Low-resolution Electromagnetic Tomography Analysis Research Articles

Physics-Informed Transfer Learning to Enhance Sleep Staging.

At-home sleep staging using wearable medical sensors poses a viable alternative to in-hospital polysomnography due to its lower cost and lower disruption to the daily lives of patients, especially in the case of long-term monitoring. Machine learning with wearables however is difficult due to the paucity of data from wearable sensors, making automation a challenge. Transfer learning from hospital polysomnograms can boost performance, but is still hindered by differences between wearable and in-hospital EEG resulting in part from differing electrode placement. We improve transfer learning performance by using electrophysiological models of a human head to generate synthetic EEG resembling EEG from a wearable sensor. The data generation method utilizes Low-Resolution Electromagnetic Tomography Analysis (LORETA). Real EEG from standard in- hospital recordings is first mapped to point currents within the brain using LORETA, after which the point currents are used to estimate EEG that would have been recorded using a wearable sensor at any given point on the head. Augmenting source datasets with synthetic data statistically significantly boosted accuracy on a wearable sleep staging task from 80.8% to 81.3% on average, depending on the transfer learning parameters and data sources. Machine learning performance can be improved using data synthesized using physical models. Our approach represents a new form of transfer learning and demonstrates that incorporating domain knowledge of electrophysiological modeling can improve machine learning results for sleep staging tasks. We expect this approach to be particularly useful for EEG data which is hard to collect, or which is obtained using unusual electrode configurations.

Cognitive Network Changes After Exposure to Haptic Vibrotactile Trigger Technology: Results From The ENHANCE Study

The conceptual framework of cognitive networks, or cognits, represents a system of working memory, especially long-term memory arrays that are intrinsically designed to attain certain behavioral ends and that are activated by a neural structure. Despite the fact that cognitions can be used in a plethora of systems, current technologies allow manipulations of the central nervous system (CNS) to execute certain sensory and motor functions. Sensation and tactual perception by the skin are an innate mechanism for human survival and represent our adaptive somatosensorial ability to apprehend information via haptics—the active touch for object recognition and perception by higher centers of the brain. The somatosensation, which is identified by a set of channels and receptors sensitive to a variety of stimuli (thermal, tactile, and mechanical), is critical to survival, balance control, cognition, and pain modulation. Cognits are cutting-edge tools and modalities that provide a landscape of theoretical assets, evidencebased experimental protocols, computational intelligence schemes, and direct empirical modalities that facilitate the understanding of the complex functionalities of the human brain. By evaluating neuroimaging data after somatosensory stimulation and collected via electroencephalogram (EEG), cognition response and change can be obtained that allows researchers to gain a better understanding of emerging scientific approaches aimed at understanding human behavioral outcomes. An emerging technology, haptic vibrotactile trigger technology (VTT), incorporates somatosensory patterns in compression sleeves. eSmartr Smart Compression Sleeves (Srysty Holdings Inc., Mississauga, ON, Canada) with VTT and its Cognitive Boost Technology (CBT) pattern is designed to optimize neural communications for improved mindful wellness. This technology has also been incorporated into patches, braces, apparel (socks), wrist bands, and other routes of delivery. Mindful wellness is considered an outcome of somatosensory intervention that modulates the behavioral responses associated with cognitive networks. Currently, there is limited research exploring these modalities, exposing the need to study new technologies and their influence on somatosensory pathways and cognitive networks. The purpose of this IRB-approved study was to explore the effects of forearm VTT stimulation patterns on cognitive networks by comparing a baseline EEG to an EEG after placing a sleeve incorporating VTT on the right or left forearm of adult healthy individuals. Materials and methods: A baseline EEG was recorded over 5 minutes from 19 scalp locations on 20 subjects ranging in age from 17.6 years to 41.9 years (n=7 females, 13 males). The subject’s dominant arm was then fitted with the eSmartr Smart Compression Sleeve for 20 minutes and another 5-minute EEG was recorded. Both the LORETA (Low Resolution Electromagnetic Tomography Analysis) inverse solution and a power spectral analysis of the surface EEG were calculated. Additionally, for 10 distinct networks, the current sources from 88 Brodmann areas were computed. The variables were absolute power and absolute current density in 1 Hz increments in 10 frequency bands (delta, theta, alpha-1, alpha-2, beta-1, beta-2, beta-3, and hi-beta). Paired t-tests were computed for each individual for all EEG parameters, as well as group paired t-tests, between the baseline EEG and followup EEG. Results: The results showed statistically significant t-test differences (P < 0.01) in both the surface EEG and the LORETA current sources between the baseline measurement and the follow-up ‘sleeve-on’ measurement. The largest differences were detected with a prominent downregulation of alpha and beta frequency powers at both the surface EEG and the LORETA current sources with the “sleeve-on,” as compared to baseline. In addition, the maximal effects of the “sleeve-on” condition were in the left frontal and left temporal surface EEGs and on the medial bank of the somatosensory cortex in the range of the alpha frequency. Changes in the default network and attention network were also prominent. Conclusions: Study results indicate that these non-pharmacologic, non-invasive, haptic vibrotactile trigger technology (VTT) patterned compression sleeves elicited a response in multiple cognitive networks. These networks play a key role in executive function, memory, attention, mood, and information flow. There was a prominent effect of the haptic vibrotactile trigger technology with the CBT- patterned sleeves on the EEG that was primarily located in alpha and beta frequency bands. The substantial impacts on the homuncular projection of the arm to the medial somatosensory cortex as well as the default network demonstrated activity influenced by the patterned sleeve. The mechanisms of action of the VTT sleeve on the brain, neuropathways, and the EEG spectrum are still being investigated. If results are confirmed with further research, this novel VTT technology could be a promising addition as a non-invasive and non-drug treatment approach for a variety of conditions and therapeutic applications.

