Human Functional Brain Imaging Research Articles

Scalp attached tangential magnetoencephalography using tunnel magneto-resistive sensors

Non-invasive human brain functional imaging with millisecond resolution can be achieved only with magnetoencephalography (MEG) and electroencephalography (EEG). MEG has better spatial resolution than EEG because signal distortion due to inhomogeneous head conductivity is negligible in MEG but serious in EEG. However, this advantage has been practically limited by the necessary setback distances between the sensors and scalp, because the Dewar vessel containing liquid helium for superconducting quantum interference devices (SQUIDs) requires a thick vacuum wall. Latest developments of high critical temperature (high-Tc) SQUIDs or optically pumped magnetometers have allowed closer placement of MEG sensors to the scalp. Here we introduce the use of tunnel magneto-resistive (TMR) sensors for scalp-attached MEG. Improvement of TMR sensitivity with magnetic flux concentrators enabled scalp-tangential MEG at 2.6 mm above the scalp, to target the largest signal component produced by the neural current below. In a healthy subject, our single-channel TMR-MEG system clearly demonstrated the N20m, the initial cortical component of the somatosensory evoked response after median nerve stimulation. Multisite measurement confirmed a spatially and temporally steep peak of N20m, immediately above the source at a latency around 20 ms, indicating a new approach to non-invasive functional brain imaging with millimeter and millisecond resolutions.

Human song: Separate neural pathways for melody and speech

Does the brain perceive song as speech with melody? A new study using intracranial recordings and functional brain imaging in humans suggests that it does not. Instead, singing, instrumental music, and speech are represented by different neural populations.

The Brain Understands Social Relationships: The Emerging Field of Functional-Connectome-Based Interpersonal Research

Human functional brain imaging research over the last 2 decades has shown that data from resting-state brain activity can help predict various psychological and pathological variables and brain function during tasks. However, most variables have been attributed to the individual brain. Recently, several studies have aimed to understand interpersonal relationships based on inter-individual similarity or dissimilarity of functional connectome. In this commentary, we introduce the studies that have opened up a new era of interpersonal research using human brain imaging.

Abstract 4733: Human functional brain imaging data support preclinical and clinical evidence that marizomib crosses the blood-brain barrier (BBB) to inhibit proteasome activity in the brain

Abstract Background: Here we summarize key data suggesting, unlike bortezomib, marizomib (MRZ), an irreversible inhibitor of all proteasome subunits, crosses the BBB, supporting its evaluation in brain malignancies. Methods: Male Swiss Webster mice with microdialysis probes implanted in the cerebellum (CER) and prefrontal cortex (PFC) were administered MRZ (0.3 mg/kg IV, n = 15), amphetamine (1 mg/kg IP, positive control, n = 4), or vehicle (n = 6). Neurotransmitter levels were measured up to 180 minutes post-dose. Brain samples were collected from MRZ-treated mice at 30, 60, 120 (n = 3 each) and 180 (n = 6) minutes post-dose to determine proteasome activity (chymotrypsin-like [CT-L], trypsin-like [T-L], and caspase-like [C-L] subunits). Proteasome activity was assessed in normal human brain (CER and frontal lobe; n = 6) and glioblastoma tumor samples (GBM; n = 30), and in peripheral blood mononuclear cells (PBMCs) from patients with recurrent GBM (rGBM) prior to and after MRZ administration (MRZ-108 study, NCT02330562). Longitudinal resting-state functional magnetic resonance imaging (fMRI) of whole-brain volumes was acquired before and after MRZ administration to patients with rGBM (n = 6). Results: In mice, MRZ significantly increased 3,4-Dihydroxyphenylacetic acid (DOPAC) and dopamine levels in the CER and decreased levels of serotonin (CER and PFC), 5-Hydroxyindoleacetic acid (CER and PFC), Homovanillic acid (PFC), and DOPAC (PFC). Proteasome activity of all 3 proteasome subunits (CT-L, C-L, T-L) was significantly reduced in mouse CER and PFC after MRZ administration; CT-L activity was most potently inhibited. In humans, similar CT-L and C-L activity levels were observed in GBM tumor tissue compared with normal brain CER, while activity levels were 3- to 4-fold higher in normal brain frontal lobe. In patients with rGBM, CT-L activity in PBMCs was inhibited 80-100% 1 hour post-MRZ, however, activity levels had returned to baseline prior to the next MRZ infusion 7 days later. Resting-state fMRI data showed, after MRZ exposure, hallucination severity was associated with decreased functional connectivity between left lingual gyrus and both left CER (T[4] = −12.78; P < 0.03 FDR) and left temporal cortex (T[4] = −9.56; P < 0.04 FDR). Conclusions: MRZ demonstrated rapid, yet transient proteasome inhibition in PBMCs. This activity pattern may be related to proteasome turnover and occur in other nucleated cells, such as glioma cells. Lower proteasome activity levels were observed in CER and GBM tumor tissue compared with frontal lobe tissue. Proteasome inhibition and neurotransmitter level alterations in the mouse brain and functional connectivity changes in the human brain suggest that MRZ crosses the BBB and specifically affects the CER. Taken together, these data suggest GBM tumor tissue, like the CER, may be sensitive to MRZ treatment. Citation Format: Daniela A. Bota, Kaijun Di, David B. Keator, Robert G. Bota, Matthew Hoffmann, C. Dan Dumitru, Nancy Levin. Human functional brain imaging data support preclinical and clinical evidence that marizomib crosses the blood-brain barrier (BBB) to inhibit proteasome activity in the brain [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4733.

