Biomedical subjects

H Ackermann

Publications and source records attributed to H Ackermann.

At least 19 recordsLinked to original sources

PubMed2002

Dynamic brain activation during processing of emotional intonation: influence of acoustic parameters, emotional valence, and sex.

Appreciation of the emotional tone of verbal utterances represents an important aspect of social life. It is still unsettled, however, which brain areas mediate processing of intonational information and whether the presumed right-sided superiority depends upon acoustic properties of the speech signal. Functional magnetic resonance imaging was used to disentangle brain activation associated with (i) extraction of specific acoustic cues and (ii) detection of specific emotional states. Stimulus material comprised pairs of emotionally intonated utterances, exclusively differing either in pitch range or in the length of stressed vowels. Hemodynamic responses showed a dynamic pattern of cerebral activation including sequenced bilateral responses of various cortical and subcortical structures. Activation associated with discrimination of emotional expressiveness predominantly emerged within the right inferior parietal lobule, within the bilateral mesiofrontal cortex and--with an asymmetry toward the right hemisphere--at the level of bilateral dorsolateral frontal cortex. Lateralization did not depend upon acoustic structure or emotional valence of stimuli. These findings might prove helpful in reconciling the controversial previous clinical and experimental data.

Adult↗

PubMed2002

[Significance of arterial hypertension in geriatric prevention].

In Germany for decades the assessment and treatment of patients with high blood pressure is not satisfactory. As in other industrial countries only approximately 50% of hypertensive men and 60% of hypertensive women are diagnosed. Arterial hypertension bears the known risks on heart and vascular system also in old age when often target organ damages are already present. A sufficient number of clinical studies proves risk reduction by blood pressure lowering treatment. According to the criteria of WHO in old age the same limits of normal blood pressure and the same stages of the disease are valid as in younger patients. The probability of cardiovascular complications increases with the height of blood pressure. As small increases of blood pressure are far more prevalent than very high blood pressure values the cumulative risk in populations is predominantly linked to mild hypertension. In elderly patients systolic blood pressure has a better predictive value than diastolic blood pressure. A short review is given of work up and treatment of hypertension in the elderly instructed by the Guidelines of the German Hypertension Society.

Aged↗

PubMed2002

The coexpression of the apoptosis-related genes bcl-2 and wt1 in predicting survival in adult acute myeloid leukemia.

The Wilms tumor gene wt1 and the protooncogene bcl-2 are upregulated in acute myeloid leukemia (AML) and are known to regulate or to inhibit the onset of apoptosis. Since wt1 has been shown to regulate the expression of bcl-2, we investigated the association of the expression of these genes and their prognostic relevance in AML. Leukemic blasts from the bone marrow of 152 patients with newly diagnosed AML were analyzed for bcl-2 and wt1 mRNA expression using RT-PCR and quantitative PCR. Therapy outcome was correlated with the level of bcl-2 and wt1 transcripts. Bcl-2-specific mRNA was detectable in 127/152 (84%) patients and wt1 mRNA in 113/152 (74%) patients with AML. In monocytic subtypes the frequency of bcl-2 and wt1 transcripts was significantly lower. The expression of bcl-2 mRNA was correlated significantly with that of wt1 mRNA (P < 0.0001). In AML patients <60 years, high expression of bcl-2 and wt1 was associated with a reduced rate of continuing complete remission (CCR, P = 0.002 and P = 0.005, respectively) and increased death rate (P = 0.0002 and P = 0.04, respectively) in contrast to patients >60 years, where the expression of bcl-2 or wt1 had no prognostic impact. Based on the coexpression of bcl-2 and wt1, we established a prognostic model defining three risk groups with significant differences in CCR rate (P = 0.01), overall survival (P < 0.04) and disease-free survival (P < 0.03). Thus, bcl-2 and wt1 mRNA expression are associated with response and long-term outcome in AMLs. The coexpression of these genes allows determination of prognostic groups with high predictive value for overall and disease-free survival.

Acute Disease↗

PubMed2001

Rate-dependent activation of a prefrontal-insular-cerebellar network during passive listening to trains of click stimuli: an fMRI study.

