Neural Correlates of Body Integrity Dysphoria

There are few things as irrefutable as the evidence that our limbs belong to us. However, persons with body integrity dysphoria (BID) [1] deny the ownership of one of their fully functional limbs and seek its amputation [2]. We tapped into the brain mechanisms of BID, examining sixteen men desiring the removal of the left healthy leg. The primary sensorimotor area of the to-be-removed leg and the core area of the conscious representation of body size and shape (the right superior parietal lobule [rSPL]) [3, 4] were less functionally connected to the rest of the brain. Furthermore, the left premotor cortex, reportedly involved in the multisensory integration of limb information [5-7], and the rSPL were atrophic. The more atrophic the rSPL, the stronger the desire for amputation, and the more an individual pretended to be an amputee by using wheelchairs or crutches to solve the mismatch between the desired and actual body. Our findings illustrate the pivotal role of the connectivity of the primary sensorimotor limb area in the mediation of the feeling of body ownership. They also delineate the morphometric and functional alterations in areas of higher-order body representation possibly responsible for the dissatisfaction with a standard body configuration. The neural correlates of BID may foster the understanding of other neuropsychiatric disorders involving the bodily self. Ultimately, they may help us understand what most of us take for granted, i.e., the experience of body and self as a seamless unity

Brain Abnormalities in Individuals with a Desire for a Healthy Limb Amputation: Somatosensory, Motoric or Both? A Task-Based fMRI Verdict

Body integrity dysphoria (BID), a long-lasting desire for the amputation of physically healthy limbs, is associated with reduced fMRI resting-state functional connectivity of somatosensory cortices. Here, we used fMRI to evaluate whether these findings could be replicated and expanded using a task-based paradigm. We measured brain activations during somatosensory stimulation and motor tasks for each of the four limbs in ten individuals with a life-long desire for the amputation of the left leg and fourteen controls. For the left leg, BID individuals had reduced brain activation in the right superior parietal lobule for somatosensory stimulation and in the right paracentral lobule for the motor task, areas where we previously found reduced resting-state functional connectivity. In addition, for somatosensory stimulation only, we found a robust reduction in activation of somatosensory areas SII bilaterally, mostly regardless of the stimulated body part. Areas SII were regions of convergent activations for signals from all four limbs in controls to a significantly greater extent than in subjects with BID. We conclude that BID is associated with altered integration of somatosensory and, to a lesser extent, motor signals, involving limb-specific cortical maps and brain regions where the first integration of body-related signals is achieved through convergence

The balance of feelings: vestibular modulation of bodily sensations.

The vestibular system processes information about head movement and orientation. No unimodal vestibular cortex has been identified in the mammalian brain. Rather, vestibular inputs are combined with many other sensory signals in the cortex. This arrangement suggests that vestibular input could influence processing in other sensory modalities. Here we show that vestibular stimulation differentially modulates two submodalities of the somatosensory system, increasing sensitivity to tactile input, and independently reducing sensitivity to nociceptive input. These modulations of touch and pain can clearly be distinguished from supramodal attentional effects of vestibular stimulation, because they are bilateral and operate in different directions. Outside the artificial conditions of laboratory stimulation, the vestibular system codes movements of the head, indicating a new relation between the body and the external world. We suggest the vestibular system participates in a form of sensory signal management, changing the balance between the various sensory systems as the relation between the body and the external environment changes. This sensory rebalancing may be a crucial element in the brain's capacity to reorient towards novel or salient features in the environment

How the vestibular system interacts with somatosensory perception: A sham-controlled study with galvanic vestibular stimulation

The vestibular system has widespread interactions with other sensory modalities. Here we investigate whether vestibular stimulation modulates somatosensory function, by assessing the ability to detect faint tactile stimuli to the fingertips of the left and right hand with or without galvanic vestibular stimulation (GVS). We found that left anodal and right cathodal GVS, significantly enhanced sensitivity to mild shocks on either hand, without affecting response bias. There was no such effect with either right anodal and left cathodal GVS or sham stimulation. Further, the enhancement of somatosensory sensitivity following GVS does not strongly depend on the duration of GVS, or the interval between GVS and tactile stimulation. Vestibular inputs reach the somatosensory cortex, increasing the sensitivity of perceptual circuitry

The VIMOS Public Extragalactic Redshift Survey (VIPERS) : The decline of cosmic star formation: quenching, mass, and environment connections

RT acknowledges financial support from the European Research Council through grant n. 202686.We use the final data of the VIMOS Public Extragalactic Redshift Survey (VIPERS) to investigate the effect of the environment on the evolution of galaxies between z = 0.5 and z = 0.9. We characterise local environment in terms of the density contrast smoothed over a cylindrical kernel, the scale of which is defined by the distance to the fifth nearest neighbour. This is performed by using a volume-limited sub-sample of galaxies complete up to z = 0.9, but allows us to attach a value of local density to all galaxies in the full VIPERS magnitude-limited sample to i < 22.5. We use this information to estimate how the distribution of galaxy stellar masses depends on environment. More massive galaxies tend to reside in higher-density environments over the full redshift range explored. Defining star-forming and passive galaxies through their (NUV-r) vs. (r-K) colours, we then quantify the fraction of star-forming over passive galaxies, fap, as a function of environment at fixed stellar mass. fap is higher in low-density regions for galaxies with masses ranging from log (M/M⊙) = 10.38 (the lowest value explored) to at least log (M/M⊙) ~ 11.3, although with decreasing significance going from lower to higher masses. This is the first time that environmental effects on high-mass galaxies are clearly detected at redshifts as high as z ~ 0.9. We compared these results to VIPERS-like galaxy mock catalogues based on a widely used galaxy formation model. The model correctly reproduces fap in low-density environments, but underpredicts it at high densities. The discrepancy is particularly strong for the lowest-mass bins. We find that this discrepancy is driven by an excess of low-mass passive satellite galaxies in the model. In high-density regions, we obtain a better (although not perfect) agreement of the model fap with observations by studying the accretion history of these model galaxies (that is, the times when they become satellites), by assuming either that a non-negligible fraction of satellites is destroyed, or that their quenching timescale is longer than ~ 2 Gyr.PostprintPeer reviewe

