Time Course Of Stimulus Research Articles

Evoked Component Analysis (ECA): Decomposing the Functional Ultrasound Signal With GLM-Regularization.

Analysis of functional neuroimaging data aims to unveil spatial and temporal patterns of interest. Existing analysis methods fall into two categories: fully data-driven approaches and those reliant on prior information, e.g. the stimulus time course. While using the stimulus signal directly can help identify the activated brain areas, it is known that the relationship between stimuli and the brain's response exhibits nonlinear and time-varying characteristics. As such, relying completely on the stimulus signal to describe the brain's temporal response leads to a restricted interpretation of the brain function. In this paper, we present a new technique called Evoked Component Analysis (ECA), which leverages prior information up to a defined extent. This is achieved by including the general linear model (GLM) design matrix as a regulatory term and estimating the factor matrices in both space and time through an alternating minimization approach. We apply ECA to 2D and swept-3D functional ultrasound (fUS) experiments conducted with mice. When decomposing 2D fUS data, we employ GLM regularization at various intensities to emphasize the role of prior information. Furthermore, we show that incorporating multiple hemodynamic response functions within the design matrix can provide valuable insights into region-specific characteristics of evoked activity. Finally, we use ECA to analyze swept-3D fUS data recorded from five mice engaged in two distinct visual tasks. Swept-3D fUS images the 3D brain sequentially using a moving probe, resulting in different slice acquisition time instants. We show that ECA can estimate factor matrices with a fine resolution at each slice acquisition time instant and yield higher t-statistics compared to GLM and correlation analysis for all subjects.

Systematic Review and Meta-Analysis: Eye-Tracking of Attention to Threat in Child and Adolescent Anxiety.

Attention biases for threat may reflect an early risk marker for anxiety disorders. Yet questions remain regarding the direction and time-course of anxiety-linked biased attention patterns in youth. A meta-analysis of eye-tracking studies of biased attention for threat was used to compare the presence of an initial vigilance toward threat and a subsequent avoidance in anxious and nonanxious youths. PubMed, PsycARTICLES, Medline, PsychINFO, and Embase were searched using anxiety, children and adolescent, and eye-tracking-related key terms. Study inclusion criteria were as follows: studies including participants≤18 years of age; reported anxiety using standardized measures; measured attention bias using eye tracking with a free-viewing task; comparison of attention toward threatening and neutral stimuli; and available data to allow effect size computation for at least one relevant measure. A random effects model estimated between- and within-group effects of first fixations toward threat and overall dwell time on threat. Thirteen eligible studies involving 798 participants showed that neither youths with or without anxiety showed significant bias in first fixation to threat versus neutral stimuli. However anxious youths showed significantly less overall dwell time on threat versus neutral stimuli than nonanxious controls (g= -0.26). Contrasting with adult eye-tracking data and child and adolescent data from reaction time indices of attention biases to threat, there was no vigilance bias toward threat in anxious youths. Instead, anxious youths were more avoidant of threat across the time course of stimulus viewing. Developmental differences in brain circuits contributing to attention deployment to emotional stimuli and their relationship with anxiety are discussed.

A central mechanism enhances pain perception of noxious thermal stimulus changes

Pain perception temporarily exaggerates abrupt thermal stimulus changes revealing a mechanism for nociceptive temporal contrast enhancement (TCE). Although the mechanism is unknown, a non-linear model with perceptual feedback accurately simulates the phenomenon. Here we test if a mechanism in the central nervous system underlies thermal TCE. Our model successfully predicted an optimal stimulus, incorporating a transient temperature offset (step-up/step-down), with maximal TCE, resulting in psychophysically verified large decrements in pain response (“offset-analgesia”; mean analgesia: 85%, n = 20 subjects). Next, this stimulus was delivered using two thermodes, one delivering the longer duration baseline temperature pulse and the other superimposing a short higher temperature pulse. The two stimuli were applied simultaneously either near or far on the same arm, or on opposite arms. Spatial separation across multiple peripheral receptive fields ensures the composite stimulus timecourse is first reconstituted in the central nervous system. Following ipsilateral stimulus cessation on the high temperature thermode, but before cessation of the low temperature stimulus properties of TCE were observed both for individual subjects and in group-mean responses. This demonstrates a central integration mechanism is sufficient to evoke painful thermal TCE, an essential step in transforming transient afferent nociceptive signals into a stable pain perception.

