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Altered Autonomic Response in Patients with Persistent Postural-Perceptual Dizziness during Simulated Vertical Self-Motion
No full textPersistent postural-perceptual dizziness (PPPD) is a chronic psychosomatic condition characterized by dizziness, unsteadiness, and swaying or rocking vertigo. Despite the well-known relationship between the autonomic nervous system (ANS) and the vestibular system ANS, involvement in PPPD has not yet been investigated. We studied HRV in fifteen patients with PPPD and fifteen healthy controls (HCs), during a virtual reality task that simulated self-motion in horizontal and vertical directions with different kinematic conditions (accelerated, decelerated, constant), to elicit vestibular stimulation via kinematic visual inputs. Subject, condition-, direction, kinematic- and trial- specific HRV indices values were compared through mixed models. In PPPD patients (as compared to HC), we observed a) lower parasympathetic tone (p<0.001), lower variability of parasympathetic tone (p<0.02) higher sympathovagal balance (p<0.001). We also observed lower variability of parasympathetic tone in vertical motion as opposed to horizontal motion (p=0.03). Our findings are consistent with the hypothesis that PPPD, like many other psychosomatic conditions, alters the physiological regulation of the ANS. This, in turn, might impact on the processing of gravity and balance-related signal and lead to the characteristic symptoms of PPPD. The reverse scenario (i.e., that pre-existing ANS dysfunctions drive abnormalities in the visuo-vestibular system and leads to PPPD) is equally likely
Brain responses to virtual reality visual motion stimulation are affected by neurotic personality traits in patients with persistent postural-perceptual dizziness
No full textOBJECTIVE: Persistent postural perceptual dizziness (PPPD) is a common vestibular disorder of persistent dizziness and unsteadiness, exacerbated by upright posture, self-motion, and exposure to complex or moving visual stimuli. Previous functional magnetic resonance imaging (fMRI) studies found dysfunctional activity in the visual-vestibular cortices in patients with PPPD. Clinical studies showed that the anxiety-related personality traits of neuroticism and introversion may predispose individuals to PPPD. However, the effects of these traits on brain function in patients with PPPD versus healthy controls (HCs) have not been studied. METHODS: To investigate potential differential effects of neuroticism and introversion on functioning of their visuovestibular networks, 15 patients with PPPD and 15 HCs matched for demographics and motion sickness susceptibility underwent fMRI during virtual reality simulation of a rollercoaster ride in vertical and horizontal directions. RESULTS: Neuroticism positively correlated with activity in the inferior frontal gyrus (IFg), and enhanced connectivity between the IFg and occipital regions in patients with PPPD relative to HCs during vertical versus horizontal motion comparison. CONCLUSIONS: In patients with PPPD, neuroticism increased the activity and connectivity of neural networks that mediate attention to visual motion cues during vertical motion. This mechanism may mediate visual control of balance in neurotic patients with PPPD
Personality traits modulate subcortical and cortical vestibular and anxiety responses to sound-evoked otolithic receptor stimulation
No full textStrong links between anxiety, space-motion perception, and vestibular symptoms have been recognized for decades. These connections may extend to anxiety-related personality traits. Psychophysical studies showed that high trait anxiety affected postural control and visual scanning strategies under stress. Neuroticism and introversion were identified as risk factors for chronic subjective dizziness (CSD), a common psychosomatic syndrome. This study examined possible relationships between personality traits and activity in brain vestibular networks for the first time using functional magnetic resonance imaging (fMRI)
Structural connectome of the human vestibular, pre-motor, and navigation network
No full textThe aim of this study is to characterize modules
and hubs within the multimodal vestibular system and,
particularly, to test the centrality of posterior peri-sylvian
regions. Structural connectivity matrices from 50 unrelated
healthy right-handed subjects from the Human Connectome
Project (HCP) database were analyzed using multishell
diffusion-weighted data, probabilistic tractography
(constrained spherical-deconvolution informed filtering of
tractograms) in combination with subject-specific grey matter
parcellations. Network nodes included parcellated regions
within the vestibular, pre-motor and navigation system.
Module calculation produced two and three modules in the
right and left hemisphere, respectively. On the right, regions
were grouped into a vestibular and pre-motor module, and into
a visual-navigation module. On the left this last module was
split into an inferior and superior component. In the thalamus,
a region comprising the mediodorsal and anterior complex, and
lateral and inferior pulvinar, was included in the ipsilateral
navigation module, while the remaining thalamus was clustered
with the ipsilateral vestibular pre-motor module. Hubs were
located bilaterally in regions encompassing the inferior parietal
cortex and the precuneus. This analysis revealed a dorso-lateral
path within the multi-modal vestibular system related to
vestibular / motor control, and a ventro-medial path related to
spatial orientation / navigation. Posterior peri-sylvian regions
may represent the main hubs of the whole modular network
Surface-based morphometry reveals the neuroanatomical basis of the five-factor model of personality.
