Role of cerebellum in fine speech control in childhood: persistent dysarthria after surgical treatment for posterior fossa tumour

Dysarthria following surgical resection of childhood posterior fossa tumour (PFT) is most commonly documented in a select group of participants with mutism in the acute recovery phase, thus limiting knowledge of post-operative prognosis for this population of children as a whole. Here we report on the speech characteristics of 13 cases seen long-term after surgical treatment for childhood PFT, unselected for the presence of post-operative mutism (mean time post-surgery = 6y10 m, range 1;4-12;6 years, two had post-operative mutism), and examine factors affecting outcome. Twenty-six age- and sex- matched healthy controls were recruited for comparison. Participants in both groups had speech assessments using detailed perceptual and acoustic methods. Over two-thirds of the group (69%) with removal of PFT had a profile of typically mild dysarthria. Prominent speech deficits included consonant imprecision, reduced rate, monopitch and monoloudness. We conclude that speech deficits may persist even up to 10 years post-surgery in participants who have not shown mutism in the acute phase. Of cases with unilateral lesions, poorer outcomes were associated with right cerebellar tumours compared to left, consistent with the notion based on adult data that speech is controlled by reciprocal right cerebellar/left frontal interactions. These results confirm the important role of the cerebellum in the control of fine speech movements in children.     

Productive syntax abilities in Huntington's and Parkinson's diseases

This study examined syntactic changes in the spoken discourse of patients with Huntington's (HD) or Parkinson's disease (PD) and explored possible relationships between their syntactic changes and concomitant cognitive and motoric symptoms. Patient and control groups participated in a conversational discourse activity and completed a battery of standardized speech and cognitive tests. The HD group used shorter and fewer grammatically complete utterances than their healthy, age-matched peers, whereas there were no significant syntactic differences between PD patients and their healthy, age-matched peers or between PD and HD patients. Productive syntax abilities in HD and PD were meaningfully related to both neuropsychological and motor speech changes. These findings indicate that patients with subcortical disease, at least those with HD, may present with language production deficits and that these deficits are most likely the product of not only motor speech limitations (i.e., dysarthria) but also underlying cognitive impairments.     

Incidence of dysarthria in children with cerebellar tumors: a prospective study

The present study investigated dysarthric symptoms in children with cerebellar tumors. Ten children with cerebellar tumors and 10 orthopedic control children were tested prior and one week after surgery. Clinical dysarthric symptoms were quantified in spontaneous speech. Syllable durations were analyzed in syllable repetition and sentence production tasks. Localization of the cerebellar lesions were defined after manual transfer from individual 2D-MR images onto 3D images of a spatially normalized healthy brain. Cerebellar children showed few and mild clinical signs of dysarthria. No difference was present in the sentence production task compared to controls. In five cerebellar children, syllables were prolonged in the syllable repetition task after surgery. Syllable duration normalized in an additional four-week session in all but one case. The MR-analysis showed that superior paravermal cerebellar areas likely involved in dysarthria in adults (paravermal lobules HVI, Crus I) were not significantly affected. In children, speech impairments appear to be rare after cerebellar surgery because tumors most commonly affect posterior-inferior and medial parts of the cerebellum while critical cerebellar regions are likely spared. The results suggest a similar localization of speech functions in the cerebellum in children and adults.     

Speech motor programming in hypokinetic and ataxic dysarthria

It is widely accepted that the cerebellar and basal ganglia control circuits contribute to the programming of movement. Converging evidence from neuroimaging, limb control, and neuropsychological studies suggests that (1) people with cerebellar disease have reduced ability to program movement sequences in advance of movement onset and (2) people with Parkinson's disease are unable to maintain a programmed response or to rapidly switch between responses. Despite a substantial supporting literature, no studies have addressed these potential areas of speech programming disruption for speakers with ataxic and hypokinetic dysarthria. Control participants and adults with dysarthria completed speech reaction time protocols designed to capture these aspects of utterance preparation. Results provided initial support for processing deficits in speakers with ataxic and hypokinetic dysarthria that are separable from motor execution impairments.     