Analysis of Neural-BOLD Coupling Through Four Models of the Neural Metabolic Demand

The coupling of the neuronal energetics to the blood-oxygen-level-dependent (BOLD) response is still incompletely understood. To address this issue, we compared the fits of four plausible models of neurometabolic coupling dynamics to available data for simultaneous recordings of the local field potential and the local BOLD response recorded from monkey primary visual cortex over a wide range of stimulus durations. The four models of the metabolic demand driving the BOLD response were: direct coupling with the overall LFP; rectified coupling to the LFP; coupling with a slow adaptive component of the implied neural population response; and coupling with the non-adaptive intracellular input signal defined by the stimulus time course. Taking all stimulus durations into account, the results imply that the BOLD response is most closely coupled with metabolic demand derived from the intracellular input waveform, without significant influence from the adaptive transients and nonlinearities exhibited by the LFP waveform.

Expression regulation of co-inhibitory molecules on human natural killer cells in response to cytokine stimulations

Co-inhibitory molecules have become the key targets in cancer immunotherapy with the strategy of blocking immune checkpoints to reverse the pathogenic regulation of T cells. However, their expression regulations in NK cells, the most important innate immune cells against tumor, remain largely undefined. In this study, we showed that the expressions of co-inhibitors on NK cells, including LAG-3, PD-1, and TIGIT, are differently regulated by cytokines IL-10, IL-12, IL-15, IFN-α, and TGF-β. Among the tested cytokines, IL-12 is the most powerful inducer of LAG-3, and TGF-β is the strongest suppresser of PD-1. Notably, the expression of these co-inhibitors responds to the time course of stimulus progressively. Together, these findings illustrated that the co-inhibitors on NK cells express differently in response to cytokine stimulations of IL-10, IL-12, IL-15, IFN-α, and TGF-β, providing an initial information on the expression regulation of co-inhibitors in human NK cells.

Trying hard not to listen: the evolution of information processing in vestibular hair cells

Vestibular afferents encode head movements with a discharge that follows stimulus timecourse. In aquatic animals, both vestibular and auditory stimuli are carried by water, and mainly differ in spectral power content. For land animals, sounds are carried by air vibration that minimally affect head movements, so that auditory and vestibular organs receive separate inputs. It is therefore no surprise that auditory and vestibular hair cells are much more similar in fish than in tetrapods. In this work we compare the two different strategies for encoding vestibular signals by hair cells in lower and higher vertebrates, and suggest a possible pathway for the evolution of the vestibular organs (by modeling the electrical membrane changes necessary and sufficient to transform one encoding strategy into the other). Amphibia represent a primitive transition to land life, and their inner ear is primitive in many ways, containing organs, such as the saccule, which cannot be classified as purely auditory nor vestibular. However, it also displays proper vestibular organs, namely an utricle, a lagena and three semicircular canals. For each vestibular organ, afferents display variations in gain, dynamics, resting discharge frequency and regularity which are similar to those in higher vertebrates, in particular a low-gain, phasic population is observed, similar to fibers innervating type-I hair cells in amniotes. On the other hand, hair cells still show primitive features, namely the presence, in the population connecting to phasic fibers, of resonant behaviour due to a Ca-BK system, which is absent in higher vertebrates, that instead possess type I hair cells, which display a characteristic large M current which profoundly change their electrophysiological properties. We have investigated the membrane and release properties of frog utricular and semicircular canal hair cells, by recording (with perforated patch-clamp) current, voltage and release from hair cells differing in morphology and epithelial position. Data from these experiments, together with literature data for buffer expression and afferent innervation, and immunohistochemistry data for intracellular Ca sources, were used to build a NEURON model of utricular hair cells reproducing literature data for afferent discharge. Our model show that Ca-BK resonance of phasic hair cells, which is set at higher frequencies than vestibular stimuli, imparts a phase advance to hair cell release relative to the mechanical stimulus, but also introduces other linearity distortions, such as gain compression, which are not present in fibers connecting to type I hair cells. Assuming that during evolution from amphibia to reptiles no intermediate animal could survive without a working vestibular system, we explored (with NEURON models) possible transitions from a resonant, ICa-based cell to a nonresonant, IM-based cell that allowed phasic transduction in all intermediate stages.

