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Biomedical subjects

T F Münte

Publications and source records attributed to T F Münte.

At least 37 records · Page 2Linked to original sources
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↗
PubMed2001

Alterations of cognitive functions induced by exogenous application of thyroid hormones in healthy men: a double-blind cross-over study using event-related brain potentials.

The influence of experimentally induced subclinical hyperthyroidism on cognitive functions was tested using exogenous thyroxine or placebo. In a double-blind cross-over design, 24 healthy young men received either 300 microg of levothyroxine or placebo for two consecutive 3-week periods. Determination of thyrotropin (TSH), total triiodothyronine (T3), thyroxine (T4), and sex hormone binding globulin (SHBG) confirmed the induction of subclinical hyperthyroidism. Three weeks after treatment with placebo or T4, subjects were tested in two visual search tasks, one requiring the serial scanning of a stimulus array of eight items in order to detect a missing feature (serial task), while the other task allowed the parallel processing of eight items in order to detect an extra feature. Reaction times varied greatly between the tasks while no effect of T4 medication was revealed on overt search behavior. The late cognitive components of the event-related brain potentials (ERP) were registered during the tasks using a multichannel recording. The late positive component (P300) to target stimuli showed a significant reduction in amplitude in the parallel search task in hyperthyroidism, while for the serial search task a significant frontal negativity was revealed for target stimuli, both suggesting an increased effort to be exerted for the execution of visual search tasks. Thus, short periods of subclinical hyperthyroidism in the range commonly induced in the treatment of thyroid cancer patients induce distinct alterations in brain-electric activity.

Adult↗
PubMed2001

Differential effects of emotional content on event-related potentials in word recognition memory.

The aim of this study was to delineate the influence of the emotional content of stimuli to be remembered on the recognition performance of normal subjects by means of the event-related potential (ERP) technique. When words are presented repeatedly, brain responses to repeated and recognized items are characterized by a more positive waveform, referred to as "old/new effect". Words judged for their emotional connotation ("negative", "positive" and "neutral") were presented successively on a video monitor to subjects, who had the task to indicate whether a given word occurred for the first ("new") or second ("old") time within the list by pressing one of two buttons. For each word category, the ERPs of the old words were more positive compared to those of the new items from about 250 ms after stimulus. The old/new effect was significantly enhanced for the negative and positive items compared to the neutral stimuli between 450 and 650 ms after stimulus pointing to a significant influence of the emotional content of words on verbal memory processes. This paradigm appears to be feasible to investigate interactions of emotion and cognition in psychiatric patients.

Adult↗
PubMed2000

Emotion/cognition-coupling in word recognition memory of depressive patients: an event-related potential study.

Depressive patients show deficits in memory functions. However, the underlying mechanisms remain unclear. Experiments with a special emphasis on the link between emotion and cognition appear challenging. The aim of this study is to investigate the influence of the emotional content of words on memory in non-medicated depressive patients (n=11) compared with a control group (n=11) utilizing event-related brain potentials (ERPs). In a continuous word recognition paradigm brain responses to repeated items are characterized by more positive waveforms of ERPs. This recognition effect ('old/new effect') has been shown to be sensitive to parameters relevant for memory processing. For the purpose of this ERP experiment visually presented words were classified into three different categories of emotional content. The ERPs for the correctly detected 'old' (repeated) words showed an increased positivity beginning approximately 250 ms post-stimulus, concurring with a good recognition performance. In addition, old/new effect and behavioral data were sensitive to words' different emotional connotations in the control group. In contrast, the depressive patients performed worse and showed no significant old/new effect. Nevertheless, their recognition performance was also enhanced by the emotional content. Furthermore, a differential effect of the emotional content on frontal ERPs was found between groups. In contrast to the control group, a reduced old/new effect indicates a reduced working memory capacity in the moderately depressed patients. This is suggested to be partially due to changes of the emotion/cognition coupling related to ruminations with preferably negative emotional connotation. However, the emotional content also affects recognition performance in the depressive patients.

Adult↗
PubMed2000

Brain potentials in the processing of complex sentences: an ERP study of control and raising constructions.

