Consensus paper: Language and the cerebellum: an ongoing enigma.

In less than three decades, the concept "cerebellar neurocognition" has evolved from a mere afterthought to an entirely new and multifaceted area of neuroscientific research. A close interplay between three main strands of contemporary neuroscience induced a substantial modification of the traditional view of the cerebellum as a mere coordinator of autonomic and somatic motor functions. Indeed, the wealth of current evidence derived from detailed neuroanatomical investigations, functional neuroimaging studies with healthy subjects and patients and in-depth neuropsychological assessment of patients with cerebellar disorders shows that the cerebellum has a cardinal role to play in affective regulation, cognitive processing, and linguistic function. Although considerable progress has been made in models of cerebellar function, controversy remains regarding the exact role of the "linguistic cerebellum" in a broad variety of nonmotor language processes. This consensus paper brings together a range of different viewpoints and opinions regarding the contribution of the cerebellum to language function. Recent developments and insights in the nonmotor modulatory role of the cerebellum in language and some related disorders will be discussed. The role of the cerebellum in speech and language perception, in motor speech planning including apraxia of speech, in verbal working memory, in phonological and semantic verbal fluency, in syntax processing, in the dynamics of language production, in reading and in writing will be addressed. In addition, the functional topography of the linguistic cerebellum and the contribution of the deep nuclei to linguistic function will be briefly discussed. As such, a framework for debate and discussion will be offered in this consensus paper.

Unravelling the influence of mild traumatic brain injury (MTBI) on cognitive-linguistic processing: a comparative group analysis.

BACKGROUND: Cognitive-linguistic deficits often accompany traumatic brain injury (TBI) and can negatively impact communicative competency. The linguistic sequelae underpinning mild TBI (MTBI) remain largely unexplored in contemporary literature. OBJECTIVES: The present research methods aim to provide group evidence pertaining to the influence of MTBI on linguistic and higher-level language processing. Extrapolating on the findings of recent case reports, it is hypothesized that performance of the MTBI patients will be significantly reduced compared to normal controls performance on the employed high-level linguistic tasks. METHODS: Sixteen patients with MTBI and 16 age- and education-matched normal control participants were assessed using a comprehensive battery of cognitive-linguistic assessments. RESULTS: The results demonstrated statistically significant differences between MTBI and normal control group performance across a number of higher-level linguistic, general cognitive and general language tasks. MTBI group performance was significantly lower than the normal control group on tasks requiring complex lexical semantic operations and memory demands, including: Recall, organization, making inferences, naming and perception/discrimination. CONCLUSIONS: These outcomes confer that post-MTBI, cognitive, high-level language and isolated general language performance (e.g. naming) is significantly reduced in MTBI patients, compared to normal controls. Furthermore, the detailed cognitive-linguistic profile offered provides a necessary direction for the identification of areas of linguistic decline in MTBI and targets for therapeutic intervention of impaired cognitive-linguistic processes to ultimately improve communicative outcomes in MTBI.

Effect of speech rate manipulations on articulatory dynamics in severe traumatic brain injury: an EMA and EPG study.

BACKGROUND: Manipulation of speech rate forms an integral part of the treatment of dysarthria and the effects of changes in speech rate on articulatory dynamics in persons with traumatic brain injury (TBI) is poorly documented. OBJECTIVE: To determine the effects of manipulations of speech rate (habitual vs fast) on lingual kinematics and tongue-to-palate contacts in adult speakers with severe TBI and matched normal controls. MATERIALS AND METHODS: Six adults with severe TBI and five matched non-neurologically impaired controls underwent testing of their articulatory function using electromagnetic articulography (EMA) and electropalatography (EPG). RESULTS: The results demonstrated that the TBI and control groups selected different strategies for increasing speech rate, with the TBI group showing an increase in articulatory effort estimated from an increase in maximum velocity and maximum acceleration/deceleration of tongue movement when speaking at the fast rate. The control group demonstrated no effects of a fast speech rate on articulatory kinematics for sentence productions. CONCLUSIONS: When speaking at a fast rate, individuals with severe TBI appear to use greater articulatory effort, possibly to preserve the distinctiveness of phonetic segments in order to avoid articulatory undershoot. In contrast, control subjects show a greater economy of effort when speaking at a fast rate, possibly to preserve articulatory precision.

