P300 and time of day: circadian rhythms, food intake, and body temperature

Effects of Ramadan on cognitive functions in young boys

Fasting during Ramadan involves abstaining from food and drink from dawn to sunset, potentially influencing cognitive functions essential for the intellectual development of the youth. Therefore, understanding the effects of fasting on these functions in children/adolescents provides valuable perspectives to enhance education and promote mental well-being. However, studies on children/adolescents in this context are still limited. To evaluate the impact of Ramadan fasting on cognitive functions, including information processing speed, inhibition, decision-making, and auditory attention processes among children and adolescents aged 11 to 15 years. This study was conducted with 24 healthy children/adolescents (aged 12.84 ± 0.69 years). The experimental protocol consisted of two sessions: Before-Ramadan (BR) and at the beginning of the second week of Ramadan (R2). At each session, the boys were randomly tested on simple reaction time (SRT), choice reaction time (CRT), negative priming reaction time (NPRT), and auditory discrimination (P300). The tests were administered and scored by the same person in the different sessions. The study found that Ramadan fasting did not have an effect on various reaction times or on electro-physiological data, including P300 amplitude and latency. The current study, conducted with healthy children/adolescents, indicates that Ramadan fasting had no impact on various reaction times (SRT, CRT, NPRT), suggesting the preservation of information processing speed and decision-making, even in the face of increased task complexity. This is evident, on the one hand, through the maintenance of the ability to react to unexpected events, and, on the other hand, through the mastery of resistance to automatism, thus reflecting the preservation of inhibitory function (NPRT). Regarding P300 data, the absence of changes in latencies and amplitudes suggests that Ramadan fasting did not alter either the evaluation time of auditory stimuli or auditory attention processes.

Test-retest reliability of electroencephalographic and magnetoencephalographic measures elicited during language tasks: A literature review

Electroencephalographic (EEG) and magnetoencephalographic (MEG) recordings during language processing can provide relevant insights on neuroplasticity in clinical populations (including patients with aphasia). To use EEG and MEG in a longitudinal way, the outcome measures should be consistent across time in healthy individuals. Therefore, the current study provides a review on the test-retest reliability of EEG and MEG measures elicited during language paradigms in healthy adults. PubMed, Web of Science and Embase were searched for relevant articles based on specific eligibility criteria. In total, 11 articles were included in this literature review. The test-retest reliability of the P1, N1 and P2 is systematically considered to be satisfactory, whereas findings are more variable for event-related potentials/fields occurring later in time. The within subject consistency of EEG and MEG measures during language processing can be influenced by multiple variables such as the stimulus presentation mode, the offline reference choice and the required amount of cognitive resources during the task. To conclude, most of the available results are favourable regarding the longitudinal use of EEG and MEG measures elicited during language paradigms in healthy young individuals. In view to the use of these techniques in patients with aphasia, future research should focus on whether the same findings apply to different age groups.

The reliability of P300 and the influence of age, gender and education variables in a 50 years and older normative sample

OBJECTIVES

The present study aims to investigate the effects of age, gender, and level of education on P300 in a healthy population, aged 50 years and over; and determine the reliability metrics for different conditions and measurement methods.

METHOD

Auditory and visual oddball recordings of 171 healthy adults were investigated. A fully automated preprocessing was applied to elicit ERP P300. Maximum peak amplitude, latency and mean amplitudes were measured. Data were stratified by age, gender, and education to determine group-level differences by using repeat measures of ANOVA. The internal consistency of P300 was calculated by a split-half method using odd-even segments. Test-retest reliability was assessed by calculating the intraclass correlation coefficient (ICC).

RESULTS

Maximum peak P300 amplitudes were higher in the 50-64 years age group compared to the >65 years age group; and females showed increased P300 amplitudes compared to males. P300 measures showed fair to good internal consistency and poor to good test-retest reliability.

CONCLUSION

Age and gender should be taken into account when designing ERP studies with elderly individuals. P300 showed good internal consistency in general, between gender groups and age groups. Long-term test-retest reliability was lower but acceptable. These findings can be interpreted as the strength of P300 by being an objective and reliable method independent of cultural differences. Here we underline several factors that may affect P300 measures and discuss other possible factors that should be standardized for P300 to be used in clinical settings.

Identification of Food/Nonfood Visual Stimuli from Event-Related Brain Potentials

Although food consumption is one of the most basic human behaviors, the factors underlying nutritional preferences are not yet clear. The use of classification algorithms can clarify the understanding of these factors. This study was aimed at measuring electrophysiological responses to food/nonfood stimuli and applying classification techniques to discriminate the responses using a single-sweep dataset. Twenty-one right-handed male athletes with body mass index (BMI) levels between 18.5% and 25% (mean age: 21.05 ± 2.5) participated in this study voluntarily. The participants were asked to focus on the food and nonfood images that were randomly presented on the monitor without performing any motor task, and EEG data have been collected using a 16-channel amplifier with a sampling rate of 1024 Hz. The SensoMotoric Instruments (SMI) iView XTM RED eye tracking technology was used simultaneously with the EEG to measure the participants' attention to the presented stimuli. Three datasets were generated using the amplitude, time-frequency decomposition, and time-frequency connectivity metrics of P300 and LPP components to separate food and nonfood stimuli. We have implemented k-nearest neighbor (kNN), support vector machine (SVM), Linear Discriminant Analysis (LDA), Logistic Regression (LR), Bayesian classifier, decision tree (DT), and Multilayer Perceptron (MLP) classifiers on these datasets. Finally, the response to food-related stimuli in the hunger state is discriminated from nonfood with an accuracy value close to 78% for each dataset. The results obtained in this study motivate us to employ classifier algorithms using the features obtained from single-trial measurements in amplitude and time-frequency space instead of applying more complex ones like connectivity metrics.