Multiple Spike Time Patterns Occur at Bifurcation Points of Membrane Potential Dynamics

The response of a neuron to repeated somatic fluctuating current injections in vitro can elicit a reliable and precisely timed sequence of action potentials. The set of responses obtained across trials can also be interpreted as the response of an ensemble of similar neurons receiving the same input, with the precise spike times representing synchronous volleys that would be effective in driving postsynaptic neurons. To study the reproducibility of the output spike times for different conditions that might occur in vivo, we somatically injected aperiodic current waveforms into cortical neurons in vitro and systematically varied the amplitude and DC offset of the fluctuations. As the amplitude of the fluctuations was increased, reliability increased and the spike times remained stable over a wide range of values. However, at specific values called bifurcation points, large shifts in the spike times were obtained in response to small changes in the stimulus, resulting in multiple spike patterns that were revealed using an unsupervised classification method. Increasing the DC offset, which mimicked an overall increase in network background activity, also revealed bifurcation points and increased the reliability. Furthermore, the spike times shifted earlier with increasing offset. Although the reliability was reduced at bifurcation points, a theoretical analysis showed that the information about the stimulus time course was increased because each of the spike time patterns contained different information about the input.

The influence of visual search efficiency on the time-course of identity-based SR-compatibility

Three experiments were conducted to investigate the impact of stimulus-driven control on the time-course of stimulus–response (SR) compatibility. Participants responded to the presence or absence of a singleton arrow that was presented among multiple nontargets. When the singleton arrow was present, observers pressed a button with their right index finger, when it was absent they pressed with their left-index finger. SR-compatibility depended on the relation between the identity of the target and the present response: Even though the identity of the target singleton arrow (whether it was pointing to the right or left) was irrelevant to the task, the direction could be corresponding (right arrow) or noncorresponding (left arrow) with a target present response (the right hand). To examine the time-course of performance target–distractor similarity was varied to increase or decrease visual search efficiency and accordingly response latency. There were three main findings. First, the results of Experiment 1 showed that observers were no faster to respond ‘present’ when the singleton arrow pointed to the right (corresponding to the right hand) than when it pointed left (noncorresponding to the right hand) in a simple present–absent detection task. Second, only when observers were encouraged to process the identity of the arrow singleton, an effect of an SR-compatibility effect was found which developed over time. Third, the time-course of SR-compatibility was not influenced by visual search efficiency. The results of the present work suggest that visual selection and response selection occur in different stages.

Pharmacologic magnetic resonance imaging (phMRI): Imaging drug action in the brain

The technique of functional magnetic resonance (fMRI), using various cognitive, motor and sensory stimuli has led to a revolution in the ability to map brain function. Drugs can also be used as stimuli to elicit an hemodynamic change. Stimulation with a pharmaceutical has a number of very different consequences compared to user controllable stimuli, most importantly in the time course of stimulus and response that is not, in general, controllable by the experimenter. Therefore, this type of experiment has been termed pharmacologic MRI (phMRI). The use of a drug stimulus leads to a number of interesting possibilities compared to conventional fMRI. Using receptor specific ligands one can characterize brain circuitry specific to neurotransmitter systems. The possibility exists to measure parameters reflecting neurotransmitter release and binding associated with the pharmacokinetics and/or the pharmacodynamics of drugs. There is also the ability to measure up- and down-regulation of receptors in specific disease states. phMRI can be characterized as a molecular imaging technique using the natural hemodynamic transduction related to neuro-receptor stimulus. This provides a coupling mechanism with very high sensitivity that can rival positron emission tomography (PET) in some circumstances. The large numbers of molecules available, that do not require a radio-label, means that phMRI becomes a very useful tool for performing drug discovery. Data and arguments will be presented to show that phMRI can provide information on neuro-receptor signaling and function that complements the static picture generated by PET studies of receptor numbers and occupancies.

Rhythmogram-Based Analysis for Continuous Electrographic Data of the Human Brain

Ecologically relevant stimuli are rarely used in scientific studies because they are difficult to control. Instead, researchers employ simple stimuli with sharp boundaries (in space and time). Here, we explore how the rhythmogram can be used to provide much needed rigorous control of natural continuous stimuli like music and speech. The analysis correlates important features in the time course of stimuli with corresponding features in brain activations elicited by the same stimuli. Correlating the identified regularities of the stimulus time course with the features extracted from the activations of each voxel of a tomographic analysis of brain activity provides a powerful view of how different brain regions are influenced by the stimulus at different times and over different (user-selected) timescales. The application of the analysis to tomographic solutions extracted from magnetoencephalographic data recorded while subjects listen to music reveals a surprising and aesthetically pleasing aspect of brain function: an area believed to be specialized for visual processing is recruited to analyze the music after the acoustic signal is transformed to a feature map. The methodology is ideal for exploring processing of complex stimuli, e.g., linguistic structure and meaning and how it fails, for example, in developmental dyslexia.

