Action viewing and language in adolescents with autism spectrum disorder.

The mirror neuron system consists of fronto-parietal regions and responds to both goal-directed action execution and observation. The broader action observation network is specifically involved in observation of actions and is thought to play a role in understanding the goals of the motor act, the intention of others, empathy, and language. Many, but not all, studies have found mirror neuron system or action observation network dysfunction in autism spectrum disorder. The objective of this study was to use observation of a goal-directed action fMRI paradigm to examine the action observation network in autism spectrum disorder and to determine whether fronto-parietal activation is associated with language ability. Adolescents with autism spectrum disorder (n = 23) were compared to typically developing adolescents (n = 20), 11-17 years. Overall, there were no group differences in activation, however, the autism spectrum group with impaired expressive language (n = 13) had significantly reduced inferior frontal and inferior parietal activation during action viewing. In controls, right supramarginal gyrus activation was associated with higher expressive language; bilateral supramarginal and left pars opercularis activation was associated with better verbal-gesture integration. Results suggest that action-observation network dysfunction may characterize a subgroup of individuals with autism spectrum disorder with expressive language deficits. Therefore, interventions that target this dysfunctional network may improve expressive language in this autism spectrum subgroup. Future treatment studies should individualize therapeutic approaches based on brain-behavior relationships.

Frontal lesions predict response to prism adaptation treatment in spatial neglect: A randomised controlled study.

Spatial neglect commonly follows right hemisphere stroke. It is defined as impaired contralesional stimulus detection, response, or action, causing functional disability. While prism adaptation treatment is highly promising to promote functional recovery of spatial neglect, not all individuals respond. Consistent with a primary effect of prism adaptation on spatial movements, we previously demonstrated that functional improvement after prism adaptation treatment is linked to frontal lobe lesions. However, that study was a treatment-only study with no randomised control group. The current study randomised individuals with spatial neglect to receive 10 days of prism adaptation treatment or to receive only standard care (control group). Replicating our earlier results, we found that the presence of frontal lesions moderated response to prism adaptation treatment: among prism-treated patients, only those with frontal lesions demonstrated functional improvements in their neglect symptoms. Conversely, among individuals in the standard care control group, the presence of frontal lesions did not modify recovery. These results suggest that further research is needed on how frontal lesions may predict response to prism adaptation treatment. Additionally, the results help elucidate the neural network involved in spatial movement and could be used to aid decisions about treatment.

Limb Apraxia: a Disorder of Learned Skilled Movement.

PURPOSE OF REVIEW: This chapter focuses on limb apraxia, a cognitive-motor disorder of learned skilled movement, and the nature of the spatiotemporal errors that disrupt movement sequences. RECENT FINDINGS: A cognitive model that attempts to reconcile conceptual and preparatory aspects of the motor program with perceptual and kinematic features will be discussed. An update on the localization of the praxis network will be provided. In addition, a long-held view that limb apraxia does not have ecological relevance will be disputed in the context of studies that have shown that limb apraxia (i) is one of the most important predictors of increased caregiver burden and (ii) is associated with impaired activities of daily living in post-stroke patients. This review summarizes current screening tools and the few randomized clinical controlled treatment studies to date. Limb apraxia is underdiagnosed and very few therapeutic options are available. Cognitive process models should be used to inform future controlled multi-modal treatment strategies.

Atypical activation of action-semantic network in adolescents with autism spectrum disorder.

In typical adults, fMRI studies have shown activation of primary and pre-motor regions during action word processing. Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by social and communication impairments. ASD studies have shown atypical semantic processing and motor deficits. The objective of this study was to examine semantic processing of verbs in ASD. 15 ASD adolescents and 19 typically developing adolescents, 11-16years, completed a semantic similarity judgment task during fMRI. There were no differences in task accuracy or reaction time. At the group level, both groups had activation in left language areas; controls, but not ASD, also had activation in the left pre-supplementary motor area (pre-SMA). In ASD, less left frontal activation and reduced left lateralization of activation within these regions was associated with shorter reaction times and better language skills. More left temporal activation was associated with better language abilities in ASD. Differences in pre-SMA activation may relate to motor planning deficits or differences in approach to the semantic task in ASD. Results suggest that left frontal language areas may be less efficient in ASD and those who can compensate by recruiting more right hemisphere homologues may result in better language abilities.

Atypical caudate anatomy in children who stutter.

A temporal motor defect in speech preparation and/or planning may contribute to the development of stuttering. This defect may be linked to a dysfunctional cortical-subcortical network at the level of the striatum. To determine whether structural differences exist and whether group differences are associated with stuttering severity or manual laterality, the caudate was measured in 14 children who stutter (CWS) and in a control group of right-handed boys, ages 8-13 years. There was a statistically significant hemisphere by group effect for caudate volume. CWS had reduced right caudate volume and atypical leftward asymmetry compared to controls. Nine of the 13 CWS with atypical caudate asymmetry had atypical manual laterality. These anomalies may represent a vulnerability that perturbs speech planning/preparation and contributes to inefficiencies in action-perception coupling that may be an indicator of stuttering susceptibility. These results suggest that right-handed boys who stutter may have a defect in the feedforward cortico-striato-thalamo-cortical networks.

