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Biomedical subjects

T F Münte

Publications and source records attributed to T F Münte.

At least 19 recordsLinked to original sources
PubMed2003

Developmental dyslexics show altered allocation of attention in visual classification tasks.

OBJECTIVES: Event-related brain potentials (ERPs) were recorded to investigate allocation of attention in adult developmental dyslexics. SUBJECTS AND METHODS: Twelve adult developmental dyslexics and 12 matched normal controls performed three visual choice reaction tasks. In the passive oddball condition, subjects watched two different simple visual stimuli presented with 87.5 and 12.5% probability. In the active oddball condition, participants responded to the low-probability target stimulus. In the active 50/50-condition, both stimuli were presented with 50% probability and a response was required to the target stimulus only. RESULTS: No group differences emerged for performance, P300 latency or laterality and for N200 amplitude, latency or laterality. An enhancement of P300 amplitude with a frontal distribution was found for NoGo (standard)-stimuli in both active conditions for the dyslexic sample. CONCLUSION: Results are discussed in the context of deviances in allocation of attentional resources in dyslexic readers.

Adult↗
PubMed2001

Discrepant target detection and action monitoring in obsessive-compulsive disorder.

Obsessive-compulsive disorder (OCD) has been related to altered mechanisms of action monitoring and target detection, and it has been hypothesized that hyperactive striatal-cortical circuits constitute the underlying pathophysiology. This study used event-related brain potentials (ERPs) to explore this hypothesis. A choice reaction time experiment was carried out in a group of OCD patients and a normal comparison group. The P3b component of the ERP to targets was taken as an indicator of the target-evaluation process and the response-locked error-related negativity (ERN) served as an indicator of action monitoring. We hypothesized that the OCD group would show a shortened P3b latency and an amplitude-enhanced ERN. Consistent with our expectations, the P3b latency was shorter and the ERN amplitude was higher in the OCD group. Unexpectedly, we also observed a prolonged ERN latency in the OCD group and a more posterior topography of this component. The data provide partial support for the hypothesis of a hyperactive neural network in OCD. In addition the disorder must involve pathophysiological processes that are presumably related to other aspects of its complex and heterogeneous clinical hallmarks.

Adult↗
PubMed2001

Event-related brain potentials to sound omissions differ in musicians and non-musicians.

The mismatch negativity (MMN) component of the auditory event-related brain potential reflects the automatic detection of sound change. MMN to occasionally omitted sounds in a tone series can be used to investigate the time course of temporal integration in the acoustic system. We used MMN to study differences in temporal integration in musicians and non-musicians. In experiment 1, occasionally omitted 'sounds' in an otherwise regular tone series evoked a reliable MMN at interstimulus intervals (SOAs) of 100, 120, 180 and 220 ms in musicians. In non-musicians, MMN was smaller/absent in the 180 and 220 ms SOAs, respectively. In experiment 2, deviance of a tone was induced by presenting tones at a shorter SOA (100 or 130 ms) compared to the standard stimulus (150 ms). Musicians showed a reliable MMN for both deviant SOAs whereas non-musicians showed an MMN only for tones presented 50 ms prior to a standard tone (SOA 100 ms). These results indicate that the temporal window of integration seems to be longer and more precise in musicians compared to musical laypersons and that long-term training is reflected in changes in neural activity.

Acoustic Stimulation↗
PubMed2001

An electrophysiological analysis of the time course of conceptual and syntactic encoding during tacit picture naming.

A central question in psycholinguistic research is when various types of information involved in speaking (conceptual/semantic, syntactic, and phonological information) become available during the speech planning process. Competing theories attempt to distinguish between parallel and serial models. Here, we investigated the relative time courses of conceptual and syntactic encoding in a tacit picture-naming task via event-related brain potential (ERP) recordings. Participants viewed pictures and made dual-choice go/no-go decisions based on conceptual features (whether the depicted item was heavier or lighter than 500 g) and syntactic features (whether the picture's German name had feminine or masculine syntactic gender). In support of serial models of speech production, both the lateralized readiness potential, or LRP (related to response preparation), and the N200 (related to response inhibition) measures indicated that conceptual processing began approximately 80 msec earlier than syntactic processing.

Adult↗
PubMed2001

Human event-related potentials and distraction during selective listening.

Event-related brain potentials were recorded from healthy human subjects while they attended to one of two auditory stimulus channels (defined by location, left and right of a fixation point, and pitch) in order to detect rare target events. The distracting properties of periodic noise (vs. continuous noise, experiment 1) and backward speech (vs. forward speech, experiment 2) presented from a third speaker located behind the subjects were investigated. A typical attention effect with a larger negativity for attended tones was observed in both experiments. Backward speech led to a significantly reduced target detection rate for the first four stimuli after onset of the distractor accompanied by a reduced event-related brain potential (ERP)-attention effect and a reduced fronto-central N2b component for the target stimuli. This indicates that irrelevant information leads to an attention decrement of about 1 s duration.