Information transmission and detection thresholds in the vestibular nuclei: single neurons vs. population encoding

Understanding how sensory neurons transmit information about relevant stimuli remains a major goal in neuroscience. Of particular relevance are the roles of neural variability and spike timing in neural coding. Peripheral vestibular afferents display differential variability that is correlated with the importance of spike timing; regular afferents display little variability and use a timing code to transmit information about sensory input. Irregular afferents, conversely, display greater variability and instead use a rate code. We studied how central neurons within the vestibular nuclei integrate information from both afferent classes by recording from a group of neurons termed vestibular only (VO) that are known to make contributions to vestibulospinal reflexes and project to higher-order centers. We found that, although individual central neurons had sensitivities that were greater than or equal to those of individual afferents, they transmitted less information. In addition, their velocity detection thresholds were significantly greater than those of individual afferents. This is because VO neurons display greater variability, which is detrimental to information transmission and signal detection. Combining activities from multiple VO neurons increased information transmission. However, the information rates were still much lower than those of equivalent afferent populations. Furthermore, combining responses from multiple VO neurons led to lower velocity detection threshold values approaching those measured from behavior (∼ 2.5 vs. 0.5-1°/s). Our results suggest that the detailed time course of vestibular stimuli encoded by afferents is not transmitted by VO neurons. Instead, they suggest that higher vestibular pathways must integrate information from central vestibular neuron populations to give rise to behaviorally observed detection thresholds.

Dynamics of extraclassical surround modulation in three types of V1 neurons

Visual stimuli outside of the classical receptive field (CRF) can influence the response of neurons in primary visual cortex (V1). While recording single units in cat, we presented drifting sinusoidal gratings in circular apertures of different sizes to investigate this extraclassical surround modulation over time. For the full 2-s stimulus time course, three types of neurons were found: 1) 68% of the cells were "suppressive," 2) 25% were "plateau" cells that showed response saturation with no suppression, and 3) the remaining 6% of cells were "facilitative." Analysis of the response dynamics revealed that at response onset, activity of one-half of facilitative cells, 70% of plateau cells, and all suppressive cells is suppressed by the surround. However, over the next 20-30 ms, surround modulation changes to stronger suppression for suppressive cells, substantial facilitation for facilitative cells, and weak facilitation for plateau cells. For all three cell types, these modulatory effects then stabilize between 100 and 200 ms from stimulus onset. Thus our findings illustrate two stages of surround modulation. Early modulation is mainly suppressive regardless of cell type and, because of rapid onset, may rely on feedforward mechanisms. Surround modulation that evolves later in time is not always suppressive, depending on cell type, and may be generated through different combinations of cortical circuits. Additional analysis of modulation throughout the cortical column suggests the possibility that the larger excitatory fields of facilitative cells, primarily found in infragranular layers, may contribute to the second stage of suppression through intracolumnar circuitry.

"The effects of irrelevant stimuli: 1. The time course of stimulus–stimulus and stimulus–response consistency effects with Stroop-like stimuli, Simon-like tasks, and their factorial combinations": Correction to Kornblum et al. (1999).

"The effects of irrelevant stimuli: 1. The time course of stimulus–stimulus and stimulus–response consistency effects with Stroop-like stimuli, Simon-like tasks, and their factorial combinations": Correction to Kornblum et al. (1999).

Multiple spike time patterns occur at bifurcation points of membrane potential dynamics

