Lexical retrieval in left and right brain lesioned children

Performance on two measures of lexical retrieval for 19 left and 13 right brain lesioned children was compared to that of control subjects matched by age, sex, race, and social class. On the Word-Finding Test, left lesioned subjects were significantly slower in response time than left controls when given semantic and visual cues and made more errors when given rhyming cues. On the Rapid Automatized Naming Test, left lesioned subjects were significantly slower than left controls in naming all semantic categories, including colors, numbers, objects, and letters. In contrast, right lesioned subjects responded as quickly as or more quickly than did right controls in all access conditions and in naming semantic categories yet tended to produce more errors than their controls, suggesting a speed-accuracy tradeoff. Children sustaining left brain lesions before 1 year of age appeared to be as impaired as those whose lesions occurred after 1 year of age. Diverse lesion sites within the left hemisphere were associated with increased lexical retrieval latencies.     

Spoken syntax in children with acquired unilateral hemisphere lesions

The spoken syntax of eight left hemisphere lesioned and eight right hemisphere lesioned children were compared to matched controls. The children's lesions were acquired between 0.08 and 6.17 years of age (mean = 1.33 years), and at the time of testing they were between 1.67 and 8.15 years of age (mean = 4.19). Based on analyses of spontaneous language samples, left hemisphere lesioned subjects performed more poorly than did their controls on most measures of simple and complex sentence structure. In contrast right lesioned subjects performed similarly to their controls on these measures, except for a tendency to make more errors in simple sentence structures. These findings provide further evidence that the left and right hemispheres are not comparable in supporting syntactic abilities.     

Brain Organization of Language after Early Unilateral Lesion: A PET Study

Neuropsychological studies suggest that good long-term language outcome is possible following extensive early left-hemisphere damage. We explored the brain organization for language in children with early unilateral lesion, using [¹⁵O]-water PET. In 12 patients with left lesion (LL) and 9 patients with right lesion (RL), cerebral blood flow changes during listening to sentences and repetition were studied. A rightward shift of language activations in the LL group was found in perisylvian areas and multiple other, mostly temporo-parietal, regions. The hypothesis of intrahemispheric reorganization in the LL group found only limited support. The number of activated regions was overall greater in the RL group. Unexpected findings included a stronger subcortical and cerebellar language involvement in the RL group. We suggest that (a) early left lesion is associated with enhanced language participation of the right hemisphere in and beyond the classical language areas, and (b) postlesional effects are in part additive (recruitment of noncanonical areas), in part subtractive (functional depression in areas normally involved in language).     

Encouraging pointing with the right hand,but not the left hand,gives right-handed 3-year-olds a linguistic advantage

Previous research has shown a strong positive association between right-handed gesturing and vocabulary development. However, the causal nature of this relationship remains unclear. In the current study, we tested whether gesturing with the right hand enhances linguistic processing in the left hemisphere, which is contralateral to the right hand. We manipulated the gesture hand children used in pointing tasks to test whether it would affect their performance. In either a linguistic task (verb learning) or a non-linguistic control task (memory), 131 typically developing right-handed 3-year-olds were encouraged to use either their right hand or left hand to respond. While encouraging children to use a specific hand to indicate their responses had no effect on memory performance, encouraging children to use the right hand to respond, compared to the left hand, significantly improved their verb learning performance. This study is the first to show that manipulating the hand with which children are encouraged to gesture gives them a linguistic advantage. Language lateralization in healthy right-handed children typically involves a dominant left hemisphere. Producing right-handed gestures may therefore lead to increased activation in the left hemisphere which may, in turn, facilitate forming and accessing lexical representations. It is important to note that this study manipulated gesture handedness among right-handers and does therefore not support the practice of encouraging children to become right-handed in manual activities.

Research Highlights

• Right-handed 3-year-olds were instructed to point to indicate their answers exclusively with their right or left hand in either a memory or verb learning task.
• Right-handed pointing was associated with improved verb generalization performance, but not improved memory performance.
• Thus, gesturing with the right hand, compared to the left hand, gives right-handed 3-year-olds an advantage in a linguistic but not a non-linguistic task.
• Right-handed pointing might lead to increased activation in the left hemisphere and facilitate forming and accessing lexical representations.

