Publications by authors named "Aina Puce"

61 Publications

EEG measures for clinical research in major vascular cognitive impairment: recommendations by an expert panel.

Neurobiol Aging 2021 Jul 10;103:78-97. Epub 2021 Mar 10.

Centre for Healthy Brain Ageing (CHeBA), School of Psychiatry, University of New South Wales; Neuropsychiatric Institute, The Prince of Wales Hospital, Sydney, Australia.

Vascular contribution to cognitive impairment (VCI) and dementia is related to etiologies that may affect the neurophysiological mechanisms regulating brain arousal and generating electroencephalographic (EEG) activity. A multidisciplinary expert panel reviewed the clinical literature and reached consensus about the EEG measures consistently found as abnormal in VCI patients with dementia. As compared to cognitively unimpaired individuals, those VCI patients showed (1) smaller amplitude of resting state alpha (8-12 Hz) rhythms dominant in posterior regions; (2) widespread increases in amplitude of delta (< 4 Hz) and theta (4-8 Hz) rhythms; and (3) delayed N200/P300 peak latencies in averaged event-related potentials, especially during the detection of auditory rare target stimuli requiring participants' responses in "oddball" paradigms. The expert panel formulated the following recommendations: (1) the above EEG measures are not specific for VCI and should not be used for its diagnosis; (2) they may be considered as "neural synchronization" biomarkers to enlighten the relationships between features of the VCI-related cerebrovascular lesions and abnormalities in neurophysiological brain mechanisms; and (3) they may be tested in future clinical trials as prognostic biomarkers and endpoints of interventions aimed at normalizing background brain excitability and vigilance in wakefulness.
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http://dx.doi.org/10.1016/j.neurobiolaging.2021.03.003DOI Listing
July 2021

Statistical power: Implications for planning MEG studies.

Neuroimage 2021 06 16;233:117894. Epub 2021 Mar 16.

Institut du Cerveau, ICM, Inserm U 1127, CNRS UMR 7225, Sorbonne Université, Centre MEG-EEG, Centre de NeuroImagerie Recherche (CENIR), 47 Boulevard de l'hôpital, 75013 Paris, France.

Statistical power is key for robust, replicable science. Here, we systematically explored how numbers of trials and subjects affect statistical power in MEG sensor-level data. More specifically, we simulated "experiments" using the MEG resting-state dataset of the Human Connectome Project (HCP). We divided the data in two conditions, injected a dipolar source at a known anatomical location in the "signal condition", but not in the "noise condition", and detected significant differences at sensor level with classical paired t-tests across subjects, using amplitude, squared amplitude, and global field power (GFP) measures. Group-level detectability of these simulated effects varied drastically with anatomical origin. We thus examined in detail which spatial properties of the sources affected detectability, looking specifically at the distance from closest sensor and orientation of the source, and at the variability of these parameters across subjects. In line with previous single-subject studies, we found that the most detectable effects originate from source locations that are closest to the sensors and oriented tangentially with respect to the head surface. In addition, cross-subject variability in orientation also affected group-level detectability, boosting detection in regions where this variability was small and hindering detection in regions where it was large. Incidentally, we observed a considerable covariation of source position, orientation, and their cross-subject variability in individual brain anatomical space, making it difficult to assess the impact of each of these variables independently of one another. We thus also performed simulations where we controlled spatial properties independently of individual anatomy. These additional simulations confirmed the strong impact of distance and orientation and further showed that orientation variability across subjects affects detectability, whereas position variability does not. Importantly, our study indicates that strict unequivocal recommendations as to the ideal number of trials and subjects for any experiment cannot be realistically provided for neurophysiological studies and should be adapted according to the brain regions under study.
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http://dx.doi.org/10.1016/j.neuroimage.2021.117894DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8148377PMC
June 2021

Differential effects of propofol and ketamine on critical brain dynamics.

PLoS Comput Biol 2020 12 21;16(12):e1008418. Epub 2020 Dec 21.

Department of Physics, Indiana University, Bloomington, Indiana, USA.

Whether the brain operates at a critical "tipping" point is a long standing scientific question, with evidence from both cellular and systems-scale studies suggesting that the brain does sit in, or near, a critical regime. Neuroimaging studies of humans in altered states of consciousness have prompted the suggestion that maintenance of critical dynamics is necessary for the emergence of consciousness and complex cognition, and that reduced or disorganized consciousness may be associated with deviations from criticality. Unfortunately, many of the cellular-level studies reporting signs of criticality were performed in non-conscious systems (in vitro neuronal cultures) or unconscious animals (e.g. anaesthetized rats). Here we attempted to address this knowledge gap by exploring critical brain dynamics in invasive ECoG recordings from multiple sessions with a single macaque as the animal transitioned from consciousness to unconsciousness under different anaesthetics (ketamine and propofol). We use a previously-validated test of criticality: avalanche dynamics to assess the differences in brain dynamics between normal consciousness and both drug-states. Propofol and ketamine were selected due to their differential effects on consciousness (ketamine, but not propofol, is known to induce an unusual state known as "dissociative anaesthesia"). Our analyses indicate that propofol dramatically restricted the size and duration of avalanches, while ketamine allowed for more awake-like dynamics to persist. In addition, propofol, but not ketamine, triggered a large reduction in the complexity of brain dynamics. All states, however, showed some signs of persistent criticality when testing for exponent relations and universal shape-collapse. Further, maintenance of critical brain dynamics may be important for regulation and control of conscious awareness.
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http://dx.doi.org/10.1371/journal.pcbi.1008418DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7785236PMC
December 2020

Editorial: Where the rubber meets the road in visual perception: High temporal-precision brain signals to top-down and bottom-up influences on perceptual resolution.

