Limb apraxia in patients with damage confined to the left basal ganglia and thalamus

The Neurocognitive Bases of Meaningful Intransitive Gestures: A Systematic Review and Meta-analysis of Neuropsychological Studies

Researchers and clinicians have long used meaningful intransitive (i.e., not tool-related; MFI) gestures to assess apraxia-a complex and frequent motor-cognitive disorder. Nevertheless, the neurocognitive bases of these gestures remain incompletely understood. Models of apraxia have assumed that meaningful intransitive gestures depend on either long-term memory (i.e., semantic memory and action lexicons) stored in the left hemisphere, or social cognition and the right hemisphere. This meta-analysis of 42 studies reports the performance of 2659 patients with either left or right hemisphere damage in tests of meaningful intransitive gestures, as compared to other gestures (i.e., MFT or meaningful transitive and MLI or meaningless intransitive) and cognitive tests. The key findings are as follows: (1) deficits of meaningful intransitive gestures are more frequent and severe after left than right hemisphere lesions, but they have been reported in both groups; (2) we found a transitivity effect in patients with lesions of the left hemisphere (i.e., meaningful transitive gestures more difficult than meaningful intransitive gestures) but a "reverse" transitivity effect in patients with lesions of the right hemisphere (i.e., meaningful transitive gestures easier than meaningful intransitive gestures); (3) there is a strong association between meaningful intransitive and transitive (but not meaningless) gestures; (4) isolated deficits of meaningful intransitive gestures are more frequent in cases with right than left hemisphere lesions; (5) these deficits may occur in the absence of language and semantic memory impairments; (6) meaningful intransitive gesture performance seems to vary according to the emotional content of gestures (i.e., body-centered gestures and emotional valence-intensity). These findings are partially consistent with the social cognition hypothesis. Methodological recommendations are given for future studies.

Anarchy in the brain: Behavioural and neuroanatomical core of the anarchic hand syndrome

An individual's inability to control the movements of their own hand is known as the Anarchic Hand Syndrome. The hand may perform apparently purposeful actions but acts as if it has a will of its own. Although the syndrome was first described over a century ago, the nature of the condition remains, for the most part, obscure, in particular in terms of the definition of the main symptoms and the underlying neural networks. The present study compares the results from in-depth assessments, made at repeated intervals (2, 4 and 7 months from the lesion onset) of the anarchic hand symptoms in three patients suffering from various different forms of brain damage. An investigation of direct grey matter damage and structural connectivity allowed us to compare the grey matter lesions and white matter disconnections in the three patients. A "core" characteristic relating to anarchic hand symptoms was identified, involving, in particular, both apparently purposeful movements (i.e., magnetic apraxia, grasping, bimanual incoordination, disorders in manual dexterity and action sequencing) and non-purposeful movements (i.e., levitation, synkinesis and mirror movements). Furthermore, ideomotor apraxia may also be associated with this syndrome. No overlapping areas of grey matter lesions were found in the three patients. In contrast, a pattern of common white matter disconnections was found, which involves inter-hemispheric disconnections (via corpus callosum), the long intra-hemispheric tracts (via SLF, IFOF and Arcuate) and the descendent tracts (corticospinal tract). These results are discussed in terms of awareness of motor intention.

Association of Circumscribed Subcortical Gray and White Matter Lesions With Apraxic Deficits in Patients With Left Hemisphere Stroke

BACKGROUND AND OBJECTIVES

Apraxia is commonly attributed to left hemisphere (LH) lesions of the cortical fronto-temporo-parietal praxis networks or white matter lesions causing disconnections between cortical nodes. By contrast, the contribution of lesions to the subcortical gray matter, that is, basal ganglia or thalamus, to apraxic deficits remains controversial. Here, we investigate whether damage to these subcortical gray matter structures (i.e., caudate nucleus, putamen, globus pallidus, and thalamus) or the adjacent white matter tracts was associated with apraxic deficits.

METHODS

We identified patients with distinct subcortical lesions with and without apraxia from a large retrospective sample of subacute LH ischemic stroke patients (n = 194). To test which subcortical structures (caudate nucleus, putamen, globus pallidus, thalamus, and adjacent white matter tracts), when lesioned, contributed to apraxic deficits, we statistically compared the proportion of lesioned voxels within subcortical gray and white matter structures between the apraxic and nonapraxic patients.

RESULTS

Of the 194 stroke patients screened, 39 (median age = 65 years, range 30-82 years; median time poststroke at the apraxia assessment = 7 days, range 1-44 days) had lesions confined to subcortical regions (gray and white matter). Eleven patients showed apraxic deficits when imitating gestures or pantomiming object use. Region-wise statistical lesion comparison (controlled for lesion size) revealed a more significant proportion of damage ('lesion load') in the caudate nucleus in apraxic stroke patients (mean difference = 6.9%, 95% CI 0.4-13.3, p = 0.038, η p 2 = 0.11). By contrast, apraxic patients had lower lesion load in the globus pallidus (mean difference = 9.9%, 95% CI 0.1-19.8, p = 0.048, η p 2 = 0.10), whereas the lesion load in other subcortical structures (putamen, thalamus, and adjacent white matter tracts) did not differ significantly between the apraxic and nonapraxic patients.

DISCUSSION

These findings provide new insights into the subcortical anatomy of apraxia after LH stroke, suggesting a specific contribution of caudate nucleus lesions to apraxic deficits.

