Task-related Cortical Activation Research Articles

A Functional Near Infrared Spectroscopy Investigation of the Physiological Underpinnings of Visual Cognitive Workload After Concussion

Background:In concussion, functional near infrared spectroscopy (fNIRS) has been shown to detect differences in cortical oxygenation during neurocognitive testing, with concussed adults manifesting less task-based cortical activation compared to controls. In addition, fNIRS has identified significantly reduced interhemispheric coherence in adult concussions relative to controls. In addition, adults with greater post-concussive symptom burden demonstrate lower task-related oxygenation in the frontal and dorsolateral prefrontal cortex (DLPFC) and reduced connectivity compared to controls.Hypothesis:The goal of this study was to use fNIRS to identify any differences in visual task-related cortical activation between concussed adolescents and healthy controls while performing a the King-Devick (KD) test.Methods:We enrolled 112 adolescents, ages 12-18 years, with recent concussion and 165 healthy controls as part of a large observational prospective cohort. Participants were provided standardized instructions to read the KD cards while wearing the fNIRS sensor pad. The relative changes in the difference of oxy-and deoxy-hemoglobin concentrations over each task condition for each optode were calculated via the Modified Beer-Lambert Law using local baselines for each task condition period as its beginning. The averaged oxy-hemoglobin concentration changes for each task period were used for statistical analysis of group (e.g., concussed vs healthy) effect.Results:The concussed adolescents (n=112) and healthy controls (n=165) were demographically comparable with respect to age, sex, and race/ethnicity. The concussed group was more likely to have a history of prior concussion (p = <.0001) and migraine (p = .0001) compared to the healthy control group (Table 1). The concussed adolescents were assessed with fNIRS while performing a visual task a median of 10 days after injury (IQR 4-16). The concussed group had significantly lower oxygenation changes that are the difference between oxygenated and deoxygenated hemoglobin as an indicator of task-evoked response, on left lateral prefrontal area (p<.005, FDR q<.005). As expected, there was also a main effect for task condition (cards) at right lateral prefrontal cortex (p<.001, FDR q<.005).Conclusions:fNIRS is able to distinguish concussed adolescents from healthy controls while performing a visual-cognitive task, the K-D test. Injured adolescents with concussion demonstrated a compensatory pattern of cortical activation, suggesting localized brain dysfunction, recruiting from both hemispheres, distinguishing it from the pattern of cortical activation in healthy controls. fNIRS, as a modality, is not only able to differentiate concussion from healthy controls, but also captures the compensatory mechanisms of cortical activation that underlie visual cognitive function after injury.

Cognitive inhibition mediates the relationship between ESL listening proficiency and English spoken word segmentation in Chinese learners: A functional near-infrared spectroscopy (fNIRS) study

The ability to segment spoken words is vitally important for language learners since it is crucial for their language development and well predicts their future language skills. The possible influence of cognitive inhibition on this ability was proposed in theory. However, there is no direct evidence supporting the role and underlying mechanism of cognitive inhibition in spoken word segmentation (SWS) in both behavioral and neuroimaging research. The present study addressed this issue by exploring the relationships among English as second language (ESL) listening proficiency, cognitive inhibition ability, and SWS performance. Cortical activation in the temporo-parietal junction (TPJ) and the prefrontal cortex (PFC) were recorded during the process of SWS by functional near-infrared spectroscopy (fNIRS). The results showed that English listening proficiency was positively associated with cognitive inhibition ability, which in turn was positively correlated with SWS performance. Moreover, we found both English listening proficiency and SWS performance were in negative associations with cortical activation in the TPJ, while cognitive inhibition ability was positively correlated with neural activities in the PFC. Critically, further mediation analysis revealed that cognitive inhibition ability mediated not only the relationship between English listening proficiency and SWS performance but also the association between English listening proficiency and cortical activation in the TPJ (recorded during SWS). Our preliminary findings suggest that English listening proficiency may affect SWS performance and task-related cortical activation through its impact on cognitive inhibition ability.

