Biology subjects

Binda, P.

Publications and source records attributed to Binda, P..

11 recordsLinked to original sources

bioRxiv2026

Residual cortical responses and network reorganization in inherited retinal degeneration: electrophysiological evidence

Retinitis pigmentosa (RP) progressively deprives the retina of input, but whether the responsiveness of the visual cortex declines in parallel, remains preserved, or increases through compensatory gain remains unclear. Indeed, a weaker visually evoked response cannot, on its own, distinguish these possibilities, since it is equally compatible with a passively degraded input and with an actively recalibrated cortex. We combined spatially resolved steady-state visual evoked potentials (SSVEPs), which index stimulus-driven activity, with transcranial magnetic stimulation combined with electroencephalography (TMS-EEG), which probes cortical reactivity independently of vision, in patients with RP and in healthy controls. Nine patients (PTs) with RP (five women, age range 28 to 69 years) and nineteen sex-, age-, and handedness-matched healthy controls (thirteen women, mean age 42.6 years) were tested. They underwent SSVEP recordings to stimuli presented at three eccentricities (central, intermediate, peripheral) and single-pulse TMS-EEG over the left and right occipital cortex and, as a non-visual control site, the dominant motor cortex. We quantified SSVEP amplitude and phase at 12 Hz, early TMS-evoked potentials, oscillatory power, inter-trial phase synchrony, and functional connectivity and graph-theoretical network measures derived from the weighted phase lag index. SSVEP amplitude followed the expected central-to-peripheral gradient: PTs were comparable to healthy controls at the center, reduced but still above their own resting baseline at intermediate eccentricity, and no longer distinguishable from baseline in the periphery; phase differed from controls in a quarter of the central and half of the intermediate sectors. Occipital stimulation elicited a larger early negative deflection after left-hemisphere stimulation in PTs compared to controls, a stronger beta-band event-related spectral perturbation after stimulation of either hemisphere, and stronger, more efficiently distributed post-stimulus connectivity, despite comparable pre-stimulus connectivity, resting motor threshold, and most early evoked components. The pattern was site- and hemisphere-specific: left occipital stimulation produced widespread, mainly contralateral effects; right occipital stimulation a more circumscribed ipsilateral one, and motor cortex stimulation showed altered alpha-band activity without the bilateral occipital beta effect. Together, these results show that progressive retinal deafferentation in RP does not produce a parallel decline in cortical responsiveness. Visually driven activity weakens with eccentricity, while direct cortical perturbation reveals preserved and, at selected sites, enhanced reactivity. This dissociation is consistent with a homeostatic increase in cortical gain rather than a uniform loss of cortical function, and indicates that the deafferented cortex retains, and in places strengthens, its capacity to respond as retinal input deteriorates.

neuroscience↗

bioRxiv2026

Physiologically Informed PCA-Partial Correlation for highly Collinear Brainstem fMRI Networks

Functional connectivity (FC) approaches from resting-state fMRI (rs-fMRI) are amply spread to investigate the cortical organization, yet the brainstem remains relatively underexplored despite its pivotal roles in both physiological and pathological conditions. The highly collinear network, in which the strongly interconnected nodes and the widespread neuromodulatory influences induce indirect or mediated interactions, make the estimation of direct brainstem FC challenging. Standard bivariate methods fail to recover the true network structure in such complex topologies, causing false positive interactions. On the other hand, partial correlation can potentially estimate the direct FC, but multicollinearity issues and collider-induced spurious correlations limit its application in high-dimensional scenarios. Here, we propose a physiologically informed framework in which the conditioning strategy for partial correlation estimation is tailored for the investigation of the brainstem and its direct interactions within the network and with whole-brain regions. Specifically, we employed a PCA-regularized partial correlation (PCA - {rho}PC) approach, where PCA is applied to the brainstem covariates to mitigate multicollinearity and model shared modulatory variance. We show that PCA - {rho}PC improves the robustness and interpretability of brainstem FC, yielding sparser and more physiologically plausible connectomes compared with conventional (regularized) approaches. Both simulation and real fMRI data raise the possibility that Pearsons and PCA-regularized approaches may complement each other in an effort to unravel the pattern of direct vs. indirect effects in highly collinear settings, paving the way for future extensions in a wide range of multivariate neuroimaging applications.

bioengineering↗

bioRxiv2025

Acute supplementation of beta-hydroxybutyrate increases visual cortical excitability in humans: a combined EEG and MRS study

Increasing plasma levels of ketone bodies via supplementation or dieting has been repeatedly used to ameliorate neurological symptoms and enhance cognitive performance. Here we aim to gain insight into the underlying mechanisms by characterizing the acute effects on visual cortical function of a single dose {beta}-hydroxybutyrate ({beta}HB) supplementation. Young human volunteers were orally administered a {beta}HB ester; we used EEG to assess cortical excitability and responsivity to visual stimulation, and Magnetic Resonance Spectroscopy to quantify glutamate and GABA+ concentrations in the occipital cortex. {beta}HB supplementation increased the amplitude of Visual Evoked Potentials and enhanced the resting-state EEG alpha rhythm. These electrophysiological changes were paralleled by a neurometabolic change in the occipital cortex, where glutamate (but not GABA+) concentration increased. The glutamate increase was correlated with the increased Visual Evoked Potential amplitude. This suggests that acute {beta}HB supplementation increases the excitability of the brain cortex, as assessed neurometabolically and electrophysiologically.