     

Writing induces a right hemisphere linguistic advantage in dysphonetic dyslexic children: implications for attention and capacity models of laterality

An experiment demonstrated a complete hemispheric processing reversal in 10 male, dysphonetic dyslexic children that occurred during a dichotic listening test of their verbal working memory. Requiring a written response to dichotic digits produced a right hemisphere/left ear superiority in the dysphonetic dyslexics whereas normal subjects and other dyslexics maintained a left hemisphere/right ear advantage. This reversal was unaffected by changes in task difficulty. A second experiment assessed the influence on producing the reversal of concurrent manual interference with left hemisphere verbal processing (responding orally vs. manually) and selective right hemisphere priming (Forward Writing vs. Backward Writing). The dysphonetic children reverted to a strong left hemisphere superiority when recalling the dichotic digits orally. Backward writing produced no ear advantage in either direction. The findings suggest that dysphonetic dyslexia may be related to (1) left hemisphere processing demands that exceed capacity, (2) easily activated right hemisphere processing strategies and (3) failure to coordinate linguistic processing interhemispherically. The results supported a novel hybrid conceptualization of dyslexia consisting of a synthesis of selective activation, and dual processor-limited capacity, theories.     

Fluency of conversational speech in children with unilateral brain lesions

The spontaneous conversational speech of 20 children with unilateral left hemisphere lesions and 13 with right lesions was compared to normally developing peers matched by age, sex, race, and social class for instances of stuttering type nonfluencies, normal nonfluencies, and rate of speech. Both left and right lesioned children provided quantitatively more and qualitatively different patterns of nonfluencies than their neurologically normal peers. Left and right lesioned children produced more stuttering types of nonfluencies than their controls, but neither lesioned group produced a greater number of normal nonfluencies than controls. Left lesioned children also had a slower rate of speech as measured by number of syllables per second during either stuttered or fluent speech. Considerable variability was observed among lesioned children. Implications for neurogenic theories of developmental fluency disorders are discussed.     

Language development in a child with left hemispherectomy

A longitudinal study of a left hemispherectomized boy (AB) was conducted to document linguistic evolution and maturation and determine the extent to which right hemisphere processes allow development of language. Resection of the left hemisphere occurred at age 5 years 6 months, following intractable epilepsy. Tests of language comprehension (pointing, understanding of prepositions, understanding of narratives) and production (naming, repetition, lexical diversity, grammatical production) were administered at ages 6:2, 6:4, 6:6, and 6 years 9 months. Observations showed little progress, if any, in most aspects of linguistic performance. In contrast to studies with left-hemispherectomized children, AB showed only a modest expansion of the semantic lexicon and the phonological repertoire more than a year after the surgical intervention. These observations indirectly suggest (1) poor functional involvement of the right hemisphere in the development of adequate linguistic abilities, (2) the necessary integrity of the LH for adequate development of language, or (3) that variations in individual brain maturation rates may account for AB's linguistic progress.     

The WISC-V in children and adolescents with epilepsy

Despite its popularity in the neuropsychological evaluation of children, the utility of the Wechsler Intelligence Scale for Children – Fifth Edition (WISC-V) has not yet been investigated in children with epilepsy. Eighty clinically referred children and adolescents with epilepsy were administered the WISC-V as part of a comprehensive assessment and scores were compared to matched controls from the WISC-V standardization sample. T tests compared WISC-V indices and subtests between patients and controls and Chi-square analyses compared the rates of low scores. Correlational analyses assessed the relationships between epilepsy severity variables (e.g., age of onset, duration of epilepsy, number of antiepileptic drugs, seizure frequency). All WISC-V composites and subtests were significantly lower in patients versus controls and the rate of low scores was higher in patients than controls for all composites and subtests with the exception of Figure Weights. The Working Memory Index and Processing Speed Index were most sensitive to impairment, while the Verbal Comprehension Index and Fluid Reasoning Index were least sensitive. Of the epilepsy severity variables, age of seizure onset and number of antiepileptic drugs were strong predictors of deficits, whereas seizure frequency was the weakest predictor. Importantly, no significant differences were seen in children with right hemisphere epilepsy versus left on the five WISC-V composites, though a trend was seen towards a lower Visual-Spatial Index in those with right-sided focal seizures.     