Altered neural activity in brain cough suppression networks in cigarette smokers.

Cough is important for airway defence, and studies in healthy animals and humans have revealed multiple brain networks intimately involved in the perception of airway irritation, cough induction and cough suppression. Changes in cough sensitivity and/or the ability to suppress cough accompany pulmonary pathologies, suggesting a level of plasticity is possible in these central neural circuits. However, little is known about how persistent inputs from the lung might modify the brain processes regulating cough.In the present study, we used human functional brain imaging to investigate the central neural responses that accompany an altered cough sensitivity in cigarette smokers.In nonsmokers, inhalation of the airway irritant capsaicin induced a transient urge-to-cough associated with the activation of a distributed brain network that included sensory, prefrontal and motor cortical regions. Cigarette smokers demonstrated significantly higher thresholds for capsaicin-induced urge-to-cough, consistent with a reduced sensitivity to airway irritation. Intriguingly, this was accompanied by increased activation in brain regions known to be involved in both cough sensory processing (primary sensorimotor cortex) and cough suppression (dorsolateral prefrontal cortex and the midbrain nucleus cuneiformis). Activations in the prefrontal cortex were highest among participants with the least severe smoking behaviour, whereas those in the midbrain correlated with more severe smoking behaviour.These outcomes suggest that smoking-induced sensitisation of central cough neural circuits is offset by concurrently enhanced central suppression. Furthermore, central suppression mechanisms may evolve with the severity of smoke exposure, changing from initial prefrontal inhibition to more primitive midbrain processes as exposure increases.

Regional brain stem activations during capsaicin inhalation using functional magnetic resonance imaging in humans

Coughing is an airway protective behavior elicited by airway irritation. Animal studies show that airway sensory information is relayed via vagal sensory fibers to termination sites within dorsal caudal brain stem and thereafter relayed to more rostral sites. Using functional magnetic resonance imaging (fMRI) in humans, we previously reported that inhalation of the tussigenic stimulus capsaicin evokes a perception of airway irritation ("urge to cough") accompanied by activations in a widely distributed brain network including the primary sensorimotor, insular, prefrontal, and posterior parietal cortices. Here we refine our imaging approach to provide a directed survey of brain stem areas activated by airway irritation. In 15 healthy participants, inhalation of capsaicin at a maximal dose that elicits a strong urge to cough without behavioral coughing was associated with activation of medullary regions overlapping with the nucleus of the solitary tract, paratrigeminal nucleus, spinal trigeminal nucleus and tract, cardiorespiratory regulatory areas homologous to the ventrolateral medulla in animals, and the midline raphe. Interestingly, the magnitude of activation within two cardiorespiratory regulatory areas was positively correlated ( r2 = 0.47, 0.48) with participants' subjective ratings of their urge to cough. Capsaicin-related activations were also observed within the pons and midbrain. The current results add to knowledge of the representation and processing of information regarding airway irritation in the human brain, which is pertinent to the pursuit of novel cough therapies. NEW & NOTEWORTHY Functional brain imaging in humans was optimized for the brain stem. We provide the first detailed description of brain stem sites activated in response to airway irritation. The results are consistent with findings in animal studies and extend our foundational knowledge of brain processing of airway irritation in humans.

Lightweight sCMOS-based high-density diffuse optical tomography.

