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Acquired apraxia of speech (AOS) is a disorder of speech motor planning/programming that is induced by a lesion to the left anterior ventral precentral sulcus. This study analyses neuroimaging data from AOS in order to propose and computationally test a mechanistic explanation of how the lesion leads to the characteristic of altered lexical stress in the disorder. Neuroimaging data from 31 participants with left hemisphere stroke (15 AOS) were reanalysed to guide a ‘lesioned’ version of the bilateral GODIVA neuro‐computational model of speech production. Structural MRI and resting‐state functional MRI measurements were used to decide the model's lesion extent and atypical neural processing, respectively. The ‘lesioned’ model was compared with a neurotypical model on the production of an exemplar utterance with different linguistic contexts. Analyses revealed the average lesion in the AOS participants extended over 22.25% of the left anterior ventral precentral sulcus. Functional connectivity in AOS was reduced between the lateral part of that region and the right motor cortex, as well as between the left and right motor cortices themselves. The version of the model that we altered in line with these findings produced lengthening of the second of two consecutive short syllables. The lengthened syllable was a word‐initial unstressed syllable, and consequently, its contrastiveness with the adjacent stressed syllable of the word was reduced. The agreement between simulation results and previously reported acoustic measurements from actual AOS patients lends support to our mechanistic explanation. In conclusion, simulations of the GODIVA model provided empirical support for a mechanistic explanation indicating permanent sub‐threshold cortical activity in AOS. As a result, the speech system becomes biased away from a motor control strategy based on motor programs and toward a strategy based on sensory feedback. This both lengthens brief syllables and interferes with the mechanism to shift between syllables, ultimately altering lexical stress. Analysis of the model's neural dynamics suggests the explanation can be generalised to various contexts where lexical stress is altered in AOS. This study reanalysed neuroimaging data from individuals with acquired apraxia of speech (AOS) to simulate lesion effects in the GODIVA neurocomputational speech model. The lesioned model reproduced characteristic lexical stress alterations in AOS, supporting a mechanistic explanation of the disorder involving an engaged feedback control system and altered transitions between syllables.

Eyelid apraxias are relatively uncommon movement disorders, often referring to apraxia of eyelid opening (AEO) while apraxia of eyelid closure (AEC) is even rarer. The later refers to the inability to volitional closure of the eyes while still having normal spontaneous automatic closure. Both are thought related to a dysfunction between neural pathways linking volition and execution of eyelid movement. Corticobasal syndrome (CBS) is a heterogeneous entity, with primary tauopathies including corticobasal degeneration (CBD) being the most frequent underlying pathology, though other etiologies are also possible. AEO is a well-described clinical feature of CBS; we present a case of CBS with apraxia of eyelid closure (AEC). Case report RESULT: A 72-year-old multilingual ambidextrous woman with an history of treated hyperparathyroidism was seen at the neurology clinic with a 5 years history of mood changes, effortful and nonfluent speech progressing to all languages (non-dominant English most affected), parkinsonism with cogwheel rigidity worse on left while apraxia and dystonic posturing was predominant on the right upper extremity. She had no dysphagia. In addition to above, neurological exam showed apraxia of speech and AEC with preserved reflex blinking, family commenting on preserved eye closure while sleeping. MoCA score was 14/30 and global cognitive impairment was observed on detailed neuropsychological testing. MRI brain showed mild atrophy slightly worse on right as well as bifrontal. DaT-scan was negative. She deferred other biomarkers testing. Our patient fits possible CBS per Armstrong's criteria. The clinical presentation as well as atrophy pattern favors a 4R-tauopathy like CBD. A normal DaT scan does not rule it out. AEC is rarer than AEO but can be seen in 4R tauopathies. Some fMRI in AEC research suggested possible insula involvement, an area frequently affected by atrophy in CBD. Other studies on AEC network support dysfunction in the right hemisphere particularly frontoparietal, which are also networks thought involved in emotional expressiveness through gestures and prosody. AEC is rare, can be seen after ischemic stroke but also in neurodegenerative disorders like primary tauopathies including CBD. More studies are needed to better understand its lesion network and relationship with language ones.