Mapping the human praxis network: an investigation of white matter disconnection in limb apraxia of gesture production

Left hemispheric cerebral stroke can cause apraxia, a motor cognitive disorder characterized by deficits of higher-order motor skills such as the failure to accurately produce meaningful gestures. This disorder provides unique insights into the anatomical and cognitive architecture of the human praxis system. The present study aimed to map the structural brain network that is damaged in apraxia. We assessed the ability to perform meaningful gestures with the hand in 101 patients with chronic left hemisphere stroke. Structural white matter fibre damage was directly assessed by diffusion tensor imaging and fractional anisotropy mapping. We used multivariate topographical inference on tract-based fractional anisotropy topographies to identify white matter disconnection associated with apraxia. We found relevant pathological white matter alterations in a densely connected fronto-temporo-parietal network of short and long association fibres. Hence, the findings suggest that heterogeneous topographical results in previous lesion mapping studies might not only result from differences in study design, but also from the general methodological limitations of univariate topographical mapping in uncovering the structural praxis network. A striking role of middle and superior temporal lobe disconnection, including temporo-temporal short association fibres, was found, suggesting strong involvement of the temporal lobe in the praxis network. Further, the results stressed the importance of subcortical disconnections for the emergence of apractic symptoms. Our study provides a fine-grain view into the structural connectivity of the human praxis network and suggests a potential value of disconnection measures in the clinical prediction of behavioural post-stroke outcome.

The Role of White Matter Disconnection in the Symptoms Relating to the Anarchic Hand Syndrome: A Single Case Study

The anarchic hand syndrome refers to an inability to control the movements of one’s own hand, which acts as if it has a will of its own. The symptoms may differ depending on whether the brain lesion is anterior, posterior, callosal or subcortical, but the relative classifications are not conclusive. This study investigates the role of white matter disconnections in a patient whose symptoms are inconsistent with the mapping of the lesion site. A repeated neuropsychological investigation was associated with a review of the literature on the topic to identify the frequency of various different symptoms relating to this syndrome. Furthermore, an analysis of the neuroimaging regarding structural connectivity allowed us to investigate the grey matter lesions and white matter disconnections. The results indicated that some of the patient’s symptoms were associated with structures that, although not directly damaged, were dysfunctional due to a disconnection in their networks. This suggests that the anarchic hand may be considered as a disconnection syndrome involving the integration of multiple antero-posterior, insular and interhemispheric networks. In order to comprehend this rare syndrome better, the clinical and neuroimaging data need to be integrated with the clinical reports available in the literature on this topic.

High Frequency of Crossed Aphasia in Dextral in an Italian Cohort of Patients with Logopenic Primary Progressive Aphasia

BACKGROUND

Primary progressive aphasia (PPA) has been described as a neurodegenerative language disorder mainly affecting the left hemisphere. Few cases of right hemisphere damage in right-handed PPA subjects have been reported. This condition, named crossed aphasia in dextral (CAD), is relatively rare and probably related to an alteration during neurodevelopment of language networks.

OBJECTIVE

To explore the prevalence of CAD in an Italian cohort of 68 PPA patients, in order to evaluate whether right hemisphere language lateralization could be a risk factor for PPA.

METHODS

Clinical-demographic and cerebral [18F]-fluorodeoxyglucose positron emission tomography ([18F]FDG-PET) scan were analyzed, resulting in 23 logopenic variant (lvPPA) patients, 26 non-fluent variant (nfvPPA) patients, and 19 semantic variant (svPPA) patients. SPM single subject routine was performed for diagnostic purposes in order to identify the hypometabolic pattern of each patient. Based on brain metabolic profile, PPA patients were divided in right and left lvPPA, nfvPPA, and svPPA. [18F]FDG-PET group analyses were performed with SPM two-sample t-test routine.

RESULTS

26% of lvPPA cases were identified as CAD based on right hypometabolic pattern. CAD patients did not differ from left lvPPA regarding demographic features and general cognitive performance; however, they performed better in specific working memory tasks and showed brain hypometabolism limited to the superior, middle, and supramarginal temporal gyri.

CONCLUSION

Atypical lateralization of language function could determine a vulnerability of the phonological language loop and in that way could be a risk factor for lvPPA.

Primary Progressive Aphasia: Natural History in an Italian Cohort

BACKGROUND/AIMS

Few longitudinal studies have explored the progression of cognitive and functional impairment of patients with primary progressive aphasia (PPA). The aims of the study were to describe the clinical, neuroimaging, and genetic features of a cohort of 68 PPA patients, and to outline the natural history of the disease.

MATERIALS AND METHODS

A sample of 23 patients with the logopenic variant, 26 with the nonfluent/agrammatic variant, and 19 with the semantic variant was retrospectively collected and followed-up for a maximum of 6 years. Clinical-neuropsychological assessment, fluorodeoxyglucose positron emission tomographic imaging, and genetic analyses were acquired at baseline. Disease progression was evaluated in terms of language impairment, global cognitive decline, and functional dependency.

RESULTS

During follow-up, one third of subjects presented total language loss, and 20% severe functional dependency. Global cognitive decline after the first year (hazard ratio, 5.93; confidence interval, 1.63-21.56) and high schooling (hazard ratio, 0.07; confidence interval, 0.008-0.74) represented risk factors for functional impairment. The apolipoprotein E status was associated with the progression of cognitive decline. Positive family history for dementia was frequent and 3 genetic autosomal dominant mutations were identified.