.Though optical imaging of human brain function is gaining momentum, widespread adoption is restricted in part by a tradeoff among cap wearability, field of view, and resolution. To increase coverage while maintaining functional magnetic resonance imaging (fMRI)-comparable image quality, optical systems require more fibers. However, these modifications drastically reduce the wearability of the imaging cap. The primary obstacle to optimizing wearability is cap weight, which is largely determined by fiber diameter. Smaller fibers collect less light and lead to challenges in obtaining adequate signal-to-noise ratio. Here, we report on a design that leverages the exquisite sensitivity of scientific CMOS cameras to use fibers with smaller cross-sectional area than current high-density diffuse optical tomography (HD-DOT) systems. This superpixel sCMOS DOT (SP-DOT) system uses -diameter fibers that facilitate a lightweight, wearable cap. We developed a superpixel algorithm with pixel binning and electronic noise subtraction to provide high dynamic range (), high frame rate (), and a low effective detectivity threshold (), each comparable with previous HD-DOT systems. To assess system performance, we present retinotopic mapping of the visual cortex ( subjects). SP-DOT offers a practical solution to providing a wearable, large field-of-view, and high-resolution optical neuroimaging system.

Towards Neuroadaptive Personal Learning Environments: Using fNIRS to Detect Changes in Attentional State

Towards Neuroadaptive Personal Learning Environments: Using fNIRS to Detect Changes in Attentional State

Quantitative evaluation of functional Near Infrared Spectroscopy measurements with different source-detector separations using Monte Carlo simulation

Quantitative evaluation of functional Near Infrared Spectroscopy measurements with different source-detector separations using Monte Carlo simulation

Valsalva-induced elevation of intracranial pressure selectively decouples deoxygenated hemoglobin concentration from neuronal activation and functional brain imaging capability

During neuronal activation, neurovascular coupling leads to a local decrease of deoxygenated hemoglobin concentration (deoxy-Hb) and thus forms the basis of many functional brain mapping methods. In animals, an elevated intracranial pressure (ICP) can attenuate or even reverse this deoxy-Hb signaling. To study the effect of an elevated ICP on functional brain imaging in humans, we used different breathing tasks to modify ICP and analyzed the resulting effect on neurovascular coupling in the motor cortex. Functional near-infrared spectroscopy (fNIRS) was performed on 45 subjects during alternating conditions of finger tapping and resting state combined with four different breathing maneuvers (normal breathing (NB), breath holding without Valsalva maneuver (BH), Valsalva maneuver with 15 mm Hg forced expiratory pressure against resistance (V15) and Valsalva maneuver with 35 mm Hg forced expiratory pressure against resistance (V35)) in randomized order. With escalation of breathing tasks the median amplitude of the functional deoxy-Hb decrease during finger tapping became smaller. In contrast, functional oxygenated hemoglobin concentration (oxy-Hb) and total hemoglobin concentration (total-Hb) responses did not show a significant alteration. The functional oxy-Hb map evoked by finger tapping withstood Valsalva challenges while the functional deoxy-Hb map identified the correct motor cortex in normal breathing conditions only and did not reveal a functional contrast during Valsalva maneuvers. In summary, we conclude that during ICP elevation, deoxy-Hb is not a reliable basis for functional brain imaging. This suggests that the validity of BOLD fMRI during increased ICP might be impaired.

BRAIN NETWORKS AS TARGETS OF NEURODEGENERATION IN PD AND AD

Our main objective is to uncover mechanisms of disease initiation and propagation in Alzheimer’s Disease (AD) and Parkinson’s Disease (PD). Human functional brain imaging has shown that the brain is organized in large-scale networks. These have been identified mainly from resting state functional MRI (rsfMRI) and diffusion tractography (DTI). Also, recent evidence suggests that neurodegenerative diseases may be the result of prion-like spreading of misfolded proteins. A misfolded protein is thought to spread via neuronal projections and then induce further misfolding and neurodegeneration in target regions. Transneuronal spread has been demonstrated in animal models for tau and beta-amyloid (implicated in AD) and alpha-synuclein (PD). Accordingly, MRI studies in AD and fronto-temporal dementia (FTD) show that the patterns of atrophy in different syndromes demonstrate overlap with intrinsic brain networks found in healthy individuals. AD appears to target the default mode network, a set of interconnected brain areas implicated in monitoring and memory retrieval. Conversely, variants of FTD target different networks; for example, the behavioral variant of FTD, which is characterized by impulsivity and disordered emotional regulation, targets a brain network implicated in reward and motivation. We used the Parkinson’s Progression Markers Initiative (PPMI), a large open-source database of imaging and clinical data in de novo PD patients. We performed deformation based morphometry and independent component analysis to identify areas showing atrophy in PD patients compared to control subjects. Striatum, basal forebrain, amygdala, hippocampus, insula and anterior cingulate cortex demonstrated atrophy in proportion to clinical disease severity, consistent with the scheme proposed by Braak from postmortem data. We also show that these regions form a connected intrinsic network. Moreover, we show that disease patterns follow brain connectomics, compatible with an epicenter in the substantia nigra. Finally we find that cognitive impairment at visit 2 is associated with progression of atrophy in the entorhinal cortex.