Acoustic Stimulation↗
PubMed2001

Control of semantic interference in episodic memory retrieval is associated with an anterior cingulate-prefrontal activation pattern.

Prefrontal activation is a consistent finding in functional neuroimaging studies of episodic memory retrieval. In the present study we aimed at a further analysis of prefrontal neural systems involved in the executive control of context-specific properties in episodic memory retrieval using an event-related fMRI design. Nine subjects were asked to learn two 20-item word lists that consisted of concrete nouns assigned to four semantic categories. Ten items of both word lists referred to the same semantic category. Subjects were instructed to determine whether nouns displayed in random order corresponded to the first 20-item target list. The interference evoked by the retrieval of semantically related items of the second list resulted in significantly longer reaction times compared to the noninterference condition. Contrasting the interference against the noninterference retrieval condition demonstrated an activation pattern that comprised a right anterior cingulate and frontal opercular area and a left-lateralized dorsolateral prefrontal region. Trial averaged time series revealed that the PFC areas were selectively activated at the interference condition and did not respond to the familiarity of learned words. These findings suggest a functionally separable role of prefrontal cortical areas mediating processes associated with the executive control of interfering context information in episodic memory retrieval.

Adult↗
PubMed2001

Central effects of sildenafil (Viagra) on auditory selective attention and verbal recognition memory in humans: a study with event-related brain potentials.

The purpose of this study was to assess possible central side-effects of sildenafil (Viagra) on attention and memory functions. Sildenafil and placebo were administered in young male subjects in a double-blind balanced cross-over design. Behavioral patterns and event-related brain potentials (ERP) were recorded in a spatial auditory attention and a visual word recognition task. While behavioral patterns did not reveal any overt effects of sildenafil, auditory ERPs were indicative of an enhanced ability to focus attention (amplitude enhancement of Nd-effect) and to select relevant target stimuli in the sildenafil condition (P3 component). In the memory task, CNS-effects of sildenafil were evident in a reduction of a negativity in the 150-250 ms range. No overt effects on behavior were observed. Nevertheless, the data reveal CNS-effects of sildenafil necessitating further studies.

Adult↗
PubMed2001

Oxazepam alters action monitoring.

RATIONALE: Oxazepam has been demonstrated to slow reaction times and increase the rate of omission errors in attentional experiments. This suggests that action monitoring might also be impaired. OBJECTIVES: The present study used the event-related brain potential (ERP) technique to investigate this hypothesis. The P3b component to targets was taken as an indicator of the target evaluation process, and the response-locked error-related negativity (ERN) served as an indicator of action monitoring. We hypothesized that the amplitudes of ERN and P3b would be reduced as an effect of oxazepam. METHODS: A simple "oddball" reaction time experiment was conducted in a double-blind crossover study of 30 mg oxazepam versus placebo. In order to investigate variations in attentional allocation, separate experimental runs were undertaken with target frequencies of 50% and 80%. RESULTS: ERN and P3b amplitudes were lower in the 80% target condition than in the 50% condition. Oxazepam did not affect behavioral parameters but was associated with an ERN of lower amplitude than the placebo condition. ERN amplitude variations between target conditions remained unchanged. CONCLUSIONS: Although the intake of 30 mg oxazepam did not impair behavioral performance, measures of the electrophysiological recordings show that action monitoring processes were altered. We argue that this may be related to the anxiolytic properties of the drug and may constitute an important causal factor for behavioral impairments after the intake of oxazepam.

Adult↗
PubMed2001

Influence of cerebral lesion volume and lesion distribution on event-related brain potentials in multiple sclerosis.

Neurocognitive involvement in multiple sclerosis (MS) is heterogeneous with some authors suggesting a frontal pattern in patients with predominantly frontal lesions. To assess the relationship between the distribution of lesions and two cognitive components (visual N2, auditory P3a) of the event-related brain potential (ERP) receiving contributions from frontal lobe structures, we performed a combined ERP and magnetic resonance imaging (MRI) study. Thirty-four MS patients were assigned to "low lesion volume, (LLV)"(n = 12),"high lesion volume,(HLV)"(n = 12) and"frontal lesion volume, (FLV)" (n = 10) groups according to lesion volume and distribution on T2-weighted MRI-scans of the brain. ERPs in visual and auditory classification tasks as well as neuropsychological tests were carried out in patients and control subjects (n = 15). The index for automatic feature registration, the N2 component with its mainly frontal contribution in the visual task, was significantly reduced in amplitude in the FLV and HLV groups (both p < 0.01 vs. controls). Moreover its amplitude correlated with lesion volume (r=0.64, p < 0.001). In contrast neither P3a nor P3b subcomponents with a multiple generator nature in the auditory task varied systematically with lesion volume or distribution. Total lesion volume rather than predominant lesion arrangement appears to be the most important factor in neurocognitive changes in MS. This is most consistent with the view that MS lesions lead to partial disconnections within widespread cortical networks which in turn produce a pattern of neuropsychological deficits that reflect total lesion load more than lesion distribution.