The relationship between the interictal epileptiform discharge source connectivity and cortical structural couplings in temporal lobe epilepsy.

The objective of this study was to explore the relation between interictal epileptiform discharge (IED) source connectivity and cortical structural couplings (SCs) in temporal lobe epilepsy (TLE). High-resolution 3D-MRI and 32-sensor EEG data from 59 patients with TLE were collected. Principal component analysis was performed on the morphological data on MRI to obtain the cortical SCs. IEDs were labeled from EEG data and averaged. The standard low-resolution electromagnetic tomography analysis was performed to locate the source of the average IEDs. Phase-locked value was used to evaluate the IED source connectivity. Finally, correlation analysis was used to compare the IED source connectivity and the cortical SCs. The features of the cortical morphology in left and right TLE were similar across four cortical SCs, which could be mainly described as the default mode network, limbic regions, connections bilateral medial temporal, and connections through the ipsilateral insula. The IED source connectivity at the regions of interest was negatively correlated with the corresponding cortical SCs. The cortical SCs were confirmed to be negatively related to IED source connectivity in patients with TLE as detected with MRI and EEG coregistered data. These findings suggest the important role of intervening IEDs in treating TLE.

Towards a More Theory-Driven BCI Using Source Reconstructed Dynamics of EEG Time-Series

Currently, the operational electroencephalography (EEG)-based brain–computer interfaces (BCIs) suffer from problems of BCI latency/lag issues, which restricts the use of interfaces impractical scenarios. One of the reasons behind the present challenges is the application of a purely data-driven approach to the BCI pipeline. Although BCI applications have improved significantly with the research in the fields of artificial intelligence (AI) and machine learning (ML), fundamental issues of data-driven training restrict the latency that can be achieved under current BCI paradigms. This work explores the possibility of future BCI using a combination of data-driven and theory-driven methods. In this study, an EEG-BCI dataset from steady-state visually evoked potentials (SSVEPs) is applied, where the SSVEP signals contain, source components from the occipital, parietal and frontal regions of the brain. Source reconstruction is done with the combination of independent component analysis (ICA) and low-resolution electromagnetic tomography analysis (LORETA). This method was able to predict BCI classification labels 5[Formula: see text]s earlier, based on pre-recorded signals from the scalp. The novelty of the current contribution lies in utilizing the source reconstructed EEG time-series for BCI classification, which allows for retention of classification accuracy up to 70% while working with the reduced data dimensionality. Implementation of this algorithm will allow a significant reduction in lag in online BCIs.

Increased Temporal Lobe Beta Activity in Boys With Attention-Deficit Hyperactivity Disorder by LORETA Analysis.