Eur J Neurosci 2020 12 23;52(11):4403-4410. Epub 2020 Nov 23.

Department of Psychology, University of Florida, Gainesville, FL, USA.

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http://dx.doi.org/10.1111/ejn.15036DOI Listing
December 2020

Issues and recommendations from the OHBM COBIDAS MEEG committee for reproducible EEG and MEG research.

Nat Neurosci 2020 12 21;23(12):1473-1483. Epub 2020 Sep 21.

Department of Psychological & Brain Sciences, Indiana University, Bloomington, IN, United States.

The Organization for Human Brain Mapping (OHBM) has been active in advocating for the instantiation of best practices in neuroimaging data acquisition, analysis, reporting and sharing of both data and analysis code to deal with issues in science related to reproducibility and replicability. Here we summarize recommendations for such practices in magnetoencephalographic (MEG) and electroencephalographic (EEG) research, recently developed by the OHBM neuroimaging community known by the abbreviated name of COBIDAS MEEG. We discuss the rationale for the guidelines and their general content, which encompass many topics under active discussion in the field. We highlight future opportunities and challenges to maximizing the sharing and exploitation of MEG and EEG data, and we also discuss how this 'living' set of guidelines will evolve to continually address new developments in neurophysiological assessment methods and multimodal integration of neurophysiological data with other data types.
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http://dx.doi.org/10.1038/s41593-020-00709-0DOI Listing
December 2020

Editorial overview: The 25th Anniversary of the Human Brain Mapping Meeting.

Neuroimage 2019 10 5;200:704-705. Epub 2019 Apr 5.

OHBM Program Committee, Université de Bordeaux, France. Electronic address:

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http://dx.doi.org/10.1016/j.neuroimage.2019.04.018DOI Listing
October 2019

Reply to "Clinical practice guidelines or clinical research guidelines?"

Clin Neurophysiol 2018 09 3;129(9):2056-2057. Epub 2018 Jul 3.

I-LABS MEG Brain Imaging Center, University of Washington, Seattle, WA, USA. Electronic address:

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http://dx.doi.org/10.1016/j.clinph.2018.06.016DOI Listing
September 2018

IFCN-endorsed practical guidelines for clinical magnetoencephalography (MEG).

Clin Neurophysiol 2018 08 17;129(8):1720-1747. Epub 2018 Apr 17.

Institute for Learning & Brain Sciences, University of Washington, Seattle, WA, USA; Department of Physics, University of Washington, Seattle, WA, USA.

Magnetoencephalography (MEG) records weak magnetic fields outside the human head and thereby provides millisecond-accurate information about neuronal currents supporting human brain function. MEG and electroencephalography (EEG) are closely related complementary methods and should be interpreted together whenever possible. This manuscript covers the basic physical and physiological principles of MEG and discusses the main aspects of state-of-the-art MEG data analysis. We provide guidelines for best practices of patient preparation, stimulus presentation, MEG data collection and analysis, as well as for MEG interpretation in routine clinical examinations. In 2017, about 200 whole-scalp MEG devices were in operation worldwide, many of them located in clinical environments. Yet, the established clinical indications for MEG examinations remain few, mainly restricted to the diagnostics of epilepsy and to preoperative functional evaluation of neurosurgical patients. We are confident that the extensive ongoing basic MEG research indicates potential for the evaluation of neurological and psychiatric syndromes, developmental disorders, and the integrity of cortical brain networks after stroke. Basic and clinical research is, thus, paving way for new clinical applications to be identified by an increasing number of practitioners of MEG.
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http://dx.doi.org/10.1016/j.clinph.2018.03.042DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6045462PMC
August 2018

A Review of Issues Related to Data Acquisition and Analysis in EEG/MEG Studies.

Brain Sci 2017 May 31;7(6). Epub 2017 May 31.

Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA.

Electroencephalography (EEG) and magnetoencephalography (MEG) are non-invasive electrophysiological methods, which record electric potentials and magnetic fields due to electric currents in synchronously-active neurons. With MEG being more sensitive to neural activity from tangential currents and EEG being able to detect both radial and tangential sources, the two methods are complementary. Over the years, neurophysiological studies have changed considerably: high-density recordings are becoming de rigueur; there is interest in both spontaneous and evoked activity; and sophisticated artifact detection and removal methods are available. Improved head models for source estimation have also increased the precision of the current estimates, particularly for EEG and combined EEG/MEG. Because of their complementarity, more investigators are beginning to perform simultaneous EEG/MEG studies to gain more complete information about neural activity. Given the increase in methodological complexity in EEG/MEG, it is important to gather data that are of high quality and that are as artifact free as possible. Here, we discuss some issues in data acquisition and analysis of EEG and MEG data. Practical considerations for different types of EEG and MEG studies are also discussed.
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http://dx.doi.org/10.3390/brainsci7060058DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5483631PMC
May 2017

Socio-emotionally significant experience and children's processing of irrelevant auditory stimuli.

Int J Psychophysiol 2017 02 16;112:52-63. Epub 2016 Dec 16.

Department of Psychology, Center for Brain, Biology and Behavior, C88, East Stadium, P.O Box 880156, University of Nebraska-Lincoln, Lincoln, NE 68588-0156, United States.