Eight volunteers underwent fMRI during passive listening to click trains. Using a parametric approach, rate-response profiles across the frequency band considered (2-6 Hz) were determined. Several cerebral structures outside the central-auditory pathways and target areas displayed distinct activation patterns each: rate-response profiles resembling high-pass (left side) or low-pass filtered (right side) signal series emerged at the level of the anterior insula, band-pass like characteristics (center frequency: 3-4 Hz) were observed within the left inferior frontal gyrus, and click train rates > 4 Hz yielded enhanced activation of the right cerebellar hemisphere. A variety of clinical and experimental data indicate that the left and right cerebral hemispheres act as high- and low-pass filters, respectively, on auditory input (double filtering by frequency theory). In light of the present fMRI data, the anterior insula contributes to the assumed double filtering by frequency functions. Furthermore, these intrasylvian areas seem to join up with the right cerebellum and the left inferior frontal gyrus to a network subserving parsing/timing functions within the auditory-verbal domain.

Acoustic Stimulation↗

PubMed2001

Contralaterality of cortical auditory processing at the level of the M50/M100 complex and the mismatch field: a whole-head magnetoencephalography study.

Humans show a stronger cortical representation of auditory input at the opposite hemisphere each. To specify the temporal aspects of this contralaterality effect within the domain of speech stimuli, the present study recorded a series of evoked magnetic fields (M50, M100, mismatch field) subsequent to monaural application of stop consonant-vowel syllables using whole-head magnetoencephalography (MEG). The M50 components exhibited a skewed shape of cross-symmetrical distribution in terms of an initial maximum peak succeeded by a knot over the contralateral and a reversed pattern over the ipsilateral temporal lobe. Most presumably, this pattern of evoked fields reflects two distinct stages of central-auditory processing: (a) initial excitation of the larger contralateral and the smaller ipsilateral projection area of the stimulated ear; (b) subsequent transcallosal activation of the residual neurons, i.e. the targets of the non-stimulated ear, at either side. Previous studies using non-speech stimuli found contralaterality of central-auditory processing to extend to the M100 field. In contrast, a larger amplitude of ipsilateral M100 as compared to the respective opposite deflection emerged after stimulation of either ear. Finally, the computed magnetic analogues of mismatch negativity failed any significant laterality effects. These data provide first evidence for a distinct pattern of hemispheric differences at the level of the M50/M100 complex subsequent to monaural application of speech stimuli.

Acoustic Stimulation↗

PubMed2001

Neural correlates of duplex perception: a whole-head magnetencephalography study.

Simultaneous experience of the same acoustic stimulus in two distinct phenomenological modes, e.g. as a speech-like and as a non-speech event, is referred to as duplex perception (DP). The most widely investigated DP paradigm splits each of the stop consonant-vowel (CV) syllables /ga/ and /da/ into an isolated formant transient (chirp) and the remaining sound structure (base). The present study recorded mismatch fields in response to a series of dichotically applied base and chirp components using whole-head magnetencephalography (MEG). Preattentive mismatch fields showed larger amplitudes in response to contralateral deviants. During attention to the fused percept /da/, the left ear deviants chirps elicited an enhanced and posteriorly shifted dipole field over the ipsilateral hemisphere. These data provide first neurophysiological evidence that the integration of acoustic stimulus elements into a coherent syllable representation constitutes a distinct stage of left-hemisphere speech sound encoding.

Acoustic Stimulation↗

PubMed2001

Differential contributions of motor cortex, basal ganglia, and cerebellum to speech motor control: effects of syllable repetition rate evaluated by fMRI.

In order to delineate the neuroanatomical correlates of speech motor control, functional magnetic resonance imaging was performed during silent repetitions of the syllable "ta" at three different rates (2.5, 4.0, and 5.5 Hz). Spatial extent and magnitude of hemodynamic responses at the level of the motor cortex showed a positive correlation to production frequencies. As concerns the basal ganglia, the lower rates (2.5 and 4.0 Hz) gave rise to higher magnitudes of activation within the left putamen as compared to the 5.5 Hz condition. In contrast, cerebellar responses were rather restricted to fast performance (4.0 and 5.5 Hz) and exhibited a shift in caudal direction during 5.5 as compared to 4.0 Hz. These findings corroborate the suggestion of a differential impact of various cortical and subcortical areas on speech motor control.