Discrimination of speech sounds by children with dyslexia: comparisons with chronological age and reading level controls

Previous studies have shown that children suffering from developmental dyslexia have a deficit in categorical perception of speech sounds. The aim of the current study was to better understand the nature of this categorical perception deficit. In this study, categorical perception skills of children with dyslexia were compared with those of chronological age and reading level controls. Children identified and discriminated /do-to/ syllables along a voice onset time (VOT) continuum. Results showed that children with dyslexia discriminated among phonemically contrastive pairs less accurately than did chronological age and reading level controls and also showed higher sensitivity in the discrimination of allophonic contrasts. These results suggest that children with dyslexia perceive speech with allophonic units rather than phonemic units. The origin of allophonic perception in the course of perceptual development and its implication for reading acquisition are discussed.     

Evaluating current deficit theories of poor reading: role of phonological processing, naming speed, balance automaticity, rapid verbal perception and working memory

To clarify the nature of cognitive deficits experienced by poor readers, 9-10-yr.-old poor readers were matched against 9 chronological age and 9 younger reading age-matched controls screened and selected from regular classrooms. Poor readers performed significantly more poorly than chronological age-matched peers on digit naming speed, spoonerisms, and nonsense word reading. Poor readers were also significantly poorer than reading age-matched controls on nonword reading but were significantly better than reading age-matched controls on postural stability. Analyses of effect sizes were consistent with these findings, showing strong effects for digit naming speed, spoonerisms, and nonword reading. However, effect size analysis also suggested that poor readers experienced moderate difficulties with balance automatisation but did not show verbal speech perception deficits relative to either control     

Verbal reaction time patterns in aphasic adults: consideration for apraxia of speech

Verbal reaction time patterns were compared in aphasic adults presenting anterior and posterior left hemisphere lesions. Reaction Times were measured from simultaneous recording of the subjects' verbal responses and electromyographic activity from three oral-facial sites. Total Reaction Time was fractionated into Premotor Time and Motor Time components to assess latencies associated with motor speech planning and execution. The results suggested that only anterior lesions result in deficits in motor speech planning and/or execution while posterior lesion patients perform no differently than normal. The evidence supports traditional concepts regarding apraxia of speech as being associated with frontal lobe lesions.     

The cognitive profile and multiple-deficit hypothesis in Chinese developmental dyslexia

The present study was conducted to examine the cognitive profile and multiple-deficit hypothesis in Chinese developmental dyslexia. Thirty Chinese dyslexic children in Hong Kong were compared with 30 average readers of the same chronological age (CA controls) and 30 average readers of the same reading level (RL controls) in a number of rapid naming, visual, phonological, and orthographic tasks. Chinese dyslexic children performed significantly worse than the CA controls but similarly to the RL controls on most of the cognitive tasks. The rapid naming deficit was found to be the most dominant type of cognitive deficit in Chinese dyslexic children. Over half of the dyslexic children exhibited deficits in 3 or more cognitive areas, and there was a significant association between the number of cognitive deficits and the degree of reading and spelling impairment. The present findings support the multiple-deficit hypothesis in Chinese developmental dyslexia.     

Speech-Language Outcomes of Hemispherectomy in Children and Young Adults

Children and young adults who had undergone right or left hemispherectomy for intractable seizures after a period of normal language acquisition were compared with respect to scores on speech and language tests. The majority of the subjects had full scale IQs in the borderline to mentally retarded range. Language scores were computed in relation to estimated mental age, not chronological age. On this basis, the left hemispherectomized children were more likely to show syntactic comprehension and rapid-rate auditory processing deficits than the right hemispherectomized. The two groups were similar to one another and to normal children in speech production. The findings are discussed in relation to developmental language disorders.     