Multi-Voxel Decoding and the Topography of Maintained Information During Visual Working Memory.

The ability to maintain representations in the absence of external sensory stimulation, such as in working memory, is critical for guiding human behavior. Human functional brain imaging studies suggest that visual working memory can recruit a network of brain regions from visual to parietal to prefrontal cortex. In this review, we focus on the maintenance of representations during visual working memory and discuss factors determining the topography of those representations. In particular, we review recent studies employing multi-voxel pattern analysis (MVPA) that demonstrate decoding of the maintained content in visual cortex, providing support for a “sensory recruitment” model of visual working memory. However, there is some evidence that maintained content can also be decoded in areas outside of visual cortex, including parietal and frontal cortex. We suggest that the ability to maintain representations during working memory is a general property of cortex, not restricted to specific areas, and argue that it is important to consider the nature of the information that must be maintained. Such information-content is critically determined by the task and the recruitment of specific regions during visual working memory will be both task- and stimulus-dependent. Thus, the common finding of maintained information in visual, but not parietal or prefrontal, cortex may be more of a reflection of the need to maintain specific types of visual information and not of a privileged role of visual cortex in maintenance.

Central Nervous System Control of Voice and Swallowing.

This review of the central nervous control systems for voice and swallowing has suggested that the traditional concepts of a separation between cortical and limbic and brain stem control should be refined and be more integrative. For voice production, a separation of the nonhuman vocalization system from the human learned voice production system has been posited based primarily on studies of nonhuman primates. However, recent humans studies of emotionally based vocalizations and human volitional voice production have shown more integration between these two systems than previously proposed. Recent human studies have shown that reflexive vocalization as well as learned voice production not involving speech involve a common integrative system. However, recent studies of nonhuman primates have provided evidence that some cortical activity vocalization and cortical changes occur with training during vocal behavior. For swallowing, evidence from the macaque and functional brain imaging in humans indicates that the control for the pharyngeal phase of swallowing is not primarily under brain stem mechanisms as previously proposed. Studies suggest that the initiation and patterning of swallowing for the pharyngeal phase is also under active cortical control for both spontaneous as well as volitional swallowing in awake humans and nonhuman primates.

The development of the intrinsic functional connectivity of default network subsystems from age 3 to 5.

In recent years, research on human functional brain imaging using resting-state fMRI techniques has been increasingly prevalent. The term "default mode" was proposed to describe a baseline or default state of the brain during rest. Recent studies suggested that the default mode network (DMN) is comprised of two functionally distinct subsystems: a dorsal-medial prefrontal cortex (DMPFC) subsystem involved in self-oriented cognition (i.e., theory of mind) and a medial temporal lobe (MTL) subsystem engaged in memory and scene construction; both subsystems interact with the anterior medial prefrontal cortex (aMPFC) and posterior cingulate (PCC) as the core regions of DMN. The present study explored the development of DMN core regions and these two subsystems in both hemispheres from 3- to 5-year-old children. The analysis of the intrinsic activity showed strong developmental changes in both subsystems, and significant changes were specifically found in MTL subsystem, but not in DMPFC subsystem, implying distinct developmental trajectories for DMN subsystems. We found stronger interactions between the DMPFC and MTL subsystems in 5-year-olds, particularly in the left subsystems that support the development of environmental adaptation and relatively complex mental activities. These results also indicate that there is stronger right hemispheric lateralization at age 3, which then changes as bilateral development gradually increases through to age 5, suggesting in turn the hemispheric dominance in DMN subsystems changing with age. The present results provide primary evidence for the development of DMN subsystems in early life, which might be closely related to the development of social cognition in childhood.

Contributions and complexities from the use of in vivo animal models to improve understanding of human neuroimaging signals.

