EEG databases in research and clinical practice: current status and future directions.
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Database Management Systems↗
Biomedical subjects
Evian Gordon
Publications and source records attributed to Evian Gordon.
Face to face: visual scanpath evidence for abnormal processing of facial expressions in social phobia.
Cognitive models of social phobia propose that cognitive biases and fears regarding negative evaluation by others result in preferential attention to interpersonal sources of threat. These fears may account for the hypervigilance and avoidance of eye contact commonly reported by clinicians. This study provides the first objective examination of threat-related processing in social phobia. It was predicted that hyperscanning (hypervigilance) and eye avoidance would be most apparent in social phobia for overt expressions of threat. An infrared corneal reflection technique was used to record visual scanpaths in response to angry, sad, and happy vs. neutral facial expressions. Twenty-two subjects with social phobia were compared with age- and sex-matched normal controls. As predicted, social phobia subjects displayed hyperscanning, (increased scanpath length) and avoidance (reduced foveal fixations) of the eyes, particularly evident for angry faces. The results could not be explained by either medication or co-morbid depression. These findings are consistent with theories emphasising the role of information processing biases in social phobia, and show promise in the application to treatment evaluation in this disorder.
Adult↗
Mapping the time course of nonconscious and conscious perception of fear: an integration of central and peripheral measures.
Neuroimaging studies using backward masking suggest that conscious and nonconscious responses to complex signals of fear (facial expressions) occur via parallel cortical and subcortical circuits. Little is known, however, about the temporal differentiation of these responses. Psychophysics procedures were first used to determine objective thresholds for both nonconscious detection (face vs. blank screen) and discrimination (fear vs. neutral face) in a backward masking paradigm. Event-related potentials (ERPs) were then recorded (n = 20) using these thresholds. Ten blocks of masked fear and neutral faces were presented under each threshold condition. Simultaneously recorded skin conductance responses (SCRs) provided an independent index of stimulus perception. It was found that Fear stimuli evoked faster SCR rise times than did neutral stimuli across all conditions, indicating that emotional content influenced responses, regardless of awareness. In the first 400 msec of processing, ERPs dissociated the time course of conscious (enhanced N4 component) from nonconscious (enhanced N2 component) perception of fear, relative to neutral. Nonconscious detection of fear also elicited relatively faster P1 responses within 100 msec post-stimulus. The N2 may provide a temporal correlate of the initial sensory processing of salient facial configurations, which is enhanced when top-down cortical feedback is precluded. By contrast, the N4 may index the conscious integration of emotion stimuli in working memory, subserved by greater cortical engagement. Hum. Brain Mapping 21:64-74, 2004.
Adolescent↗
Sex differences in adult ADHD: a double dissociation in brain activity and autonomic arousal.
It is now estimated that up to one-half of attention deficit hyperactivity disorder (ADHD) children continue to manifest symptoms in adulthood. A striking discrepancy between juvenile and adult populations is the increasing proportion of females with an ADHD diagnosis. To shed light on the psychophysiological mechanisms underlying adult ADHD, electroencephalography (EEG) and electrodermal index of arousal (skin conductance level or SCL) measures were employed under conditions of eyes-closed resting activity. Quantitative EEG (QEEG) and SCL were measured simultaneously and continuously (2 min) in 35 ADHD adults (21 males, 14 females) and their age- and sex-matched controls. As a group ADHD adults were found to have EEG and SCL deviations consistent with previous adolescent and juvenile studies. However, adult males (but not females) with ADHD showed increased EEG theta activity. By contrast, adult females (but not males) with ADHD were autonomically hypo-aroused (decreased SCL). These results suggest that distinct mechanisms may underpin adult ADHD in males and females.
Adult↗
The dynamics of cortico-amygdala and autonomic activity over the experimental time course of fear perception.
Human neuroimaging studies implicate the amygdala, medial prefrontal and somatosensory-related cortices as key neural components in the perception of facial fear signals. Yet, their temporal sequence and interaction with autonomic arousal is not known. We used simultaneous functional magnetic resonance imaging (fMRI) and skin conductance response (SCR) recording in 22 healthy subjects to examine central and autonomic responses to repeated fearful expressions. Phasic SCRs followed a U-shape pattern across early, middle and late presentations of fear stimuli. fMRI data revealed a concomitant temporal sequence of preferential somatosensory insula, dorsomedial prefrontal cortex and left amygdala engagement. These findings suggest that sustained cortico-amygdala and autonomic responses may serve to prime the emotional content of fear signals, and differentiate them from initial stimulus novelty.