Prefrontal and occipital asymmetry and volume in boys with autism spectrum disorder.

OBJECTIVE: To examine prefrontal and occipital asymmetry (brain torque) in boys with autism spectrum disorder (ASD) and controls. A secondary aim was to study age-related changes in gray and white matter volume. BACKGROUND: Several studies have found atypical early cortical development in ASD. Atypical brain torque, defined as a greater-than-normal left prefrontal and right occipital asymmetry, has been found in some studies of children and adults with ASD. This configuration may be an early neural marker of ASD risk. METHODS: We studied 24 right-handed boys with ASD and 27 typically developing right-handed boys, 7 to 15 years old, obtaining neuropsychological profiles and measuring prefrontal and occipital volumes on magnetic resonance images. RESULTS: Most participants had the expected rightward prefrontal and leftward occipital asymmetry, with no group differences in direction or degree of asymmetry. We found a trend toward larger prefrontal volume in the ASD group than in the controls. The controls also had a trend toward differences in age associations, correlating with total and left prefrontal white matter volumes. CONCLUSIONS: Our findings suggest that atypical brain torque may not be a neural signature of ASD, although our sample was limited to high-functioning, right-handed boys. Our results provide support for aberrant cortical development in ASD, continuing into adolescence, with prefrontal regions being disproportionally affected.

Modulation of sensory and motor cortex activity during speech preparation.

Previous studies have shown that speaking affects auditory and motor cortex responsiveness, which may reflect the influence of motor efference copy. If motor efference copy is involved, it would also likely influence auditory and motor cortical activity when preparing to speak. We tested this hypothesis by using auditory event-related potentials and transcranial magnetic stimulation (TMS) of the motor cortex. In the speech condition subjects were visually cued to prepare a vocal response to a subsequent target, which was compared to a control condition without speech preparation. Auditory and motor cortex responsiveness at variable times between the cue and target were probed with an acoustic stimulus (Experiment 1, tone or consonant-vowels) or motor cortical TMS (Experiment 2). Acoustic probes delivered shortly before targets elicited a fronto-central negative potential in the speech condition. Current density analysis showed that auditory cortical activity was attenuated at the beginning of the slow potential in the speech condition. Sensory potentials in response to probes had shorter latencies (N100) and larger amplitudes (P200) when consonant-vowels matched the sound of cue words. Motor cortex excitability was greater in the speech than in the control condition at all time points before picture onset. The results suggest that speech preparation induces top-down regulation of sensory and motor cortex responsiveness, with different time courses for auditory and motor systems.

Relevance of subcortical stroke in dysphagia.

BACKGROUND AND PURPOSE: Unilateral cortical lesions are associated with dysphagia in ischemic stroke. It is unclear, however, whether acute subcortical stroke is associated with a similar risk of dysphagia. The aim of this study was to determine the occurrence of dysphagia in purely subcortical stroke and identify dysphagia characteristics. METHODS: Between 2003 and 2005, videofluoroscopic swallow studies (VFSSs) were completed in 20 consecutive ischemic stroke patients with purely subcortical lesions (right hemisphere damage [RHD]=10, left hemisphere damage [LHD]=10) and 25 age-matched controls. Individuals were classified with dysphagia when at least 2 swallowing measures were 2 standard deviations above mean scores for the control group. Lesion volume, hemisphere, and location were determined from diffusion-weighted magnetic resonance imaging scans. RESULTS: Seven subcortical stroke patients (35%) met VFSS criteria for dysphagia (LHD=5, RHD=2); 4 patients presented with clinically significant dysphagia. A significant interaction between hemisphere and lesion location was identified. Whereas 3 of 5 patients with dysphagia (60%) had lesions to the left periventricular white matter (PVWM), LHD patients without dysphagia did not have PVWM lesions. In contrast, no RHD patients with PVWM lesions had dysphagia, and 6 of 8 patients without dysphagia (75%) had PVWM lesions. Oral transfer was significantly slower in patients with subcortical stroke compared with the healthy adults. CONCLUSIONS: Lesions to the left PVWM may be more disruptive to swallowing behavior than similar lesions to the right PVWM. Swallowing deficits involving oral control and transfer may be a marker of subcortical neural axis involvement.

Defining and measuring dysphagia following stroke.

