Joseph Ciorciari

Steady-State Visually Evoked Potential topography associated with a visual vigilance task

SummaryThis paper describes data which demonstrate a correlation between the magnitude of the Steady-State Visually Evoked Potential (SSVEP) and visual vigilance. The SSVEP was recorded from 64 scalp sites and elicited by a 13Hz uniform visual flicker presented continuously while subjects undertook a visual vigilance task. Fifteen right-handed males were required to view three times a series of 180 geometrical shapes comprising a sequence of 60 squares, 60 circles and a further 60 squares. Each viewing of the 180 shapes constituted a trial. Trials 1 and 2 were identical while trial 3 differed from the first two in that one of the circles was modified. Subjects were ignorant as to the location of the modified circle and prior to the third trial, were challenged to identify the modified circle. A comparison of trials 2 and 3 indicated that the appearance of the modified circle was associated with an attenuation of the SSVEP in the occipito/parietal region. The same comparison indicated a pronounced SSVEP attenuation in the centro/parietal region during the interval that subjects were anticipating the appearance of the modified circle. These results suggest a distinction between the cortical activation patterns occurring during different phases of a visual vigilance task.

Steady-state visually evoked potential topography during the Wisconsin card sorting test

This paper describes, for the first time, changes in steady-state visually evoked potential (SSVEP) topography associated with the performance of a computerised version of the Wisconsin card sort test (WCS). The SSVEP was recorded from 64 scalp sites and was elicited by a 13 Hz spatially uniform visual flicker presented continuously while 16 subjects performed the WCS. in the WCS, the sort criterion was automatically changed after subjects had sorted 10 cards correctly. Feedback on the 11th card always constituted a cue for a change in the sort criterion. It was found that in the 1-2 sec interval after the occurrence of the cue to change sort criterion, the prefrontal, central and right parieto-temporal regions showed a pronounced attenuation in SSVEP amplitude and an increase in phase lag. These changes, interpreted as an increase in regional cortical activity, are not apparent in the equivalent portions of the WCS when the sort criterion does not need to be changed. These results indicate that the levels of prefrontal and right parieto-temporal activity varied during the performance of the WCS, peaking at the times a change in sort criterion was required.

Acute neurocognitive effects of epigallocatechin gallate (EGCG)

Green tea is reported to have wide ranging beneficial health outcomes across epidemiological studies, which have been attributed to its flavonoid content. We investigated whether the flavonoid epigallocatechin gallate (EGCG) modulates brain activity and self-reported mood in a double-blind, placebo controlled crossover study. Participants completed baseline assessments of cognitive and cardiovascular functioning, mood and a resting state electroencephalogram (EEG) before and then 120 min following administration of 300 mg EGCG or matched placebo. EGCG administration was associated with a significant overall increase in alpha, beta and theta activity, also reflected in overall EEG activity, more dominant in midline frontal and central regions, specifically in the frontal gyrus and medial frontal gyrus. In comparison to placebo the EGCG treatment also increased self-rated calmness and reduced self rated stress. This pattern of results suggests that participants in the EGCG condition may have been in a more relaxed and attentive state after consuming EGCG. This is in keeping with the widespread consumption of green tea for its purported relaxing/refreshing properties. The modulation of brain function due to EGCG is deserving of further controlled human studies.

Dissociative Tendencies and Memory Performance on Directed-Forgetting Tasks

The current article presents two studies that aimed to replicate DePrince and Freyds (2001, 2004) studies demonstrating that high and low dissociators differentially recall neutral and trauma words under conditions of varying cognitive load. We did not find this effect. This lack of replication was apparent for both free recall and word recognition memory and in both studies. In effect, we found little evidence to support betrayal trauma theory, yet observed increased memory fallibility, as demonstrated by lower general recall and (in one study) commission errors, in high dissociators.

Changes in long term neural connectivity following psychological trauma

OBJECTIVE Neural connectivity differences between adults reporting childhood, adulthood or no history of trauma were examined. METHODS A total of 39 participants completed the Post-traumatic Stress Diagnostic Scale (PDS; Foa EB. Post-traumatic Stress Diagnostic Scale (PDS) Manual. Minneapolis, MN: National Computer Systems, 1995), a Word Memory Task (WMT; [McNally RJ, Metzger LJ, Lasko NB, Clancy SA, Pitman RK. Directed forgetting of trauma cues in adult survivors of childhood sexual abuse with and without post-traumatic stress disorder. J Abnorm Psychol 1998;107:596-601]) and EEG analysis. Intelligence was not assessed during the study. RESULTS As predicted, those with childhood trauma had significantly higher EEG coherence than those with either adulthood trauma or no past trauma. CONCLUSIONS Significant differences were observed over frontal, central, temporal and parietal areas. Evidence was found suggesting that childhood psychological trauma may have a lasting impact on neuronal connectivity. SIGNIFICANCE This is the first study to demonstrate the suspected long term effect of trauma over central, temporal and parietal areas. Long term neural correlates of childhood and adult trauma appear to suggest information processing differences--differences that may, eventually, lead to better interventions following trauma.

