meaningful conclusions, and (iii) report new re-analyses of our data and direct tests on the two target studies. Overall, current evidence does not support a distance effect on SoA. Our reassessment provides alternative explanations that converge with available evidence suggesting that distance may influence temporal interval perception, but that effect is independent of action intention and therefore of agency. Public Significance StatementIn our increasingly connected world, we often interact with devices and influence events that are physically distant from us - like controlling smart appliances remotely or engaging in virtual reality experiences. Does the distance between us and the effects of our actions change how much we feel in control of the outcomes of our actions? Recent studies have suggested that we feel less responsible when action outcomes appear in far space compared to near space. However, methodological limitations in these studies, as well as our own results with a similar paradigm, challenge the validity of this claim. We aim to contribute to the crucial debate on the role of spatial distance on humans feeling of responsibility by providing a respectful though critical analysis of recent findings and offering recommendations for future research.

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bioRxiv2025

Spatial distance and temporal attentional focus modulate voluntary action preparation and awareness

Peripersonal space (PPS)--the immediate space surrounding the body--modulates perception and motor control. However, its impact on how voluntary actions are initiated and subjectively experienced remains underexplored. Similarly, how directing attention to different phases of an action, such as intention formation versus execution, and anticipating outcomes of an action, modulates the neural readiness for movement, has yet to be fully examined. This study investigates whether spatial proximity, attentional focus, and anticipated action outcomes influence action preparation and action awareness, using a virtual reality adaptation of the Libet clock paradigm during EEG recordings. Neural results reveal that attentional focus and anticipated action outcomes modulate different phases of motor preparation, as indexed by the readiness potential (RP)--a gradual buildup of neural activity preceding voluntary movement. Focusing on decision timing (without subsequent action outcomes) enhances early RP amplitude and decreases the late RP slope, suggesting increased preparatory neural engagement during intention formation. In contrast, focusing on action execution leads to a steeper late RP slope, indicating later and faster motor activity buildup when attention is directed toward movement onset. Anticipating action outcomes increased late RP slope, which was accompanied by the temporal binding effect: when a tone followed the action, both decision and action estimates shifted toward it. Spatial proximity also modulates early RP slope, with a steeper buildup in near versus far space, suggesting facilitated motor preparation within PPS. It further enhances the late RP amplitude when participants focused on their intention to act. Behavioural results show that actions are perceived as occurring earlier when the clock is displayed near compared to far, indicating that PPS influences the temporal perception of action timing. Overall, these findings highlight the dynamic interplay among external spatial context and internal cognitive processes in shaping motor preparation and action awareness. Importantly, a temporal internal attentional focus on intention to act modulates early RP--traditionally considered an unconscious stage of neural readiness. These results contribute to a deeper understanding of how PPS and the locus of attention on specific action phases affect action preparation and awareness, with potential implications for future research on the sense of agency and voluntary action decision making.

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bioRxiv2024

Repetitive Somatosensory Stimulation Shrinks The Body Image

Current models of mental body representations (MBRs) indicate that tactile inputs feed several of them for different functions, implying that altering tactile inputs may affect MBRs differently. Here we tested this hypothesis by leveraging Repetitive Somatosensory Stimulation (RSS), known to improve tactile perception by modulating primary somatosensory cortex (SI) activity, and measured its effects over the body image, the body model and the superficial schema in a randomized sham-controlled, double-blind cross-over study. Results show that RSS affected the body image, participants perceiving their finger size as being smaller after RSS. While previous work showed increase of finger size perception after tactile anesthesia (Gandevia & Phegan 1999), these findings reveal that tactile inputs can diametrically modulate the body image. In contrast, RSS did not alter the body model or superficial schema. In addition, we report a novel mislocalization pattern, with a bias towards the middle finger in the distal phalanges that reverses towards the thumb in the proximal phalanx, enriching the known distortions of the superficial schema. Overall, these findings provide novel insights into the functional organization of MBRs and their relationships with somatosensory information. Reducing the perceived body size through RSS could be useful in helping treat body image disturbance.

