Cortical Information Processing Research Articles

Informational Masking Effects on Neural Encoding of Stimulus Onset and Acoustic Change.

Recent investigations using cortical auditory evoked potentials have shown masker-dependent effects on sensory cortical processing of speech information. Background noise maskers consisting of other people talking are particularly difficult for speech recognition. Behavioral studies have related this to perceptual masking, or informational masking, beyond just the overlap of the masker and target at the auditory periphery. The aim of the present study was to use cortical auditory evoked potentials, to examine how maskers (i.e., continuous speech-shaped noise [SSN] and multi-talker babble) affect the cortical sensory encoding of speech information at an obligatory level of processing. Specifically, cortical responses to vowel onset and formant change were recorded under different background noise conditions presumed to represent varying amounts of energetic or informational masking. The hypothesis was, that even at this obligatory cortical level of sensory processing, we would observe larger effects on the amplitude and latency of the onset and change components as the amount of informational masking increased across background noise conditions. Onset and change responses were recorded to a vowel change from /u-i/ in young adults under four conditions: quiet, continuous SSN, eight-talker (8T) babble, and two-talker (2T) babble. Repeated measures analyses by noise condition were conducted on amplitude, latency, and response area measurements to determine the differential effects of these noise conditions, designed to represent increasing and varying levels of informational and energetic masking, on cortical neural representation of a vowel onset and acoustic change response waveforms. All noise conditions significantly reduced onset N1 and P2 amplitudes, onset N1-P2 peak to peak amplitudes, as well as both onset and change response area compared with quiet conditions. Further, all amplitude and area measures were significantly reduced for the two babble conditions compared with continuous SSN. However, there were no significant differences in peak amplitude or area for either onset or change responses between the two different babble conditions (eight versus two talkers). Mean latencies for all onset peaks were delayed for noise conditions compared with quiet. However, in contrast to the amplitude and area results, differences in peak latency between SSN and the babble conditions did not reach statistical significance. These results support the idea that while background noise maskers generally reduce amplitude and increase latency of speech-sound evoked cortical responses, the type of masking has a significant influence. Speech babble maskers (eight talkers and two talkers) have a larger effect on the obligatory cortical response to speech sound onset and change compared with purely energetic continuous SSN maskers, which may be attributed to informational masking effects. Neither the neural responses to the onset nor the vowel change, however, were sensitive to the hypothesized increase in the amount of informational masking between speech babble maskers with two talkers compared with eight talkers.

LHX1-a multifunctional regulator in preoptic area-derived interneuron development.

LHX1-a multifunctional regulator in preoptic area-derived interneuron development.

Spatiotemporal Analysis of Event-related Current Density Reveals Dissociable Effects of Arousal and Valence on Emotional Picture Processing.

BackgroundThe processing of emotional visual stimulation involves the processing of emotional and visuoperceptual information. It is not completely revealed how the valence and arousal affect these two aspects. The objective was to investigate the effects of valence and arousal on spatiotemporal characteristics of cortical information processing using distributed source imaging of event-related current density (ERCD).MethodsElectroencephalograms (64 channels) were recorded from 19 healthy men while presenting affective pictures. Distributed source localization analysis was adopted to obtain the spatiotemporal pattern of ERCD on cortical surface in response to emotional visual stimulation. A nonparametric cluster-based permutation test was used to find meaningful time and space without prior knowledge.ResultsSignificant changes of ERCD in 400–800 ms among positive, negative, and neutral emotional conditions were found in left posterior cingulate cortex (PCC) and right inferior temporal cortex (ITC). In the PCC, the stimuli with higher arousal levels showed more negative ERCD than neutral stimuli. In the ITC, the ERCD for negative stimuli was significantly more negative than those of positive and neutral ones.ConclusionArousal and valence had strong influence on memory encoding and visual analysis at late period. The location and time showing significant change in neural activity according to arousal and valence would provide valuable information for understanding the changes of cortical function by neuropsychiatric disorders.

