Difficulty-related changes in inter-regional neural synchrony are dissociated between target and non-target processing

Information processing deficits in head injury assessed with ERPs reflecting early and late processing stages

Dissociating activation and integration of discourse referents: Evidence from ERPs and oscillations

Reduced P300 responses in criminal psychopaths during a visual oddball task

Previous studies have shown that the neural mechanisms underlying visual spatial attention rely on top-down control information from the frontal and parietal cortexes, which ultimately amplifies sensory processing of stimulus occurred at the attended location relative to those at unattended location. However, the modulations of effective brain networks in response to stimulus at attended and unattended location are not yet clear. In present study, we collected event-related potentials (ERPs) from 15 subjects during a visual spatial attention task, and a partial directed coherence (PDC) method was used to construct alpha-band effective brain networks of two conditions (targets at attended and nontargets at unattended location). Flow gain mapping, effective connectivity pattern, and graph measures including clustering coefficient (C), characteristic path length (L), global efficiency (Eglobal), and local efficiency (Elocal) were compared between two conditions. Flow gain mapping showed that the frontal region seemed to serve as the main source of information transmission in response to targets at attended location while the parietal region served as the main source in nontarget condition. Effective connectivity pattern indicated that in response to targets, there existed obvious top-down connections from the frontal, temporal, and parietal cortexes to the visual cortex compared with in response to nontargets. Graph theory analysis was used to quantify the topographical properties of the brain networks, and results revealed that in response to targets, the brain networks were characterized by significantly smaller characteristic path length and larger global efficiency than in response to nontargets. Our findings suggested that smaller characteristic path length and larger global efficiency could facilitate global integration of information and provide a substrate for more efficient perceptual processing of targets at attended location compared with processing of nontargets at ignored location, which revealed the neural mechanisms underlying visual spatial attention from the perspective of effective brain networks and graph theory for the first time and opened new vistas to interpret a cognitive process.

Objective: The aim of this study was to investigate the post-sauna residual consequences on brain neural network arousal, information processing and cognitive performance.Methods: Sixteen male subjects (24 ± 1 yr.) participated in the study. Whole-body hyperthermia was induced with Finnish sauna bathing. Before and 90 min after the sauna, resting electroencephalography (EEG) for spectral analysis and EEG event-related potentials (ERPs) during oddball tasks by two modalities (auditory and visual) were recorded.Results: Sauna bathing increased rectal temperature (Tre, 37.11 ± 0.33 °C to 38.84 ± 0.32 °C) and heart rate (HR, 65.63 ± 9.39 bpm to 151.0 ± 21.8 bpm). At 90 min after the sauna, Tre (37.00 ± 0.29 °C) and HR (72.1 ± 2.80 bpm) recovered to baseline levels. An increase was found in alpha power following sauna recovery. In the visual task modality, post-sauna recovery led to enhancement in the N2 amplitude with centroparietal distribution and decreases in P3 amplitude with distribution along the frontoparietal axis for executive motor–cognitive processing. In the auditory task modality, post-sauna recovery led to a decrease in P3 amplitude with a frontoparietal distribution and this change was accompanied by auditory N2 amplitude enhancement along the centroparietal distribution for non-target cognitive processing. No significant differences in task performance were found.Conclusion: Post-sauna recovery to normothermia led to enhanced resting neural network relaxation followed by increases in cognitive processing economy for the given oddball tasks. The auditory processing was not affected more by post-sauna recovery than was visual processing. Post-sauna recovery modifications in ERP components (stimulus processing) were insufficient to affect cognitive performance in both visual and auditory task modalities.

BackgroundWe used an automated Event Related Potentials (ERP) technique to compare ERP responses in amyloid positive and negative group of 75 patients with Mild Cognitive Impairment (MCI) and Dementia in a general neurological outpatient clinic. Over the years, research labs have repeatedly reported abnormal ERP markers in patients with MCI and dementia. Recent advances in technology have made ERP testing safe, easy to use and low cost, thus rendering it suitable for clinical use. Indeed, ERPs have become more routinely used in clinical assessment of neurological patients with cognitive changes. The possibility that ERP could help identify amyloid status in MCI and dementia patients adds to the potential clinical utility of these biomarkers.MethodPatients with a history of cognitive complains underwent an auditory oddball ERP paradigm in conjunction with routine neurological evaluation and imaging studies. Standard neuropsychological testing were available in most cases. Amyloid PET imaging was done as part of the IDEAS (Imaging Dementia ‐Evidence for Amyloid Scanning) study and provided the readings for amyloid load. ERP responses were analyzed in the context of beta amyloid readings, and in relation to the patients’ degree of cognitive deficits.ResultFinal data analysis will be presented at the time of the conferenceConclusionThe possibility that ERP could help identify amyloid status in MCI and dementia patients adds to the potential clinical utility of these biomarkers. possibility that ERP could help identify amyloid status in MCI and dementia patients adds to the potential clinical utility of these biomarkers.

