Task-related Changes Research Articles

MEG Responses to the Perception of Global Structure within Glass Patterns

BackgroundThe perception of global form requires integration of local visual cues across space and is the foundation for object recognition. Here we used magnetoencephalography (MEG) to study the location and time course of neuronal activity associated with the perception of global structure from local image features. To minimize neuronal activity to low-level stimulus properties, such as luminance and contrast, the local image features were held constant during all phases of the MEG recording. This allowed us to assess the relative importance of striate (V1) versus extrastriate cortex in global form perception.Methodology/Principal FindingsStimuli were horizontal, rotational and radial Glass patterns. Glass patterns without coherent structure were viewed during the baseline period to ensure neuronal responses reflected perception of structure and not changes in local image features. The spatial distribution of task-related changes in source power was mapped using Synthetic Aperture Magnetometry (SAM), and the time course of activity within areas of maximal power change was determined by calculating time-frequency plots using a Hilbert transform. For six out of eight observers, passive viewing of global structure was associated with a reduction in 10–20 Hz cortical oscillatory power within extrastriate occipital cortex. The location of greatest power change was the same for each pattern type, being close to or within visual area V3a. No peaks of activity were observed in area V1. Time-frequency analyses indicated that neural activity was least for horizontal patterns.ConclusionsWe conclude: (i) visual area V3a is involved in the analysis of global form; (ii) the neural signature for perception of structure, as assessed using MEG, is a reduction in 10–20 Hz oscillatory power; (iii) different neural processes may underlie the perception of horizontal as opposed to radial or rotational structure; and (iv) area V1 is not strongly activated by global form in Glass patterns.

Comparison of different baseline conditions in evaluating factors that influence motor cortex excitability

Identifying task-related changes in cortical excitability requires comparing motor evoked potentials (MEPs) measured under an experimental condition with that obtained in a baseline, control condition. The goal of this study was to compare two different procedures for measuring baseline that are commonly used in transcranial magnetic stimulation (TMS) studies. We hypothesized that baseline measurements obtained during task performance may be elevated due to an overall heightened state of arousal or task-specific fluctuations in excitability. Single-pulse TMS was used to elicit MEPs during an experimental task involving action observation. Baseline MEPs were recorded before (preblock) and during (intrablock) the experimental blocks. Intrablock baseline MEPs were modulated in a manner correlated with the effect of the experimental manipulation. Although there are advantages to obtaining baseline measurements during the experimental block, such measurements are biased by the experimental manipulation. Unbiased baseline measurements are best obtained between experimental blocks.

Optical Imaging: A New Window to the Adult Brain

Noninvasive optical imaging is an emerging method of functional neuroimaging that has major advantages that make it particularly suited to both basic and clinical neuroscience research as well as to clinical practice.2–7 It has great promise for contributing to neuropsychiatry.2 The required equipment is compact and portable, it is relatively easy to use, and the method is relatively tolerant of subject movement. Studies can be performed in almost any location including at the bedside and in natural settings. Patients who are not good candidates for more traditional functional imaging methods (e.g., functional MRI [fMRI] and positron emission tomography [PET]) often do well with optical imaging, as it does not require absolute stillness or confinement and has no associated loud noises. It is also safe to use in the presence of metal (e.g., plates, pins, pacemakers), an important consideration for some populations of interest. It has much faster time resolution than most other functional imaging techniques and can easily provide repeated within-subject measures. Other major advantages are low cost and high safety. Like surface electroencephalography (EEG), optical imaging captures activation-related changes only from the cerebral cortex. Historically, the major disadvantages of optical imaging have been its lower spatial resolution and smaller regions of coverage, areas of major improvement over the last decade. Use of optical imaging for monitoring of cerebral state in high-risk situations (e.g., neurosurgery, intensive care unit), while an important clinical application, is outside the scope of this review.8–10

The default network and processing of personally relevant information: Converging evidence from task-related modulations and functional connectivity

Despite a growing interest in the default network (DN), its composition and function are not fully known. Here we examined whether the DN, as a whole, is specifically active during a task involving judgments about the self, or whether this engagement extends to judgments about a close other. We also aimed to provide converging evidence of DN involvement from across-task functional connectivity, and resting-state functional connectivity analyses, to provide a more comprehensive delineation of this network. Using functional MRI we measured brain activity in young adults during tasks and rest, and utilized a multivariate method to assess task-related changes as well as functional connectivity. An overlapping set of regions showed increased activity for judgments about the self, and about a close other, and strong functional connectivity with the posterior cingulate, a critical node of the DN. These areas included ventromedial prefrontal cortex, posterior parietal cortex, and medial temporal regions, all thought to be part of the DN. Several additional regions, such as the left inferior frontal gyrus and bilateral caudate, also showed the same pattern of activity and connectivity. These results provide evidence that the default network, as an integrated whole, supports internally oriented cognition involving information that is personally relevant, but not limited specifically to the self. They also suggest that the DN may be somewhat more extensive than currently thought.