neuroscience↗

bioRxiv2025

The pulvinar regulates plasticity in human visual cortex

In normally sighted human adults, two-hours of monocular deprivation is sufficient to transiently alter ocular dominance. Here we show that this is associated with a reduction of functional connectivity between the pulvinar and early visual cortex, selective for the pulvinar-to-V1 directionality. Across participants, the strength of the pulvinar-to-V1 connectivity was negatively correlated with the ocular dominance shift, implying less plasticity in participants with stronger influence of the pulvinar over V1. Our results support a revised model of adult V1 plasticity, where short-term reorganization is gated by modulatory signals relayed by the pulvinar. TeaserShort-term monocular deprivation triggers a reorganization of the visual processing network, measured with 7TfMRI in human adults.

neuroscience↗

bioRxiv2025

Short-term monocular deprivation in adult humans: a meta-analysis and new perspectives

Starting from the early 2010s [1, 2], several studies have shown that a short period of monocular deprivation in adult volunteers transiently shifts ocular dominance in favor of the deprived eye. We compiled a meta-analysis of 73 such studies that measured the effects of monocular deprivation and related manipulations, using a diverse set of techniques [1-73]. The ocular dominance shift elicited by monocular deprivation was comparable across studies where deprivation was achieved with an opaque or translucent patch and irrespectively of whether the dominant or non-dominant eye was deprived. Effects were larger and longer lasting after longer periods of deprivation. Qualitatively similar effects were produced by monocular manipulations that did not reduce the strength of the stimulus: filtering or distorting the image in one eye, suppressing it from awareness or merely making it task irrelevant. We discuss the available evidence in the light of current models and a new perspective inspired by predictive coding.

neuroscience↗

bioRxiv2021

Short-term plasticity in the visual thalamus

While there is evidence that the visual cortex retains a potential for plasticity in adulthood, less is known about the subcortical stages of visual processing. Here we asked whether short-term ocular dominance plasticity affects the visual thalamus. We addressed this question in normally sighted adult humans, using ultra-high field (7T) magnetic resonance imaging combined with the paradigm of short-term monocular deprivation. With this approach, we previously demonstrated transient shifts of perceptual eye dominance and ocular dominance in visual cortex (Binda et al., 2018). Here we report evidence for short-term plasticity in the ventral division of the pulvinar (vPulv), where the deprived eye representation was enhanced over the non-deprived eye. This pulvinar plasticity effect was similar as previously seen in visual cortex and it was correlated with the ocular dominance shift measured behaviorally. In contrast, there was no short-term plasticity effect in Lateral Geniculate Nucleus (LGN), where results were reliably different from vPulv, despite their spatial proximity. We conclude that the visual thalamus retains potential for short-term plasticity in adulthood; the plasticity effect differs across thalamic subregions, possibly reflecting differences in their cortical connectivity.

neuroscience↗

bioRxiv2021

Attention cueing in rivalry: insights from pupillometry

We used pupillometry to evaluate the effects of attention cueing on perceptual bi-stability, as reported by adult human observers. Perceptual alternations and pupil diameter were measured during two forms of rivalry, generated by presenting a white and a black disk to the two eyes (binocular rivalry) or splitting the disks between eyes (interocular grouping rivalry). In line with previous studies, we found that subtle pupil size oscillations (about 0.05 mm) tracked alternations between exclusive dominance phases of the black or white disk. These oscillations were larger for perceptually stronger stimuli: presented to the dominant eye or with physically higher luminance contrast. However, cueing of endogenous attention to one of the rivaling percepts did not affect pupil oscillations during exclusive dominance phases. This was in spite of the reliable effects of endogenous attention on perceptual dominance, which shifted in favor of the cued percept by about 10%. The results were comparable for binocular and interocular grouping rivalry. Cueing only had a marginal modulatory effect on pupil size during mixed percepts in binocular rivalry. This may suggest that, rather than acting by modulating perceptual strength, endogenous attention primarily acts during periods of unresolved competition, which is compatible with attention being automatically directed to the rivaling stimuli during periods of exclusive dominance and thereby sustaining perceptual alternations. Significance StatementBinocular rivalry depends on attention. When it is diverted away from the stimuli, perceptual alternations slow down; when it is preferentially directed to one stimulus, perception lingers more on it, consistent with attention enhancing the effective strength of the rivaling stimuli. Here we introduce pupillometry as a means to indirectly track changes in effective stimulus strength. We find that pupil size oscillates, accurately tracking perceived luminance during two forms of rivalry: binocular rivalry and interocular grouping rivalry. Both show robust effects of attention cueing on perceptual dominance, but pupil oscillations during exclusive dominance are unaffected by cueing. This suggests that endogenous attention does not affect perceptual strength during exclusive dominance, though it might do so during transition phases.

