Katja Batens

Increased motor preparation activity during fluent single word production in DS: A correlate for stuttering frequency and severity.

Abnormal speech motor preparation is suggested to be a neural characteristic of stuttering. One of the neurophysiological substrates of motor preparation is the contingent negative variation (CNV). The CNV is an event-related, slow negative potential that occurs between two defined stimuli. Unfortunately, CNV tasks are rarely studied in developmental stuttering (DS). Therefore, the present study aimed to evaluate motor preparation in DS by use of a CNV task. Twenty five adults who stutter (AWS) and 35 fluent speakers (FS) were included. They performed a picture naming task while an electro-encephalogram was recorded. The slope of the CNV was evaluated at frontal, central and parietal electrode sites. In addition, a correlation analysis was performed with stuttering severity and frequency measures. There was a marked increase in CNV slope in AWS as compared to FS. This increase was observed over the entire scalp with respect to stimulus onset, and only over the right hemisphere with respect to lip movement onset. Moreover, strong positive correlations were found between CNV slope and stuttering frequency and severity. As the CNV is known to reflect the activity in the basal ganglia-thalamo-cortical-network, the present findings confirm an increased activation of this loop during speech motor preparation in stuttering. The more a person stutters, the more neurons of this cortical-subcortical network seem to be activated. Because this increased CNV slope was observed during fluent single word production, it is discussed whether or not this observation refers to a successful compensation strategy.

When will a stuttering moment occur? The determining role of speech motor preparation.

The present study aimed to evaluate whether increased activity related to speech motor preparation preceding fluently produced words reflects a successful compensation strategy in stuttering. For this purpose, a contingent negative variation (CNV) was evoked during a picture naming task and measured by use of electro-encephalography. A CNV is a slow, negative event-related potential known to reflect motor preparation generated by the basal ganglia-thalamo-cortical (BGTC) - loop. In a previous analysis, the CNV of 25 adults with developmental stuttering (AWS) was significantly increased, especially over the right hemisphere, compared to the CNV of 35 fluent speakers (FS) when both groups were speaking fluently (Vanhoutte et al., (2015) doi: 10.1016/j.neuropsychologia.2015.05.013). To elucidate whether this increase is a compensation strategy enabling fluent speech in AWS, the present analysis evaluated the CNV of 7 AWS who stuttered during this picture naming task. The CNV preceding AWS stuttered words was statistically compared to the CNV preceding AWS fluent words and FS fluent words. Though no difference emerged between the CNV of the AWS stuttered words and the FS fluent words, a significant reduction was observed when comparing the CNV preceding AWS stuttered words to the CNV preceding AWS fluent words. The latter seems to confirm the compensation hypothesis: the increased CNV prior to AWS fluent words is a successful compensation strategy, especially when it occurs over the right hemisphere. The words are produced fluently because of an enlarged activity during speech motor preparation. The left CNV preceding AWS stuttered words correlated negatively with stuttering frequency and severity suggestive for a link between the left BGTC - network and the stuttering pathology. Overall, speech motor preparatory activity generated by the BGTC - loop seems to have a determining role in stuttering. An important divergence between left and right hemisphere is hypothesized.

CNV amplitude as a neural correlate for stuttering frequency: A case report of acquired stuttering.

A neural hallmark of developmental stuttering is abnormal articulatory programming. One of the neurophysiological substrates of articulatory preparation is the contingent negative variation (CNV). Unfortunately, CNV tasks are rarely performed in persons who stutter and mainly focus on the effect of task variation rather than on interindividual variation in stutter related variables. However, variations in motor programming seem to be related to variation in stuttering frequency. The current study presents a case report of acquired stuttering following stroke and stroke related surgery in the left superior temporal gyrus. A speech related CNV task was administered at four points in time with differences in stuttering severity and frequency. Unexpectedly, CNV amplitudes at electrode sites approximating bilateral motor and left inferior frontal gyrus appeared to be inversely proportional to stuttering frequency. The higher the stuttering frequency, the lower the activity for articulatory preparation. Thus, the amount of disturbance in motor programming seems to determine stuttering frequency. At right frontal electrodes, a relative increase in CNV amplitude was seen at the test session with most severe stuttering. Right frontal overactivation is cautiously suggested to be a compensation strategy. In conclusion, late CNV amplitude elicited by a relatively simple speech task seems to be able to provide an objective, neural correlate of stuttering frequency. The present case report supports the hypothesis that motor preparation has an important role in stuttering.

Subthalamic nucleus stimulation and spontaneous language production in Parkinson’s disease: A double laterality problem

BACKGROUNDnAsymmetric degeneration of dopaminergic neurons, are characteristic for Parkinsons disease (PD). Despite the lateralized representation of language, the correlation of asymmetric degeneration of nigrostriatal networks in PD with language performance has scarcely been examined.nnnOBJECTIVE/HYPOTHESISnThe laterality of dopamine depletion influences language deficits in PD and thus modulates the effects of subthalamic nucleus (STN) stimulation on language production.nnnMETHODSnThe spontaneous language production of patients with predominant dopamine depletion of the left (PD-left) and right (PD-right) hemisphere was compared in four stimulation conditions.nnnRESULTSnPD-right made comparatively more verb inflection errors than PD-left. Bilateral STN stimulation improves spontaneous language production only for PD-left.nnnCONCLUSIONSnThe laterality of dopamine depletion influences spontaneous language production and the effect of STN stimulation on linguistic functions. However, it is probably only one of the many variables influencing the effect of STN stimulation on language production.