Aim: Attention-deficit hyperactivity disorder (ADHD) is a common childhood neuropsychiatric disorder that affects 6.1 million US children. The mechanism of ADHD is currently unclear. Differences in ADHD presentations between boys and girls are well-established. In the present study, we used quantitative electroencephalography (EEG) to investigate the brain area and EEG bands of boys with ADHD.Methods: This study enrolled 40 boys with ADHD and 40 age-matched controls without ADHD. Low-resolution electromagnetic tomography (LORETA) and instantaneous frequency were used to analyze EEG data to reveal the mechanisms underlying ADHD in boys.Results: We found that the instantaneous frequencies in the T3 and T4 EEG channels in boys with ADHD were significantly higher than those in the controls. The beta band showed significant difference in current density between the ADHD and control groups. In the entire brain area, the bilateral inferior and middle temporal gyrus exhibited the most significant difference between the ADHD and control groups in the EEG beta band. Connectivity analysis revealed an increase in connectivity between the left middle frontal gyrus and fusiform gyrus of the temporal lobe in boys with ADHD.Conclusions: LORETA is a promising tool for analyzing EEG signals and can be used to investigate the mechanism of ADHD. Our results reveal that the inferior temporal gyrus, middle temporal gyrus, and fusiform gyrus of the temporal lobe are potentially involved in the pathogenesis of ADHD in boys. In comparison with other imaging methods, such as magnetic resonance imaging, EEG is easy to perform, fast, and low cost. Our study presents a new approach for investigating the pathogenesis of ADHD in boys.

Quantitative electroencephalogram analysis of frontal cortex functional changes in patients with migraine.

The functional abnormality of brain areas accounting for the migraine remains to be elucidated. Most related studies have used functional magnetic resonance imaging to investigate brain areas involved in migraine. However, the results are heterogeneous. In this study, we used a convenient tool to explore the brain regions involved in migraine. In this study, 40 children with migraine and 40 sex- and age-matched health controls were enrolled, and electroencephalogram was used to explore the functional abnormal areas of migraine through electroencephalogram bands and low-resolution electromagnetic tomography analysis. The results revealed that spectrum edge frequency 50 in all electroencephalogram channels in patients with migraine were lower than those in controls. Significant differences were discovered over frontal areas. In addition, significantly higher current density over the frontopolar prefrontal cortex and orbitofrontal cortex and higher connectivity over the left prefrontal cortex were observed in patients with migraine. We suggest that functional disturbance of the prefrontal cortex may play a potential role in children with migraine, and that low-resolution electromagnetic tomography is a reliable and convenient tool for studying the functional disturbance of migraine.

Sex Differences in QEEG in Psychopath Offenders.

Introduction. Functional brain differences related to sex in psychopathic behavior represent an important field of neuroscience research; there are few studies on this area, mainly in offender samples. Objective. The aim of this study was to investigate the presence of electrophysiological differences between male and female psychopath offenders; specifically, we wanted to assess whether the results in quantitative EEG, low-resolution electromagnetic tomography (LORETA), and changes in synchronous brain activity could be related to sex influence. Sample and Methods. The study included 31 male and 12 female psychopath offenders, according to the Hare Psychopathy Checklist-Revised criteria from 2 prisons located in Havana City. The EEG visual inspection characteristics and the use of frequency domain quantitative analysis techniques are described. Results. The resting EEG visual analyses revealed a high percentage of EEG abnormalities in both studied groups. Significant statistical differences between the mean parameters of cross spectral measures between psychopathic offender groups were found in the beta band at bilateral frontal derivation and centroparietal areas. LORETA showed differences especially in the paralimbic and parieto-occipital areas Synchronization likelihood revealed a significant group effect in the 26 to 30 Hz band. These results indicate that combining quantitative EEG, LORETA analysis, and synchronization likelihood may improve the neurofunctional differentiation between psychopath offenders of both sexes.

Mental Simulation of Facial Expressions: Mu Suppression to the Viewing of Dynamic Neutral Face Videos.