CONCLUSIONS

There were no differences in the progression of PPA subtypes. Genetics plays an important role in disease onset and progression.

The language profile of progressive supranuclear palsy

A progressive speech/language disorder, such as the non fluent/agrammatic variant of primary progressive aphasia and progressive apraxia of speech, can be due to neuropathologically verified Progressive Supranuclear Palsy (PSP). The prevalence of linguistic deficits and the linguistic profile in PSP patients who present primarily with a movement disorder is unknown. In the present study, we investigated speech and language performance in a sample of clinically diagnosed PSP patients using a comprehensive language battery, including, besides traditional language tests, a detailed analysis of connected speech (picture description task assessing 26 linguistic features). The aim was to identify the most affected linguistic levels in seventeen PSP with a movement disorder presentation, compared to 21 patients with Parkinson's disease and 27 healthy controls. Machine learning methods were used to detect the most relevant language tests and linguistic features characterizing the language profile of PSP patients. Our results indicate that even non-clinically aphasic PSP patients have subtle language deficits, in particular involving the lexical-semantic and discourse levels. Patients with the Richardson's syndrome showed a lower performance in the word comprehension task with respect to the other PSP phenotypes with predominant frontal presentation, parkinsonism and progressive gait freezing. The present findings support the usefulness of a detailed language assessment in all patients in the PSP spectrum.

No evidence of effectiveness of mirror therapy early after stroke: an assessor-blinded randomized controlled trial

OBJECTIVE

The aim of this study was to investigate the efficacy of mirror therapy on upper-limb recovery in early post-stroke patients.

DESIGN

Assessor-blinded randomized controlled trial.

SETTING

Inpatient rehabilitation clinic.

SUBJECTS

A total of 40 patients with upper-limb impairment due to a first-ever ischaemic or haemorrhagic stroke, within four weeks from the cerebrovascular accident.

INTERVENTION

The intervention group received mirror therapy, while the control group received sham therapy. During mirror therapy, patients' sound hand was reflected by a mirror. During sham therapy, an opaque surface replaced the mirror-reflecting surface. Both the mirror therapy and sham therapy groups practised their sound hand with exercises, ranging from the simple elbow flexion-extension to complex tasks (e.g. reaching and grasping). Mirror therapy and sham therapy were added to conventional rehabilitation.

MAIN MEASURES

Primary outcome includes Fugl-Meyer upper extremity scale. Secondary outcomes include action research arm test (ARAT) and functional independence measure (FIM) scale. Outcomes were measured at the beginning (T0) and end (T1) of the treatment.

RESULTS

At baseline, both groups (sham therapy vs. mirror therapy; mean (SD)) were comparable for Fugl-Meyer (30.9 (23.9) vs. 28.5 (21.8)), ARAT (25.1 (25.5) vs. 23.5 (24)) and FIM (71.0 (20.6) vs. 72.9 (17.8)) scores. At the end of the treatment, both groups significantly improved in the Fugl-Meyer (40.6 (21.3) vs. 38.3 (23.4)), ARAT (31.9 (23.0) vs. 30 (24.1)) and FIM (100.3 (21.9) vs. 99.4 (22.6)) scores. However, at T1, no significant difference was observed between the sham therapy and mirror therapy groups, neither for the Fugl-Meyer, nor for ARAT and FIM scores.

CONCLUSION

Compared with sham therapy, mirror therapy did not add additional benefit to upper-limb recovery early after stroke.

Longitudinal MRI Evaluation of Ischemic Stroke in the Basal Ganglia of a Rhesus Macaque (Macaca mulatta) with Seizures

An adult rhesus macaque developed seizures after the induction of ischemic stroke. Initially, on the day of surgery, a focal ischemic lesion was present exclusively in the right caudate nucleus. By 48 h after stroke induction, the lesion had extended into the putamen, when a seizure was observed. Our report highlights the temporal changes in infarction of unilateral basal ganglia after acute stroke and the accompanying clinical symptoms. This unusual case may provide additional information regarding the involvement of the basal ganglia in seizures, given that prior case reports and studies usually have not described the temporal and spatial evolution of the lesion before clinical symptoms emerge.

Bilateral functional connectivity at rest predicts apraxic symptoms after left hemisphere stroke

Increasing evidence indicates that focal lesions following stroke cause alterations in connectivity among functional brain networks. Functional connectivity between hemispheres has been shown to be particularly critical for predicting stroke-related behavioral deficits and recovery of motor function and attention. Much less is known, however, about the relevance of interhemispheric functional connectivity for cognitive abilities like praxis that rely on strongly lateralized brain networks. In the current study, we examine correlations between symptoms of apraxia-a disorder of skilled action that cannot be attributed to lower-level sensory or motor impairments-and spontaneous, resting brain activity in functional MRI in chronic left hemisphere stroke patients and neurologically-intact control participants. Using a data-driven approach, we identified 32 regions-of-interest in which pairwise functional connectivity correlated with two distinct measures of apraxia, even when controlling for age, head motion, lesion volume, and other artifacts: overall ability to pantomime the typical use of a tool, and disproportionate difficulty pantomiming the use of tools associated with different, competing use and grasp-to-move actions (e.g., setting a kitchen timer versus picking it up). Better performance on both measures correlated with stronger interhemispheric functional connectivity. Relevant regions in the right hemisphere were often homologous to left hemisphere areas associated with tool use and action. Additionally, relative to overall pantomime accuracy, disproportionate difficulty pantomiming the use of tools associated with competing use and grasp actions was associated with weakened functional connectivity among a more strongly left-lateralized and peri-Sylvian set of brain regions. Finally, patient performance on both measures of apraxia was best predicted by a model that incorporated information about lesion location and functional connectivity, and functional connectivity continued to explain unique variance in behavior even after accounting for lesion loci. These results indicate that interhemispheric functional connectivity is relevant even for a strongly lateralized cognitive ability like praxis and emphasize the importance of the right hemisphere in skilled action.