Acute effects of high-intensity interval training and moderate-intensity continuous exercise on BDNF and irisin levels and neurocognitive performance in late middle-aged and older adults

The purposes of the present study were (1) to explore and compare the acute effects of high-intensity interval training (HIIT) and moderate-intensity continuous exercise (MICE) on neurocognitive performance and molecular biomarkers in late middle-aged and older adults, and (2) to examine the relationships of HIIT/MICE exercise-induced neurocognitive changes with changes in circulating irisin and BDNF levels elicited by different acute exercise modes. Using a within-subject design, twenty-one participants completed an acute bout of 30 min of HIIT, MICE, or a non-exercise-intervention (REST) session in a counterbalanced order. The neuropsychological [i.e., accuracy rate (AR) and reaction time (RT)] and neurophysiological [i.e., event-related potential (ERP) P3 latency and amplitude] indices were simultaneously measured when the participants performed a working memory task at baseline and after an intervention mode. Blood samples were also taken before and after the intervention mode. The results showed that, although ARs were significantly increased only via the MICE intervention mode, the acute HIIT and MICE interventions improved RT performance and increased ERP P3 amplitudes in the late middle-aged and older adults under consideration. Serum BDNF levels were significantly increased with the acute HIIT and MICE interventions, and significant irisin level increases were only observed following the HIIT intervention. However, changes in the levels of Irisin and BDNF pre- and post-intervention were not correlated with changes in neurocognitive performance, with the exception of the correlation between the changes in irisin levels and RTs with acute exercise in the MICE intervention mode. The present findings suggested similar beneficial effects on neurocognitive performance (i.e., RTs and ERP P3 amplitudes) and peripheral BDNF levels following MICE and HIIT interventions in the middle-aged and older adults. In terms of ARs and irisin, the two acute exercise modes appear to induce divergent effects. Irisin may play a potential facilitating role in the neuropsychological (e.g., RT) performance of working memory in such a group. However, the mechanisms remain to be determined.

Evaluating person-centered factors associated with brain-computer interface access to a commercial augmentative and alternative communication paradigm

Current BCI-AAC systems largely utilize custom-made software and displays that may be unfamiliar to AAC stakeholders. Further, there is limited information available exploring the heterogenous profiles of individuals who may use BCI-AAC. Therefore, in this study, we aimed to evaluate how individuals with amyotrophic lateral sclerosis (ALS) learned to control a motor-based BCI switch in a row-column AAC scanning pattern, and person-centered factors associated with BCI-AAC performance. Four individuals with ALS completed 12 BCI-AAC training sessions, and three individuals without neurological impairment completed 3 BCI-AAC training sessions. To assess person-centered factors associated with BCI-AAC performance, participants completed both initial and recurring assessment measures including levels of cognition, motor ability, fatigue, and motivation. Three of four participants demonstrated either BCI-AAC performance in the range of neurotypical peers, or an improving BCI-AAC learning trajectory. However, BCI-AAC learning trajectories were variable. Assessment measures revealed that two participants presented with a suspicion for cognitive impairment yet achieved the highest levels of BCI-AAC accuracy with their increased levels of performance being possibly supported by largely unimpaired motor skills. Motor-based BCI switch access to a commercial AAC row-column scanning may be feasible for individuals with ALS and possibly supported by timely intervention.

Effects of Acute Aerobic Exercise on Cognitive Flexibility Required During Task-Switching Paradigm

The present study aimed to investigate the effects of acute aerobic exercise on underlying neuronal activities associated with task-switching processes including both mixing and switch effects. A total of 29 healthy young adults (21.4 ± 1.2 years) participated in this study. The experiment consisted of an exercise and a rest condition. In the exercise condition, participants completed 30 min of self-paced motor-driven treadmill exercise at 70% intensity of maximum heart rate (HR_max). In the rest condition, participants rested quietly for 30 min. Both conditions were conducted on different days, and the order was counterbalanced across participants. Participants performed the task-switching paradigm (switching between two different tasks), after both exercise and rest conditions respectively. The P3 amplitude was smaller in the non-switch trial than the single trial only in the rest condition, but not in the exercise condition. In other words, more attentional resources were allocated to the non-switch trial requiring greater amounts of working memory following the exercise condition. Mixing and switch effects on the P3 component were influenced by acute aerobic exercise. This result suggests that acute aerobic exercise may serve to facilitate the flexibility of task-set reconfiguration and maintain the task set in working memory. Furthermore, during the switch trials, the P3 latency was shorter in the exercise condition than in the rest condition. This result is consistent with the findings of previous studies, indicating that cognitive processing speed is increased only during task conditions requiring greater amounts of executive control. Our study clearly indicates that acute aerobic exercise may facilitate cognitive flexibility as well as other executive functions (i.e., inhibitory control and working memory).

Distinctive Effects of Aerobic and Resistance Exercise Modes on Neurocognitive and Biochemical Changes in Individuals with Mild Cognitive Impairment

Background:

Decreased levels of the neuroprotective growth factors, low-grade inflammation, and reduced neurocognitive functions during aging are associated with neurodegenerative diseases, such as Alzheimer’s disease. Physical exercise modifies these disadvantageous phenomena while a sedentary lifestyle promotes them.

Purpose:

The purposes of the present study included investigating whether both aerobic and resistance exercise produce divergent effects on the neuroprotective growth factors, inflammatory cytokines, and neurocognitive performance, and further exploring whether changes in the levels of these molecular biomarkers are associated with alterations in neurocognitive performance.

Methods:

Fifty-five older adults with amnestic MCI (aMCI) were recruited and randomly assigned to an aerobic exercise (AE) group, a resistance exercise (RE) group, or a control group. The assessment included neurocognitive measures [e.g., behavior and event-related potential (ERP)] during a task-switching paradigm, as well as circulating neuroprotective growth factors (e.g., BDNF, IGF-1, VEGF, and FGF-2) and inflammatory cytokine (e.g., TNF-α, IL-1β, IL-6, IL-8, and IL-15) levels at baseline and after either a 16-week aerobic or resistance exercise intervention program or a control period.

Results:

Aerobic and resistance exercise could effectively partially facilitate neurocognitive performance [e.g., accuracy rates (ARs), reaction times during the heterogeneous condition, global switching cost, and ERP P3 amplitude] when the participants performed the task switching paradigm although the ERP P2 components and P3 latency could not be changed. In terms of the circulating molecular biomarkers, the 16-week exercise interventions did not change some parameters (e.g., leptin, VEGF, FGF-2, IL-1β, IL-6, and IL-8). However, the peripheral serum BDNF level was significantly increased, and the levels of insulin, TNF-α, and IL-15 levels were significantly decreased in the AE group, whereas the RE group showed significantly increased IGF-1 levels and decreased IL-15 levels. The relationships between the changes in neurocognitive performance (AR and P3 amplitudes) and the changes in the levels of neurotrophins (BDNF and IGF-1)/inflammatory cytokines (TNF-α) only approached significance.

