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).     

Narrative Discourse in Children with Early Focal Brain Injury

Children with early brain damage, unlike adult stroke victims, often go on to develop nearly normal language. However, the route and extent of their linguistic development are still unclear, as is the relationship between lesion site and patterns of delay and recovery. Here we address these questions by examining narratives from children with early brain damage. Thirty children (ages 3;7–10;10) with pre- or perinatal unilateral focal brain damage and their matched controls participated in a storytelling task. Analyses focused on linguistic proficiency and narrative competence. Overall, children with brain damage scored significantly lower than their age-matched controls on both linguistic (morphological and syntactic) indices and those targeting broader narrative qualities. Rather than indicating that children with brain damage fully catch up, these data suggest that deficits in linguistic abilities reassert themselves as children face new linguistic challenges. Interestingly, after age 5, site of lesion does not appear to be a significant factor and the delays we have witnessed do not map onto the lesion profiles observed in adults with analogous brain injuries.     

The Effect of Emotional Reactions upon Retention

Studies pertaining to recovery of function following either serial ablations or early brain damage were reviewed. In general, serial damage leads to greater functional sparing than simultaneous damage to the same area. Similarly, brain damage sustained early in the developmental history of the organism is less traumatic in terms of subsequent behavior than later injury. Variables relevant to the generality of the phenomena were emphasized, and possible avenues for future investigation were suggested.     

Event-related potentials in neuropsychological studies of language

Experiments are described in which event-related potentials (ERPs) are employed to study the specialization of functions between and within the cerebral hemispheres during the performance of language and nonlanguage tasks by normal adults. Similar studies of deaf subjects suggest that the functional organization of the brain may be altered after different early language and sensory experiences. Studies of patients with alexia without agraphia suggest that the ERP may be a valuable tool with which to study cerebral reorganization after brain damage.     

"Frog, where are you?" Narratives in children with specific language impairment, early focal brain injury, and Williams syndrome

In this cross-population study, we use narratives as a context to investigate language development in children from 4 to 12 years of age from three experimental groups: children with early unilateral focal brain damage (FL; N=52); children with specific language impairment (SLI; N=44); children with Williams syndrome (WMS; N=36), and typically developing controls. We compare the developmental trajectories of these groups in the following domains: morphological errors, use of complex syntax, complexity of narrative structure, and types and frequency of evaluative devices. For the children with early unilateral brain damage, there is initial delay. However, by age 10, they are generally within the normal range of performance for all narrative measures. Interestingly, there are few, if any, side specific differences. Children with SLI, who have no frank neurological damage and show no cognitive impairment demonstrate significantly more delay on all morphosyntactic measures than the FL group. Quantitatively, on morphosyntactic measures, the SLI group clusters with those children with WMS who are moderately retarded. Together these data help us to understand the extent and nature of brain plasticity for language development and those aspects of language and discourse that are dissociable.     

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.     

Neuropsychological profile following suicide attempt by hanging: two adolescent case reports.

Hippocampal damage and amnesia following hypoxia and ischemia are described in the few published adult cases of suicide attempt by hanging. However, a recent review (Caine & Watson, 2000) suggests a variable pattern of brain involvement and neuropsychological impairments following hypoxic-ischemic injury that may or may not involve amnesia. To help clarify the impact of hanging on the developing brain, we examined neuropsychological functioning in two adolescents who survived suicide attempt by hanging. Despite differences in Glasgow Coma Scale (GCS), coma duration, and structural imaging findings, both patients had similar IQ (VIQ>PIQ) and presented with various combinations of deficits in expressive/receptive language, visual-constructional and perceptual ability, processing speed, attention, working memory, and/or executive functioning shortly after injury. In spite of their similarities, only one of the patients presented with classic amnesia symptoms in his early recovery. This patient was evaluated 1 year postinjury, and persistent deficits in processing speed and memory encoding were noted. Several hanging-related variables, including longer estimated hanging duration, greater weight, and severe airway edema, were thought to place this patient at increased risk for cognitive deficits. Clinical MRI scans of this patient obtained 6 weeks postinjury revealed mild volume loss as well as abnormalities in bilateral superior cortex. However, CT and MRI scans obtained throughout early recovery did not reveal overt evidence of injury to specific memory-related structures. Comprehensive neuropsychological evaluation of all adolescent survivors of suicide attempt by hanging is recommended, as a variety of postacute cognitive deficits were observed in these patients despite relatively short (相似文献   