Lingual kinematics during rapid syllable repetition in Parkinson's disease.

BACKGROUND: Rapid syllable repetition tasks are commonly used in the assessment of motor speech disorders. However, little is known about the articulatory kinematics during rapid syllable repetition in individuals with Parkinson's disease (PD). AIMS: To investigate and compare lingual kinematics during rapid syllable repetition in dysarthric speakers with PD (DPD), non-dysarthric speakers with PD (NDPD) and a group of healthy controls. METHODS & PROCEDURES: Electromagnetic articulography was used to record tongue-tip and tongue-back movement in five DPD and five NDPD participants during rapid repetition of /ta/and /ka/syllables, and matched with six healthy controls. OUTCOMES & RESULTS: Results revealed significant between-group differences for most of the kinematic parameters measured but comparable rapid syllable repetition rates. Post-hoc analyses indicated that the DPD participants, when compared with the NDPD participants, had similar range but prolonged duration of lingual movement. The DPD and NDPD participants had primarily increased range and prolonged duration of lingual movement accompanied by increased speed parameters, when compared with healthy controls. CONCLUSIONS & IMPLICATIONS: The findings of the present study contradict theories that suggest that the clinical features of hypokinetic dysarthria, including articulatory imprecision, are the outcome of restrictions in the range of movement of the muscles of the articulators. The observed prolonged duration of lingual movement in PD may plausibly be due to the observed increased range of lingual movement rather than slowness of lingual movement.

Differentiating profiles of speech impairments in Friedreich's ataxia: a perceptual and instrumental approach.

BACKGROUND: The speech disorder associated with Friedreich's ataxia (FRDA) is classically described as ataxic dysarthria. However, variable neuropathology beyond the cerebellum, which may include the corticospinal and corticobulbar tracts, means that the dysarthria can be mixed rather than a pure ataxic dysarthria. AIMS: To characterize physiological features of the dysarthria associated with FRDA and identify differential patterns of deviation that may occur across the subsystems of the speech-production mechanism in a series of seven case studies. METHODS & PROCEDURES: The assessment battery included a perceptual analysis of a speech sample using an interval rating scale, and a range of instrumental measures to investigate the respiratory, laryngeal, velopharyngeal and articulatory systems. OUTCOMES & RESULTS: The results demonstrated the variability that exists in the dysarthria associated with FRDA, highlighting the existence of differential profiles of speech impairment. A particular distinction was observed between the presence of hypernasality and phonatory dysfunction, as evidenced by the instrumental results. CONCLUSIONS & IMPLICATIONS: The distinct profiles of dysarthria associated with FRDA indicate that approaches that address multiple subsystems are necessary for the accurate characterization and quantification of the motor speech disorder. Further research is required to investigate the decline in speech function as the disease progresses, as changes in speech function over time may be a good indicator of neurological decline in FRDA.

Indices of language outcome 11 years after intrathecal chemotherapy for acute lymphoblastic leukemia: a sibling case-control study.

Studies are emerging that suggest that major language indices do not differentiate children treated for acute lymphoblastic leukemia (ALL) with risk-adapted intrathecal chemotherapy (ITC) from control children matched on age, gender, and educational level. No study to date has controlled for cognitive environment, an important variable influencing language achievement and outcome. This case-control study applies the deconfounding principle by using a sibling as a control to investigate language outcomes in a male child 11 years after administration of ITC for ALL at the age of 2 years 3 months. A comprehensive behavioral language test battery failed to differentiate the siblings on current language performance when descriptively compared, but neurophysiological assessment revealed that the ITC-treated child required more time and elicited a smaller N400 component compared to his sibling during picture-word matching. The findings suggest that in the absence of pretreatment performance indices, comparison with sibling achievement may supplement what is known on posttreatment language skill development drawn from comparative studies using children matched on age, sex, and educational level drawn from the community. The study's findings offer pilot data of language outcomes following ITC beyond the early stage of survivorship. The benefits and limitations of using siblings in research where the cognitive environment is known to make an important contribution to skill development are discussed.