Many of the major advances in our understanding of how functional brain imaging signals relate to neuronal activity over the previous two decades have arisen from physiological research studies involving experimental animal models. This approach has been successful partly because it provides opportunities to measure both the hemodynamic changes that underpin many human functional brain imaging techniques and the neuronal activity about which we wish to make inferences. Although research into the coupling of neuronal and hemodynamic responses using animal models has provided a general validation of the correspondence of neuroimaging signals to specific types of neuronal activity, it is also highlighting the key complexities and uncertainties in estimating neural signals from hemodynamic markers. This review will detail how research in animal models is contributing to our rapidly evolving understanding of what human neuroimaging techniques tell us about neuronal activity. It will highlight emerging issues in the interpretation of neuroimaging data that arise from in vivo research studies, for example spatial and temporal constraints to neuroimaging signal interpretation, or the effects of disease and modulatory neurotransmitters upon neurovascular coupling. We will also give critical consideration to the limitations and possible complexities of translating data acquired in the typical animals models used in this area to the arena of human fMRI. These include the commonplace use of anesthesia in animal research studies and the fact that many neuropsychological questions that are being actively explored in humans have limited homologs within current animal models for neuroimaging research. Finally we will highlighting approaches, both in experimental animals models (e.g. imaging in conscious, behaving animals) and human studies (e.g. combined fMRI-EEG), that mitigate against these challenges.

799 THE ANTERIOR CINGULATE GYRUS PLAYS AN IMPORTANT ROLE IN THE CONTROL OF MICTURITION REFLEX IN A RAT MODEL OF PARKINSON'S DISEASE

You have accessJournal of UrologyUrodynamics/Incontinence/Female Urology: Basic Research1 Apr 2011799 THE ANTERIOR CINGULATE GYRUS PLAYS AN IMPORTANT ROLE IN THE CONTROL OF MICTURITION REFLEX IN A RAT MODEL OF PARKINSON'S DISEASE Takeya Kitta, Hiroshi Tanaka, Takahiko Mitsui, Yukiko Kanno, Kimihiko Moriya, Katsuya Nonomura, and Naoki Yoshimura Takeya KittaTakeya Kitta Sapporo, Japan More articles by this author , Hiroshi TanakaHiroshi Tanaka Sapporo, Japan More articles by this author , Takahiko MitsuiTakahiko Mitsui Sapporo, Japan More articles by this author , Yukiko KannoYukiko Kanno Sapporo, Japan More articles by this author , Kimihiko MoriyaKimihiko Moriya Sapporo, Japan More articles by this author , Katsuya NonomuraKatsuya Nonomura Sapporo, Japan More articles by this author , and Naoki YoshimuraNaoki Yoshimura Pittsburgh, PA More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2011.02.617AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Micturition reflex is controlled by a complex hierarchy of the CNS. The pontine micturition center and midbrain periaqueductal gray (PAG) integrates bladder information. The anterior cingulate gyrus (ACG) is also thought to participate in the control of micturition, based on functional brain imaging studies although its functional role is not fully understood. The present study examined dynamic neural activity changes in the ACG and PAG during the micturition reflex induced by pelvic nerve (PLN) stimulation. METHODS Sprague-Dawely rats were divided into PD and sham groups, which were injected with 6-hydroxydopamine and vehicle, respectively, into the substantia nigra. A tungsten electrode was inserted stereotaxically into the ACG and PAG to record field potentials that were evoked by PLN stimulation. The effects of ZM24138 (ZM) (adenosine A2A antagonist) administered intravenously (i.v.) on the PLN evoked field potentials in the PAG and ACG were examined. RESULTS PD rats showed bladder overactivity evidenced by a significant decrease in intercontraction intervals (ICI) compared with sham rats. I.v. administration of ZM increased ICI in both rats with the inhibitory effects being greater in PD vs. sham rats, and also increased the amplitude of the evoked potentials in a dose dependent manner in the ACG of PD rats. However, no significant changes in ACG evoked potentials were found in sham rats. I.v. administration of ZM reduced the amplitude of evoked potentials in PAG of both rats with the inhibitory effects being greater in PD vs. sham rats (figure). CONCLUSIONS In this study, neural activity in the ACG was significantly increased along with suppression of bladder overactivity after ZM administration only in the PD model, suggesting that ACG neurons have an inhibitory role in bladder control. This assumption is supported by human functional brain imaging showing increased responses in the ACG during withholding urine. In addition, reduced ACG activity due to activation of adenosine A2A receptors seems to contribute to bladder overactivity in PD. In contrast, a decrease in PAG activity may lead to inhibition of the micturition reflex. Understanding the roles of CNS nuclei including the ACG in the modulation of micturition could provide further insights into the pathophysiology of OAB. © 2011 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 185Issue 4SApril 2011Page: e321-e322 Advertisement Copyright & Permissions© 2011 by American Urological Association Education and Research, Inc.MetricsAuthor Information Takeya Kitta Sapporo, Japan More articles by this author Hiroshi Tanaka Sapporo, Japan More articles by this author Takahiko Mitsui Sapporo, Japan More articles by this author Yukiko Kanno Sapporo, Japan More articles by this author Kimihiko Moriya Sapporo, Japan More articles by this author Katsuya Nonomura Sapporo, Japan More articles by this author Naoki Yoshimura Pittsburgh, PA More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Brain tissue oxygen amperometry in behaving rats demonstrates functional dissociation of dorsal and ventral hippocampus during spatial processing and anxiety

