The different types of limb apraxia errors made by patients with left vs. right hemisphere damage

Analysis of task demands in apraxia

Several task demands were examined in a battery of praxis tests: the movement system (limb versus axial), input modality (command versus imitation), movement complexity (single gestures versus a sequence of gestures), type of limb gesture (transitive versus intransitive), and the representational nature of the gestures. Performance accuracy for a group of left hemisphere patients was significantly lower than for two other groups of patients with either right hemisphere damage or no brain damage on all gestures. The right hemisphere patients were significantly different from the normals only for the most complex gestures involving a three movement sequence. Within the left hemisphere group performance to command was not different from imitation. Representational and nonrepresentational gestures were not different, and axial gestures was not different from the limb gestures. The transitive and complex gestures were not different but were both performed less accurately than the intransitive gestures. The implications of these findings for understanding apraxia were discussed.

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 evaluation and rehabilitation in mental retardation

A discussion is provided of issues related to neuropsychological assessment of mentally retarded individuals. The first matters considered are test selection in relation to mental age and diagnostic issues. Various methods of evaluation are then considered, including assessment of orientation to sound and visual stimuli, language comprehension, right-left discrimination, and abstract and symbolic processes. Methods are also reviewed for detailed evaluation of language functions including testing for aphasia and for academic skills such as reading, writing, and calculation, as well as for spatial and constructional abilities. A section is devoted to use of neuropsychological assessment for rehabilitation of various disorders such as congenital aphasia, alexia, and spatial-constructional disorders.

The role of the hemispheres in closed loop movements

The purpose of these experiments was to determine if the two hemispheres play different roles in controlling closed loop movements. Subjects were asked to move to a narrow or wide target in the left or right hemispace. Reaction time (RT) was faster for the left arm of normals, only in the right hemispace, but there were no differences between arms in movement execution. Right but not left hemisphere stroke (CVA) patients showed longer RTs for the contralateral but not ipsilateral arm. The right CVA group's ipsilateral movement, especially to narrow targets was less accurate. The left CVA group's RT did not benefit from advanced information, but ipsilateral movement execution was normal. These results were discussed in terms of inter- as well as intrahemispheric control of programming and execution of closed loop movements.

Ideational apraxia: a deficit in tool selection and use

We report a 67-year-old left-handed man who exhibited an ideational apraxia in both clinical and nonclinical natural settings following a right hemisphere infarction. His inability to use tools could not be explained by a motor production deficit (ideomotor apraxia), because he made content errors and could not match tools with objects. His deficit could not be attributed to an agnosia or language comprehension deficit, because he could name tools and point to tools on command. Based on our testing, it appeared that this patient had a loss of knowledge related to tool use.

Hemispheric control of the initial and corrective components of aiming movements

This study examined whether the left and right hemispheres play differential roles in controlling the initial and corrective components of aiming movements. A simple aiming task was administered to 31 normal control subjects and 29 unilateral stroke patients (14 with right hemisphere damage and 15 with left hemisphere damage). Movement amplitude was varied (25, 64 and 100 mm) and reaction time, movement time and accuracy were measured. Through a trajectory analysis, initial and corrective movements were separated. The stroke patients performed the task with their ipsilateral arm which was compared to the normal controls' right or left are performance. Regardless of the movement amplitude the left hemisphere group's reaction time was slower, and the execution of the initial movement component was less accurate than controls. No performance deficits were found on corrective movements. Performance was not impaired for the right hemisphere group on any measures. These results are discussed in terms of the hemispheres' possible roles in controlling movements which are largely open or closed loop.

Pantomimes and aging

The goal of this study was to verify the evolution of pantomiming in normal aged subjects in comparison to normal younger adults. Ninety-six subjects participated in this study: 30 between the ages of 20 and 30; 30 between the ages of 40 and 50; and 36 between the ages of 60 and 82. The subjects were required to execute 42 pantomimes on verbal command. The executed gestures were divided into two categories and analyzed separately: (a) the static constituents which refer to the shape the subject gave to the body part(s) involved; and (b) the dynamic constituents which refer to the executed action and to the relations established between several static constituents during the execution. The results showed that the aged subjects' performance was different from the younger subjects' performance principally in the static constituents of self-oriented one-hand gestures where the aged subjects used a part of their body to serve as the absent object.

Apraxia in a patient with atypical cerebral dominance

Liepmann postulated that the left hemisphere of right-handed persons contains the "movement formulas" that control purposeful skilled movements of the limbs on both sides of the body. Accordingly, in right-handers apraxia should follow damage to the left hemisphere, whereas right hemisphere damage should not lead to apraxia. Although this is generally true, we recently examined a right-handed man who after a right hemispheric stroke became aphasic and apraxic with his nonparalyzed right hand. Our observations suggest that the right hemisphere of this right-handed man made a critical contribution to the planning and execution of skilled movements. This case provides evidence that right-handers should not be considered a homogeneous group in terms of cerebral motor dominance and that contrary to Liepmann's postulate, hemispheric dominance for the control of skilled movements does not entirely determine handedness.

The effects of task complexity on motor performance in left and right CVA patients

The effects of task complexity on movement ipsilateral to lesion were examined using the Fitts tapping task [Fitts, P.M., J. exp. Psychol. 47, 381-391, 1954]. Subjects were required to rapidly tap two targets, which were 1 or 4 cm wide. Twenty controls and ten left hemisphere and nine right hemisphere stroke patients were studied. Only the left hemisphere group showed significant deficits with greater impairment found in the wide target condition. Quantified CT scan analyses indicated lesion volume was similar between CVA groups, but the left hemisphere group's lesions were more anterior. The results are discussed in terms of inter- and intrahemispheric roles in open and closed loop movements.

Apraxia after a superior parietal lesion

We studied a patient who had unilateral (left) limb apraxia associated with a lesion of her right superior (Brodmann areas 5 and 7) and inferior parietal lobes. In monkeys areas 5 and 7 contain "hand-manipulation neurons" that are thought to be important in proprioceptive guidance. Therefore, we tested our patient with her eyes open and closed. Her left hand performance with pantonime, imitation, and use of actual objects dramatically deteriorated in the absence of visual guidance. In addition, although the patient did not have optic ataxia and had normal proprioception, she had difficulty using her left forelimb in tasks that require transcoding from a visual to a somatesthetic spatial coordinate system. We propose that each superior parietal lobe is not only responsible for transcoding from a visual-spatial code into a somatesthetic-spatial code but is also critical for transcoding spatial-temporal representations of skilled movement into a somatesthetic-spatial code.

The clinical examination for motor apraxia

The signs and symptoms of motor apraxia are described both for ideomotor and ideational apraxia. Typical errors are described. For ideomotor apraxia a list of tasks is given. The many conceptual and psychometric problems that still await an answer are briefly discussed.