neuroscience↗

bioRxiv2021

Objective pupillometry shows that perceptual styles covary with autistic-like personality traits

We measured the modulation of pupil-size (in constant lighting) elicited by observing transparent surfaces of black and white moving dots, perceived as a cylinder rotating about its vertical axis. The direction of rotation was swapped periodically by flipping stereo-depth of the two surfaces. Pupil size modulated in synchrony with the changes in front-surface color (dilating when black). The magnitude of pupillary modulation was larger for participants with higher Autism-Spectrum Quotient (AQ), consistent with a local style of perception, with attention focused on the front surface. The modulation with surface color, and its correlation with AQ, was equally strong when participants passively viewed the stimulus. No other indicator, including involuntary pursuit eye-movements, covaried with AQ. These results reinforce our previous report with a similar bistable stimulus (Turi, Burr, & Binda, 2018), and go on to show that bistable illusory motion is not necessary for the effect, or its dependence on AQ.

neuroscience↗

bioRxiv2020

Temporal binding of Visual and Motor cortical oscillations revealed by BOLD response in Humans

The mechanisms coordinating action and perception over time are poorly understood. The sensory cortex needs to prepare for upcoming changes contingent on action, and this requires temporally precise communication that takes into account the variable delays between sensory and motor processing. Several theorists1,2 have proposed synchronization of the endogenous oscillatory activity observed in most regions of the brain3 as the basis for an efficient and flexible communication protocol between distal brain areas2,4, a concept known as "communication through coherence". Synchronization of endogenous oscillations5,6 occurs after a salient sensory stimulus, such as a flash or a sound7-11, and after a voluntary action12-18, and this impacts directly on perception, causing performance to oscillate rhythmically over time. Here we introduce a novel fMRI paradigm to probe the neural sources of oscillations, based on the concept of perturbative signals, which overcomes the low temporal resolution of BOLD signals. The assumption is that a synchronized endogenous rhythm will modulate cortical excitability rhythmically, which should be reflected in the BOLD responses to brief stimuli presented at different phases of the oscillation cycle. We record rhythmic oscillations of V1 BOLD synchronized by a simple voluntary action, in phase with behaviourally measured oscillations in visual sensitivity in the theta range. The functional connectivity between V1 and M1 also oscillates at the same rhythm. By demonstrating oscillatory temporal coupling between primary motor and sensory cortices, our results strongly implicate communication through coherence to achieve precise coordination and to encode sensory-motor timing.

neuroscience↗

bioRxiv2019

A closer look at the timecourse of mind wandering: pupillary responses and behavior

Mind wandering (MW) refers to the shift of attention away from a primary task and/or external environment towards thoughts unrelated to the task. Recent evidence has shown that pupillometry can be used as an objective marker of the onset and maintenance of externally-driven MW episodes. In the present study we aimed to further investigate pupillary changes associated with the onset and duration of self-reported MW episodes. We used a modified version of the joint behavioural-pupillometry paradigm we recently introduced. Participants were asked to perform a monotonous vigilance task which was intermixed with task-irrelevant cue-phrases (visually presented verbal cues); they were instructed to interrupt the task whenever a thought came to mind (self-caught method) and to indicate the trigger of their thought, if any. We found systematic pupil dilation after the presentation of verbal cues reported to have triggered MW, compared with other verbal cues presented during a supposedly on-task period (i.e., the period immediately following the resuming of the task after a self-caught interruption and MW report). These results confirm that pupil diameter is sensitive to the changes associated with the onset of MW and its unfolding over time. Moreover, by computing the latency between the trigger presentation and the task interruption (self-catch), we could also estimate the duration of MW episodes triggered by verbal cues. However, a high variability was found, implying very large inter-event variability, which could not be explained by any of the MW properties we acquired (including: temporal focus, specificity, emotional valence). Our behavioural and pupillometry findings stress the need for objective measures about the temporal unfolding of MW (while most studies focus on arbitrary time-window preceding self-reports of MW).

neuroscience↗

bioRxiv2018

Short-term plasticity of 7T BOLD ocular dominance and spatial frequency representation in adult human primary visual cortex

Visual cortex, particularly V1, is considered to be resilient to plastic changes in adults. In particular, ocular dominance is assumed to be hard-wired after the end of the critical period. We show that short-term (2h) monocular deprivation in adult humans boosts the BOLD response to the deprived eye, changing ocular dominance of V1 vertices, consistently with homeostatic plasticity. The boost is strongest in V1, present in V2, V3 & V4 but absent in V3a and MT. Assessment of spatial frequency tuning in V1 by a population Receptive-Field technique shows that deprivation primarily boosts high spatial frequencies, consistent with a primary involvement of the parvocellular pathway. Crucially, the V1 deprivation effect correlates across participants with the perceptual increase of the deprived eye dominance assessed with binocular rivalry, suggesting a common origin. Our results demonstrate that visual cortex, particularly the ventral pathway, retains a high potential for homeostatic plasticity in the human adult.

neuroscience↗