Adult↗

PubMed2001

Determination of heparin-platelet factor 4-IgG antibodies improves diagnosis of heparin-induced thrombocytopenia.

Only a few patients with heparin-induced antibodies develop heparin-induced thrombocytopenia (HIT). In this study, we investigated whether different immunglobulin classes can be used to differentiate between antibody-positive patients with and without HIT. Four different patient populations were investigated: 32 patients with the immune type of HIT with thromboembolic complications, 13 patients with HIT without thromboembolism, 24 patients with heparin-platelet factor 4 (PF4) antibodies without clinical symptoms of HIT, and 20 heparin-treated patients with thrombocytopenia caused by other reasons. In all patients the immunglobulin mixture of IgG, IgM and IgA, and the single immunglobulin classes of heparin-PF4 antibodies, were investigated. No significant differences between HIT patients with thromboembolic complications and patients with isolated HIT were found concerning the different immunglobulin classes. Antibody-positive patients with HIT had significantly higher levels of IgG antibodies than those without HIT (P < 0.05), while they did not differ concerning IgM and IgA antibodies. By determining IgG antibodies, the specificity of the enzyme-linked immunosorbent assay (ELISA) system was increased without loss of sensitivity. Heparin-PF4-IgG antibodies can identify patients at risk of developing life-threatening HIT. Future ELISAs should only include this immunglobulin class, as the determination of the antibody mixture may lead to overestimation of HIT.

Aged↗

PubMed2000

Differential impact of periodic and aperiodic speech-like acoustic signals on magnetic M50/M100 fields.

Voiced and unvoiced sounds, characterized by a periodic or aperiodic acoustic structure, respectively, represent two basic information-bearing elements of the speech signal. Using whole-head magnetencephalography (MEG), magnetic fields (M50/M100) in response to synthetic vowel-like as well as noise-like signals matched in spectral envelope were recorded in 20 subjects. Aperiodic events gave rise to increased M50 concomitant with reduced M100 activity as compared to their periodic cognates. Attention toward the auditory channel enhanced the effects of signal periodicity. These data provide first evidence that speech-relevant acoustic features differentially affect evoked magnetic fields as early as the M50 component. Conceivably, the M50 field reflects an ongoing monitoring process whereas the M100 component is bound to more specific operations such as detection of signal periodicity.

Acoustic Stimulation↗

PubMed2000

Right-hemisphere dominance for the processing of sound-source lateralization.

Cortical processing of change in direction of a perceived sound source was investigated in 12 human subjects using whole-head magnetoencephalography. The German word "da" was presented either with or without 0.7 msec interaural time delays to create the impression of right- or left-lateralized or midline sources, respectively. Midline stimuli served as standards, and lateralized stimuli served as deviants in a mismatch paradigm. Two symmetrically linked dipoles fitted to the mismatch fields showed stronger moments in the hemisphere contralateral to the side of the deviant. The right dipole displayed equal latencies to both left and right deviants, whereas left dipole latencies were longer for ipsilateral than contralateral deviants. Frequency analysis between 20-70 Hz and statistical probability mapping revealed increased induced gamma-band activity at 53+/-2.5 Hz to both types of deviants. Right deviants elicited spectral amplitude enhancements in this frequency range, peaking at latencies of 160 and 240 msec. These effects were localized bilaterally over the angular gyri and posterior temporal regions. Coherence analysis suggested the existence of two separate interhemispheric networks. For left-lateralized deviants, both spectral amplitude enhancements at 110 and 220 msec and coherence increases were restricted to the right hemisphere. In conclusion, both mismatch dipole latencies at the supratemporal plane and gamma-band activity in posterior parietotemporal areas suggested a right hemisphere engagement in the processing of bidirectional sound-source shifts. In contrast, left-hemisphere regions responded predominantly to contralateral events. These findings may help to elucidate phenomena such as unilateral auditory neglect.

Acoustic Stimulation↗

PubMed2000

Opposite hemispheric lateralization effects during speaking and singing at motor cortex, insula and cerebellum.