Background and objectives Nonfluent variant primary progressive aphasia (nfvPPA) and primary progressive apraxia of speech (PPAOS) can be precursors to corticobasal syndrome (CBS). Details on their progression remain unclear. We aimed to examine the clinical and neuroimaging evolution of nfvPPA and PPAOS into CBS. Methods We conducted a retrospective longitudinal study in 140 nfvPPA or PPAOS patients and applied the consensus criteria for possible and probable CBS for every visit, evaluating limb rigidity, akinesia, limb dystonia, myoclonus, ideomotor apraxia, alien limb phenomenon, and nonverbal oral apraxia (NVOA). Given the association of NVOA with AOS, we also modified the CBS criteria by excluding NVOA and assigned every patient to either a progressors or non-progressors group. We evaluated the frequency of every CBS feature by year from disease onset, and assessed gray and white matter volume loss using SPM12. Results Asymmetric akinesia, NVOA, and limb apraxia were the most common CBS features that developed; while limb dystonia, myoclonus, and alien limb were rare. Eighty-two patients progressed to possible CBS; only four to probable CBS. nfvPPA and PPAOS had a similar proportion of progressors, although nfvPPA progressed to CBS earlier ( p -value = 0.046), driven by an early appearance of limb apraxia ( p -value = 0.0041). The non-progressors and progressors both showed premotor/motor cortex involvement at baseline, with spread into prefrontal cortex over time. Discussion An important proportion of patients with nfvPPA and PPAOS progress to possible CBS, while they rarely develop features of probable CBS even after long follow-up.

Background The motor‐cognitive syndrome apraxia is a common stroke sequela and severely affects the outcome after stroke by impairing activities of daily living. Notably, like in many health conditions, there is a massive backlog regarding studies on sex differences in patients with apraxia despite common knowledge that sex influences praxis performance in healthy participants. We investigated putative sex differences in apraxic stroke patients at the behavioral and neural levels. Methods We retrospectively analysed the data of a cohort of 102 left‐hemisphere stroke patients in the (sub)acute phase who were apraxic according to the Cologne Apraxia Screening (KAS). We conducted voxel‐based lesion–symptom mapping (VLSM) to elucidate the lesion patterns. Further, in an age‐matched subsample (tolerance of 5 years) with equal numbers of men and women, behavioral comparisons and a VLSM analysis were conducted to explore differential sex‐related lesion patterns. Results Overall, apraxic deficits were associated with lesions in the parietal, temporal, and frontal regions in the cohort of 102 left‐hemisphere stroke patients. The age‐matched cohort consisted of 30 women and 30 men and showed no significant differences in demographic and clinical characteristics. There were no performance differences between men and women at the behavioral level regarding praxis functions. In contrast, VLSM revealed differential lesion patterns by sex. Male compared to female apraxic stroke patients significantly more often showed lesions that affected the left inferior frontal gyrus. Conclusion The data suggest a differential organization of the praxis system in men and women, warranting further exploration.

Limb apraxia is a higher-order motor disorder often occurring post-stroke, which affects skilled actions. It is assessed through tasks involving gesture production or pantomime, recognition, meaningless gesture imitation, complex figure drawing, single and multi-object use. A two-system model for the organisation of actions hypothesizes distinct pathways mediating praxis deficits via conceptual, ‘indirect’, and perceptual ‘direct’ routes to action. Traditional lesion- symptom mapping techniques have failed to identify these distinct routes. We assessed 29 left hemisphere stroke patients to investigate white matter disconnections on deficits of praxis tasks from the Birmingham Cognitive Screening. White matter disconnection maps derived from patients’ structural T1 lesions were created using a diffusion-weighted healthy participant dataset acquired from the human connectome project (HCP). Initial group-level regression analyses revealed significant disconnection between occipital lobes via the splenium of the corpus callosum and involvement of the inferior longitudinal fasciculus in meaningless gesture imitation deficits. There was a trend of left fornix disconnection in gesture production deficits. Further, voxel-wise Bayesian Crawford single-case analyses performed on two patients with the most severe meaningless gesture imitation and meaningful gesture production deficits, respectively, confirmed distinct posterior interhemispheric disconnection, for the former, and disconnections between temporal and frontal areas via the fornix, rostrum of the corpus callosum and anterior cingulum, for the latter. Our results suggest distinct pathways associated with perceptual and conceptual deficits akin to ‘direct’ and ‘indirect’ action routes, with some patients displaying both. Larger studies are needed to validate and elaborate on these findings, advancing our understanding of limb apraxia.

