Slow Negative Potential Research Articles

Slow negative potentials in the pre-stimulus period in norm and patients with the first episode of schizophrenia

Behavioral data (correct response latency and errors number increase) indicate a significant decrease in the task performance efficiency in patients with the first episode of schizophrenia, compared to the norm. At the same time the SNP 1, 2, 3 amplitudes were found to enhance in the patients group, compared to the norm, which may reflect a compensatory activation of predictive attention and inhibition cortical networks for increase the response efficiency. Intergroup differences in the topography of the SNP1 and SNP2 peaks amplitude suggest “disorganization” of the left hemisphere cognitive control cortical networks at the early stage of schizophrenia. It is assumed that the SNP 1, 2, 3 components can be considered as potentially significant clinically markers of cognitive control disorders in schizophrenia.

Dynamic alpha power modulations and slow negative potentials track natural shifts of spatio-temporal attention.

Alpha power modulations and slow negative potentials have previously been associated with anticipatory processes in spatial and temporal top-down attention. In typical experimental designs, however, neural responses triggered by transient stimulus onsets can interfere with attention-driven activity patterns and our interpretation of such. Here, we investigated these signatures of spatio-temporal attention in a dynamic paradigm free from potentially confounding stimulus-driven activity using electroencephalography. Participants attended the cued side of a bilateral stimulus rotation and mentally counted how often one of two remembered sample orientations (i.e., the target) was displayed while ignoring the uncued side and non-target orientation. Afterwards, participants performed a delayed match-to-sample task, in which they indicated if the orientation of a probe stimulus matched the corresponding sample orientation (previously target or non-target). We observed dynamic alpha power reductions and slow negative waves around task-relevant points in space and time (i.e., onset of the target orientation in the cued hemifield) over posterior electrodes contralateral to the locus of attention. In contrast to static alpha power lateralization, these dynamic signatures correlated with subsequent memory performance (primarily detriments for matching probes of the non-target orientation), suggesting a preferential allocation of attention to task-relevant locations and time points at the expense of reduced resources and impaired performance for information outside the current focus of attention. Our findings suggest that humans can naturally and dynamically focus their attention at relevant points in space and time and that such spatio-temporal attention shifts can be reflected by dynamic alpha power modulations and slow negative potentials.

OC10: Effect of painful electrical stimuli on readiness potential in the human brain

The major aim of the present study was to investigate whether painful stimuli have a differential effect on the Readiness Potential (RP) in terms of the early and late components. We hypothesized that painful stimuli would modulate the cortical movement preparatory activity and the components to a different extent when compared to non-painful stimuli. The readiness potential (RP), which is a slow negative electrical brain potential that occurs before voluntary movement, can be interpreted as a measure of intrinsic brain activity originating from self-regulating mechanisms. Early and late components of the RP may indicate clinical-neurophysiological features such as motivation, preparation, intention, and initiation of voluntary movements. 15 healty volunteers were enrolled in this study. We conducted electrical stimulation trials in two randomized blocks termed as “no-pain condition” and “pain condition“. Our results demonstrated that painful stimuli were preceded by an enhanced RP at the Cz channel (p<0.05). The mean amplitude of the RP at the early phase was significantly higher for the painful stimuli when compared to the non-painful stimuli (p<0.05). Our results indicate that electrical painful stimuli, which can be considered as an unpleasant and stressful condition, modulate the motor preparation at sensory motor regions to a different extent when compared to non-painful electrical stimuli. Since early component of the RP represents cortical activation due to anticipation of the stimuli and the allocation of attentional resources, our results suggest that painful stimuli may affect the motor preparation processes and the prediction of the movement at the cortical level.

Neural Correlates of Aging-Related Differences in Pro-active Control in a Dual Task.