Conclusion:

These findings suggested that in older adults with aMCI, not only aerobic but also resistance exercise is effective with regard to increasing neurotrophins, reducing some inflammatory cytokines, and facilitating neurocognitive performance. However, the aerobic and resistance exercise modes likely employed divergent molecular mechanisms on neurocognitive facilitation.

Food Cue Reactivity and the Brain-Heart Axis During Cognitive Stress Following Clinically Relevant Weight Loss

Successful weight loss maintainers are more vulnerable to stress induced eating. The aim of our study was to determine what effect an attention-demanding cognitive performance task had on brain-heart reactivity to visual food cues in women who maintained clinically relevant weight loss vs. women who had never weight cycled. A clinical weight loss group (CWL, n = 17) and a BMI-matched control group (CTL, n = 23) completed modified Stroop tasks that either included high calorie food pictures (Food Stroop) or excluded food cues (Office Stroop). ECG, breathing rate, and EEG were recorded. CWL participants: The Eating Restraint scores (Three Factor Eating Questionnaire) of the CWL participants correlated negatively with their heart rates recorded during the Food Stroop task (r = 0.62, p < 0.01). There was no such relationship in CTL participants. The P200 latencies in CWL participants evoked by the Stroop color-word cues at the C3 electrode were positively correlated to the log high frequency power in their cardiac spectrograms during the Food Stroop (r = 0.63, p < 0.02). There were no such relationships in the Office Stroop task nor in CTL participants. Combined Groups: Participants' heart rates were significantly lower (p < 0.05) and their RMSSD values and the log Total Power in their cardiac spectrograms were significantly greater during the Food Stroop vs. Office Stroop (p < 0.01, Bonferroni corrected). In conclusion Eating Restraint scores in CWL participants correlated with their Stroop heart rates, while the P200 latencies evoked by the Stroop cues correlated with the log high frequency power in their cardiac spectrograms (marker of cardiac vagal activation) during the Food Stroop task. This provides evidence that even 12 months after successful weight loss maintenance the cardiac ANS reactivity to food cues while completing a cognitive performance test was still different to that in individuals of normal weight who never weight cycled. Across all participants the cardiac ANS reactivity evoked by performing the Stroop task was lowered by food cues suggesting that the dampening effect of food cues on cardiac ANS reactivity may be one of the drivers of ‘stress induced' eating.

Differential Effects of Carbohydrates on Behavioral and Neuroelectric Indices of Selective Attention in Preadolescent Children

The importance of breakfast consumption for ideal cognitive performance has received much attention in recent years, although research on the topic has yielded mixed results. The present study utilized event-related brain potentials (ERPs) elicited during a modified flanker task to investigate the neuroelectric implications of receiving different mixed macronutrient beverages after an overnight fast. A repeated measures design was employed whereby preadolescent participants (9–10 years of age) completed cognitive testing while ERPs were collected during two non-consecutive testing sessions, one in which they received one of three treatment beverages consisting of mixed-macronutrient formulations (either Carbohydrate Blend, Sucrose, Maltodextrin) and the other in which they received a placebo drink containing Sucralose. Performance indices, ERPs, and blood glucose were recorded at three time points before the testing session and after the ingestion of each drink. While the behavioral performance indices and N2 results showed some evidence of glucose facilitation, the effects were small and selective. Participants who received the Maltodextrin treatment showed faster reaction times and more stable N2 amplitudes after ingesting the treatment beverage. The most robust effects were seen in the P3 amplitude measurement. Across the three drink groups, participants showed a marked amplitude increase over time after the placebo drink was ingested, although P3 amplitudes remained stable when a carbohydrate treatment drink was ingested. These effects were eliminated when changes in blood glucose were accounted for, suggesting that the neurolectric effects were directly related to glycemic change. These findings suggest that ingestion of carbohydrates after an overnight fast results in changes to the P3 amplitude of the ERP waveform elicited during an attentional inhibition task.

An acute bout of aerobic or strength exercise specifically modifies circulating exerkine levels and neurocognitive functions in elderly individuals with mild cognitive impairment

Although exercise is an effective way to decrease the risk of developing Alzheimer's disease, the biological basis for such benefits from the different exercise modes remains elusive. The present study thus aimed (i) to investigate the effects of acute aerobic or resistance exercise on neurocognitive performances and molecular markers when performing a cognitive task involving executive functioning in older adults with amnestic mild cognitive impairment (aMCI), and (ii) to explore relationships of acute exercise-induced neurocognitive changes with changes in circulating levels of neuroprotective growth factors (e.g., BDNF, IGF-1, VEGF, and FGF-2, collectively termed 'exerkines'), elicited by different acute exercise modes. Sixty-six older adults with aMCI were recruited and randomly assigned to an aerobic exercise (AE) group, a resistance exercise (RE) group, or a non-exercise-intervention (control) group. The behavioral [i.e., accuracy rate (AR) and reaction time (RT)] and electrophysiological [i.e., event-related potential (ERP) P3 latency and amplitude collected from the Fz, Cz, and Pz electrodes] indices were simultaneously measured when participants performed a Flanker task at baseline and after either an acute bout of 30 min of moderate-intensity AE, RE or a control period. Blood samples were taken at three time points, one at baseline (T1) and two after an acute exercise intervention (T2 and T3: before and after cognitive task test, respectively). The results showed that the acute AE and RE not only improved behavioral (i.e., RTs) performance but also increased the ERP P3 amplitudes in the older adults with aMCI. Serum FGF-2 levels did not change with acute aerobic or resistance exercise. However, an acute bout of aerobic exercise significantly increased serum levels of BDNF and IGF-1 and tended to increase serum levels of VEGF in elderly aMCI individuals. Acute resistance exercise increased only serum IGF-1 levels. However, the exercise-induced elevated levels of these molecular markers returned almost to baseline levels in T3 (about 20 min after acute exercise). In addition, changes in the levels of neurotrophic and angiogenic factors were not correlated with changes in RTs and P3 amplitudes. The present findings of changes in neuroprotective growth factors and neurocognitive performances through acute AE or RE suggest that molecular and neural prerequisites for exercise-dependent plasticity are preserved in elderly aMCI individuals. However, the distinct pattern of changes in circulating molecular biomarkers induced by two different exercise modes in aMCI elderly individuals and the potentially interactive mechanisms of the effects of BDNF, IGF-1, and VEGF on amyloid-β provide a basis for future long-term exercise intervention to investigate whether AE relative to RE might be more effective in prevention/treatment of an early stage neurodegenerative disease.

