Papers by Hermann Ackermann
Gender-Specific Vocal Dysfunctions in Parkinson's Disease: Electroglottographic and Acoustic Analyses
Annals of Otology, Rhinology & Laryngology, 1995
Electroglottographic (EGG) and acoustic recordings were obtained during sustained vowel productio... more Electroglottographic (EGG) and acoustic recordings were obtained during sustained vowel production in men and women suffering from Parkinson's disease (PD). The computed EGG spectrograms allowed us to differentiate various kinds of phonatory disturbances: intervals with subharmonic energy (“low-frequency segments”), “noise-like regions,” and abrupt shifts of fundamental frequency (F0). Female PD subjects presented with a significantly increased portion of subharmonic segments and with significantly more abrupt F0 shifts as compared to both controls and male PD subjects. Presumably, these alterations in spectral energy distribution reflect different oscillatory modes of the glottal source. Thus, PD seems to have a differential impact on phonation in men and women. Conceivably, these gender-specific vocal dysfunctions are determined by the well-known sexual dimorphism of laryngeal size.
Prosodische St�rungen bei neurologischen Erkrankungen - eine Literatur�bersicht
Fortschr Neurol Psychiat, 1993
Folia Phoniatrica et Logopaedica, 2001
We tested the applicability of the Goettinger Hoarseness Diagram (GHD) for quantitative evaluatio... more We tested the applicability of the Goettinger Hoarseness Diagram (GHD) for quantitative evaluation of voice disorders after severe traumatic brain injury (TBI) and compared the obtained data with those from established voice analysis systems such as the Multi-Dimensional Voice Program (MDVP), electroglottography (EGG) and perceptual ratings using sustained vowel productions from 10 patients with TBI dysarthrophonia at late stages postinjury and of 10 healthy control speakers. Statistical analyses revealed significant intergroup differences with respect to various acoustic and perceptual measures, i.e., irregularity component, noise component, noise-to-harmonic ratio, shimmer, jitter, roughness, creakiness, strained-strangledness, hypernasality. By contrast, the considered EGG estimates, i.e., open quotient and speed quotient, did not allow for separation of patients and controls. In addition, the two GHD components exhibited close correlations to perceived roughness and creakiness, ...
Articulatory Deficits in Parkinson’s and Huntington’s Disease: An Acoustic Analysis
Advances in Behavioral Biology, 1995
Investigations of rapid voluntary activity of distal upper limb muscles have demonstrated common ... more Investigations of rapid voluntary activity of distal upper limb muscles have demonstrated common motor deficits, e.g. bradykinesia and delayed transition between movements, in Huntington’s (HD) and Parkinson’s disease (PD).1 Since both striatal disorders may give rise to speech motor disturbances, the question emerges whether HD and PD dysarthria are characterized by similar articulatory deteriorations as well.
Processing of dynamic aspects of speech and non-speech stimuli: a whole-head magnetoencephalography study
Cognitive Brain Research, 2003
Clinical and experimental data indicate higher proficiency of the left hemisphere in encoding dyn... more Clinical and experimental data indicate higher proficiency of the left hemisphere in encoding dynamic acoustic events such as rapid formant transitions (30-40 ms) that distinguish consonant-vowel syllables such as /ba/ or /da/. In order to further elucidate the underlying neurophysiological mechanisms, discrimination of /bi/-like formant transitions of variable duration (18, 36, 54, or 72 ms) from a steady-state /i/-like vowel was investigated by means of whole-head magnetoencephalography (MEG) both during visual distraction and selective attention. Voiced speech-like as well as unvoiced non-speech stimuli, matched for spectral envelope, served as test materials. Based on an oddball design, magnetic mismatch fields (MMF) were determined during an early (170-210 ms) and a late (230-290 ms) time window. Selective attention toward the deviant events resulted in enhanced MMFs particularly within the left hemisphere, indicating attention-dependent left-lateralized processing of dynamic auditory events across both the speech and non-speech domains. Perceptual discrimination improved along with transient lengthening. Accordingly, early MMF was, as a rule, enlarged in case of longer as compared to shorter transients. The 36-ms transitions yielded attention- and voicing-dependent deviations from the linear regression of MMF strength on transition duration. Considering the predominance of 30- to 40-ms formant transients across the world's languages, these findings indicate an adaptation or predisposition of the human perceptual system to the spectral/temporal characteristics of prototypical speech sounds. Signal voicing had no significant main effect on MMF strength despite superior perceptual performance in case of voiced as compared to voiceless target stimuli.