Evaluation of Electroencephalogram Using Exact Low-Resolution Electromagnetic Tomography During Photic Driving Response in Patients with Migraine

Background: Photophobia is a common feature of migraine, which may involve abnormal cortical information processing. In electroencephalograms (EEG), photic driving is known as a reaction to visual stimulation. Both photophobia and photic driving response are present during light stimulation. We hypothesized that cortical response to photic stimulation would differ between migraine patients with and without aura. Methods: We recruited 50 migraine patients (migraine with aura [MWA] = 21; migraine without aura [MWOA] = 29). Spontaneous eyes-closed resting EEG from 20 electrodes on the scalp during the interictal phase was recorded. After recording, each photic stimulation was separately selected. We analyzed EEG by fast Fourier transform and observed the spectrum frequency peaks and topographies in response to photic stimulation. Exact low-resolution electromagnetic tomography (eLORETA) was used to compute the 3-dimensional intracerebral distribution of EEG activity. Results: Photic stimulation at frequencies 5, 8, 15, and 20 Hz showed significant differences between migraine patients with and without aura. MWOA patients consistently had a stronger response to photic stimulation than MWA patients. In all patients, the differential response was located in the visual cortex, except for the stimulation at 20 Hz, where the difference at subharmonic 10 Hz was located in the parietal cortex (Brodmann Area 7). Conclusion: We confirmed high incidences of photic hypersensitivity and photic driving responses in migraine patients. We suggest that repeated occurrences of cortical spreading depression in MWA may suppress cortical function, thus contributing to a weaker visual cortical response to photic stimulation in MWA patients compared with MWOA patients.

Cortical processing of irrelevant somatosensory information from the leg is altered by attention during early movement preparation

The ability to actively suppress, or gate, irrelevant sensory information is needed for safe and efficient walking in sensory-rich environments. Both attention and the late phase of motor preparation alter somatosensory evoked potentials (SEPs) in healthy adults. The aim of this study was to examine the effect of attention on the processing of irrelevant somatosensory information during the early phase of preparation of plantarflexion movements. Young healthy individuals received tibial nerve stimulation while electroencephalography (EEG) recorded SEPs over the Cz electrode. Three conditions were tested in both legs: 1) Rest, 2) Attend To the stimulated limb, and 3) Attend Away from the stimulated limb. In conditions 2 and 3, vibration (80 Hz) was applied over the medial soleus muscle to cue voluntary plantarflexion movements of the stimulated (Attend To) or non-stimulated leg (Attend Away). Only SEPs delivered during early preparation were averaged for statistical analysis. Results demonstrated a main effect of condition for the N40 and N70 indicating that SEP amplitudes in the Attend To condition were smaller than rest (p ≤ 0.02). For the P50, no interaction effects or main effects were found (p ≥ 0.08). There was no main effect of leg for any component measured. The results indicate that gating of irrelevant sensory information during early preparation occurs in the leg when attention is directed within the same limb. If attention alters the somatosensory stimuli from a leg movement, then directing attention may affect safe community walking.

Expectations about low-level visual features influence late stages of cortical information processing

Expectations about low-level visual features influence late stages of cortical information processing

Auditory Training Reverses Lead (Pb)-Toxicity-Induced Changes in Sound-Azimuth Selectivity of Cortical Neurons.