Spontaneous Eye Blink Rate Connects Missing Link between Aerobic Fitness and Cognition.

Higher aerobic fitness, a physiological marker of habitual physical activity, is likely to predict higher executive function based on the prefrontal cortex (PFC), according to current cross-sectional studies. The exact biological link between the brain and the brawn remains unclear, but the brain dopaminergic system, which acts as a driving force for physical activity and exercise, can be hypothesized to connect the missing link above. Recently, spontaneous eye blink rate (sEBR) was proposed and has been used as a potential, noninvasive marker of brain dopaminergic activity in the neuroscience field. To address the hypothesis above, we sought to determine whether sEBR is a mediator of the association between executive function and aerobic fitness. Thirty-five healthy young males (18-24 yr old) had their sEBR measured while staring at a fixation cross while at rest. They underwent an aerobic fitness assessment using a graded exercise test to exhaustion and performed a color-word Stroop task as an index of executive function. Stroop task-related cortical activation in the left dorsolateral PFC (l-DLPFC) was monitored using functional near-infrared spectroscopy. Correlation analyses revealed significant correlations among higher aerobic fitness, less Stroop interference, and higher sEBR. Moreover, mediation analyses showed that sEBR significantly mediated the association between aerobic fitness and Stroop interference. In addition, higher sEBR was correlated with higher neural efficiency of the l-DLPFC (i.e., executive function was high, and the corresponding l-DLPFC activation was relatively low). These results indicate that the sEBR mediates the association between aerobic fitness and executive function through prefrontal neural efficiency, which clearly supports the hypothesis that brain dopaminergic function works to connect, at least in part, the missing link between aerobic fitness and executive function.

Functional near-infrared spectroscopy to assess sensorimotor cortical activity during hand squeezing and ankle dorsiflexion in individuals with and without bilateral and unilateral cerebral palsy.

.Significance: Our study is the first comparison of brain activation patterns during motor tasks across unilateral cerebral palsy (UCP), bilateral cerebral palsy (BCP), and typical development (TD) to elucidate neural mechanisms and inform rehabilitation strategies.Aim: Cortical activation patterns were compared for distal upper and lower extremity tasks in UCP, BCP, and TD using functional near-infrared spectroscopy (fNIRS) and related to functional severity.Approach: Individuals with UCP (, ), BCP (, ), and TD (, ) participated in this cross-sectional cohort study. The fNIRS was used to noninvasively monitor the hemodynamic response to task-related cortical activation. The block design involved repetitive nondominant hand squeezing and ankle dorsiflexion.Results: Individuals with UCP demonstrated the highest levels of activation for the squeeze task ( ; ; and ) and more activity in the ipsilateral versus contralateral hemisphere. Individuals with BCP showed the highest levels of cortical activation in the dorsiflexion task ( ; ).Conclusions: Grouping by CP subtype and manual function or mobility level demonstrated significant differences from TD, even for individuals with the mildest forms of CP. Hemispheric activation patterns showed hypothesized but nonsignificant trends.

Positive Mood while Exercising Influences Beneficial Effects of Exercise with Music on Prefrontal Executive Function: A Functional NIRS Study

Much attention has been focused on physical exercise benefits to mental health such as mood and cognitive function. Our recent studies have consistently shown that a single bout of exercise elicits increased task-related brain activation mainly in the dorsolateral part of the prefrontal cortex (DLPFC), which results in improved executive performance. As the DLPFC is associated with the modulation of mood as well as executive function, it is tempting to hypothesize that exercising while in a positive mood would facilitate the beneficial effects of exercise on executive function via DLPFC activation. Thus, we conceived an experiment that used music to elicit a positive mood during exercise. Thirty-three young adults performed ten minutes of moderate-intensity (50% V.O2peak) pedaling exercise with two experimental conditions: listening to music and listening to beeps at a steady tempo. Mood and executive function were respectively assessed using the Two-Dimensional Mood Scale and a color-word-matching Stroop task before and after the exercise sessions. Prefrontal activation during the Stroop task was monitored using functional near-infrared spectroscopy. Exercise with music elicited greater enhancement of a positive mood (vitality) than did exercise with beeps. Contrary to our hypothesis, there were no significant differences between conditions in improvement in Stroop task performance and task-related cortical activation in the left-DLPFC. The correlation analyses, however, revealed significant correlations among increased vitality, shortened Stroop interference time and increased activation in the left-DLPFC. These results support the hypothesis that positive mood while exercising influences the benefit of exercise on prefrontal activation and executive performance.