Developmental outcomes after early prefrontal cortex damage

The neuropsychological bases of cognitive, social, and moral development are minimally understood, with a seemingly wide chasm between developmental theories and brain maturation models. As one approach to bridging ideas in these areas, we review 10 cases of early prefrontal cortex damage from the clinical literature, highlighting overall clinical profiles and real life developmental outcomes. Based on these cases, there is preliminary evidence to support distinctive developmental differences after: (1) dorsolateral, (2) mesial, and (3) orbital-polar prefrontal lesions, for more profound impairments after bilateral damage, and possibly for recovery differences after very early vs. later childhood lesion onset. Further case and group studies are needed to confirm reliable effects of specific lesion locations, the influence of age of lesion onset, and related experiential and treatment variables in determining adult outcomes. Rather than a single underlying deficit associated with early prefrontal cortex damage, we interpret the findings to suggest that it is the altered integration and interplay of cognitive, emotional, self-regulatory, and executive/metacognitive deficits that contribute to diverse developmental frontal lobe syndromes. The findings support the fundamental importance of prefrontal cortex maturation in protracted cognitive, social-emotional, and moral development.     

Altered lateralization of dorsal language tracts in 6‐week‐old infants at risk for autism

Altered structural connectivity has been identified as a possible biomarker of autism spectrum disorder (ASD) risk in the developing brain. Core features of ASD include impaired social communication and early language delay. Thus, examining white matter tracts associated with language may lend further insight into early signs of ASD risk and the mechanisms that underlie language impairments associated with the disorder. Evidence of altered structural connectivity has previously been detected in 6‐month‐old infants at high familial risk for developing ASD. However, as language processing begins in utero, differences in structural connectivity between language regions may be present in the early infant brain shortly after birth. Here we investigated key white matter pathways of the dorsal language network in 6‐week‐old infants at high (HR) and low (LR) risk for ASD to identify atypicalities in structural connectivity that may predict altered developmental trajectories prior to overt language delays and the onset of ASD symptomatology. Compared to HR infants, LR infants showed higher fractional anisotropy (FA) in the left superior longitudinal fasciculus (SLF); in contrast, in the right SLF, HR infants showed higher FA than LR infants. Additionally, HR infants showed more rightward lateralization of the SLF. Across both groups, measures of FA and lateralization of these pathways at 6 weeks of age were related to later language development at 18 months of age as well as ASD symptomatology at 36 months of age. These findings indicate that early differences in the structure of language pathways may provide an early predictor of future language development and ASD risk.     

A proposed regional hierarchy in recovery of post-stroke aphasia

Activation studies in patients with aphasia due to stroke or tumours in the dominant hemisphere have revealed effects of disinhibition in ipsilateral perilesional and in contralateral homotopic cortical regions, referred to as collateral and transcallosal disinhibition. These findings were supported by studies with selective disturbance of cortical areas by repetitive transcranial magnetic stimulation (rTMS) in healthy volunteers and in patients with focal brain lesions. Both, collateral as well as transcallosal disinhibition might be relevant for the compensation of lesions within a functional network. From these data a hierarchical organization of recovery of aphasia after stroke and of compensation of language defects due to brain tumours can be deduced, by which the reactivation of undamaged network areas of the ipsilateral hemisphere usually lead to better outcome than the involvement of homotopic contra-lateral regions. rTMS can be used to identify areas relevant for speech production and might play a role in treatment strategies targeted at modulating the activity of contralateral homotopic areas of the functional network which might interfere with language recovery.     

聋人早期手语经验对脑功能及结构的塑造作用

语言经验对脑功能和结构发展有重要的塑造作用。然而, 目前的相关证据主要来自对脑损伤导致的失语症病人的语言康复、第二语言学习以及针对成人读者进行的语言训练等方面的研究。幼儿时期的早期语言经验对脑结构与功能发展的影响更加重要, 但直接的研究证据却相当缺乏。本文提出一个研究设想, 拟综合使用多种脑成像技术, 系统探讨有早期手语经验和无早期手语经验的聋人个体在脑皮层语言功能的组织及脑结构发育的差异, 包括语言任务中大脑语言区的激活模式, 静息状态下脑功能联结的默认网络特征, 脑皮层灰质密度, 以及神经纤维束发育状况等, 揭示早期语言经验对大脑功能和结构发育的塑造作用。     

Acquisition of lexical morphology in simple partial epilepsy.