Aside from spoken language, singing represents a second mode of acoustic (auditory-vocal) communication in humans. As a new aspect of brain lateralization, functional magnetic resonance imaging (fMRI) revealed two complementary cerebral networks subserving singing and speaking. Reproduction of a non-lyrical tune elicited activation predominantly in the right motor cortex, the right anterior insula, and the left cerebellum whereas the opposite response pattern emerged during a speech task. In contrast to the hemodynamic responses within motor cortex and cerebellum, activation of the intrasylvian cortex turned out to be bound to overt task performance. These findings corroborate the assumption that the left insula supports the coordination of speech articulation. Similarly, the right insula might mediate temporo-spatial control of vocal tract musculature during overt singing. Both speech and melody production require the integration of sound structure or tonal patterns, respectively, with a speaker's emotions and attitudes. Considering the widespread interconnections with premotor cortex and limbic structures, the insula is especially suited for this task.

Adult↗

PubMed2000

Articulatory/phonetic sequencing at the level of the anterior perisylvian cortex: a functional magnetic resonance imaging (fMRI) study.

Damage to the anterior peri-intrasylvian cortex of the dominant hemisphere may give rise to a fairly consistent syndrome of articulatory deficits in the absence of relevant paresis of orofacial or laryngeal muscles (apraxia of speech, aphemia, or phonetic disintegration). The available clinical data are ambiguous with respect to the relevant lesion site, indicating either dysfunction of the premotor aspect of the lower precentral gyrus or the anterior insula in the depth of the Sylvian fissure. In order to further specify the functional anatomic substratum of this syndrome, functional magnetic resonance imaging (fMRI) was performed during reiteration of syllables differing in their demands on articulatory/phonetic sequencing (CV versus CCCV versus CVCVCV). Horizontal tongue movements and a polysyllabic lexical item served as control conditions. Repetition of the CV and CCCV monosyllables elicited a rather bilateral symmetric hemodynamic response at the level of the anterior and posterior bank of the central sulcus (primary sensorimotor cortex), whereas a more limited area of neural activity arose within this domain during production of lexical and nonlexical polysyllables, significantly or exclusively lateralized toward the left hemisphere. There is neurophysiological evidence that primary sensorimotor cortex mediates the "fractionation" of movements. Assuming that the polysyllables considered are organized as coarticulated higher-order units, the observed restricted and lateralized cortical activation pattern, most presumably, reflects a mode of "nonindividualized" motor control posing fewer demands on "movement fractionation." These findings may explain the clinical observation of disproportionately worse repetition of trisyllabic items as compared to monosyllables in apraxia of speech. The various test materials failed to elicit significant activation of the anterior insula. If at all, only horizontal tongue movements yielded a hemodynamic reaction extending beyond the sensorimotor cortex to premotor areas. Since limbic projections target the inferior dorsolateral frontal lobe, the enlarged region of activation during horizontal tongue movements might reflect increased attentional requirements of this task.

Adult↗

PubMed2000

Encoding of temporal speech features (formant transients) during binaural and dichotic stimulus application: a whole-head magnetencephalography study.

Spoken-word recognition depends upon the encoding of relevant 'information bearing elements' of the acoustic speech signal. For example, relatively rapid shifts of spectral energy distribution (formant transients) cue the perception of stop consonant-vowel (CV) syllables such as /ba/, /ga/, and /da/. A variety of data indicate left-hemisphere superiority with respect to the processing of formant transients. To further delineate the underlying neurophysiological mechanisms, evoked cortical fields in response to CV syllables (oddball design; frequent stimulus=binaural /ga/; four deviant constellations: Binaural /ba/, binaural /da/, left /da/ (left ear deviant)-right /ga/, right /da/ (right ear deviant)-left /ga/) were recorded by means of whole-head magnetencephalography (MEG; 151 channels) under two different conditions of attentional demands (visual distraction versus reaction to prespecified stimuli). (a) During binaural stimulus presentation attention toward target events resulted in a significantly enhanced mismatch field (MMNm, magnetic analogue to the mismatch negativity) over the left as compared to the right hemisphere. In contrast, preattentive processing of the CV syllables failed MMNm lateralization effects. (b) Dichotic application of /da/ elicited a larger contralateral MMNm amplitude in subjects with right ear advantage (REA) at behavioral testing. In addition, right ear deviants yielded a stronger ipsilateral response than the left ear cognates. Taken together, these data indicate bilateral preattentive processing and subsequent attention-related predominant left-hemisphere encoding of formant transients at the level of the supratemporal plane. Furthermore, REA during dichotic application of CV syllables seems to be linked to functional dissociation of the two hemispheres during auditory processing.