Developmental changes in the variability of tongue and lip movements during speech from childhood to adulthood: an EMA study.

This study investigated the developmental variability of lip and tongue movement in 48 children and adults. Motion of the tongue-tip, tongue-body and lower lip was recorded using electromagnetic articulography during productions of sentences containing /t/, /s/, /l/, /k/ and /p/. Four groups of speakers participated in the study: (1) aged 6-7 years; (2) 8-11 years; (3) 12-17 years; and (4) adults. The variation in distance, duration, speed, acceleration and deceleration of the articulators during single open-close speech movements was analysed, and the stability of multiple movement sequences was examined using the spatiotemporal index. The experimental findings revealed a gradual developmental progression from 6 years to adulthood. At adolescence, speakers continued to exhibit significantly more variable speech motor output compared to adult speakers. The observed developmental pattern suggests that attenuated, but important, changes in the speech motor system occurs from mid-childhood, through adolescence, to adulthood.

Intact language skills and semantic processing speed following the use of fractionated cranial irradiation therapy for the treatment of childhood medulloblastoma: a 4-year follow-up study.

Recent advances in the delivery of cranial radiation therapy aim to reduce the adverse neurocognitive outcomes associated with successful treatments. Damage to white matter tracts following cranial radiation may result in a reduction in information processing speed, which in turn may lead to declines in academic achievement and performance scores on neurocognitive testing. This study reports on language outcomes and neurophysiological measures reflecting the efficiency of the brain's capacity to process semantic information in a 14-year-old female following treatment, which included fractionated cranial radiation dosages, for medulloblastoma at age 10 years 3 months. The findings suggest processing skills on par with her peers and stability in general language skill over the 4 years post-treatment.

Kinematic analysis of lingual movements during consonant productions in dysarthric speakers with Friedreich's ataxia: A case-by-case analysis.

Articulatory kinematics were investigated using electromagnetic articulography (EMA) in four dysarthric speakers with Friedreich's ataxia (FRDA). Specifically, tongue-tip and tongue-back movements were recorded by the AG-200 EMA system during production of the consonants /t/ and /k/ as produced within a sentence utterance and during a rapid syllable repetition task. The results obtained for each of the participants with FRDA were individually compared to those obtained by a control group (n = 10). Results revealed significantly greater movement durations and increased articulatory distances, most predominantly during the approach phase of consonant production. A task difference was observed with lingual kinematics more disturbed during the syllable repetition task than during the sentence utterance. Despite expectations of slowed articulatory movements in FRDA dysarthria, the EMA data indicated that the observed prolongation of consonant phase durations was generally associated with greater articulatory distances, rather than slowed movement execution.

Language skills in a child with Leber hereditary optic neuropathy following intrathecal chemotherapy for acute lymphoblastic leukemia.

The language skills of a male child with Leber hereditary optic neuropathy (LHON) and coincidentally treated for acute lymphoblastic leukemia (ALL) with intrathecal chemotherapy at the age of 3 years 8 months were comprehensively evaluated twice over a 6-month period approximately 5½ years after diagnosis of ALL. Despite marked chemotherapy-related leukoencephalopathic changes documented on magnetic resonance imaging, the child presented with stable language skills, which were generally average to above-average based on the normative data from a comprehensive language test battery. In light of the coincidental presentation in the child of a diagnosis of LHON, which may lead to serious vision impairment and increased vulnerability to drug neurotoxicity, coupled with a history of central nervous system (CNS)-directed treatment for ALL resulting in progressive white matter pathology, the study highlights the importance of ongoing monitoring of the child's language development throughout his adolescent years.