Event Abstract Back to Event Multiple spike time patterns occur at bifurcation points of membrane potential dynamics J. Vincent Toups1, Jean-Marc Fellous2, Peter J. Thomas3*, Terrence J. Sejnowski4, 5, 6 and Paul H. Tiesinga1, 7 1 University of North Carolina at Chapel Hill, United States 2 University of Arizona, United States 3 Case Western Reserve University , Department of Mathematics, United States 4 Salk Institute, United States 5 HHMI, United States 6 University of California at San Diego, United States 7 Radboud University, Netherlands The response of a neuron to fluctuating current injected in vitro typically elicits a reliable and precisely timed sequence of action potentials when the same waveform is repeated. The effects that different stimulus conditions occurring in vivo might have on the reproducibility of output spike times remains an open question. To address this question, we somatically injected an aperiodic current into cortical neurons in vitro and varied the amplitude of the fluctuations and the constant pedestal or offset. As the amplitude of the fluctuations was increased the spike reliabilities increased and the spike times remained stable over a range of values. However, at exceptional values called bifurcation points, large shifts in the spike times were obtained in response to small changes in the stimulus amplitude. At such bifurcation points, multiple spike patterns were revealed with an unsupervised method. Increasing the current offset, which mimicked an increase in network activity, also increased the spike time reliability, but the spike times shifted earlier with increasing offset. Although the reliability was reduced at bifurcation points, the information about the stimulus time course was increased because each of the spike time patterns contained different information about the input. Conference: Computational and Systems Neuroscience 2010, Salt Lake City, UT, United States, 25 Feb - 2 Mar, 2010. Presentation Type: Poster Presentation Topic: Poster session III Citation: Toups J, Fellous J, Thomas PJ, Sejnowski TJ and Tiesinga PH (2010). Multiple spike time patterns occur at bifurcation points of membrane potential dynamics. Front. Neurosci. Conference Abstract: Computational and Systems Neuroscience 2010. doi: 10.3389/conf.fnins.2010.03.00244 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 04 Mar 2010; Published Online: 04 Mar 2010. * Correspondence: Peter J Thomas, Case Western Reserve University, Department of Mathematics, Cleveland, United States, pjthomas@cwru.edu Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers J. Vincent Toups Jean-Marc Fellous Peter J Thomas Terrence J Sejnowski Paul H Tiesinga Google J. Vincent Toups Jean-Marc Fellous Peter J Thomas Terrence J Sejnowski Paul H Tiesinga Google Scholar J. Vincent Toups Jean-Marc Fellous Peter J Thomas Terrence J Sejnowski Paul H Tiesinga PubMed J. Vincent Toups Jean-Marc Fellous Peter J Thomas Terrence J Sejnowski Paul H Tiesinga Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Time course of processing emotional stimuli as a function of perceived emotional intelligence, anxiety, and depression.

An individual's self-reported abilities to attend to, understand, and reinterpret emotional situations or events have been associated with anxiety and depression, but it is unclear how these abilities affect the processing of emotional stimuli, especially in individuals with these symptoms. The present study recorded event-related brain potentials while individuals reporting features of anxiety and depression completed an emotion-word Stroop task. Results indicated that anxious apprehension, anxious arousal, and depression were associated with self-reported emotion abilities, consistent with prior literature. In addition, lower anxious apprehension and greater reported emotional clarity were related to slower processing of negative stimuli indexed by event-related potentials (ERPs). Higher anxious arousal and reported attention to emotion were associated with ERP evidence of early attention to all stimuli regardless of emotional content. Reduced later engagement with stimuli was also associated with anxious arousal and with clarity of emotions. Depression was not differentially associated with any emotion processing stage indexed by ERPs. Research in this area may lead to the development of therapies that focus on minimization of anxiety to foster successful emotion regulation.

Oscillatory response function: Towards a parametric model of rhythmic brain activity

Rhythmic brain activity, measured by magnetoencephalography (MEG), is modulated during stimulation and task performance. Here, we introduce an oscillatory response function (ORF) to predict the dynamic suppression-rebound modulation of brain rhythms during a stimulus sequence. We derived a class of parametric models for the ORF in a generalized convolution framework. The model parameters were estimated from MEG data acquired from 10 subjects during bilateral tactile stimulation of fingers (stimulus rates of 4 Hz and 10 Hz in blocks of 0.5, 1, 2, and 4 s). The envelopes of the 17-23 Hz rhythmic activity, computed for sensors above the rolandic region, correlated 25%-43% better with the envelopes predicted by the models than by the stimulus time course (boxcar). A linear model with separate convolution kernels for onset and offset responses gave the best prediction. We studied the generalizability of this model with data from 5 different subjects during a separate bilateral tactile sequence by first identifying neural sources of the 17-23 Hz activity using cortically constrained minimum norm estimates. Both the model and the boxcar predicted strongest modulation in the primary motor cortex. For short-duration stimulus blocks, the model predicted the envelope of the cortical currents 20% better than the boxcar did. These results suggest that ORFs could concisely describe brain rhythms during different stimuli, tasks, and pathologies.