An approach to single trial analysis of event-related potentials based on signal detection theory

Inducing Gamma Oscillations and Precise Spike Synchrony by Operant Conditioning via Brain-Machine Interface

Time effects on event-related brain potentials and vigilance performance

Objective To investigate the therapeutic effect of high-frequency repetitive transcranial magnetic stimulation (rTMS) on the mild cognitive impairment (MCI). Methods The study recruited 36 volunteers from Shijiazhuang City, who were diagnosed with MCI, and randomly divided into a treatment group (18) and a control group (18). Magnetic stimulation site was located in the dorsolateral prefrontal cortex with the frequency of 20 Hz, and 30 minutes (15 minutes on each side) each time, 5 times a week for 8 weeks. The control group received the same frequency with pseudo-stimulating coil, which produced vibration and sound, but didn′t generate a magnetic field.The MMSE was used to measure cognitive functioning, and event-related potentials (ERPs) in Fz, Cz and Pz were recorded using auditory oddball paradigm. Results (1) Compared with the control group, the patients′ count error rate in the experimental group was reduced after the intervention （F(1,31)=10.335, P 0.05). Conclusion The 8-week high-frequency repetitive transcranial magnetic stimulation treatment may improve the cognitive function in patients with MCI. Key words: Evoked potentials; Repetitive transcranial magnetic stimulation; Mild cognitive impairment

Skin sympathetic nerve activity and event-related potentials during auditory oddball paradigms

The primary aim of this study was to assess the effects of continuous, visual distracters that change systematically in complexity on P300 responses generated by an auditory oddball paradigm. In addition, the type of attention given to the visual distracter was explored. It was hypothesized that P300 amplitudes would be smallest, latencies longest, and changes in scalp distribution greatest when the most complex visual distracter requiring active attention was used versus the simple visual distracter requiring passive attention. Auditory-evoked P300s were collected in a sample of 10 healthy adults (mean age = 19.90 years) using a two-toned oddball paradigm (1500 Hz "frequent" tone, probability of occurrence: 0.88, and 2000 Hz "rare" target tone, probability of occurrence: 0.12). The oddball paradigm was paired with three different visual distracters, increasing in complexity. The simplest was a black fixation cross on a white background that participants were asked to view passively as they performed the auditory task of counting the target stimulus. The second visual distracter increased in complexity by introducing color and motion, as tan and medium pink squares were alternated on the screen. Participants had to actively attend to the alternating squares by looking for a hidden text message while simultaneously counting the target auditory stimulus. The third visual distracter condition increased complexity again by introducing not only color and motion, but also biological relevance as participants viewed a mouth producing nonsense syllables. Participants had to actively attend to the moving mouth to determine what it was producing while simultaneously counting the rare auditory stimulus. The two more complex visual distracters that required active attention caused reductions in auditory-evoked P300 amplitudes relative to those recorded while the participants passively viewed a fixation cross. P300 amplitudes were similar whether the two more complex visual distracters (squares versus mouth) were used. P300 latencies and scalp distribution were not influenced by complexity of, or type of attention to, the visual distracter. Regardless of distracter condition, P300 amplitude was significantly smaller and P300 latency was significantly shorter at frontal sites when compared with central and parietal sites. Findings indicate that endogenous attentional resource allocation abilities can be effectively monitored through the addition of a complex, visually distracting task to a "classic" auditory P300 paradigm. Biological relevance of the distracting task does not seem to have an effect on the event-related potentials measured in this study, suggesting other aspects, such as whether or not a stimulus contains color or motion, may determine the efficiency of the distracter. Last, by increasing the complexity of, and amount of attention to, a visual distracter while evoking P300s using auditory stimuli, the cognitive load for the normal, healthy listener seems to be increased and the response amplitude subsequently reduced. Evoking P300s under similar conditions from disordered populations with subtle cognitive deficits (e.g., mild traumatic brain injury) may allow for increased diagnostic specificity and sensitivity over that found for P300s to classic, auditory oddball paradigms alone.