In the present study we made use of Event-Related Potentials (ERPs) to examine raising and subject control constructions in German. Our most salient result is that the ERPs elicited at the empty subject position of a raising construction are clearly different from those elicited at the corresponding position of an otherwise identical subject control construction, the former producing a stronger P600. We argue that this result provides an electrophysiological correlate of the theoretical distinction between NP trace and PRO.

Brain↗
PubMed2000

Receptive amusia: evidence for cross-hemispheric neural networks underlying music processing strategies.

Perceptual musical functions were investigated in patients suffering from unilateral cerebrovascular cortical lesions. Using MIDI (Musical Instrument Digital Interface) technique, a standardized short test battery was established that covers local (analytical) as well as global perceptual mechanisms. These represent the principal cognitive strategies in melodic and temporal musical information processing (local, interval and rhythm; global, contour and metre). Of the participating brain-damaged patients, a total of 69% presented with post-lesional impairments in music perception. Left-hemisphere-damaged patients showed significant deficits in the discrimination of local as well as global structures in both melodic and temporal information processing. Right-hemisphere-damaged patients also revealed an overall impairment of music perception, reaching significance in the temporal conditions. Detailed analysis outlined a hierarchical organization, with an initial right-hemisphere recognition of contour and metre followed by identification of interval and rhythm via left-hemisphere subsystems. Patterns of dissociated and associated melodic and temporal deficits indicate autonomous, yet partially integrated neural subsystems underlying the processing of melodic and temporal stimuli. In conclusion, these data contradict a strong hemispheric specificity for music perception, but indicate cross-hemisphere, fragmented neural substrates underlying local and global musical information processing in the melodic and temporal dimensions. Due to the diverse profiles of neuropsychological deficits revealed in earlier investigations as well as in this study, individual aspects of musicality and musical behaviour very likely contribute to the definite formation of these widely distributed neural networks.

Acoustic Stimulation↗
PubMed2000

No implicit memory for stories played during isoflurane/alfentanil/nitrous oxide anesthesia: a reading speed measurement.

UNLABELLED: Implicit memory of intraoperatively presented stories was recently detected by using the reading speed paradigm during propofol-alfentanil-nitrous oxide anesthesia. Our main goal was to evaluate the reading speed test procedure under another anesthetic regimen, i.e., isoflurane combined with nitrous oxide and alfentanil-infusion. In both experiments, patients were premedicated with oral midazolam. In a previous experiment, patients postoperatively read "old" stories that had been presented during anesthesia quicker compared with "new," unpresented stories. The same study design and test material as in the previous experiment were used. One of two audio tapes with two short stories was played randomly to patients during lumbar disk surgery and to awake controls. Approximately 7 h later, a structured interview and the reading speed test were used to determine whether the participants had any explicit or implicit memories of the presented stories. The results of 30 patients and 30 controls were calculated. Whereas the control participants showed an intact explicit and implicit memory of the previously presented material, no such effect was found in the anesthetized patients. The present experiment shows that changing the main anesthetic in otherwise equal study conditions, i. e., propofol to isoflurane (end-expiratory 0.7%), implicit memory is abolished in anesthetized patients. IMPLICATIONS: We showed that implicit memory during general anesthesia can be abolished by changing the hypnotic anesthetic. Increased postoperative reading speed for stories presented during propofol-alfentanil-nitrous oxide anesthesia was shown in a previous experiment, but not in our study using isoflurane for balanced anesthesia.

Adult↗
PubMed2000

Electrophysiological estimates of the time course of semantic and phonological encoding during implicit picture naming.

Two different event-related potential (ERP) components were used to investigate the temporal processing of semantic and phonological encoding during implicit picture naming. Participants were shown pictures and carried out a dual choice go/nogo decision based on semantic information (i.e., whether the picture was of an object or an animal) and phonological information (i.e., whether the picture's name starts with a vowel or a consonant). In addition to the already established lateralized readiness potential (LRP; related to response preparation), we introduce the N200 (presumably related to response inhibition) as a tool for measuring online language processing. Both, the LRP and the N200 data indicated that semantic processing began earlier than phonological processing. The data are discussed in the context of language production models. Therein, the LRP and N200 results, taken together, favor a serial or cascaded processing model of language production in contrast to a parallel processing account.