Adult↗
Spontaneous alpha peak frequency predicts working memory performance across the age span.
Working memory capacity has been consistently shown to decline with increasing age. Mechanisms underlying this decline are poorly understood. One index that has been found to predict performance on memory tests is alpha peak frequency, the peak of spectral alpha power of the EEG. Activity in the alpha band has been also associated with higher cognitive functions including attention and anticipation and has been shown to slow with age. Few studies, however, have examined whether there might be a relationship between WM decline and alpha peak frequency. The present study specifically investigated this relationship. Digit span was used as the index of WM function. The study made use of 550 normal subjects aged between 11 and 70 years in the Brain Resource International Database. The data were acquired from six laboratories located in the USA (2), Europe (2) and Australia (2). Forward and reverse digit span were found to be lower in older relative to younger age groups. Spontaneous alpha peak frequency slowed with age and more so at anterior than posterior sites. Frontal alpha peak frequency was found to be a significant predictor of reverse digit span, with each 1 Hz increase in frequency associated with a 0.21 increase in reverse digit span score and this was independent of age, indicating a positive relationship between alpha peak frequency and working memory performance.
Adolescent↗
Neurophysiologically-based mean-field modelling of tonic cortical activity in post-traumatic stress disorder (PTSD), schizophrenia, first episode schizophrenia and attention deficit hyperactivity disorder (ADHD).
A recently developed quantitative model of cortical activity is used that permits data comparison with experiment using a quantitative and standardized means. The model incorporates properties of neurophysiology including axonal transmission delays, synaptodendritic rates, range-dependent connectivities, excitatory and inhibitory neural populations, and intrathalamic, intracortical, corticocortical and corticothalamic pathways. This study tests the ability of the model to determine unique physiological properties in a number of different data sets varying in mean age and pathology. The model is used to fit individual electroencephalographic (EEG) spectra from post-traumatic stress disorder (PTSD), schizophrenia, first episode schizophrenia (FESz), attention deficit hyperactivity disorder (ADHD), and their age/sex matched controls. The results demonstrate that the model is able to distinguish each group in terms of a unique cluster of abnormal parameter deviations. The abnormal physiology inferred from these parameters is also consistent with known theoretical and experimental findings from each disorder. The model is also found to be sensitive to the effects of medication in the schizophrenia and FESz group, further supporting the validity of the model.
Adolescent↗
A temporal dissociation of subliminal versus supraliminal fear perception: an event-related potential study.
Current theories of emotion suggest that threat-related stimuli are first processed via an automatically engaged neural mechanism, which occurs outside conscious awareness. This mechanism operates in conjunction with a slower and more comprehensive process that allows a detailed evaluation of the potentially harmful stimulus (LeDoux, 1998). We drew on the Halgren and Marinkovic (1995) model to examine these processes using event-related potentials (ERPs) within a backward masking paradigm. Stimuli used were faces with fear and neutral (as baseline control) expressions, presented above (supraliminal) and below (subliminal) the threshold for conscious detection. ERP data revealed a double dissociation for the supraliminal versus subliminal perception of fear. In the subliminal condition, responses to the perception of fear stimuli were enhanced relative to neutral for the N2 "excitatory" component, which is thought to represent orienting and automatic aspects of face processing. By contrast, supraliminal perception of fear was associated with relatively enhanced responses for the late P3 "inhibitory" component, implicated in the integration of emotional processes. These findings provide evidence in support of Halgren and Marinkovic's temporal model of emotion processing, and indicate that the neural mechanisms for appraising signals of threat may be initiated, not only automatically, but also without the need for conscious detection of these signals.
Adolescent↗
Dysregulation of arousal and amygdala-prefrontal systems in paranoid schizophrenia.