Background: Multi-tasking is usually impaired in older people. In multi-tasking, a fixed order of sub-tasks can improve performance by promoting a time-structured preparation of sub-tasks. How proactive control prioritizes the pre-activation or inhibition of complex tasks in older people has received no sufficient clarification so far.Objective: To explore the effects of aging on neural proactive control mechanisms in a dual task.Methodology: To address this question, the psychological refractory period (PRP) paradigm was used. Two 2-alternative-forced-choice reaction tasks with a predefined order (T1 and T2) signaled by a cue had to be executed simultaneously or consecutively by young (mean age 25.1 years, n = 36) and old subjects (mean age 70.4 years, n = 118). Performance indices of dual-task preparation were used to assess the focused preparation of T1 and T2. To compare preparatory mechanisms at the neurophysiologic level, multi-channel electroencephalogram (EEG) was recorded and negative slow cortical potentials (SCPs) were analyzed as objective markers of the amount and localization of cortical pre-activation before sub-task presentation.Results: Dual-task performance was significantly slower in old adults. T1 performance was facilitated in both age groups, but T2 processing in old adults was not optimized by the temporal structure as efficiently as in young adults. Also, only young adults manifested a stable pattern of focused of negative slow-wave activity increase at medial frontal and right-hemisphere posterior regions, which was associated with a coordinated preparatory T1 pre-activation and T2 deferment, while old adults manifested a broad topographic distribution of negative SCPs associated with a pre-activation of sensory and motor processes.Conclusions: These observations demonstrate that the proactive preparation for dual tasking is altered with aging. It is suggested that in young adults, attention-based pre-activation of working memory and inhibitory networks in the right hemisphere synchronizes the simultaneous preparation of the two sub-tasks, whereas in old adults, sensory and motor networks appear to be non-specifically pre-activated for subsequent deferred mode of processing.

Effect of Painful Electrical Stimuli on Readiness Potential in the Human Brain.

The readiness potential (RP), which is a slow negative electrical brain potential that occurs before voluntary movement, can be interpreted as a measure of intrinsic brain activity originating from self-regulating mechanisms. Early and late components of the RP may indicate clinical-neurophysiological features such as motivation, preparation, intention, and initiation of voluntary movements. In the present study, we hypothesized that electrical pain stimuli modulate the preparatory brain activity for movement. The grand average evoked potentials were measured at sensory motor regions with EEG during an experimental protocol consisting of painful and nonpainful stimuli. Our results demonstrated that painful stimuli were preceded by an enhanced RP when compared to non-painful stimuli at the Cz channel (p < 0.05). Furthermore, the mean amplitude of the RP at the early phase was significantly higher for the painful stimuli when compared to the non-painful stimuli (p < 0.05). Our results indicate that electrical painful stimuli, which can be considered as an unpleasant and stressful condition, modulate the motor preparation at sensory motor regions to a different extent when compared to non-painful electrical stimuli. Since early component of the RP represents cortical activation due to anticipation of the stimuli and the allocation of attentional resources, our results suggest that painful stimuli may affect the motor preparation processes and the prediction of the movement at the cortical level.

\u201cFree won\u2019t\u201d after a beer or two: chronic and acute effects of alcohol on neural and behavioral indices of intentional inhibition

BackgroundResponse inhibition can be classified into stimulus-driven inhibition and intentional inhibition based on the degree of endogenous volition involved. In the past decades, abundant research efforts to study the effects of alcohol on inhibition have focused exclusively on stimulus-driven inhibition. The novel Chasing Memo task measures stimulus-driven and intentional inhibition within the same paradigm. Combined with the stop-signal task, we investigated how alcohol use affects behavioral and psychophysiological correlates of intentional inhibition, as well as stimulus-driven inhibition.MethodsExperiment I focused on intentional inhibition and stimulus-driven inhibition in relation to past-year alcohol use. The Chasing Memo task, the stop-signal task, and questionnaires related to substance use and impulsivity were administered to 60 undergraduate students (18–25 years old). Experiment II focused on behavioral and neural correlates acute alcohol use on performance on the Chasing Memo task by means of electroencephalography (EEG). Sixteen young male adults (21–28 years old) performed the Chasing Memo task once under placebo and once under the influence of alcohol (blood alcohol concentration around 0.05%), while EEG was recorded.ResultsIn experiment I, AUDIT (Alcohol Use Disorder Identification Test) total score did not significantly predict stimulus-driven inhibition or intentional inhibition performance. In experiment II, the placebo condition and the alcohol condition were comparable in terms of behavioral indices of stimulus-driven inhibition and intentional inhibition as well as task-related EEG patterns. Interestingly, a slow negative readiness potential (RP) was observed with an onset of about 1.2 s, exclusively before participants stopped intentionally.ConclusionsThese findings suggest that both past-year increases in risky alcohol consumption and moderate acute alcohol use have limited effects on stimulus-driven inhibition and intentional inhibition. These conclusions cannot be generalized to alcohol use disorder and high intoxication levels. The RP might reflect processes involved in the formation of an intention in general.

