Biomedical subjects

Volker Gall

Publications and source records attributed to Volker Gall.

5 recordsLinked to original sources

PubMed2005

Cortical plasticity associated with stuttering therapy.

UNLABELLED: Neuroimaging studies have indicated that persistent developmental stuttering (PDS) may be associated both with an abnormality in white matter of left-hemispheric speech areas and a right-hemispheric hyperactivity. The latter may compensate for the deficient structural connectivity in the left hemisphere. To investigate the effects of stuttering therapy on brain activity nine male adults with PDS underwent functional magnetic resonance imaging (fMRI) before and within 12 weeks after fluency shaping therapy. Brain response differences during overt sentence reading before and after therapy were assessed by utilizing random effects analyses. After therapy, a more widespread activation was observed in frontal speech and language regions and temporal areas of both hemispheres, particularly and more pronounced on the left side. Interestingly, distinct posttreatment left-sided activation increases were located directly adjacent to a recently detected area of white matter anomaly [M. Sommer, M.A. Koch, W. Paulus, C. Weiller, C. Buchel (2002). Disconnection of speech-relevant brain areas in persistent developmental stuttering. The Lancet, 360, 380-383] suggesting that fluency shaping techniques reorganize neuronal communication between left-sided speech motor planning, motor execution, and temporal areas. Hence, a therapeutic mechanism can be assumed to remodel brain circuitry close to the source of the dysfunction instead of reinforcing compensation via homologous contralateral brain networks. EDUCATIONAL OBJECTIVES: The reader will learn about and be able to: (1) describe brain activation changes detected shortly after fluency-shaping therapy; (2) identify left-hemispheric regions where a (re)functionalization after fluency-shaping therapy seems to occur adjacent to a recently described abnormal white matter region in PDS subjects; and (3) discuss how an effective cerebral compensation mechanism for stuttering could work.

Adult↗

PubMed2004

Immunogenicity of pneumococcal vaccination of patients with cochlear implants.

BACKGROUND: Pneumococcal meningitis is a rare but potentially fatal complication of cochlear implantation. METHODS: A prospective study was conducted of the immunogenicity of pneumococcal vaccination in 174 patients with cochlear implants (CIs). The cohort was divided into groups of patients with impaired hearing due to meningitis (P(1)), cranial malformations (P(2)), or an unknown cause (P(3)) and was stratified by age as follows: <2 years (A(1)), 2-5 years (A(2)), and >5 years (A(3)). We determined immunoglobulin (Ig) levels for IgG subclasses 1-4 and serum concentrations of antibodies against pneumococci before and 4-6 weeks after vaccination. Group A(1) received the 7-valent pneumococcal conjugate vaccine (PCV-7), group A(2) received PCV-7 or the 23-valent pneumococcal polysaccharide vaccine (PPV-23), and group A(3) received PPV-23. RESULTS: IgG, IgM, and IgG1 levels were significantly lower in group P(1), compared with the other patient groups and with historic data for healthy control subjects, suggesting a decreased antibody response. Group P(1) had lower levels of pneumococcal antibodies, compared with groups P(2) and P(3) before vaccination (P<.05, pneumococcal serotypes 4 and 9V). Irrespective of the underlying condition, all patients showed a sufficient antibody response after 1 dose of vaccine. In children 2-5 years of age, PCV-7 was significantly more immunogenic than PPV-23. CONCLUSIONS: PCV-7 should be administered to all CI recipients younger than 6 years and older than 6 years who are at an increased risk for bacterial meningitis. CI recipients with a history of bacterial meningitis should undergo immunological evaluation.

Adolescent↗

PubMed2003

The nature and treatment of stuttering as revealed by fMRI A within- and between-group comparison.

UNLABELLED: This article reviews some of our recent functional magnetic resonance imaging (fMRI) studies of stuttering. Using event-related fMRI experiments, we investigated brain activation during speech production. Results of three studies comparing persons who stutter (PWS) and persons who do not stutter (PWNS) are outlined. Their findings point to a region in the right frontal operculum (RFO) that was consistently implicated in stuttering. During overt reading and before fluency shaping therapy, PWS showed higher and more distributed neuronal activation than PWNS. Immediately after therapy differential activations were even more distributed and left sided. They extended to frontal, temporal, and parietal regions, anterior cingulate, insula, and putamen. These over-activations were slightly reduced and again more right sided two years after therapy. Left frontal deactivations remained stable over two years of observation, and therefore possibly indicate a dysfunction. After therapy, we noted higher activations in persons who stutter moderately than in those who stutter severely. These activations might reflect patterns of compensation. We discuss why these findings suggest that fluency-inducing techniques might synchronize a disturbed signal transmission between auditory, speech motor planning, and motor areas. EDUCATIONAL OBJECTIVES: The reader will learn about and be able to: (1) identify regions of brain activations and deactivations specific for PWS; (2) describe brain activation changes induced by fluency shaping therapy; and (3) discuss the correlation between stuttering severity and brain activation.

Adult↗

PubMed2003

A new method to record subglottal pressure waves: potential applications.

Rapid subglottal pressure changes related to the glottal cycles influence the aerodynamics of phonation. Various methods to measure these have been developed, but are not practical for routine phoniatric use. For that reason, a noninvasive measurement tool is necessary. This article presents a technique that uses a microphone positioned at the skin of the jugular fossa to record the signal which arises in the subglottal spaces and is transmitted through the soft tissue to the surface of the skin. Using the program Glottal Segmentation of Voice and Speech, jugular microphone recordings from two healthy subjects were compared with simultaneously recorded direct intratracheal measurements during the same phonation. A systematic error arising from the transmission properties of the microphone and the soft tissue leads to phase and amplitude deviations. These must be taken into account and require correction. This correction procedure leads to high correlations and a good agreement between the two signals. Even without this correction the jugular microphone measurements proved to be useful as a diagnostic and a therapeutic tool in cases where chest resonance specific processes appear affected. In addition, they offer material for research purposes. Although based on a small number of subjects, the new method shows a good validity; testing on a larger number of subjects will probably strengthen the validity.

Adult↗

PubMed2003

Event-related fMRI for the suppression of speech-associated artifacts in stuttering.

The purpose of this study was to establish functional magnetic resonance imaging (fMRI) for the investigation of brain function during overt speech production in stuttering. Up to now this technique has rarely been used for the investigation of speech production paradigms because artifacts related to overt speaking largely impair the sensitivity toward task-related activation. Recently, the temporal delay of the hemodynamic response has been exploited to achieve a suppression of speech-related artifacts. By the limitation to very short utterances (one word), a temporal segregation of the respective effects was accomplished by means of an event-related experimental design. However, the investigation of speech production in persons who stutter requires a more extensive speaking situation. Since longer and more complex utterances evoke more symptoms of stuttering than reading of single words, a useful task should at least include the reading of full sentences. In this study we performed simulations to investigate the correlation of speech-related artifacts with the respective hemodynamic response in dependency on speech duration and rate of data sampling. Furthermore, we show that prolonged stimulus durations and repetition times of 3 s still allow an effective suppression of speech-related artifacts in fluent as well as in nonfluent speakers. Not only were obvious false activations at high contrast cerebrospinal fluid tissue borders widely eliminated, subjects also displayed consistent activation in speech-related and motor areas. As these results widely resemble those obtained by earlier neuroimaging studies on language production, event-related fMRI seems to be capable of recording neurophysiological correlates of overt speech production.

Adult↗