The role of inhibitory control in behavioral and physiological expressions of toddler executive function

A total of 81 toddlers (24–27 months of age) participated in a biobehavioral investigation of inhibitory control. Maternal report measures of inhibitory control were related to laboratory tasks assessing inhibitory abilities under conditions of conflict, delay, and compliance challenge as well as toddler verbal ability. In addition, unique variance in inhibitory control was explained by task-related changes in brain electrical activity at lateral frontal scalp sites as well as concurrent inhibitory task performance. Implications regarding neural correlates of executive function during early development and a central organizing role of inhibitory processing during toddlerhood are discussed.

Selective Activation of Striatal Fast-Spiking Interneurons during Choice Execution

Basal ganglia circuits are essential for the organization and execution of voluntary actions. Within the striatum, fast-spiking interneurons (FSIs) are thought to tightly regulate the activity of medium-spiny projection neurons (MSNs) through feed-forward inhibition, yet few studies have investigated the functional contributions of FSIs in behaving animals. We recorded presumed MSNs and FSIs together with motor cortex and globus pallidus (GP) neurons, in rats performing a simple choice task. MSN activity was widely distributed across the task sequence, especially near reward receipt. By contrast, FSIs showed a coordinated pulse of increased activity as chosen actions were initiated, in conjunction with a sharp decrease in GP activity. Both MSNs and FSIs were direction selective, but neighboring MSNs and FSIs showed opposite selectivity. Our findings suggest that individual FSIs participate in local striatal information processing, but more global disinhibition of FSIs by GP is important for initiating chosen actions while suppressing unwanted alternatives.

Default network connectivity during a working memory task

The default network exhibits correlated activity at rest and has shown decreased activation during performance of cognitive tasks. There has been little investigation of changes in connectivity of this network during task performance. In this study, we examined task-related modulation of connectivity between two seed regions from the default network posterior cingulated cortex (PCC) and medial prefrontal cortex (mPFC) and the rest of the brain in 12 healthy adults. The purpose was to determine (1) whether connectivity within the default network differs between a resting state and performance of a cognitive (working memory) task and (2) whether connectivity differs between these nodes of the default network and other brain regions, particularly those implicated in cognitive tasks. There was little change in connectivity with the other main areas of the default network for either seed region, but moderate task-related changes in connectivity occurred between seed regions and regions outside the default network. For example, connectivity of the mPFC with the right insula and the right superior frontal gyrus decreased during task performance. Increased connectivity during the working memory task occurred between the PCC and bilateral inferior frontal gyri, and between the mPFC and the left inferior frontal gyrus, cuneus, superior parietal lobule, middle temporal gyrus and cerebellum. Overall, the areas showing greater correlation with the default network seed regions during task than at rest have been previously implicated in working memory tasks. These changes may reflect a decrease in the negative correlations occurring between the default and task-positive networks at rest.

Adaptive, behaviorally gated, persistent encoding of task-relevant auditory information in ferret frontal cortex.

Top-down signals from frontal cortex (FC) are conjectured to play a critical role in cognitive control of sensory processing. To explore this interaction, we compared activity in ferret FC and primary auditory cortex (A1) during auditory and visual tasks requiring discrimination between classes of reference and target stimuli. FC responses were behaviorally-gated, selectively encoded the timing and invariant behavioral meaning of target stimuli, could be rapid in onset, and sometimes persisted for hours following behavior. This mirrors earlier findings in A1that attention triggered rapid, selective, persistent, task-related changes in spectrotemporal receptive fields. Simultaneously recorded local field potentials (LFPs) revealed behaviorally-gated changes in inter-areal coherence, selectively modulated between FC and focal regions of A1 responsive to target sounds. These results suggest that A1 and FC dynamically establish a functional connection during auditory behavior that shapes the flow of sensory information and maintains a persistent trace of recent task-relevant stimulus features.