Do readiness potentials happen all the time?

The Readiness Potential (RP) is a slow negative EEG potential found in the seconds preceding voluntary actions. Here, we explore whether the RP is found only at this time, or if it also occurs when no action is produced. Recent theories suggest the RP reflects the average of accumulated stochastic fluctuations in neural activity, rather than a specific signal related to self-initiated action: RP-like events should then be widely present, even in the absence of actions. We investigated this hypothesis by searching for RP-like events in background EEG of an appropriate dataset for which the action-locked EEG had previously been analysed to test other hypotheses [Khalighinejad, N., Brann, E., Dorgham, A., Haggard, P. Dissociating cognitive and motoric precursors of human self-initiated action. Journal of Cognitive Neuroscience. 2019, 1-14]. We used the actual mean RP as a template, and searched the entire epoch for similar neural signals, using similarity metrics that capture the temporal or spatial properties of the RP. Most EEG epochs contained a number of events that were similar to the true RP, but did not lead directly to any voluntary action. However, these RP-like events were equally common in epochs that eventually terminated in voluntary actions as in those where voluntary actions were not permitted. Events matching the temporal profile of the RP were also a poor match for the spatial profile, and vice versa. We conclude that these events are false positives, and do not reflect the same mechanism as the RP itself. Finally, applying the same template-search algorithm to simulated EEG data synthesized from different noise distributions showed that RP-like events will occur in any dataset containing the 1⁄f noise ubiquitous in EEG recordings. To summarise, we found no evidence of genuinely RP-like events at any time other than immediately prior to self-initiated actions. Our findings do not support a purely stochastic model of RP generation, and suggest that the RP may be a specific precursor of self-initiated voluntary actions.

Contingent negative variation in acute trauma patients: A prospective exploratory study

It is still unclear why some individuals completely recover after an acute trauma and others develop a long-lasting post-traumatic stress disorder (PTSD). This study investigates whether the contingent negative variation (CNV) – a slow negative event-related potential – may be associated with the occurrence of PTSD after acute trauma. CNV (auditory 2-stimulus reaction time paradigm) was recorded within one month as well as 6 months after an acute trauma (dangerous or grave physical injuries, witnessing of attempted suicide or murder, robbery, extortion, accidents, heavy illness, death or loss of an important person, hostage-taking) in 39 otherwise healthy adults and compared with CNV recordings in 38 healthy control subjects without potentially traumatizing experience in their history. According to their subsequent clinical course, these subjects were divided into two groups: participants who recovered completely 1 month after the trauma (PTSD- group, n = 31), and those who began to experience PTSD (PTSD+ group, n = 8). Patients from both trauma groups were characterized by a significantly longer reaction time immediately after the trauma. The PTSD+ group demonstrated lower amplitudes of the late CNV component immediately and six months after the trauma compared with the PTSD- and the control group. Whether the lower CNV amplitudes in patients who develop PTSD after the acute trauma, which is already present in the first days after the trauma, may be related to a higher risk for development of PTSD in these subjects, this has to be clarified in further prospective studies.

F11. Scalp EEG recording of direct current shifts during generalized spike-and-wave complexes in adult idiopathic generalized epilepsy