Neurophysiological Processing of an Emotional Task is Sensitive to Time-of-Day

Previous work from our laboratory has shown that a measure of attention to emotionally-charged stimuli, the late positive potential (LPP) event related potential (ERP), distinguished neutral from emotional pictures on a baseline day, but not after sleep deprivation. Here we sought to extend these findings and address the uncertainty about the effect of time-of-day on emotion processing by testing a morning group (8:00–10:00 a.m., n = 30) and an evening group (8:00–10:00 p.m., n = 30). We also examined the extent of diurnal changes in cortisol related to the emotion processing task. Results from this study mirrored those found after one night of sleep deprivation. Compared to the morning group, the LPP generated by the evening group (who had a greater homeostatic sleep drive) did not distinguish neutral from emotionally-charged stimuli. New to this study, we also found that there was a time-of-day effect on positive, but not negative pictures. While, as expected, cortisol levels were higher in the morning relative to the evening group, there was no relationship between cortisol and the LPP ERP emotion measure. In addition, neither time-of-day preference nor sleep quality was related to the LPP measure. These findings show that, similar to what occurs after sleep deprivation, increased sleep pressure throughout the day interferes with attention processing to emotional stimuli.

Circadian course of the P300 ERP in patients with amyotrophic lateral sclerosis - implications for brain-computer interfaces (BCI)

Background

Accidents or neurodegenerative diseases like amyotrophic lateral sclerosis (ALS) can lead to progressing, extensive, and complete paralysis leaving patients aware but unable to communicate (locked-in state). Brain-computer interfaces (BCI) based on electroencephalography represent an important approach to establish communication with these patients. The most common BCI for communication rely on the P300, a positive deflection arising in response to rare events. To foster broader application of BCIs for restoring lost function, also for end-users with impaired vision, we explored whether there were specific time windows during the day in which a P300 driven BCI should be preferably applied.

Methods

The present study investigated the influence of time of the day and modality (visual vs. auditory) on P300 amplitude and latency. A sample of 14 patients (end-users) with ALS and 14 healthy age matched volunteers participated in the study and P300 event-related potentials (ERP) were recorded at four different times (10, 12 am, 2, & 4 pm) during the day.

Results

Results indicated no differences in P300 amplitudes or latencies between groups (ALS patients v. healthy participants) or time of measurement. In the auditory condition, latencies were shorter and amplitudes smaller as compared to the visual condition.

Conclusion

Our findings suggest applicability of EEG/BCI sessions in patients with ALS throughout normal waking hours. Future studies using actual BCI systems are needed to generalize these findings with regard to BCI effectiveness/efficiency and other times of day.

Acute effects of BZP, TFMPP and the combination of BZP and TFMPP in comparison to dexamphetamine on an auditory oddball task using electroencephalography: a single-dose study

RATIONALE

Piperazine-based designer drugs such as benzylpiperazine (BZP) and trifluoromethylphenylpiperazine (TFMPP) have been marketed and sold as legal alternatives to dexamphetamine and 3,4-methylenedioxymethamphetamine (MDMA) until 2008 in New Zealand. When administered in combination, BZP + TFMPP have been reported to produce drug-drug synergism in rodents by stimulating the release of dopamine and serotonin.

OBJECTIVES

This study was to evaluate the acute event-related potential effects of BZP, TFMPP or the combination of BZP + TFMPP compared with dexamphetamine in young healthy male adults.

METHODS

A double-blind, randomised, placebo-controlled study investigated the effects of BZP, TFMPP, the combination of BZP + TFMPP, and dexamphetamine on the event-related potentials during an auditory oddball task. Healthy, right-handed males were given a single oral dose of either BZP (200 mg), TFMPP (60 mg), a combination of BZP + TFMPP (100/30 mg), dexamphetamine (20 mg) or placebo (lactose) and tested both before and 120 min after drug administration.

RESULTS

A single dose of either TMFPP (t = -2.29, p = 0.03) or dexamphetamine (t = -2.33, p = 0.02) significantly reduced the P300 amplitude. A similar trend was also found in BZP. In contrast, BZP and TFMPP in combination has no effect. Neither P300 latency nor the mean reaction time was affected by any of the drug treatments. In addition, neither the P100 nor the P200 component was significantly affected following any of the drug treatments.

CONCLUSIONS

A single oral dose of BZP or TFMPP, but not the combination of BZP/TFMPP, affected auditory sensory-evoked P300 potential in a manner similar to dexamphetamine.

P300 in individuals with sensorineural hearing loss

Introduction

Behavioral and electrophysiological auditory evaluations contribute to the understanding of the auditory system and of the process of intervention.

Objective

To study P300 in subjects with severe or profound sensorineural hearing loss.

Methods

This was a descriptive cross-sectional prospective study. It included 29 individuals of both genders with severe or profound sensorineural hearing loss without other type of disorders, aged 11 to 42 years; all were assessed by behavioral audiological evaluation and auditory evoked potentials.

Results

A recording of the P3 wave was obtained in 17 individuals, with a mean latency of 326.97 ms and mean amplitude of 3.76 V. There were significant differences in latency in relation to age and in amplitude according to degree of hearing loss. There was a statistically significant association of the P300 results with the degrees of hearing loss (p = 0.04), with the predominant auditory communication channels (p < 0.0001), and with time of hearing loss.

Conclusions

P300 can be recorded in individuals with severe and profound congenital sensorineural hearing loss; it may contribute to the understanding of cortical development and is a good predictor of the early intervention outcome.