Concurrent exergaming and transcranial direct current stimulation to improve balance in people with Parkinson\u2019s disease: study protocol for a randomised controlled trial

BackgroundPeople with Parkinson’s disease (PD) commonly experience postural instability, resulting in poor balance and an increased risk of falls. Exercise-based video gaming (exergaming) is a form of physical training that is delivered through virtual reality technology to facilitate motor learning and is efficacious in improving balance in aged populations. In addition, studies have shown that anodal transcranial direct current stimulation (a-tDCS), when applied to the primary motor cortex, can augment motor learning when combined with physical training. However, no studies have investigated the combined effects of exergaming and tDCS on balance in people with PD.Methods/designTwenty-four people with mild to moderate PD (Hoehn and Yahr scale score 2–4) will be randomly allocated to receive one of three interventions: (1) exergaming + a-tDCS, (2) exergaming + sham a-tDCS or (3) usual care. Participants in each exergaming group will perform two training sessions per week for 12 weeks. Each exergaming session will consist of a series of static and dynamic balance exercises using a rehabilitation-specific software programme (Jintronix) and 20 minutes of either sham or real a-tDCS (2 mA) delivered concurrently. Participants allocated to usual care will be asked to maintain their normal daily physical activities. All outcome measures will be assessed at baseline and at 6 weeks (mid-intervention), 12 weeks (post-intervention) and 24 weeks (3-month follow-up) after baseline. The primary outcome measure will be the Limits of Stability Test. Secondary outcomes will include measures of static balance, leg strength, functional capacity, cognitive task-related cortical activation, corticospinal excitability and inhibition, and cognitive inhibition.DiscussionThis will be the first trial to target balance in people with PD with combined exergaming and a-tDCS. We hypothesise that improvements in balance, functional and neurophysiological outcome measures, and neurocognitive outcome measures will be greater and longer-lasting following concurrent exergaming and a-tDCS than in those receiving sham tDCS or usual care.Trial registrationAustralian New Zealand Clinical Trials Registry, ACTRN12616000594426). Registered on 9 May 2016.

Human brain patterns underlying vigilant attention: impact of sleep debt, circadian phase and attentional engagement

Sleepiness and cognitive function vary over the 24-h day due to circadian and sleep-wake-dependent mechanisms. However, the underlying cerebral hallmarks associated with these variations remain to be fully established. Using functional magnetic resonance imaging (fMRI), we investigated brain responses associated with circadian and homeostatic sleep-wake-driven dynamics of subjective sleepiness throughout day and night. Healthy volunteers regularly performed a psychomotor vigilance task (PVT) in the MR-scanner during a 40-h sleep deprivation (high sleep pressure) and a 40-h multiple nap protocol (low sleep pressure). When sleep deprived, arousal-promoting thalamic activation during optimal PVT performance paralleled the time course of subjective sleepiness with peaks at night and troughs on the subsequent day. Conversely, task-related cortical activation decreased when sleepiness increased as a consequence of higher sleep debt. Under low sleep pressure, we did not observe any significant temporal association between PVT-related brain activation and subjective sleepiness. Thus, a circadian modulation in brain correlates of vigilant attention was only detectable under high sleep pressure conditions. Our data indicate that circadian and sleep homeostatic processes impact on vigilant attention via specific mechanisms; mirrored in a decline of cortical resources under high sleep pressure, opposed by a subcortical “rescuing” at adverse circadian times.

Neurofeedback-induced facilitation of the supplementary motor area affects postural stability.