Introduction Direct current (DC) shifts are EEG components slower than delta waves. In focal epilepsy, ictal DC shifts recorded with intracranial and scalp electrodes have been reported to be helpful to delineate epileptogenic zone. Here we investigated DC shifts during generalized spike-and-wave complexes (SWC) in adult patients with idiopathic generalized epilepsy (IGE). Methods Nine patients with electro-clinical diagnosis of IGE (four males), age 35 ± 13 years (mean ± SD), were included. Conventional scalp EEG was recorded for around 30 min, using Ag/AgCl electrodes set according to international 10–20 system, with sampling frequency of 500 Hz. In total, 55 EEG records for 1836 min (mean 6.9 records per patient) were analyzed. All records were reviewed offline under the condition of TC 0.3 s, 30 mm/s, and HF 60, in various montages, all SWC were marked, and segments with significant artifacts were excluded by visual inspection. Then the reviewing condition was changed into the average reference montage excluding frontopolar and earlobe electrodes, TC 2.0 s, 60 s/page, and HF15. Baselines of each EEG waveform were set referring to the segment from 20 s to 10 s before the SWC onset. DC shifts were defined as sustained negative and/or positive slow potentials with the amplitude higher than 20 μ V, better delineated with TC 2.0 s than 0.3 s, and reproducible in location within each patient. Results Among 272 SWC, 175 eligible SWC were analyzed (duration 1.5 ± 1.6 s, amplitude 9.1 ± 17.1 μ V), and DC shifts were present at 30 times (17.1% of SWC analyzed, amplitude 29.7 ± 20.2 μ V). DC shifts were mainly observed in fontal and frontopolar electrodes. SWC with DC shifts showed significantly longer duration than those without (2.9 ± 3.1 s v.s. 1.2 ± 0.7 s, p = 0.008). Amplitude and duration of DC shifts showed significant positive linear correlation (r = 0.60, p Conclusion Scalp-recorded DC shifts during SWC was associated with persistent EEG seizures in adult patients with IGE. More confined distribution of DC shifts than that of SWC may reflect heterogeneous epileptogenicity within each IGE patient.

A Randomized Controlled ERP Study on the Effects of Multi-Domain Cognitive Training and Task Difficulty on Task Switching Performance in Older Adults.

Executive functions are subject to a marked age-related decline, but have been shown to benefit from cognitive training interventions. As of yet, it is, however, still relatively unclear which neural mechanism can mediate training-related performance gains. In the present electrophysiological study, we examined the effects of multi-domain cognitive training on performance in an untrained cue-based task switch paradigm featuring Stroop color words: participants either had to indicate the word meaning of Stroop stimuli (word task) or perform the more difficult task of color naming (color task). One-hundred and three older adults (>65 years old) were randomly assigned to a training group receiving a 4-month multi-domain cognitive training, a passive no-contact control group or an active (social) control group receiving a 4-month relaxation training. For all groups, we recorded performance and EEG measures before and after the intervention. For the cognitive training group, but not for the two control groups, we observed an increase in response accuracy at posttest, irrespective of task and trial type. No training-related effects on reaction times were found. Cognitive training was also associated with an overall increase in N2 amplitude and a decrease of P2 latency on single trials. Training-related performance gains were thus likely mediated by an enhancement of response selection and improved access to relevant stimulus-response mappings. Additionally, cognitive training was associated with an amplitude decrease in the time window of the target-locked P3 at fronto-central electrodes. An increase in the switch positivity during advance task preparation emerged after both cognitive and relaxation training. Training-related behavioral and event-related potential (ERP) effects were not modulated by task difficulty. The data suggest that cognitive training increased slow negative potentials during target processing which enhanced the N2 and reduced a subsequent P3-like component on both switch and non-switch trials and irrespective of task difficulty. Our findings further corroborate the effectiveness of multi-domain cognitive training in older adults and indicate that ERPs can be instrumental in uncovering the neural processes underlying training-related performance gains.

First objective evaluation of taste sensitivity to 6-n-propylthiouracil (PROP), a paradigm gustatory stimulus in humans

Practical and reliable methods for the objective measure of taste function are critically important for studying eating behavior and taste function impairment. Here, we present direct measures of human gustatory response to a prototypical bitter compound, 6-n-propyltiouracil (PROP), obtained by electrophysiological recordings from the tongue of subjects who were classified for taster status and genotyped for the specific receptor gene (TAS2R38), and in which taste papilla density was determined. PROP stimulation evoked negative slow potentials that represent the summated depolarization of taste cells. Depolarization amplitude and rate were correlated with papilla density and perceived bitterness, and associated with taster status and TAS2R38. Our study provides a robust and generalizable research tool for the quantitative measure of peripheral taste function, which can greatly help to resolve controversial outcomes on the PROP phenotype role in taste perception and food preferences, and be potentially useful for evaluating nutritional status and health.

