Mike Matzke

Brain activity associated with syntactic incongruencies in words and pseudo-words

Event-related brain potentials (EMS) were recorded while normal German subjects read either simple declarative sen- tences made up from real German words, or sentences that contained German pseudo-words instead of nouns and verbs. The verb (pseudo-verb) of the sentences disagreed in number with the subject noun (pseudo-noun) in 50% of the sentences. The subjects had the task either to read the sentences for an interspersed memory test (memory condition, pseudeword sentences only) or to make a syntactic judgment after each real-word/pseudo-word sentence. While in the real-word condition a late and widespread positivity resembling the previously described syntactic positive shift was found for the disagreeing verbs, a negativity with an onset latency of about 300 msec was seen for the disagreeing pseudo-verbs. In the pseudo-word conditions no positivity followed the initial negativity. This dissociation of negative and positive waves occurring in response to morphosyntactic mismatches by the pseudo/real-word manipulation suggests that the positive shift is a concomitant of a recomputation routine initiated to account for the number incongruency. This routine is based upon the semantics of the sentence and therefore is not observed in the pseudo-word conditions. The earlier negativity, on the other hand, appears to be a more direct index of morphosyntactic incongruency.

Brain potentials reveal the timing of face identity and expression judgments

Event-related brain potentials (ERPs) were recorded from multiple scalp locations from young human subjects while they performed two different face processing tasks. The first task entailed the presentation of pairs of faces in which the second face was either a different view of the first face or a different view of a different face. The subjects had to decide whether or not the two faces depicted the same person. In the second task, pairs of faces (frontal views) were presented with the task of judging whether the expression of the second face matched that of the face. Incongruous faces in the view (identity) matching task gave rise to a negativity peaking at about 350 ms with a frontocentral maximum. This effect was similar to the N400 obtained in linguistic tasks. ERP effects in the expression matching task were much later and had a different distribution. This pattern of results corresponds well with neuropsychological and neuroimaging data suggesting specialized neuronal populations subserving identity and expression analysis but adds a temporal dimension to previous investigations.

The costs of freedom: an ERP – study of non-canonical sentences

OBJECTIVES The present investigation explored the electrophysiological correlates of working memory during sentence comprehension. METHODS Event-related brain potentials (ERP) were recorded from 29 channels in 22 subjects, while they read German sentences having subject-first (canonical) or object-first (non-canonical) word orders. RESULTS Three different ERP effects were observed: a negativity (maximum at Fc5) differentiating unambiguous object-first and subject-first sentences, interpreted as reflecting the demands of the object-first sentences on working memory; a second negativity (maximum at F7) to the subject noun-phrase in object-first sentences, interpreted as indicating retrieval of verbal material. Finally, a parietal positivity was found for ambiguous sentences that turned out to have a non-canonical word order, which was interpreted as indicating revision and reevaluation processes. CONCLUSIONS The present data underscore the different roles of working memory in comprehension.

Disturbed Monitoring and Response Inhibition in patients with Gilles De La Tourette Syndrome and Co-Morbid Obsessive Compulsive Disorder

Objective: Fronto-striatal dysfunction has been discussed as underlying symptoms of Tourette syndrome (TS) with co-morbid Obsessive Compulsive Disorder (OCD). This suggests possible impairments of executive functions in this disorder, which were therefore targeted in the present study. Results: A comprehensive series of neuropsychological tests examining attention, memory and executive functions was performed in a group of 14 TS/OCD in co-occurrence with OCD patients and a matched control group. Results: While attentional and memory mechanisms were not altered, TS/OCS patients showed deficits in executive functions predominately in the areas of response inhibition and action monitoring. Conclusions: These findings provide further evidence for a substantial impairment of the frontal-striatal-thalamic-frontal circuit. We propose that the deficits in monitoring, error detection and response inhibition constitute the major impairment of TS/OCD patients in the cognitive domain.

Low-Dose Treatment of Cervical Dystonia, Blepharospasm and Facial Hemispasm with Albumin-Diluted Botulinum Toxin Type A under EMG Guidance

Several studies support the hypothesis that low-dose botulinum toxin treatment may be as beneficial as high-dose regimen. Therefore, we studied 115 patients (aged 27–84; mean 58.0, SD = 12.9 years; 68% females, 32% males) suffering from cervical dystonia (n = 66), blepharospasm (n = 28), and facial hemispasm (n = 21) over a period of 2 years in an open label, non-controlled pilot study. Patients received low-dose treatment with botulinum toxin type A (Dysport®). The toxin was diluted in 20 ml of 0.1% albumin solution to arrive at a concentration of 25 MU/ml and injected under EMG control. Patients responded to the treatment about 1 week after injection (mean 7.3 days, SD = 4.6). The mean duration of beneficial effects was 11.7 weeks (SD = 5.6). Patients evaluated the clinical global improvement on a scale ranging from 0 to 4. For the whole population, the mean was 2.7 points (SD = 1.1). In none of the subjects could antibodies to botulinum toxin type A be detected, and only a few side effects were observed. In conclusion, low-dose therapy with botulinum toxin A merits further controlled studies.