Executive function and endocrinological responses to acute resistance exercise

This study had the following two aims: First, to explore the effects of acute resistance exercise (RE, i.e., using exercise machines to contract and stretch muscles) on behavioral and electrophysiological performance when performing a cognitive task involving executive functioning in young male adults; Second, to investigate the potential biochemical mechanisms of such facilitative effects using two neurotrophic factors [i.e., growth hormone (GH) and insulin-like growth factor-1 (IGF-1)] and the cortisol levels elicited by such an exercise intervention mode with two different exercise intensities. Sixty young male adults were recruited and randomly assigned to a high-intensity (HI) exercise group, moderate-intensity (MI) exercise group, and non-exercise-intervention (NEI) group. Blood samples were taken, and the behavioral and electrophysiological indices were simultaneously measured when individuals performed a Go/No-Go task combined with the Erikson Flanker paradigm at baseline and after either an acute bout of 30 min of moderate- or high-intensity RE or a control period. The results showed that the acute RE could not only benefit the subjects' behavioral (i.e., RTs and accuracy) performance, as found in previous studies, but also increase the P3 amplitude. Although the serum GH and IGF-1 levels were significantly increased via moderate or high intensity RE in both the MI and HI groups, the increased serum levels of neurotrophic factors were significantly decreased about 20 min after exercise. In addition, such changes were not correlated with the changes in cognitive (i.e., behavioral and electrophysiological) performance. In contrast, the serum levels of cortisol in the HI and MI groups were significantly lower after acute RE, and the changes in cortisol levels were significantly associated with the changes in electrophysiological (i.e., P3 amplitude) performance. The findings suggest the beneficial effects of acute RE on executive functioning could be due to changes in arousal, possibly modulated by the serum cortisol levels.

Impact of acute aerobic exercise and cardiorespiratory fitness on visuospatial attention performance and serum BDNF levels

The purpose of the current study was to explore various behavioral and neuroelectric indices after acute aerobic exercise in young adults with different cardiorespiratory fitness levels when performing a cognitive task, and also to gain a mechanistic understanding of the effects of such exercise using the brain-derived neurotrophic factor (BDNF) biochemical index. Sixty young adults were separated into one non-exercise-intervention and two exercise intervention (EI) (i.e., EIH: higher-fit and EIL: lower-fit) groups according to their maximal oxygen consumption. The participants' cognitive performances (i.e., behavioral and neuroelectric indices via an endogenous visuospatial attention task test) and serum BDNF levels were measured at baseline and after either an acute bout of 30min of moderate intensity aerobic exercise or a control period. Analyses of the results revealed that although acute aerobic exercise decreased reaction times (RTs) and increased the central Contingent Negative Variation (CNV) area in both EI groups, only the EIH group showed larger P3 amplitude and increased frontal CNV area after acute exercise. Elevated BDNF levels were shown after acute exercise for both EI groups, but this was not significantly correlated with changes in behavioral and neuroelectric performances for either group. These results suggest that both EI groups could gain response-related (i.e., RT and central CNV) benefits following a bout of moderate acute aerobic exercise. However, only higher-fit individuals could obtain particular cognition-process-related efficiency with regard to attentional resource allocation (i.e., P3 amplitude) and cognitive preparation processes (i.e., frontal CNV) after acute exercise, implying that the mechanisms underlying the effects of such exercise on neural functioning may be fitness dependent. However, the facilitating effects found in this work could not be attributed to the transient change in BDNF levels after acute exercise.

Aroma helps to preserve information processing resources of the brain in healthy subjects but not in temporal lobe epilepsy

PURPOSE

Inhalation of ylang-ylang aroma has been shown to reduce the auditory P300, an event-related potential thought to reflect higher-order processing. Because olfactory function is sometimes disturbed in temporal lobe epilepsy (TLE), the objective of the present study was to determine whether the effect of ylang-ylang aroma on the auditory P300 was impaired in patients with TLE.

METHOD

Fourteen subjects with TLE and 14 healthy controls participated in this study. Electroencephalograms were recorded during an auditory oddball task, and ylang-ylang aroma or odorless air was delivered through a mask.

RESULTS

We found that the ylang-ylang aroma prolonged the latencies of P300 in both groups. The ylang-ylang aroma significantly reduced the P300 amplitudes of healthy subjects as described previously. However, in TLE patients, the P300 was unaffected by the aroma.

CONCLUSION

The current results show that exposure to the ylang-ylang aroma reduced information processing resources in healthy subjects but had limited effects in patients with TLE. We suggest that impaired higher-order olfactory processing in TLE patients may inhibit the effects of the ylang-ylang aroma on the P300.

Effects of food energy on cognitive performance: no support from event-related potentials (yet?)

Several reviews of behavioural studies have concluded that some foods may have beneficial effects on cognitive performance. The present review summarises findings from studies using event-related potentials to investigate the food effects on brain activity underlying cognition. Despite initial positive indications from observational studies, subsequent studies with a within-subject design have not consistently confirmed these effects. This could be due to several factors, e.g. the use of attention tests (in contrast to memory tests employed in behavioural studies) and the lack of a control condition in some instances. Future studies could benefit from measuring cognitive performance with more difficult tests that tap into cognitive domains other than attention, using an appropriately controlled cross-over design, and a more systematic variation and complete description and characterisation of the food intervention.

Event-related variations in alpha band activity during an attentional task in preadolescents: Effects of morning nutrition

OBJECTIVE

Event-related desynchronization and synchronization (ERD/ERS) methodology was used to study interactions between nutrition, brain function, cognition and behavior in children who ate or skipped breakfast after overnight fasting.

METHODS

Healthy preadolescents performed a cued visual Go/No-Go RT task after overnight fasting (Phase 1) and again (Phase 2) after eating breakfast (n=30) or continuing to fast (n=30). ERS and ERD determinations (8-10, 10-12Hz; frontal, central, parietal, occipital sites) and measures of sleep (overnight actigraphy) and blood glucose (finger sticks) were obtained.

RESULTS

Feeding increased blood glucose, but the groups were similar in sleep amount and response accuracy. Between-phase comparisons showed slower RT and increased alpha synchronization in fasting subjects, but little change in those who ate breakfast. Phase 2 group differences emphasized greater frontal early ERS and late frontal-central ERD in Fed subjects.

CONCLUSIONS

In preadolescents a brief extension of overnight fasting resulted in significant changes in brain activity and behavior that were effectively countered by eating breakfast. Delaying breakfast until mid-morning appeared to have introduced fasting effects that attenuated responses in Fed subjects.

SIGNIFICANCE

These findings show the sensitivity of brain function and behavior to subtle variations in nutritional status and argue for greater consideration of nutritional variables in neurobehavioral studies.