Theory and research indicate considerable influence of socio-emotionally significant experiences on children's functioning and adaptation. In the current study, we examined neurophysiological correlates of children's allocation of information processing resources to socio-emotionally significant events, specifically, simulated marital interactions. We presented 9- to 11-year-old children (n=24; 11 females) with 15 videos of interactions between two actors posing as a married couple. Task-irrelevant brief auditory probes were presented during the videos, and event-related potentials (ERPs) elicited to the auditory probes were measured. As hypothesized, exposure to higher levels of interparental conflict was associated with smaller P1, P2, and N2 ERPs to the probes. This finding is consistent with the idea that children who had been exposed to more interparental conflict attended more to the videos and diverted fewer cognitive resources to processing the probes, thereby producing smaller ERPs to the probes. In addition, smaller N2s were associated with more child behavior problems, suggesting that allocating fewer processing resources to the probes was associated with more problem behavior. Results are discussed in terms of implications of socio-emotionally significant experiences for children's processing of interpersonal interactions.
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http://dx.doi.org/10.1016/j.ijpsycho.2016.12.006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5515239PMC
February 2017

Same Intervention-Different Reorganization: The Impact of Lesion Location on Training-Facilitated Somatosensory Recovery After Stroke.

Neurorehabil Neural Repair 2016 11 20;30(10):988-1000. Epub 2016 Jun 20.

The Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Melbourne, Victoria, Australia.

Background: The brain may reorganize to optimize stroke recovery. Yet relatively little is known about neural correlates of training-facilitated recovery, particularly after loss of body sensations.

Objective: Our aim was to characterize changes in brain activation following clinically effective touch discrimination training in stroke patients with somatosensory loss after lesions of primary/secondary somatosensory cortices or thalamic/capsular somatosensory regions using functional magnetic resonance imaging (fMRI).

Methods: Eleven stroke patients with somatosensory loss, 7 with lesions involving primary (S1) and/or secondary (S2) somatosensory cortex (4 male, 58.7 ± 13.3 years) and 4 with lesions primarily involving somatosensory thalamus and/or capsular/white matter regions (2 male, 58 ± 8.6 years) were studied. Clinical and MRI testing occurred at 6 months poststroke (preintervention), and following 15 sessions of clinically effective touch discrimination training (postintervention).

Results: Improved touch discrimination of a magnitude similar to previous clinical studies and approaching normal range was found. Patients with thalamic/capsular somatosensory lesions activated preintervention in left ipsilesional supramarginal gyrus, and postintervention in ipsilesional insula and supramarginal gyrus. In contrast, those with S1/S2 lesions did not show common activation preintervention, only deactivation in contralesional superior parietal lobe, including S1, and cingulate cortex postintervention. The S1/S2 group did, however, show significant change over time involving ipsilesional precuneus. This change was greater than for the thalamic/capsular group (P = .012; d = -2.43; CI = -0.67 to -3.76).

Conclusion: Different patterns of change in activation are evident following touch discrimination training with thalamic/capsular lesions compared with S1/S2 cortical somatosensory lesions, despite common training and similar improvement.
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http://dx.doi.org/10.1177/1545968316653836DOI Listing
November 2016

Editorial: Facing the Other: Novel Theories and Methods in Face Perception Research.

Front Hum Neurosci 2016 8;10:32. Epub 2016 Feb 8.

Perception in Action Research Centre, and ARC Centre of Excellence in Cognition and its Disorders, Department of Cognitive Science, Faculty of Human Sciences, Macquarie University Sydney, NSW, Australia.

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http://dx.doi.org/10.3389/fnhum.2016.00032DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4744850PMC
February 2016

Something to sink your teeth into: The presence of teeth augments ERPs to mouth expressions.

Neuroimage 2016 Feb 17;127:227-241. Epub 2015 Dec 17.

Indiana University-Bloomington, USA. Electronic address:

If the whites of the sclera can impact neural processing of eye expressions (Hardee, Thompson, & Puce, 2008; Whalen et al., 1998), do seen teeth affect neural responses to mouth expressions? Twenty participants (10 females; ages 22-31) viewed avatar mouth images depicting grimaces, smiles and open mouth expressions that were presented with and without teeth. A continuous 256 channel electroencephalogram (EEG) was recorded while subjects completed two tasks: an implicit task evaluating stimulus color and an explicit task evaluating mouth expression valence. Event related potential (ERP) peak amplitudes and latencies and area under the curve (AUC) were measured in individual subject averaged ERPs. Statistical testing revealed a main effect of the presence of Teeth for P100, N170, and vertex positive potential (VPP) amplitudes and for slow positive wave (SPW) AUC. Task by teeth interactions occurred for P250 amplitude, underscoring how explicit task demands can influence neural processing. Arousal ratings co-varied with teeth presence, suggesting that low-level visual features such as teeth may drive the saliency of emotional expressions, and lie at the core of differences in neural processing to different emotional expressions.
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http://dx.doi.org/10.1016/j.neuroimage.2015.12.020DOI Listing
February 2016

On dissociating the neural time course of the processing of positive emotions.

Neuropsychologia 2016 Mar 11;83:123-137. Epub 2015 Dec 11.