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bioRxiv2024

Extending tactile space with hand-held tools: A re-analysis and review

Tools can extend the sense of touch beyond the body, allowing the user to extract sensory information about distal objects in their environment. Though research on this topic has trickled in over the last few decades, little is known about the neurocomputational mechanisms of extended touch. In 2016, along with our late collaborator Vincent Hayward, we began a series of studies that attempted to fill this gap. We specifically focused on the ability to localize touch on the surface of a rod, as if it were part of the body. We have conducted eight behavioral experiments over the last several years, all of which have found that humans are incredibly accurate at tool-extended tactile localization. In the present article, we perform a model-driven reanalysis of these findings with an eye towards estimating the underlying parameters that map sensory input into spatial perception. This reanalysis revealed that users can almost perfectly localize touch on hand-held tools. This raises the question of how humans can be so good at localizing touch on an inert non-corporeal object. The remainder of the paper focuses on three aspects of this process that occupied much of our collaboration with Vincent: the mechanical information used by participants for localization; the speed by which the nervous system can transform this information into a spatial percept; and whether body-based computations are repurposed for tool-extended touch. In all, these studies underscore the special relationship between bodies and tools.

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bioRxiv2023

No evidence in favour of the existence of 'intentional' binding

Intentional binding refers to the subjective temporal compression between a voluntary action and its sensory outcome. Despite some studies having challenged the link between temporal compression and intentional action, the intentional binding is still widely used as an implicit measure for the sense of agency. The debate remains unsettled primarily because the experimental conditions used in previous studies were confounded with various alternative causes for temporal compression, and action intention has not yet been tested comprehensively against all potential alternative causes in a single study. Here, we solve this puzzle by jointly comparing participants estimates of the interval between three types of triggering events with comparable predictability - voluntary movement, passive movement, external sensory event - and an external sensory outcome (auditory or visual across experiments). Results failed to show intentional binding, i.e., no shorter interval estimation for the voluntary than the passive movement conditions. Instead, we observed temporal (but not intentional) binding when comparing both movement conditions to the external sensory condition. Thus, temporal binding seems to originate from sensory integration and temporal prediction, not from action intention. As such, these findings underscore the need to reconsider the use of "intentional binding" as a reliable proxy of the sense of agency. Public Significance StatementWhen we press a light switch and observe a bulb lightening, we experience a sense of agency, a feeling of control over these events. We also estimate the temporal interval between our voluntary action and its consequence shorter than the same interval between two events in which we are not involved. Such temporal binding has thus been taken as a measure of the sense of agency. However, our study reveals that voluntary actions are neither necessary, nor sufficient for temporal binding. Instead, temporal binding relies on predicting and integrating information. The sense of agency can be disturbed in various psychiatric disorders and its brain mechanisms are currently actively explored. Our study urges amending how it is measured.

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bioRxiv2023

Implicit motor adaptation and perceived hand position without proprioception: A kinesthetic error may be derived from efferent signals

Implicit sensorimotor adaptation keeps our movements well-calibrated amid changes in the body and environment. We have recently postulated that implicit adaptation is driven by a perceptual error: the difference between the desired and perceived movement outcome. According to this perceptual re-alignment model, implicit adaptation ceases when the perceived movement outcome - a multimodal percept determined by a prior belief conveying the intended action, the motor command, and feedback from proprioception and vision - is aligned with the desired movement outcome. Here, we examined the role of proprioception in implicit motor adaptation and perceived movement outcome by examining individuals who lack proprioception. We used a modified visuomotor rotation task designed to isolate implicit adaptation and probe perceived outcome throughout the experiment. Surprisingly, implicit adaptation and perceived outcome were minimally impacted by deafferentation, posing a challenge to the perceptual re-alignment model of implicit adaptation.

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bioRxiv2022

Alpha oscillations reflect similar mapping mechanisms for localizing touch on hands and tools

Numerous studies have suggested that tools become incorporated into a representation of our body. A prominent hypothesis suggests that our brain re-uses body-based computations when we use tools. However, little is known about how this is implemented at the neural level. Here we used the ability to localize touch on both tools and body parts as a case study to fill this gap. Neural oscillations in the alpha (8-13 Hz) and beta (15-25 Hz) frequency bands are involved in mapping touch on the body in distinct reference frames. Alpha activity reflects the mapping of touch in external coordinates, whereas beta activity reflects the mapping of touch in skin-centered coordinates. Here, we aimed at pinpointing the role of these oscillations during tool-extended sensing. We recorded participants oscillatory activity while tactile stimuli were applied to either hands or the tips of hand-held rods. The posture of the hands/tool-tips was uncrossed or crossed at participants body midline in order for us to disentangle brain responses related to different coordinate systems. We found that alpha-band activity was modulated similarly across postures when localizing touch on hands and on tools, reflecting the position of touch in external space. Source reconstruction also indicated a similar network of cortical regions involved for tools and hands. Our findings strongly suggest that the brain uses similar oscillatory mechanisms for mapping touch on the body and tools, supporting the idea of neural processes being repurposed for tool-use. SIGNIFICANCE STATEMENTTool use is one of the defining traits of humankind. Tools allow us to explore our environment and expand our sensorimotor abilities. A prominent hypothesis suggests that our brain re-uses body-based neural processing to swiftly adapt to the use of tools. However, little is known about how this is implemented at the neural level. In the present study we used the ability to map touch on both tools and body parts as a case study to fill this gap. We found that the brain uses similar oscillatory mechanisms for mapping touch on a hand-held tool and on the body. These results provide novel and compelling support to the idea that neural processes devoted to body-related information are re-purposed for tool-use.