The mirror neuron network (MNN) has been proposed as a neural substrate of action understanding. Electroencephalography (EEG) mu suppression has commonly been studied as an index of MNN activity during execution and observation of hand and finger movements. However, in order to establish its role in higher order processes, such as recognizing and sharing emotions, more research using social emotional stimuli is needed. The current study aims to contribute to our understanding of the sensitivity of mu suppression to facial expressions. Modulation of the mu and occipital alpha (8–13 Hz) rhythms was calculated in 22 participants while they observed dynamic video stimuli, including emotional (happy and sad) and neutral (mouth opening) facial expressions, and non-biological stimulus (kaleidoscope pattern). Across the four types of stimuli, only the neutral face was associated with a significantly stronger mu suppression than the non-biological stimulus. Occipital alpha suppression was significantly greater in the non-biological stimulus than all the face conditions. Source estimation standardized low resolution electromagnetic tomography (sLORETA) analysis comparing the neural sources of mu/alpha modulation between neutral face and non-biological stimulus showed more suppression in the central regions, including the supplementary motor and somatosensory areas, than the more posterior regions. EEG and source estimation results may indicate that reduced availability of emotional information in the neutral face condition requires more sensorimotor engagement in deciphering emotion-related information than the full-blown happy or sad expressions that are more readily recognized.

Electrophysiological Indexes of Incongruent Audiovisual Phonemic Processing: Unraveling the McGurk Effect

In this study the timing of electromagnetic signals recorded during incongruent and congruent audiovisual (AV) stimulation in 14 Italian healthy volunteers was examined. In a previous study (Proverbio et al., 2016) we investigated the McGurk effect in the Italian language and found out which visual and auditory inputs provided the most compelling illusory effects (e.g., bilabial phonemes presented acoustically and paired with non-labials, especially alveolar–nasal and velar–occlusive phonemes). In this study EEG was recorded from 128 scalp sites while participants observed a female and a male actor uttering 288 syllables selected on the basis of the previous investigation (lasting approximately 600 ms) and responded to rare targets (/re/, /ri/, /ro/, /ru/). In half of the cases the AV information was incongruent, except for targets that were always congruent. A pMMN (phonological Mismatch Negativity) to incongruent AV stimuli was identified 500 ms after voice onset time. This automatic response indexed the detection of an incongruity between the labial and phonetic information. SwLORETA (Low-Resolution Electromagnetic Tomography) analysis applied to the difference voltage incongruent–congruent in the same time window revealed that the strongest sources of this activity were the right superior temporal (STG) and superior frontal gyri, which supports their involvement in AV integration.

Comparative analysis of the electroencephalogram in patients with Alzheimer's disease, diffuse axonal injury patients and healthy controls using LORETA analysis.

Alzheimer's disease (AD) is a dementia that affects a large contingent of the elderly population characterized by the presence of neurofibrillary tangles and senile plaques. Traumatic brain injury (TBI) is a non-degenerative injury caused by an external mechanical force. One of the main causes of TBI is diffuse axonal injury (DAI), promoted by acceleration-deceleration mechanisms.ObjectiveTo understand the electroencephalographic differences in functional mechanisms between AD and DAI groups.MethodsThe study included 20 subjects with AD, 19 with DAI and 17 healthy adults submitted to high resolution EEG with 128 channels. Cortical sources of EEG rhythms were estimated by exact low-resolution electromagnetic tomography (eLORETA) analysis.ResultsThe eLORETA analysis showed that, in comparison to the control (CTL) group, the AD group had increased theta activity in the parietal and frontal lobes and decreased alpha 2 activity in the parietal, frontal, limbic and occipital lobes. In comparison to the CTL group, the DAI group had increased theta activity in the limbic, occipital sublobar and temporal areas.ConclusionThe results suggest that individuals with AD and DAI have impairment of electrical activity in areas important for memory and learning.

Pathophysiology of refractory obsessive-compulsive disorder: A study of visual search combined with overactive performance monitoring.

Based on both functional and structural studies of excessive activity, fronto-striatal-thalamic-cortical and cortico-striatal circuits have been hypothesized to underlie the pathophysiology of obsessive-compulsive disorder (OCD). However, the neurobiological underpinnings of OCD refractory to medication and therapy remain controversial. This study aimed to evaluate neuroanatomical abnormalities of the whole brain and to evaluate visual processing in patients with refractory OCD.This study was comprised of 2 experiments. The neuroanatomical abnormalities of the whole brain were evaluated using a visual search in combination with overactive performance monitoring (Experiment I), and visual processing was evaluated using event-related potentials recorded from subjects during performance of a visual search task. We also examined the amplitudes and latency of the error-related negativity (ERN) using a modified flanker task (Experiment II). Standard low-resolution electromagnetic tomography analysis was applied to determine the special areas.Patients with refractory OCD had a significantly greater number of saccades and prolonged latencies relative to the healthy controls. Scalp map topography confirmed that visual cognitive and executive dysfunction was localized to the fusiform gyrus. Furthermore, we found that during a modified flanker task, ERNs had a greater amplitude and a prolonged latency relative to those of the healthy controls. Further data analysis suggested that cognitive dysfunction and compulsive behavior in OCD patients were linked to abnormalities within the dorsolateral prefrontal cortex (DLPFC).We identified abnormal activities within the fusiform gyrus and DLPFC that likely play important roles in the pathophysiology of OCD.