Department of Psychological Sciences, Indiana University, Bloomington, IN, USA. Electronic address:

Providing evidence for categorical theories of emotion mandates the inclusion of discrete emotion categories beyond the typical six "basic" emotions. Traditional neurophysiological investigations of emotion typically feature the six basic emotions with happiness as the lone positive exemplar. Here we studied how event-related potentials (ERPs) might differentiate between two positive emotional expressions: happiness and pride, and if so, at what time interval. Furthermore, given divergent findings in the ERP literature with respect to viewing emotional expressions, we explicitly examined how task type modulates neurophysiological responses when the same stimuli are viewed. While a continuous electroencephalogram (EEG) was recorded, 20 healthy participants completed two tasks: an implicit task where participants judged whether or not a face featured a brown spot (freckle), and an explicit task where they judged the face as portraying a "happy," "proud," or "neutral" expression. Behavioral performance exceeded 90% accuracy on both tasks. In the explicit task, participants responded faster and more accurately for Happy compared to Proud and Neutral expressions. Neurophysiologically, amplitudes for N170, VPP and P250 ERPs differentiated emotional from neutral expressions, but not from each other. In contrast, the late SPW component significantly differentiated Happy and Proud expressions from each other. Moreover, main effects of Task were found for the VPP, P250, LPP and SPW; additionally, Emotion X Task interactions were observed for P250 and SPW. Our data stress that task demands may magnify or diminish neural processing differences between emotion categories, which therefore cannot be disentangled with a single experimental paradigm. Additionally, some ERP differences may also reflect variations in categorization difficulty.
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http://dx.doi.org/10.1016/j.neuropsychologia.2015.12.001DOI Listing
March 2016

Nodal centrality of functional network in the differentiation of schizophrenia.

Schizophr Res 2015 Oct 20;168(1-2):345-52. Epub 2015 Aug 20.

Imaging Research Facility, Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, USA.

A disturbance in the integration of information during mental processing has been implicated in schizophrenia, possibly due to faulty communication within and between brain regions. Graph theoretic measures allow quantification of functional brain networks. Functional networks are derived from correlations between time courses of brain regions. Group differences between SZ and control groups have been reported for functional network properties, but the potential of such measures to classify individual cases has been little explored. We tested whether the network measure of betweenness centrality could classify persons with schizophrenia and normal controls. Functional networks were constructed for 19 schizophrenic patients and 29 non-psychiatric controls based on resting state functional MRI scans. The betweenness centrality of each node, or fraction of shortest-paths that pass through it, was calculated in order to characterize the centrality of the different regions. The nodes with high betweenness centrality agreed well with hub nodes reported in previous studies of structural and functional networks. Using a linear support vector machine algorithm, the schizophrenia group was differentiated from non-psychiatric controls using the ten nodes with the highest betweenness centrality. The classification accuracy was around 80%, and stable against connectivity thresholding. Better performance was achieved when using the ranks as feature space as opposed to the actual values of betweenness centrality. Overall, our findings suggest that changes in functional hubs are associated with schizophrenia, reflecting a variation of the underlying functional network and neuronal communications. In addition, a specific network property, betweenness centrality, can classify persons with SZ with a high level of accuracy.
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http://dx.doi.org/10.1016/j.schres.2015.08.011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4591247PMC
October 2015

Neurophysiological Correlates of Children’s Processing of Interparental Conflict Cues.

J Fam Psychol 2015 Aug;29(4):518-27

This study builds on the literature on child exposure to marital conflict by testing whether mother-reported marital conflict exposure predicts a child’s P3 event-related potential (ERP) components generated in response to viewing quasi–marital conflict photos. We collected ERP data from 23 children (9–11 years of age) while presenting photos of actors pretending to be a couple depicting interpersonal anger, happiness, and neutrality. To elicit the P3 ERP, stimuli were presented using an oddball paradigm, with angry and happy photos presented on 20% of trials each and neutral photos presented on the remaining 60% of trials. Angry photos were the target in 1 block, and happy photos were the target in the other block. In the angry block, children from high-conflict homes had shorter reaction times (RTs) on happy trials than on neutral trials, and children from low-conflict homes had shorter RTs on angry trials than on happy trials. Also within the angry block, children generated larger P3s on angry trials than on happy trials, regardless of exposure to conflict. Further, children from high-conflict homes generated larger P3s on angry trials and on happy trials compared with neutral trials, but children from low-conflict homes did not. Results are discussed in terms of implications for children’s processing of displays of interpersonal emotion.
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http://dx.doi.org/10.1037/fam0000088DOI Listing
August 2015

Extrastriate visual cortex reorganizes despite sequential bilateral occipital stroke: implications for vision recovery.

Front Hum Neurosci 2015 28;9:224. Epub 2015 Apr 28.

Behavioural Neuroscience, Florey Institute for Neuroscience and Mental Health, University of Melbourne Melbourne, VIC, Australia.

The extent of visual cortex reorganization following injury remains controversial. We report serial functional magnetic resonance imaging (fMRI) data from a patient with sequential posterior circulation strokes occurring 3 weeks apart, compared with data from an age-matched healthy control subject. At 8 days following a left occipital stroke, contralesional visual cortical activation was within expected striate and extrastriate sites, comparable to that seen in controls. Despite a further infarct in the right (previously unaffected hemisphere), there was evolution of visual cortical reorganization progressed. In this patient, there was evidence of utilization of peri-infarct sites (right-sided) and recruitment of new activation sites in extrastriate cortices, including in the lateral middle and inferior temporal lobes. The changes over time corresponded topographically with the patient's lesion site and its connections. Reorganization of the surviving visual cortex was demonstrated 8 days after the first stroke. Ongoing reorganization in extant cortex was demonstrated at the 6 month scan. We present a summary of mechanisms of recovery following stroke relevant to the visual system. We conclude that mature primary visual cortex displays considerable plasticity and capacity to reorganize, associated with evolution of visual field deficits. We discuss these findings and their implications for therapy within the context of current concepts in visual compensatory and restorative therapies.
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http://dx.doi.org/10.3389/fnhum.2015.00224DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4412053PMC
May 2015

Social decisions affect neural activity to perceived dynamic gaze.

