Reduced betweenness centrality of a sensory-motor vestibular network in subclinical agoraphobia

Agoraphobic patients feel dizzy in crowded open spaces and respond to this symptom with excessive fear and avoidance. These clinical features show great similitude with the newly defined syndrome of persistent postural perceptual dizziness (PPPD). Patients with PPPD show decreased activity and connectivity in regions of the vestibular cortex. Due to the great overlap between these two conditions, we hypothesized that individuals with sub-clinical agoraphobia would show reduction in the connectivity features of these regions. We selected a group of healthy individuals from the Human Connectome Project that self-reported agoraphobia episodes, and compared it with a control group. We accurately matched the two groups for psychological measures and personality traits in order to study the neural correlates of vestibular symptoms independently of possible psychiatric vulnerabilities. We found that the agoraphobia group showed reduced betweenness centrality of a network encompassing key regions of the vestibular cortex. Dysfunctions of the vestibular cortex may explain the dizziness symptom for a disorder previously labelled as psychogenic.

Time-resolved connectome of the five-factor model of personality

The 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.

Structural connectome of the human vestibular, pre-motor, and navigation network<sup/>

The 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.

Dynamic inter-network connectivity in the human brain

Recently, 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

It 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.

Intermolecular double quantum coherences (iDQc) and diffusion-weighted imaging (DWI) imaging of the human brain at 1.5 T

To study the sensitivity of intermolecular double quantum coherences (iDQc) imaging contrast to brain microstructure and brain anisotropy, we investigated the iDQC contrast between differently structured areas of the brain according to the strength and the direction of the applied correlation gradient. Thus diffusion-weighted imaging (DWI) and diffusion tensor imaging (DTI) maps have been obtained. This procedure, which consists of analyzing both iDQc and DWI images at different gradient strength and gradient direction, could be a promising tool for clinical brain investigations performed with higher than 1.5 T magnetic fields.

Real-time quantification of T(2)(*) changes using multiecho planar imaging and numerical methods

Conventional approaches to quantify whole brain T(2)(*) maps use nonlinear regression with intensive computational requirements that therefore likely limit quantitative T(2)(*) mapping for real-time applications. To overcome these limitations an alternative method, NumART(2)(*) (NUMerical Algorithm for Real-time T(2)(*) mapping) that directly calculates T(2)(*) by a linear combination of images obtained at three or more different echo times was developed. NumART(2)(*), linear least-squares, and nonlinear regression techniques were applied to multiecho planar images of the human brain and to simulated data. Although NumART(2)(*) may overestimate T(2)(*), it yields comparable values to regression techniques in cortical and subcortical areas, with only moderate deviations for echo spacings between 18 and 40 ms. NumART(2)(*), like linear regression, requires 2% of the computational time needed for nonlinear regression and compares favorably with linear regression due to its higher precision. The use of NumART(2)(*) for continuous on-line T(2)(*) mapping in real time fMRI studies is shown.

In vivo multiple spin echoes imaging of trabecular bone on a clinical 1.5 T MR scanner

In vivo multiple spin echoes (MSE) images of bone marrow in trabecular bone were obtained for the first time on a clinical 1.5 T scanner. Despite of a reduced sensitivity of the MSE trabecular bone images with respect to the cerebral matter ones, it is possible to observe some features in the MSE trabecular bone images that may be useful in the diagnosis of osteopenic states. Two different CRAZED-type MSE imaging sequences based on spin-echo and EPI imaging modalities were applied in phantom and in vivo. Preliminary experimental results indicate that EPI imaging readout seems to conceal the MSE contrast correlated with pore dimension in porous media. However it is still possible to detect anisotropy effects related to the bone structure in MSE-EPI images. Some strategies are suggested to optimize the quality of MSE trabecular bone images.

Combined visual attention and finger movement effects on human brain representations

Sensory and motor systems interact in complex ways; visual attention modifies behavior, neural encoding, and brain activation; and dividing attention with simultaneous tasks may impede performance while producing specific brain activation patterns. We hypothesized that combining voluntary movement with visual attention would yield unique brain representations differing from those occurring for movement or visual attention alone. Hemodynamic signals in humans were obtained with functional magnetic resonance imaging (MRI) while participants performed one of four tasks that required only a repetitive finger movement, only attending to the color of a visual stimulus, simultaneous finger movement and visual attention, or no movement and no visual attention. The movement-alone task yielded brain activation in structures commonly engaged during voluntary movement, including the primary motor cortex, supplementary motor area, and cerebellum. Visual attention alone resulted in sparse cerebral cortical and substantial bilateral cerebellar activation. Simultaneous performance of visual attention and finger movements yielded widespread cerebral cortical, cerebellar, and other subcortical activation, in many of the same sites activated for the movement or attention tasks. However, the movement-related plus attention-related activation extended beyond the movement-alone or attention-alone activation sites, indicating a novel activation pattern related to the combined performance of attention and movement. Additionally, the conjoint effects of visual attention and movement upon brain activation were probably not simple gain effects, since we found activation-related interactions in the left superior parietal lobule, the right fusiform gyrus, and left insula, indicating a potent combinatory role for visual attention and movement for activation patterns in the human brain. In conclusion, performing visual attention and movement tasks simultaneously, even though the tasks had no specific interrelationship, resulted in novel activation patterns not predicted by performing movements or visual attention alone.

