An fMRI-compatible multi-configurable handheld response system using an intensity-modulated fiber-optic sensor

Impact of Intravesical Cold Sensation on Functional Network Connectivity Estimated Using ICA at Rest & During Interoceptive Task

Afferent nerves that carry interoceptive signals from the viscera to the brain include Aδ and C-fibers. Previously, we examined the effects of detrusor distention (conveyed mainly by Aδ fibers) on the static functional network connectivity (FNC) of the brain using independent component analysis (ICA) of fMRI time series. In the present study, we investigate the impact of intravesical cold sensation (thought to be conveyed by C-fibers) on brain FNC using similar ICA approach. Thirteen healthy women were scanned on a 3.0T MRI scanner during a resting state scan and an intravesical cold sensation task fMRI. High dimensional ICA (n = 75) were used to decompose the fMRI data into several intrinsic connectivity networks (ICNs) including the default-mode (DMN), subcortical (SCN; amygdala, thalamus), salience (SN), central executive (CEN), sensorimotor (SMN), and cerebellar/brainstem (CBN) networks. Results demonstrate significant FNC differences in several ICN pairs primarily between the SCN and cognitive networks such as CEN, as well as between SN and CBN and DMN when intravesical cold water condition was compared to rest (FDR-corrected p-value of 0.05). Significant increases in FNC between CBN and between SMN were also observed during interoceptive condition. The results indicate significant impact of Aδ and C-fiber-originated interoceptive signals on the brain connectivity when compared to the baseline rest.

Design and Application of a New Automated Fluidic Visceral Stimulation Device for Human fMRI Studies of Interoception

Mapping the brain centers that mediate the sensory-perceptual processing of visceral afferent signals arising from the body (i.e., interoception) is useful both for characterizing normal brain activity and for understanding clinical disorders related to abnormal processing of visceral sensation. Here, we report a novel closed-system, electrohydrostatically driven master–slave device that was designed and constructed for delivering controlled fluidic stimulations of visceral organs and inner cavities of the human body within the confines of a 3T magnetic resonance imaging (MRI) scanner. The design concept and performance of the device in the MRI environment are described. In addition, the device was applied during a functional MRI (fMRI) investigation of visceral stimulation related to detrusor distention in two representative subjects to verify its feasibility in humans. System evaluation tests demonstrate that the device is MR-compatible with negligible impact on imaging quality [static signal-to-noise ratio (SNR) loss <2.5% and temporal SNR loss <3.5%], and has an accuracy of 99.68% for flow rate and 99.27% for volume delivery. A precise synchronization of the stimulus delivery with fMRI slice acquisition was achieved by programming the proposed device to detect the 5 V transistor–transistor logic (TTL) trigger signals generated by the MRI scanner. The fMRI data analysis using the general linear model analysis with the standard hemodynamic response function showed increased activations in the network of brain regions that included the insula, anterior and mid-cingulate and lateral prefrontal cortices, and thalamus in response to increased distension pressure on viscera. The translation from manually operated devices to an MR-compatible and MR-synchronized device under automatic control represents a useful innovation for clinical neuroimaging studies of human interoception.

Tracking intrinsic connectivity brain network features during successive (Pseudo-) resting states and interoceptive task fMRI

Advanced multivariate analyses of functional magnetic resonance imaging (fMRI) data based on blood oxygen level-dependent (BOLD) contras have revealed that the human brain organizes its activities into multiple intrinsic connectivity networks (ICNs). Several fMRI studies have evaluated the modulations of these networks during different cognitive or emotional tasks using blind source separation techniques particularly the independent component analysis (ICA). In this exploratory study, we applied ICA methodology to examine ICN modulations under different interoceptive conditions. Fifteen right-handed healthy subjects (age range 21-48 years) underwent a series of eyes-open resting-state and interoceptive task fMRI scans. Using a high-order ICA model, the functional imaging data were decomposed into 75 independent components and 36 were identified as non-artifactual ICNs. ICN spatial modulations were evaluated in terms of the network volume and maximum activations. ICN temporal modulations were assessed based on the power density frequency spectra. Following a false discovery rate multiple comparison correction threshold of ρ <; 0.05, we found significant changes in spatial feature of the attention/cognitive, default-mode, visual and salience networks. More liberal statistical criteria (uncorrected ρ <; 0.05) also indicated differences in network volumes between different states especially involving the sensorimotor, subcortical, cerebellar and brainstem networks. Significant power spectra changes were also found in several attention/cognitive and visual networks as well as the sensorimotor, salience, and subcortical networks especially when resting-states where compared with the interoceptive task fMRI. Further investigations of how interoceptive sensations alter the spatial and temporal features of the human brain networks can elucidate the foundational underpinnings of brain-body relation.