To clarify the relationship between the hippocampus and the event-related responses in auditory information processing, we recorded event-related potentials (ERPs) and event-related magnetic fields (ERFs) associated with the auditory oddball paradigm in 12 patients with temporal lobe epilepsy before and after surgical treatment, and in eight age-matched healthy volunteers. Lesions in the patients were hippocampal sclerosis (8), cyst (2), cavernoma (1) and calcified arteriovenous malformation (1), all in the unilateral temporal lobe. Standard temporal lobectomy (8), selective amygdalohippocampectomy (2), selective hippocampectomy (1) and inferior lateral temporal resection (1) were carried out. ERPs were recorded in nine patients before surgery, in all 12 patients after surgery, and in all normal subjects. P300 was maximal at Pz in the patients both before and after surgery, and in normal subjects. The peak latency and amplitude of P300 measured at Pz in the patients either before or after surgery did not differ significantly from those in normal subjects. After surgery, only the amplitude of P300 over the anterior and mid-temporal area on the resected side was attenuated, while it was symmetric before surgery regardless of the side of epileptogenic focus. ERFs were recorded in three patients before surgery and in six normal subjects by using a whole-head neuromagnetometer. ERFs in response to the target stimuli at a latency of approximately 400 ms were recognized at the anterior, middle and posterior lateral channels on each hemisphere (M400). The latency and dipole moments for M400 did not differ significantly between the patients before surgery and the normal subjects. As a result of analysis using the time-varying multidipole model, three dipoles for M400 were estimated in two patients in whom ERFs were available before surgery for the analysis, and in normal subjects: mesial temporal area, superior temporal area and inferior parietal area on each hemisphere. After surgery, in four out of six patients in whom ERFs were recordable, M400 at the anterior temporal channels on the resected side disappeared, and the activity in the affected mesial temporal area was lost. In one patient who underwent inferior lateral temporal resection, M400 waveforms and its sources were preserved in all regions. There were no significant differences in the latency and dipole moments of the unaffected source of M400 before versus after surgery. These results suggest that the hippocampus contributes to the scalp-recorded P300 only at the corresponding anterior temporal region, and does not influence its general waveform and predominant distribution over the scalp.

Background and PurposeThe aim of this study was to identify the mechanism underlying the auditory discriminatory process reflected in mismatch negativity (MMN), using time-frequencyanalysis of single-trial event-related potentials (ERPs).MethodsTwo auditory tones of different probabilities (oddball paradigm) and the same probability (control paradigm) were used. The average dynamic changes in amplitude were evaluated, and the in-phase consistency of the EEG spectrum at each frequency and time window across trials, event-related spectral perturbations (ERSPs), and inter-trial phase coherence (ITC) were computed.ResultsSubtraction of the ERPs of standard stimuli from the ERPs of deviant stimuli revealed a clear MMN component in the oddball paradigm. However, no discernible MMN component was observed in the control paradigm. Statistical tests showed that in the oddball paradigm, deviant tones produced significant increases of theta ERSPs and ITC at around 250 ms as compared with the standard tone, while no significant difference between the two stimuli was observed in the control paradigm.ConclusionsOur results confirm that the auditory discriminatory process reflected in MMN is accompanied by phase resetting and power modulation at the theta frequency.

Previous studies have suggested the relation of particular frequency bands such as theta (4-8 Hz), alpha (8-14 Hz), beta (14-30 Hz), or gamma (>30 Hz) to cognitive functions. However, there has been controversy over which bands are specifically related to attention. We used the attention network test to separate three anatomically defined brain networks that carry out the functions of alerting, orienting, and executive control of attention. High-density scalp electrical recording was performed to record synchronous oscillatory activity and power spectrum analyses based on functional magnetic resonance imaging constrained dipole modeling were conducted for each attentional network. We found that each attentional network has a distinct set of oscillations related to its activity. The alerting network showed a specific decrease in theta-, alpha-, and beta-band activity 200-450 ms after a warning signal. The orienting network showed an increase in gamma-band activity at approximately 200 ms after a spatial cue, indicating the location of a target. The executive control network revealed a complex pattern when a target was surrounded with incongruent flankers compared with congruent flankers. There was an early (<400 ms) increase in gamma-band activity, a later (>400 ms) decrease in beta- and low gamma-band activity after the target onset, and a decrease of all frequency bands before response followed by an increase after the response. These data demonstrate that attention is not related to any single frequency band but that each network has a distinct oscillatory activity and time course.