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Biomedical subjects

H Ackermann

Publications and source records attributed to H Ackermann.

At least 55 records · Page 3Linked to original sources
PubMed1998

Does the cerebellum contribute to cognitive aspects of speech production? A functional magnetic resonance imaging (fMRI) study in humans.

Several positron emission tomography (PET) studies suggest a contribution of the lateral aspects of the right cerebellar hemisphere to higher-level (cognitive) aspects of speech production such as controlled verbal response selection. As an alternative, however, 'inner speech', giving rise to subliminal activity of orofacial and laryngeal muscles, might account for the observed activation effects. Eighteen subjects underwent functional magnetic resonance imaging (fMRI) during continuous silent recitation of the names of the months of the year ('automatic speech'). The right cerebellar hemisphere showed a significantly increased hemodynamic response concomitant with, among others, an asymmetric activation pattern towards the left side at the level of the motor strip. Since highly overlearned word strings, presumably, pose few demands on controlled response selection and since the projections of the right cerebellar hemisphere to the left precentral gyrus participate in motor control, the observed cerebellar activation, thus, seems to be related to the articulatory level of speech production rather than, as suggested by previous PET studies, to cognitive operations.

Adult↗
PubMed1998

Dissolution of gallbladder stones with methyl tert-butyl ether and stone recurrence: a European survey.

Since there are now several ways to treat symptomatic gallstone disease, one is able to select treatment on the basis of the patient's comfort, the practicability, effectiveness, and side effects of the technique, and the relative costs. In order to assess the present status of contact dissolution with methyl tert-butyl ether with regard to these aspects, the present enquiry reports the data of 21 European hospitals. Eight hundred three patients were selected for contact litholysis of cholesterol gallbladder stones using methyl tert-butyl ether. Percutaneous transhepatic puncture of the gallbladder was performed under x-ray or ultrasound guidance. Dissolution rate, side effects, and treatment times of 268 patients from one single center were compared to those of 535 patients from the other 20 centers. Two hundred sixty-four patients were followed for five years to assess stone recurrence. Physicians were asked how they assessed the expenditure of the method, the discomfort to the patients, and the staffing situation. Patients were asked to indicate their acceptance on an analog scale. Puncture was successful in 761 (94.8%) patients. Prophylactic administration of antibiotics was not necessary. Stones were dissolved in 724 (95.1%) patients. In 315 (43.5%) sludge remained in the gallbladder. The most severe complication was bile leakage, which led 12 (1.6%) patients to have elective cholecystectomy. Toxic injuries due to the ether were not reported. Method-related lethality amounted to 0%, 30-day-lethality to 0.4%. Stone recurrence rate was about 40% in solitary stones and about 70% in multiple stones over five years. Patients with multiple stones developed recurrent stones almost twice as often as those with solitary stones. The probability of stone recurrence in patients with sludge in the gallbladder after catheter removal was not statistically significantly different from those without sludge. Seventy to 90% of the centers found the puncture to be simple and not distressing for patients and the relation between expenditure and therapeutic success to be acceptable. The acceptance of contact litholysis by the patients was excellent. Contact litholysis when applied by an experienced team provides real advantages in the treatment of gallstone disease. The method is technically simple, well accepted by the patients, and can be easily applied in community hospitals. Contact litholysis may be of particular value in patients who are not suitable for anesthesia or surgery.

Adolescent↗
PubMed1997

Categorical speech perception in cerebellar disorders.