Identifying the effects of visceral interoception on human brain connectome: A multivariate analysis of covariance of fMRI data

Sources of variations in the neural circuitry of the human brain and interrelationship between intrinsic connectivity networks (ICNs) are still a matter of debate and ongoing research. Here, we applied a multivariate analysis of covariance (MANCOVA) based on high-dimensional independent component analysis (ICA) to identify the effects of interoception and related variables on human brain connectome. Fifteen healthy right-handed subjects (all females, age range 21 - 48 years; mean age = 30.3, SD = 8.7 years) underwent a blood-oxygen-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) that included continuous intravesical saline infusion and drainage. The design matrix included the intravesical fullness, subject fullness rating, normalized right and left insula thickness, age, and neuropsychological assessments (Mini-Mental State Exam; MMSE, and Hospital Anxiety and Depression Scale; HADS) as covariates of interest. Univariate tests were also performed with a reduced design matrix (p <; 0.05, corrected for multiple comparisons using false discovery rate) to study the nature and extent of the relationship between these covariates and three ICA outcome measures, namely, the spatial map intensity, frequency spectral power, and functional network connectivity. Results showed significant effects of interoception (intravesical fullness) on spatial map intensity of the salience network (anchored by insula and anterior cingulate cortex) and the frontoparietal central executive network, The left and right insula thickness influenced the spatial map intensity of the subcortical network, and the attention/cognitive and default-mode networks, respectively. The intravesical fullness also showed an effect on the spectral power of the subcortical network. Further investigations of the effect of internal (bodily) sensations on the ICN properties can provide an invaluable tool for understanding the role of interoception in health and illness.

Differential functional brain network connectivity during visceral interoception as revealed by independent component analysis of fMRI TIME-series

Influential theories of brain-viscera interactions propose a central role for interoception in basic motivational and affective feeling states. Recent neuroimaging studies have underlined the insula, anterior cingulate, and ventral prefrontal cortices as the neural correlates of interoception. However, the relationships between these distributed brain regions remain unclear. In this study, we used spatial independent component analysis (ICA) and functional network connectivity (FNC) approaches to investigate time course correlations across the brain regions during visceral interoception. Functional magnetic resonance imaging (fMRI) was performed in thirteen healthy females who underwent viscerosensory stimulation of bladder as a representative internal organ at different prefill levels, i.e., no prefill, low prefill (100 ml saline), and high prefill (individually adapted to the sensations of persistent strong desire to void), and with different infusion temperatures, i.e., body warm (∼37°C) or ice cold (4-8°C) saline solution. During Increased distention pressure on the viscera, the insula, striatum, anterior cingulate, ventromedial prefrontal cortex, amygdalo-hippocampus, thalamus, brainstem, and cerebellar components showed increased activation. A second group of components encompassing the insula and anterior cingulate, dorsolateral prefrontal and posterior parietal cortices and temporal-parietal junction showed increased activity with innocuous temperature stimulation of bladder mucosa. Significant differences in the FNC were found between the insula and amygdalo-hippocampus, the insula and ventromedial prefrontal cortex, and the ventromedial prefrontal cortex and temporal-parietal junction as the distention pressure on the viscera increased. These results provide new insight into the supraspinal processing of visceral interoception originating from an internal organ.

Protocol for a prospective magnetic resonance imaging study on supraspinal lower urinary tract control in healthy subjects and spinal cord injury patients undergoing intradetrusor onabotulinumtoxinA injections for treating neurogenic detrusor overactivity

BACKGROUND

The control of the lower urinary tract is a complex, multilevel process involving both the peripheral and central nervous system. Due to lesions of the neuraxis, most spinal cord injury patients suffer from neurogenic lower urinary tract dysfunction, which may jeopardise upper urinary tract function and has a negative impact on health-related quality of life. However, the alterations to the nervous system following spinal cord injury causing neurogenic lower urinary tract dysfunction and potential effects of treatments such as intradetrusor onabotulinumtoxinA injections on lower urinary tract control are poorly understood.