Soc Cogn Affect Neurosci 2015 Nov 28;10(11):1557-67. Epub 2015 Apr 28.

Psychological and Brain Sciences, Indiana University, Bloomington IN, USA,

Gaze direction, a cue of both social and spatial attention, is known to modulate early neural responses to faces e.g. N170. However, findings in the literature have been inconsistent, likely reflecting differences in stimulus characteristics and task requirements. Here, we investigated the effect of task on neural responses to dynamic gaze changes: away and toward transitions (resulting or not in eye contact). Subjects performed, in random order, social (away/toward them) and non-social (left/right) judgment tasks on these stimuli. Overall, in the non-social task, results showed a larger N170 to gaze aversion than gaze motion toward the observer. In the social task, however, this difference was no longer present in the right hemisphere, likely reflecting an enhanced N170 to gaze motion toward the observer. Our behavioral and event-related potential data indicate that performing social judgments enhances saliency of gaze motion toward the observer, even those that did not result in gaze contact. These data and that of previous studies suggest two modes of processing visual information: a 'default mode' that may focus on spatial information; a 'socially aware mode' that might be activated when subjects are required to make social judgments. The exact mechanism that allows switching from one mode to the other remains to be clarified.
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http://dx.doi.org/10.1093/scan/nsv049DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4631155PMC
November 2015

Photographic but not line-drawn faces show early perceptual neural sensitivity to eye gaze direction.

Front Hum Neurosci 2015 10;9:185. Epub 2015 Apr 10.

Cognitive Science Program, Indiana University Bloomington, IN, USA ; Program in Neuroscience, Indiana University Bloomington, IN, USA ; Department of Psychological and Brain Sciences, Indiana University Bloomington, IN, USA.

Our brains readily decode facial movements and changes in social attention, reflected in earlier and larger N170 event-related potentials (ERPs) to viewing gaze aversions vs. direct gaze in real faces (Puce et al., 2000). In contrast, gaze aversions in line-drawn faces do not produce these N170 differences (Rossi et al., 2014), suggesting that physical stimulus properties or experimental context may drive these effects. Here we investigated the role of stimulus-induced context on neurophysiological responses to dynamic gaze. Sixteen healthy adults viewed line-drawn and real faces, with dynamic eye aversion and direct gaze transitions, and control stimuli (scrambled arrays and checkerboards) while continuous electroencephalographic (EEG) activity was recorded. EEG data from 2 temporo-occipital clusters of 9 electrodes in each hemisphere where N170 activity is known to be maximal were selected for analysis. N170 peak amplitude and latency, and temporal dynamics from Event-Related Spectral Perturbations (ERSPs) were measured in 16 healthy subjects. Real faces generated larger N170s for averted vs. direct gaze motion, however, N170s to real and direct gaze were as large as those to respective controls. N170 amplitude did not differ across line-drawn gaze changes. Overall, bilateral mean gamma power changes for faces relative to control stimuli occurred between 150-350 ms, potentially reflecting signal detection of facial motion. Our data indicate that experimental context does not drive N170 differences to viewed gaze changes. Low-level stimulus properties, such as the high sclera/iris contrast change in real eyes likely drive the N170 changes to viewed aversive movements.
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http://dx.doi.org/10.3389/fnhum.2015.00185DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4392689PMC
April 2015

White matter abnormalities of microstructure and physiological noise in schizophrenia.

Brain Imaging Behav 2015 Dec;9(4):868-77

Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, 47405, USA.

White matter abnormalities in schizophrenia have been revealed by many imaging techniques and analysis methods. One of the findings by diffusion tensor imaging is a decrease in fractional anisotropy (FA), which is an indicator of white matter integrity. On the other hand, elevation of metabolic rate in white matter was observed from positron emission tomography (PET) studies. In this report, we aim to compare the two structural and functional effects on the same subjects. Our comparison is based on the hypothesis that signal fluctuation in white matter is associated with white matter functional activity. We examined the variance of the signal in resting state fMRI and found significant differences between individuals with schizophrenia and non-psychiatric controls specifically in white matter tissue. Controls showed higher temporal signal-to-noise ratios clustered in regions including temporal, frontal, and parietal lobes, cerebellum, corpus callosum, superior longitudinal fasciculus, and other major white matter tracts. These regions with higher temporal signal-to-noise ratio agree well with those showing higher metabolic activity reported by studies using PET. The results suggest that individuals with schizophrenia tend to have higher functional activity in white matter in certain brain regions relative to healthy controls. Despite some overlaps, the distinct regions for physiological noise are different from those for FA derived from diffusion tensor imaging, and therefore provide a unique angle to explore potential mechanisms to white matter abnormality.
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http://dx.doi.org/10.1007/s11682-014-9349-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4492900PMC
December 2015

Disrupted modular architecture of cerebellum in schizophrenia: a graph theoretic analysis.

Schizophr Bull 2014 Nov 29;40(6):1216-26. Epub 2014 Apr 29.