Ventral medial prefrontal cortex (vmPFC) as a target of the dorsolateral prefrontal modulation by transcranial direct current stimulation (tDCS) in drug addiction.

Here, we report some electrophysiologic and imaging effects of the transcranial direct current stimulation (tDCS) over the dorsolateral prefrontal cortex (dlPFC) in drug addiction, notably in alcohol and crack-cocaine dependence. The low resolution electromagnetic tomography (LORETA) analysis obtained through event-related potentials (ERPs) under drug-related cues, more specifically in its P3 segment (300-500ms) in both, alcoholics and crack-cocaine users, showed that the ventral medial prefrontal cortex (vmPFC) was the brain area with the largest change towards increasing activation under drug-related cues in those subjects that kept abstinence during and after the treatment with bilateral tDCS (2mA, 35cm(2), cathodal left and anodal right) over dlPFC, applied repetitively (five daily sessions). In an additional study in crack-cocaine, which showed craving decreases after repetitive bilateral tDCS, we examined data originating from diffusion tensor imaging (DTI), and we found increased DTI parameters in the left connection between vmPFC and nucleus accumbens (NAcc), such as the number of voxels, fractional anisotropy (FA) and apparent diffusion coefficient (ADC), in tDCS-treated crack-cocaine users when compared to the sham-tDCS group. This increasing of DTI parameters was significantly correlated with craving decreasing after the repetitive tDCS. The vmPFC relates to the control of drug seeking, possibly by extinguishing this behavior. In our studies, the bilateral dlPFC tDCS reduced relapses and craving to the drug use, and increased the vmPFC activation under drug cues, which may be of a great importance in the control of drug use in drug addiction.

Electrocortical Reactivity During Self-referential Processing in Female Youth With Borderline Personality Disorder

BackgroundBorderline personality disorder (BPD) is debilitating, and theoretical models have postulated that cognitive-affective biases contribute to the onset and maintenance of BPD symptoms. Despite advances, our understanding of BPD pathophysiology in youth is limited. The present study used event-related potentials (ERPs) to identify cognitive-affective processes that underlie negative self-referential processing in BPD youth. MethodsHealthy females (n = 33) and females with BPD (n = 26) 13 to 22 years of age completed a self-referential encoding task while 128-channel electroencephalography data were recorded to examine early (i.e., P1 and P2) and late (late positive potential [LPP]) ERP components. Whole-brain standardized low-resolution electromagnetic tomography explored intracortical sources underlying significant scalp ERP effects. ResultsCompared to healthy females, participants with BPD endorsed, recalled, and recognized fewer positive and more negative words. Moreover, unlike the healthy group, females with BPD had faster reaction times to endorse negative versus positive words. In the scalp ERP analyses, the BPD group had greater P2 and late LPP positivity to negative as opposed to positive words. For P2 and late LPP, whole-brain standardized low-resolution electromagnetic tomography analyses suggested that females with BPD overrecruit frontolimbic circuitry in response to negative stimuli. ConclusionsCollectively, these findings show that females with BPD process negative self-relevant information differently than healthy females. Clinical implications and future directions are discussed.

EEG source activity during processing of neutral stimuli in subjects with anxiety disorders.