Lead (Pb) causes significant adverse effects on the developing brain, resulting in cognitive and learning disabilities in children. The process by which lead produces these negative changes is largely unknown. The fact that children with these syndromes also show deficits in central auditory processing, however, indicates a speculative but disturbing relationship between lead-exposure, impaired auditory processing, and behavioral dysfunction. Here we studied in rats the changes in cortical spatial tuning impacted by early lead-exposure and their potential restoration to normal by auditory training. We found animals that were exposed to lead early in life displayed significant behavioral impairments compared with naïve controls while conducting the sound-azimuth discrimination task. Lead-exposure also degraded the sound-azimuth selectivity of neurons in the primary auditory cortex. Subsequent sound-azimuth discrimination training, however, restored to nearly normal the lead-degraded cortical azimuth selectivity. This reversal of cortical spatial fidelity was paralleled by changes in cortical expression of certain excitatory and inhibitory neurotransmitter receptor subunits. These results in a rodent model demonstrate the persisting neurotoxic effects of early lead-exposure on behavioral and cortical neuronal processing of spatial information of sound. They also indicate that attention-demanding auditory training may remediate lead-induced cortical neurological deficits even after these deficits have occurred.

State-Dependent Modulation of Visual Evoked Potentials in a Rodent Genetic Model of Electroencephalographic Instability

Despite normal sleep timing and duration, Egr3-deficient (Egr3−/−) mice exhibit electroencephalographic (EEG) characteristics of reduced arousal, including elevated slow wave (1–4 Hz) activity during wakefulness. Here we show that these mice exhibit state-dependent instability in the EEG. Intermittent surges in EEG power were found in Egr3−/− mice during wakefulness and rapid eye movement sleep, most prominently in the beta (15–35 Hz) range compared to wild type (Egr3+/+) mice. Such surges did not coincide with sleep onset, as the surges were not associated with cessation of electromyographic tone. Cortical processing of sensory information by visual evoked responses (VEP) were found to vary as a function of vigilance state, being of higher magnitude during slow wave sleep (SWS) than wakefulness and rapid eye movement sleep. VEP responses were significantly larger during quiet wakefulness than active wakefulness, in both Egr3−/− mice and Egr3+/+ mice. EEG synchronization in the beta range, previously linked to the accumulation of sleep need over time, predicted VEP magnitude. Egr3−/− mice not only displayed elevated beta activity, but in quiet wake, this elevated beta activity coincides with an elevated evoked response similar to that of animals in SWS. These data confirm that (a) VEPs vary as a function of vigilance state, and (b) beta activity in the EEG is a predictor of state-dependent modulation of visual information processing. The phenotype of Egr3−/− mice indicates that Egr3 is a genetic regulator of these phenomena.

Cortical signatures of wakeful somatosensory processing

Sensory inputs carry critical information for the survival of an organism. In mice, tactile information conveyed by the whiskers is of high behavioural relevance, and is broadcasted across cortical areas beyond the primary somatosensory cortex. Mesoscopic voltage sensitive dye imaging (VSDI) of cortical population response to whisker stimulations has shown that seemingly ‘simple’ sensory stimuli can have extended impact on cortical circuit dynamics. Here we took advantage of genetically encoded voltage indicators (GEVIs) that allow for cell type-specific monitoring of population voltage dynamics in a chronic dual-hemisphere transcranial windowed mouse preparation to directly compare the cortex-wide broadcasting of sensory information in wakening (lightly anesthetized to sedated) and awake mice. Somatosensory-evoked cortex-wide dynamics is altered across brain states, with anatomically sequential hyperpolarising activity observed in the awake cortex. GEVI imaging revealed cortical activity maps with increased specificity, high spatial coverage, and at the timescale of cortical information processing.

Progressive muscle relaxation according to Jacobson for migraine prophylaxis : Clinical effectiveness and mode of action