Recent studies of schizophrenia have revealed cognitive and memory deficits that are accompanied by disruptions of neuronal connectivity in cortical and subcortical brain regions. More recently, alterations of topological organization of structural networks in schizophrenia are also being identified using graph theoretical analysis. However, the role of the cerebellum in this network structure remains largely unknown. In this study, global network measures obtained from diffusion tensor imaging were computed in the cerebella of 25 patients with schizophrenia and 36 healthy volunteers. While cerebellar global network characteristics were slightly altered in schizophrenia patients compared with healthy controls, the patients showed a retained small-world network organization. The modular architecture, however, was changed mainly in crus II. Furthermore, schizophrenia patients had reduced correlations between modularity and microstructural integrity, as measured by fractional anisotropy (FA) in lobules I-IV and X. Finally, FA alterations were significantly correlated with the Positive and Negative Syndrome Scale symptom scores in schizophrenia patients. Taken together, our data suggest that schizophrenia patients have altered network architecture in the cerebellum with reduced local microstructural connectivity and that cerebellar structural abnormalities are associated symptoms of the disorder.
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http://dx.doi.org/10.1093/schbul/sbu059DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4193723PMC
November 2014

Neural correlates of apparent motion perception of impoverished facial stimuli: a comparison of ERP and ERSP activity.

Neuroimage 2014 Sep 13;98:442-459. Epub 2014 Apr 13.

Cognitive Science Program, Indiana University, Bloomington, IN, USA.

Our brains readily decode human movements, as shown by neural responses to face and body motion. N170 event-related potentials (ERPs) are earlier and larger to mouth opening movements relative to closing in both line-drawn and natural faces, and gaze aversions relative to direct gaze in natural faces (Puce and Perrett, 2003; Puce et al., 2000). Here we extended this work by recording both ERP and oscillatory EEG activity (event-related spectral perturbations, ERSPs) to line-drawn faces depicting eye and mouth movements (Eyes: Direct vs Away; Mouth: Closed vs Open) and non-face motion controls. Neural activity was measured in 2 occipito-temporal clusters of 9 electrodes, one in each hemisphere. Mouth opening generated larger N170s than mouth closing, replicating earlier work. Eye motion elicited robust N170s that did not differ between gaze conditions. Control condition differences were seen, and generated the largest N170. ERSP difference plots across conditions in the occipito-temporal electrode clusters (Eyes: Direct vs Away; Mouth: Closed vs Open) showed statistically significant differences in beta and gamma bands for gaze direction changes and mouth opening at similar post-stimulus times and frequencies. In contrast, control stimuli showed activity in the gamma band with a completely different time profile and hemispheric distribution to facial stimuli. ERSP plots were generated in two 9 electrode clusters centered on central sites, C3 and C4. In the left cluster for all stimulus conditions, broadband beta suppression persisted from about 250ms post-motion onset. In the right cluster, beta suppression was seen for control conditions only. Statistically significant differences between conditions were confined between 4 and 15Hz, unlike the occipito-temporal sites where differences occurred at much higher frequencies (high beta/gamma). Our data indicate that N170 amplitude is sensitive to the amount of movement in the visual field, independent of stimulus type. In contrast, occipito-temporal beta and gamma activity differentiates between facial and non-facial motion. Context and stimulus configuration likely plays a role in shaping neural responses, based on comparisons of the current data to previously reported studies. Broadband suppression of central beta activity, and significant low frequency differences were likely stimulus driven and not contingent on behavioral responses.
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http://dx.doi.org/10.1016/j.neuroimage.2014.04.029DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4106672PMC
September 2014

Reducing respiratory effect in motion correction for EPI images with sequential slice acquisition order.

Authors:
Hu Cheng Aina Puce

J Neurosci Methods 2014 Apr 19;227:83-9. Epub 2014 Feb 19.

Imaging Research Facility, Indiana University, Bloomington, IN, United States; Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, United States.

Motion correction is critical for data analysis of fMRI time series. Most motion correction algorithms treat the head as a rigid body. Respiration of the subject, however, can alter the static magnetic field in the head and result in motion-like slice shifts for echo planar imaging (EPI). The delay of acquisition between slices causes a phase difference in respiration so that the shifts vary with slice positions. To characterize the effect of respiration on motion correction, we acquired fast sampled fMRI data using multi-band EPI and then simulated different acquisition schemes. Our results indicated that respiration introduces additional noise after motion correction. The signal variation between volumes after motion correction increases when the effective TR increases from 675ms to 2025ms. This problem can be corrected if slices are acquired sequentially. For EPI with a sequential acquisition scheme, we propose to divide the image volumes into several segments so that slices within each segment are acquired close in time and then perform motion correction on these segments separately. We demonstrated that the temporal signal-to-noise ratio (TSNR) was increased when the motion correction was performed on the segments separately rather than on the whole image. This enhancement of TSNR was not evenly distributed across the segments and was not observed for interleaved acquisition. The level of increase was higher for superior slices. On superior slices the percentage of TSNR gain was comparable to that using image based retrospective correction for respiratory noise. Our results suggest that separate motion correction on segments is highly recommended for sequential acquisition schemes, at least for slices distal to the chest.
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http://dx.doi.org/10.1016/j.jneumeth.2014.02.007DOI Listing
April 2014

Multiple faces elicit augmented neural activity.

Front Hum Neurosci 2013 14;7:282. Epub 2013 Jun 14.

Department of Radiology, Center for Advanced Imaging, School of Medicine, West Virginia University Morgantown, WV, USA ; Department of Radiology, School of Medicine, West Virginia University Morgantown, WV, USA ; Department of Neurobiology and Anatomy, School of Medicine, West Virginia University Morgantown, WV, USA ; Department of Psychological and Brain Sciences, Indiana University Bloomington, IN, USA.

