Crossed Apraxia: Implications for Handedness

51 children with localized cerebral lesions were investigated with the British Ability Scales, Wechsler test, Porteus Mazes, Conners Teacher Rating Scale, and computerized tomography. The extent of the lesions was quantitatively determined. The IQ was 10 points lower in the left hemispheric lesions, although the right hemispheric lesions were larger. When corrected for size of lesions, the IQ is 17 points higher (p less than 0.05) in children with right than with left hemispheric early lesions. The children with left hemispheric lesions had also significantly more behavioural problems (Conners Scale). Children with bilateral lesions had 15 points lower IQ than those with unilateral lesions, although from the slightly larger extent one could expect only 3 points difference. There was no influence of hemiparesis or of epilepsy of the IQ independent of the extent of lesion. There was more plasticity of the hemisphere than of the lobes as shown by Wisconsin Card Sorting data. The higher density of mental capacities in the left cerebral hemisphere of man is explained by more efficient programs, and more dense packing of functions due to more training of the left cerebral hemisphere.

There are a number of studies concerning difference of postural control following left or right hemisphere lesions. Few studies, however, compare the role of the right and left hemisphere in learning new postural tasks. This study aimed to address this question. Twenty patients with hemiparesis after ischemic stroke in the middle cerebral artery territory (11 with a right and 9 with a left hemispheric lesion) were investigated. All subjects were trained using two different tasks during ten training sessions. In both tasks, the subjects stood on a force platform and were taught to change the position of the center of pressure (COP) presented as a cursor on a monitor screen in front of the patient. The subjects were instructed to align the COP with the target and then move the target by shifting the COP in the indicated direction. In the "Balls" task, the position of the target (a ball) varied randomly, so the subject had to learn a general strategy of voluntary COP control. In "Bricks", the subject always had to move the target in a single direction (downward) from the top to the bottom of the screen, so that a precise postural coordination had to be learned. The number of correctly performed trials for a session was scored. The task performance and its rate were analyzed and compared with respect to the lesion lateralization between two patient groups. The voluntary control of the COP position and learning course were initially impaired in all groups of patients in both tasks. In "Balls", there were no differences between the two groups of patients. In contrast, in "Bricks", there was a greater initial deficit in patients with right hemisphere lesions, while the rate of postural learning and the final performance level did not differ between the groups. With a lower initial deficit and similar rate of learning, the maximal level of the task performance was reached earlier (on the 5th day of training) in patients with left hemisphere lesions. This group stopped improving its performance during follow-up training. The results suggest that the motor structures of the right hemisphere are more involved in the precise control of COP trajectory, but not in learning. There is no difference between hemispheres in the initial performance and learning of the general strategy of voluntary COP control. Possibly, the control of specific COP trajectory needs more sensory feedback that is associated with greater involvement of the right hemisphere. This might be a reason for the greater initial impairment of this task after lesions in the right hemisphere.

We investigated how changes in the writing of 14 Korean stroke patients reflect the unique features of the Korean writing system. The Korean writing system, Han-geul, has both linguistic and visuospatial/constructive characteristics. In the visuospatial construction of a syllable, the component consonant(s) and vowel(s) must be arranged from top-to-bottom and/or left-to-right within the form of a square. This syllabic organization, unique to Korean writing, may distinguish dysgraphia in Korean patients from the disorder in other languages, and reveal the effects of stroke on visuospatial/constructive abilities. We compared 2 groups of patients affected by stroke, 1 group with left hemisphere (LH) lesions and the other with right hemisphere (RH) lesions. We instructed them to write from a dictation of 90 monosyllabic stimuli, each presented with a real word cue. Patients had to repeat a target syllable and a word cue, and then to write the target syllable only. Patients with LH and RH lesions produced qualitatively different error patterns. While the LH lesion group produced primarily linguistic errors, visuospatial/constructive errors predominated in the group with RH lesions. With regard to language-specific features, these Korean patients with RH lesions produced diverse visuospatial/constructive errors not commonly observed in dysgraphia of the English language. Language-specific writing errors by Korean stroke patients reflect the unique characteristics of Korean writing, which include the arrangement of strokes and graphemes within a square syllabic form by dimensional and spatial rules. These findings support the notion that the Korean writing system possesses a language-specific nature with both linguistic and visuospatial/constructive processes. Distinctive patterns of dysgraphia in the Korean language also suggest interactivity between linguistic and visuospatial/constructive levels of processing. This study is noteworthy for its systematic description of Korean dysgraphia in the largest group of patients studied to date.