Specific Entrainment of Mitral Cells during Gamma Oscillation in the Rat Olfactory Bulb

Local field potential (LFP) oscillations are often accompanied by synchronization of activity within a widespread cerebral area. Thus, the LFP and neuronal coherence appear to be the result of a common mechanism that underlies neuronal assembly formation. We used the olfactory bulb as a model to investigate: (1) the extent to which unitary dynamics and LFP oscillations can be correlated and (2) the precision with which a model of the hypothesized underlying mechanisms can accurately explain the experimental data. For this purpose, we analyzed simultaneous recordings of mitral cell (MC) activity and LFPs in anesthetized and freely breathing rats in response to odorant stimulation. Spike trains were found to be phase-locked to the gamma oscillation at specific firing rates and to form odor-specific temporal patterns. The use of a conductance-based MC model driven by an approximately balanced excitatory-inhibitory input conductance and a relatively small inhibitory conductance that oscillated at the gamma frequency allowed us to provide one explanation of the experimental data via a mode-locking mechanism. This work sheds light on the way network and intrinsic MC properties participate in the locking of MCs to the gamma oscillation in a realistic physiological context and may result in a particular time-locked assembly. Finally, we discuss how a self-synchronization process with such entrainment properties can explain, under experimental conditions: (1) why the gamma bursts emerge transiently with a maximal amplitude position relative to the stimulus time course; (2) why the oscillations are prominent at a specific gamma frequency; and (3) why the oscillation amplitude depends on specific stimulus properties. We also discuss information processing and functional consequences derived from this mechanism.

A Phenomenological Model for Mechanically Mediated Growth, Remodeling, Damage, and Plasticity of Gel-Derived Tissue Engineered Blood Vessels

Mechanical stimulation has been shown to dramatically improve mechanical and functional properties of gel-derived tissue engineered blood vessels (TEBVs). Adjusting factors such as cell source, type of extracellular matrix, cross-linking, magnitude, frequency, and time course of mechanical stimuli (among many other factors) make interpretation of experimental results challenging. Interpretation of data from such multifactor experiments requires modeling. We present a modeling framework and simulations for mechanically mediated growth, remodeling, plasticity, and damage of gel-derived TEBVs that merge ideas from classical plasticity, volumetric growth, and continuum damage mechanics. Our results are compared with published data and suggest that this model framework can predict the evolution of geometry and material behavior under common experimental loading scenarios.

Motor conflict in Stroop tasks: Direct evidence from single-trial electro-myography and electro-encephalography

Several brain imaging studies have assumed that response conflict is present in Stroop tasks. However, this has not been demonstrated directly. We examined the time-course of stimulus and response conflict resolution in a numerical Stroop task by combining single-trial electro-myography (EMG) and event-related brain potentials (ERP). EMG enabled the direct tracking of response conflict and the peak latency of the P300 ERP wave was used to index stimulus conflict. In correctly responded trials of the incongruent condition EMG detected robust incorrect response hand activation which appeared consistently in single trials. In 50–80% of the trials correct and incorrect response hand activation coincided temporally, while in 20–50% of the trials incorrect hand activation preceded correct hand activation. EMG data provides robust direct evidence for response conflict. However, congruency effects also appeared in the peak latency of the P300 wave which suggests that stimulus conflict also played a role in the Stroop paradigm. Findings are explained by the continuous flow model of information processing: Partially processed task-irrelevant stimulus information can result in stimulus conflict and can prepare incorrect response activity. A robust congruency effect appeared in the amplitude of incongruent vs. congruent ERPs between 330–400 ms, this effect may be related to the activity of the anterior cingulate cortex.

The Resting Human Brain and Motor Learning

SummaryFunctionally related brain networks are engaged even in the absence of an overt behavior. The role of this resting state activity, evident as low-frequency fluctuations of BOLD (see [1] for review, [2–4]) or electrical [5, 6] signals, is unclear. Two major proposals are that resting state activity supports introspective thought or supports responses to future events [7]. An alternative perspective is that the resting brain actively and selectively processes previous experiences [8]. Here we show that motor learning can modulate subsequent activity within resting networks. BOLD signal was recorded during rest periods before and after an 11 min visuomotor training session. Motor learning but not motor performance modulated a fronto-parietal resting state network (RSN). Along with the fronto-parietal network, a cerebellar network not previously reported as an RSN was also specifically altered by learning. Both of these networks are engaged during learning of similar visuomotor tasks [9–22]. Thus, we provide the first description of the modulation of specific RSNs by prior learning—but not by prior performance—revealing a novel connection between the neuroplastic mechanisms of learning and resting state activity. Our approach may provide a powerful tool for exploration of the systems involved in memory consolidation.