Modulation of Neuronal Activity in the Monkey Putamen Associated With Changes in the Habitual Order of Sequential Movements

The striatum, especially its dorsolateral part, plays a major role in motor skill learning and habit formation, but it is still unclear how this contribution might be mediated at the neuronal level. We recorded single neurons in the posterior putamen of two monkeys performing an overlearned sequence of arm reaching movements to examine whether task-related activities are sensitive to manipulations of the serial order of stimulus-target locations. The monkeys' capacity to learn sequential regularities was assessed by comparing arm movement latencies and saccadic ocular reactions when a fixed repeating sequence was replaced with a random sequence. We examined neurons classified as phasically active projection neurons (PANs) and tonically active presumed cholinergic interneurons (TANs). About one-third of the PANs (35/106, 33%) activated during specific parts of a trial displayed modulations of their level of activation when the sequential structure was changed. This differential activity consisted of either decreases or increases in activity without altering the time period during which task-related activations occurred. In addition, half of the TANs (41/80, 51%) changed their responses to task stimuli with the sequence switch, indicating that the response selectivity of TANs reflects the detection of the context that requires adaptation to changes in the serial order of stimulus presentations. Our findings suggest that task-related changes in activity of projection neurons may be an important factor contributing to the production and adjustment of sequential behavior executed in an automatic fashion, whereas putative interneurons may provide a signal for performance monitoring in specific contexts.

Noninvasive imaging of prefrontal activation during attention-demanding tasks performed while walking using a wearable optical topography system

Optical topography (OT) based on near-infrared spectroscopy is a noninvasive technique for mapping the relative concentration changes in oxygenated and deoxygenated hemoglobin (oxy- and deoxy-Hb, respectively) in the human cerebral cortex. In our previous study, we developed a small and light wearable optical topography (WOT) system that covers the entire forehead for monitoring prefrontal activation. In the present study, we examine whether the WOT system is applicable to OT measurement while walking, which has been difficult with conventional OT systems. We conduct OT measurements while subjects perform an attention-demanding (AD) task of balancing a ping-pong ball on a small card while walking. The measured time course and power spectra of the relative concentration changes in oxy- and deoxy-Hb show that the step-related changes in the oxy- and deoxy-Hb signals are negligible compared to the task-related changes. Statistical assessment of the task-related changes in the oxy-Hb signals show that the dorsolateral prefrontal cortex and rostral prefrontal area are significantly activated during the AD task. These results suggest that our functional imaging technique with the WOT system is applicable to OT measurement while walking, and will be a powerful tool for evaluating brain activation in a natural environment.

Model-based analysis and quantification of age trends in auditory evoked potentials

Objective The physiological basis for the changes in auditory evoked potentials (AEPs) during development and aging is currently unknown. This study investigates age- and task-related changes via a mathematical model of neuronal activity, which allows a number of physiological changes to be inferred. Methods A quantitative, physiology-based model of activity in cortical and thalamic neurons was used to analyze oddball AEPs recorded from 1498 healthy subjects aged 6–86 years. Results Differences between standard and target responses can be largely explained by differences in connection strengths between thalamic and cortical neurons. The time it takes signals to travel between the thalamus and cortex decreases during development and increases during aging. Strong age trends are also seen in intracortical and thalamocortical neuronal connection strengths. Conclusions Changes in AEP latency can be attributed to changes in the thalamocortical signal propagation time. Large changes in the connection strengths between neuronal populations occur during development, resulting in increased thalamocortical inhibition and decreased thalamocortical excitation. Standard and target parameters are similar in children but diverge during adolescence, due to changes in thalamocortical loop activity. Significance Model-based AEP analysis links age-related changes in brain electrophysiology to underlying changes in brain anatomy and physiology, and yields quantitative predictions of several currently unknown physiological and anatomical properties of the brain.

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Eye blinks are influenced by several external sensory and internal cognitive factors. However, neither the precise temporal effects of these factors on blinking nor how their timing compares between modalities is known. Our aim was to understand the influence of sensory input vs task-relevant information on blinks in the visual and auditory domain. Using a visual and an auditory temporal judgement task, we found that blinks were suppressed during stimulus presentation in both domains and the overall input length had a significant positive relationship with blink latency i.e. the end of blink suppression. Indeed, the effect of sensory input duration on blink latency was not significantly different between visual and auditory stimuli. The precise timing of blink latency was further modulated by the duration of the task relevant input, which was independent of the overall length of sensory input. The influence of task related changes embedded in the overall stimulation suggests an additional influence of top-down processes on blink timing. Intriguingly, embedded changes as short as 40 ms in the auditory domain and 100 ms in the visual domain are reflected in blink latency differences. Importantly, we could show that task accuracy and motor response was not the driving factor of blink modulation. Our results show a sensory domain independent modulation of blink latencies introduced by changes in the length of task-relevant information. Therefore, blinks not only mark the time of sensory input but also can act as precise indicator for periods of cognitive processing and attention.