The effect of the menstrual cycle on electrophysiological and behavioral measures of memory and mood

Event-related potentials (ERPs) were compared between the menses and ovulatory phase of the menstrual cycle in response to visually presented words, some of which were repeated as part of direct and indirect memory tasks. Twelve spontaneously cycling women were tested during the menses and ovulatory phases. For the direct task, participants had to discriminate between new words and those repeated after a mean of six trials. In the indirect task, subjects were required to discriminate between target and nontarget words. Some of the nontarget words were repeated after a mean of six trials. The ERP repetition effect mean amplitude was significantly greater in response to repeated words at both cycle phases but did not differ across the cycle. P300 amplitude was significantly greater during menses than the ovulatory phase. We conclude that context updating mechanisms as indexed by the P300 are sensitive to cyclic hormonal fluctuations.

Circadian rhythm and desensitization in chemosensory event-related potentials in response to odorous and painful stimuli

Olfactory (H2S) and trigeminal (CO2) event-related potentials (ERPs) were studied with respect to circadian rhythm and desensitization. ERPs, perceived odor and pain intensity, oral temperature, blood pressure, heart rate, nasal volume, and sleepiness were assessed four times at 04:00, 08:00, 12:00, 16:00, 20:00, and 24:00 hr in five young men. For each of these 24 sessions per participant, H2S and CO2 were each presented in 15 series of five stimuli with a 5-s ISI within and 30-s ISI between series. ERP amplitudes, but not latencies, followed a circadian rhythm (largest at 16:00 and smallest at 04:00) similar to oral temperature and opposite to sleepiness. Amplitudes decreased (most pronounced at 16:00 and 20:00) and latencies increased with repeated stimulation, suggesting desensitization, in accordance with odor and pain intensity. These findings imply that circadian rhythm and desensitization should be considered in chemosensory ERP studies.

Glucose and glucoregulatory modulation of memory scanning, event-related potentials and EEG in elderly subjects

Endogenous P300b event-related potential (ERP) and behavioral performance measures, extracted during a visual memory scanning task, and spectral indices of resting electroencephalographic (EEG) activity, were assessed in 12 healthy elderly adults before and after double-blind oral administration of a placebo or glucose (50 mg) beverage. Glucoregulation was estimated by deriving a recovery index to categorize subjects as having better (BR) or poorer (PR) blood glucose recovery. Although glucoregulatory status did not impact on EEG or task performance, PR subjects exhibited reduced P300b areas relative to BR subjects prior to beverage administration. Glucose did not alter P300b or memory scanning performance but, regardless of glucoregulatory status, it increased the EEG power in the slow alpha frequency band. The study results suggest that peripheral glucoregulation can influence neuroelectric measures of cognition and that the acute ingestion of glucose can modulate central arousal processes.

Tobacco smoking and event-related brain potentials in a Stroop task

Behavioral and event-related brain potential (ERP) measures were used to assess the effects of tobacco smoking on selective attention. Two groups of abstinent smokers performed a Stroop color-naming task. The display color of a stimulus word determined the correct response, whereas word meaning was irrelevant. Meaning was congruent, neutral, or incongruent with respect to color. After completing two blocks of trials under abstinent conditions, subjects received a 15-min break before performing two more blocks. Subjects in the Smoking group (N=12) smoked two cigarettes during the break. Matched Control subjects (N=12) did not smoke during the break. Typical Stroop effects were found, as reaction time (RT) was shortest to congruent words, intermediate to neutral words, and longest to incongruent words. Overall RT decreased after the break equally for the Smoking and Control groups, whereas the magnitude of the Stroop effect was unchanged for either group. P300 amplitude decreased after the break for the Smoking group but not for the Control group, which implied that smoking rather than practice produced component decline. Error rate and P300 latency did not change after the break for either group. The results suggest that tobacco smoking may decrease the availability of general attentional resources required to evaluate colored word stimuli, whereas the specific stimulus processing mechanisms responsible for the Stroop effect are relatively unaffected.

Diurnal variation in the P300 component of human cognitive event-related potential

Diurnal variation in the P300 component of the human cognitive event-related potential (ERP) was examined. The P300 component is considered to be a measure of neuroelectric activity related to cognitive functions such as attention allocation and information processing. Nine diurnally active healthy male subjects whose sleep-wake rhythms were synchronized prior to the experiment were studied. The P300 components oral temperature, heart rate, left- and right-hand grip strength, reaction time, subjectively rated sleepiness, attention level, and fatigue were measured at 08:00, 11:00, 14:00, 17:00, and 20:00. Significant diurnal variations in P300 latency, P300 amplitude, oral temperature, heart rate, left- and right-hand grip strength, subjectively rated sleepiness, and attention level were observed. The P300 latency at 08:00 was significantly longer than at 11:00, 17:00, and 20:00, while the P300 amplitude at 08:00 was significantly greater than at 17:00 and 20:00. The P300 latency was correlated positively with subjectively rated sleepiness and negatively correlated with subjectively rated attention level. These results suggest the existence of diurnal variation in human cognitive functions.

[The p300 cognitive event-related potential. II. Individual variability and clinical application in psychopathology]

The P300 wave is one of the cognitive components of the event-related potential (ERP) that is used to investigate the cognitive processes, and which can be used to study patient populations with a variety of psychiatric disorders. Its clinical utility has been increased by the identification of factors that contribute to the variability in its amplitude and latency. However, its value as a diagnostic index has not been entirely established. It can provide a useful recording of patients' information processing, and indicate the severity of the clinical state and its possible evolution. It can also assist in determining what therapeutic approach to adopt. In the present review, the findings in the literature concerning interindividual variation in the P300 wave are first described; several variables significantly influence the amplitude and latency of this wave, such as age, gender, intelligence and personality. Following this, the relevance of the data in the literature on the clinical applications of P300 in psychopathology is examined, including the studies undertaken to obtain an objective diagnostic index for mental disorders and also those carried out to assess the problems concerning the interpretation of information connected with the mental pathologies examined. P300-associated findings on dementia, schizophrenia, depression, alcoholism, drug addiction, anxiety disorders (panic disorder, obsessive-compulsive disorder, and post-traumatic stress syndrome) and on personality disorders (schizoid, antisocial or borderline personality disorder) have been examined in detail.

Sex effects on rate of change of P300 latency with age

OBJECTIVE

Recent MRI evidence suggests that neuroanatomic structures may change more rapidly with age in males compared with females. Sex differences for P300 latency were tested to determine whether similar results might appear for P300 latency, a neurophysiological measure sensitive to age and neurodegenerative processes.