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bioRxiv2021

A somatosensory computation that unifies bodies and tools

It is often claimed that tools are embodied by the user, but whether the brain actually repurposes its body-based computations to perform similar tasks with tools is not known. A fundamental computation for localizing touch on the body is trilateration. Here, the location of touch on a limb is computed by integrating estimates of the distance between sensory input and its boundaries (e.g., elbow and wrist of the forearm). As evidence of this computational mechanism, tactile localization on a limb is most precise near its boundaries and lowest in the middle. We show that the brain repurposes trilateration to localize touch on a tool. In a large sample of participants, we found that localizing touch on a tool produced the signature of trilateration, with highest precision close to the base and tip of the tool. A computational model of trilateration provided a good fit to the observed localization behavior. To further demonstrate the computational plausibility of repurposing trilateration, we implemented it in a three-layer neural network that was based on principles of probabilistic population coding. This network determined hit location in tool-centered coordinates by using a tools unique pattern of vibrations when contacting an object. Simulations demonstrated the expected signature of trilateration, in line with the behavioral patterns. Our results have important implications for how trilateration may be implemented by somatosensory neural populations. We conclude that trilateration is a fundamental spatial computation that unifies limbs and tools.

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bioRxiv2021

Alpha oscillations are involved in localizing touch on hand-held tools

The sense of touch is not restricted to the body but can also extend to external objects. When we use a hand-held tool to contact an object, we feel the touch on the tool and not in the hand holding the tool. The ability to perceive touch on a tool actually extends along its entire surface, allowing the user to accurately localize where it is touched similarly as they would on their body. While the neural mechanisms underlying the ability to localize touch on the body have been largely investigated, those allowing to localize touch on a tool are still unknown. We aimed to fill this gap by recording the EEG signal of participants while they localized tactile stimuli on a hand-held rod. We focused on oscillatory activity in the alpha (7-14 Hz) and beta (15-30 Hz) range, as they have been previously linked to distinct spatial codes used to localize touch on the body. Beta activity reflects the mapping of touch in skin-based coordinates, whereas alpha activity reflects the mapping of touch in external space. We found that alpha activity was solely modulated by the location of tactile stimuli applied on a hand-held rod. Source reconstruction suggested that this alpha power modulation was localized in a network of fronto-parietal regions previously implicated in higher-order tactile and spatial processing. These findings are the first to implicate alpha oscillations in tool-extended sensing and suggest an important role for processing touch in external space when localizing touch on a tool.

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bioRxiv2021

Body representation plasticity is altered in Developmental Coordination Disorder

Developmental Coordination Disorder (DCD) is a pathological condition characterized by impaired motor skills. Current theories advance that a deficit of the internal models is mainly responsible for DCD childrens altered behavior. Yet, accurate movement execution requires not only correct movement planning, but also integration of sensory feedback into body representation for action (Body Schema) to update the state of the body. Here we advance and test the hypothesis that the plasticity of this body representation is altered in DCD. To probe Body Schema (BS) plasticity, we submitted a well-established tool-use paradigm to seventeen DCD children, required to reach for an object with their hand before and after tool use, and compared their movement kinematics to that of a control group of Typically Developing (TD) peers. We also asked both groups to provide explicit estimates of their arm length to probe plasticity of their Body Image (BI). Results revealed that DCD children explicitly judged their arm shorter after tool use, showing changes in their BI comparable to their TD peers. Unlike them, though, DCD did not update their implicit BS estimate: kinematics showed that tool use affected their peak amplitudes, but not their latencies. Remarkably, the kinematics of tool use showed that the motor control of the tool was comparable between groups, both improving with practice, confirming that motor learning abilities are preserved in DCD. This study thus brings evidence in favor of an alternative theoretical account of the DCD etiology. Our findings point to a deficit in the plasticity of the body representation used to plan and execute movements. Though not mutually exclusive, this widens the theoretical perspective under which DCD should be considered: DCD may not be limited to a problem affecting the internal models and their motor functions, but may concern the state of the effector they have to use.