The effects of everyday concurrent tasks on overground minimum toe clearance and gait parameters

Deaths and injuries resulting from falls are a significant problem for older adults. Over half of falls during walking result from a trip, and these are likely to begin when the foot contacts the ground at the point of minimum toe clearance (MTC) during the swing phase where the foot most closely approaches the ground. MTC is commonly investigated using a limited number of points and on a treadmill, which cannot account for flooring irregularities, speed changes, and direction changes of overground gait. This paper presents a new method of calculating 3D overground MTC that accounts for flooring variations and utilizes hundreds of points on each shoe. These methods are applied to 10 unimpaired adults during habitual gait: (1) without a concurrent task, (2) while carrying a 9-kg laundry basket, (3) while carrying a tray with a full glass of water on it, and (4) while answering standardized conversational questions. Results indicated that steps were slower and shorter during concurrent tasks while MTC changes were dependent on task type (higher for basket, lower for questions, and unchanged for water). Task-related MTC changes were independent of spatiotemporal gait changes. Thus, MTC during overground gait, particularly while concurrent tasks are being performed, may be an independent fall risk factor that merits further investigation in subjects at-risk of falls. The relationships between MTC, gait parameters, and older age or fall risk should be explored further in at-risk subjects and circumstances to elucidate potential tripping mechanisms.

Interactions between systemic hemodynamics and cerebral blood flow during attentional processing

The study explored interactions between systemic hemodynamics and cerebral blood flow during attentional processing. Using transcranial Doppler sonography, blood flow velocities in the middle cerebral arteries (MCA) of both hemispheres were recorded while 50 subjects performed a cued reaction time task. Finger arterial pressure and heart rate were also continuously monitored. Doppler sonography revealed a right dominant blood flow response. The extent of the increase measured in second two of the interstimulus interval showed a clear positive association with reaction speed. Task-related changes in blood pressure and heart rate proved predictive of changes in MCA flow velocities in limited time windows of the response. Besides an association between cerebral blood flow and attentional performance, the results suggest a marked impact of systemic hemodynamics on the blood flow response. All observed interactions are highly dynamic in time.

Autonomic predictors of Stroop performance in young and middle-aged adults

Although changes in autonomic activity have been extensively examined as responses to cognitive challenges, relatively few studies have used individual differences in autonomic parameters to predict executive performance in healthy adults. Here we examined baseline and task-related changes in heart rate and heart rate variability (measured by respiratory sinus arrhythmia (RSA)) to predict performance of a pictorial Stroop task in a group of 81 healthy adults aged 17–55. Greater autonomic reactivity (increased heart rate and reduced RSA for task performance) was associated with faster colour naming of faces in the Stroop task. Dividing the group by median age revealed that middle-aged adults reduced RSA to a greater degree than their younger counterparts in the context of equivalent performance across groups. Findings suggest that performance of executive function tasks that evoke attentional control may depend in part on the responsiveness of autonomic control parameters via age-dependent mechanisms.

Frontal brain activation in young children during picture book reading with their mothers. Acta Paediatr 2010, Ohgi et al.

Acta PaediatricaVolume 99, Issue 2 p. 320-321 Free Access Frontal brain activation in young children during picture book reading with their mothers. Acta Paediatr 2010, Ohgi et al. This article corrects the following: Frontal brain activation in young children during picture book reading with their mothers S Ohgi, KK Loo, C Mizuike, Volume 99Issue 2Acta Pædiatrica pages: 225-229 First Published online: October 22, 2009 First published: 08 January 2010 https://doi.org/10.1111/j.1651-2227.2009.01681.xAboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL The authors of the above mentioned article (1), published in the current issue of Acta Paediatrica would like to correct the errors in 2-4 (pp. 227–228). The correct figures should be: Figure 2Open in figure viewerPowerPoint Time course and total average oxy-Hb values. Average task-related changes of oxy-Hb signals from an arbitrary zero baseline at the start of the measurement period were calculated for each 30-sec epoch. The results of task-related changes of oxy-Hb values between the two tasks conditions are presented above for the right (upper figure) and left (lower figure) frontal areas. Time-course changes of oxy-Hb values were significantly increased in response to Task 1 vs Task 2 in both frontal areas. Similarly, total averages of oxy-Hb values in both frontal areas were observed in Task 1 compared with Task 2. Figure 3Open in figure viewerPowerPoint Mothers’ and Children’s Verbal and Non-verbal Behaviours. Frequency of mothers’ and children’s verbalizations and their pointing behaviours were significantly higher in frequency in Task 1 compared with Task 2. AR = Attention-recruiting; E = Elaborations, Q = Question and F = Feedback. Figure 4Open in figure viewerPowerPoint Correlation between average values of oxy-Hb and mothers’ and children’s verbal behaviours during picture book reading. Correlation between values of oxy-Hb and mothers’ total verbalizations during Task 1 is shown. Significantly positive correlations between average values of oxy-Hb and mothers’ total verbalizations were observed in both frontal areas (upper figure; right, lower figure; left). Reference 1 Ohgi S, Loo KK, Mizuike C. Frontal brain activation in young children during picture book reading with their mothers. Acta Paediatr 2010; 99: 225– 9. Volume99, Issue2February 2010Pages 320-321 FiguresReferencesRelatedInformation