Visual versus phonological abilities in Spanish dyslexic boys and girls

Phonological and visual theories propose different primary deficits as part of the explanation for dyslexia. Both theories were put to test in a sample of Spanish dyslexic readers. Twenty-one dyslexic and 22 typically-developing children matched on chronological age were administered phonological discrimination and awareness tasks and coherent motion perception tasks. No differences were found between groups on the coherent motion tasks, whereas dyslexic readers were impaired relative to controls on phonological discrimination tasks. Gender differences followed the opposite pattern, with no differences on phonological tasks, and dyslexic girls performing significantly worse than dyslexic boys in coherent motion perception. These results point to the importance of phonological deficits related to speech perception in Spanish, and to possible gender differences in the neurobiological bases for dyslexia.     

Speech perception and short-term memory deficits in persistent developmental speech disorder

Children with developmental speech disorders may have additional deficits in speech perception and/or short-term memory. To determine whether these are only transient developmental delays that can accompany the disorder in childhood or persist as part of the speech disorder, adults with a persistent familial speech disorder were tested on speech perception and short-term memory. Nine adults with a persistent familial developmental speech disorder without language impairment were compared with 20 controls on tasks requiring the discrimination of fine acoustic cues for word identification and on measures of verbal and nonverbal short-term memory. Significant group differences were found in the slopes of the discrimination curves for first formant transitions for word identification with stop gaps of 40 and 20 ms with effect sizes of 1.60 and 1.56. Significant group differences also occurred on tests of nonverbal rhythm and tonal memory, and verbal short-term memory with effect sizes of 2.38, 1.56, and 1.73. No group differences occurred in the use of stop gap durations for word identification. Because frequency-based speech perception and short-term verbal and nonverbal memory deficits both persisted into adulthood in the speech-impaired adults, these deficits may be involved in the persistence of speech disorders without language impairment.     

Error Analysis of Limb and Orofacial Praxis in Children with Developmental Motor Deficits

Two models have been suggested to depict the relationship between disorders of limb and orofacial praxis. The first views apraxia as a unitary disorder in which the underlying mechanisms for each type are similar, while the second model suggests that there are two separate praxis systems: one for planning and controlling limb gestures and a second one for planning and controlling orofacial movements. The purpose of this study was to investigate whether a common mechanism may underlie deficits in limb and orofacial praxis in children. This was done by analyzing the types of praxis errors demonstrated by children with developmental motor deficits and normal controls when performing limb and orofacial gestures. Results indicated that there was consistency across modalities (i.e., limb, orofacial) in the types of praxis errors made by children with motor deficits, providing support for the idea that a common mechanism may underlie disruptions to limb and orofacial praxis in children. This study also examined developmental trends in gestural representation and in types of praxis errors. The findings revealed a striking developmental maturation in gestural ability between the ages of 6 and 11 years for all children. However, over this age range, children with developmental motor deficits were impaired relative to normal controls.     

The Gesell developmental schedule in hispanic low-birth weight infants during the first year of life

The Gesell Schedule was administered to 143 low birthweight, high-risk, Hispanic infants of low-socioeconomic status to determine if this test was appropriate for this population. All but 5 were preterms, 73 females, 70 males. The infants were evaluated at 20 and 40 weeks corrected chronological age (CCA). The Gesell appears to be a useful developmental test for this population. Values for the overall developmental quotient (DQ) did not deviate from the Gesell norms, despite the infants' relatively poor growth pattern. Slight deviations from the norm in gross motor, fine motor, and language subscales were observed at 40 weeks CCA. Repeated measure analyses of variance revealed a significant decline in overall developmental, language, and fine motor quotients from 20 to 40 weeks. Birth-weight (BW) and small-for-gestational-age (SGA) categories influenced the outcome.     