Anxiety disorders are a social problem due to their prevalence and consequences. It is crucial to explore the influence of anxiety on cognitive processes. In this study we recorded EEG activity from 73 subjects (35 patients, 38 controls, matched for age and education) during performance of the Continuous Attention Task. We used low resolution electromagnetic tomography (LORETA) for evaluation of mechanisms of impaired cognitive performance in anxiety disorders. Analysis showed that patients with anxiety disorders committed more errors than the controls, had a short latency of P300 and higher amplitude of ERPs at all steps of stimulus processing. Furthermore, we showed that there was a relationship between the scores of Hamilton Anxiety Scale and Beck Depression Inventory, and amplitudes and latencies of ERPs. The results of LORETA analysis showed that enhanced neural responses were found within circuits mediating visual information processing, sustained attention and anxiety. Also, we found higher current density within areas playing an important role in the brain fear network - anterior cingulate and anterior part of insula. Electrophysiological neuroimaging showed greater recruitment of cognitive resources in anxiety disorders, evidenced by higher current density and activation of greater number of brain areas. Despite the strategy employed to compensate for cognitive problems, the anxiety patients did not achieve the same performance as controls. Present study demonstrates that anxiety disorders influence processing of neutral stimuli and this influence is observable at both behavioral and electrophysiological level. The data suggests instability of neural systems responsible for information selection, working memory, engagement and focusing of attention.

Blunted Neural Responses to Reward in Remitted Major Depression: A High-Density Event-Related Potential Study

BackgroundMajor depressive disorder (MDD) is a highly recurrent condition, and improving our understanding of the abnormalities that persist in remitted MDD (rMDD) may provide insight into mechanisms that contribute to relapse. Reward learning deficits linked to dysfunction in frontostriatal regions are characteristic of MDD. Although initial behavioral evidence of reward learning deficits in rMDD has emerged, it is unclear whether these deficits reflect impairments in neural reward processing that persist into remission. MethodsWe examined behavioral reward learning and 128-channel event-related potentials (ERPs) during a well-validated probabilistic reward task in 26 individuals with rMDD and 34 control subjects with no history of depression. Temporospatial principal components analysis was used to separate overlapping ERP components, and group differences in neural activity in a priori regions were examined using low-resolution electromagnetic tomography. ResultsIndividuals with rMDD displayed reduced behavioral reward learning and blunted ERP amplitude to reward feedback. The reduction in ERP amplitude occurred at a principal components analysis factor that peaked during the time at which phasic reward feedback-related signaling—hypothesized to originate in the striatum and project to the anterior cingulate cortex—is thought to modulate scalp-recorded activity. Consistent with this finding, low-resolution electromagnetic tomography analyses revealed reduced activity in the anterior cingulate cortex in the rMDD group, and this blunting correlated with poorer reward learning. ConclusionsThese findings suggest that the reward learning impairment observed in acute MDD persists into full remission and that these impairments may be attributable to abnormalities in the neural processes that support reward feedback monitoring, particularly within the anterior cingulate cortex.

The mechanism of neurofeedback training for treatment of central neuropathic pain in paraplegia: a pilot study.

BackgroundCentral neuropathic pain has a prevalence of 40 % in patients with spinal cord injury. Electroencephalography (EEG) studies showed that this type of pain has identifiable signatures, that could potentially be targeted by a neuromodulation therapy. The aim of the study was to investigate the putative mechanism of neurofeedback training on central neuropathic pain and its underlying brain signatures in patients with chronic paraplegia.MethodsPatients’ EEG activity was modulated from the sensory-motor cortex, electrode location C3/Cz/C4/P4 in up to 40 training sessions Results. Six out of seven patients reported immediate reduction of pain during neurofeedback training. Best results were achieved with suppressing Ɵ and higher β (20–30 Hz) power and reinforcing α power at C4. Four patients reported clinically significant long-term reduction of pain (>30 %) which lasted at least a month beyond the therapy. EEG during neurofeedback revealed a wide spread modulation of power in all three frequency bands accompanied with changes in the coherence most notable in the beta band. The standardized low resolution electromagnetic tomography analysis of EEG before and after neurofeedback therapy showed the statistically significant reduction of power in beta frequency band in all tested patients. Areas with reduced power included the Dorsolateral Prefrontal Cortex, the Anterior Cingulate Cortex and the Insular Cortex.ConclusionsNeurofeedback training produces both immediate and longer term reduction of central neuropathic pain that is accompanied with a measurable short and long term modulation of cortical activity. Controlled trials are required to confirm the efficacy of this neurofeedback protocol on treatment of pain. The study is a registered UKCRN clinical trial Nr 9824.

One-year-old fear memories rapidly activate human fusiform gyrus.

