Aina Puce Research Collection

Permanent link for this collectionhttps://hdl.handle.net/2022/22726

My research interests lie in the brain basis of social interaction – with a focus on non-verbal communication. In my Social Neuroscience Lab we study how information that is perceived consciously or unconsciously leads us to make decisions about the intentions, goals, emotions and mental states of others. My research involves the integrated use of functional and structural magnetic resonance imaging (MRI), infrared eye tracking, high-density electroencephalography (EEG) and transcranial magnetic stimulation (TMS) to understand brain function in human subjects. I have a long-standing collaboration with colleagues who use magnetoencephalography (MEG). By investigating structural and functional connectivity patterns in the brain as subjects engage in evaluating the social behaviors of others, we can begin to develop insights into how the human brain processes incoming the dynamic and fleeting social information in our environment.

Science is important but must be based on a solid scaffold of reliable scientific method. To that end, I have co-written a textbook on methods [Riitta Hari & Aina Puce (2017); MEG-EEG Primer, New York, Oxford University Press]. We have revised it and the 2nd edition is currently in press (2022). I am also very active in international efforts devoted to encouraging and developing best practices in neurophysiology and neuroimaging, as well as open science and data sharing.

Browse

Recent Submissions

Now showing 1 - 20 of 36
  • Item
    Good scientific practice in EEG and MEG research: Progress and perspectives
    (NeuroImage, 2022) Niso, Guiomar; Krol, Laurens R.; Combrisson, Etienne; Dubarry, A. Sophie; Elliott, Madison A.; François, Clément; Héjja-Brichard, Yseult; Herbst, Sophie K.; Jerbi, Karim; Kovic, Vanja; Lehongre, Katia; Luck, Steven J.; Mercier, Manuel; Mosher, John C.; Pavlov, Yuri G.; Puce, Aina; Schettino, Antonio; Schön, Daniele; Sinnott-Armstrong, Walter; Somon, Bertille; Šoškić, Anđela; Styles, Suzy J.; Tibon, Roni; Vilas, Martina G.; van Vliet, Marijn; Chaumon, Maximilien
    Good scientific practice (GSP) refers to both explicit and implicit rules, recommendations, and guidelines that help scientists to produce work that is of the highest quality at any given time, and to efficiently share that work with the community for further scrutiny or utilization. For experimental research using magneto- and electroencephalography (MEEG), GSP includes specific standards and guidelines for technical competence, which are periodically updated and adapted to new findings. However, GSP also needs to be regularly revisited in a broader light. At the LiveMEEG 2020 conference, a reflection on GSP was fostered that included explicitly documented guidelines and technical advances, but also emphasized intangible GSP: a general awareness of personal, organizational, and societal realities and how they can influence MEEG research. This article provides an extensive report on most of the LiveMEEG contributions and new literature, with the additional aim to synthesize ongoing cultural changes in GSP. It first covers GSP with respect to cognitive biases and logical fallacies, pre-registration as a tool to avoid those and other early pitfalls, and a number of resources to enable collaborative and reproducible research as a general approach to minimize misconceptions. Second, it covers GSP with respect to data acquisition, analysis, reporting, and sharing, including new tools and frameworks to support collaborative work. Finally, GSP is considered in light of ethical implications of MEEG research and the resulting responsibility that scientists have to engage with societal challenges. Considering among other things the benefits of peer review and open access at all stages, the need to coordinate larger international projects, the complexity of MEEG subject matter, and today's prioritization of fairness, privacy, and the environment, we find that current GSP tends to favor collective and cooperative work, for both scientific and for societal reasons.
  • Item
    Visual Information Routes in the Posterior Dorsal and Ventral Face Network Studied with Intracranial Neurophysiology and White Matter Tract Endpoints
    (Cerebral Cortex, 2022) Babo-Rebelo, Mariana; Puce, Aina; Bullock, D; Hugueville, Laurent; Pestilli, Franco; Adam, C.; Lehongre, Katia; Lambrecq, Virginie; Dinkelacker, Vera; George, Nathalie
    Occipitotemporal regions within the face network process perceptual and socioemotional information, but the dynamics and information flow between different nodes of this network are still debated. Here, we analyzed intracerebral EEG from 11 epileptic patients viewing a stimulus sequence beginning with a neutral face with direct gaze. The gaze could avert or remain direct, while the emotion changed to fearful or happy. N200 field potential peak latencies indicated that face processing begins in inferior occipital cortex and proceeds anteroventrally to fusiform and inferior temporal cortices, in parallel. The superior temporal sulcus responded preferentially to gaze changes with augmented field potential amplitudes for averted versus direct gaze, and large effect sizes relative to other network regions. An overlap analysis of posterior white matter tractography endpoints (from 1066 healthy brains) relative to active intracerebral electrodes in the 11 patients showed likely involvement of both dorsal and ventral posterior white matter pathways. Overall, our data provide new insight into the timing of face and social cue processing in the occipitotemporal brain and anchor the superior temporal cortex in dynamic gaze processing.
