Cerebellum and apraxia

Classical tenits posit that the role of the cerebellum is limited to pure sensorimotor control. However, evidence from clinical and imaging studies shows that the cerebellum is crucially involved in nonmotor cognitive and affective functions. Schmahmann and Sherman (1998) [1] introduced the cerebellar cognitive affective syndrome (CCAS), characterised by executive, visuo-spatial, affective and linguistic impairments caused by cerebellar pathology. Apraxia, as a planning, organisation and execution disorder of a skilled motor action (not caused by motor, sensory or intellectual impairment) [2], may be regarded to form part of the executive cluster of CCAS. Indeed, several anatomoclinical studies have confirmed involvement of the cerebellum in at least some types of apraxia, which adds to the nonmotor role of the cerebellum. According to Hugo Liepmann [3], apraxia is thought to evolve from a disruption of the creation, activation or retrieval of movement formulae. These formulae represent the idea of a movement as a visual or acoustic image and are stored in the left parietal lobe. The left prefrontal area subsequently associates these formulae with an inherently stored innervatory pattern to transfer the information to the left primary motor areas. The corpus callosum transfers this information to the right motor cortex if the movement is to be executed by the left limb [3]. Based on some recent clinical evidence we hypothesize that the cerebellum forms an intrinsic part of this connectionist model of Liepmann

Foreign accent syndrome: A typological overview

Foreign Accent Syndrome (FAS) is a motor speech disorder which causes patients to speak their native language with an accent different from speakers belonging to the same language community: the patient lacks the ability to make the phonemic and phonetic contrasts of his/her native language and demonstrates suprasegmental alterations which cause listeners to perceive the accent as distinctly ‘foreign’. In 1982, Whitaker proposed 4 diagnostic criteria for FAS: 1) the accent is considered by the patient, acquaintances and investigators as foreign, 2) it is unlike the patient’s accent before the insult, 3) the accent is clearly related to central nervous system damage, 4) there is no evidence in the patient’s background of him/her being a speaker of a foreign language (pp. 197- 198). Although FAS of “acquired neurogenic origin” is the most common variant of the disorder, there exists a “developmental”, “psychogenic” and “mixed variant” as well (Verhoeven and Mariën, 2010). In FAS of neurogenic origin the foreign accent is incited by a lesion affecting the central nervous system, often a stroke or brain trauma. However, FAS has also been attested in relation to MS (Villaverde-Gonzalez et al., 2003), tumor (Masao et al., 2011; Tomasino et al., 2013; Abel et al., 2009), as well as other pathologies affecting the CNS. Developmental FAS can be regarded as a subtype of neurogenic FAS; only here it is developmental in nature, affecting speech as it develops. In the psychogenic variant, a psychological/psychiatric disorder incites FAS, whereas the mixed variant is originally neurogenic in nature, but the accent change has such a profound effect on the patient’s psychological status that he/she internalizes it by further developing the accent in order ‘to create a more “believable” personality’ (Verhoeven and Mariën 2010, p. 600

Foreign accent syndrome as a developmental motor speech disorder

Introduction: Foreign Accent Syndrome (FAS) is a relatively rare motor speech disorder in which the pronunciation of a patient is perceived by listeners of the same language community as distinctly foreign. FAS has been well documented in adult patients with etiologically heterogeneous, though mostly vascular brain lesions affecting the motor speech network of the language dominant hemisphere. In addition, reports exist of adult patients in whom FAS was due to a psychiatric illness. Although FAS has been reported in children, such accounts are rare and have remained largely anecdotal in that there have been no formally documented cases of FAS as a developmental motor speech disorder. Methods and results: For the first time, we describe the clinical, cognitive and neurolinguistic findings in two patients who in the absence of a history of psychiatric illness or acquired brain damage already presented with FAS at an early stage of speech and language development. In the first patient “developmental FAS” was associated with a dysharmonic distribution of neurocognitive test results indicating slight underdevelopment of visuo-spatial skills and visual memory. The second patient presented with “developmental FAS” associated with specific language impairment (SLI). Independent support for a diagnosis of FAS in both patients was obtained in an accent attribution experiment in which groups of native speakers of (Belgian) Dutch assessed the type of foreign accent of a sample of the patients’ conversational speech. Both patients were judged as non-native speakers of Dutch by the majority of participants who predominantly identified the accent as French. Conclusion: This paper for the first time documents two patients who presented with FAS on a developmental basis. The finding that FAS does not only occur in the context of acquired brain damage or psychogenic illness but also exists as developmental motor speech impairment requires a re-definition of FAS as a clinical syndrome