Semantic activation in Parkinson's disease patients on and off levodopa.

Research suggests that dopamine may exert a neuromodulatory influence on automatic spreading activation within semantic networks. In order to investigate the influence of dopamine depletion on semantic activation in Parkinson's disease (PD), nine patients with PD performed a lexical decision task when on and off levodopa medication. Eleven healthy controls matched to the PD patients in terms of sex, age and education also participated in the study. Both directly related word pairs (e.g., tiger - stripe) and indirectly related word pairs (word pairs related via a mediating word, e.g., chalk - black) were used to measure semantic activation across stimulus onset asynchronies (SOAs) of 270msec, 520msec and 1020msec. Analysis of variance statistics revealed that the activation of directly related and indirectly related targets was slower for the PD group relative to the control group. Within group comparisons revealed further changes to semantic activation in PD patients off medication, with no activation of directly or indirectly related target words evident in PD patients off medication. These results further clarify the nature of dopamine's neuromodulatory influence on semantic activation, and suggest that the nature of altered semantic activation in PD may depend on the magnitude of dopamine depletion.

Kinematic analysis of articulatory coupling in acquired apraxia of speech post-stroke.

PRIMARY OBJECTIVE: Electromagnetic articulography was employed to investigate the strength of articulatory coupling and hence the degree of functional movement independence between individual articulators in apraxia of speech (AOS). METHODS AND PROCEDURES: Tongue-tip, tongue-back and jaw movement was recorded from five speakers with AOS and a concomitant aphasia (M = 53.6 years; SD = 12.60) during /ta, sa, la, ka/ syllable repetitions, spoken at typical and fast rates of speech. Covariance values were calculated for each articulatory pair to gauge the strength of articulatory coupling. The results obtained for each of the participants with AOS were individually compared to those obtained by a control group (n = 12; M = 52.08 years; SD = 12.52). Comparisons were made between the typical rate productions of the control group and the typical and fast rate productions of the participants with AOS. MAIN OUTCOMES AND RESULTS: In comparison to the control group, four speakers with AOS exhibited significantly stronger articulatory coupling for alveolar and/or velar speech targets, during typical and/or fast rate conditions, suggesting decreased functional movement independence. CONCLUSIONS: The reduction in functional movement independence might have reflected an attempt to simplify articulatory control or a decrease in the ability to differentially control distinct articulatory regions.

Examining the effects of multiple sclerosis on speech production: does phonetic structure matter?

UNLABELLED: The second formant (F2) is well-known to be important to intelligibility (e.g. [Delattre, P., Liberman, A., & Cooper, F. (1955). Acoustic loci and transitional cues for consonants. Journal of the Acoustical Society of America, 27, 769-774]) and is affected by a variety of dysarthrias [Weismer, G., & Martin, R. (1992). Acoustic and perceptual approaches to the study of intelligibility. In R. Kent (Ed.), Intelligibility in speech disorders (pp. 67-118). Amsterdam: John Benjamins Publishing Company]. This study tests two related hypotheses: (1) dysarthria associated with Multiple Sclerosis (MS) has a greater effect on the ability to produce extreme F2 movement than on typical F2 movement and (2) phonetic stimuli associated with large and/or rapid F2 movement in healthy speakers precipitate larger differences between healthy and dysarthric speech than do stimuli associated with small and/or slow F2 movement. Twelve participants with MS and 16 healthy controls read aloud the Grandfather Passage. F2 slopes were calculated from the F2 tracings (i.e. change in Hz over a 20ms lag). For each sentence, the following measures of F2 movement were calculated: F2 range (maximum F2-minimum F2), median slope, and 95%ile slope. The mean and the maximum observation for each participant were respectively used as measures of typical and extreme productions. A repeated-measures MANOVA detected significantly larger group differences in the slopes of maximum productions than for mean production. Also, group differences in F2 slope were greater in phonetic stimuli associated with the largest F2 slopes in healthy speech than in phonetic stimuli associated with more shallow slopes. No group differences in F2 range were detected. Results indicate dysarthria affects the production of extremely rapid changes in F2 and that some phonetic structures are more useful than others for detecting these impairments. It is concluded that comparison of speakers' best-productions (e.g. maximum F2 slope) yield more useful estimates of the effects of mild to moderate dysarthria on F2 slopes than do typical productions. LEARNING OUTCOMES: The reader will be able to: (1) describe two approaches to measuring typical and extreme acoustic variability that can be applied to connected speech, (2) discuss evidence that MS affects extremely rapid changes in F2.