METHODS

Auditory event related potentials (ERPs) were recorded using an auditory 'oddball' to elicit the N200 and P300 components. Forty-two male and 42 female healthy normal subjects (age range 15-85 years) were entered in this study. Both linear and curvilinear correlations of N200 and P300 latency/amplitude with age were tested.

RESULTS

The slope of P300 latency on age for males was steeper than for females at Pz in subjects who were 30 years of age and older. N200 and P300 latencies were inversely correlated with age in young adult males (<30 years old).

CONCLUSIONS

Males may experience more rapid change of P300 latency, but not amplitude, than females in middle to old age. Further research is required to determine whether those change reflects neural pathophysiology, or is mediated by such factors as neuroanatomic differences, body temperature, or mild auditory deficits.

On P300 measurement stability: habituation, intra-trial block variation, and ultradian rhythms

P300 event-related brain potentials (ERPs) were elicited using a simple discrimination task in which participants discriminated two different equiprobable visual stimuli with button-press responses (n = 20). A total of ten trial blocks were presented at 10-min intervals. P300 amplitude declined significantly, but peak latency did not change reliably across trial blocks. P300 amplitude demonstrated a reliable cyclical fluctuation across trial blocks, although P300 latency did not. Intra-trial block ERP variability was assessed by computing the correlation coefficients between the target and standard stimuli for amplitude and latency measures across participants within each trial block. P300 amplitude correlations were weakest at the Fz electrode, more strongly associated at Cz, and were most strongly correlated at Pz across trial blocks. P300 latency correlations were somewhat weaker and similar in strength across electrodes sites. The correlational patterns for both P300 amplitude and latency demonstrated reliable cyclical variation. The N100 component produced strong and consistent correlations for both amplitude and latency, whereas the P200 and N200 component measures evinced cyclical correlational patterns similar to the P300 across trial blocks. These results suggest that the stability of P300 and other component measures can vary appreciably within and across trial blocks in a manner that reflects ultradian variation in arousal level.

P300 and personality: an investigation with the Cloninger's model

The relationships between P300 and personality have been explored mainly in reference to the model of personality described by Eysenck because of its biological bases. Recently, Cloninger and his colleagues have proposed a model of personality based on four temperaments and three characters. The Temperament and Character Inventory (TCI) is a 226-item self-questionnaire developed to assess these seven dimensions of personality. In the present study, the relationships between these dimensions of personality and P300 have been investigated in 43 normal subjects. The results show that P300 amplitude is positively correlated with the novelty seeking dimension and negatively correlated with the harm avoidance dimension. In contrast, the other dimensions of the TCI were not related to P300 amplitude. Moreover, P300 latency and reaction time were not associated with the TCI dimensions of personality. This study confirms that personality is related to P300.

P300 habituation patterns: individual differences from ultradian rhythms

Event-related brain potentials (ERPs) were elicited with auditory stimuli from normal subjects every 10 min. for 10 successive trial blocks to assess ultradian influences on the P300 component. Based on a theoretical analysis of the underlying relationship between background EEG activity and P300 variability, subjects were divided into two groups according to whether P300 amplitude increased or decreased initially over trial blocks. P300 amplitude habituated across trial blocks. P300 latency produced systematic cyclical variation with approximately a 90-min. period that was opposite in phase for the different subject groups. The findings suggest that ultradian rhythms contribute to P300 latency variability. The implications of the results for P300 in applied settings are discussed.

Traumatic brain injury assessed with olfactory event-related brain potentials

Olfactory event-related potentials (OERPs) were evaluated to develop an objective, quantitative assessment of sensory and cognitive olfactory loss following traumatic brain injury (TBI). Subjects included 25 TBI patients and 25 age/gender-matched healthy controls. Following standard clinical evaluation of smell function, TBI patients were divided into three groups: 12 anosmics (loss of smell), 6 hyposmics (reduced smell), and 7 normosmics (normal smell). Cognitive ability was assessed using the Trail Making Test (A and B). OERPs were recorded monopolarly from midline electrode sites using an amyl acetate stimulus with a 60-second interstimulus interval; subjects estimated the magnitude of each odor stimulus. Anosmic TBI patients were also tested with OERPs using ammonia to ensure trigeminal nerve function. Amyl acetate OERPs demonstrated that the sensory N1 and P2 amplitudes and the cognitive P3 amplitudes were absent in the anosmic TBI patients and greatly reduced in the hyposmic and normosmic TBI patients compared to healthy controls. The trigeminal OERPs from the anosmic TBI patients were within normal limits, indicating that the primary olfactory deficits were objectively measured with OERPs. The relationship between the OERPs and neuropsychologic test performance supports the cognitive loss associated with TBI. The present study lends support to the utility of OERPs as an objective tool for measuring sensory and cognitive loss after traumatic brain injury.

EEG, ERPs and food consumption

Baseline electroencephalographic (EEG) and auditory event-related brain potentials (ERPs) were assessed in subjects before and after consuming food and under eyes open and closed recording conditions in an attempt to replicate and extend previous food--ERP effects. Subjects were assessed the morning after fasting from the previous night, before and after eating a standard lunch. Delta- band EEG spectral power decreased and theta- and early alpha-band frequency increased after food consumption. However, in contrast to previous reports, P300 amplitude was unaffected by food consumption and peak latency increased. The strength of the correlational association between background EEG activity and P300 measures decreased for the delta- and theta- bands, but increased for the early and late alpha- bands. The findings suggest that food consumption affects general arousal, rather than specific cognitive EEG or ERP factors and are discussed with respect to previous EEG-ERP findings on food intake.

P300 assessment of opiate and cocaine users: effects of detoxification and buprenorphine treatment

We assessed cognitive function following heroin and cocaine detoxification and investigated whether buprenorphine treatment improves the disruptive effects of detoxification. Three groups of male volunteers meeting DSM-III-R criteria for concurrent opiate and cocaine dependence were tested using an auditory oddball paradigm before and after detoxification, and again on the 15th day of either buprenorphine or placebo treatment. There were no significant differences in P300 amplitude, latency, or topographic distribution between drug-dependent subjects and controls on admission day. Following detoxification there was a significant decrease in P300 amplitude in the drug-dependent group at a time when self-reported signs of withdrawal were minimal. Buprenorphine treatment significantly reversed the P300 amplitude decrement following detoxification, whereas placebo-treated subjects continued to show depressed P300 amplitudes. These data demonstrate that buprenorphine treatment is effective in eliminating detoxification-induced impairments in one measure of cognitive ability.