Impaired imitation of gestures in mild dementia: comparison of dementia with Lewy bodies, Alzheimer's disease and vascular dementia

INTRODUCTION

To examine whether imitation of gestures provided useful information to diagnose early dementia in elderly patients.

METHODS

Imitation of finger and hand gestures was evaluated in patients with mild dementia; 74 patients had dementia with Lewy bodies (DLB), 100 with Alzheimer's disease (AD) and 52 with subcortical vascular dementia (SVaD).

RESULTS

Significantly, more patients with DLB (32.4%) compared with patients with AD (5%) or SVaD (11.5%) had an impaired ability to imitate finger gestures bilaterally. Also, significantly, more patients with DLB (36.5%) compared with patients with AD (5%) or SVaD (15.4%) had lower mean scores of both hands. In contrast, impairment of the imitation of bimanual gestures was comparable among the three patient groups (DLB 50%, AD 42%, SVaD 42.3%).

DISCUSSION

Our study revealed that imitation of bimanual gestures was impaired non-specifically in about half of the patients with mild dementia, whereas imitation of finger gestures was significantly more impaired in patients with early DLB than in those with AD or SVaD. Although the sensitivity was not high, the imitation tasks may provide additional information for diagnosis of mild dementia, especially for DLB.

Poststroke depression and its multifactorial nature: results from a prospective longitudinal study

OBJECTIVE

Poststroke depression (PSD) is commonly observed in stroke patients and has a negative impact on functional outcome and quality of life. Therefore, a prospective, longitudinal epidemiological study was conducted aiming to determine prevalence and risk factors for PSD at 1, 3, 6, 12 and 18 months poststroke.

METHODS

A total of 222 patients were included in the study and 201 patients entered data analysis. Demographic data, vascular risk factors, stroke characteristics, functional and neurocognitive outcome measures and psychosocial factors were considered as potential risk factors for PSD. Clinically significant signs and symptoms of PSD were quantified by means of the Cornell Scale for Depression (CSD) and the Montgomery and Åsberg Depression Rating Scale (MADRS).

RESULTS

PSD was present at 1, 3, 6, 12 and 18 months poststroke in 24.5%, 27.1%, 28.3%, 19.8% and 26.3% of the patients respectively. Univariate regression analyses revealed that PSD was significantly associated with stroke severity, physical disability, cognitive impairment and stroke outcome during the 18 months time frame of the study. Reduced social activities and the presence of apraxia were consistently associated with PSD whereas aphasia was only significantly associated in the first 6 months after stroke. Patients with relational problems had a 3 times greater risk of becoming depressed at 18 months poststroke than patients without relational problems (OR=3.09; 95% CI=1.31-7.26).

CONCLUSIONS

Risk factors for PSD seem variable indicating the need for clinicians to consider the dynamic and multifactorial nature of PSD emphasizing the importance of a rigorous and long-term monitoring and support of stroke patients and their caregivers.

Higher-level gait disorders: an open frontier

The term higher-level gait disorders (HLGD) defines a category of balance and gait disorders that are not explained by deficits in strength, tone, sensation, or coordination. HLGD are characterized by various combinations of disequilibrium and impaired locomotion. A plethora of new imaging techniques are beginning to determine the neural circuits that are the basis of these disorders. Although a variety of neurodegenerative and other pathologies can produce HLGD, the most common cause appears to be microvascular disease that causes white-matter lesions and thereby disrupts balance/locomotor circuits.

Ideomotor apraxia in agrammatic and logopenic variants of primary progressive aphasia

There are few studies examining praxis in subjects with primary progressive aphasia. The aim of this study was to examine the pattern and severity of ideomotor apraxia in subjects with logopenic and agrammatic variants of primary progressive aphasia and to determine if the presence of ideomotor apraxia correlated with specific neuroanatomical structural abnormalities. Subjects with primary progressive aphasia were prospectively recruited and classified according to published criteria. Using the apraxia subtest of the Western Aphasia Battery, pattern and severity of ideomotor apraxia was examined in all subjects diagnosed with agrammatic and logopenic variants of primary progressive aphasia. The study included 47 subjects, 21 diagnosed with agrammatic variant of primary progressive aphasia and 26 with logopenic variant primary progressive aphasia. Subjects with agrammatic aphasia were older at onset than the logopenic variant (67.2 vs. 61.7 years, p = 0.02), but there was no difference in illness duration prior to evaluation. Those with logopenic aphasia showed more cognitive impairment on the Mini-Mental Status Examination (agrammatic = 26.7/30, logopenic = 22/30, p = 0.002), and a trend for more severe language impairment as measured by the Western Aphasia Battery-Aphasia Quotient (agrammatic = 82.3, logopenic = 75.2, p = 0.11). Strong correlations were found between Western Aphasia Battery-Aphasia Quotient and total apraxia, instrumental apraxia, and complex apraxia, while average to modest correlations were seen with upper limb apraxia and facial apraxia. After adjusting for age, mental status performance, and Western Aphasia Battery-Aphasia Quotient score, those with agrammatic aphasia had a higher degree of total apraxia (p = 0.004), facial apraxia (p = 0.03), instrumental apraxia (p = 0.0006), and complex apraxia (p = 0.0006) than those with logopenic aphasia. The agrammatic variant of primary progressive aphasia was associated with greater praxis deficits but less cognitive impairment than the logopenic variant. The presence of ideomotor apraxia was associated with grey matter loss in the left lateral premotor cortex with extension into the motor cortex. These findings suggest that although some affected areas in the agrammatic and logopenic variants of primary progressive aphasia overlap, there exists an area that is more affected in the agrammatic variant than the logopenic variant that accounts for the greater association of agrammatic aphasia with ideomotor apraxia.