  • Item
    Statistical power: implications for planning MEG studies
    (NeuroImage, 2021) Chaumon, Maximilien; Puce, Aina; George, Nathalie
    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.
  • Item
    Differential effects of propofol and ketamine on critical brain dynamics
    (PLOS Computational Biology, 2020) Farley, Thomas F.; Sporns, Olaf; Puce, Aina; Beggs, John
    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.
  • Item
    Best practices in data analysis and sharing in neuroimaging using MEEG
    (OSF Preprints, 2018) Pernet, Cyril; Garrido, Marta; Gramfort, Alexandre; Maurits, Natasha; Michel, Christoph M.; Pang, Elizabeth; Salmelin, Riitta; Schoffelen, Jan Mathijis; Valdes-Sosa, Pedro A.; Puce, Aina
    Non-invasive neuroimaging methods, including magnetoencephalography and electroencephalography (MEEG), have been critical in advancing the understanding of brain function in healthy people and in individuals with neurological or psychiatric disorders. Currently, scientific practice is undergoing a tremendous change, aiming to improve both research reproducibility and transparency in data collection, documentation and analysis, and in manuscript review. To advance the practice of open science, the Organization for Human Brain Mapping created the Committee on Best Practice in Data Analysis and Sharing (COBIDAS), which produced a report for MRI-based data in 2016. This effort continues with the OHBM’s COBIDAS MEEG committee whose task was to create a similar document that describes best practice recommendations for MEEG data. The document was drafted by OHBM experts in MEEG, with input from the world-wide brain imaging community, including OHBM members who volunteered to help with this effort, as well as Executive Committee members of the International Federation for Clinical Neurophysiology. This document outlines the principles of performing open and reproducible research in MEEG. Not all MEEG data practices are described in this document. Instead, we propose principles that we believe are current best practice for most recordings and common analyses. Furthermore, we suggest reporting guidelines for Authors that will enable others in the field to fully understand and potentially replicate any study. This document should be helpful to Authors, Reviewers of manuscripts, as well as Editors of neuroscience journals.
  • Item
    A Review of Issues Related to Data Acquisition andAnalysis in EEG/MEG Studies
    (Brain Sciences, 2017-05-31) Puce, Aina; Hämäläinen, Matti S.
    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.
  • Item
    Advances in human intracranial electroencephalography research, guidelines and good practices
    (NeuroImage, 2022-10) Mercier, Manuel R.; Dubarry, Anne-Sophie; Tadel, François; Avanzini, Pietro; Axmacher, Nikolai; Cellier, Dillan; Del Vecchio, Maria; Hamilton, Liberty S.; Hermes, Dora; Kahana, Michael J.; Knight, Robert T.; Llorens, Anais; Megevand, Pierre; Melloni, Lucia; Miller, Kai J.; Piai, Vitória; Puce, Aina; Ramsey, Nick F; Schwiedrzik, Caspar M.; Smith, Sydney E.; Stolk, Arjen; Swann, Nicole C.; Vansteensel, Mariska J; Voytek, Bradley; Wang, Liang; Lachaux, Jean-Philippe; Oostenveld, Robert
    Since the second-half of the twentieth century, intracranial electroencephalography (iEEG), including both electrocorticography (ECoG) and stereo-electroencephalography (sEEG), has provided an intimate view into the human brain. At the interface between fundamental research and the clinic, iEEG provides both high temporal resolution and high spatial specificity but comes with constraints, such as the individual’s tailored sparsity of electrode sampling. Over the years, researchers in neuroscience developed their practices to make the most of the iEEG approach. Here we offer a critical review of iEEG research practices in a didactic framework for newcomers, as well addressing issues encountered by proficient researchers.The scope is threefold: (i) review common practices in iEEG research, (ii) suggest potential guidelines for working with iEEG data and answer frequently asked questions based on the most widespread practices, and (iii) based on current neurophysiological knowledge and methodologies, pave the way to good practice standards in iEEG research. The organization of this paper follows the steps of iEEG data processing. The first section contextualizes iEEG data collection. The second section focuses on localization of intracranial electrodes. The third section highlights the main pre-processing steps. The fourth section presents iEEG signal analysis methods. The fifth section discusses statistical approaches.The sixth section draws some unique perspectives on iEEG research. Finally, to ensure a consistent nomenclature throughout the manuscript and to align with other guidelines, e.g., Brain Imaging Data Structure (BIDS) and the OHBM Committee on Best Practices in Data Analysis and Sharing (COBIDAS), we provide a glossary to disambiguate terms related to iEEG research.
