Eye movements, eye blinks, cardiac signals, muscle noise, and line noise present serious problems for electroencephalographic (EEG) interpretation and analysis when rejecting contaminated EEG segments results in an unacceptable data loss. Many methods have been proposed to remove artifacts from EEG recordings, especially those arising from eye movements and blinks. Often regression in the time or frequency domain is performed on parallel EEG and electrooculographic (EOG) recordings to derive parameters characterizing the appearance and spread of EOG artifacts in the EEG channels. Because EEG and ocular activity mix bidirectionally, regressing out eye artifacts inevitably involves subtracting relevant EEG signals from each record as well. Regression methods become even more problematic when a good regressing channel is not available for each artifact source, as in the case of muscle artifacts. Use of principal component analysis (PCA) has been proposed to remove eye artifacts from multichannel EEG. However, PCA cannot completely separate eye artifacts from brain signals, especially when they have comparable amplitudes. Here, we propose a new and generally applicable method for removing a wide variety of artifacts from EEG records based on blind source separation by independent component analysis (ICA). Our results on EEG data collected from normal and autistic subjects show that ICA can effectively detect, separate, and remove contamination from a wide variety of artifactual sources in EEG records with results comparing favorably with those obtained using regression and PCA methods. ICA can also be used to analyze blink‐related brain activity.

Objective: To investigate the relationship between white matter tract integrity and language and memory performances in patients with temporal lobe epilepsy (TLE). Results: Increases in MD of the left UF, PHC, and IFOF were associated with poorer verbal memory in TLE, as were bilateral increases in MD of the AF, and decreases in FA of the right AF. Increased MD of the AF and UF, and decreased FA of the AF, UF, and left IFOF were related to naming performances. No correlations were found between DTI measures and nonverbal memory or fluency in TLE. Regression analyses revealed that several fibers, including the AF, UF, and IFOF, independently predicted cognitive performances after controlling for HV. Methods Conclusions:The results suggest that structural compromise to multiple fiber tracts is associated with memory and language impairments in patients with temporal lobe epilepsy. Furthermore, we provide initial evidence that diffusion tensor imaging tractography may provide clinically unique information for predicting neuropsychological status in patients with epilepsy. Neurology ® 2008;71:1869-1876 GLOSSARY AF ϭ arcuate fasciculus; BNT ϭ Boston Naming Test; CST ϭ corticospinal tract; DTI ϭ diffusion tensor imaging; FA ϭ fractional anisotropy; FORX ϭ fornix; HV ϭ hippocampal volume; ICHV ϭ intracranial-adjusted HV; IFOF ϭ inferior frontooccipital fasciculus; LM ϭ Logical Memory; MD ϭ mean diffusivity; MTS ϭ mesial temporal sclerosis; PHC ϭ parahippocampal cingulum; TLE ϭ temporal lobe epilepsy; UF ϭ uncinate fasciculus; WMS-III ϭ Wechsler Memory Scale-Third Edition.Global and lobar white matter atrophy has been reported in patients with temporal lobe epilepsy (TLE), 1,2 and an association between global white matter volume loss and generalized cognitive dysfunction has been described.2 However, the relationships among local white matter changes and cognitive impairments in TLE have not been established. Diffusion-tensor imaging (DTI) is a relatively new MRI technique for investigating white matter microstructure by measuring the relative motility of water within a voxel (mean diffusivity [MD]) and its directionality (fractional anisotropy [FA]).3,4 Higher MD and lower FA values are thought to reflect factors such as demyelination and axonal injury that are important for understanding neurologic disease.5 DTI tractography is an extension of DTI that provides an in vivo method of quantifying and visualizing the integrity of Editorial, page 1854

No abstract

Amnesic patients often show improved performance when stimuli are repeated, even in the absence of conscious memory for those stimuli. Although these performance changes are typically attributed to perceptual or motor systems, in some cases they may be related to basic language processing. We examined two neurophysiological measures that vary with word repetition in 12 amnesic patients and 12 control subjects: (i) a late positive component of the event-related potential (ERP) linked to conscious memory and (ii) the N400 component that varies with language comprehension. In each trial, the subject heard a category name, then viewed a word, and then decided whether the word was semantically congruous or incongruous (e.g. 'yes' for 'baby animal: cub'; 'no' for 'water sport: kitchen'). Recall and recognition testing at the end of the experiment showed that control subjects had better memory for congruous than for incongruous words, as did the amnesic patients, who performed less well overall. In contrast, amnesic patients were unimpaired on the category decisions required in each trial and, like the control subjects, showed a large N400 for incongruous relative to congruous words. Similarly, when incongruous trials were repeated after 0-13 intervening trials, N400s were reduced in both groups. When congruous trials were repeated, a late positive repetition effect was observed, but only in the control group. Furthermore, the amplitude of the late positive repetition effect was highly correlated with later word recall in both patients and controls. In the patients, the correlation was also observed with memory scores from standardized neuropsychological tests. These data are consistent with a proposed link between the late positive repetition effect and conscious memory. On the other hand, the N400 repetition effect was not correlated with episodic memory abilities, but instead indexed an aspect of memory that was intact in the amnesic patients. The preserved N400 repetition effect is an example of preserved memory in amnesia that does not easily fit into the categories of low-level perceptual processing or of motor learning. Instead, the sensitivity of the N400 to both semantic context and repetition may reflect a short-term memory process that serves language comprehension in realtime.

BACKGROUND AND PURPOSE:Noninvasive imaging plays a pivotal role in lateralization of the seizure focus in presurgical patients with temporal lobe epilepsy (TLE). Our goal was to evaluate the utility of diffusion tensor imaging (DTI) tractography in TLE.