Speaking in numbers as a transitional phase between mutism and Wernicke's aphasia: A report of three cases

Background: Mutism in the context of hemispheric stroke with aphasia is rare and usually evolves to non-fluent aphasia. Aims: We describe three multilingual and mathematically educated patients with an initial presentation of mutism, followed by a short-lasting episode of speaking in numbers as a transitional stage before developing Wernickes aphasia. We discuss potential pathophysiological mechanisms underlying this phenomenon. Methods & Procedures: Clinical neurolinguistic testing, including Aachen Aphasia Test and video-analysis of spontaneous speech by transcription. Outcomes & Results: In the transitional stage between mutism and Wernickes aphasia, numbers were randomly uttered in one or more languages, although not necessarily in the first acquired or most-used language. Number speech occurred not only in propositional speech, but also during reading and naming. Conclusions: These patients exhibit two peculiar phenomena. First, the evolution of mutism to Wernickes aphasia and second, the transitional phase of number speech. It is hypothesised that mutism may be more frequent in the hyperacute stages of stroke-related aphasia as a consequence of transient generalised failure of the language network. Current theories on the organisation of number magnitude and lexical retrieval of number and non-number words are discussed with reference to numerical speech. The lack of previous reports of this syndrome is probably due to the combination of the transient nature of the phenomenon and the suspected prerequisites of a specific neuro-anatomical lesion and educational background.

The influence of subthalamic nucleus stimulation on pragmatic language production in Parkinson's disease.

AbstractWhile the influence of deep brain stimulation (DBS) of the subthalamic nucleus (STN) on the comprehension of pragmatic language in Parkinson’s disease (PD) has been the focus of studies, its impact on production, however, has yet to be elucidated. (1) Investigating the infnluence of DBS STN on pragmatic language production in spontaneous speech by comparing different stimulation conditions and (2) evaluating the effect of asymmetric dopaminergic denervation. This paper included 18 patients with advanced idiopathic PD with STN DBS. [Ten PD patients with predominantly left hemispheric dopamine denervation (PD-left) and eight PD patients with predominantly right-hemispheric dopamine denervation (PD-right).] The pragmatic components ‘communicative functions’ and ‘conversational skills’ were evaluated by analysing the spontaneous language production in four stimulation conditions. STN stimulation did not appear to influence the pragmatic production skills. Only when asymmetric dopamine depletion was taken into account the parameter ‘giving an explanation’ interaction was detectable. STN DBS appears to have some influence on the production of pragmatic language depending on asymmetric dopaminergic denervation. Suggestions are made for further research of pragmatic production in Parkinson’s disease.

Aphasia therapy early after stroke : behavioural and neurophysiological changes in the acute and post-acute phases

Background: There is reasonable evidence to suggest that speech and language therapy can be effective in the chronic stages of stroke recovery. However, the active ingredients remain unknown and several variables can influence therapy outcome, such as content, type, and amount of therapy. Neurophysiological measures, event-related brain potentials such as the N400 and P300, have shown to be sensitive markers of therapeutic effects. As a supplement to the usual behavioural evaluation methods, neurophysiological measures might help to further disentangle the effect of content, type, and/or amount of therapy. Aims: The present single case study aims to investigate the effect of language therapy by combining behavioural and neurophysiological outcome measures in a patient with aphasia during the acute and post-acute stage after stroke. By further subdividing the therapy period into different therapy blocks, possible influences of content, type, and/or amount of therapy are investigated. Methods & Procedures: RL is a 47-year-old man with a moderate non-fluent aphasia, who received three periods of therapy in the first four months after his stroke. The initial evaluation moment occurred 10 days post-stroke. First, he received an intensive language treatment of 30 hr in 3 weeks, which was followed by a conventional treatment of 30 hr in 7 weeks. Then, RL received a second, intensive language therapy of 30 hr in 3 weeks. This was followed by a period of 6 months without any form of language treatment. Behavioural and neurophysiological measures were collected after every therapy and therapy-free period. The effect of therapy was examined by comparing the whole therapy period with the therapy-free period, without differentiating between the intensive and conventional treatment. In a second analysis, a comparison was made between the intensive therapy periods and the conventional therapy programme. Outcomes & Results: RL showed a general improvement on both behavioural and neurophysiological measures after the whole therapy period, which was preserved throughout the therapy-free period. Intensive treatment yielded better language outcomes as indicated by a behavioural and neurophysiological improvement in contrast with the behavioural deterioration of auditory discrimination of pseudowords and decline of the N400 neurophysiological marker, after the conventional therapy. Conclusions: The present study demonstrates the outcome of early language treatment after stroke in which intensity can play an important role. In addition, the use of neurophysiological outcome measures provides added value to the behavioural evaluations in the context of therapeutic follow-up.