Keele and Ivry (1991) considered the cerebellum an "internal clock" responsible for temporal computations both in the motor and in the perceptual domain. These authors, therefore, expected that the processing of durational parameters of the perceived acoustic speech signal such as voice onset time (VOT) depends upon the cerebellum as well. However, a preliminary investigation of Ivry and Gopal (1992) revealed unimpaired phoneme-boundary effects in cerebellar patients along a continuum of monosyllabic stimuli with systematically varied VOT (/ba/-/pa/). Since the energy of the aspiration noise provides additional cues for the discrimination of voiced and voiceless stops, the present study used a series of disyllabic stimuli differing in a purely durational parameter. Both controls and patients with unilateral cerebellar lesion identified the endpoints of this continuum in nearly all instances as the counterparts of a minimal pair (Boten, /bo:tn/, "messengers" versus Boden, /bo:dn/, "floor"). Subjects with bilateral pathology of the cerebellum, in contrast, did not show a comparable phoneme-boundary effect. Our data corroborate the hypothesis of the cerebellum as an internal clock and implicate a role of this structure in speech perception.

Adult↗
PubMed1997

Voice onset time in ataxic dysarthria.

In eight patients with a purely ataxic syndrome due to cerebellar atrophy the voice onset time (VOT) of word-initial stop consonants was measured at the acoustic signal. The subjects had been asked to produce sentence utterances including either one of the German minimal pair cognates "Daten" (/daten/, "data") and "Taten" (/taten/, "deeds"). In addition, a master tape comprising the target words from patients and controls in randomized order was played to six listeners for perceptual evaluation. Two major findings emerged. First, the cerebellar subjects presented with a reduced categorical distinction of the VOT of voiced and unvoiced stop consonants. Second, the patients' target words with initial unvoiced plosive gave rise to a significantly increased number of misassignments at perceptual evaluation. To some extent comparable VOT disruptions have been noted in apraxia of speech and basal ganglia disorders. Thus, different pathomechanisms might result in similar VOT abnormalities.

Adult↗
PubMed1997

The cortical processing of perceived emotion: a DC-potential study on affective speech prosody.

Direct current (DC) components of the EEG signal were recorded in 16 right-handed subjects during presentation of pairs of declarative sentences with either happy, sad or neutral intonation. Each stimulus pair had identical wording, but differed at the acoustic level either in pitch (fundamental frequency = FO) range or in duration of stressed syllables. Subjects were asked, first, to identify the emotional category of each sentence pair and, second, to indicate the utterance displaying stronger emotional expressiveness. Stimuli with happy or sad intonation, as well as FO-manipulated neutral sentences, yielded a significantly lateralized negativity towards the right hemisphere (RH). Compared with FO-varied neutral utterances, the discrimination of time-manipulated neutral stimuli resulted in significantly reduced amplitudes, predominantly over RH areas. These results corroborate the suggestion of a dominant role of the RH for the evaluation of the emotional significance of sensory input.

Acoustic Stimulation↗
PubMed1997

Prognostic significance of polo-like kinase (PLK) expression in non-small cell lung cancer.

Our previous data indicate that the expression of the PLK gene which codes for a serine/threonine kinase is restricted to proliferating cells. In Northern blot experiments PLK mRNA expression was at the limit of detection in normal lung tissue but elevated in most samples of non-small cell lung cancer (NSCLC). A very low frequency of PLK transcripts was only found in bronchiolo-alveolar carcinomas. NSCLC patients whose tumors showed moderate PLK expression survived significantly longer (5 year survival rate=51.8%) than those with high levels of PLK transcripts (24.2%, P=0.001). No statistically significant correlation was found between PLK mRNA expression and age, sex, TNM status, histological type or degree of differentiation. Interestingly, the prognosis of patients in post-surgical stages I and II was correlated with PLK expression (5 year survival rates in stage I: 69.1% (moderate PLK) - 43.5% (high PLK), P=0.03 or in stage II: 51.9% (moderate PLK) - 9.9% (high PLK), P=0.006). These results suggest that PLK mRNA expression provides a new independent prognostic indicator for patients with NSCLC.

Adenocarcinoma, Bronchiolo-Alveolar↗
PubMed1997

The temporal control of repetitive articulatory movements in Parkinson's disease.