Alteration of early components of the visual evoked potential in amyotrophic lateral sclerosis

Abstract Evoked potentials were recorded in three different visual experiments in 14 patients with amyotrophic lateral sclerosis (ALS) and 14 matched control subjects. Control subjects’ evoked potentials (EPs) were characterized by an initial positivity in the 90–140 ms range (P1) at the temporo-occipital site. This component was absent from the group average of the ALS patients as well as the individual patients’ EPs. As the P1 is known to emanate from inferior occipito-temporal areas, this finding provides electrophysiological evidence for a cortical involvement in ALS including visual areas.

Event-related potentials and EMDR treatment of post-traumatic stress disorder

Ten patients suffering from post-traumatic stress disorder (PTSD) following a severe traumatic event, were assessed with event-related brain potentials (ERPs) in a modified oddball paradigm containing auditory standard, target, and novel tones. ERPs were assessed before and after a treatment session using the eye movement desensitization and reprocessing method. Compared to a control group that underwent sham treatment, ERPs of the patients showed a reduction of the P3a component in the post-treatment recording, suggesting a reduced orienting to novel stimuli and reduced arousal level after the treatment. Moreover, psychometric assessment revealed a marked improvement of the PTSD symptoms after treatment.

EVENT-RELATED BRAIN POTENTIALS TO UNFAMILIAR FACES IN EXPLICIT AND IMPLICIT MEMORY TASKS

The purpose of this study was to investigate electrophysiological correlates related to the recognition of repeated faces in the intact human by means of event-related brain potentials (ERPs). A group of young healthy adults performed a continuous face recognition task, in which 240 unfamiliar faces were flashed upon a computer screen with 80 of the faces being repetitions. The subjects had to classify faces as previously seen and previously unseen faces. The concomitantly recorded ERPs from 19 scalp sites revealed a more positive going waveform for the correctly classified repeated faces beginning at about 280 ms (old/new effect). The same subjects performed a similar task with visually presented concrete nouns as stimuli. The old/new effect in this task showed a similar distribution, amplitude and onset latency. It is thus concluded that the old/new effect is not specific to the materials to be memorized. In contrast, the old/new effect in an implicit face repetition experiment (with the detection of famous persons being the task) showed a different distribution. It is argued that the differential distribution might reflect the different requirements of the two tasks (explicit vs. implicit task). Recent interpretations of the old/new effects are discussed.

Abnormalities of visual search behaviour in ALS patients detected with event-related brain potentials

A number of recent reports have emphasized neuropyschological symptoms in ALS, including frontal functions, memory and attention. We investigated visual search behaviour of ALS in two types of tasks: a simple, relatively effortless parallel search task and a more complex attention-demanding serial search task. Behavioural parameters and cognitive event-related potentials (ERP) from 19 scalp channels were obtained from 13 ALS patients and 13 matched controls during task performance. ALS patients showed the same target detection rates as controls in the parallel task but were significantly impaired in the serial task. Performance was slower in the patients than in the controls. This slowing could be attributed to cognitive rather than motor impairments, by inspection of the latency of the P3 component, which was delayed by 120 ms in the patients. In addition, the ERPs in the serial task showed a grossly reduced P3 amplitude, indicating disturbed stimulus evaluation in the patients under these conditions. Changes of an early attention-sensitive ERP component suggest an attention deficit underlying the disturbances in search behaviour. (Amyot Lat Scler 1999; 1:21–27)

ADEM-like presentation, anti-MOG antibodies, and MS pathology: TWO case reports

Acute disseminated encephalomyelitis (ADEM) mostly occurs in children and can be triggered by infections and vaccinations. Recently, 40% of patients with ADEM were found to be seropositive for myelin oligodendrocyte glycoprotein antibodies (MOG-abs).1 Furthermore, a subgroup of adult patients negative for aquaporin-4 antibody fulfilling diagnostic clinical and radiologic criteria for neuromyelitis optica spectrum disorder (NMOSD) harbor high-titer serum MOG-abs.2 We present clinical, serologic, and histopathologic features of 2 adult patients with a clinical diagnosis of ADEM according to the diagnostic criteria3 associated with intrathecal MOG-abs synthesis. MOG-abs were determined by live-cell immunofluorescence on HEK293T cells expressing full-length human MOG-enhanced green fluorescent protein at a starting dilution of 1:20 in serum and 1:2 in CSF using an epifluorescence microscope and end-point titration as previously described.2