Apraxia for differentiating Alzheimer's disease from subcortical vascular dementia and mild cognitive impairment

Although ideomotor limb apraxia is considered to be a typical sign of cortical pathologies such as Alzheimer's disease (AD), it has been also reported in subcortical neurodegenerative diseases and vascular lesions. We aimed to investigate the difference between AD, subcortical vascular dementia (SVaD) and mild cognitive impairment (MCI) patients by means of ideomotor limb apraxia frequency and severity. Ninety-six AD, 72 SVaD, and 84 MCI patients were assessed with the mini-mental status examination (MMSe), clinical dementia rating (CDR) and the apraxia screening test of TULIA (AST). Apraxia was significantly more frequent in the AD patients (32.3%) than in both of the SVaD (16.7%) and MCI (4.8%) patients. The frequency of apraxia was also significantly higher in SVaD patients than in MCI patients. AD patients had significantly lower apraxia scores than both SVaD and MCI patients. In addition, a significant difference was found between SVaD and MCI patients in terms of apraxia scores. These results suggest that the widespread belief of the association between apraxia and cortical dementias is not exactly correct. The significant difference between both of the dementia groups and the MCI patients suggests that the absence of apraxia can be an indicator for MCI diagnosis.

Apraxia

Humans need to perform skilled movements to successfully interact with their environment as well as take care of themselves and others. These important skilled purposeful actions are primarily performed by the forelimb, and the loss of these skills is called apraxia. This review describes the means of testing, the pathophysiology, and the clinical characteristics that define five different general forms of forelimb apraxia including: (1) ideational apraxia, an inability to correctly sequence a series of acts leading to a goal; (2) conceptual apraxia, a loss of mechanical tool knowledge; (3) ideomotor apraxia, a loss of the knowledge of how when making transitive and intransitive movements to correctly posture and move the forelimb in space; (4) dissociation apraxia, a modality-specific deficit in eliciting learned skilled acts; and (5) limb-kinetic apraxia, a loss of hand-finger deftness.

Apraxia related with subcortical lesions due to cerebrovascular disease

OBJECTIVES

To examine whether ideomotor apraxia exists in patients with subcortical ischemic lesions.

PATIENTS AND METHODS

A matched-control, prospective and multi-centered research design was used. Ideomotor apraxia, anxiety and depression were assessed by the Movement Imitation Test and the Hamilton scales, respectively.

RESULTS

Forty two consecutive patients with subcortical ischemic stroke and an equal number of healthy participants, matched in age and sex were included. Paired-sample t-tests showed that patients had significantly more apractic elements in their movements (t = 5.03, P < 0.01), higher anxiety (t = -2.55, P = 0.0014) and depression levels (t = -2.61, P = 0.012) than their healthy matched participants. Participants with higher anxiety and depression scores performed worse on the Movement Imitation Test.

CONCLUSIONS

Ischemic damage of subcortical modular systems may affect praxis.

Embodied semantics for actions: findings from functional brain imaging

The theory of embodied semantics for actions specifies that the sensory-motor areas used for producing an action are also used for the conceptual representation of the same action. Here we review the functional imaging literature that has explored this theory and consider both supporting as well as challenging fMRI findings. In particular we address the representation of actions and concepts as well as literal and metaphorical phrases in the premotor cortex.

Action comprehension in aphasia: linguistic and non-linguistic deficits and their lesion correlates

We tested aphasic patients' comprehension of actions to examine processing deficits in the linguistic and non-linguistic domains and their lesion correlates. Twenty-nine left-hemisphere injured patients and 18 age-matched control subjects matched pictured actions (with the objects missing) or their linguistic equivalents (printed sentences with the object missing) to one of two visually-presented pictures of objects. Aphasic patients performed poorly not only in the linguistic domain but also in the non-linguistic domain. A subset of the patients, largely consisting of severe and non-fluent aphasics, showed a greater deficit in the linguistic domain compared with the non-linguistic domain and across the patient group, deficits in the linguistic and non-linguistic domains were not tightly correlated. Poor performance in pantomime interpretation was associated with lesions in the inferior frontal, premotor and motor cortex, a portion of somatosensory cortex, and the caudate, while poor reading comprehension of actions was associated with lesions around the anterior superior temporal lobe, the anterior insula and the anterior portion of the inferior parietal lobe. Lesion size did not correlate with deficits. The lesion results for pantomime interpretation deficits demonstrate that lesions in the frontal component of the human analog of the "mirror neuron system" are associated with deficits in non-linguistic action understanding. For reading comprehension deficits, the lesion correlates are brain areas known to be involved in linguistic tasks including sentence processing and speech articulation; the parietal lesion site may also correspond to a subpart of the human mirror neuron system. These results indicate that brain areas important for the production of language and action are also recruited in their comprehension. Similar findings have been reported in electrophysiological and neuroimaging studies. Our findings now also lend neuropsychological support to an embodied view of brain organization for action processing.