Traditionally, the function of the hippocampus (HPC) has been viewed in unitary terms, but there is growing evidence that the HPC is functionally differentiated along its septotemporal axis. Lesion studies in rodents and functional brain imaging in humans suggest a preferential role for the septal HPC in spatial learning and a preferential role for the temporal HPC in anxiety. To better enable cross-species comparison, we present an in vivo amperometric technique that measures changes in brain tissue oxygen at high temporal resolution in freely-moving rats. We recorded simultaneously from the dorsal (septal; dHPC) and ventral (temporal; vHPC) HPC during two anxiety tasks and two spatial tasks on the radial maze. We found a double-dissociation of function in the HPC, with increased vHPC signals during anxiety and increased dHPC signals during spatial processing. In addition, dHPC signals were modulated by spatial memory demands. These results add a new dimension to the growing consensus for a differentiation of HPC function, and highlight tissue oxygen amperometry as a valuable tool to aid translation between animal and human research.

What Body Parts Reveal about the Organization of the Brain

In this issue of Neuron, Orlov etal. show that the human occipitotemporal cortex contains regions responding preferentially to body part categories, such as upper limbs (hand, elbow), torsos, or lower faces (mouth, chin). This organization may reflect differences in the connectivity of these regions with other brain regions, to support the efficient processing of the different types of information different body parts provide.

Using non-invasive brain interference as a tool for mimicking spatial neglect in healthy volunteers

Visuospatial processing refers to the spatial perception, recognition and analysis of visual input. Human functional brain imaging studies have consistently revealed the involvement of fronto-parietal brain areas during the execution of visuospatial tasks. Just as the execution of these tasks activates fronto-parietal regions in the healthy brain, lesions to those structures, e.g. after stroke or brain injury, cause specific spatial deficits. The most prominent of these is known as spatial neglect. There are several competing theories on the neural mechanisms underlying spatial neglect. Although each of these theories postulates different underlying physiological mechanisms, they all account in their own way for the fact that the prevalence of neglect is much higher following right hemisphere lesions. This makes it difficult to distinguish between the different models at a behavioural level. Until today, it was impossible to empirically address these matters and to provide direct and conclusive empirical evidence in favour of one of the competing theories of spatial neglect. This review article describes the neural correlates of intact visuospatial processing as revealed by non-invasive functional brain imaging studies. It subsequently focuses on the approach of using the non-invasive brain inference technique of transcranial magnetic brain stimulation (TMS) to transiently and reversibly disrupt neural activity in these visuospatial processing-related brain regions. Using this approach, we can now imitate specific spatial deficits and neglect-like symptoms in healthy volunteers. Mimicking and manipulating the spatial deficits following unilateral brain lesions, under controlled experimental conditions, may allow for the development of new therapeutic interventions for parietal stroke patients suffering from real spatial neglect. The perspective is to use non-invasive brain interference to guide and promote functional recovery on a brain-system level in stroke and neglect patients, based on knowledge directly derived from fundamental brain research in healthy volunteers.

Real-time imaging of human brain function by near-infrared spectroscopy using an adaptive general linear model

Near-infrared spectroscopy is a non-invasive neuroimaging method which uses light to measure changes in cerebral blood oxygenation associated with brain activity. In this work, we demonstrate the ability to record and analyze images of brain activity in real-time using a 16-channel continuous wave optical NIRS system. We propose a novel real-time analysis framework using an adaptive Kalman filter and a state–space model based on a canonical general linear model of brain activity. We show that our adaptive model has the ability to estimate single-trial brain activity events as we apply this method to track and classify experimental data acquired during an alternating bilateral self-paced finger tapping task.