NeuroReport, 2005
The onset of pitch within an ongoing noise signal evokes a particular brain activity, the pitch o... more The onset of pitch within an ongoing noise signal evokes a particular brain activity, the pitch onset response (POR). Using wholehead MEG, PORs to iterated rippled noise (IRN) and Huggins pitch (HP), representing prototypical pitch-in-noise signals, were measured in twenty subjects during a pitch identi¢cation task (333 Hz, 400 Hz, randomized). HP and IRN yielded similar responses, lateralized to the left hemisphere and peaking about 180 ms after pitch onset. The initial phase (140 ms) showed stronger activations to 400 than to 333 Hz whereas later stages (200^300 ms) showed target vs nontarget e¡ects.These results suggest, ¢rst, that di¡erent pitches converge into a common cortical representation and, second, that the POR encompasses various successive processing stages. NeuroReport 16:193^196
NeuroImage, Jan 15, 2005
The processing streams of the various sensory modalities are known to interact within the central... more The processing streams of the various sensory modalities are known to interact within the central nervous system. These interactions differ depending on the level of stimulus representation and attention. The current study focused on cross-sensory influences on stimulus change detection during unattended auditory processing. We employed an oddball paradigm to assess cortical processing using whole-head magnetoencephalography (MEG) in 20 volunteers. While subjects performed distraction tasks of varying difficulties, auditory duration deviants were applied randomly to the left or the right ear preceded (200-400 ms) by oculomotor, static visual, or flow field co-stimulation at either side. Mismatch fields were recorded over both hemispheres. Changes in gaze direction and static visual stimuli elicited the most reliable enhancement of deviance detection at the same side (most prominent at the right auditory cortex). Under both conditions, the lateralized unattended and unpredictive pre-...
Functional MRI localizing in the cerebellum
Neurosurgery clinics of North America, 2005
Mapping of cerebellar function by functional MRI now enables us not only to re-establish older an... more Mapping of cerebellar function by functional MRI now enables us not only to re-establish older anatomic findings of somatotopic representations but to gain new insights in the function of the cerebellum and its intimate relations of cerebral regions to serving sensorimotor function, sensory discrimination, and cognitive processing. Consequently, it will change our understanding of neurologic and psychologic failures in patients with inborn errors or neurodegenerative diseases or after neurosurgical procedures.
Speech Disorders following Severe Traumatic Brain Injury: Kinematic Analysis of Syllable Repetitions Using Electromagnetic Articulography
Folia Phoniatrica et Logopaedica, 2000
Using electromagnetic articulography, the lips, the tip of the tongue, and the tongue dorsum were... more Using electromagnetic articulography, the lips, the tip of the tongue, and the tongue dorsum were tracked during repetitions of the syllables [pa], [ta] and [ka] in 10 speakers with dysarthria following severe traumatic brain injury and in 10 age-matched control subjects. When asked to produce the syllable trains as fast as possible, the patient group showed a rather homogeneous pattern of movement abnormalities including prolonged syllable durations and reduced peak velocity/amplitude ratios. Most presumably, limited speed generation gives rise to the impaired ability to increase speech rate. During the habitual speaking condition, reduced velocity/amplitude ratios were restricted to the tongue tip and tongue dorsum. Obviously, the tongue and the lips are differentially affected in dysarthria following severe traumatic brain injury.
Neurophonetics
WIREs Cognitive Science, 2012
Neurophonetics aims at the elucidation of the brain mechanisms underlying speech communication in... more Neurophonetics aims at the elucidation of the brain mechanisms underlying speech communication in our species. Clinical observations in patients with speech impairments following cerebral disorders provided the initial vantage point of this research area and indicated distinct functional‐neuroanatomic systems to support human speaking and listening. Subsequent approaches—considering speech production a motor skill—investigated vocal tract movements associated with spoken language by means of kinematic and electromyographic techniques—allowing, among other things, for the evaluation of computational models suggesting elementary phonological gestures or a mental syllabary as basic units of speech motor control. As concerns speech perception, the working characteristics of auditory processing were first investigated based upon psychoacoustic techniques such as dichotic listening and categorical perception designs. More recently, functional hemodynamic neuroimaging and electrophysiologi...