.Near-infrared spectroscopy-mediated neurofeedback (NIRS-NFB) is a promising therapeutic intervention for patients with neurological diseases. Studies have shown that NIRS-NFB can facilitate task-related cortical activation and induce task-specific behavioral changes. These findings indicate that the effect of neuromodulation depends on local cortical function. However, when the target cortical region has multiple functions, our understanding of the effects is less clear. This is true in the supplementary motor area (SMA), which is involved both in postural control and upper-limb movement. To address this issue, we investigated the facilitatory effect of NIRS SMA neurofeedback on cortical activity and behavior, without any specific task. Twenty healthy individuals participated in real and sham neurofeedback. Balance and hand dexterity were assessed before and after each NIRS-NFB session. We found a significant interaction between assessment periods (pre/post) and condition (real/sham) with respect to balance as assessed by the center of the pressure path length but not for hand dexterity as assessed by the 9-hole peg test. SMA activity only increased during real neurofeedback. Our findings indicate that NIRS-NFB itself has the potential to modulate focal cortical activation, and we suggest that it be considered a therapy to facilitate the SMA for patients with postural impairment.

The role of long-term physical exercise on performance and brain activation during the Stroop colour word task in fibromyalgia patients.

The Stroop colour word test (SCWT) has been widely used to assess changes in cognitive performance such as processing speed, selective attention and the degree of automaticity. Moreover, the SCWT has proven to be a valuable tool to assess neuronal plasticity that is coupled to improvement in performance in clinical populations. In a previous study, we showed impaired cognitive processing during SCWT along with reduced task-related activations in patients with fibromyalgia. In this study, we used SCWT and functional magnetic resonance imagingFMRI to investigate the effects of a 15-week physical exercise intervention on cognitive performance, task-related cortical activation and distraction-induced analgesia (DIA) in patients with fibromyalgia and healthy controls. The exercise intervention yielded reduced fibromyalgia symptoms, improved cognitive processing and increased task-related activation of amygdala, but no effect on DIA. Our results suggest beneficial effects of physical exercise on cognitive functioning in FM.

Brain activation in frontotemporal and Alzheimer's dementia: a functional near-infrared spectroscopy study.

BackgroundFrontotemporal dementia is an increasingly studied disease, the underlying functional impairments on a neurobiological level of which have not been fully understood. Patients with the behavioral-subtype frontotemporal dementia (bvFTD) are particularly challenging for clinical measurements such as functional imaging due to their behavioral symptoms. Here, an alternative imaging method, functional near-infrared spectroscopy (fNIRS), is introduced to measure task-related cortical brain activation based on blood oxygenation. The current study investigated differences in cortical activation patterns of patients with bvFTD, Alzheimer’s dementia (AD), and healthy elderly subjects measured by fNIRS.MethodEight probable bvFTD patients completed the semantic, phonological, and control conditions of a verbal fluency task. Eight AD patients and eight healthy controls were compared on the same task. Simultaneously, an fNIRS measurement was conducted and analyzed using a correction method based on the expected negative correlation between oxygenated and deoxygenated hemoglobin.ResultsHealthy controls show an increase in cortical activation measured in frontoparietal areas such as the dorsolateral prefrontal cortex. The activation pattern of patients with AD is similar, but weaker. In contrast, bvFTD patients show a more frontopolar pattern, with activation of Broca’s area, instead of the dorsolateral prefrontal cortex and the superior temporal gyrus. The frontoparietal compensation mechanisms, seen in the healthy elderly, were missing in bvFTD patients.ConclusionDifferent frontoparietal cortical activation patterns may indicate a correlate of diverse pathophysiological mechanisms of AD and bvFTD during verbal fluency processing. The AD pattern is weaker and more similar to the healthy pattern, whereas the bvFTD pattern is qualitatively different, namely more frontopolar and without frontoparietal compensation activation. It adheres to a change of cortical activation during the course of the disease.Electronic supplementary materialThe online version of this article (doi:10.1186/s13195-016-0224-8) contains supplementary material, which is available to authorized users.