Progressive muscle relaxation (PMR) after Jacobson has been used for migraine prophylaxis since the early 1970s. Migraine patients are assumed to have an enhanced autonomic arousal which can be counterbalanced by systematic relaxation. Relaxation techniques are thought to reduce the activation level, to alter cortical pain processing and to enhance activation in pain-reducing cortical structures in the periaqueductal grey matter. Meta-analyses could show PMR to be just as efficacious as pharmacological treatment options. A beneficial effect can only arise if regular daily exercises of 5-25 min are performed and the exercises are transferred into the daily routine. This review critically summarizes the empirical findings concerning the effects of PMR on migraine. Alack of recent research on this topic was determined. In a study by this group 50migraine patients and 46healthy controls were examined. It could be shown that in addition to the clinical efficacy on migraine frequency, changes in cortical information processing, measured by means of the evoked potential contingent negative variation (CNV) could also be determined. The initially increased CNV amplitude became normalized after regular PMR training in migraine patients. With the review of PMR studies on migraine prophylaxis and the results of our own study it could be shown that PMR is an efficacious non-pharmacological treatment option for migraine prophylaxis. In addition to its clinical effects, alterations in cortical stimulation processing in terms of anormalization of the CNV could be documented.

Coordinated neuronal ensembles in primary auditory cortical columns.

The synchronous activity of groups of neurons is increasingly thought to be important in cortical information processing and transmission. However, most studies of processing in the primary auditory cortex (AI) have viewed neurons as independent filters; little is known about how coordinated AI neuronal activity is expressed throughout cortical columns and how it might enhance the processing of auditory information. To address this, we recorded from populations of neurons in AI cortical columns of anesthetized rats and, using dimensionality reduction techniques, identified multiple coordinated neuronal ensembles (cNEs), which are groups of neurons with reliable synchronous activity. We show that cNEs reflect local network configurations with enhanced information encoding properties that cannot be accounted for by stimulus-driven synchronization alone. Furthermore, similar cNEs were identified in both spontaneous and evoked activity, indicating that columnar cNEs are stable functional constructs that may represent principal units of information processing in AI.

Metabolic modulation of neuronal gamma-band oscillations

Gamma oscillations (30-100Hz) represent a physiological fast brain rhythm that occurs in many cortex areas in awake mammals, including humans. They associate with sensory perception, voluntary movement, and memory formation and require precise synaptic transmission between excitatory glutamatergic neurons and inhibitory GABAergic interneurons such as parvalbumin-positive basket cells. Notably, gamma oscillations are exquisitely sensitive to shortage in glucose and oxygen supply (metabolic stress), with devastating consequences for higher cognitive functions. Herein, we explored the robustness of gamma oscillations against changes in the availability of alternative energy substrates and amino acids, which is partially regulated by glial cells such as astrocytes. We used organotypic slice cultures of the rat hippocampus expressing acetylcholine-induced persistent gamma oscillations under normoxic recording conditions (20% oxygen fraction). Our main findings are (1) partial substitution of glucose with pyruvate and the ketone body β-hydroxybutyrate increases the frequency of gamma oscillations, even at different stages of neuronal tissue development. (2) Supplementation with the astrocytic neurotransmitter precursor glutamine has no effect on the properties of gamma oscillations. (3) Supplementation with glycine increases power, frequency, and inner coherence of gamma oscillations in a dose-dependent manner. (4) During these treatments switches to other frequency bands or pathological network states such as neural burst firing or synchronized epileptic activity are absent. Our study indicates that cholinergic gamma oscillations show general robustness against these changes in nutrient and amino acid composition of the cerebrospinal fluid; however, modulation of their properties may impact on cortical information processing under physiological and pathophysiological conditions.

PV Interneurons: Critical Regulators of E/I Balance for Prefrontal Cortex-Dependent Behavior and Psychiatric Disorders.