Optimized beamforming for simultaneous MEG and intracranial local field potential recordings in deep brain stimulation patients

Insight into how brain structures interact is critical for understanding the principles of functional brain architectures and may lead to better diagnosis and therapy for neuropsychiatric disorders. We recorded, simultaneously, magnetoencephalographic (MEG) signals and subcortical local field potentials (LFP) in a Parkinson's disease (PD) patient with bilateral deep brain stimulation (DBS) electrodes in the subthalamic nucleus (STN). These recordings offer a unique opportunity to characterize interactions between the subcortical structures and the neocortex. However, high-amplitude artefacts appeared in the MEG. These artefacts originated from the percutaneous extension wire, rather than from the actual DBS electrode and were locked to the heart beat. In this work, we show that MEG beamforming is capable of suppressing these artefacts and quantify the optimal regularization required. We demonstrate how beamforming makes it possible to localize cortical regions whose activity is coherent with the STN-LFP, extract artefact-free virtual electrode time-series from regions of interest and localize cortical areas exhibiting specific task-related power changes. This furnishes results that are consistent with previously reported results using artefact-free MEG data. Our findings demonstrate that physiologically meaningful information can be extracted from heavily contaminated MEG signals and pave the way for further analysis of combined MEG-LFP recordings in DBS patients.

Modification of effective connectivity of cerebro-cerebellar loop by movement of the opposing limb

Parkinson's disease (PD) reportedly includes altered connectivity of neural loops involving the basal ganglia and cerebellum, although little is known regarding any changes in the connectivity of motor loops. The goal of this study was to further understand the connectivity within the basal ganglia–thalamo-motor (BGTM) and cerebro-cerebellar (CC) loops in PD. Twelve PD patients and 12 age-matched control subjects performed a protocol involving self-initiated (SI) and externally-triggered (ET) finger movements, while being scanned with functional magnetic resonance imaging. Compared with the control subjects, the PD subjects showed hypo-activation in the bilateral putamen, right supplementary motor area and hyper-activation in the right premotor cortex. In the sensorimotor cortex and cerebellar hemisphere, PD subjects tended to show hyper-activation in a main effects analysis, but hypo-activation in a linear effects analysis. Analysis using structural equation modeling (SEM) revealed significant positive interactions within the right BGTM loop during the SI task and within the right (right cerebral hemisphere–left cerebellum) CC loop during the ET task. SEM also revealed task-related quantitative changes between the thalamus and the motor cortices in the control subjects. We found that the PD patients showed reduced connectivity in the right BGTM loop and inter-hemispheric connections in SEM, which is the first demonstration of this phenomenon. Interestingly, PD patients exhibited preserved connectivity within the right CC loop during the ET task. These results suggest disruption of cortico-striatal processing and preservation of relatively intact neural circuits that do not involve the basal ganglia in PD.

Visual mismatch negativity to irrelevant changes is sensitive to task-relevant changes

Event-related potentials (ERPs) were measured in response to frequent (standard) and infrequent (deviant) task-irrelevant bar patterns. The constituent bars of the deviant patterns had either different orientation or different color than the bars of the standard. The task was the detection of either the orientation or the color change of a centrally presented shape. The deviant minus the standard ERP difference produced posterior negativity and was identified as visual mismatch negativity (vMMN). On the one hand, vMMN to orientation deviancy had smaller amplitude in the task demanding detection of the orientation change, and vMMN to color deviancy had smaller amplitude in the task demanding the color change. On the other hand, irrelevant deviancy influenced the task-performance. Reaction time (RT) to the orientation change of the target shape was longer in sequences with orientation change in the background, whereas RT to color change was longer in sequences with color change in the background. This interaction suggested that there was competition between the processing of irrelevant stimuli that share characteristics of task-related changes and target-related processing.

Cervical cord functional MRI changes in relapse-onset MS patients

ObjectiveTo investigate whether (1) the tactile-associated cord functional MRI (fMRI) changes vary in the different clinical stages of relapse-onset multiple sclerosis (MS), and (2) the pattern of cord fMRI changes...