OBJECTIVE: The authors investigated impaired differentiation of limbic-prefrontal systems by autonomic arousal in schizophrenia. It was predicted that paranoid patients would be distinguished by a disjunction of hyperarousal but reduced amygdala and medial prefrontal activity relative to both healthy comparison subjects and patients with nonparanoid schizophrenia. METHOD: Pictures depicting facial expressions of fear were presented to 27 schizophrenia patients (13 paranoid, 14 nonparanoid) and 22 matched healthy comparison subjects in an implicit perception task to evoke limbic activity. Simultaneous functional magnetic resonance imaging and skin conductance arousal recordings were acquired during presentation of faces expressing fear or neutral emotion. Responses to fear stimuli were further examined by contrasting those that were associated with a skin conductance response ("with arousal") and those that were not ("without arousal"). RESULTS: In the comparison subjects, arousal dissociated amygdala/medial prefrontal ("visceral") networks and hippocampus/lateral prefrontal ("context") networks for fear perception. Excessive arousal responses were elicited in the schizophrenia subjects, but there was an associated reduction in amygdala/medial prefrontal activity. This disjunction was pronounced in paranoid patients relative to both healthy subjects and nonparanoid patients. Paranoid patients also showed a relatively greater prefrontal deficit for "without-arousal" responses. CONCLUSIONS: This is the first study to reveal a functional disconnection in autonomic and central systems for processing threat-related signals in patients with paranoid schizophrenia. Paranoid cognition may reflect an internally generated cycle of misattribution regarding incoming fear signals due to a breakdown in the regulation of these systems.
Adult↗
Sex differences in functional connectivity in first-episode and chronic schizophrenia patients.
OBJECTIVE: There has been consistent evidence for a lower incidence and milder course of schizophrenia in women, yet there have been very few investigations of sex differences in brain function in this disorder. This study used a new high-temporal-resolution measure of functional brain connectivity to test the prediction that female patients would show relatively greater inter- and intrahemispheric connectivity than male patients, particularly in the early stage of schizophrenia. METHOD: Forty patients with chronic schizophrenia (20 women and 20 men) and 24 patients with first-episode schizophrenia (12 women and 12 men) and their respective matched comparison groups completed a conventional auditory oddball task. Phase synchronous gamma (40 Hz) activity was extracted from EEG recording during the task and time-locked to the oddball (target) stimuli. RESULTS: Chronic schizophrenia subjects showed a reduction in global functional connectivity (lower gamma phase synchrony) relative to their matched healthy subjects. Unexpectedly, this reduction was most apparent in female patients. By contrast, while first-episode patients showed a general reduction in the speed of frontal connectivity, the speed of global connectivity was relatively faster in female patients. CONCLUSIONS: This is the first study to investigate sex differences in schizophrenia that used the functional connectivity measure of gamma phase synchrony. The results suggest that in female patients with schizophrenia, additional breakdowns in brain network connectivity may develop with illness chronicity.
Adult↗
Defining the temporal threshold for ocular fixation in free-viewing visuocognitive tasks.
Patterns of ocular fixation in free-viewing tasks reflect aspects of visual attention and cognition. To quantify these patterns, fixations must be identified in raw eye movement data by applying explicit spatial and temporal thresholds. A temporal threshold of 200 ms is commonly used in clinical visuocognitive research, despite having been originally derived from a study of eye movements in reading. We systematically explored temporal fixation thresholds below 200 ms, using biologically relevant (human face) and abstract (complex geometric) stimuli. Short fixations (<200 ms) significantly altered spatiotemporal patterns of fixation for both the face and geometric stimuli, by increasing the number of fixations and the scanpath length. A threshold of 100 ms was found to discriminate fixations from other oculomotor activity effectively, and was consistent with current physiological and visuocognitive models. Statistical examination of fixation duration data for each subject suggested the median was a less biased and more robust measure of central tendency than the mean.
Adult↗
Emotion perception in schizophrenia: an eye movement study comparing the effectiveness of risperidone vs. haloperidol.