Get PDFThe five-factor model (FFM) is a widely used taxonomy of human personality; yet its neuro anatomical basis remains unclear. This is partly because past associations between gray-matter volume and FFM were driven by different surface-based morphometry (SBM) indices (i.e. cortical thickness, surface area, cortical folding or any combination of them). To overcome this limitation, we used Free-Surfer to study how variability in SBM measures was related to the FFM in n = 507 participants from the Human Connectome Project.Neuroticism was associated with thicker cortex and smaller area and folding in prefrontal-temporal regions. Extraversion was linked to thicker pre-cuneus and smaller superior temporal cortex area. Openness was linked to thinner cortex and greater area and folding in prefrontal-parietal regions. Agreeableness was correlated to thinner prefrontal cortex and smaller fusiform gyrus area. Conscientiousness was associated with thicker cortex and smaller area and folding in prefrontal regions. These findings demonstrate that anatomical variability in prefrontal cortices is linked to individual differences in the socio-cognitive dispositions described by the FFM. Cortical thickness and surface area/folding were inversely related each others as a function of different FFM traits (neuroticism, extraversion and consciousness vs openness), which may reflect brain maturational effects that predispose or protect against psychiatric disorders
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Time-resolved connectome of the five-factor model of personality.
Get PDFThe human brain is characterized by highly dynamic patterns of functional connectivity. However, it is unknown whether this time-variant 'connectome' is related to the individual differences in the behavioural and cognitive traits described in the five-factor model of personality. To answer this question, inter-network time-variant connectivity was computed in n = 818 healthy people via a dynamical conditional correlation model. Next, network dynamicity was quantified throughout an ad-hoc measure (T-index) and the generalizability of the multi-variate associations between personality traits and network dynamicity was assessed using a train/test split approach. Conscientiousness, reflecting enhanced cognitive and emotional control, was the sole trait linked to stationary connectivity across several circuits such as the default mode and prefronto-parietal network. The stationarity in the 'communication' across large-scale networks offers a mechanistic description of the capacity of conscientious people to 'protect' non-immediate goals against interference over-time. This study informs future research aiming at developing more realistic models of the brain dynamics mediating personality differences
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Dynamic inter-network connectivity in the human brain
No full textRecently, the field of functional brain connectivity has shifted its attention on studying how functional connectivity (FC) between remote regions changes over time. It is becoming increasingly evident that the human 'connectome' is a dynamical entity whose variations are effected over very short timescales and reflect crucial mechanisms which underline the physiological functioning of the brain. In this study, we employ ad-hoc statistical and surrogate data generation methods to quantify whether and which brain networks displayed dynamic behaviors in a very large sample of healthy subjects provided by the human connectome project (HCP). our findings provided evidences that there are specific pairs of networks and specific networks within the healthy brain that are more likely to display dynamic behaviors. this new set of findings supports the notion that studying the time-variant connectivity in the brain could reveal useful and important properties about brain functioning in health and disease
Dynamical brain connectivity estimation using GARCH models: An application to personality neuroscience
No full textIt has recently become evident that the functional connectome of the human brain is a dynamical entity whose time evolution carries important information underpinning physiological brain function as well as its disease-related aberrations. While simple sliding window approaches have had some success in estimating dynamical brain connectivity in a functional MRI (fMRI) context, these methods suffer from limitations related to the arbitrary choice of window length and limited time resolution. Recently, Generalized autoregressive conditional heteroscedastic (GARCH) models have been employed to generate dynamical covariance models which can be applied to fMRI. Here, we employ a GARCH-based method (dynamic conditional correlation -DCC) to estimate dynamical brain connectivity in the Human Connectome Project (HCP) dataset and study how the dynamic functional connectivity behaviors related to personality as described by the five-factor model. Openness, a trait related to curiosity and creativity, is the only trait associated with significant differences in the amount of time-variability (but not in absolute median connectivity) of several inter-network functional connections in the human brain. The DCC method offers a novel window to extract dynamical information which can aid in elucidating the neurophysiological underpinning of phenomena to which conventional static brain connectivity estimates are insensitive
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