In the study of language acquisition following early brain damage, results have been divergent. On one hand, some studies claim that language eventually resumes to normal, whereas, on the other hand, studies show lasting deficits throughout development. Discrepancies in the results could arise from different etiologies and tests used. This study attempts to determine the extent to which the development of verb production is affected in later development in children who had simple partial epilepsy (SPE). Measures of diversity and fluency of three verb types, namely main verbs, auxiliary and copula verbs, and nonfinite verbs were used on three children diagnosed as SPE and compared to control groups. Our main results show a limited production of auxiliary verbs. Further analysis of their productions suggest a telegraphic style of speech, as reflected by a superior production of nonfinite verb type compared with normal children. These findings are interpreted as reflecting long-lasting consequences of early brain damage with respect to language development.     

Bilingualism alters children's frontal lobe functioning for attentional control

Bilingualism is a typical linguistic experience, yet relatively little is known about its impact on children's cognitive and brain development. Theories of bilingualism suggest that early dual‐language acquisition can improve children's cognitive abilities, specifically those relying on frontal lobe functioning. While behavioral findings present much conflicting evidence, little is known about its effects on children's frontal lobe development. Using functional near‐infrared spectroscopy (fNIRS), the findings suggest that Spanish–English bilingual children (n = 13, ages 7–13) had greater activation in left prefrontal cortex during a non‐verbal attentional control task relative to age‐matched English monolinguals. In contrast, monolinguals (n = 14) showed greater right prefrontal activation than bilinguals. The present findings suggest that early bilingualism yields significant changes to the functional organization of children's prefrontal cortex for attentional control and carry implications for understanding how early life experiences impact cognition and brain development.     

From the left to the right: How the brain compensates progressive loss of language function

In normal right-handed subjects language production usually is a function oft the left brain hemisphere. Patients with aphasia following brain damage to the left hemisphere have a considerable potential to compensate for the loss of this function. Sometimes, but not always, areas of the right hemisphere which are homologous to language areas of the left hemisphere in normal subjects are successfully employed for compensation but this integration process may need time to develop. We investigated right-handed patients with left hemisphere brain tumors as a model of continuously progressive brain damage to left hemisphere language areas using functional neuroimaging and transcranial magnetic stimulation (TMS) to identify factors which determine successful compensation of lost language function. Only patients with slowly progressing brain lesions recovered right-sided language function as detected by TMS. In patients with rapidly progressive lesions no right-sided language function was found and language performance was linearly correlated with the lateralization of language related brain activation to the left hemisphere. It can thus be concluded that time is the factor which determines successful integration of the right hemisphere into the language network for compensation of lost left hemisphere language function.     

Early gender differences in the functional usage of language

Early male and female differences in the functional use of language were investigated by coding the verbal interactions of 32 preschool children during a 10-minute play session with same-sex peer. The speech of each child was classified into functional-motivational categories using the FIS-P scoring instrument. The findings were consistent with the literature on adult conversational styles, showing that males talk more and are more assertive in their social interactions than are females. The results of this study demonstrate the existence of early gender differences in the functional use of language and emphasize the importance of a developmental approach to the study of communication styles.     

Baby babbling at five months linked to sex hormone levels in early infancy

Gender-dependent differentiation of the brain at morphological, neurochemical and functional levels of organization have been shown to be primarily controlled by sex differences in gonadal hormone concentrations during pre- and early postnatal development. Indeed, previous studies have reported that pre- and perinatal hormonal environments influence brain development and, consequently, affect sex specific long-term language outcomes.Herein, we investigated whether postnatal surges of estrogen (estradiol) and androgen (testosterone) may predict properties of pre-speech babbling at five months. This study is the first attempt to investigate a possible correlation between sex hormones and infants’ articulatory skills during the typical postnatal period of extended hormonal activity known as ‘mini-puberty.’ A hierarchical, multiple regression approach revealed a significant, robust positive relationship between 4-week concentrations of estradiol and individual articulatory skills. In contrast, testosterone concentrations at five months negatively correlated with articulatory skills at the same age in both boys and girls. Our findings reinforce the assumption of the importance of sex hormones for auditory–vocal development towards language in human infants.     