Facial speech gestures: the relation between visual speech processing,phonological awareness,and developmental dyslexia in 10‐year‐olds

Successful communication in everyday life crucially involves the processing of auditory and visual components of speech. Viewing our interlocutor and processing visual components of speech facilitates speech processing by triggering auditory processing. Auditory phoneme processing, analyzed by event‐related brain potentials (ERP), has been shown to be associated with impairments in reading and spelling (i.e. developmental dyslexia), but visual aspects of phoneme processing have not been investigated in individuals with such deficits. The present study analyzed the passive visual Mismatch Response (vMMR) in school children with and without developmental dyslexia in response to video‐recorded mouth movements pronouncing syllables silently. Our results reveal that both groups of children showed processing of visual speech stimuli, but with different scalp distribution. Children without developmental dyslexia showed a vMMR with typical posterior distribution. In contrast, children with developmental dyslexia showed a vMMR with anterior distribution, which was even more pronounced in children with severe phonological deficits and very low spelling abilities. As anterior scalp distributions are typically reported for auditory speech processing, the anterior vMMR of children with developmental dyslexia might suggest an attempt to anticipate potentially upcoming auditory speech information in order to support phonological processing, which has been shown to be deficient in children with developmental dyslexia.     

Auditory‐motor adaptation is reduced in adults who stutter but not in children who stutter

Previous studies have shown that adults who stutter produce smaller corrective motor responses to compensate for unexpected auditory perturbations in comparison to adults who do not stutter, suggesting that stuttering may be associated with deficits in integration of auditory feedback for online speech monitoring. In this study, we examined whether stuttering is also associated with deficiencies in integrating and using discrepancies between expected and received auditory feedback to adaptively update motor programs for accurate speech production. Using a sensorimotor adaptation paradigm, we measured adaptive speech responses to auditory formant frequency perturbations in adults and children who stutter and their matched nonstuttering controls. We found that the magnitude of the speech adaptive response for children who stutter did not differ from that of fluent children. However, the adaptation magnitude of adults who stutter in response to auditory perturbation was significantly smaller than the adaptation magnitude of adults who do not stutter. Together these results indicate that stuttering is associated with deficits in integrating discrepancies between predicted and received auditory feedback to calibrate the speech production system in adults but not children. This auditory‐motor integration deficit thus appears to be a compensatory effect that develops over years of stuttering.     

Atypical speech lateralization in adults with developmental coordination disorder demonstrated using functional transcranial Doppler ultrasound

Research using clinical populations to explore the relationship between hemispheric speech lateralization and handedness has focused on individuals with speech and language disorders, such as dyslexia or specific language impairment (SLI). Such work reveals atypical patterns of cerebral lateralization and handedness in these groups compared to controls. There are few studies that examine this relationship in people with motor coordination impairments but without speech or reading deficits, which is a surprising omission given the prevalence of theories suggesting a common neural network underlying both functions. We use an emerging imaging technique in cognitive neuroscience; functional transcranial Doppler (fTCD) ultrasound, to assess whether individuals with developmental coordination disorder (DCD) display reduced left‐hemisphere lateralization for speech production compared to control participants. Twelve adult control participants and 12 adults with DCD, but no other developmental/cognitive impairments, performed a word‐generation task whilst undergoing fTCD imaging to establish a hemispheric lateralization index for speech production. All participants also completed an electronic peg‐moving task to determine hand skill. As predicted, the DCD group showed a significantly reduced left lateralization pattern for the speech production task compared to controls. Performance on the motor skill task showed a clear preference for the dominant hand across both groups; however, the DCD group mean movement times were significantly higher for the non‐dominant hand. This is the first study of its kind to assess hand skill and speech lateralization in DCD. The results reveal a reduced leftwards asymmetry for speech and a slower motor performance. This fits alongside previous work showing atypical cerebral lateralization in DCD for other cognitive processes (e.g., executive function and short‐term memory) and thus speaks to debates on theories of the links between motor control and language production.     

