Emotional and Physiological Responses to False Feedback

The effect of unilateral brain lesions on perception of visual illusions

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.

In this study, we examine whether corrections made during an ongoing movement are differentially affected by left hemisphere damage (LHD) and right hemisphere damage (RHD). Our hypothesis of motor lateralization proposes that control mechanisms specialized to the right hemisphere rely largely on online processes, while the left hemisphere primarily utilizes predictive mechanisms to specify optimal coordination patterns. We therefore predict that RHD, but not LHD, should impair online correction when task goals are unexpectedly changed. Fourteen stroke subjects (7 LHD, 7 RHD) and 14 healthy controls reached to 1 of the 3 targets that unexpectedly "jumped" during movement onset. RHD subjects showed a considerable delay in initiating the corrective response relative to controls and LHD subjects. However, both stroke groups made large final position errors on the target jump trials. Position deficits following LHD were associated with poor intersegmental coordination, while RHD subjects had difficulty terminating their movements appropriately. These findings confirm that RHD, but not LHD, produces a deficit in the timing of online corrections and also indicate that both stroke groups show position deficits that are related to the specialization of their damaged hemisphere. Further research is needed to identify specific neural circuits within each hemisphere critical for these processes.

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.

There is growing evidence that the side of brain lesions results in distinct upper extremity deficits in motor control, movement behavior, and emotional and cognitive function poststroke. We investigated self-evaluation errors, which are the differences in scores between patient self-evaluation and clinician evaluations, and compared patients with left hemisphere damage (LHD) and right hemisphere damage (RHD) poststroke. Twenty-eight patients with chronic stroke (LHD = 16) performed the actual amount of the test twice with a one-week interval. We videotaped the participants' movements, and participants with stroke and evaluators graded the quality of movement scores by watching video recordings. Self-evaluation errors were significantly lower in patients with LHD than in those with RHD (t = 2.350, p = .019). Interestingly, this error did not change after the clinician provided the correct score as feedback. Chi-squared analysis revealed that more patients with LHD underestimated their movements (χ2 = 9.049, p = .002), while more patients with RHD overestimated (χ2 = 7.429, p = .006) in the send evaluation. Furthermore, there were no correlations between self-evaluation error and age, cognitive function, physical impairment, ability to control emotions, or onset months poststroke. Patients with stroke and therapists evaluated the same movements differently, and this can be dependent on hemispheric damage. Therapists might need to encourage patients with LHD who underestimate their movement to ensure continuous use of their more-affected arm. Patients with RHD who overestimate their movement might need treatment to overcome impaired self-awareness, such as video recordings, to protect from unexpected dangerous situations.

This study investigated the nature of semantic attribute knowledge in subjects with left and right hemisphere brain damage and subjects with no brain damage. The relationship between attribute knowledge and both auditory comprehension level and naming skills was also studied. Subjects completed a sorting task involving high, mid, and low frequency of occurrence nouns and high (HI) and low importance (LI) attributes. Subjects also named pictures of the stimulus nouns. While the identification of HI attributes remained intact, left and right hemisphere-damaged subjects exhibited equivalent reductions in identification of LI attributes across frequency levels. In contrast, the left hemisphere-damaged subjects were significantly more impaired on comprehension and naming measures than were the right hemisphere-damaged subjects. Comprehension and naming performance demonstrated a systematic relationship with attribute knowledge in the left hemisphere-damaged subjects only.