Adult↗
PubMed2001

Differences in brain potentials to open and closed class words: class and frequency effects.

Closed class (determiners, pronouns, conjunctions, prepositions etc. ) and open class (nouns, verbs, adjectives, adverbs) words have different linguistic functions and have been proposed to be processed by different neural systems. Here, event-related potentials (ERPs) were recorded in young German-speaking subjects while they read closed class and open class words flashed upon a video-screen. In the first experiment closed class words were sorted into four different frequency categories and open class words into three categories. The words were presented in a list with the subjects' task to detect occasional non-words. A centroparietal negativity (N400) with a peak latency of about 400 ms varied in amplitude as a function of frequency in both classes. The N400 in closed class items, however, was considerably smaller than that in open class words of similar frequency. A left anterior negativity (N280/LPN) showed some degree of frequency-sensitivity regardless of word class. Only for the very high frequency closed class words a frontal negativity with an onset of about 400 ms was obtained (N400-700). This N400-700 effect was replicated in the second study, in which medium frequency closed and open class words and very high frequency closed class words were presented at the fifth position of simple German sentences. It is suggested that neither N400 nor the left anterior negativity (N280/LPN) distinguish qualitatively between the two word classes and thus claims about different brain systems involved in the processing of open and closed class words are not substantiated electrophysiologically. The N400-700 effect is possibly related to specific grammatical functions of some closed class items, such as determiners.

Adult↗
PubMed2001

Deficit in automatic sound-change detection may underlie some music perception deficits after acute hemispheric stroke.

Music perception deficits following acute neurological damage are thought to be rare. By a newly devised test battery of music-perception skills, however, we were able to identify among a group of 12 patients with acute hemispheric stroke six patients with music perception deficits (amusia) while six others had no such deficits. In addition we recorded event-related brain potentials (ERPs) in a passive listening task with frequent standard and infrequent pitch deviants designed to elicit the mismatch negativity (MMN). The MMN in the patients with amusia was grossly reduced, while the non-amusic patients and control subjects had MMNs of equal size. These data show that amusia is quite common in unselected stroke patients. The MMN reduction suggests that amusia is related to unspecific automatic stimulus classification deficits in these patients.

Acute Disease↗
PubMed2001

Electrophysiological estimates of semantic and syntactic information access during tacit picture naming and listening to words.

We investigated the relative time courses of the accessibility of semantic and syntactic information in speaking and comprehension via event-related brain potentials (ERPs). Native German speakers either viewed a series of pictures (tacit picture naming experiment) or heard a series of nouns (listening experiment) and made dual choice go/nogo decisions based on each item's semantic and syntactic features. N200 peak latency results indicate that access to meaning has temporal precedence over access to syntactic information in both speaking (approximately 80 ms) and comprehension (approximately 70 ms), and are discussed in the context of current psycholinguistic theories.

Adult↗
PubMed2001

Event-related brain responses to morphological violations in Catalan.

The ERP (event-related potential) violation paradigm was used to investigate brain responses to morphologically correct and incorrect verb forms of Catalan. Violations of stem formation and inflectional processes were examined in separate experimental conditions. Our most interesting finding is that misapplications of stem formation rules elicit an early left preponderant negativity. This complements our previous ERP results on morphological violations in other languages in which misapplications of inflectional rules were shown to produce such effects. We make use of the linguistic distinction between lexically stored and rule-based word forms and suggest a unified interpretation of the experimental results, arguing that these negativities vary as a function of processes involved in morpho-syntactic structure building.

Adult↗
PubMed2001

General anesthesia for interventional neuroradiology: propofol versus isoflurane.

STUDY OBJECTIVE: To compare recovery of psychomotor and cognitive ability after isoflurane and propofol-based general anesthesia. DESIGN: Prospective, blinded interventional study. SETTING: University hospital. PATIENTS: 24 ASA physical status I and II patients undergoing embolization procedures for intracranial vascular lesions. INTERVENTIONS: Isoflurane anesthesia or propofol anesthesia was given to patients. MEASUREMENTS: Awakening time; early recovery (5 minutes, 15 minutes, 30 minutes) was assessed using orientation and Steward tests; medium recovery (30 minutes, 60 minutes, 120 minutes) was tested using Controlled World Association (COWAT) and Digit Span tests; late recovery (4 hours, 24 hours) was assessed using a Verbal Learning and Memory Test and three subtests of a computerized attention test battery. MAIN RESULTS: Awakening time and early recovery of motor and respiratory function did not differ between groups. The propofol group scored worse in COWAT and Digit Span tests up to 60 minutes after anesthesia. Both groups showed an impairment of higher cognitive functions up to 24 hours after anesthesia. CONCLUSIONS: Both isoflurane- and propofol-based anesthesia allow early extubation and recovery of basic psychomotor functions. More sophisticated tests show a decline of cognitive functions up to 24 hours after isoflurane- as well as propofol-based anesthesia. Because both anesthetics show similar recovery of psychomotor functions after long duration anesthesia, other factors such as subjective well-being and costs may be considered when deciding between these two anesthetics.