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bioRxiv2020

A neural surveyor in somatosensory cortex

Perhaps the most recognizable sensory map in all of neuroscience is the somatosensory homunculus. Though it seems straightforward, this simple representation belies the complex link between an activation in a somatotopic map and the associated touch location on the body. Any isolated activation is spatially ambiguous without a neural decoder that can read its position within the entire map, but how this is computed by neural networks is unknown. We propose that the somatosensory system implements multilateration, a common computation used by surveying and GPS systems to localize objects. Specifically, to decode touch location on the body, multilateration estimates the relative distance between the afferent input and the boundaries of a body part (e.g., the joints of a limb). We show that a simple feedforward neural network, which captures several fundamental receptive field properties of cortical somatosensory neurons, can implement a Bayes-optimal multilateral computation. Simulations demonstrated that this decoder produced a pattern of localization variability between two boundaries that was unique to multilateration. Finally, we identify this computational signature of multilateration in actual psychophysical experiments, suggesting that it is a candidate computational mechanism underlying tactile localization.

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bioRxiv2020

Patterns of multisensory facilitation distinguish peripersonal from reaching space

Peripersonal space (PPS) is a multisensory representation of the space near body parts facilitating interactions with the close environment. Studies on non-human and human primates converge in showing that PPS is a body-part-centred representation that guides actions. Because of these characteristics, growing confusion conflates peripersonal and arm-reaching space (ARS), that is the space ones arm can reach. Despite neuroanatomical evidence favors their distinction, no study has contrasted directly their respective extent and behavioral features. Here, in five experiments (N=140) we found that PPS differs from ARS, as evidenced both by participants spatial and temporal performance and its modeling. We mapped PPS and ARS using both their respective gold standard tasks and a novel multisensory facilitation paradigm. Results show that 1) PPS is smaller than ARS; 2) multivariate analyses of spatial patterns of multisensory facilitation predict participants hand locations within ARS; 3) the multisensory facilitation map shifts isomorphically following hand positions, revealing hand-centred coding of PPS, therefore pointing to a functional similarity to the receptive fields of monkeys multisensory neurons. A control experiment further corroborated these results and additionally ruled out the orienting of attention as driving mechanism for the increased multisensory facilitation near the hand. In sharp contrast, ARS mapping results in a larger spatial extent, with undistinguishable patterns across hand positions, cross-validating the conclusion that PPS and ARS are distinct spatial representations. These findings urge for a refinement of theoretical models of PPS, which is relevant to constructs as diverse as self-representation, social interpersonal distance, and motor control.

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bioRxiv2020

The role of the vestibular system in value attribution to positive and negative reinforcers

Somatic inputs originating from bioregulatory processes can guide cognition and behavior. One such bodily signal, mostly overlooked so far, is represented by visuo-vestibular coupling and its alteration, which in extreme cases may result in motion sickness. We argued that the inherently perturbed interoceptive state that follows can be a powerful determinant of human motivated behavior, resulting in a blunted response to appetitive stimuli and an exaggerated response to noxious ones. We sought to assess such differential impact of visuo-vestibular mismatches on value through a task involving conflict monitoring. We therefore administered to 42 healthy participants a modified version of the Flankers task, in which distractors (arrows, pointing in either a congruent or incongruent direction) signaled the availability of monetary incentives (gains, losses, or neutral trials). While performing the task, participants received either galvanic vestibular stimulation (GVS), or sham stimulation. We have found impaired behavioral performances when value, which was attached to task-irrelevant information, was at stake. Gains and losses, interestingly, dissociated, and only the latter caused enhanced interference costs in the task, suggesting that negative incentives may be more effective in capturing human attention than positive ones. Finally, we have found some weak evidence for GVS to further increase the processing of losses, as suggested by even larger interference costs in this condition. Results were, however, overall ambiguous, and suggest that much more research is needed to better understand the link between the vestibular system and motivation. HighlightsO_LIVisuo-Vestibular mismatches may be important somatic markers affecting the evaluation of reinforcers; C_LIO_LIWhen attached to distractors, value information impairs behavioral performance for the task at hand; C_LIO_LITrials in which potential losses were at stake were associated with larger interference costs arising from conflicting information between the target and the flankers; C_LIO_LIGVS (Right-Anodal) may further increase the interference caused by losses, but the evidence in this respect was ambiguous and inconclusive; C_LI

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bioRxiv2020

Reaching to sounds in virtual reality: A multisensory-motor approach to re-learn sound localisation