Testing comprehension abilities in users of British Sign Language following CVA

Ape signing and linguistic realism: A reply to Fodor

Hemispatial neglect is commonly observed in adults following right-hemisphere brain lesions. Given the potential for reorganization in the developing brain, spatial neglect may not be apparent following early unilateral damage. This study aimed to determine whether infants who experienced pre- or perinatal focal brain lesions showed evidence of spatial neglect. Study participants were 33 infants/toddlers (22 males, 11 females; age range 6 to 48 months); 27 preschool children (14 males, 13 females; age range 28 to 75 months) with either left hemisphere (LH) or right hemisphere (RH) damage of pre- or perinatal onset (total 60), and 36 control individuals (15 females, 21 males; age range 28 to 75 months). Participants were assessed using two object-removal preference tasks. Control children showed no lateralized preference for object removal. Those with LH or RH damage preferentially removed objects from the side of the board ipsilateral to the lesion first and the contralateral side last. These results suggest that spatial neglect may be found in young children even after very early unilateral brain damage. Further, in contrast to the adult pattern, contralateral neglect is present for up to 6 years after either LH or RH damage. This pattern suggests that there may be a different distribution of attention to space in the developing brain as compared with the mature brain. The persistence of spatial neglect suggests that there are some limitations on plasticity in the developing human brain.

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.

We compared the performance in a picture-name matching task of 10 patients suffering from left cerebral hemisphere (LH) damage and 10 from right hemisphere (RH) damage. The tasks showed detailed figures of nonrigid objects (animals) and rigid objects (artefacts), and each object was shown in two separate views: a noncanonical view (an unusual perspective for rigid objects or a contorted pose for the nonrigid ones) and a canonical view (a typical perspective and pose). Patients with LH damage were specifically impaired in identifying noncanonical (contorted) poses of nonrigid objects (animals). In a second picture-name matching experiment, using the divided visual field technique, normal subjects matched names to images of nonrigid shapes (animals) shown in canonical and noncanonical perspectives of noncontorted, typical poses of the animals. It was found that the normal subjects' RH identified these perspectives better than their LH. We conclude that computationally different problems are solved by different cerebral mechanisms when identifying flexible objects and when identifying rigid objects. We propose the idea that identifying flexible objects when their shapes contort relies on accessing stored descriptions of objects' parts and their “categorical” spatial relations and that both types of information are encoded better by the LH. In contrast, we propose that the RH is more adept at identifying different perspectives of rigid objects (and flexible objects when their shapes do not contort) because of this hemisphere's superiority in encoding specific global shapes and their views, and in coordinate spatial transformation.

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.

ABSTRACTPurposeThe aim of this study is to analyze and compare the performance and strategies used by control subjects and patients with unilateral brain damage on phonemic and semantic Verbal Fluency tasks.MethodsThe sample consisted of 104 participants divided into four groups (26 with left hemisphere damage and aphasia- LHDa, 28 with left hemisphere damage and no aphasia- LHDna, 25 with right hemisphere damage- RHD and 25 neurologically healthy control subjects). All participants were administered the phonemic (“M” letter-based) and semantic (animals) verbal fluency tasks from the Montreal-Toulouse Language Assessment Battery (MTL-BR).ResultsPatients in the LHDa group showed the worst performance (fewer words produced, fewer clusters and switches) in both types of fluency task. RHD group showed fewer switching productions when compared with controls and LHDna had fewer words productions than controls in the first 30 seconds block.ConclusionOur findings suggest that the LHDa group obtained lower scores in most measures of SVF and PVF when compared to the other groups.

The effects of congenital, unilateral, focal brain lesions on early linguistic development and hemispheric lateralization for language were investigated longitudinally in 24 preschool children with hemiplegia (14 males, 10 females), 12 with left hemisphere damage (LHD) and 12 with right hemisphere damage (RHD). A comprehensive linguistic assessment was performed at 2 and 3 years of life; cerebral lateralization for language was measured by the Fused Dichotic Words Listening Test. An early left-side specificity for language was indicated by the presence of lexical and grammatical delay in most children with LHD. In the dichotic listening test all 12 children with LHD showed a shift of language lateralization from the left to the right hemisphere. Atypical lateralization coefficients (lambda), i.e. values falling more than two standard deviations from the mean of a normative sample, were associated with a delay in lexical and grammatical development, especially after LHD. In addition, cortical-subcortical-periventricular lesions rather than solely periventricular damage, and larger lesions rather than small, were associated with the most atypical lateralization coefficients, irrespective of lesion side. Results of this study suggest that language and lateralization data are closely related and that reallocation of language functions in alternative regions of the brain has a cost in terms of a slow rate of language acquisition.

Decision strategies in neuropsychology I: Determination of lateralized cerebral dysfunction