METHODS/DESIGN

This is a prospective structural and functional magnetic resonance imaging study investigating the supraspinal lower urinary tract control in healthy subjects and spinal cord injury patients undergoing intradetrusor onabotulinumtoxinA injections for treating neurogenic detrusor overactivity.Neuroimaging data will include structural magnetic resonance imaging (T1-weighted imaging and diffusion tensor imaging) as well as functional, i.e. blood oxygen level-dependent sensitive magnetic resonance imaging using a 3 T magnetic resonance scanner. The functional magnetic resonance imaging will be performed simultaneously to three different bladder stimulation paradigms using an automated magnetic resonance compatible and synchronised pump system.All subjects will undergo two consecutive and identical magnetic resonance imaging measurements. Healthy subjects will not undergo any intervention between measurements but spinal cord injury patients will receive intradetrusor onabotulinumtoxinA injections for treating neurogenic detrusor overactivity.Parameters of the clinical assessment including bladder diary, urinalysis, medical history, neuro-urological examination, urodynamic investigation as well as standardised questionnaires regarding lower urinary tract function and quality of life will serve as co-variates in the magnetic resonance imaging analysis.

DISCUSSION

This study will identify structural and functional alterations in supraspinal networks of lower urinary tract control in spinal cord injury patients with neurogenic detrusor overactivity compared to healthy controls. Post-treatment magnetic resonance imaging measurements in spinal cord injury patients will provide further insights into the mechanism of action of treatments such as intradetrusor onabotulinumtoxinA injections and the effect on supraspinal lower urinary tract control.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01768910.

Protocol for a prospective neuroimaging study investigating the supraspinal control of lower urinary tract function in healthy controls and patients with non-neurogenic lower urinary tract symptoms

INTRODUCTION

Lower urinary tract symptoms (LUTS) are highly prevalent, cause an enormous economic burden on healthcare systems and significantly impair the quality of life (QoL) of affected patients. The dependence of the LUT on complex central neuronal circuits makes it unique in comparison to other visceral functions, such as the gastrointestinal tract, but also more vulnerable to neurological diseases.

METHODS AND ANALYSIS

This is a prospective neuroimaging study investigating the supraspinal control of LUT function in healthy controls and in patients with non-neurogenic LUTS. The clinical assessment will include medical history, neuro-urological examination, bladder diary, urine analysis, urodynamic investigations, as well as standardised questionnaires regarding LUTS and QoL. The acquisition of neuroimaging data will include structural assessments (T1-weighted imaging and diffusion tensor imaging) as well as functional investigations using blood-oxygen-level dependent sensitive functional MRI (fMRI) in a 3 T MR scanner. The fMRI will be performed during four different bladder tasks using an automated MR-compatible and MR-synchronised pump system. The first three task-related fMRIs will consist of automated, repetitive filling of 100 mL warm (37°C) saline starting with (1) an empty bladder, (2) a low prefilled bladder volume (100 mL) and (3) a high prefilled bladder volume (persistent desire to void). The fourth task-related fMRI will comprise of automated, repetitive filling of 100 mL cold (4-8°C) saline starting with an empty bladder.

ETHICS AND DISSEMINATION

The local ethics committee approved this study (KEK-ZH-Nr. 2011-0346). The findings of the study will be published in peer-reviewed journals and presented at national and international scientific meetings.

TRIAL REGISTRATION NUMBER

This study has been registered at clinicaltrials.gov (http://www.clinicaltrials.gov/ct2/show/NCT01768910).

Design of an fMRI-compatible optical touch stripe based on frustrated total internal reflection

Previously we developed a low-cost, multi-configurable handheld response system, using a reflective-type intensity modulated fiber-optic sensor (FOS) to accurately gather participants' behavioral responses during functional magnetic resonance imaging (fMRI). Inspired by the popularity and omnipresence of the fingertip-based touch sensing user interface devices, in this paper we present the design of a prototype fMRI-compatible optical touch stripe (OTS) as an alternative configuration. The prototype device takes advantage of a proven frustrated total internal reflection (FTIR) technique. By using a custom-built wedge-shaped optically transparent acrylic prism as an optical waveguide, and a plano-concave lens to provide the required light beam profile, the position of a fingertip touching the surface of the wedge prism can be determined from the deflected light beams that become trapped within the prism by total internal reflection. To achieve maximum sensitivity, the optical design of the wedge prism and lens were optimized through a series of light beam simulations using WinLens 3D Basic software suite. Furthermore, OTS performance and MRI-compatibility were assessed on a 3.0 Tesla MRI scanner running echo planar imaging (EPI) sequences. The results show that the OTS can detect a touch signal at high spatial resolution (about 0.5 cm), and is well suited for use within the MRI environment with average time-variant signal-to-noise ratio (tSNR) loss < 3%.