Methods for examining electrophysiological coherence in epileptic networks.

Epilepsy may reflect a focal abnormality of cerebral tissue, but the generation of seizures typically involves propagation of abnormal activity through cerebral networks. We examined epileptiform discharges (spikes) with dense array electroencephalography (dEEG) in five patients to search for the possible engagement of pathological networks. Source analysis was conducted with individual electrical head models for each patient, including sensor position measurement for registration with MRI with geodesic photogrammetry; tissue segmentation and skull conductivity modeling with an atlas skull warped to each patient's MRI; cortical surface extraction and tessellation into 1 cm(2) equivalent dipole patches; inverse source estimation with either minimum norm or cortical surface Laplacian constraints; and spectral coherence computed among equivalent dipoles aggregated within Brodmann areas with 1 Hz resolution from 1 to 70 Hz. These analyses revealed characteristic source coherence patterns in each patient during the pre-spike, spike, and post-spike intervals. For one patient with both spikes and seizure onset localized to a single temporal lobe, we observed a cluster of apparently abnormal coherences over the involved temporal lobe. For the other patients, there were apparently characteristic coherence patterns associated with the discharges, and in some cases these appeared to reflect abnormal temporal lobe synchronization, but the coherence patterns for these patients were not easily related to an unequivocal epileptogenic zone. In contrast, simple localization of the site of onset of the spike discharge, and/or the site of onset of the seizure, with non-invasive 256 dEEG was useful in predicting the characteristic site of seizure onset for those cases that were verified by intracranial EEG and/or by surgical outcome.

Attention network performance and psychopathic symptoms in early adolescence: an ERP study.

Reaction time (RT) and event-related potential (ERP) measures were used to examine the relationships between psychopathic symptoms and three major attention networks (alerting, orienting, and executive attention) among a community sample of youth. Antisocial Process Screening Device (APSD; Frick and Hare 2001) total and subscale scores were negatively correlated with ERP measures of attentional alerting, indicating that youth with psychopathic symptoms had difficulty using warning cues to prepare for upcoming targets. APSD total scores were not related to performance on measures of orienting or executive attention, although weaker executive attention was found among youth with higher scores on the Impulsivity subscale. These findings support attention-based models of psychopathy and provide evidence of specific deficits in attentional alerting among youth with psychopathic traits. Deficiencies in attentional alerting may be related to noradrenergic functioning and may have cascading effects on higher order cognitive and affective processing.

Frontolimbic activity in a frustrating task: covariation between patterns of coping and individual differences in externalizing and internalizing symptoms.

Many problem behaviors in youth have been attributed to maladaptive self-regulation in response to frustration. Frontolimbic networks that promote flexible as well as over- and undercontrolled regulation could provide evidence linking cortical mechanisms of self-regulation to the development of internalizing or externalizing symptomology. Specifically, ineffective dorsally mediated inhibitory control may be associated with rule-breaking and substance use behaviors, whereas overengagement of ventral limbic systems responsible for self-monitoring of errors may increase risk of developing anxious and depressed symptomology. In this study, a sample of 9- to 13-year-old children were presented with an emotional go/no-go task. Event-related potentials were used to identify differences in cortical mechanisms related to inhibitory control (indexed with the stimulus-locked medial frontal negativity) and self-monitoring (indexed with the error-related negativity). These measurements were then related to externalizing and internalizing behaviors. As predicted, externalizing problems were associated with smaller medial frontal negativity amplitudes, which indicate undercontrolled self-regulation and poor dorsal mediation of actions. Internalizing symptoms were related to larger error-related negativity amplitudes, demonstrating overregulation and overengagement of ventral limbic systems. These findings suggest that the use of event-related potential methodology with paradigms that elicit cognition-emotion can provide insight into the neural mechanisms of regulatory deficits that result in problem behaviors in youth.