Anatomical organization of the telencephalic connections of the parafascicular nucleus in adult and developing rats

The parafascicular nucleus (PFN) of the rat, homologous to the human centre médian, is an intralaminar nucleus of the thalamus, classically considered as part of the ascending activating system. We have previously demonstrated that it is also connected to several subcortical nuclei. To obtain a more detailed picture of the connectivity of the PFN, the organization and the topography of the reciprocal parafascicular-telencephalic relationships were studied in both adult and developing rats, using anterograde and retrograde neuronal tracers. In the adult rat, the ascending parafascicular projections were densest to the striatum, dense to the frontal and least dense to cingulate cortex, and were strictly ipsilateral. They displayed a loose topography, with the more medial parafascicular neurons projecting to the medial frontal and cingulate cortex and medial striatum, and the more lateral neurons projecting to the lateral frontal cortex and lateral striatum. All these connections were already present at embryonic day 19. Parafascicular neurons projecting to the telencephalon in adult rats were mostly of the multipolar type, with a few bipolar neurons. In neonatal rats they showed a bipolar morphology at birth; they became mostly multipolar later on, with an increasing complexity of the dendritic arbor up to postnatal day 10. Neurons in the frontal cortex retrogradely labelled from the PFN were more numerous perinatally, and decreased as early as postnatal day 5. The telencephalic connections of the PFN were found to be more discrete and restricted than previously thought, thus suggesting a more specific functional role for the nucleus than cortical recruitment.

Gait apraxia after bilateral supplementary motor area lesion

OBJECTIVES

The study aimed at addressing the issue of the precise nature of gait apraxia and the cerebral dysfunction responsible for it.

METHODS

The case of a patient, affected by a bilateral infarction limited to a portion of the anterior cerebral artery territory is reported. The patient's ability to walk was formally assessed by means of a new standardised test.

RESULTS

Due to an anomaly within the anterior cerebral artery system, the patient's lesion was centred on the supplementary motor regions of both hemispheres. He presented with clear signs of gait apraxia that could not be accounted for by paresis or other neurological deficits. No signs of any other form of apraxia were detected.

CONCLUSIONS

The clinical profile of the patient and the analysis of 49 cases from previous literature suggest that gait apraxia should be considered a clinical entity in its own right and lesions to the supplementary motor areas are responsible for it.

Cognition in action: testing a model of limb apraxia

Assessment of limb apraxia is still suffering from Liepmann's legacy and performance in gesture-processing tests is generally rendered by classifying patients' profile according to the classic clinical labels of ideomotor and ideational apraxia. At odds with other cognitive functions, interpretation of apraxia has suffered from a lack of a reliable model which does justice to its complexity. Recently such a model has been proposed (Rothi et al., 1991, 1997). In this article a modified version of this model is presented and predictions are made according to its functional architecture. Five different patterns of impairment of gesture processing are postulated. To validate the predicted performance profiles, 19 left-hemisphere-damaged patients were assessed by means of an ad hoc battery of four praxis tests. Four of the five predicted apraxia patterns were observed, the fifth being more equivocal. These results support the need to overcome the simplistic dichotomous view of apraxia and confirm the fruitfulness of a model of normal gesture processing in order to understand dissociations in apraxia.

Visual feedback has differential effects on reaching movements in Parkinson's and Alzheimer's disease

We examine the role of visual feedback in the programming and execution of reaching movement in patients with Parkinson's disease without cognitive impairment and patients with Alzheimer's disease without extrapyramidal signs. Controls were normally aging subjects. All subjects moved a cursor to targets on a digitizing tablet without seeing their limb. Starting and target positions were always visible on a screen while, during movement, cursor position was either visible or blanked. They were instructed to make uncorrected movements, as fast and as accurate as possible without minimizing reaction time. In absence of visual feedback, movement accuracy in patients with AD was severely impaired. Hand paths of parkinsonian patients were as accurate as normal subjects' with similar temporal velocity profiles and movement speed. With cursor feedback, accuracy was the same in the three groups, although movement speed and transport phase in patients with Alzheimer's disease were significantly reduced compared to the other groups. Also, movements of parkinsonian patients showed shorter transport phase and lower mean velocity than controls'. The different characteristics of the motor performance suggests that in the two diseases visual information is used differently for both motor programming and execution: patients with Alzheimer's disease, while scarcely using feed forward commands, relied on continuous on-line external cues. The correlation of motor performance with cognitive impairment argues against the hypothesis of basal ganglia involvement in AD. The motor abnormalities we found may represent early subclinical manifestation of apraxic disturbance. Parkinsonian patients showed higher reliance on feedback commands only with cursor feedback: this could be explained by their difficulty in engaging effectively automatic routines when distractors are present.