Progressive apraxia of speech (PAOS) is a 4R tauopathy characterized by difficulties with motor speech planning. Neurodegeneration in PAOS targets the premotor cortex, particularly the supplementary motor area (SMA), with degeneration of white matter (WM) tracts connecting premotor and motor cortices and Broca's area observed on diffusion tensor imaging (DTI). We aimed to assess flortaucipir uptake across speech‐language‐related WM tracts identified using DTI tractography in PAOS. Twenty‐two patients with PAOS and 26 matched healthy controls were recruited by the Neurodegenerative Research Group (NRG) and underwent MRI and flortaucipir‐PET. The patient population included patients with primary progressive apraxia of speech (PPAOS) and non‐fluent variant/agrammatic primary progressive aphasia (agPPA). Flortaucipir PET scans and DTI were coregistered using rigid registration with a mutual information cost function in subject space. Alignments between DTI and flortaucipir PET were inspected in all cases. Whole‐brain tractography was calculated using deterministic algorithms by a tractography reconstruction tool (DSI‐studio) and specific tracts were identified using an automatic fiber tracking atlas‐based method. Fractional anisotropy (FA) and flortaucipir standardized uptake value ratios (SUVRs) were averaged across the frontal aslant tract, arcuate fasciculi, inferior frontal‐occipital fasciculus, inferior and middle longitudinal fasciculi, as well as the SMA commissural fibers. Reduced FA (p < .0001) and elevated flortaucipir SUVR (p = .0012) were observed in PAOS cases compared to controls across all combined WM tracts. For flortaucipir SUVR, the greatest differentiation of PAOS from controls was achieved with the SMA commissural fibers (area under the receiver operator characteristic curve [AUROC] = 0.83), followed by the left arcuate fasciculus (AUROC = 0.75) and left frontal aslant tract (AUROC = 0.71). Our findings demonstrate that flortaucipir uptake is increased across WM tracts related to speech/language difficulties in PAOS. Structural connectomics assessment of the supplementary motor area (SMA) in progressive apraxia of speech (PAOS) subjects. White matter connectivity representation from cortical regions involved in the language network (LN) shows lower fractional anisotropy (FA) and larger mean diffusivity (MD) and standardized uptake value ratio (SUVR) values than control. The addition of SMA to the speech and LN demonstrates further FA decrease in MD and SUVR increase likely due to the involvement of SMA in the disease.

The anatomical relationship between speech apraxia (SA) and oral apraxia (OA) is still unclear. To shed light on this matter we studied 137 patients with acute ischaemic left-hemisphere stroke and performed support vector regression-based, multivariate lesion–symptom mapping. Thirty-three patients presented with either SA or OA. These two symptoms mostly co-occurred (n = 28), except for few patients with isolated SA (n = 2) or OA (n = 3). All patient with either SA or OA presented with aphasia (p < 0.001) and these symptoms were highly associated with apraxia (p < 0.001). Co-occurring SA and OA were predominantly associated with insular lesions, while the insula was completely spared in the five patients with isolated SA or OA. Isolated SA occurred in case of frontal lesions (prefrontal gyrus and superior longitudinal fasciculus), while isolated OA occurred in case of either temporoparietal or striatocapsular lesions. Our study supports the notion of a predominant, but not exclusive, role of the insula in verbal and non-verbal oral praxis, and indicates that frontal regions may contribute exclusively to verbal oral praxis, while temporoparietal and striatocapsular regions contribute to non-verbal oral praxis. However, since tests for SA and OA so far intrinsically also investigate aphasia and apraxia, refined tests are warranted.