Spatial analysis after perinatal stroke: patterns of neglect and exploration in extra-personal space

This study was conducted to determine whether school-aged children who had experienced a perinatal stroke demonstrate evidence of persistent spatial neglect, and if such neglect was specific to the visual domain or was more generalized. Two studies were carried out. In the first, 38 children with either left hemisphere (LH) or right hemisphere (RH) damage and 50 age-matched controls were given visual cancellation tasks varying in two factors: target stimuli and stimulus array. In the second study, tactile neglect was evaluated in 41 children with LH or RH damage and 72 age-matched controls using a blindfolded manual exploration task. On the visual cancellation task, LH subjects omitted more target stimuli on the right, but also on the left, compared with controls. Children with RH lesions also produced a larger number of omissions on both the left and right sides than controls, but with poorer performance on the left. On the manual exploration task, LH children required significantly longer times to locate the target on both sides of the board than did controls. RH children had significantly prolonged search times on the left side, but not on the right, compared with controls. In both tasks, LH subjects employed unsystematic search strategies more often than both control and RH children. The search strategy of RH children also tended to be erratic when compared to controls, but only in the random arrays of the visual cancellation tasks; structure of the target stimuli improved their organization. These results demonstrate that children with early LH brain damage display bilateral difficulties in visual and tactile modalities; a pattern that is in contrast to that seen in adults with LH damage. This may result from disorganized search strategies or other subtle spatial or attentional deficits. Results of performance of RH children suggests the presence of contralateral neglect in both the visual and tactile modalities; a finding that is similar to the neglect in adult stroke patients with RH lesions. The fact that deficits in spatial attention and organizational strategies are present after very early focal damage to either the LH or the RH broadens our understanding of the differences in functional lateralization between the immature and mature brain. These results also add to evidence for limitations to plasticity in the developing brain. Our findings may have therapeutic and rehabilitative implications for the management of children with early focal brain lesions.     

Auditory processing of brain-damaged adults under competitive listening conditions

Right CVAs, mild left CVAs, and non-brain-damaged adults received the Token Test under three conditions: quiet, white noise, and speech babble. Left CVAs performed most poorly of all groups in all conditions experiencing difficulty with subtests III, IV, and V. Right CVAs were inferior to controls on each of these three subtests in the speech babble condition only. Thus, right CVA difficulty with both memory and syntactic tasks was demonstrated in speech babble. These results are explained by the hypothesis that both hemispheres are necessary to process auditory information under complex listening conditions. Total brain capacity of right CVA patients may be overloaded if either memory load or linguistic complexity is increased in the presence of certain types of listening competition.     

Narrative comprehension in adults with right and left hemisphere brain-damage: theme organization.

The effects of delayed presentation of a central theme on the comprehension and interpretation of narratives were investigated in adults with right and left hemisphere brain-damage and normal individuals. The performance of subgroups of the subjects with right and left hemisphere brain-damage also was examined. Right hemisphere brain-damaged groups with anterior and posterior lesions were significantly less accurate and identified significantly fewer central themes when central theme presentation was delayed until the end of a narrative than when the theme was presented at the beginning. Subjects with anterior right hemisphere brain-damage produced significantly more embellishments and confabulations than subjects with posterior damage and non-brain-damaged controls, regardless of theme condition. The performance of non-brain-damaged subjects and subjects with fluent and nonfluent aphasia was unaffected by the organization of the central theme in the narratives.     

Deficits in temporal sequencing of verbal material: The effect of laterality of lesion

Temporal sequencing of verbal materials (digits, words, and geometric forms) presented in two sensory modalities (auditory and visual) to three groups of subjects (Broca's with left anterior lesions, patients with right hemisphere lesions, and normals) was examined. Each subject was asked to point to a set of stimuli in the same sequence as presented by the examiner. Results indicated that patients with left hemisphere lesions were more impaired on all tasks than the right hemisphere lesioned patients who, in turn, were impaired compared to normal controls. Response to auditory presentation was superior to response to visual presentation. Also, digits were the easiest for all groups, and words were easier than geometric forms. Of special interest was the finding which suggested that right hemisphere lesions are associated with impairment of verbal temporal sequencing under either auditory or visual presentation.     

The effects of right and left hemiparkinsonism on prosody

Recent studies show right hemisphere dominance in the mediation of emotional prosody and left hemisphere contribution to linguistic prosody in patients with cortical injury. The present study investigated emotional and linguistic functions of prosody as well as facial and musical processing in 21 patients with lateralized subcortical disease. Fourteen right hemiparkinsonians (RPD) and 7 left hemiparkinsonians (LPD) were compared to 17 normal controls (NC). Patients were impaired on receptive and expressive tests of emotional and linguistic prosody. Patients were also selectively impaired on emotional processing of facial stimuli and in the musical processing of pitch and tonal memory, though not timber. These findings suggest that monotone speech reported in PD is of multimodal origins and may involve dysfunction in neural centers involved in emotional and linguistic processing. There were no differences between RPD and LPD groups in the pattern of deficits, suggesting bilateral involvement in emotional processing at the subcortical level.     