A High-Density EEG Investigation into Steady State Binaural Beat Stimulation

Binaural beats are an auditory phenomenon that has been suggested to alter physiological and cognitive processes including vigilance and brainwave entrainment. Some personality traits measured by the NEO Five Factor Model have been found to alter entrainment using pulsing light stimuli, but as yet no studies have examined if this occurs using steady state presentation of binaural beats for a relatively short presentation of two minutes. This study aimed to examine if binaural beat stimulation altered vigilance or cortical frequencies and if personality traits were involved. Thirty-one participants were played binaural beat stimuli designed to elicit a response at either the Theta (7 Hz) or Beta (16 Hz) frequency bands while undertaking a zero-back vigilance task. EEG was recorded from a high-density electrode cap. No significant differences were found in vigilance or cortical frequency power during binaural beat stimulation compared to a white noise control period. Furthermore, no significant relationships were detected between the above and the Big Five personality traits. This suggests a short presentation of steady state binaural beats are not sufficient to alter vigilance or entrain cortical frequencies at the two bands examined and that certain personality traits were not more susceptible than others.

Brain oscillatory activity during spatial navigation: Theta and gamma activity link medial temporal and parietal regions

Brain oscillatory correlates of spatial navigation were investigated using blind source separation (BSS) and standardized low resolution electromagnetic tomography (sLORETA) analyses of 62-channel EEG recordings. Twenty-five participants were instructed to navigate to distinct landmark buildings in a previously learned virtual reality town environment. Data from periods of navigation between landmarks were subject to BSS analyses to obtain source components. Two of these cortical sources were found to exhibit significant spectral power differences during navigation with respect to a resting eyes open condition and were subject to source localization using sLORETA. These two sources were localized as a right parietal component with gamma activation and a right medial-temporal–parietal component with activation in theta and gamma bandwidths. The parietal gamma activity was thought to reflect visuospatial processing associated with the task. The medial-temporal–parietal activity was thought to be more specific to the navigational processing, representing the integration of ego- and allo-centric representations of space required for successful navigation, suggesting theta and gamma oscillations may have a role in integrating information from parietal and medial-temporal regions. Theta activity on this medial-temporal–parietal source was positively correlated with more efficient navigation performance. Results are discussed in light of the depth and proposed closed field structure of the hippocampus and potential implications for scalp EEG data. The findings of the present study suggest that appropriate BSS methods are ideally suited to minimizing the effects of volume conduction in noninvasive recordings, allowing more accurate exploration of deep brain processes.

EEG coherence and dissociative Identity disorder: Comparing EEG coherence in DID hosts, alters, controls and acted alters

Abstract This is the first study to apply EEG coherence analysis to the study of Dissociative Identity Disorder (DID). EEG coherence is argued to be an objective measure of cortical connectivity. Five DID patients were compared to five controls, who were professional actors. Fifteen dissociated DID alter states were studied, as were 15 “alters” simulated by the actor control participants. Comparisons of EEG coherence were made between DID participants and controls. Significant differences in EEG coherence were found in comparing DID host and alter personalities, with coherence found to be lower in the alter personalities. No significant differences were found in comparing DID host personalities and controls. The acted alters matched for age and gender, showed no significant differences in coherence compared to DID alter personalities. The results indicate that EEG coherence may be an objective measure of the neuronal cortical connectivity associated with DID.

EEG Correlates of Virtual Reality Hypnosis

Abstract The study investigated hypnosis-related electroencephalographic (EEG) coherence and power spectra changes in high and low hypnotizables (Stanford Hypnotic Clinical Scale) induced by a virtual reality hypnosis (VRH) induction system. In this study, the EEG from 17 participants (Mean age = 21.35, SD = 1.58) were compared based on their hypnotizability score. The EEG recording associated with a 2-minute, eyes-closed baseline state was compared to the EEG during a hypnosis-related state. This novel induction system was able to produce EEG findings consistent with previous hypnosis literature. Interactions of significance were found with EEG beta coherence. The high susceptibility group (n = 7) showed decreased coherence, while the low susceptibility group (n = 10) demonstrated an increase in coherence between medial frontal and lateral left prefrontal sites. Methodological and efficacy issues are discussed.

Cognitive processes associated with compulsive buying behaviours and related EEG coherence

The behavioural and cognitive phenomena associated with Compulsive Buying (CB) have been investigated previously but the underlying neurophysiological cognitive process has received less attention. This study specifically investigated the electrophysiology of CB associated with executive processing and cue-reactivity in order to reveal differences in neural connectivity (EEG Coherence) and distinguish it from characteristics of addiction or mood disorder. Participants (N=24, M=25.38 yrs, S.D.=7.02 yrs) completed the Sensitivity to Punishment Sensitivity to Reward Questionnaire and a visual memory task associated with shopping items. Sensitivities to reward and punishment were examined with EEG coherence measures for preferred and non-preferred items and compared to CB psychometrics. Widespread EEG coherence differences were found in numerous regions, with an apparent left shifted lateralisation for preferred and right shifted lateralisation for non-preferred items. Different neurophysiological networks presented with CB phenomena, reflecting cue reactivity and episodic memory, from increased arousal and attachment to items.