Praxis is defined as skilled, purposive limb movement. While it has been a consistent finding that lesions of the left cerebral hemisphere result in significantly worse performance on praxis testing than lesions of the right cerebral hemisphere, recently some investigators have proposed that the right hemisphere may also play an important role in mediating praxis. To learn if the right hemisphere does have a role in praxis we studied right-handed patients with right or left hemisphere lesions, as well as right-handed normal controls who were matched for age and education. Two trained raters scored the transitive gesture performance of the forelimb ipsilateral to the injured hemisphere. For the normal controls, left and right hand performances were scored separately and used for statistical comparison. Independent comparisons were made on six dimensions that are important for accurate gesture performance and on an overall apraxia score. When compared to normal control subjects the patients with left hemisphere lesions (LHD) did demonstrate deficient praxis; that is, ideomotor apraxia. However, those with right hemisphere lesions (RHD) did not. Based on this study it would appear that the right hemisphere does not play a crucial role in praxis.

In adults apraxia is more common after left-hemisphere damage. The engram for control of skilled motor movements has therefore been considered a specialized function of the left hemisphere. The ontogenesis of motor control was studied in a group of prepubertal children with congenital unilateral hemispheric lesions. Left-hemisphere lesions caused greater impairment of rapid independent finger movements, suggesting that specialization for motor control is innately programmed in the left hemisphere. No subject evidenced apraxia to verbal command, but adult-like performance is not yet expected at the age the group was tested, and effects of side of lesion could appear later.

Unilateral left and right hemisphere lesions produce numerous well documented neuropsychological consequences (DeRenzi, 1982). Some of these sequelae are attentional, involving anatomical systems related to the selection of information for conscious detection (Nissen, 1986; Posner & Rafal, 1986). Such attentional deficits can often be demonstrated in tasks involving conflicts between stimuli (Posner & Presti, 1987). For example, patients with left hemisphere lesions have difficulty selecting a verbal input when it conflicts with a simultaneous spatial command. Patients with right hemisphere damage show the reverse pattern (Walker, Friedrich, & Posner, 1983). Similarly, patients with parietal lobe lesions often have great difficulty when an event in the contralesional visual field is in conflict with one in the ipsilesional field. In severe cases these patients may be completely unaware of contralesional targets while in milder cases the target may be detected but with longer latency (DeRenzi, 1982; Posner, Walker, Friedrich & Rafal, 1984).

Literature shows that subjects with right brain damage present inference difficulties. However, more recent neuroimaging research demonstrates coactivation of hemispheres during inferential processing in healthy individuals. Comparative studies on the effects of right-and left-hemisphere lesions on tasks of reading comprehension of inferences are scarce. The objectives of this study were: (1) To compare the performance of patients with left hemisphere lesion (LHL), right hemisphere lesion (RHL) and healthy subjects in a task of reading comprehension of inferences; (2) To analyze the correlation between cognitive functions and performance on this inference comprehension test; and (3) To analyze the influence of age, education and local of lesion on the same task. METHODS: The sample consisted of 75 subjects divided into three groups: 25 subjects with LHL, 25 subjects with RHL and 25 control subjects (CG). Individuals were assessed using the "Implicit Management" test, designed to evaluate comprehension of inferences during reading. The test consists of 20 small texts, demonstrating a scenario of a fact or a problem situation. Patients answered questions that demand different types of inferential reasoning: explicit (not requiring inferential reasoning per se), logical (requiring logical reasoning and deduction processes), pragmatic (requiring inductions from common knowledge and contextualization), distracting (the requested information is not contained in the text) and "other" (requiring concomitant management of logical and pragmatic operations). The Cognitive Linguistic Quick Test (CLQT) was used for cognitive evaluation and correlation with the inference comprehension test. The CLQT assesses the domains of attention, memory, executive functions, language, and visuospatial abilities. RESULTS: Regarding performance in the inference comprehension test, the three groups differed in the logical, pragmatic, "other" questions, and in the total scores. The RHL group performed worse than the LHL group, and both had worse scores than the CG. The RHL and LHL groups did not differ in explicit and distracting questions, but they had lower performances when compared to the CG. In the overall analysis of the sample, all cognitive domains of the CLQT were related to all types of questions in the inference comprehension test, especially logical, pragmatic, "other" questions, and total score. In the group analysis, in the LHD group, memory was correlated with performance in logical questions; attention, memory, executive functions and visuospatial skills were correlated with performance in "other" questions. In the LHE group, attention and visuospatial skills were more related to pragmatic questions. Only education influenced the performance of the sample as a whole. CONCLUSIONS:

Objective To develop and standardize the Limb and Oral Apraxia Test (LOAT) for Korean patients and investigate its reliability, validity, and clinical usefulness for patients with stroke.MethodsWe developed the LOAT according to a cognitive neuropsychological model of limb and oral praxis. The test included meaningless, intransitive, transitive, and oral praxis composed of 72 items (56 items on limb praxis and 16 items on oral praxis; maximum score 216). We standardized the LOAT in a nationwide sample of 324 healthy adults. Intra-rater and inter-rater reliability and concurrent validity tests were performed in patients with stroke. We prospectively applied the LOAT in 80 patients and analyzed the incidence of apraxia. We also compared the clinical characteristics between the apraxia and non-apraxia groups.ResultsThe internal consistency was high (Cronbach’s alpha=0.952). The inter-rater and intra-rater reliability and concurrent validity were also high (r=0.924–0.992, 0.961–0.999, and 0.830, respectively; p<0.001). The mean total, limb, and oral scores were not significantly different according to age and education (p>0.05). Among the 80 patients with stroke, 19 (23.8%) had limb apraxia and 21 (26.3%) had oral apraxia. Left hemispheric lesions and aphasia were significantly more frequently observed in the limb/oral apraxia group than in the non-apraxia group (p<0.001).ConclusionThe LOAT is a newly developed comprehensive test for limb and oral apraxia for Korean patients with stroke. It has high internal consistency, reliability, and validity and is a useful apraxia test for patients with stroke.

Treatment of Psychiatric Symptoms Associated With a Frontal Lobe Tumor Through Surgical Resection

Scholastic aptitude and achievement among children with unilateral brain lesions

Attention impairments are frequent in stroke patients with important consequences on the rehabilitation outcomes and quality of life. The aim of the study was to perform a comprehensive assessment of selective and intensive attention processes in a large population of brain-damaged patients, evaluating the influence of the side and site of the brain lesion, the time from stroke, and the concomitant presence of aphasia or neglect. We assessed 204 patients with a first unilateral brain lesion and 42 healthy individuals with three subtests of the Test of Attentional Performance (TAP): Alertness, Go-No Go, and Divided Attention. 44.4% of patients had an impairment in both intensive and selective aspects of attention, 5.6% had deficits only in the intensive component, and 31.8% had deficits only in selective tasks. More than 80% of the patients fell below the cut-off point on at least one task. Patients with a right hemispheric lesion (RHL) were more impaired than patients with a left hemispheric lesion (LHL) especially in tonic and phasic alertness. Patients with total anterior infarcts (TACI) presented the worst profile compared to other stroke subtypes, with a difference between total and lacunar subtypes in the Alertness test, independent of the presence of warning. Patients in the chronic phase had shorter RTs than acute patients only in the Alertness test. In patients with LHL, the presence of aphasia was associated with a greater deficit in selective attention. In patients with RHL, the presence of unilateral neglect was associated with impaired alertness and selective attention. Attention deficits are common after a unilateral first stroke. In keeping with the hierarchical organization of attention functions, results confirm the important role of the right hemisphere for the intensive components of attention, also highlighting the involvement of left hemisphere functioning for the selective aspects, possibly indicating a role of its linguistic functions.

Temporal Sequencing of Verbal and Nonverbal Materials: The Effect of Laterality of Lesion

Understanding ‘not’: neuropsychological dissociations between hand and head markers of negation in BSL

The Role of the Left Hemisphere in Verbal and Spatial Reasoning Tasks

Quantitative EEG abnormalities in major depressive disorder with basal ganglia stroke with lesions in different hemispheres