Recent clinical data indicate that internal cueing mechanisms required for the triggering of movement sequences are impaired in Parkinson's disease (PD). Nevertheless, most PD subjects produce maximal syllable repetition rates similar to those observed in healthy control individuals during oral diadochokinesis tasks. There is some evidence that tremor oscillations may pace repetitive movements in Parkinsonians giving rise to hastening phenomena. Conceivably, the performance of PD patients in syllable repetition tasks thus reflects a specific timing deficit, i.e., articulatory hastening. It is the aim of the present study to investigate the contribution of speech hastening to oral diadochokinesis in the presence of internal and external cues. By means of an optoelectric movement analysis system, the displacements of the lips during repetitions of the syllable /pa/ were recorded in two akinetic-rigid PD individuals. Subjects were asked to synchronize labial diadochokinesis to sequences of periodic acoustic stimuli (2.5-6 Hz). One of the PD patients showed speech hastening, i.e., he produced repetitions of 8 to 9 Hz whenever stimulus frequencies exceeded 4 Hz. The other Parkinsonian adequately matched the stimulus frequencies required. However, she achieved a higher diadochokinesis rate in the matching task than under the instruction to repeat "as fast as possible." Thus, the presence of an external cue improved performance. In conclusion, our data indicate two deficits of the temporal control of repetitive articulatory gestures in PD: speech hastening and impaired self-paced sequencing. These two pathomechanisms may allow to reconcile the controversial findings on oral diadochokinesis in PD reported so far.

Female↗
PubMed1997

Control of repetitive lip and finger movements in Parkinson's disease: influence of external timing signals and simultaneous execution on motor performance.

This study addresses the question of whether external timing signals and/or simultaneous rhythmic movements of other limbs can alleviate sequencing motor deficits associated with Parkinson's disease (PD). Subjects performed rhythmic lip and finger movements simultaneously or in isolation. In addition, they had to self-pace their movements or match them to an external signal. Our results are summarized as follows: (1) Seven of 12 patients had adequate mean repetition rates; that is, they fulfilled the task requirements on a global scale. The remaining five patients had various degrees of hastened responses and were not fully able to synchronize their movements to an external pacing signal. (b) PD patients exhibited hypometria in their finger tapping, but not in their lip movements. Their movements were not abnormally slowed, but peak velocity was appropriately scaled, even to reduced movement amplitudes. (c) Mean repetition rates, stability of frequency response, and kinematics did not differ between conditions of external and internal stimulation within the PD group, but were different form the control group performance. (d) Kinematic measures were not improved during dual-task execution. PD patients were not able to maintain a 1:1 rhythm between effectors. The incidence of hastening increased during simultaneous motor execution. We conclude that the use of external pacing signals might aid movement initiation of PD patients, but does not improve their temporal or spatial coordination when generating repetitive movements. Simultaneous execution does not necessarily enhance motor performance, but might actually have detrimental effects in patients prone to hastening.

Aged↗
PubMed1997

Kinematic analysis of articulatory movements in central motor disorders.

The various components of the central motor system are expected to play a similar role in speech production and in upper limb control. Slowed articulatory performance, therefore, must be expected in disorders of the corticobulbar tracts, cerebellum, and basal ganglia. Using an optoelectronic device, the present study recorded lower lip trajectories during production of sentence utterances in patients with Parkinson's disease (PD), Huntington's disease (HD), cerebellar atrophy (CA), and pseudobulbar palsy (PB). The various subject groups showed a similar range of overall motor disability. Patients with CA and PB exhibited slowed movement execution in terms of a reduced ratio of peak velocity to maximum amplitude ("stiffness"). In contrast to upper limb motor control, the lip excursions showed an uncompromised shape of velocity profiles. Two different patterns emerged in HD. A single patient suffering from the akinetic-rigid Westphal variant of this disease had articulatory hypometria, whereas the remaining subjects showed significant bradykinesia under increased temporal demands, concomitant with normal movement amplitudes. The PD patients had unimpaired velocity-displacement relationships. Presumably, biomechanical constraints such as the rather small excursions of articulatory lower lip gestures or the scarce spindle supply of facial muscles account for the observed discrepancies between upper limb and speech motor control in PD.