The VIMOS Public Extragalactic Redshift Survey (VIPERS). Downsizing of the blue cloud and the influence of galaxy size on mass quenching over the last eight billion years

R.T. acknowledges financial support from the European Research Councilthrough grant No. 202686.We use the full VIPERS redshift survey in combination with SDSS-DR7 to explore the relationships between star-formation history (using d4000), stellar mass and galaxy structure, and how these relationships have evolved since z ~ 1. We trace the extents and evolutions of both the blue cloud and red sequence by fitting double Gaussians to the d4000 distribution of galaxies in narrow stellar mass bins, for four redshift intervals over 0 < z < 1. This reveals downsizing in star formation, since the high-mass limit of the blue cloud has retreated steadily from time from ℳ ~ 1011.2 M⊙ at z ~ 0.9 to ℳ ~ 1010.7 M⊙ to the present day. The number density of massive blue-cloud galaxies (ℳ ~ 1011 M⊙, d4000 < 1.55) drops sharply by a factor five between z ~ 0.8 and z ~ 0.5. These galaxies are becoming quiescent at a rate that largely matches  the increase in the numbers of massive passive galaxies seen over this period. We examine the size-mass relation of blue-cloud galaxies,  finding that its high-mass boundary runs along lines of constant ℳ /re or equivalently inferred velocity dispersion. Larger galaxies can continue to form stars to higher stellar masses than smaller galaxies. As  blue-cloud galaxies approach this high-mass limit, entering a narrow diagonal region within the size-mass plane termed the “quenching zone”, they start to be quenched, their d4000 values increasing to push them towards the green valley. In parallel, their structures change, showing higher Sérsic indices and central stellar mass densities. For these galaxies, bulge growth is required for them to reach the high-mass limit of the blue cloud and be quenched by internal mechanisms. The blue-cloud galaxies that are being quenched at z ~ 0.8 lie along the same size-mass relation as present day quiescent galaxies and seem the likely progenitors of today’s S0s.Publisher PDFPeer reviewe

Caloric vestibular stimulation modulates nociceptive evoked potentials

Vestibular stimulation has been reported to alleviate central pain. Clinical and physiological studies confirm pervasive interactions between vestibular signals and somatosensory circuits, including nociception. However, the neural mechanisms underlying vestibular-induced analgesia remain unclear, and previous clinical studies cannot rule out explanations based on alternative, non-specific effects such as distraction or placebo. To investigate how vestibular inputs influence nociception, we combined caloric vestibular stimulation (CVS) with psychophysical and electrocortical responses elicited by nociceptive-specific laser stimulation in humans (laser-evoked potentials, LEPs). Cold water CVS applied to the left ear resulted in significantly lower subjective pain intensity for experimental laser pain to the left hand immediately after CVS, relative both to before CVS and to 1 h after CVS. This transient reduction in pain perception was associated with reduced amplitude of all LEP components, including the early N1 wave reflecting the first arrival of nociceptive input to primary somatosensory cortex. We conclude that cold left ear CVS elicits a modulation of both nociceptive processing and pain perception. The analgesic effect induced by CVS could be mediated either by subcortical gating of the ascending nociceptive input, or by direct modulation of the primary somatosensory cortex

Beyond the Non-Specific Attentional Effect of Caloric Vestibular Stimulation: Evidence from Healthy Subjects and Patients

Caloric vestibular stimulation (CVS) is a simple physiological manipulation that has been used for a long time in different clinical fields due to its rapid and relevant effects on behaviour. One of the most debated issues in this research field concerns the degree of specificity of such stimulation, namely whether the effects of CVS can be, and to what extent are, independent of the mere influence of non-specific factors such as general arousal, ocular movements or attentional shift towards the stimulated side. The hypothesis that CVS might cause a shift of attention towards the side of the stimulation has been largely supported; moreover, a large amount of evidence is available nowadays to corroborate the specific effect of CVS, providing behavioural and neurophysiological data in both patients and normal subjects. These data converge in indicating that the effects of CVS can be independent of eye deviation and general arousal, can modulate different symptoms in different directions, and do not merely depend on a general shift of attention. The present article is divided into three main sections. In the first section, we describe classical studies that investigate the effects of CVS on neglect and related symptoms. In the second and third parts, we provide an overview of the modulatory effects of CVS on somatosensory processes and body representation in both brain-damaged patients and healthy subjects. Finally, we conclude by discussing the relevance of these new findings for the understanding of the neural mechanisms underlying the modulatory effects of CVS