Brain and language
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The inhibition deficit hypothesis (IDH) proposed that individual differences in inhibitory control is an underlying reason for age-related language decline. This study examined whether the hypothesis holds within the domain of lexico-semantic retrieval. Sixty-six older adults aged 60-79 were tested in a semantic fluency task comprising 16 categories; each response was classified as automatic or controlled. ⋯ Mixed-effects modelling revealed that the number of controlled (but not automatic) responses was negatively associated with age. This interaction could be partially accounted for by the behavioral Stroop inhibition score and two neural measures from the ERP flanker task (P2 and Pc amplitudes). These results not only provide converging evidence supporting the IDH, but also demonstrate the involvement of specific inhibitory control components, including attentional control and performance monitoring.
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Developmental stuttering is known to be a sexually dimorphic and male-biased speech motor control disorder. In the present case-control study, we investigated the relationship between developmental stuttering and steroid hormones. Serum levels of testosterone, dihydrotestosterone (DHT), dehydroepiandrosterone (DHEA), oestradiol, progesterone, cortisol, and sex hormone binding globulin (SHBG), as well as the 2nd/4th digit ratio (2D:4D), an indicator of prenatal testosterone level, were compared between children who stutter (CWS) and children who do not stutter (CWNS). ⋯ Our results showed significantly higher levels of testosterone, DHT, and oestradiol in CWS in comparison with CWNS. The severity of stuttering was positively correlated with the serum levels of testosterone, DHEA, and cortisol, whereas no association was seen between the stuttering and digit ratio, progesterone, or SHBG. The CYP17CC genotype was significantly associated with the disorder.
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Randomized Controlled Trial
Reversing Ribot: does regression hold in language of prodromal Alzheimer's disease?
We consider the regression or retrogenesis hypothesis, which argues that order of acquisition in development is reversed in neurodegeneration or pathology. Originally proposed as a regression hypothesis for the study of memory disorders, specifically retrograde amnesia, by Ribot (1881), it has been extended to the study of brain aging and pathology and to language. ⋯ Through interuniversity collaboration using a matched experimental design and task, we compare production of complex sentences containing relative clauses by normal monolingual children during normal development, healthy young adults, healthy aging adults, and aging adults diagnosed with mild cognitive impairment, a recognized potential harbinger of Alzheimer's disease. Our results refute the regression hypothesis in this area and lead to potential syntactic markers for prodromal Alzheimer's disease and predictions for future brain imaging analyses.
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The purpose of the present investigation was to evaluate the contribution of age-at-insult and brain pathology on longitudinal outcome and recovery of pragmatic language in a sample of children and adolescents with traumatic brain injury (TBI). Children and adolescents with mild to severe TBI (n=112) were categorized according to timing of brain insult: (i) Middle Childhood (5-9 years; n=41); (ii) Late Childhood (10-11 years; n=39); and (iii) Adolescence (12-15 years; n=32) and group-matched for age, gender and socio-economic status (SES) to a typically developing (TD) control group (n=43). Participants underwent magnetic resonance imaging (MRI) including a susceptibility weighted imaging (SWI) sequence 2-8 weeks after injury and were assessed on measures of pragmatic language and behavioural functioning at 6- and 24-months after injury. ⋯ Reduced pragmatic communication was associated with frontal, temporal and corpus callosum lesions, as well as more frequent externalizing behaviour at 24-months post injury. Findings show that persisting pragmatic language impairment after pediatric TBI is related to younger age at brain insult, as well as microhemorrhagic pathology in brain regions that contribute to the anatomically distributed social brain network. Relationships between reduced pragmatic communication and more frequent externalizing behavior underscore the need for context-sensitive rehabilitation programs that aim to increase interpersonal effectiveness and reduce risk for maladaptive behavior trajectories into the long-term post injury.
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We conducted an Activation Likelihood Estimation (ALE) meta-analysis to identify brain regions that are recruited by linguistic stimuli requiring relatively demanding semantic or syntactic processing. We included 54 functional MRI studies that explicitly varied the semantic or syntactic processing load, while holding constant demands on earlier stages of processing. ⋯ These results challenge models of sentence comprehension highlighting the role of anterior LIFG for semantic processing. In addition, the results emphasise the posterior (but not anterior) temporal lobe for both semantic and syntactic processing.