Influence of a standard electropalatography artificial palate upon articulation. A preliminary study.

OBJECTIVE: This study investigated the influence of a standard electropalatography (EPG) palate upon speech articulation in 3 normal speakers under standard EPG testing conditions. PATIENTS AND METHODS: Three adult females aged 26, 31 and 34 years read the experimental phrase 'say CV again' 5 times under 3 experimental conditions: normal speech (without a palate in situ), 45 min after EPG palate insertion and 3 h after EPG palate insertion. Consonants and vowels commonly used in EPG research were studied and included /t/, /s/ and /integral/ in the /i/, /a/ and /u/ vowel environments. Perceptual and acoustic analysis of the data was completed. RESULTS: The results revealed varied patterns of adaptation across the 3 participants. Perceptual analysis suggested that 2 of the participants adapted to the presence of the palate; however, 1 did not. The presence of the palate resulted in significant changes to consonant duration for all 3 participants. Spectrally, production of /t/ was unaffected by the presence of the palate, while articulation of fricatives varied across the participants. CONCLUSION: Paired with a previous study examining the effects of an EPG palate upon speech articulation [McLeod S, Searl J: Am J Speech Lang Pathol 2006;15:192-206], the present data suggest that researchers and clinicians alike should be aware of the potential perturbing effects of the palate.

Communicative competence and metalinguistic ability: performance by children and adults with autism spectrum disorder.

The Test of Language Competence-Expanded Edition (TLC-E) was administered to children and adults with a diagnosis of autism spectrum disorder (ASD). Relative to controls, those with ASD were less competent on a range of TLC-E tasks. No differences were found for either child or adult ASD groups on any of the TLC-E measures when re-classified as Asperger syndrome (AS) and high functioning autism (HFA) using DSM-IV language criterion. Hierarchical cluster analyses of individuals with ASD identified subgroups within the spectrum. The use of developmental language history as an identifying marker in autism is questioned. The findings suggest that comprehensive language assessments on individuals with ASD can provide clinically relevant information regarding the heterogeneity of language skills within the autistic spectrum.

Physiologic development of tongue-jaw coordination from childhood to adulthood.

PURPOSE: This investigation aimed to examine the development of tongue-jaw coordination during speech from childhood to adolescence. METHOD: Electromagnetic articulography was used to track tongue and jaw motion in 48 children and adults (aged 6-38 years) during productions of /t/ and /k/ embedded in sentences. RESULTS: The coordinative organization of the tongue and jaw exhibited changes until the age of 8-11 years and continued to undergo refinement into late adolescence. The tongue-tip and tongue-body were observed to develop unique kinematic relations with the jaw. While tongue-tip movement became increasingly synchronized with jaw movement, tongue-body and jaw retained movement independence but developed a more consistent kinematic relation. CONCLUSION: The present results support the notion that speech motor development is nonuniform, with a refinement period from mid-childhood to late adolescence.

Electropalatographic assessment of tongue-to-palate contact patterns and variability in children, adolescents, and adults.