Can ionic diffusion have an effect on extracellular potentials?

Several pathological conditions, such as hypoxia, anoxia, ischemia and spreading depression are associated with ion concentration changes in the extracellular space (ECS) [1]. Also during non-pathological conditions, endured periods of intense neural signaling may cause local ion concentration changes in the millimolar range. Changes in ion concentrations are often accompanied by a slow negative potential shift measured in the ECS [1-3], the origin of which is not properly understood. In computational neuroscience, it is common to use the simplifying assumption that diffusive currents (along concentration gradients) are negligible compared to Ohmic currents (along electrical fields). This is, for example, an underlying assumption in the cable equation used in most multi-compartmental neural models. It is also an underlying assumption in standard current source density (CSD) theory, which predicts neural current sources from recordings of extracellular potentials. However, theoretical studies have identified scenarios where large, but biologically realistic, ion concentration gradients may induce diffusive currents that are comparable in magnitude to Ohmic currents [4,5]. In the current work, we have explored possible effects that diffusive currents may have on the extracellular potential in a cortical column. To do this, we developed a hybrid simulation framework: First, we used the simulator NEURON (and an available multicompartmental neural model with realistic morphology [6]) to simulate the transmembrane ionic output from a small population of cortical neurons driven by realistic synaptic input. Next, we used a separate scheme to predict variations in extracellular potentials and ion concentrations. The scheme was based on the Nernst-Planck equations for electrodiffusion and the constraint of electroneutrality, and represents a novel, efficient and generally applicable method for simulating extracellular dynamics surrounding multicompartmental neural models or networks of such (e.g., the Blue Brain simulator). Our key findings were: (i) Morphology-dependent distributions of transmembrane current sources/sinks induced sustained extracellular potentials. Spatial variations of the ECS potential were of the order of a few mV across the depth of the cortical columns, which is similar to experimentally observed sustained potential profiles [2,3]. (ii) Long periods of neuronal output (simulations were run for 80 s) could change local ECS ion concentrations by several millimolars. (iii) For large, but realistic, concentration gradients in the ECS, diffusive currents were of the same magnitude as Ohmic currents. (iv) Diffusive currents could have a significant impact on the sustained extracellular potentials, and could be a possible explanation to the observed relationship between ionic shifts and voltage drops in the ECS [1-3]. (v) Variation in concentrations and diffusive currents took place at the time scale of several seconds, and had little impact on the frequencies that are of predominant interest in standard CSD-analysis.

Simultaneous measurement of electroencephalography and near-infrared spectroscopy during voluntary motor preparation

We investigated the relationship between electrophysiological activity and haemodynamic response during motor preparation by simultaneous recording of electroencephalography (EEG) and near-infrared spectroscopy (NIRS). It is still unknown how exactly EEG signals correlate with the haemodynamic response, although the activation in the premotor area during motor preparation has been captured by EEG and haemodynamic approaches separately. We conducted EEG-NIRS simultaneous recordings over the sensorimotor area with a self-paced button press task. Participants were instructed to press a button at their own pace after a cue was shown. The result showed that the readiness potential (RP), a negative slow potential shift occurring during motor preparation, on C3 in the extended 10–20 system occurred about 1000 ms before the movement onset. An increase in concentration of oxyhaemoglobin (oxyHb) in the premotor cortex during motor preparation was also confirmed by NIRS, which resulted in a significant correlation between the amplitude of the RP and the change in oxyHb concentration (Pearson’s correlation r2 = 0.235, p = 0.03). We show that EEG-NIRS simultaneous recording can demonstrate the correlation between the RP and haemodynamic response in the premotor cortex contralateral to the performing hand.