We used a psychophysiological marker of visual attention (the visual scanpath) to investigate the effects of atypical (risperidone) vs. typical (haloperidol) antipsychotic medication on facial emotion perception in schizophrenia (n=28) and healthy control (n=28) groups. Of the schizophrenia subjects, 15 were prescribed risperidone. Visual scanpaths to 'happy', 'sad' and 'neutral' faces were recorded using video-oculography, and concurrent emotion-recognition accuracy was assessed using multiple-option tasks. Compared to control subjects, both schizophrenia subgroups showed a restriction in visual scanning (reduced total fixation number and decreased scanpath length). Haloperidol-treated schizophrenia subjects exhibited an additional and consistent pattern of reduced attention (fixation) to salient features for neutral and happy. By contrast, risperidone-treated subjects showed a relatively greater attention to salient features for these expressions, in which they did not differ from controls. Recognition accuracy for happy and neutral showed a similar lack of impairment. These findings suggest that risperidone may play a specific role in schizophrenia in the ability to attend to salient features, and to integrate this information into an accurate percept for neutral and positive expressions in particular.
Adult↗
Processing angry and neutral faces in post-traumatic stress disorder: an event-related potentials study.
This study examined evoked response potentials (ERPs) to angry and neutral faces in 15 individuals with post-traumatic stress disorder (PTSD) and 15 age and sex-matched controls over temporal (T5,T6) and occipital (O1,O2) regions. Twenty faces with an angry expression were alternated with 20 faces with a neutral emotional expression. There were significantly larger early negative (N110) and late negative (N650) ERP components in controls to the angry compared to the neutral faces. The PTSD group did not display ERP differences between angry and neutral faces, and the amplitude of their negative waveforms were reduced relative to controls. These findings may reflect adaptive, rapid responding to potential threat in the controls, and a reduced capacity to discriminate between non-threat and generalized threat stimuli in PTSD.
Adult↗
Electrodermal responsivity distinguishes ERP activity and symptom profile in schizophrenia.
BACKGROUND: Traditional averaging of late component Event Related Potentials (ERPs) might obscure important psychophysiological subprocesses underlying schizophrenia disturbances in cognitive functioning. One such subprocess could be the active orientation of attention to significant or novel stimuli. In this study, we used skin conductance responses (SCRs) to index orienting responses (ORs). ERP activity was examined in relation to concomitant ORs in a schizophrenia and nonpsychiatric control group. Schizophrenia responses were considered with respect to the Reality Distortion, Disorganisation and Psychomotor Poverty syndromes. METHOD: Forty schizophrenia and 40 age and sex matched control subjects were tested. The three schizophrenia syndromes were derived from a principal component analysis of Positive and Negative Syndrome Scale (PANSS) ratings. Auditory ERPs (N100, N200, P200, P300) were elicited using a conventional auditory oddball paradigm, and electrodermal SCR data were acquired simultaneously. RESULTS: ERP data were sub-averaged according to the presence/absence of an OR. For both 'with-' and 'without-OR' ERPs, schizophrenia subjects as a group showed reduced N100 (associated with vigilance level) and N200 (associated with response selection) amplitude, and for with-OR responses, they showed an additional reduction in P300 (context processing). Concerning schizophrenia syndromes, Reality Distortion was related primarily to frontal disturbances (earlier N100/N200 latency and decreased P200/P300 amplitude), and Psychomotor Poverty to a generally delayed P300 latency. Similarly delayed P300 in Disorganisation was explained by medication effects. There were no associations with syndromes for without-OR ERPs. CONCLUSION: These results suggest that schizophrenia syndromes are dissociated with regard to both the direction and nature of speed of information processing disturbances, in relation to task-relevant information that produces active orientation.
Adolescent↗
Synchronous gamma activity: a review and contribution to an integrative neuroscience model of schizophrenia.
Synchronous high frequency (Gamma band) activity has been proposed as a candidate mechanism for the integration or 'binding' of distributed brain activities. Since the first descriptions of schizophrenia, attempts to characterize this disorder have focused on disturbances in such integrative processing. Here, we review both micro- and macroscopic neuroscience research into Gamma synchrony, and its application to understanding schizophrenia. The review encompasses evidence from both animal and human studies for the functional significance of Gamma activity, the association between Gamma dysfunction and information processing disturbances, and the relevance of specific Gamma dysfunctions to the integration and extension of previous disconnection models of schizophrenia. Attention is given to the relationship between Gamma activity and the heterogeneous symptoms of schizophrenia. Existing studies show that measures of Gamma activity have the potential to explain far more of the variance in schizophrenia performance than previous neurophysiological measures. It is concluded that measures of Gamma synchrony offer a valuable window into the core integrative disturbance in schizophrenia cognition.