How do our brains respond when we are being watched by a group of people?Despite the large volume of literature devoted to face processing, this question has received very little attention. Here we measured the effects on the face-sensitive N170 and other ERPs to viewing displays of one, two and three faces in two experiments. In Experiment 1, overall image brightness and contrast were adjusted to be constant, whereas in Experiment 2 local contrast and brightness of individual faces were not manipulated. A robust positive-negative-positive (P100-N170-P250) ERP complex and an additional late positive ERP, the P400, were elicited to all stimulus types. As the number of faces in the display increased, N170 amplitude increased for both stimulus sets, and latency increased in Experiment 2. P100 latency and P250 amplitude were affected by changes in overall brightness and contrast, but not by the number of faces in the display per se. In Experiment 1 when overall brightness and contrast were adjusted to be constant, later ERP (P250 and P400) latencies showed differences as a function of hemisphere. Hence, our data indicate that N170 increases its magnitude when multiple faces are seen, apparently impervious to basic low-level stimulus features including stimulus size. Outstanding questions remain regarding category-sensitive neural activity that is elicited to viewing multiple items of stimulus categories other than faces.
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http://dx.doi.org/10.3389/fnhum.2013.00282DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3682123PMC
June 2013

Sustained neural activity to gaze and emotion perception in dynamic social scenes.

Soc Cogn Affect Neurosci 2014 Mar 30;9(3):350-7. Epub 2012 Nov 30.

Cogimage group, CRICM, UMR 7225/UMR-S 975, UPMC/CNRS/INSERM, ICM building, GHU Pitié-Salpêtrière, 47 bd de l'Hôpital, 75013 Paris, France. Tel: +33 1 57 27 41 79;

To understand social interactions, we must decode dynamic social cues from seen faces. Here, we used magnetoencephalography (MEG) to study the neural responses underlying the perception of emotional expressions and gaze direction changes as depicted in an interaction between two agents. Subjects viewed displays of paired faces that first established a social scenario of gazing at each other (mutual attention) or gazing laterally together (deviated group attention) and then dynamically displayed either an angry or happy facial expression. The initial gaze change elicited a significantly larger M170 under the deviated than the mutual attention scenario. At around 400 ms after the dynamic emotion onset, responses at posterior MEG sensors differentiated between emotions, and between 1000 and 2200 ms, left posterior sensors were additionally modulated by social scenario. Moreover, activity on right anterior sensors showed both an early and prolonged interaction between emotion and social scenario. These results suggest that activity in right anterior sensors reflects an early integration of emotion and social attention, while posterior activity first differentiated between emotions only, supporting the view of a dual route for emotion processing. Altogether, our data demonstrate that both transient and sustained neurophysiological responses underlie social processing when observing interactions between others.
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http://dx.doi.org/10.1093/scan/nss141DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3980798PMC
March 2014

Structural network topology revealed by white matter tractography in cannabis users: a graph theoretical analysis.

Brain Connect 2011 24;1(6):473-83. Epub 2012 Feb 24.

Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana 47405, USA.

Endocannabinoid receptors modulate synaptic plasticity in the brain and may therefore impact cortical connectivity not only during development but also in response to substance abuse in later life. Such alterations may not be evident in volumetric measures utilized in brain imaging, but could affect the local and global organization of brain networks. To test this hypothesis, we used a novel computational approach to estimate network measures of structural brain connectivity derived from diffusion tensor imaging (DTI) and white matter tractography. Twelve adult cannabis (CB) users and 13 healthy subjects were evaluated using a graph theoretic analysis of both global and local brain network properties. Structural brain networks in both CB subjects and controls exhibited robust small-world network attributes in both groups. However, CB subjects showed significantly decreased global network efficiency and significantly increased clustering coefficients (degree to which nodes tend to cluster around individual nodes). CB subjects also exhibited altered patterns of local network organization in the cingulate region. Among all subjects, schizotypal and impulsive personality characteristics correlated with global efficiency but not with the clustering coefficient. Our data indicate that structural brain networks in CB subjects are less efficiently integrated and exhibit altered regional connectivity. These differences in network properties may reflect physiological processes secondary to substance abuse-induced synaptic plasticity, or differences in brain organization that increase vulnerability to substance use.
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http://dx.doi.org/10.1089/brain.2011.0053DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3604771PMC
January 2013

Inverse effectiveness and multisensory interactions in visual event-related potentials with audiovisual speech.

Brain Topogr 2012 Jul 25;25(3):308-26. Epub 2012 Feb 25.

Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, USA.

In recent years, it has become evident that neural responses previously considered to be unisensory can be modulated by sensory input from other modalities. In this regard, visual neural activity elicited to viewing a face is strongly influenced by concurrent incoming auditory information, particularly speech. Here, we applied an additive-factors paradigm aimed at quantifying the impact that auditory speech has on visual event-related potentials (ERPs) elicited to visual speech. These multisensory interactions were measured across parametrically varied stimulus salience, quantified in terms of signal to noise, to provide novel insights into the neural mechanisms of audiovisual speech perception. First, we measured a monotonic increase of the amplitude of the visual P1-N1-P2 ERP complex during a spoken-word recognition task with increases in stimulus salience. ERP component amplitudes varied directly with stimulus salience for visual, audiovisual, and summed unisensory recordings. Second, we measured changes in multisensory gain across salience levels. During audiovisual speech, the P1 and P1-N1 components exhibited less multisensory gain relative to the summed unisensory components with reduced salience, while N1-P2 amplitude exhibited greater multisensory gain as salience was reduced, consistent with the principle of inverse effectiveness. The amplitude interactions were correlated with behavioral measures of multisensory gain across salience levels as measured by response times, suggesting that change in multisensory gain associated with unisensory salience modulations reflects an increased efficiency of visual speech processing.
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http://dx.doi.org/10.1007/s10548-012-0220-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3789520PMC
July 2012

In the blink of an eye: neural responses elicited to viewing the eye blinks of another individual.