Acoustic Stimulation↗

PubMed2000

Cortical activation patterns of affective speech processing depend on concurrent demands on the subvocal rehearsal system. A DC-potential study.

In order to delineate brain regions specifically involved in the processing of affective components of spoken language (affective or emotive prosody), we conducted two event-related potential experiments. Cortical activation patterns were assessed by recordings of direct current components of the EEG signal from the scalp. Right-handed subjects discriminated pairs of declarative sentences with either happy, sad or neutral intonation. Each stimulus pair was derived from two identical original utterances that, due to digital signal manipulations, slightly differed in fundamental frequency (F0) range or in duration of stressed syllables. In the first experiment, subjects were asked: (i) to denote the original emotional category of each sentence pair and (ii) to decide which of the two items displayed stronger emotional expressiveness. Participants in the second experiment were asked to repeat the utterances using inner speech during stimulus presentation in addition to the discrimination task. In the absence of inner speech, a predominant activation of right frontal regions was observed, irrespective of emotional category. In the second experiment, a bilateral activation with left frontal preponderance emerged from discrimination during additional performance of inner speech. Compared with the first experiment, a new pattern of acoustic signal processing arose. A relative decrease of brain activity during processing of F0 stimulus variants was observed together with increased activation during discrimination of duration-manipulated sentence pairs. Analysis of behavioural data revealed no significant differences in evaluation of expressiveness between the two experiments. We conclude that the topographical shift of cortical activity originates from left hemisphere (LH) mechanisms of speech processing that centre around the subvocal rehearsal system as an articulatory control component of the phonological loop. A strong coupling of acoustic input and (planned) verbal output channel in the LH is initiated by subvocal articulatory activity like inner speech. These neural networks may provide interpretations of verbal acoustic signals in terms of motor programs and facilitate continuous control of speech output by comparing the signal produced with that intended. Most likely, information on motor aspects of suprasegmental signal characteristics contributes to the evaluation of affective components of spoken language. In consequence, the right hemisphere (RH) holds a merely relative dominance, both for processing of F0 and for evaluation of emotional significance of sensory input. Psychophysically, an important determinant on expression of lateralization patterns seems to be given by the degree of communicative demands such as solely perceptive (RH) or perceptive and verbal-expressive (RH and LH).

Adult↗

PubMed2000

Lip-jaw and tongue-jaw coordination during rate-controlled syllable repetitions.

The present study investigated the relationship between functionally relevant compound gestures and single-articulator component movements of the jaw and the constrictors lower lip and tongue tip during rate-controlled syllable repetitions. In nine healthy speakers, the effects of speaking rate (3 vs 5 Hz), place of articulation, and vowel type during stop consonant-vowel repetitions (/pa/, /pi/, /ta/, /ti/) on the amplitude and peak velocity of differential jaw and constrictor opening-closing movements were measured by means of electromagnetic articulography. Rather than homogeneously scaled compound gestures, the results suggest distinct control mechanisms for the jaw and the constrictors. In particular, jaw amplitude was closely linked to vowel height during bilabial articulation, whereas the lower lip component amplitude turned out to be predominantly rate sensitive. However, the observed variability across subjects and conditions does not support the assumption that single-articulator gestures directly correspond to basic phonological units. The nonhomogeneous effects of speech rate on articulatory subsystem parameters indicate that single structures are differentially rate sensitive. On average, an increase in speech rate resulted in a more or less proportional increase of the steepness of peak velocity/amplitude scaling for jaw movements, whereas the constrictors were less rate sensitive in this respect. Negative covariation across repetitions between jaw and constrictor amplitudes has been considered an indicator of motor equivalence. Although significant in some cases, such a relationship was not consistently observed across subjects. Considering systematic sources of variability such as vowel height, speech rate, and subjects, jaw-constrictor amplitude correlations showed a nonhomogeneous pattern strongly depending on place of articulation.

Analysis of Variance↗

PubMed2000

Characterisation of patients with primary biliary cirrhosis responding to long term ursodeoxycholic acid treatment.