Cognitive and biological determinants of P300: an integrative review

The P300 event-related brain potential (ERP) is thought to reflect neuroelectric activity related to cognitive processes such as attention allocation and activation of immediate memory. However, recent studies have provided evidence that the P300 also is influenced by biological processes such as fluctuations in the arousal state of subjects. The effects of natural (circadian, ultradian, seasonal, menstrual) and environmentally induced (exercise, fatigue, drugs) state variables on the P300 are reviewed. The findings suggest that these factors contribute to P300 measures and are discussed in terms of their theoretical and applied implications.

P300 is unaffected by glucose increase

The effects of glucose ingestion on the P3(00) event-related brain potential (ERP) were investigated by using a visual stimulus oddball paradigm in which subjects discriminated between checkerboard (target) and horizontal line (standard) stimuli. Subjects were assessed for six consecutive trial blocks that were spaced 20 min apart on two different occasions. For the glucose condition, an initial baseline trial block was recorded followed by ingestion of 100 mg of glucose and the remaining five trial blocks recorded. For the water condition, the same procedure was employed with water ingested instead of glucose. Blood glucose levels, heart rate, and body temperature measures also were obtained before each trial block. P3 amplitude and latency did not change across trial blocks for the glucose/water conditions. No glucose/water effects were observed for the N1, P2, or N2 components as well. Blood glucose levels and heart rate increased for the glucose but not the water condition; body temperature decreased with the ingestion of both glucose and water and then returned to baseline levels. These findings suggest that ERPs are not influenced by increases of blood glucose level and are discussed in the context of previous ERP studies employing glucose manipulations.

P300 from an auditory oddball task: inter-laboratory consistency

Event-related potentials (ERPs) were recorded from normal subjects for the purpose of evaluating measurement consistency among six laboratories located in different cities within the United States. At each laboratory location 15 male subjects were tested using a simple auditory stimulus discrimination task and identical electrophysiological equipment and recording methods. Assessment of the N1, P2, N2, and P3(00) potentials from both the target and standard stimuli resulted in no reliable differences among laboratories for component amplitudes, latencies, and scalp distributions. Quantitative evaluation of overall waveform and specific component morphology yielded good to excellent agreement across laboratories. The findings suggest that large-scale inter-laboratory human electrophysiological studies are feasible and may prove of value when using ERPs to evaluate cognitive function in humans.

P300 from amnesic patients with bilateral hippocampal lesions

P3(00) event-related brain potentials (ERPs) were recorded using auditory and visual stimuli from 5 amnesic patients with confirmed (n = 4) or suspected (n = 1) bilateral damage to the hippocampal formation without skull defects. Four normal control subjects were matched to each amnesic patient with respect to age, sex, education, and IQ subtest scores (n = 20 total controls). All 5 amnesic patients exhibited ERPs, and no reliable differences in P3 amplitude or latency could be detected between the patients and the control subjects in either modality. The findings indicate that the hippocampal formation does not contribute significantly to the scalp-recorded P3 from auditory and visual target stimuli, a conclusion also supported by additional recent findings from studies of patients with extensive bilateral medial temporal lobe damage studies. The significance of the P3 component for cognitive processing is discussed.

P300, habituation, and response mode

The P3(00) event-related brain potential (ERP) was elicited with an auditory discrimination paradigm under two response task conditions in which the probability of the target tone was always 0.20. Subjects either counted the occurrence of each target tone or pressed a button to the target in different conditions. No response was made to the standard tone. Consecutive blocks of trials were obtained to assess habituation of P3 amplitude. The count task demonstrated less habituation than the button-press task, with a strong interaction obtained between response mode and trial block for all electrode sites. The findings suggest that habituation of P3 amplitude is sensitive to the amount of attentional resources allocated to the processing of a target stimulus, with more resources required for a count task compared to fewer needed for a button-press response.

Time of day and semantic category effects on late components of the visual ERP

The N100, P200, N400 and P600 components of the visual event-related potential were recorded from 11 female subjects every 2 h from 09:00 to 21:00 hours using a semantic categorization task. All subjects scored as "Intermediate" or marginal "Evening" types on a Morningness-Eveningness questionnaire. Amplitude and latency of components, tympanic temperature, and performance measures for positive and negative category instances were assessed. Amplitude of P200 increased across the day. Amplitude of N400 was larger, and latency of P600 was longer, for negative category instances, but neither component varied with time of day. N100 was unaffected by time of day. The results suggest that previous reports of diurnal variations in visual N100-P200 were due to variations in P200 alone, and that diurnal variations in P200 may reflect diurnal variations in underlying arousal levels. In addition, overlap with P600 may have obscured time of day effects for N400.

P300 in multiple sclerosis: a preliminary report

The P300 component of the event-related brain potential (ERP) elicited with auditory stimuli and pattern-shift visual evoked potentials (VEPs) was obtained from 16 patients with multiple sclerosis (MS) and 16 matched control subjects. P300 latency was significantly longer and component amplitude relatively depressed in the MS patients compared to control subjects. The P100 potential of the VEP also was delayed for both full-field and half-field stimulus conditions in the patients compared to control subjects. The findings suggest that the P300 ERP may reflect the cognitive decline associated with MS.

P300 and individual differences: morning/evening activity preference, food, and time-of-day

To determine how individual differences stemming from activity preference, previous food intake, and time-of-day affect the P300 or P3 event-related brain potential (ERP), subject groups who varied orthogonally on these factors were compared using a simple auditory discrimination task to elicit the ERPs. Amplitude of the P3 component for morning-preferring subjects who had eaten recently was relatively large for both the morning and evening measurement time groups. P3 amplitude for the morning-preferring subjects who had not eaten recently was large for those measured in the morning and relatively small for those subjects measured in the evening. For evening-preferring subjects who had eaten recently, P3 amplitude was again relatively large for both the morning and evening measurement time groups. Evening-preferring subjects who had not eaten recently produced very small P3 components for those measured in the morning compared to the large components produced by those subjects measured in the evening. P3 latency tended to be longer for all subjects who had not eaten recently compared to those who had. The results suggest that the P3 component is sensitive to physiological and psychological changes originating from individual differences related to bodily state, which perhaps stems from individual differences in arousal level.