The Cerebellum, 2013
Friedreich ataxia (FRDA) is the most frequent recessive ataxia in the Western world. Dysarthria i... more Friedreich ataxia (FRDA) is the most frequent recessive ataxia in the Western world. Dysarthria is a cardinal feature of FRDA, often leading to severe impairments in daily functioning, but its exact characteristics are only poorly understood so far. We performed a comprehensive evaluation of dysarthria severity and the profile of speech motor deficits in 20 patients with a genetic diagnosis of FRDA based on a carefully selected battery of speaking tasks and two widely used paraspeech tasks, i.e., oral diadochokinesis and sustained vowel productions. Perceptual ratings of the speech samples identified respiration, voice quality, voice instability, articulation, and tempo as the most affected speech dimensions. Whereas vocal instability predicted ataxia severity, tempo turned out as a significant correlate of disease duration. Furthermore, articulation predicted the overall intelligibility score as determined by a systematic speech pathology assessment tool. In contrast, neurologists' ratings of intelligibility-a component of the "Scale for the Assessment and Rating of Ataxia"-were found to be related to perceived speech tempo. Obviously, clinicians are more sensitive to slowness of speech than to any other feature of spoken language during dysarthria evaluation. Our results suggest that different components of speech production and trunk/limb motor functions are differentially susceptible to FRDA pathology. Furthermore, evidence emerged that paraspeech tasks do not allow for an adequate scaling of speech deficits in FRDA.
Contralaterality of cortical auditory processing at the level of the M50/M100 complex and the mismatch field: A whole-head magnetoencephalography study
Neuroreport, 2001
Humans show a stronger cortical representation of auditory input at the opposite hemisphere each.... more 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.
The right supratemporal plane hears the distance of objects: neuromagnetic correlates of virtual reality
NeuroReport, 2003
The neural mechanisms of auditory distance perception, a function of great biological importance,... more The neural mechanisms of auditory distance perception, a function of great biological importance, are poorly understood. Where not overruled by conflicting factors such as echoes or visual input, sound intensity is perceived as conveying distance information. We recorded neuromagnetic responses to amplitude variations over both supratemporal planes, with and without auditory spatial simulations. In the absence of other cues for distance, including those provided by auditory virtual reality, amplitude changes elicited enhanced preattentive responses over the right temporal lobe, indicating hemispheric lateralization of the 'where' pathway in the human. Lesion studies in monkeys and humans have shown that the rostral part of the right superior temporal cortex contributes to spatial awareness in the visual domain. Our data indicate that the distance to a sound source is processed within the adjacent right auditory cortex, thus extending the recent model of a right-hemisphere temporal multisensory matrix that subserves the integration of space-related data across visual and auditory modalities.
Time course and hemispheric lateralization effects of complex pitch processing: evoked magnetic fields in response to rippled noise stimuli
Neuropsychologia, 2004
To delineate the time course and processing stages of pitch encoding at the level of the supratem... more To delineate the time course and processing stages of pitch encoding at the level of the supratemporal plane, the present study recorded evoked magnetic fields in response to rippled noise (RN) stimuli. RN largely masks simple tonotopic representations and addresses pitch processing within the temporal domain (periodicity encoding). Four dichotic stimulus types (111 or 133 Hz RN at one ear, white noise to the other one) were applied in randomized order during either visual distraction or selective auditory attention. Strictly periodic signals, noise-like events, and mixtures of both signals served as control conditions. (1) Attention-dependent ear x hemisphere interactions were observed within the time domain of the M50 field, indicating early streaming of auditory information. (2) M100 responses to strictly periodic stimuli were found lateralized to the right hemisphere. Furthermore, the higher-pitched stimuli yielded enhanced activation as compared to the lower-pitch signals (pitch scaling), conceivably reflecting sensory memory operations. (3) Besides right-hemisphere pitch scaling, the relatively late M100 component in association with the RN condition (latency = 136 ms) showed significantly stronger field strengths over the left hemisphere. Control experiments revealed this lateralization effect to be related to noise rather than pitch processing. Furthermore, subtle noise variations interacted with signal periodicity. Obviously, thus, complex task demands such as RN encoding give rise to functional segregation of auditory processing across the two hemispheres (left hemisphere: noise, right hemisphere: periodicity representation). The observed noise/periodicity interactions, furthermore, might reflect pitch-synchronous spectral evaluation at the level of the left supratemporal plane, triggered by right-hemisphere representation of signal periodicity.