The contribution of apraxic speech to working memory deficits in Parkinson's disease

This article links two formerly separate areas of research associated with Parkinson's disease (PD): speech and memory. It is proposed that speech deficits occur in PD not merely at the level of muscular control, as is commonly termed dysarthria, but also at the level of speech planning and programming, more aptly described as a form of apraxia. It is further argued that PD patient groups exhibit small deficits in verbal span, and the link between apraxic speech and verbal span is elucidated via Baddeley's (1986) model of working memory. An experiment is described in which aspects of speech of 36 PD and 43 healthy control subjects were rated and classified, and measures of span and articulation rate for words of different syllable lengths were taken. Twenty-three PD subjects had dysarthric speech, while 14 of them had apraxic speech, which was associated with lower memory span scores for longer words. It is concluded that apraxic speech can be a source of reduced memory span in PD. In addition to implications for rehabilitation and therapeutic work with PD sufferers, these findings advance our theoretical understanding of the Parkinsonian syndrome.     

Functional Topography of the Cerebellum in Verbal Working Memory

Speech—both overt and covert—facilitates working memory by creating and refreshing motor memory traces, allowing new information to be received and processed. Neuroimaging studies suggest a functional topography within the sub-regions of the cerebellum that subserve verbal working memory. Medial regions of the anterior cerebellum support overt speech, consistent with other forms of motor execution such as finger tapping, whereas lateral portions of the superior cerebellum support speech planning and preparation (e.g., covert speech). The inferior cerebellum is active when information is maintained across a delay, but activation appears to be independent of speech, lateralized by modality of stimulus presentation, and possibly related to phonological storage processes. Motor (dorsal) and cognitive (ventral) channels of cerebellar output nuclei can be distinguished in working memory. Clinical investigations suggest that hyper-activity of cerebellum and disrupted control of inner speech may contribute to certain psychiatric symptoms.     

Categorical speech perception deficits distinguish language and reading impairments in children

We examined categorical speech perception in school‐age children with developmental dyslexia or Specific Language Impairment (SLI), compared to age‐matched and younger controls. Stimuli consisted of synthetic speech tokens in which place of articulation varied from ‘b’ to ‘d’. Children were tested on categorization, categorization in noise, and discrimination. Phonological awareness skills were also assessed to examine whether these correlated with speech perception measures. We observed similarly good baseline categorization rates across all groups; however, when noise was added, the SLI group showed impaired categorization relative to controls, whereas dyslexic children showed an intact profile. The SLI group showed poorer than expected between‐category discrimination rates, whereas this pattern was only marginal in the dyslexic group. Impaired phonological awareness profiles were observed in both the SLI and dyslexic groups; however, correlations between phonological awareness and speech perception scores were not significant. The results of the study suggest that in children with language and reading impairments, there is a significant relationship between receptive language and speech perception, there is at best a weak relationship between reading and speech perception, and indeed the relationship between phonological and speech perception deficits is highly complex.     

Visuomotor tracking abilities of speakers with apraxia of speech or conduction aphasia

This investigation examined the visuomotor tracking abilities of persons with apraxia of speech (AOS) or conduction aphasia (CA). In addition, tracking performance was correlated with perceptual judgments of speech accuracy. Five individuals with AOS and four with CA served as participants, as well as an equal number of healthy controls matched by age and gender. Participants tracked predictable (sinusoidal) and unpredictable signals using jaw and lip movements transduced with strain gauges. Tracking performance in participants with AOS was poorest for predictable signals, with decreased kinematic measures of cross-correlation and gain ratio and increased target-tracker difference. In contrast, tracking of the unpredictable signal by participants with AOS was performed as well as for other groups (e.g. participants with CA, healthy controls). Performance of the subjects with AOS on the predictable tracking task was found to strongly correlate with perceptual judgments of speech. These findings suggest that motor control capabilities are impaired in AOS, but not in CA. Results suggest that AOS has its basis in motor programming deficits, not impaired motor execution.