Intelligence profiles in children and adolescents with left temporal lobe epilepsy: relationship to language laterality

Pre- and postoperative IQ profiles were examined in children and adolescents with left temporal-lobe epilepsy. Participants were grouped according to their pattern of speech dominance, as indicated by the intracarotid sodium amobarbital procedure. Seven participants with typical (left hemisphere) speech representation were matched for age and sex to seven participants with atypical (bilateral or right hemisphere) speech representation. The group with atypical speech representation tended to perform worse pre- and postoperatively on several verbal and nonverbal subtests. Unlike Strauss et al.'s (1990) sample, however, the groups did not differ significantly on pre- or postoperative Performance IQ. The results suggest that when individuals are matched closely for age and sex, there may only be limited support for a nonverbal "crowding" hypothesis. Atypical speech representation in children and adolescents with early temporal-lobe epilepsy appears to be associated with lowered performance on both verbal and nonverbal IQ subtests.     

记忆状态下儿童青少年脑波超慢涨落特点的研究

用ET技术对24名7—18岁的儿童青少年进行了静息状态和记忆状态下脑电超慢涨落特点的比较研究,结果表明,在记忆状态下：(1)被试S1、S2频率明显下降,记忆成绩好的被试这一特点更为明显;(2)男生左脑功率明显下降,女生右脑功率明显上升;(3)左脑优势被试左前脑功率下降,右脑优势被试右前脑功率上升。     

Are there different patterns of cerebral asymmetry between dyslexic subtypes?

The purpose of this research has been to analyze the cerebral asymmetry in dyslexic children and, specifically for demonstrating whether there are different patterns of cerebral asymmetry among subtypes of dyslexia. We used a sample of 89 dyslexic children divided into subtypes obtained from the Jimenez and Ramirez (2002) study. The dual-task method was used to assess hemispheric specialization. The data were compared with that obtained from a control group of normal readers of same age (CA; N= 37) and with a younger reading level control group (RL; N= 40). We found that in the dyslexic group, similarly to the younger reading level group, a high percentage of children showed convergence in the left hemisphere of both linguistic and spatial functions. This pattern was also found in the RL control group. On the other hand, we did not find different patterns of cerebral asymmetry between dyslexic subtypes.     

Linguistic and neuropsychological deficits in crossed conduction aphasia. Report of three cases

This study describes the linguistic and neuropsychological findings in three right-handed patients with crossed conduction aphasia. Despite the location of the lesion in the right hemisphere, all patients displayed a combination of linguistic deficits typically found in conduction aphasia following analogous damage to the left hemisphere. Associated cognitive deficits varied across the three patients. In addition, all cases showed deficits classically attributed to non-dominant hemisphere damage (visuoperceptual deficits and reduced figural memory). As a result, lesion-behaviour relationships in our study sample indicate both dominant and non-dominant qualities of the right hemisphere.     

Reorganization of the cerebro-cerebellar network of language production in patients with congenital left-hemispheric brain lesions

Patients with congenital lesions of the left cerebral hemisphere may reorganize language functions into the right hemisphere. In these patients, language production is represented homotopically to the left-hemispheric language areas. We studied cerebellar activation in five patients with congenital lesions of the left cerebral hemisphere to assess if the language network is reorganized completely in these patients, i.e. including also cerebellar language functions. As compared to a group of controls matched for age, sex, and verbal IQ, the patients recruited an area not in the right but in the left cerebellar hemisphere. The extent of laterality of the cerebellar activation correlated significantly with the laterality of the frontal activation. We suggest that the developing brain reacts to early focal lesions in the left hemisphere with a mirror-image organization of the entire cerebro-cerebellar network engaged in speech production.     

Processing of basic speech acts following localized brain damage: a new light on the neuroanatomy of language

We examined the effect of localized brain lesions on processing of the basic speech acts (BSAs) of question, assertion, request, and command. Both left and right cerebral damage produced significant deficits relative to normal controls, and left brain damaged patients performed worse than patients with right-sided lesions. This finding argues against the common conjecture that the right hemisphere of most right-handers plays a dominant role in natural language pragmatics. In right-hemisphere damaged patients, there was no correlation between location and extent of lesion in perisylvian cortex and performance on BSAs. By contrast, processing of the different BSAs by left hemisphere-damaged patients was strongly affected by perisylvian lesion location, with each BSA showing a distinct pattern of localization. This finding raises the possibility that the classical left perisylvian localization of language functions, as measured by clinical aphasia batteries, partly reflects the localization of the BSAs required to perform these functions.