PURPOSE: To investigate the developmental time course of tongue-to-palate contact patterns during speech from childhood to adulthood using electropalatography (EPG) and a comprehensive profile of data analysis. METHOD: Tongue-to-palate contacts were recorded during productions of /t/, /l/, /s/, and /k/ in 48 children, adolescents and adults (aged 6-38 years) using the Reading Electropalatograph system. RESULTS: A protracted course of development for lingual control was indicated, with significant changes occurring until age 11 years; the adolescent period was in turn characterized by continual refinement of articulatory control. With maturity, a reduction in the amount of palatal contact and an anterior shift in the place of articulation was evident during anterior consonant productions, whereas the tongue-back-to-palate contact pattern became more consistent for the velar stop /k/. CONCLUSION: These results support that maturation of the speech motor system is nonuniform.

Language disorders subsequent to left cerebellar lesions: a case for bilateral cerebellar involvement in language?

BACKGROUND: Crossed cerebello-cerebral diaschisis, reflecting a functional depression of supratentorial language areas due to reduced input via cerebello-cortical pathways, may represent the neuropathological mechanism responsible for language deficits associated with cerebellar pathology. Although it has been proposed that language is lateralized to the right cerebellar hemisphere, recent clinical and neuroimaging studies suggest that the cerebellum may bilaterally influence the regulation of language, with the left cerebellar hemisphere also contributing to the mediation of language via ipsilateral cerebello-cortical pathways. AIMS: The aim of the study was to determine the effect of left primary cerebellar lesions on general as well as higher-level language function. METHODS AND PROCEDURES: Linguistic profiles of a group of ten individuals with left primary cerebellar lesions were compared with those of a group of non-neurologically impaired controls matched for age, gender and level of education. OUTCOMES AND RESULTS: The findings confirmed that higher-level language deficits may result from left primary cerebellar lesions possibly as a consequence of ipsilateral cerebral diaschisis. CONCLUSIONS: The results challenge the notion of a right lateralized cerebellum and support a role for the left as well as the right cerebellar hemisphere in the regulation of language function.

The impact of a cerebellar tumour on language function in childhood.

BACKGROUND/AIMS: Childhood-acquired cerebellar studies to date have appeared to present a concordant pattern of specific neuropsychological profiles depending on lesion site. The aim was to determine the impact of a cerebellar tumour specifically on language function in children by reporting both the general and high-level language abilities of 4 cases with differing sites of hemispheric and vermal involvement. METHODS: The language abilities of 4 children (aged from 7 years 9 months to 13 years), treated with surgery and/or radiotherapy for cerebellar tumour 6 months to 3 years previously, were examined. A standardized battery of general and high-level language assessments was administered. RESULTS: Analysis revealed intact abilities across all 4 cases on measures of general language, including receptive language, expressive language, receptive vocabulary and naming. While 2 of the 4 cases also demonstrated intact high-level language skills across all measures, the remaining 2 demonstrated specific deficits in linguistic problem solving at 6 months after treatment. Follow-up assessment of 1 case also demonstrated further decline in this area 12 months later. CONCLUSION: Findings of high-level language deficits in problem solving in 2 of the 4 cases examined supported previous reports of specific impairments in high-level language and in thinking flexibility and problem solving following cerebellar hemispheric damage in childhood.

The influence of dopamine on semantic activation in Parkinson's disease: evidence from a multipriming task.

Research has suggested that semantic processing deficits in Parkinson's disease (PD) are related to striatal dopamine deficiency. As an investigation of the influence of dopamine on semantic activation in PD, 7 participants with PD performed a lexical-decision task when on and off levodopa medication. Seven healthy controls matched to the participants with PD in terms of sex, age, and education also participated in the study. By use of a multipriming paradigm, whereby 2 prime words were presented prior to the target word, semantic priming effects were measured across stimulus onset asynchronies (SOAs) of 250 ms and 1,200 ms. The results revealed a similar pattern of priming across SOAs for the control group and the PD participants on medication. In contrast, within-group comparisons revealed that automatic semantic activation was compromised in PD participants when off medication. The implications of these results for the neuromodulatory influence of dopamine on semantic processing in PD are discussed.