Action Potentials↗
Social phobics do not see eye to eye: a visual scanpath study of emotional expression processing.
Clinical observation suggests that social phobia is characterised by eye avoidance in social interaction, reflecting an exaggerated social sensitivity. These reports are consistent with cognitive models of social phobia that emphasize the role of interpersonal processing biases. Yet, these observations have not been verified empirically, nor has the psychophysiological basis of eye avoidance been examined. This is the first study to use an objective psychophysiological marker of visual attention (the visual scanpath) to examine directly how social phobia subjects process interpersonal (facial expression) stimuli. An infra-red corneal reflection technique was used to record visual scanpaths in response to neutral, happy and sad face stimuli in 15 subjects with social phobia, and 15 age and sex-matched normal controls. The social phobia subjects showed an avoidance of facial features, particularly the eyes, but extensive scanning of non-features, compared with the controls. These findings suggest that attentional strategies for the active avoidance of salient facial features are an important marker of interpersonal cues in social phobia. Visual scanpath evidence may, therefore, have important implications for clinical intervention.
Adult↗
Integrative neuroscience.
A fundamental impediment to an "Integrative Neuroscience" is the sense that scientists building models at one particular scale often see that scale as the epicentre of all brain function. This fragmentation has begun to change in a very distinctive way. Multidisciplinary efforts have provided the impetus to break down the boundaries and encourage a freer exchange of information across disciplines and scales. Despite huge deficits of knowledge, sufficient facts about the brain already exist, for an Integrative Neuroscience to begin to lift us clear of the jungle of detail, and shed light upon the workings of the brain as a system. Integrations of brain theory can be tested using judicious paradigm designs and measurement of temporospatial activity reflected in brain imaging technologies. However, to test realistically these new hypotheses requires consistent findings of the normative variability in very large numbers of control subjects, coupled with high sensitivity and specificity of findings in psychiatric disorders. Most importantly, these findings need to be analyzed and modeled with respect to the fundamental mechanisms underlying these measures. Without this convergence of theory, databases, and methodology (including across scale physiologically realistic numerical models), the clinical utility of brain imaging technologies in psychiatry will be significantly impeded. The examples provided in this paper of integration of theory, temporospatial integration of neuroimaging technologies, and a numerical simulation of brain function, bear testimony to the ongoing conversion of an Integrative Neuroscience from an exemplar status into reality.
Animals↗
"Gamma (40 Hz) phase synchronicity" and symptom dimensions in schizophrenia.
INTRODUCTION: The failure of integrative brain function is a fundamental characteristic of schizophrenia. Synchronous Gamma (40 Hz) activity, proposed as a candidate mechanism underlying the integration ("binding") of distributed brain activities, may provide a direct window into schizophrenic disintegration. METHODS: 40 schizophrenia and 40 age/gender-matched control subjects participated in an auditory oddball paradigm. We examined both early (Gamma 1) and later Gamma (Gamma 2) phase synchrony to target stimuli. Factor analysis scores were used to examine the associations between Gamma synchrony and three syndromes (Psychomotor Poverty, Reality Distortion, and Disorganisation). RESULTS: Multiple analyses of variance revealed an overall decrease in frontal and left hemisphere Gamma synchrony, but increased posterior Gamma 2 synchrony in schizophrenia compared to controls. Schizophrenia syndromes were differentiated by distinct patterns of Gamma disturbances: Psychomotor Poverty showed decreased left hemisphere synchrony; Reality Distortion was associated with increased right synchrony; Disorganisation showed a widespread enhancement with a delay in frontal Gamma synchrony. CONCLUSIONS: These findings are consistent with previous evidence for left hemisphere and frontal disturbances in the schizophrenia group. However, the syndrome results point to more distinctive patterns of dysregulation in network integration: widespread and excessive in Disorganisation, localised and enhanced in Reality Distortion, versus localised and diminished in Psychomotor Poverty.
Journal Article↗