On somatotopic representation centers for finger movements in human primary motor cortex and supplementary motor area

We used functional magnetic resonance imaging to examine the representation pattern for repetitive voluntary finger movements in the primary motor cortex (M1) and the supplementary motor area (SMA) of humans. Healthy right-handed participants performed repetitive individuated flexion-extension movements of digits 1, 2, and 3 using the dominant hand. Contralateral functional labeling for the group indicated a largely overlapping activation pattern in M1 and SMA for the three digits. Consistent with recent findings, the geographic activation center in M1 for each finger differed, and we found some evidence of a homunculus organization pattern in M1 and SMA, but only for the central location of the representations. However, the statistical power for the homunculus pattern was weak, and the distance separating the digit geographical centers was typically less than 15% of the entire extent of digit representations in M1 or SMA. While separations for digit representations occurred, the entire data set provided more support for the concept of distributed, overlapping representations than for a classic homunculus organization for voluntary finger movements.

Tonotopic cortical changes following stapes substitution in otosclerotic patients: a magnetoencephalographic study

The aim of the study was to investigate and follow up the tonotopic organization of the primary auditory cortex in otosclerotic patients before and after corrective surgery. The characteristics of primary auditory cortex activation were studied in ten otosclerotic patients (i.e., subjects suffering from a conductive hearing loss, prior to and following stapes substitution). Magnetoencephalographic recordings of auditory evoked fields by tone-burst stimulation at octave frequencies between 250 and 2000 Hz were performed during monaural stimulation. The brain topography of the main cortical response (N100m) generators at different tones was studied in patients and compared with ten healthy controls; pre- post-surgical changes were also correlated to their clinical outcome following corrective surgery. A significant decrease of the tonotopic extension in the cortical region responsive to the four explored frequencies was found in patients before surgery with respect to the control population. At the time of postsurgical follow-up, the tonotopic representation had enlarged and was approaching the dimensions seen in normal subjects, although with higher variability. The extent of the enlargement of the postoperative tonotopically organized area was directly correlated with the postsurgery period duration. Our findings indicate that auditory cortical areas of human adults undergo functional reorganization following peripheral alteration of the sensory input entering the CNS. The restriction of the cortical tonotopic region caused by the long-term reduction of acoustic input is followed by a reorganization within the usual boundaries following the recovery of auditory function; this process is taking place in a time scale of a few weeks.

Bilateral neuromagnetic activation of human primary sensorimotor cortex in preparation and execution of unilateral voluntary finger movements

Extracranial magnetoencephalographic activity was separately recorded (25 channels) from bilateral primary sensorimotor cortex (M1-S1) of normal right-handers during unilateral finger movements. Standard dipole analysis indicated only a contralateral M1-S1 source for first movement-evoked field (MEF1) peaking at about 115 ms after electromyographic onset. However, the subtraction of the magnetic field generated by this source from the recorded magnetic field disclosed a low-amplitude ipsilateral central-parietal MEF1 that was explained by an ipsilateral M1-S1 source.

[General systems theory, analog models and essential arterial hypertension]

The application of the General System Theory to the fields of biology and particularly of medicine is fraught with many difficulties deriving from the mathematical complexities of application. The authors suggest that these difficulties can be overcome by applying analogical models, thus opening new prospects for the resolution of the manifold problems involved in connection with the study of arterial hypertension.

[Correlation between thyroid hypofunction and the presence of circulating antithyroid microsomal antibodies. A phenomenon in the aged, prevalent in women]

The authors evaluated the existence of serum thyroid microsomal antibodies (anti-TMS) and their correlation, if any, with thyroid function in a group of 120 consecutive patients, who seemed clinically worthy to be studied from that point of view, even if they were lacking of a previous laboratory framing. Present study shows a consistent prevalence (81.8%) of anti-TMS concentrations were not related with any hormone parameter of thyroid function. Instead, the prevalence of anti-TMS positive subjects get to 69% in the 39 over-65 aged patients (32 women) of survey, with a concordance between high anti-TMS concentration and hypothyroidism of 87.5% in the subgroup. In these elderly patients circulating anti-TMS and serum TSH were found directly correlated (p less than 0.001), whereas serum FT4 was found in inverse correlation with the same antibodies (p less than 0.01). The consistent share of hypothyroid-aging patients, although mild or subclinical but clearly related with immunological phenomena, cannot be overlooked.