Practicing Novel, Praxis-Like Movements: Physiological Effects of Repetition.

Our primary goal was to develop and validate a task that could provide evidence about how humans learn praxis gestures, such as those involving the use of tools. To that end, we created a video-based task in which subjects view a model performing novel, meaningless one-handed actions with kinematics similar to praxis gestures. Subjects then imitated the movements with their right hand. Trials were repeated six times to examine practice effects. EEG was recorded during the task. As a control, subjects watched videos of a model performing a well-established (over learned) tool-use gesture. These gestures were also imitated six times. Demonstrating convergent validity, EEG measures of task-related cortical activation were similar in topography and frequency between the novel gesture task and the overlearned, praxis gesture task. As in studies assessing motor skill learning with simpler tasks, cortical activation during novel gesture learning decreased as the same gestures were repeated. In the control condition, repetition of overlearned tool-use gestures were also associated with reductions in activation, though to a lesser degree. Given that even overlearned, praxis gestures show constriction of EEG activity with repetition, it is possible that that attentional effects drive some of the repetition effects seen in EEG measures of activation during novel gesture repetition.

Mechanisms of cortical high-gamma activity (60-200 Hz) investigated with computational modeling

High-gamma activity (HGA) at frequencies 60-200 Hz have been observed during task-related cortical activation in humans [1] and in animals [2], and have been used to map normal brain function and to decode commands in brain-computer interfaces. To understand the role that HGA plays in both normal and pathological brain states, deeper insights into its generating mechanisms are essential. Because the neural populations recorded by LFPs and EEG cannot be comprehensively recorded at scales that are likely to be relevant, we used a biologically based computational model of a cortical network to investigate the mechanisms generating HGA. The computational model included excitatory pyramidal regular-spiking and inhibitory fast-spiking neurons described by Hodgkin - Huxley dynamics. We compared activity generated by this model with HGA that was observed in LFP recorded in monkey somatosensory cortex during vibrotactile stimulation. Increase of firing rate and broadband HGA responses in LFP signals generated by the model were in agreement with experimental results (see Figure ​Figure11). Figure 1 Comparison of high-gamma observed in vivo (AB) and simulated in the model (CD) during sensory stimulation for different stimulus amplitudes denoted G1, G2, G5 and G10. AC: average firing rate of neurons. BD: time - frequency maps of LFP signals.

Asymmetric projections of the arcuate fasciculus to the temporal cortex underlie lateralized language function in the human brain.

The arcuate fasciculus (AF) in the human brain has asymmetric structural properties. However, the topographic organization of the asymmetric AF projections to the cortex and its relevance to cortical function remain unclear. Here we mapped the posterior projections of the human AF in the inferior parietal and lateral temporal cortices using surface-based structural connectivity analysis based on diffusion MRI and investigated their hemispheric differences. We then performed the cross-modal comparison with functional connectivity based on resting-state functional MRI (fMRI) and task-related cortical activation based on fMRI using a semantic classification task of single words. Structural connectivity analysis showed that the left AF connecting to Broca's area predominantly projected in the lateral temporal cortex extending from the posterior superior temporal gyrus to the mid part of the superior temporal sulcus and the middle temporal gyrus, whereas the right AF connecting to the right homolog of Broca's area predominantly projected to the inferior parietal cortex extending from the mid part of the supramarginal gyrus to the anterior part of the angular gyrus. The left-lateralized projection regions of the AF in the left temporal cortex had asymmetric functional connectivity with Broca's area, indicating structure-function concordance through the AF. During the language task, left-lateralized cortical activation was observed. Among them, the brain responses in the temporal cortex and Broca's area that were connected through the left-lateralized AF pathway were specifically correlated across subjects. These results suggest that the human left AF, which structurally and functionally connects the mid temporal cortex and Broca's area in asymmetrical fashion, coordinates the cortical activity in these remote cortices during a semantic decision task. The unique feature of the left AF is discussed in the context of the human capacity for language.