Elucidating the prefrontal cortical microcircuit has been challenging, given its role in multiple complex behaviors, including working memory, cognitive flexibility, attention, social interaction and emotional regulation. Additionally, previous methodological limitations made it difficult to parse out the contribution of certain neuronal subpopulations in refining cortical representations. However, growing evidence supports a fundamental role of fast-spiking parvalbumin (PV) GABAergic interneurons in regulating pyramidal neuron activity to drive appropriate behavioral responses. Further, their function is heavily diminished in the prefrontal cortex (PFC) in numerous psychiatric diseases, including schizophrenia and autism. Previous research has demonstrated the importance of the optimal balance of excitation and inhibition (E/I) in cortical circuits in maintaining the efficiency of cortical information processing. Although we are still unraveling the mechanisms of information representation in the PFC, the E/I balance seems to be crucial, as pharmacological, chemogenetic and optogenetic approaches for disrupting E/I balance induce impairments in a range of PFC-dependent behaviors. In this review, we will explore two key hypotheses. First, PV interneurons are powerful regulators of E/I balance in the PFC, and help optimize the representation and processing of supramodal information in PFC. Second, diminishing the function of PV interneurons is sufficient to generate an elaborate symptom sequelae corresponding to those observed in a range of psychiatric diseases. Then, using this framework, we will speculate on whether this circuitry could represent a platform for the development of therapeutic interventions in disorders of PFC function.

Postnatal Ablation of Synaptic Retinoic Acid Signaling Impairs Cortical Information Processing and Sensory Discrimination in Mice.

Retinoic acid (RA) and its receptors (RARs) are well established essential transcriptional regulators during embryonic development. Recent findings in cultured neurons identified an independent and critical post-transcriptional role of RA and RARα in the homeostatic regulation of excitatory and inhibitory synaptic transmission in mature neurons. However, the functional relevance of synaptic RA signaling in vivo has not been established. Here, using somatosensory cortex as a model system and the RARα conditional knock-out mouse as a tool, we applied multiple genetic manipulations to delete RARα postnatally in specific populations of cortical neurons, and asked whether synaptic RA signaling observed in cultured neurons is involved in cortical information processing in vivo Indeed, conditional ablation of RARα in mice via a CaMKIIα-Cre or a layer 5-Cre driver line or via somatosensory cortex-specific viral expression of Cre-recombinase impaired whisker-dependent texture discrimination, suggesting a critical requirement of RARα expression in L5 pyramidal neurons of somatosensory cortex for normal tactile sensory processing. Transcranial two-photon imaging revealed a significant increase in dendritic spine elimination on apical dendrites of somatosensory cortical layer 5 pyramidal neurons in these mice. Interestingly, the enhancement of spine elimination is whisker experience-dependent as whisker trimming rescued the spine elimination phenotype. Additionally, experiencing an enriched environment improved texture discrimination in RARα-deficient mice and reduced excessive spine pruning. Thus, RA signaling is essential for normal experience-dependent cortical circuit remodeling and sensory processing.SIGNIFICANCE STATEMENT The importance of synaptic RA signaling has been demonstrated in in vitro studies. However, whether RA signaling mediated by RARα contributes to neural circuit functions in vivo remains largely unknown. In this study, using a RARα conditional knock-out mouse, we performed multiple regional/cell-type-specific manipulation of RARα expression in the postnatal brain, and show that RARα signaling contributes to normal whisker-dependent texture discrimination as well as regulating spine dynamics of apical dendrites from layer (L5) pyramidal neurons in S1. Deletion of RARα in excitatory neurons in the forebrain induces elevated spine elimination and impaired sensory discrimination. Our study provides novel insights into the role of RARα signaling in cortical processing and experience-dependent spine maturation.

Spatial-Pooling Memristor Crossbar Converting Sensory Information to Sparse Distributed Representation of Cortical Neurons

The spatial pooler in brain's neocortex models how the cortical neurons learn the feedforward connections and forms the cortical representation from various sensory information. To realize the spatial pooler's operation in hardware, we propose a new spatial-pooling memristor crossbar that converts the inputs from sensory organ into the sparse distributed representation (SDR) of cortical neurons, in this paper. The spatial pooling is composed of overlapping, inhibition, and learning steps. The proposed memristor crossbar can perform exactly the same functions of overlapping, inhibition, and learning with the spatial-pooling software algorithm. By converting the sensory information to SDR using the spatial-pooling memristor crossbar, we can have the following advantages for the cortical information processing: first, preserving the semantic similarity through the spatial pooling; second, changing synaptic weights continuously; third, keeping the sparsity of SDR as low as 2% like brain's neocortex; and fourth, improving the noise robustness. In this paper, these four properties of the spatial pooling in brain's neocortex have been simulated and verified in the memristor crossbar circuit. For verifying the spatial-pooling operation, the memristor crossbar has been tested for MNIST image recognition in this paper. The recognition rate is as high as 95% for the memristor crossbar with 4096 columns.