Front Hum Neurosci 2011 5;5:68. Epub 2011 Aug 5.

Center for Advanced Imaging, West Virginia University Morgantown, WV, USA.

Facial movements have the potential to be powerful social signals. Previous studies have shown that eye gaze changes and simple mouth movements can elicit robust neural responses, which can be altered as a function of potential social significance. Eye blinks are frequent events and are usually not deliberately communicative, yet blink rate is known to influence social perception. Here, we studied event-related potentials (ERPs) elicited to observing non-task relevant blinks, eye closure, and eye gaze changes in a centrally presented natural face stimulus. Our first hypothesis (H1) that blinks would produce robust ERPs (N170 and later ERP components) was validated, suggesting that the brain may register and process all types of eye movement for potential social relevance. We also predicted an amplitude gradient for ERPs as a function of gaze change, relative to eye closure and then blinks (H2). H2 was only partly validated: large temporo-occipital N170s to all eye change conditions were observed and did not significantly differ between blinks and other conditions. However, blinks elicited late ERPs that, although robust, were significantly smaller relative to gaze conditions. Our data indicate that small and task-irrelevant facial movements such as blinks are measurably registered by the observer's brain. This finding is suggestive of the potential social significance of blinks which, in turn, has implications for the study of social cognition and use of real-life social scenarios.
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http://dx.doi.org/10.3389/fnhum.2011.00068DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3151614PMC
November 2011

Action expertise reduces brain activity for audiovisual matching actions: an fMRI study with expert drummers.

Neuroimage 2011 Jun 21;56(3):1480-92. Epub 2011 Mar 21.

Department of Psychology, University of Glasgow, Glasgow, Scotland, UK.

When we observe someone perform a familiar action, we can usually predict what kind of sound that action will produce. Musical actions are over-experienced by musicians and not by non-musicians, and thus offer a unique way to examine how action expertise affects brain processes when the predictability of the produced sound is manipulated. We used functional magnetic resonance imaging to scan 11 drummers and 11 age- and gender-matched novices who made judgments on point-light drumming movements presented with sound. In Experiment 1, sound was synchronized or desynchronized with drumming strikes, while in Experiment 2 sound was always synchronized, but the natural covariation between sound intensity and velocity of the drumming strike was maintained or eliminated. Prior to MRI scanning, each participant completed psychophysical testing to identify personal levels of synchronous and asynchronous timing to be used in the two fMRI activation tasks. In both experiments, the drummers' brain activation was reduced in motor and action representation brain regions when sound matched the observed movements, and was similar to that of novices when sound was mismatched. This reduction in neural activity occurred bilaterally in the cerebellum and left parahippocampal gyrus in Experiment 1, and in the right inferior parietal lobule, inferior temporal gyrus, middle frontal gyrus and precentral gyrus in Experiment 2. Our results indicate that brain functions in action-sound representation areas are modulated by multimodal action expertise.
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http://dx.doi.org/10.1016/j.neuroimage.2011.03.009DOI Listing
June 2011

Relationship between touch impairment and brain activation after lesions of subcortical and cortical somatosensory regions.

Neurorehabil Neural Repair 2011 Jun 7;25(5):443-57. Epub 2011 Mar 7.

National Stroke Research Institute, Florey Neuroscience Institutes, Melbourne, Victoria, Australia.

Background: The neural basis underlying somatosensory impairment and recovery poststroke is virtually unexplored.

Objective: To investigate the relationship between touch discrimination impairment and task-related brain activation in stroke survivors with somatosensory impairment following subcortical or cortical lesions.

Methods: A total of 19 stroke survivors with touch impairment were investigated using fMRI and a touch discrimination paradigm 1-month poststroke; 11 had subcortical and 8 cortical sensory lesions; 12 age-matched healthy controls were also studied. Mean task-related contrast images were regressed with sensory impairment using random effects analysis for each subgroup and the total group.

Results: There was no significant difference in touch impairment between stroke subgroups. Touch discrimination of the affected hand correlated negatively with task-related activation in the ipsilesional primary somatosensory cortex (SI; adjacent to the SI hand area activated in healthy controls); ipsilesional secondary somatosensory cortex (SII); contralesional thalamus; and attention-related frontal and occipital regions in the subcortical group. In contrast, the cortical group did not show significant correlated activity. Yet there was no significant between-group difference in a priori somatosensory regions: only in the superior medial frontal gyrus. A negative correlation was observed in the contralesional thalamus for the total group, irrespective of lesion type.

Conclusion: The findings provide novel evidence of neural correlates of poststroke touch impairment involving a distributed network of ipsilesional SI and SII, the contralesional thalamus, and frontal attention regions, particularly following subcortical lesions. Further systematic investigation of a modulatory role for ipsilesional SI, the thalamus, and frontal attention regions in sensory processing and recovery is warranted, particularly given implications for rehabilitation.
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http://dx.doi.org/10.1177/1545968310395777DOI Listing
June 2011
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