Early Sensory Contributions to Contextual Encoding Deficits in Schizophrenia

The AX version of the visual continuous performance task (AX-CPT) is widely used for investigating visual working memory dysfunction in schizophrenia. Event-related potentials (ERP) provide an objective index of brain function and can be used to evaluate brain substrates underlying impaired cognition in schizophrenia. To assess the mechanisms that underlie visual working memory dysfunction in schizophrenia relative to impairment of early visual processing. Case-control study. Inpatient and outpatient facilities associated with the Nathan Kline Institute for Psychiatric Research. A total of 30 individuals with schizophrenia and 17 healthy comparison subjects. Three versions of the AX-CPT, with parametric variations in the proportions of trial types, were used to test performance and underlying neural activity during differential challenge situations. Contrast sensitivity measures were obtained from most subjects. Behavioral performance was assessed using d' context scores. Integrity of stimulus- and task-related cortical activation to both cue and probe stimuli was assessed using sensory (C1, P1, N1) and cognitive (N2, contingent negative variation [CNV]) ERP components. Early magnocellular/parvocellular function was assessed using contrast sensitivity. Linear regression and path analyses were used to assess relations between physiological and behavioral parameters. Patients showed reduced amplitude of both early sensory (P1, N1) and later cognitive (N2, CNV) ERP components. Deficits in sensory (N1) and cognitive (N2) component activation to cue stimuli contributed independently to impaired behavioral performance. In addition, sensory deficits predicted impaired cognitive ERP generation. Finally, deficits in performance correlated with impairments in contrast sensitivity to low, but not high, spatial frequency stimuli. Working memory deficits in schizophrenia have increasingly been attributed to impairments in stimulus encoding rather than to failures in memory retention. This study provides objective physiological support for encoding hypotheses. Further, deficits in sensory processing contribute significantly to impaired working memory performance, consistent with generalized neurochemical models of schizophrenia.

P2-405: Induction of toll-like receptor 9 signaling as a method for preventing or ameliorating Alzheimer's disease

the control group. After training, these differences in task-related cortical activation patterns between groups were reduced. Conclusions: The results of our study indicate that a computer assisted training program over 4 weeks may significantly improve visual working memory task-performance in healthy elderly and MCI patients and that this improvement is accompanied by neuroplastical changes, as indicated by altered task-related cortical activation patterns.

Neural Correlates of Promotion and Prevention Goal Activation: An fMRI Study using an Idiographic Approach

Regulatory focus theory [Higgins, E. T. Beyond pleasure and pain. American Psychologist, 52, 1280-1300, 1997] postulates two social-cognitive motivational systems, the promotion and prevention systems, for self-regulation of goal pursuit. However, the neural substrates of promotion and prevention goal activation remain unclear. Drawing on several literatures, we hypothesized that priming promotion versus prevention goals would activate areas in the left versus right prefrontal cortex (PFC), respectively, and that activation in these areas would be correlated with individual differences in chronic regulatory focus. Sixteen participants underwent functional magnetic resonance imaging while engaged in a depth-of-processing task, during which they were exposed incidentally to their own promotion and prevention goals. Task-related cortical activation was consistent with previous studies. At the same time, incidental priming of promotion goals was associated with left orbital PFC activation, and activation in this area was stronger for individuals with a chronic promotion focus. Findings regarding prevention goal priming were not consistent with predictions. The data illustrate the centrality of self-regulation and personal goal pursuit within the multilayered process of social cognition.