Fast threat detection is crucial for survival. In line with such evolutionary pressure, threat-signaling fear-conditioned faces have been found to rapidly (<80 ms) activate visual brain regions including the fusiform gyrus on the conditioning day. Whether remotely fear conditioned stimuli (CS) evoke similar early processing enhancements is unknown. Here, 16 participants who underwent a differential face fear-conditioning and extinction procedure on day 1 were presented the initial CS 24 h after conditioning (Recent Recall Test) as well as 9-17 months later (Remote Recall Test) while EEG was recorded. Using a data-driven segmentation procedure of CS evoked event-related potentials, five distinct microstates were identified for both the recent and the remote memory test. To probe intracranial activity, EEG activity within each microstate was localized using low resolution electromagnetic tomography analysis (LORETA). In both the recent (41-55 and 150-191 ms) and remote (45-90 ms) recall tests, fear conditioned faces potentiated rapid activation in proximity of fusiform gyrus, even in participants unaware of the contingencies. These findings suggest that rapid processing enhancements of conditioned faces persist over time.

Training of Affect Recognition impacts electrophysiological correlates of facial affect recognition in schizophrenia: Analyses of fixation-locked potentials

Objectives. Training of Affect Recognition (TAR) is a useful approach to restoring cognitive function in schizophrenic patients. Along with improving visual exploration of faces and altering central information processing in relevant brain areas, TAR attenuates impairments in facial affect recognition. In the present study, we investigate the effects of TAR on early electrophysiological correlates of facial affect recognition in schizophrenia. Methods. The study population comprised 12 schizophrenic patients and 14 healthy controls. In each individual, we carried out EEG, concomitant measurements of scanning eye movements and fixation-based low resolution electromagnetic tomography (sLORETA) analyses of brain electric activity. All analyses were performed at baseline and after participation in TAR. Results. In patients, brain activation patterns significantly changed after completing the TAR. Functional improvements were particularly pronounced in the superior parietal and inferior parietal lobes, where trained patients showed a larger increase in activation than untrained healthy controls. Conclusions. The TAR activates compensatory brain processes involved in the perception, attention and evaluation of emotional stimuli. This may underlie the established behavioral effects of the TAR in schizophrenic patients, which include improvements in facial affect recognition and alterations of visual exploration strategies.

The intention to conceal activates the right prefrontal cortex: an event-related potential study.

Recent studies on deception have shown that a late positive potential (LPP), a component of event-related brain potentials, is elicited when a participant wishes to conceal recognition of the eliciting stimulus. The LPP occurs about 500 ms after stimulus onset and has an occipital scalp distribution with concurrent negativity at frontal sites. The present study investigated the cortical sources of the LPP associated with the intention to conceal. Standardized low-resolution electromagnetic tomography analysis was applied on previously published concealment-related LPP data (Matsuda, Nittono, and Ogawa, 2013, N=30). The cortical sources of the LPP were estimated in the right middle frontal gyrus and the right inferior frontal gyrus, which fits well with the findings of fMRI studies. Previous research suggests that activities in the middle frontal gyrus and the right inferior frontal gyrus are associated with cognitive control and that greater relative right than left frontal activities are associated with withdrawal motivation. On the basis of these findings, it is concluded that the LPP may reflect cognitive control with withdrawal motivation that is recruited by the participants' goal of concealing their recognition and avoiding disclosure. A positive potential at occipital sites can be a sign of the activation in the prefrontal cortex.

Anodal transcranial direct current stimulation (tDCS) increases frontal–midline theta activity in the human EEG: A preliminary investigation of non-invasive stimulation

Rhythmical brain activity in the range between four and eight Hz acquired over frontal–midline EEG recording sites – so called frontal–midline theta activity – is regarded as one of the most prominent neural signatures of sustained attention. It is reported to parametrically increase with cognitive load and is thought to be generated in medial prefrontal cortex. Here we explored the possibility of using anodal transcranial direct current stimulation over frontal sites to enhance frontal–midline theta activity and to increase sustained attention performance. We used a small preliminary sample to test a novel direct current stimulation electrode configuration by which we were able to significantly increase frontal–midline theta amplitude in a resting condition after the end of the stimulation period. Using standardised low resolution electromagnetic tomography analysis the effect in the surface EEG was localised to right prefrontal and left medial prefrontal brain areas. Transcranial direct current stimulation did, however, not have any impact on behavioural performance during a sustained attention task. This most likely was due to a very fast washout of the stimulation’s after effect on theta activity. Although these are only preliminary results from a rather small sample, this study demonstrates that transcranial direct current stimulation can be used to rather selectively enhance frontal–midline theta amplitude.