Purpose: Our purpose was to create a comprehensive review of speech impairment in frontotemporal dementia (FTD), primary progressive aphasia (PPA), and progressive apraxia of speech in order to identify the most effective measures for diagnosis and monitoring, and to elucidate associations between speech and neuroimaging. Method: Speech and neuroimaging data described in studies of FTD and PPA were systematically reviewed. A meta-analysis was conducted for speech measures that were used consistently in multiple studies. Results: The methods and nomenclature used to describe speech in these disorders varied between studies. Our meta-analysis identified 3 speech measures which differentiate variants or healthy control-group participants (e.g., nonfluent and logopenic variants of PPA from all other groups, behavioral-variant FTD from a control group). Deficits within the frontal-lobe speech networks are linked to motor speech profiles of the nonfluent variant of PPA and progressive apraxia of speech. Motor speech impairment is rarely reported in semantic and logopenic variants of PPA. Limited data are available on motor speech impairment in the behavioral variant of FTD. Conclusions: Our review identified several measures of speech which may assist with diagnosis and classification, and consolidated the brain-behavior associations relating to speech in FTD, PPA, and progressive apraxia of speech.

Patients with progressive apraxia of speech (PAOS) often develop atypical parkinsonian features suggestive of corticobasal syndrome (CBS) or progressive supranuclear palsy (PSP), and typically have an underlying 4-repeat tauopathy at autopsy. We describe three cases of PAOS with underlying Pick’s disease, a 3-repeat tauopathy, who lacked CBS or PSP features during life. We reviewed patients enrolled in the Neurodegenerative Research Group’s ongoing studies on speech and language disorders and identified those with PAOS who had autopsy-confirmed Pick’s disease. All patients had comprehensive neurologic, speech-language, and neuropsychological assessments, as well as multimodal neuroimaging, during life. Three female patients presented with phonetic PAOS without parkinsonism. Patient 1 had speech onset at age 54, later developed behavioral variant frontotemporal dementia (bvFTD), and died at 64. Patient 2 had speech onset at 47, early bvFTD features, prominent frontal and temporal involvement, and died at 53. Patient 3 had speech onset at 58, minimal behavioral changes, primarily frontal involvement on imaging, and died at 63. Our findings highlight that Pick's disease can present with PAOS and may be distinguished from 4R-tau PAOS by an absence of motoric CBS/PSP features and, in some cases, by prominent temporal hypometabolism with bvFTD development. These atypical features may prove useful in the antemortem identification of Pick's disease as a cause of PAOS. •Progressive apraxia of speech typically shares features with 4R tauopathies.•We report three autopsy-confirmed cases of PAOS with underlying 3R tau.•Early behavioral changes and lack of parkinsonism may be clinical clues to 3R tau.•Prominent temporal involvement on imaging may be a marker of 3R tau.

BackgroundMotor deficit after stroke is related to regional anatomical damage.ObjectiveTo examine the influence of lesion location on upper limb motor deficit in chronic patients with stroke.MethodsLesion likelihood maps were created from T1-weighted structural MRI in 33 chronic patients with stroke with either purely subcortical lesions (SC, n=19) or lesions extending to any of the cortical motor areas (CM, n=14). We estimated lesion likelihood maps over the whole brain and applied multivoxel pattern analysis to seek the contribution weight of lesion likelihood to upper limb motor deficit. Among 5 brain regions of interest, the brain region with the greatest contribution to motor deficit was determined for each subgroup.ResultsThe corticospinal tract was most likely to be damaged in both subgroups. However, while damage in the corticospinal tract was the best indicator of motor deficit in the SC patients, motor deficit in the CM patients was best explained by damage in brain areas activated during handgrip.ConclusionsQuantification of structural damage can add to models explaining motor outcome after stroke, but assessment of corticospinal tract damage alone is unlikely to be sufficient when considering patients with stroke with a wide range of lesion topography.