Aged↗
PubMed1997

Neuropsychological abnormalities in cerebellar syndromes--fact or fiction?

In recent years, theoretical considerations and a large number of empirical investigations have been published in support of a cerebellar involvement in cognitive processing. This chapter aims at a critical evaluation of the neuropsychological findings from clinical studies of patients with cerebellar syndromes. The discussion will mainly consider data from patients with selective cerebellar dysfunction, as data from patients with combined cerebellar and extracerebellar damage are of limited value for the issue of a cerebellar involvement in cognition. Early clinical observations indicated that degenerative diseases or selective cerebellar lesions did not necessarily give rise to general intellectual impairment such as dementia. Recent neuropsychological evidence based on standardized testing does not yet provide a clear picture. Deficits in motor learning or temporal processing are consistently observed in patients with cerebellar syndromes, while the cerebellum does not appear to be critically involved in general intellectual capacities or memory. Deficits in frontal lobe function, visuospatial processing or nonmotor skill learning have been reported in several studies, but have not been replicated in others. Such discrepancies may relate to a number of methodological problems. Future neuropsychological studies should take such methodological issues into account by using patients with selective cerebellar dysfunction, adequately matched clinical and non-clinical comparison groups, and theory-driven iesl batteries comprising a wide range of tests.

Animals↗
PubMed1997

[Nondeclarative memory--neuropsychological findings and neuroanatomic principles].

The contents of long-term memory will influence behaviour, even if the acquired knowledge or the original learning episode are not remembered. These phenomena have been termed "non-declarative" or "implicit" memory, and they are contrasted with "declarative" or "explicit" memory which is characterised by conscious search and retrieval procedures. Non-declarative memory encompasses non-associative learning, simple conditioning, priming effects as well as motor, perceptual and cognitive skill acquisition. The dissociation of both forms of memory is documented by studies in health subjects which indicated that experimental manipulations or drugs may differentially affect declarative and non-declarative memory processes. Damage to the medial temporal or the medial thalamic regions is known to result in declarative memory deficits whereas non-declarative memory is largely unaffected by such lesions. Animal research and clinical findings indicate that several components of non-declarative memory such as motor and cognitive skill acquisition or certain types of classical conditioning are dependent upon the integrity of the basal ganglia or the cerebellum. These issues are therefore of increasing importance for the understanding of extrapyramidal and cerebellar diseases. This paper presents recent neuropsychological findings and neuroanatomical data relating to the issue of non-declarative memory.

Animals↗
PubMed1997

[Neuroradiologic activation studies of cerebral organization of language capacities. A review of the literature].

Models on the cerebral organisation of speech and language capacities are predominantly based on lesion studies. Neuroradiological activation methods using positron emission or magnetic resonance tomography provide a further means to investigate brain-behaviour relationships. The present paper reviews the available data obtained with functional imaging during speech and language tasks. The classical connectionist model suggests several distinct language centres within the perisylvian area of the dominant hemisphere. Especially the processing of complex verbal stimuli yields haemodynamic and metabolic reactions outside this area. At least partially, these extrasylvian foci might reflect paralinguistic functions such as motivational or attentional aspects of speech production, or the processing of emotions conveyed by verbal utterances. As far as linguistic capacities are concerned, functional imagery has yielded two results which extend the classical connectionist model of speech and language functions: (a) the medial part of the occipital lobe of the dominant hemisphere seems to comprise representations of visual word forms; (b) word generation yields activation of cerebellar structures. In contrast to the classical connectionist model, reading did not cause reactions of the angular region of the left hemisphere. Furthermore, phonological and semantic processing of verbal stimuli include the anterior perisylvian language zones. The interpretation of discrepancies between data derived from lesion studies and those obtained with functional imaging is still unsettled. First of all, rapid cognitive processes do not necessarily give rise to a detectable significant haemodynamic or metabolic response. Secondly, highly automatised language processes such as inner speech are difficult to control.

