Electroencephalography and clinical neurophysiology最新文献

We present a new approach for non-invasive localization of focal epileptogenic discharges in patients considered for surgical treatment. EEG-triggered functional MR imaging (fMRI) and 3D EEG source localization were combined to map the primary electrical source with high spatial resolution. The method is illustrated by the case of a patient with medically intractable frontal lobe epilepsy. EEG obtained in the MRI system allowed triggering of the fMRI acquisition by the patient's habitual epileptogenic discharges. fMRI revealed multiple areas of signal enhancement. Three-dimensional EEG source localization identified the same active areas and provided evidence of onset in the left frontal lobe. Subsequent electrocorticography from subdural electrodes confirmed spike and seizure onset over this region. This approach, i.e. the combination of EEG-triggered fMRI and 3D EEG source analysis, represents a promising additional tool for presurgical epilepsy evaluation allowing precise non-invasive identification of the epileptic foci.

Between-electrode cross-covariances of delta (0–3 Hz)- and theta (4–7 Hz)-filtered high resolution EEG potentials related to preparation, initiation, and execution of human unilateral internally triggered one-digit movements were computed to investigate statistical dynamic coupling between these potentials. Significant (P<0.05, Bonferroni-corrected) cross-covariances were calculated between electrodes of lateral and median scalp regions. For both delta- and theta-bandpassed potentials, covariance modeling indicated a shifting functional coupling between contralateral and ipsilateral frontal-central-parietal scalp regions and between these two regions and the median frontal-central scalp region from the preparation to the execution of the movement (P<0.05). A maximum inward functional coupling of the contralateral with the ipsilateral frontal-central-parietal scalp region was modeled during the preparation and initiation of the movement, and a maximum outward functional coupling during the movement execution. Furthermore, for theta-bandpassed potentials, rapidly oscillating inward and outward relationships were modeled between the contralateral frontal-central-parietal scalp region and the median frontal-central scalp region across the preparation, initiation, and execution of the movement. We speculate that these cross-covariance relationships might reflect an oscillating dynamic functional coupling of primary sensorimotor and supplementary motor areas during the planning, starting, and performance of unilateral movement. The involvement of these cortical areas is supported by the observation that averaged spatially enhanced delta- and theta-bandpassed potentials were computed from the scalp regions where task-related electrical activation of primary sensorimotor areas and supplementary motor area was roughly represented.

Objectives: The ability to analyze patterns of recorded seizure activity is important in the localization and classification of seizures. Ictal evolution is typically a dynamic process with signals composed of multiple frequencies; this can limit or complicate methods of analysis. The recently-developed matching pursuit algorithm permits continuous time–frequency analyses, making it particularly appealing for application to these signals. The studies here represent the initial applications of this method to intracranial ictal recordings.

Methods: Mesial temporal onset partial seizures were recorded from 9 patients. The data were analyzed by the matching pursuit algorithm were continuous digitized single channel recordings from the depth electrode contact nearest the region of seizure onset. Time–frequency energy distributions were plotted for each seizure and correlated with the intracranial EEG recordings.

Results: Periods of seizure initiation, transitional rhythmic bursting activity, organized rhythmic bursting activity and intermittent bursting activity were identified. During periods of organized rhythmic bursting activity, all mesial temporal onset seizures analyzed had a maximum predominant frequency of 5.3–8.4 Hz with a monotonic decline in frequency over a period of less than 60 s. The matching pursuit method allowed for time–frequency decomposition of entire seizures.

Conclusions: The matching pursuit method is a valuable tool for time–frequency analyses of dynamic seizure activity. It is well suited for application to the non-stationary activity that typically characterizes seizure evolution. Time–frequency patterns of seizures originating from different brain regions can be compared using the matching pursuit method.

The present study shows that different neural activity during mental imagery and abstract mentation can be assigned to well-defined steps of the brain's information-processing. During randomized visual presentation of single, imagery-type and abstract-type words, 27 channel event-related potential (ERP) field maps were obtained from 25 subjects (sequence-divided into a first and second group for statistics). The brain field map series showed a sequence of typical map configurations that were quasi-stable for brief time periods (microstates). The microstates were concatenated by rapid map changes. As different map configurations must result from different spatial patterns of neural activity, each microstate represents different active neural networks. Accordingly, microstates are assumed to correspond to discrete steps of information-processing. Comparing microstate topographies (using centroids) between imagery- and abstract-type words, significantly different microstates were found in both subject groups at 286–354 ms where imagery-type words were more right-lateralized than abstract-type words, and at 550–606 ms and 606–666 ms where anterior-posterior differences occurred. We conclude that language-processing consists of several, well-defined steps and that the brain-states incorporating those steps are altered by the stimuli's capacities to generate mental imagery or abstract mentation in a state-dependent manner.

Objective: To describe the electroencephalographic findings in mucolipidosis type IV (ML IV), a lysosomal storage disease of unknown etiology characterized clinically by corneal clouding, retinal degeneration and severe psychomotor retardation. Most patients are of Ashkenazi–Jewish ancestry. The EEG findings in this syndrome have not been characterized.

Methods: We analyzed the EEGs of 10 patients with the diagnosis of ML IV, aged between of 2.5 and 21 years. All patients had 21 channel recordings in the international 10/20 system without sedation.

Results: Six of the 10 patients had slowing of the background in the theta frequency range, and 4 had excessive beta frequency activity without the administration of medications. Two patients were able to reach stage 2 sleep, and were noted to have both synchronous and asynchronous spindles and vertex waves. Of the 10 patients, 6 had epileptiform spikes, all of which were noted frequently. The location of the spikes varied, from the frontal and temporal regions to the central regions, although location was consistent in each patient. Only one patient with epileptiform spikes had a history of clinical seizures. None of the other patients had a history of seizures.

Conclusions: These findings imply that epileptiform discharges are common in patients with ML IV, but are infrequently associated with clinical seizures.

In a recent work, the calculation of the correlation dimension (CD) of the profiles of EEG slow-wave activity during sleep in 7 young subjects, allowed us to conclude that sleep-regulation might be considered a deterministic non-linear process with an average dimension above 3. In this paper we report the results of the calculation of the CD of EEG slow-wave activity in 20 normal subjects (children and young adults) who slept in the laboratory for 3 consecutive nights. The results confirm that it is possible to calculate the CD in most normal profiles (33 out of 40) and to discriminate between chaos and noise. The lower limit of CD was found as ranging between approximately 2.5 and 4.5, it did not show significant changes across consecutive nights in the same subject and did not seem to change significantly with age in children and young adults.

High spatial density recording and better topographic mapping algorithms have improved the spatial resolving power of the event-related potential (ERP), adding to its already excellent temporal resolution. This study used a 64 channel recording array and spherical spline interpolation to create topographic descriptions of the voltage and current density scalp distributions of the ERP in an auditory oddball paradigm. Frequent (standard) and infrequent (target) tones were presented at a rate of one every approximately 2500 ms to a group of 20 college undergraduates in passive listening and active (count the infrequent tones) task blocks. ANOVAs and topographic analyses were performed on the primary deflections in the `late' portion of the ERP: the P1, N1, P2, N2 and P3. A target minus standard difference wave was also created for each task. The difference wave contained a mismatch negativity (MMN), an N2b and a P3d. The MMN did not differ between the passive and active tasks and had a topography similar to the N1; also the difference wave P3d was topographically similar to the target P3. The N2b, which occurred only to targets in the active condition, and was the first index of target detection, had a scalp distribution consistent with generation in frontal and superior temporal cortex, suggesting activity in cortical areas of selective attention and auditory stimulus representation.