Adult↗
PubMed1999

Intra-modal and cross-modal spatial attention to auditory and visual stimuli. An event-related brain potential study.

This study investigated cross-modal interactions in spatial attention by means of recording event-related brain potentials (ERPs). Noise bursts and light flashes were presented in random order to both left and right field locations separated by 60 degrees in free-field. One group of subjects was instructed to attend selectively to the noise bursts (attend-auditory group), and a second group attended only to the flashes (attend-visual group). On different runs attention was directed to either the right or left field stimuli of the designated modality. In the attend-auditory group, noise bursts at the attended location elicited a broad, biphasic negativity (Nd) beginning at 70 ms. The cross-modal spatial attention effect on the auditory ERPs in the attend-visual group was very similar in morphology, but the Nd was reduced in amplitude relative to the intra-modal effect. In the attend-visual group, flashes at the attended location elicited enhanced early (100-200 ms) and late (200-350 ms) ERP components relative to unattended-location flashes. The cross-modal effect in the attend-auditory group included small but significant enhancements of early components of the visual ERPs. It was concluded that spatial attention has a multi-modal organization such that the processing of stimuli at attended locations is facilitated at an early, sensory level, even for stimuli of an unattended modality.

Acoustic Stimulation↗
PubMed1999

Effects of synthetic delta9-tetrahydrocannabinol on binocular depth inversion of natural and artificial objects in man.

Binocular depth inversion represents an illusion of visual perception that is sensitive to various behavioural and psychiatric conditions. It is affected by cannabinoids, reflecting associated changes in perception. The present study investigated the differences in binocular depth inversion of different classes of natural and artificial objects and the effect of synthetic delta9-tetrahydrocannabinol (Dronabinol) on these illusionary perceptions. Using this model, the effects of orally administered Dronabinol on binocular depth inversion were investigated in 17 healthy male volunteers. Pictures from natural and artificial objects were presented stereoscopically and the depth perception of the volunteers was scored in an operationalized way. The timecourse of the effects of Dronabinol on binocular depth inversion was analyzed with regard to the stimulus classes (natural and synthetic objects). Significant differences in binocular depth inversion of the different groups of stimuli were revealed. Objects with a higher degree of everyday familiarity were generally seen as more illusionary than those with a lower degree of everyday familiarity. A strong impairment of binocular depth inversion due to Dronabinol was found in most classes of objects. Analysis of different stimulus classes provides further information on the underlying perceptual processing of binocular depth inversion. An impairment of top-down processing of visual sensory data by Dronabinol is suggested. The anandamidergic system seems to be involved in areas of visual information processing.

Adult↗
PubMed1999

Decomposition of morphologically complex words in English: evidence from event-related brain potentials.

To explain processing differences between regular (e.g., start/started) and irregular (e.g., think/thought) word formation linguistic models posit either a single mechanism handling both morphological clusters or separate mechanisms for regular and irregular words. The purpose of the present study is to investigate how these processing differences map onto brain processes by assessing electrophysiological effects of English past tense forms, using the repetition priming paradigm. Event-related brain potentials (ERPs) were recorded from 59 scalp sites as 19 subjects read stem forms of regular and irregular verbs from a list of 1152 words; the stem forms were either preceded (5-9 intervening items) by their past tense forms (=primed condition) or by past tense forms of unrelated verbs (=unprimed condition). The difference between the ERPs to the primed and unprimed stems was taken as a measure of morphological priming. We found that the ERPs to regular verbs were clearly different from those to irregular verbs: the former were associated with an N400 reduction in the primed condition; primed irregular verb stems, however, showed no such effect. Control conditions demonstrated that the N400 modulation for regular verbs cannot be attributed to formal (i.e., phonological or orthographical) priming. These ERP effects indicate that regular verbs serve as more powerful primes for their corresponding stem forms than irregular past tense forms, suggesting that regular (but not irregular) past tense forms may be decomposed into stem plus affix.

Adolescent↗