Brain↗
PubMed1997

Fractal dimension of sustained vowel productions in neurological dysphonias: an acoustic and electroglottographic analysis.

In order to investigate whether nonlinear methods of signal analysis provide a measure of phonatory irregularities in neurogenic voice disorders, the present study computed the fractal dimension (D) both of the electroglottographic (EGG) and the acoustic signal of sustained vowel productions obtained from patients with Parkinson's disease (PD) and cerebellar atrophy (CA). Compared with normal speakers, the female PD group as well as the male and female CA patients showed an increased dimension (D) of the EGG. The dimensional complexity of the acoustic signal largely depended on vowel type. Furthermore, the dimension of the acoustic signal was reduced in male PD patients as compared to the respective controls.

Brain↗
PubMed1997

Articulatory control of phonological vowel length contrasts: kinematic analysis of labial gestures.

The present study investigated the articulatory control of the German vowel quantity contrast, i.e., the phonological difference between short and long vowels. By means of an optoelectronic system the excursions of the compound lower lip/jaw opening and closing gestures were measured during production of test sentences comprising the target sequence /pVp/ (V = /a/, /i/, /u/, /a:/, /i:/, /u:/). First, a highly linear relationship between peak velocity and movement amplitude emerged within each quantity class. Second, vowel quantity systematically influenced the scaling of velocity and amplitude during oral opening. Third, as compared to their short counterparts, long vowels showed an increased peakedness of the velocity profile. Finally, the velocity profiles of the long vowels were characterized by an asymmetric shape in terms of a prolonged deceleration phase of the opening and a lengthened acceleration interval of the closing movement. With respect to durational coarticulation patterns, the control of vowel quantity clearly differed from intrinsic, i.e., vowel type-induced, variability. The latter was partially compensated for the level of word duration by shortening of the prevocalic consonant whereas vowel quantity turned out to be primarily due to the lengthening of the syllable /pV/.

Adult↗
PubMed1997

Influence of selegiline and lipoic acid on the life expectancy of immunosuppressed mice.

Ten groups of 14 immunosuppressed NMRI-mice (nu/nu) were raised and kept under germ-reduced conditions. The control animals were fed a germ-reduced diet, nine other groups received the same diet with selegiline (CAS 14611-51-9, Deprenyl) or lipoic acid (thioctic acid, CAS 62-46-4) admixed at various amounts. The 50% survival rate, the total life span of each group and the areas under the curves were determined to evaluate life expectancy as compared to the controls. The racemate of lipoic acid at high dosage (350 mg/kg body weight) reduced the life span significantly. The S(-)-enantiomer of lipoic acid (75 mg/kg body weight) increased the 50% survival rate, whereas the physiologic R(+)-enantiomer (9 mg/kg body weight) expanded the total life span of its group. Alteration of only one out of three parameters was not considered significant. All other groups except for one did not differ from controls: only animals which obtained 75 micrograms selegiline per kg of body weight and per day exerted increased life expectancies by all three parameters. This group exhibited also in statistical evaluation a significantly (p < 0.05) prolongated survival time up to about 200% as compared to the control animals.

Animals↗
PubMed1996

Functional lateralization of speech production at primary motor cortex: a fMRI study.

To evaluate lateralization of speech production at the level of the Rolandic cortex, functional magnetic resonance imaging (1.5 Tesla, 27 parallel axial slices, EPI-technique) was performed during a speech task (continuous silent recitation of the names of the months of the year). As control conditions, non-speech tongue movements and silent singing of a well-known melody with the syllable 'la' as its carrier were considered. Tongue movements produced symmetrical activation at the lower primary motor cortex. During automatic speech a strong functional lateralization to the left hemisphere emerged within the same area. In contrast, singing yielded a predominant right-sided activation of the Rolandic region. Functional lateralization of speech production therefore seems to include the precentral gyrus as well as Broca's area.

Adult↗