Diffusion tensor imaging of adult age differences in cerebral white matter: relation to response time

Diffusion tensor imaging (DTI) measures the displacement of water molecules across tissue components, thus providing information regarding the microstructure of cerebral white matter. Fractional anisotropy (FA), the degree to which diffusion is directionally dependent, is typically higher for compact, homogeneous fiber bundles such as the corpus callosum. Previous DTI studies in adults have demonstrated an age-related decline in white matter FA, but whether the relation between FA and behavioral performance varies as a function of age has not been determined. We investigated adult age differences in FA, and age-related changes in the relation between FA and response time (RT), in a visual target-detection task. The results confirmed that, independently of age, FA is higher in the corpus callosum than in other brain regions. We also observed an age-related decline in FA that did not vary significantly across the brain regions. For both age groups, a lower level of integrity of the cerebral white matter (as indexed by FA), in specific brain regions, was associated with slower responses in the visual task. An age-related change in this relation was evident, however, in that the best predictor of RT for younger adults was FA in the splenium of the corpus callosum, whereas for older adults the best predictor was FA in the anterior limb of the internal capsule. This pattern is consistent with measures of the task-related cortical activation obtained from these same individuals and suggests an age-related increase in the attentional control of responses mediated by corticostriatal or corticothalamic circuits.

Functional dynamics of spoken and signed word production: A case study using electrocorticographic spectral analysis

Background: Event-related changes in the EEG power spectrum have recently been used to study functional brain activation in humans. Like traditional event-related potentials, event-related spectral changes provide information about the temporal evolution of cortical activation that is difficult to obtain with fMRI or PET. These spectral changes include event-related suppression of power in the alpha band (8-13 Hz) and even-related augmentation of power in the gamma band (>30 Hz). Most studies of the gamma band have focused on frequencies in and around 40 Hz. Using electrocorticographic (ECoG) signals recorded with subdural electrodes implanted for the surgical management of epilepsy, we have also observed a broadband augmentation of power in higher gamma frequencies (>80 Hz). This index of cortical activation has compared favourably with alpha suppression and with electrical cortical stimulation mapping in studies utilising simple motor and auditory processing, but such a comparison has not been done for tasks requiring more complex language processing. Aims: We used two different spectral indices of cortical activation - alpha power suppression and gamma power augmentation, to study the spatial and temporal patterns of human cortical activation during different word production tasks. Methods: Subdural ECoG electrodes were implanted for clinical purposes in a patient with normal hearing, who had learned sign language as an adult and later developed intractable epilepsy. We measured event-related spectral changes during language tasks with different input and output modalities: Picture naming and word reading (visual inputs), and word repetition (auditory input) were performed with spoken responses (oral-articulatory output) and with signed responses (manual-gestural output). In addition we used a visually guided motor task to map tongue and hand representations independent of language. Results: Speech and signing differentially activated tongue and hand regions of sensorimotor cortex. Although posterior superior temporal gyrus was activated early during auditory word repetition, picture naming and word reading also activated this region, albeit slightly later, consistent with phonological and/or lexical-semantic processing. In contrast, basal temporal-occipital cortex was activated earlier and with greater magnitude during picture naming and word reading than during word repetition, suggesting semantic processing or object and word recognition. In all of the tasks, event-related gamma augmentation occurred in more discrete spatial and temporal patterns than event-related alpha suppression. Conclusions: Event-related alpha suppression and gamma augmentation provide complementary information about task-related cortical activation. This study demonstrates the utility of ECoG spectral analysis for studying the functional anatomy of human language with excellent temporal resolution.

Cerebral oxygenation changes during motor and somatosensory stimulation in humans, as measured by near-infrared spectroscopy.

Functional cortical activation is coupled to changes of cerebral hemodynamics and metabolism. These changes have been used in positron emission tomography and recently developed functional magnetic resonance techniques to localize task-related cortical activation. Near-infrared spectroscopy has the potential to monitor changes of intracerebral blood oxygenation during functional activation (Villringer 1993, Hoshi 1993). We proceeded from a rather global, cognitive stimulus to experimental paradigms which entail a more localized cerebral activation and which have been examined by other functional techniques. In establishing a simple motor and a vibratory stimulus we sought a means to further examine the issue of coupling of neuronal function and cerbral hemodynamics. In recent experiments we were able to demonstrate that these stimulation models are useful to retrieve additional information about oxygenation dependent signal changes in functional MRI (Kleinschmidt 1994, Obrig 1994). As near-infrared spectroscopy has a good temporal resolution, we were also interested in the time course of local oxygenation changes.