Hybrid spin‐CMOS stochastic spiking neuron for high‐speed emulation of In vivo neuron dynamics

The spintronic stochastic spiking neuron (S3N) developed herein realises biologically mimetic stochastic spiking characteristics observed within in vivo cortical neurons, while operating several orders of magnitude more rapidly and exhibiting a favourable energy profile. This work leverages a novel probabilistic spintronic switching element device that provides thermally-driven and current-controlled tunable stochasticity in a compact, low-energy, and high-speed package. In order to close the loop, the authors utilise a second-order complementary metal-oxide-semiconductor (CMOS) synapse with variable weight control that accumulates incoming spikes into second-order transient current signals, which resemble the excitatory post-synaptic potentials found in biological neurons, and can be used to drive post-synaptic S3Ns. Simulation program with integrated circuit emphasis (SPICE) simulation results indicate that the equivalent of 1 s of in vivo neuronal spiking characteristics can be generated on the order of nanoseconds, enabling the feasibility of extremely rapid emulation of in vivo neuronal behaviours for future statistical models of cortical information processing. Their results also indicate that the S3N can generate spikes on the order of ten picoseconds while dissipating only 0.6-9.6 μW, depending on the spiking rate. Additionally, they demonstrate that an S3N can implement perceptron functionality, such as AND-gate- and OR-gate-based logic processing, and provide future extensions of the work to more advanced stochastic neuromorphic architectures.

Neuronal Variability as a Proxy for Network State

Characterizing how network state modulates cortical dynamics and information processing is an important step for understanding the neural code. In 2010, Churchland et al. reported wide experimental evidence showing that spontaneous and stimulus-evoked conditions are two distinct states, as indicated by a marked reduction of neuronal variability after stimulus onset.

P.2.034 - Genotype-dependent deterioration of sustained attention by the COMT inhibitor tolcapone after sleep deprivation

Introduction Elevated sleepiness and impaired vigilance due to medical disorders, is often treated by drugs that enhance dopaminergic neurotransmission, including modafinil, caffeine or cocaine [1]. Tolcapone is a brain penetrant selective inhibitor of catechol-O-methyltransferase (COMT) devoid of psychostimulant properties that leads to relatively specific increases in prefrontal cortex (PFC) dopamine signaling [2,3]. Because it hardly affects striatal domapinergic transmission, tolcapone may mitigate subjective and behavioral consequences of sleep deprivation without unwanted psychostimulant adverse effects [2]. Tolcapone also improves cognition and cortical information processing in rested volunteers, depending on the genotype of the functional Val158Met polymorphism of COMT [3]. The impact of this common genetic variant for efficient treatment of hypersomnolence and behavioral markers of increased sleep need after sleep loss is controversial. Here we investigated the potential usefulness of tolcapone to mitigate consequences of sleep deprivation on lapses of sustained attention, and tested the hypothesis that dopamine signaling in the prefrontal cortex (PFC) causally contributes to neurobehavioral and neurophysiological markers of human sleep homeostasis. Methods We first quantified the impact of COMT genotype (SNP-Id: rs4680) on the evolution of attentional lapses during two days of extended wakefulness in a non-tolcapone treated group of 73 volunteers. Subsequently, in an independent group of 30 healthy male study participants, we tested whether selective inhibition of COMT activity by tolcapone counteracts attentional and neurophysiological markers of elevated sleep need in a COMT genotype-dependent manner. 2 x 100 mg tolcapone were administered after 11 and 23 hours, in a randomized, double-blind, placebo-controlled, cross-over design. The psychomotor Vigilance Test (PVT) and objective electroencephalogram (EEG) recordings were carried out in three-hour intervals among all 103 volunteers across the 40 hours of prolonged wakefulness. Repeated measure linear mixed-models were applied, followed by multiple comparison corrected post-hoc testing when appropriate. Results Both COMT genotype and tolcapone modulated the sleep-loss induced impairment of vigilant attention. More specifically, data from the non-tolcapone treated group revealed that Val/Met heterozygotes produced twice as many lapses after a night without sleep compared to Met/Met homozygotes (p Conclusions The current results demonstrate that PFC dopaminergic neurotransmission regulates attentional lapses during sleep deprivation without changing neurophysiological markers of sleep homeostasis. Intriguingly, selective inhibition of COMT can even reverse the expected beneficial effects of pharmacologically enhanced dopaminergic tone after prolonged wakefulness. These findings may have important implications, given the increased use of stimulants in healthy people aimed at improving vigilance and cognitive functions [1,4].