[Effect of polyunsaturated phosphatidylcholine and vitamin B complex on the metabolism of selenium homotaurocholic acid in patients with chronic liver disease]

SeHCAT, a synthetic homologue of thaurocolic acid, may be used to examine the dynamics of enterohepatic circulation. A greater retention of SeHCAT may be attributed to a defective hepatic clearance and to a partial redistribution of the biliary acid pool outside the enterohepatic circle. This method has been applied to 20 patients affected with chronic hepatic disorders. The percentage of retention of SeHCAT in normal subjects was 19-20 on average. The hepatopathic patient has an average SeHCAT retention of 54%. After treatment with polyunsaturated phosphatidylcholine (EPL) plus vitamin B complex i.v., the percentage of SeHCAT retention was significantly less than 31% (P less than 0.001). It can be hypothesized that the drug determines an improvement of the enterohepatic circle (acting on the hepatic clearance) in patients with chronic hepatic disorders as shown by the reduction of the percentage of SeHCAT retention noticed.

[Evaluation of the parameters used in monitoring hypothyroid patients treated with L-thyroxine]

Hormonal and clinical data on 38 tests performed in 7 hypothyroid patients given substitutive treatment with L-thyroxin were analysed. The aim of the survey was to assess the dependability of the various parameters used to estimate dose adequacy in substitutive treatment. Examination of individual cases revealed that overdoses of thyroxin increased T4 to above normal limits without increases in T3, FT3, FT4 or hypophyseal suppression. Chronological discrepancies between clinical data and normal parameters were also noted. However on the data as a whole significant correlations were noted between T4 and TSH (p less than 0.001), between T4 and delta-TSH (p less than 0.001), between T3 and TSH p less than 0.01), between FT3 and delta-TSH (p less than 0.01), between FT4 and delta-TSH (p less than 0.01). FT4 and delta-TSH were also significantly correlated (p less than 0.02) with the Billewicz clinical index of hypothyroidism. It is concluded that the clinical and hormonal data in treated hypothyroid cases have the same significance as in normal or untreated hypothyroid cases. However, it must be borne in mind that unusual relations between the various thyroid hormone fractions including TSH and the standardised clinical examination may arise while doses are being established. In this case the data cannot be automatically interpreted but merely carefully assessed in the light of experience.

[Hepatic clearance of 99mTc-p-butyl HIDA in liver diseases. Correlations with routine hematochemical parameters of liver function]

The aim of the present investigation was to study the clearance of 99mTc-p-butyl IDA in some acute and chronic liver diseases, it being considered that the typical parameters obtained with this method are as indicative as any of the others put forward for the study of liver function using radioisotopes. 46 subjects were examined: 6 with acute hepatitis, 10 with chronic hepatitis, 18 with liver cirrhosis and 12 with dyspepsia but otherwise normal haematochemical tests. Two basic 99mTc-p-butyl IDA clearance parameters, Tu (semi-take up time) and Te (semi-excretion time), were determined plotting the data obtained using a Gamma-Camera on semi-logarithmic paper. Mean Tu values were as follows: 5'06'' +/- 1'24'' in dyspeptics, 12'30'' +/- 6'31'' in subjects with acute hepatitis, 6'30'' +/- 1'45'' in subjects with chronic hepatitis and 13'30'' +/- 4'30'' in subjects with cirrhosis. The values were: 34'30'' +/- 4'30'' in dyspeptics, 49'54'' +/- 2'36'' in subjects with acute hepatitis, 42'24'' +/- 12'24'' in subjects with chronic hepatitis and 65'30'' +/- 39'36'' in subjects with cirrhosis. The Tu parameter was found to be delayed more significantly in cirrhotic patients and less in subjects with acute or chronic hepatitis, compared to dyspeptics with normal haematochemical parameters. Te was significantly delayed in subjects with cirrhosis and acute hepatitis, while there was no difference for subjects with chronic hepatitis. Of the routine haematochemical tests, the albumin/gamma-globulin ratio and unconjugated bilirubin were found to correlate significantly with the Tu parameter, whereas conjugated bilirubin was found to bear a significant correlation to the Te parameter.