Early language development after peri-natal stroke

Early unilateral brain damage has different implications for language development than does similar damage in adults, given the plasticity of the developing brain. The goal of this study was to examine early markers of language and gesture at 12 and 24 months in children who had peri-natal right hemisphere (RH) or left hemisphere (LH) stroke (n = 71), compared with typically developing controls (n = 126). Parents completed the MacArthur-Bates Communicative Development Inventory (CDI): Words & Gestures (12 month data point), or the CDI: Words & Sentences (24 month data point). Statistical analyses were performed on percentile scores using analysis of variance techniques. At 12 months, there were no differences among groups for Words Understood, Phrases Understood or Words Produced. At 24 months, both lesion groups scored significantly lower than controls on Word Production, Irregular Words, and Mean Length of Sentences, but lesion groups did not differ from each other. In a longitudinal subset of participants, expressive vocabulary failed to progress as expected from 12 to 24 months in the stroke group, with no differences based on lesion side. Gesture and word production were dissociated in the left hemisphere subjects. Findings suggest that early language development after peri-natal stroke takes a different course from that of typical language development, perhaps reflecting brain reorganization secondary to plasticity in the developing brain.     

Oscillatory gamma activity mediates the pathway from socioeconomic status to language acquisition in infancy

BackgroundThe predictable path to child language acquisition is largely constrained by both brain maturation and environmental experience. The synchronized activity of large numbers of neurons gives rise to macroscopic brain oscillations on an electroencephalogram (EEG). It has been found that neural oscillations at rest in the gamma frequency band (25–45 Hz) are associated with development of different cognitive systems, including language. Although the etiology of language is explained by genetically driven brain maturation factors, environment plays a significant role. Specifically, candidate pathways from environment to language development include sociodemographic factors, primarily socioeconomic status (SES) which is likely to exert its effects on language development through other factors, such as parenting style.Despite these assumptions, no studies have so far examined the interrelation between brain maturation factors such as gamma frequency oscillatory activity, environmental factors such as SES, and language acquisition.Aim and methodIn a longitudinal study of 84 Italian typically developing infants, we measured the power of oscillatory gamma activity as mediator between SES and language acquisition. Baseline EEG and information about SES were collected when infants were aged 6 months. Children were followed-up longitudinally to measure expressive vocabulary and Mean Length of Utterance (MLU) at 24 months.ResultsThe mediation model showed that SES is associated with gamma power which, in turn, is associated with expressive language at age 24 months. A higher SES predicted an increase in left central gamma power which, in turn, predicted better language scores.ConclusionsThese results confirm the predictive role of gamma activity oscillatory activity on later language acquisition, suggesting a specific role for these oscillatory mechanisms in language development milestones such as vocabulary development and early word combination. Furthermore, they suggest that SES differences in brain activity may be apparent at early stages of life and affect later language skills. If replicated, our findings could contribute to identifying highest-risk children and may prompt cost-effective preventive/treatment strategies.     

Neuroprotection and stroke rehabilitation: modulation and enhancement of recovery

Recent advances in research are modifying our view of recovery after nervous system damage. New findings are changing previously held concepts and providing promising avenues for treatment of patients after stroke. This review discusses mechanisms of neuronal injury after brain ischemia and the attempts to study neuroprotection options based on such mechanisms. It also considers measures available at present to improve outcome after stroke and presents new areas of research, particularly stimulation techniques, neurogenesis and trophic factors to enhance recovery. In order to improve outcomes, medications that may be detrimental to recovery should be avoided, while symptomatic therapy of problems such as depression, pain syndromes and spasticity may contribute to better results. Continued surveillance and early treatment of complications associated with acute stroke, along with supportive care remain the mainstay of treatment for stroke patients in the recovery phase. Present research on limiting brain damage and improving recovery and plasticity enhance the prospects for better clinical treatments to improve recovery after stroke.     

The Contribution of Neuroimaging to the Study of Language and Aphasia

New structural and functional imaging methods continue to be developed at a rapid pace. In the last 25 years, advanced imaging techniques have provided insights into how language is represented and processed in the brain and how it can be disrupted by damage to, or dysfunction of, various parts of the brain. Imaging studies have also yielded new information regarding how individuals recover language after stroke. We briefly review the strengths and weaknesses of the various radiological methods currently used to study language and aphasia.