Apraxia and cerebral haemorrhage: the relationship between haematoma volume and prognosis

In this study, we examined twenty-five patients with left putaminal haemorrhage to investigate the relations between ideational apraxia (IA) and intracerebral haemorrhage. Apraxias were determined at 1 and 6 months after the stroke onset. Extension and volume of haematoma were examined with CT scan within 2 days of stroke onset. IA was present in 10 cases at 1 month and disappeared in 6 cases (transient IA) and persisted in 4 cases(persisted IA) at 6 months from the onset. Although the haematoma volume related to the existence of IA, there was no significant difference between transient and persistent IA. All three patients with the haematoma volume larger than 40 ml in the transient IA group were younger than 50 years old. All cases with persistent IA were older than 50 years old. Consequently, the existence of IA seems to be partially dependent on the haematoma volume which may cause the organic damage of subcortical white matter. However, patient's age is also important to determine the prognosis of IA. This maybe related to the nature of the haemorrhage and the mode of the onset. These factors remain to be determined.

Assessment and intervention with clients with apraxia: contributions from the literature

Individuals with praxis problems encounter difficulties engaging in occupation, and the occupational therapists who work with these clients are challenged to provide intervention that enables occupational performance. This extensive review of the current literature provides clinicians with information regarding the relevant descriptions and suggested mechanisms of apraxia. Errors noted in performance, different classification systems and the implications of the current knowledge will be discussed. The paper concludes by providing information for clinicians regarding occupational therapy evaluation and intervention strategies for praxis problems.

Axial movements are relatively preserved with respect to limb movements in aphasic patients

Apraxia is commonly manifested during the acute stage following left hemisphere cerebrovascular accident and typically co-occurs with aphasia. We examined 30 acute stroke patients with aphasia and apraxia in order to determine if such patients show evidence of preservation of selective subclasses of movements. Although Geschwind noted the preservation of axial movements to command in aphasic apraxic patients, his views were subsequently refuted. However, we found that aphasic apraxic patients of varying degrees of severity, including patients with global aphasia, showed relative preservation of axial movements to command and imitation. Theoretical interpretations and implications for acute neurologic rehabilitation are discussed.

The left hemisphere and the selection of learned actions

The left hemisphere's dominance for movement is well known. The basis of its dominance is less clear. We have tested 16 left hemisphere (LH) patients, 17 right hemisphere (RH) patients and 12 neurologically normal controls on a battery of five tasks. The tasks were based on animal lesion and recording studies, and human imaging and magnetic stimulation studies that identified two distributed systems that are important for the selection of motor responses and object-oriented responses. The LH patients were impaired on three response selection tasks: learning to select between joystick movement responses instructed by visual cues; learning to select between analogous object-oriented responses instructed by visual cues; learning to select movements in a sequence. Although we replicated the finding that LH damage impairs sequencing, some of the impaired tasks had no sequencing element. We therefore argue that the LH deficits are best explained as an impairment of response selection. This was confirmed by showing that LH subjects were unimpaired on a more demanding task-object discrimination learning-which imposed a greater memory load but had no response selection element. Moreover, the LH deficits could not be attributed to disorganization of movement kinematics. The lesions of the impaired LH group were widespread but always included the distributed systems known to be important for response selection-the dorsolateral frontal and parietal cortices, striatum, thalamus and white matter fascicles.

Unilateral lenticular infarcts: radiological and clinical syndromes, aetiology, and prognosis

OBJECTIVES

To analyse the clinical features induced by lenticular infarction found in 20 patients, and to analyse the radiological and clinical correlations.

METHODS

Eight women and 12 men, mean age 73 years, were included in this study, which was carried out from 1 January 1994 to 30 November 1996. They were characterised by the onset of a lenticular infarction, shown by CT and MRI. A complete neurological and neurocognitive examination, and photon emission computed tomography (SPECT), were performed in all the patients and there was a long clinical follow up.

RESULTS

Two distinct clinical syndromes were identified corresponding to the two anatomical areas of the lenticular nucleus: behavioural and cognitive disorders were associated with infarcts within the globus pallidus, whereas both motor disorders (dystonia) and cognitive disorders were associated with infarcts within the putamen. Outcome was excellent in all the patients for motor function, but slight cognitive disorders, problems with short term memory, and dysphasia persisted for several months. The size of the lesion did not explain these symptoms. By contrast, the slight reduction in cerebral blood flow found in the adjacent frontotemporal area may explain them by a deafferentation or a diaschisis phenomenon.

CONCLUSION

It is possible to identify the clinical symptoms of a single lesion in the pallidus nucleus and in the putaminal nucleus, in which behavioural, cognitive, and movements disorders are important. After an acute and spectacular onset, outcome is in general excellent. A disease of the small arteries must be involved.

On crossed apraxia. Description of a right-handed apraxic patient with right supplementary motor area damage

GP, a right-handed woman, without evidence of familial left-handedness, showed clearcut bilateral ideo-motor apraxia and oro-facial apraxia after a vascular lesion of the right hemisphere, encroaching upon the fronto-mesial region. She scored normally in most other cognitive tests, including language, but showed signs of callosal disconnection, left anarchic hand and mild unilateral spatial neglect. This cognitive profile points to the possibility of praxis being localized to the right hemisphere in this right-handed patient. We argue in favour of individual variability of praxis dominance, and maintain that this dominance might be completely right-sided in some subjects. Moreover the anatomical locus of GP's lesion points to the possible role that the frontal lobes (and more specifically the Supplementary Motor Area) play in the genesis of apraxia.