Increased motor preparation activity during fluent single word production in DS: A correlate for stuttering frequency and severity

Abnormal speech motor preparation is suggested to be a neural characteristic of stuttering. One of the neurophysiological substrates of motor preparation is the contingent negative variation (CNV). The CNV is an event-related, slow negative potential that occurs between two defined stimuli. Unfortunately, CNV tasks are rarely studied in developmental stuttering (DS). Therefore, the present study aimed to evaluate motor preparation in DS by use of a CNV task. Twenty five adults who stutter (AWS) and 35 fluent speakers (FS) were included. They performed a picture naming task while an electro-encephalogram was recorded. The slope of the CNV was evaluated at frontal, central and parietal electrode sites. In addition, a correlation analysis was performed with stuttering severity and frequency measures.There was a marked increase in CNV slope in AWS as compared to FS. This increase was observed over the entire scalp with respect to stimulus onset, and only over the right hemisphere with respect to lip movement onset. Moreover, strong positive correlations were found between CNV slope and stuttering frequency and severity. As the CNV is known to reflect the activity in the basal ganglia-thalamo-cortical-network, the present findings confirm an increased activation of this loop during speech motor preparation in stuttering. The more a person stutters, the more neurons of this cortical–subcortical network seem to be activated. Because this increased CNV slope was observed during fluent single word production, it is discussed whether or not this observation refers to a successful compensation strategy.

41. Slow negative erp recorded in human hippocampi during a simple sensorimotor task occurs independently of motor execution

A hippocampal-prominent slow negativity with a peak latency at around 450 ms is consistently observed as a correlate of hippocampal activity during various cognitive tasks. Some intracranial EEG studies demonstrated that hippocampal evoked activity is related to movement execution as well as stimulus evaluation and associated memory processes. The aim of the present study was to investigate the temporal relationship between the latency of the hippocampal slow negative potential and motor responses. We analyzed ERPs recorded with 22 depth electrodes implanted into the hippocampi of 11 epileptic patients. Subjects were instructed to press a button after the presentation of a tone. In each subject, the artifact-free EEG segments were (1) sorted according to the respective RT from the fastest to the slowest responses, (2) divided into five subgroups and averaged separately (sorted averages). Finally, the ERP latency and relative latency, obtained from all five sorted averages, were correlated with the median RT for each subgroup. All investigated hippocampi generated a prominent negative ERP peaking at approximately 420 ms. In 16 from 22 cases we found that the ERP latency did not correlate with the reaction time; in different subjects, this potential could either precede or follow the motor response. Our results indicate that the hippocampal negative ERP occurs independently of motor execution. We suggest that hippocampal slow negativity, recorded in a simple sensorimotor task, is related to the evaluation of stimulus meaning within the context of situation.

Spreading depression features and Iba1 immunoreactivity in the cerebral cortex of developing rats submitted to treadmill exercise after treatment with monosodium glutamate

Physical exercise and excessive consumption of monosodium glutamate (MSG) can affect the morphological and electrophysiological organization of the brain during development. However, the interaction of both factors remains unclear. We analyzed the effect of this interaction on the excitability-related phenomenon known as cortical spreading depression (CSD) and the microglial reaction expressed as Iba1-immunolabeled cells in the rat motor cortex. MSG (2g/kg or 4g/kg) was administered every other day during the first 14 postnatal days. Treadmill exercise started at 21–23 days of life and lasted 3 weeks, 5 days/week, for 30min/day. At 45–60 days, CSD was recorded for 4h at two cortical points and the CSD parameters (velocity, amplitude, and duration of the negative potential change) calculated. Confirming previous observations, exercised rats presented with lower CSD velocities (3.29±0.18mm/min) than the sedentary group (3.80±0.18mm/min; P<0.05). MSG increased CSD velocities in the exercised rats compared to saline-treated and exercised animals in a dose-dependent manner (3.49±0.19, 4.05±0.18, and 3.27±0.26 for 2g/kg MSG, 4g/kg MSG, and saline, respectively; P<0.05). The amplitude (ranging from 14.3±5.9 to 18.7±6.2mV) and duration (46.7±11.1 to 60.5±11.6s) of the negative slow potential shift of the CSD were similar in all groups. Both exercise and MSG treatment increased Iba1 immunolabeling. The results confirm that physical exercise decelerates CSD propagation. However, it does not impede the CSD-accelerating action of MSG. These effects were accompanied by a cortical microglia reaction. Therefore, the data suggest that treadmill exercise early in life can influence the development of cortical electrical activity.