When localising sounds in space the brain relies on internal models that specify the correspondence between the auditory input reaching the ears and initial head-position with coordinates in external space. These models can be updated throughout life, setting the basis for re-learning spatial hearing abilities in adulthood. This is particularly important for individuals who experience long-term auditory alterations (e.g., hearing loss, hearing aids, cochlear implants) as well as individuals who have to adapt to novel auditory cues when listening in virtual auditory environments. Until now, several methodological constraints have limited our understanding of the mechanisms involved in spatial hearing re-learning. In particular, the potential role of active listening and head-movements have remained largely overlooked. Here, we overcome these limitations by using a novel methodology, based on virtual reality and real-time kinematic tracking, to study the role of active multisensory-motor interactions with sounds in the updating of sound-space correspondences. Participants were immersed in a virtual reality scenario showing 17 speakers at ear-level. From each visible speaker a free-field real sound could be generated. Two separate groups of participants localised the sound source either by reaching or naming the perceived sound source, under binaural or monaural listening. Participants were free to move their head during the task and received audio-visual feedback on their performance. Results showed that both groups compensated rapidly for the short-term auditory alteration caused by monaural listening, improving sound localisation performance across trials. Crucially, compared to naming, reaching the sounds induced faster and larger sound localisation improvements. Furthermore, more accurate sound localisation was accompanied by progressively wider head-movements. These two measures were significantly correlated selectively for the Reaching group. In conclusion, reaching to sounds in an immersive visual VR context proved most effective for updating altered spatial hearing. Head movements played an important role in this fast updating, pointing to the importance of active listening when implementing training protocols for improving spatial hearing. HIGHLIGHTS- We studied spatial hearing re-learning using virtual reality and kinematic tracking - Audio-visual feedback combined with active listening improved monaural sound localisation - Reaching to sounds improved performance more than naming sounds - Monaural listening triggered compensatory head-movement behaviour - Head-movement behaviour correlated with re-learning only when reaching to sounds

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bioRxiv2020

SPHERE: A novel approach to 3D and active sound localization

In everyday life, localizing a sound source in free-field entails more than the sole extraction of monaural and binaural auditory cues to define its location in the three-dimensions (azimuth, elevation and distance). In spatial hearing, we also take into account all the available visual information (e.g., cues to sound position, cues to the structure of the environment), and we resolve perceptual ambiguities through active listening behavior, exploring the auditory environment with head or/and body movements. Here we introduce a novel approach to sound localization in 3D named SPHERE (European patent n{degrees} WO2017203028A1), which exploits a commercially available Virtual Reality Head-mounted display system with real-time kinematic tracking to combine all of these elements (controlled positioning of a real sound source and recording of participants responses in 3D, controlled visual stimulations and active listening behavior). We prove that SPHERE allows accurate sampling of the 3D spatial hearing abilities of normal hearing adults, and it allowed detecting and quantifying the contribution of active listening. Specifically, comparing static vs. free head-motion during sound emission we found an improvement of sound localization accuracy and precisions. By combining visual virtual reality, real-time kinematic tracking and real-sound delivery we have achieved a novel approach to the study of spatial hearing, with the potentials to capture real-life behaviors in laboratory conditions. Furthermore, our new approach also paves the way for clinical and industrial applications that will leverage the full potentials of active listening and multisensory stimulation intrinsic to the SPHERE approach for the purpose rehabilitation and product assessment.

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bioRxiv2019

Electrocutaneous stimulation to the face inhibits motor evoked potentials in the hand: face-hand interactions revealed by afferent inhibition

Reorganization of the sensorimotor cortex following amputation and other interventions has revealed large-scale plastic changes between the hand and face representations. To investigate whether hand-face interactions are also present in the normal state of the system we measured sensorimotor interactions between these two areas using an afferent inhibition transcranial magnetic stimulation (TMS) protocol in which the TMS motor evoked potential (MEP) is inhibited when it is preceded by an afferent stimulus. We hypothesized that if hand-face interactions exist in the normal state of the system then stimulation of the face would inhibit hand MEPs. In two separate experiments we delivered an electrocutaneous stimulus to either the right upper lip (Experiment 1) or right cheek (Experiment 2) and recorded muscular activity from the right first dorsal interosseous (FDI). Both lip and cheek stimulation inhibited FDI MEPs. To investigate the specificity of this effect we conducted two additional experiments in which cutaneous stimulation was applied to either the right forearm (Experiment 3) or right arm (Experiment 4). Neither forearm nor arm stimulation inhibited FDI MEPs. These data provide the first evidence for face-to-hand afferent inhibition and we suggest that the mechanisms underlying these sensorimotor interactions could contribute to face/hand interactions observed following sensorimotor reorganisation.

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