Ideomotor apraxia: behavioral dimensions and neuroanatomical basis

Ideomotor apraxia, disordered movement execution to command, commonly follows left-hemisphere damage, implying left-hemisphere dominance for certain kinds of movements. To delineate this dominance we used different command modalities to elicit meaningful movements and tested imitation of nonsense movements. Twenty-seven patients with unilateral hemispheric stroke and 10 age-matched controls were evaluated. Patients with left-hemisphere damage performed both meaningful and nonsense movements poorer than the other study groups; thus, the meaningfulness of the movements is irrelevant for the left-hemisphere motor dominance. The performance varied, however, with the command modality and movement type. Based on this and earlier studies we posit that the left-hemisphere motor dominance is determined by the artificiality of the test situation (it concerns movements performed to command and out of the natural context) and increased spatial and temporal complexity of the demanded movements. No association between the lesion locus within the left hemisphere and the severity of the ideomotor apraxia was found.

A kinematic study of the reach to grasp movement in a subject with hemiParkinson's disease

The kinematic organization of a reach to grasp movement in a left hemiParkinson subject is compared to that of a control subject. Subjects used the right and left limbs to reach 15, 27 or 40 cm for the grasp of cylinders of 0.7 or 8 cm diameter. In general, the kinematics of the affected limb of the hemiParkinson subject differed from that of the unaffected limb. However, for both arms the hemiParkinson subject showed a delay in the onset of the manipulation component. The subtle dysfunction in the activation of near-simultaneous or sequential movements is thus bilateral, despite unilateral clinical symptomatology.

Ideomotor apraxia without aphasia and aphasia without apraxia: the anatomical support for a double dissociation

This study aimed to verify the existence of a double aphasia/apraxia dissociation. Apraxic patients without aphasia and aphasic patients without apraxia were included in a consecutive series of patients with cortical or subcortical CT documented vascular lesions in the left hemisphere. Of 699 patients, 10 were found to be apraxic but not aphasic and 149 aphasic but not apraxic. These findings indicate an aphasia/apraxia double dissociation. This suggests that praxis and language make use of two different, partly overlapping networks.

Parkinsonism and defects of praxis following methanol poisoning

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The biasing of weight judgments in Alzheimer's and Huntington's disease: a priming or programming phenomenon

The performances of Huntington's disease (HD) patients and patients with dementia of the Alzheimer type (DAT) were compared on an adaptation-level task involving the judgment of weights. In this task, subjects were first exposed to either a relatively heavy (heavy bias) or a relatively light (light bias) set of weights, and were later asked to rate the heaviness of a standard set of 10 weights using a 9-point scale. Patients with DAT and intact control subjects both perceived the standard set of weights as heavier following the light bias trials and lighter following the heavy bias trials, despite the DAT patients' poor explicit memory for the initial biasing session. In contrast, the weight judgments of the HD group as a whole was not significantly influenced by prior exposure to relatively heavy or light weights, and the size of the bias effect for this group was significantly correlated with the severity of their dementia. It is suggested that the impaired biasing performance of the HD patients, like their previously demonstrated impairment in motor skill learning, is due to a motor programming deficit resulting from neostriatal dysfunction.

Apraxia in a patient with lesion located in right sub-cortical area. Analysis of errors

This report describes a case of apraxia caused by a right sided sub-cortical lesion. Performance on test for apraxia was impaired. A new type of error which involved demonstrating the use of objects on one's own body is reported. Some theoretical interpretations of the findings are discussed.

Neuropsychological identification of motor problems: can we learn something from the feet and legs that hands and arms will not tell us?

The degree of structural and functional specialization that differentiates between upper and lower limb use in humans is quite unparalleled among primates. It is argued that less neural resources are devoted to leg and foot control than to arm and hand control, and that this aspect of lower limb innervation, together with the uniquely restricted use of the lower limb, renders lower limb function more sensitive to general neural insult. In addition, the status of leg and foot control differs from that of arm and hand control both early in life and during the later years of decline.

Aphasia and apraxia caused by ischemic damage to the white substance of the dominant hemisphere

We describe a case of aphasia associated with ideomotor apraxia due to a CT-proven ischemic lesion strictly confined to the dominant hemisphere white substance at the junctional zone of Donnan. The aphasia did not fit any of the known patterns. At first severe, it cleared in 5 days, while the apraxia remained unchanged 25 days after onset.

Crossed aphasia: functional studies with single photon emission computerized tomography

The correlation between clinical picture, CT scan and regional cerebral blood flow (rCBF) assessed by single photon emission computerized tomography (SPECT) was investigated in two patients with crossed aphasia. The presence and degree or right hemisphere dysfunction, beyond the areas affected by CT, closely paralleled the time course of language disturbances in both patients: transient aphasia in case 1 was associated with temporary reduction of perfusion in the right hemisphere, while in case 2 persistent aphasia and apraxia were found along with severe right hemisphere hypoperfusion three year after the onset of stroke.

Ideomotor apraxia: a study of initial severity

This study investigated whether there are predictors for initial severity of ideomotor apraxia (IMA) in focal left-hemisphere vascular patients. One hundred and twenty-nine subjects were examined between 15 and 30 days post-onset. Twenty-five patients with bilateral lesions were also studied in order to delineate the role of the right hemisphere. Other neuropsychological variables (i.e., token test, progressive matrices and oral apraxia scores) and size of the lesion were included in the experimental design. The main results were that a) token test, progressive matrices, oral apraxia scores, and lesion size correlate significantly with IMA, and b) that the presence of a second lesion in the right hemisphere is not found to have any significant effect on initial severity of IMA.