BACKGROUND: In some patients with primary biliary cirrhosis, ursodeoxycholic acid causes full biochemical normalisation of laboratory data; in others, indexes improve but do not become normal. AIMS: To characterise complete and incomplete responders. METHODS: Seventy patients with primary biliary cirrhosis were treated with ursodeoxycholic acid 10-15 mg/kg/day and followed up for 6-13 years. RESULTS: In 23 patients (33%) with mainly stage I or II disease, cholestasis indexes and aminotransferases normalised within 1-5 years, except for antimitochondrial antibodies. Histological findings improved. Indexes were not normalised in 47 patients (67%) although the improvement of their biochemical functions parallelled the trend in the first group. In these incomplete responders histological findings improved to a lesser extent. The only difference between the two groups before treatment was higher levels of alkaline phosphatase and gamma glutamyl transpeptidase in the incomplete responders. At onset of treatment the discriminant value separating responders from incomplete responders was 660 U/l for alkaline phosphatase and 131 U/l for gamma glutamyl transpeptidase. One year later it was 239 and 27 U/l (overall predictive value for responders 92%, for incomplete responders 81%). There were no differences between the two groups concerning immune status, antimitochondrial antibody subtypes, liver histology, or any other data. HLA-B39, DRB1*08, DQB1*04 dominated in both groups. CONCLUSIONS: In patients with mainly early stages of primary biliary cirrhosis, higher values of alkaline phosphatase and gamma glutamyl transpeptidase are the only biochemical indexes which allow discrimination between patients who will completely or incompletely respond to ursodeoxycholic acid treatment.

Adult↗

PubMed1999

Preattentive processing of consonant vowel syllables at the level of the supratemporal plane: a whole-head magnetencephalography study.

A variety of clinical and experimental data indicate superiority of the left hemisphere with respect to the encoding of dynamic aspects of the acoustic speech signal such as formant transients, i.e., fast changes of spectral energy distribution across a few tens of milliseconds, which cue the perception of stop consonant vowel syllables. Using an oddball design, the present study recorded auditory evoked magnetic fields by means of a whole-head device in response to vowels as well as syllable-like structures. Both the N1m component (=the magnetic equivalent to the N1 response of the electroencephalogram (EEG)) and various difference waves between the magnetic fields to standard and respective rare events (MMNm=magnetic mismatch negativity) were calculated. (a) Vowel mismatch (/a/ against /e/) resulted in an enlarged N1m amplitude reflecting, most presumably, peripheral adaptation processes. (b) As concerns lateralized responses to syllable-like structures, only the shortest transient duration (=10 ms) elicited a significantly enhanced MMNm at the left side. Conceivably, the observed hemispheric difference contributes to prelexical parsing of the auditory signal rather than the encoding of linguistic categories.

Adult↗

PubMed1999

Phonemic vowel length contrasts in cerebellar disorders.

Apraxia of speech and Broca's aphasia both affect voice onset time (VOT) whereas phonemic vowel length distinctions seem to be preserved. Assuming a close cooperation of anterior perisylvian language zones and the cerebellum with respect to speech timing, a similar profile of segment durations must be expected in ataxic dysarthria. In order to test this hypothesis, patients with cerebellar atrophy or cerebellar ischemia were asked to produce sentence utterances including either one of the German lexial items "Rate" (/ra:t(h)e/, 'installment'), "Ratte" (/rat(h)e/, 'rat'), "Gram" (/gra:m/, 'grief'), "Gramm" (/gram/, 'gramm'), "Taten" (/t(h)atn/, 'actions'), or "Daten" (/datn/, 'data'). At the acoustic signal, the duration of the target vowels /a/ and /a:/ as well as the VOT of the word-initial alveolar stops /d/ and /t/ were determined. In addition, a master tape comprising the target words from patients and controls in randomized order was played to three listeners for perceptual evaluation. In accordance with a previous study, first, the cerebellar subjects presented with a reduced categorical separation of the VOT of voiced and unvoiced stop consonants. Second, vowel length distinctions were only compromised in case of the minimal pair "Gram"/"Gramm." In contrast to "Rate"/"Ratte", production of the former lexical items requires coordination of several orofacial structures. Disruption of vowel length contrasts would, thus, depend upon the complexity of the underlying articulatory pattern.

Adult↗