  • Item
    IFCN-endorsed practical guidelines for clinical magnetoencephalography (MEG)
    (Clinical Neurophysiology, 2018-08) Hari, Riitta; Baillet, Sylvain; Barnes, Gareth; Burgess, Richard; Forss, Nina; Gross, Joachim; Hämäläinen, Matti; Jensen, Ole; Kakigi, Ryusuke; Mauguière, François; Nakasato, Nobukatzu; Puce, Aina; Romani, Gian-Luca; Schnitzler, Alfons; Taulu, Samu
    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.
  • Item
    Socio-emotionally Significant Experience and Children’s Processing of Irrelevant Auditory Stimuli
    (International Journal of Psychophysiology, 2016-12) Schermerhorn, Alice C.; Bates, John E.; Puce, Aina; Molfese, Dennis L.
    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.
  • Item
    Nodal centrality of functional network in the differentiation of schizophrenia
    (Schizophrenia Research, 2015-08) Cheng, Hu; Newman, Sharlene; Goñi, Joaquín; Kent, Jerillyn S.; Howell, Josselyn; Bolbecker, Amanda; Puce, Aina; O’Donnell, Brian F.; Hetrick, William P.
    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.
  • Item
    White matter abnormalities of microstructure and physiological noise in schizophrenia
    (Brain Imaging and Behavior, 2015-01) Cheng, Hu; Newman, Sharlene D.; Kent, Jerillyn S.; Bolbecker, Amanda; Klaunig, Mallory J.; O'Donnell, Brian F.; Puce, Aina; Hetrick, William P.
    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.
  • Item
    Disrupted Modular Architecture of Cerebellum in Schizophrenia: A Graph Theoretic Analysis
    (Schizophrenia Bulletin, 2014-04) Kim, Dae-Jin; Kent, Jerillyn S.; Bolbecker, Amanda R.; Sporns, Olaf; Cheng, Hu; Newman, Sharlene D.; Puce, Aina; O’Donnell, Brian F.; Hetrick, William P.
    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.
  • Item
    Neural correlates of apparent motion perception of impoverished facial stimuli: A comparison of ERP and ERSP activity
    (NeuroImage, 2014-04) Rossi, Alejandra; Parada, Francisco J.; Kolchinsky, Artemy; Puce, Aina
    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 occipitotemporal 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 occipitotemporal 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 250 ms post-motion onset. In the right cluster, beta suppression was seen for control conditions only. Statistically significant differences between conditions were confined between 4 – 15 Hz, unlike occipitotemporal 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, occipitotemporal beta and gamma activity differentiate between facial and non-facial motion. Context and stimulus configuration likely play 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.
  • Item
    Audiovisual Non-Verbal Dynamic Faces Elicit Converging fMRI and ERP Responses
    (Brain Topography, 2009-04) Brefczynski-Lewis, Julie; Lowitszch, Svenja; Parsons, Michael
    In an everyday social interaction we automatically integrate another’s facial movements and vocalizations, be they linguistic or otherwise. This requires audiovisual integration of a continual barrage of sensory input—a phenomenon previously well-studied with human audiovisual speech, but not with non-verbal vocalizations. Using both fMRI and ERPs, we assessed neural activity to viewing and listening to an animated female face producing non-verbal, human vocalizations (i.e. coughing, sneezing) under audio-only (AUD), visual-only (VIS) and audiovisual (AV) stimulus conditions, alternating with Rest (R). Underadditive effects occurred in regions dominant for sensory processing, which showed AV activation greater than the dominant modality alone. Right posterior temporal and parietal regions showed an AV maximum in which AV activation was greater than either modality alone, but not greater than the sum of the unisensory conditions. Other frontal and parietal regions showed Common-activation in which AV activation was the same as one or both unisensory conditions. ERP data showed an early superadditive effect (AV > AUD + VIS, no rest), mid-range underadditive effects for auditory N140 and face-sensitive N170, and late AV maximum and common-activation effects. Based on convergence between fMRI and ERP data, we propose a mechanism where a multisensory stimulus may be signaled or facilitated as early as 60 ms and facilitated in sensory-specific regions by increasing processing speed (at N170) and efficiency (decreasing amplitude in auditory and face-sensitive cortical activation and ERPs). Finally, higher-order processes are also altered, but in a more complex fashion.