Comparison of cortical responses to the activation of retina by visual stimulation and transcorneal electrical stimulation

BackgroundElectrical stimulation has been widely used in many ophthalmic diseases to modulate neuronal activities or restore partial visual function. Due to the different processing pathways and mechanisms, responses to visual and electrical stimulation in the primary visual cortex and higher visual areas might be different. This differences would shed some light on the properties of cortical responses evoked by electrical stimulation. ObjectiveThis study's goal was to directly compare the cortical responses evoked by visual and electrical stimulation and investigate the cortical processing of visual information and extrinsic electrical signal. MethodsOptical imaging of intrinsic signals (OIS) was used to probe the cortical hemodynamic responses in 11 cats. Transcorneal electrical stimulation (TES) through an ERG-jet contact lens electrode was used to activate visual cortices. Full-field and peripheral drifting gratings were used as the visual stimuli. ResultsThe response latency evoked by TES was shorter than that responding to visual stimulation (VS). Cortical responses evoked by VS were retinotopically organized, which was consistent with previous studies. On the other hand, the cortical region activated by TES was preferentially located in the secondary visual cortex (Area 18), while the primary visual cortex (Area 17) was activated by a higher current intensity. Compared with the full-field VS, the cortical response in Area 18 to TES with a current intensity above 1.2 mA was significantly stronger. ConclusionAccording to our results, we provided some evidence that the cortical processing of TES was influenced by the distribution of the electrical field in the retina and the activating threshold of different retinal ganglion cells.

The dynamics of error processing in the human brain as reflected by high-gamma activity in noninvasive and intracranial EEG

Error detection in motor behavior is a fundamental cognitive function heavily relying on local cortical information processing. Neural activity in the high-gamma frequency band (HGB) closely reflects such local cortical processing, but little is known about its role in error processing, particularly in the healthy human brain. Here we characterize the error-related response of the human brain based on data obtained with noninvasive EEG optimized for HGB mapping in 31 healthy subjects (15 females, 16 males), and additional intracranial EEG data from 9 epilepsy patients (4 females, 5 males). Our findings reveal a multiscale picture of the global and local dynamics of error-related HGB activity in the human brain. On the global level as reflected in the noninvasive EEG, the error-related response started with an early component dominated by anterior brain regions, followed by a shift to parietal regions, and a subsequent phase characterized by sustained parietal HGB activity. This phase lasted for more than 1 s after the error onset. On the local level reflected in the intracranial EEG, a cascade of both transient and sustained error-related responses involved an even more extended network, spanning beyond frontal and parietal regions to the insula and the hippocampus. HGB mapping appeared especially well suited to investigate late, sustained components of the error response, possibly linked to downstream functional stages such as error-related learning and behavioral adaptation. Our findings establish the basic spatio-temporal properties of HGB activity as a neural correlate of error processing, complementing traditional error-related potential studies.