Neuropsychologia, 2002
It is still unsettled in how far temporal resolution of dynamic acoustic events (formant transiti... more It is still unsettled in how far temporal resolution of dynamic acoustic events (formant transitions) or phonetic/linguistic processes contribute to predominant left-hemisphere encoding of consonant-vowel syllables. To further elucidate the underlying mechanisms, evoked magnetic fields in response to consonant-vowel events (synthetic versus spoken) were recorded (oddball design: standards = binaural/ba/, deviants = dichotic/ba/-/da/; 20 right-handed subjects) under different attentional conditions (visual distraction versus stimulus identification). Spoken events yielded a left-lateralized peak phase of the mismatch field (MMF; 150-200 ms post-stimulus onset) in response to right-ear deviants during distraction. By contrast, pre-attentive processing of synthetic items gave rise to a left-enhanced MMF onset (100 ms), but failed to elicit later lateralization effects. In case of directed attention, synthetic deviants elicited a left-pronounced MMF peak resembling the pre-attentive response to natural syllables. These interactions of MMF asymmetry with signal structure and attentional load indicate two distinct successive left-lateralization effects: signal-related operations and representation of 'phonetic traces'. Furthermore, a right-lateralized early MMF component (100 ms) emerged in response to natural syllables during pre-attentive processing and to synthetic stimuli in case of directed attention. Conceivably, these effects indicate right hemisphere operations prior to phonetic evaluation such as periodicity representation. Two distinct time windows showed correlations between dichotic listening performance and ear effects on magnetic responses reflecting early gain factors (ca. 75 ms post-stimulus onset) and binaural fusion strategies (ca. 200 ms), respectively. Finally, gender interacted with MMF lateralization, indicating different processing strategies in case of artificial speech signals.
Neuropsychologia, 2002
Dichotic listening (DL) studies indicate higher proficiency of the right cerebral hemisphere in p... more Dichotic listening (DL) studies indicate higher proficiency of the right cerebral hemisphere in processing the pitch of auditory events. Especially, acoustic stimuli of a rich harmonic structure such as square waves (complex tones) elicit a left ear advantage (LEA) under dichotic stimulus application. In order to investigate the timing of early sensory encoding at the level of the supratemporal plane, whole-head magnetoencephalography (MEG; 151 channels) recordings were performed in 20 right-handed subjects using an oddball paradigm based on dichotically applied complex tones. In contrast to electroencephalography (EEG) and event related potentials (ERP), this technique separately measures neuronal activity of left and right auditory cortex. Neuromagnetic responses were obtained both during preattentive stimulus processing, as well as during a pitch detection task. Rare stimuli presented to the left ear elicited a stronger magnetic analogue of mismatch negativity (MMNm) over both hemispheres and gave rise to shorter latencies of the contralateral mismatch fields than right ear deviants. In conclusion, the present data provide first evidence for functional laterality effects even at the level of preattentive pitch processing within the auditory cortex.
Parametric analysis of rate-dependent hemodynamic response functions of cortical and subcortical brain structures during auditorily cued finger tapping: a fMRI study
NeuroImage, 2003
A multitude of functional imaging studies revealed a mass activation effect at the level of the s... more A multitude of functional imaging studies revealed a mass activation effect at the level of the sensorimotor cortex during repetitive finger-tapping or finger-to-thumb opposition tasks in terms of either a stepwise or a monotonic relationship between movement rate and hemodynamic response. With respect to subcortical structures of the centralmotor system, there is, by contrast, some preliminary evidence for nonlinear rate/response functions within basal ganglia and cerebellum. To further specify these hemodynamic mechanisms, functional magnetic resonance imaging (fMRI) was performed during a finger-tapping task in response to acoustic stimuli (six different frequencies: 2.0, 2.5, 3.0, 4.0, 5.0 and 6.0 Hz; applied via headphones). Passive listening to the same auditory stimuli served as a control condition. Statistical evaluation of the obtained data considered two approaches: categorical and parametric analysis. As expected, the magnitude of the elicited hemodynamic response within left sensorimotor cortex (plateau phase at frequencies above 4 Hz) and mesiofrontal cortex paralleled movement rate. The observed bipartite mesial response pattern, most presumably, reflects functional compartmentalization of supplementary motor area (SMA) in a rostral component (pre-SMA) and in a caudal (SMA proper) component. At the level of the cerebellum, two significant hemodynamic responses within the hemisphere ipsilateral to the hand engaged into finger tapping (anterior/posterior quadrangular lobule and posterior quadrangular lobule) could be observed. Both activation foci exhibited a stepwise rate/response function. In accordance with clinical data, these data indicate different cerebellar contributions to motor control at frequencies below or above about 3 Hz, respectively. Caudate nucleus, putamen, and external pallidum of the left hemisphere displayed, by contrast, a negative linear rate/response relationship. The physiological significance of these latter findings remains to be clarified.
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Papers by Hermann Ackermann