A foreign speech accent in a case of conversion disorder

Objective: The aim of this paper is to report the psychiatric, neuroradiological and linguistic characteristics in a native speaker of Dutch who developed speech symptoms which strongly resemble Foreign Accent Syndrome. Background: Foreign Accent Syndrome is a rare speech production disorder in which the speech of a patient is perceived as foreign by speakers of the same speech community. This syndrome is generally related to focal brain damage. Only in few reported cases the Foreign Accent Syndrome is assumed to be of psychogenic and/or psychotic origin. Method: In addition to clinical and neuroradiological examinations, an extensive test battery of standardized neuropsychological and neurolinguistic investigations was carried out. Two samples of the patient's spontaneous speech were analysed and compared to a 500,000-words reference corpus of 160 normal native speakers of Dutch. Results: The patient had a prominent French accent in her pronunciation of Dutch. This accent had persisted over the past eight years and has become progressively stronger. The foreign qualities of her speech did not only relate to pronunciation, but also to the lexicon, syntax and pragmatics. Structural as well as functional neuroimaging did not reveal evidence that could account for the behavioural symptoms. By contrast psychological investigations indicated conversion disorder. Conclusions: To the best of our knowledge this is the first reported case of a foreign accent like syndrome in conversion disorder

Accent attribution in speakers with Foreign Accent Syndrome

Purpose: The main aim of this experiment was to establish the extent to which the impression of foreignness in speakers with Foreign Accent Syndrome (FAS) is in any way comparable to the impression of foreignness in speakers with a real foreign accent. Method: Three groups of listeners attributed accents to conversational speech samples of 5 FAS speakers which were embedded amongst those of 5 speakers with a real foreign accent and 5 native speaker controls. The listener groups differed in their familiarity with foreign accented speech and speech pathology. Results: The findings indicate that listeners’ perceptual reactions to the three groups of speakers are essentially different at all levels of analysis. The native speaker controls are unequivocally considered as native speakers of Dutch while the speakers with a real foreign accent are very reliably assessed as non-native speakers. The speakers with Foreign Accent Syndrome, however, are in some sense perceived as foreign and in some sense as native by listeners, but not as foreign as speakers with a real foreign accent nor as native as real native speakers. This result may be accounted for in terms of the trigger support model of foreign accent perception. Conclusions: The findings of the experiment is consistent with the idea that the very nature of the foreign accent in different in both groups of speakers, although it cannot be fully excluded that the perceived foreignness in the two groups is one of degree

Neurological aspects of foreign accent syndrome in stroke patients

Foreign Accent Syndrome (FAS) is an intriguing motor speech disorder which has captured the interest of the scientific community and media for decades. At the moment, there is no comprehensive model which can account for the pathophysiology of this disorder. This paper presents a review of 112 FAS cases published between 1907 and October 2016: these were analyzed with respect to demographic characteristics, lesion location, associated neurocognitive symptoms, and comorbid speech and language disorders. The analysis revealed that organic-neurogenic FAS is more frequent in women than in men. In organic-neurogenic FAS over half of the patients acquired the foreign accent after a stroke. Their lesions are typically located in the left supratentorial regions of the brain, and generally involve the primary motor cortex and premotor cortex (BA 4 and 6), and/or the basal ganglia. Although neurocognitive data are not consistently reported, vascular FAS patients regularly suffer frontal executive dysfunctions. On the basis of a careful comparison of the cognitive and theoretical accounts of FAS, AoS and ataxic dysarthria, it is concluded that FAS should be regarded a dual component motor speech disorder in which both planning and motor execution of speech may be affected

III-V-on-silicon anti-colliding pulse-type mode-locked laser

An anti-colliding pulse-type III–V-on-silicon passively mode-locked laser is presented for the first time based on a III–V-on-silicon distributed Bragg reflector as outcoupling mirror implemented partially underneath the III–V saturable absorber. Passive mode-locking at 4.83 GHz repetition rate generating 3 ps pulses is demonstrated. The generated fundamental RF tone shows a 1.7 kHz 3 dB linewidth. Over 9 mW waveguide coupled output power is demonstrated

Asymmetries in speech articulation as reflected on palatograms: a meta-study

This paper presents the results from an investigation of asymmetries in speech articulation on the basis of 1,502 previously published palatograms of a wide variety of speech sounds in a range of languages. For each palatogram, the direction and degree of tongue-palate contact was quantified by means of an index capturing the degree of lateral asymmetry. The results of this investigation show that lingual asymmetry in the articulation of speech sounds is substantial: 83% of the palatograms are asymmetrical. With respect to the direction of the asymmetry it is found that the asymmetry is more often towards the left side of the palate (45%) than to the right side (38%). Further analysis reveals that there are significant differences in both the direction and the degree of the asymmetry as a function of manner and place of articulation

Cerebellar induced differential polyglot aphasia: a neurolinguistic and fMRI study

Research has shown that linguistic functions in the bilingual brain are subserved by similar neural circuits as in monolinguals, but with extra-activity associated with cognitive and attentional control. Although a role for the right cerebellum in multilingual language processing has recently been acknowledged, a potential role of the left cerebellum remains largely unexplored. This paper reports the clinical and fMRI findings in a strongly right-handed (late) multilingual patient who developed differential polyglot aphasia, ataxic dysarthria and a selective decrease in executive function due to an ischemic stroke in the left cerebellum. fMRI revealed that lexical-semantic retrieval in the unaffected L1 was predominantly associated with activations in the left cortical areas (left prefrontal area and left postcentral gyrus), while naming in two affected non-native languages recruited a significantly larger bilateral functional network, including the cerebellum. It is hypothesized that the left cerebellar insult resulted in decreased right prefrontal hemisphere functioning due to a loss of cerebellar impulses through the cerebello-cerebral pathways