Adolescent↗
PubMed2001

Postoperative reading speed does not indicate implicit memory in elderly cardiac patients after propofol and remifentanyl anaesthesia.

BACKGROUND: A recent study in young patients undergoing propofol-alfentanil-nitrous oxide anaesthesia demonstrated implicit memory for stories presented during operation using a postoperative reading speed task. In this study we investigated whether patients who tolerate only small amounts of anaesthetics are prone to develop implicit and explicit memories about intraoperative events. METHODS: Thirty patients with poor physical status (ASA III-IV) undergoing cardioverter defibrillator implantation were included in the study. Patients were premedicated with intravenous midazolam and anaesthesia was maintained using propofol and remifentanil infusions. During surgery one of two audio-tapes containing two short stories was played to the patients. Reading speed for the stories played during surgery and two similar stories from the other tape was tested 4 h later. Explicit memory was tested at 4 h and 24 h after audiotape presentation using a structured interview and a forced-choice recognition test pertaining to the story content. Thirty additional awake subjects served as controls. RESULTS: Although half of the patients seemed to be awake one or more times during the operation, no explicit memories of intraoperative events were reported. The forced-choice recognition of the stories was at chance level. No effect on reading speed was found in either the patients or the control subjects. CONCLUSIONS: The possible reasons for reduced explicit and implicit memory performance in elderly patients are age and poor physical status of the patients and the modality change between study and test phases. A non-anaesthetised control group of the same age and physical status should therefore be included in all studies of implicit memory.

Acoustic Stimulation↗
PubMed2001

Altered inhibition of motor responses in Tourette Syndrome and Obsessive-Compulsive Disorder.

OBJECTIVES: The Gilles de la Tourette Syndrome (TS) and Obsessive Compulsive Disorder (OCD) have been shown to display impaired cognitive and motor inhibition. This study investigated inhibitory mechanisms of motor responses in order to expand the understanding of sensorimotor integration processes in both disorders. We hypothesized that both patient groups would display altered frontal inhibitory activity. MATERIAL AND METHODS: To this end event-related brain potentials (ERPs) were recorded in a STOP-paradigm in groups of TS and OCD patients and in a control group. The paradigm required the execution of a motor response after a "go" signal was given and the occasional suppression of this response after a second "stop" signal occurred. RESULTS: Behavioral parameters and Lateralized Readiness Potential (LRP) confirmed that both patient groups were well able to initiate motor responses. "Go" and "stop" stimuli elicited an enhanced frontal negative activity in both patient groups. In addition, "stop" stimuli were associated with a frontal shift of the NoGo-Anteriorization (NGA) in the TS group but not in the OCD group. CONCLUSIONS: The data are interpreted to indicate altered frontal inhibitory functions. Similarities and dissimilarities between the findings for TS and OCD are discussed with respect to other pathophysiologic aspects of the disorders.

Adolescent↗
PubMed2001

Electrophysiological measures and dual-task performance in Tourette syndrome indicate deficient divided attention mechanisms.

Tourette syndrome has been associated with impairments of attentional functions such as distractability, even in subjects without co-morbid attention deficit hyperactivity disorder. Based on the results of earlier research we hypothesized that Tourette syndrome patients might employ altered control mechanisms of attentional processes and have concurrent difficulties in allocating their attentional resources among competing tasks. Event-related brain potentials (ERPs) were recorded in a group of Tourette syndrome patients and in a matched control group during a dual task experiment. This experiment required the simultaneous detection of visual and auditory target stimuli which were manipulated to yield two different difficulty levels each of which were varied orthogonally. The behavioural parameters confirmed the intended performance differences between difficult-to-detect targets and easy-to-detect targets. This was paralleled by lower amplitudes and longer latencies of the corresponding P3b-ERP subcomponents. Although Tourette syndrome patients were unimpaired in overall performance they showed an increased interference of visual task demands with auditory target perception. In parallel they also exhibited a reduced amplitude of the P3b component to auditory targets. The findings show that Tourette syndrome patients are not generally impaired in their dual task performance. The allocation of attentional resources to competing tasks however, is altered. We speculate that this may be related to deficient inhibitory functions.

Adolescent↗