  • Item
    Electrophysiology and brain imaging of biological motion
    (Philosophical Transactions B, 2003-02) Puce, Aina; Perrett, David
    The movements of the faces and bodies of other conspecifics provide stimuli of considerable interest to the social primate. Studies of single cells, field potential recordings and functional neuroimaging data indicate that specialized visual mechanisms exist in the superior temporal sulcus (STS) of both human and non-human primates that produce selective neural responses to moving natural images of faces and bodies. STS mechanisms also process simplified displays of biological motion involving point lights marking the limb articulations of animate bodies and geometrical shapes whose motion simulates purposeful behaviour. Facial movements such as deviations in eye gaze, important for gauging an individual's social attention, and mouth movements, indicative of potential utterances, generate particularly robust neural responses that differentiate between movement types. Collectively such visual processing can enable the decoding of complex social signals and through its outputs to limbic, frontal and parietal systems the STS may play a part in enabling appropriate affective responses and social behaviour.
  • Item
    Structural Network Topology Revealed by White Matter Tractography in Cannabis Users: A Graph Theoretical Analysis
    (2011-12) Kim, Dae-Jin; Skosnik, Patrick D.; Cheng, Hu; Pruce, Ben J.; Brumbaugh, Margaret S.; Vollmer, Jennifer M.; Hetrick, William P.; O'Donnell, Brian F.; Sporns, Olaf; Puce, Aina; Newman, Sharlene D.
    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.
  • Item
    Inverse Effectiveness and Multisensory Interactions in Visual Event-Related Potentials with Audiovisual Speech
    (Brain Topography, 2012-02) Stevenson, Ryan A.; Bushmakin, Maxim; Kim, Sunah; Wallace, Mark T.; Puce, Aina; James, Thomas W.
    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.
  • Item
    Neuronal oscillations and visual amplification of speech
    (Trends in Cognitive Sciences, 2008-02) Schroeder, Charles E.; Lakatos, Peter; Kajikawa, Yoshinao; Partan, Sarah; Puce, Aina
    It is widely recognized that viewing a speaker’s face enhances vocal communication, although the neural substrates of this phenomenon remain unknown. We propose that the enhancement effect uses the ongoing oscillatory activity of local neuronal ensembles in the primary auditory cortex. Neuronal oscillations reflect rhythmic shifting of neuronal ensembles between high and low excitability states. Our hypothesis holds that oscillations are ‘predictively’ modulated by visual input, so that related auditory input arrives during a high excitability phase and is thus amplified. We discuss the anatomical substrates and key timing parameters that enable and constrain this effect. Our hypothesis makes testable predictions for future studies and emphasizes the idea that ‘background’ oscillatory activity is instrumental to cortical sensory processing.
  • Item
    It's all in the eyes: neural responses to socially significant gaze shifts
    (NeuroReport, 2009-12) Carrick, Olivia K.; Thompson, James C.; Epling, James A.; Puce, Aina
    Gaze direction signals another's focus of social attention. Here, we recorded event-related potentials to a multiface display where a gaze aversion created three different social scenarios involving social attention, mutual gaze exchange, and gaze avoidance. N170 was unaffected by social scenario. P350 latency was the shortest in social attention and mutual gaze exchange, whereas P500 was thelargest for gaze avoidance. Our data suggest that neural activity after 300 ms poststimulus may index processes associated with extracting social meaning, whereas that earlier than 300 ms may index processing of gaze change independent of social context.
  • Item
    Neural responses elicited to face motion and vocalization pairings
    (Neuropsychologia, 2007-01) Puce, Aina; Epling, James A.; Thompson, James C.; Carrick, Olivia K.
    During social interactions our brains continuously integrate incoming auditory and visual input from the movements and vocalizations of others. Yet, the dynamics of the neural events elicited to these multisensory stimuli remain largely uncharacterized. Here we recorded audiovisual scalp event-related potentials (ERPs) to dynamic human faces with associated human vocalizations. Audiovisual controls were a dynamic monkey face with a species-appropriate vocalization, and a house with opening front door with a creaking door sound. Subjects decided if audiovisual stimulus trials were congruent (e.g. human face–human sound) or incongruent (e.g. house image–monkey sound). An early auditory ERP component, N140, was largest to human and monkey vocalizations. This effect was strongest in the presence of the dynamic human face, suggesting that species-specific visual information can modulate auditory ERP characteristics. A motion-induced visual N170 did not change amplitude or latency across visual motion category in the presence of sound. A species-specific incongruity response consisting of a late positive ERP at around 400 ms, P400, was selectively larger only when human faces were mismatched with a non-human sound. We also recorded visual ERPs at trial onset, and found that the category-specific N170 did not alter its behavior as a function of stimulus category—somewhat unexpected as two face types were contrasted with a house image. In conclusion, we present evidence for species-specificity in vocalization selectivity in early ERPs, and in a multisensory incongruity response whose amplitude is modulated only when the human face motion is paired with an incongruous auditory stimulus.