Neonatal treatment with monosodium glutamate lastingly facilitates spreading depression in the rat cortex

AimsMonosodium glutamate (MSG) is a neuroexcitatory amino acid used in human food to enhance flavor. MSG can affect the morphological and electrophysiological organization of the brain. This effect is more severe during brain development. Here, we investigated the electrophysiological and morphological effects of MSG in the developing rat brain by characterizing changes in the excitability-related phenomenon of cortical spreading depression (CSD) and microglial reaction. Main methodsFrom postnatal days 1–14, Wistar rat pups received 2 or 4g/kg MSG (groups MSG-2 and MSG-4, respectively; n=9 in each group), saline (n=10) or no treatment (naïve group; n=5) every other day. At 45–60days, CSD was recorded on two cortical points for 4h. The CSD parameters velocity, and amplitude and duration of the negative potential change were calculated. Fixative-perfused brain sections were immunolabeled with anti-IBA-1 antibodies to identify and quantify cortical microglia. Key findingsMSG-4 rats presented significantly higher velocities (4.59±0.34mm/min) than the controls (saline, 3.84±0.20mm/min; naïve, 3.71±0.8mm/min) and MSG-2 group (3.75±0.10mm/min). The amplitude (8.8±2.2 to 11.2±1.9mV) and duration (58.2±7.1 to 73.6±6.0s) of the negative slow potential shift was similar in all groups. MSG-treatment dose-dependently increased the microglial immunolabeling. SignificanceThe results demonstrate a novel, dose-dependent action of MSG in the developing brain, characterized by acceleration of CSD and significant microglial reaction in the cerebral cortex. The CSD effect indicates that MSG can influence cortical excitability, during brain development, as evaluated by CSD acceleration. Data suggest caution when consuming MSG, especially in developing organisms.

Promoting endogenous associative plasticity in human primary motor cortex

Promoting endogenous associative plasticity in human primary motor cortex

P.4.e.002 Standardised LORETA findings in patients with panic disorder before and after cognitive behavioural therapy

Brain activity preceding rapid eye movements (REM) during human REM sleep has remained poorly understood. Slow negative brain potential (pre-REM negativity) appears before REMs. Current sources of this potential were investigated to identify brain activity immediately preceding REMs.In this study, 22 young healthy volunteers (20–25 years old) participated. Polysomnograms were recorded during normal nocturnal sleep. Brain potentials between 200 ms before and 50 ms after the onset of REMs and pseudo-triggers (3000 ms before the onset of REMs) were averaged. Standardized low-resolution brain electromagnetic tomography (sLORETA) was used to estimate current sources of pre-REM negativity.Pre-REM negativity appeared with the maximal amplitude at right prefrontal sites immediately before REMs. However, this negativity did not appear before pseudo-triggers. Current sources of the pre-REM negativity were estimated in the ventromedial prefrontal cortex, uncus, insula, anterior cingulated cortex, basal forebrain, parahippocampal gyrus, premotor cortex and frontal eye field.The pre-REM negativity reflects brain activity coupled with the occurrence of REMs. Results of this study suggest that emotion, memory, and motor-related brain activity might occur before REMs.Pre-REM negativity is expected to be a psychophysiological index for elucidating functions of REM sleep.

Efferent Fibers Innervate Gustatory and Mechanosensitive Afferent Fibers in Frog Fungiform Papillae

A possibility of efferent innervation of gustatory and mechanosensitive afferent fiber endings was studied in frog fungiform papillae with a suction electrode. The amplitude of antidromic impulses in a papillary afferent fiber induced by antidromically stimulating an afferent fiber of glossopharyngeal nerve (GPN) with low voltage pulses was inhibited for 40 s after the parasympathetic efferent fibers of GPN were stimulated orthodromically with high voltage pulses at 30 Hz for 10 s. This implies that electrical positivity of the outer surface of papillary afferent membrane was reduced by the efferent fiber-induced excitatory postsynaptic potential. The inhibition of afferent responses in the papillae was blocked by substance P receptor blocker, L-703,606, indicating that substance P is probably released from the efferent fiber terminals. Slow negative synaptic potential, which corresponded to a slow depolarizing synaptic potential, was extracellularly induced in papillary afferent terminals for 45 s by stimulating the parasympathetic efferent fibers of GPN with high voltage pulses at 30 Hz for 10 s. This synaptic potential was also blocked by L-703,606. These data indicate that papillary afferent fiber endings are innervated by parasympathetic efferent fibers.