PURPOSE: To continue the development of a quantified, standard method to differentiate individuals with stroke and dysphagia from individuals without dysphagia. METHOD: Videofluoroscopic swallowing studies (VFSS) were completed on a group of participants with acute stroke (n = 42) and healthy age-matched individuals (n = 25). Calibrated liquid volumes of 3, 5, 10, and 20 ml were administered during the VFSS. Six measures in 3 domains of bolus flow (timing, direction, and clearance) were measured. Values of these measures obtained from the control group were used to classify dysphagia within the participants. RESULTS: The use of a single measure or single liquid volumes to classify dysphagia did not distinguish between healthy adults and individuals following stroke with and without dysphagia. Abnormality on more than 1 measure across multiple volumes appears to be a more robust method in defining dysphagia for liquids. CONCLUSIONS: Our findings indicate that the definition of dysphagia is critical in determining whether persons are classified with disordered swallowing. The definition is dependent on materials and measures evaluated. Each measure provides independent aspects to the evaluation. Determining the level of importance of each depends on the purpose of the evaluation.

Atypical PT anatomy in children with autism spectrum disorder with expressive language deficits.

Deficits in communication are a core feature of autism spectrum disorder (ASD), however, structural language abilities are highly variable, ranging from minimally verbal to superior linguistic skills. Differences in the anatomy of cortical language regions, including anterior and posterior areas, have been found in ASD. It remains unclear, however, if anatomical differences distinguish individuals with impaired expressive language from those without such deficits. In addition, anatomical differences have not been explored in children with extremely low expressive language. This study included 34 boys with ASD, 7-11 years old, including an expressive language impaired group (n = 17) and an average-high language group (n = 17). The language impaired group was subdivided into a low (n = 9) and extremely low (n = 8) language subgroup for exploratory analyses to determine whether children with ASD with extremely low expressive language abilities exhibit distinct anatomy. Gray matter volume of the pars triangularis, pars opercularis, and planum temporale (PT) were measured on MRIs. PT volume was smaller in the ASD group with expressive language impairment relative to those without language deficits. The right PT volume was also positively correlated with language scores. The exploratory analyses revealed differences in the left PT, with smaller volume in the extremely low language subgroup, relative to the average and moderately low language groups. Results suggest that smaller PT volumes in both hemispheres are associated with severe language impairments in ASD. The PT may therefore, be a biomarker of language outcome in young children with ASD, with more studies of PT anatomy necessary.

Anatomical asymmetries of anterior perisylvian speech-language regions.

Anterior cortical perisylvian areas important for speech and language functions include the pars triangularis (PTR), comprised of heteromodal association cortex, and the pars opercularis (POP), comprised of motor association cortex. The anatomy of these frontal language regions has not been well studied in large samples, however in smaller samples, leftward asymmetry of these regions has been found. Sex-linked differences have also been suggested, with bilateral activation of frontal language areas in women and leftward activation in men. We used volumetric MRI methods to measure the gray matter volume of the PTR, POP, and diagonal sulcus (DS) in 60 healthy right-handed adults and examined the distribution of asymmetry of these regions. Sex-linked differences in volume and asymmetry of anterior speech regions were also examined. For the PTR, there was a slight leftward asymmetry, however for the POP+DS, there was a slight rightward asymmetry. The DS was present slightly more often in the right hemisphere than in the left hemisphere and its frequency was similar in men and women. There were no significant sex-linked differences in volume or asymmetry for any of these frontal areas. More studies are necessary, looking at the anatomy of anterior language regions in large samples and examining the relationship between anatomy and function.

Verbal dichotic listening in right and left-handed adults: laterality effects of directed attention.

Dichotic listening performance of consonant vowel stimuli was studied in 51 adult right- and left-handers in three attention conditions: non-directed and directed to either the right or left ear. In the non-directed condition, a significant right-ear advantage was found in both handedness groups with a stronger asymmetry in right-handers. There are at least three explanations for this ear bias. The classic or structural hypothesis suggests that to the right ear projects more strongly to the language dominant left hemisphere. The callosal relay hypothesis is based on the influence of inhibitory connections via the corpus callosum. The attentional hypothesis suggests that each hemisphere primarily directs attention to contralateral space and because the left hemisphere is dominant for language in both groups, and is aroused by speech stimuli, attention is primarily directed to the right ear. Neither hypothesis can explain why greater than 95% of right-handers have left hemisphere language dominance, but only 70-80% have a right ear bias. Our results demonstrate that in the directed attention conditions both groups increased their lateral biases when directed to either the right or left. The classic or structural hypothesis cannot account for these changes, thereby providing support for the attentional hypothesis. In addition, the right-handed subjects exhibited a greater shift of bias than did the left-handed subjects, when directing their attention leftward. This finding suggests that right-handed people are better able to shift their attention than left-handed people.

Lobar asymmetries in subtypes of dyslexic and control subjects.

Reading involves phonologic decoding, in which readers "sound out" a word; orthographic decoding, in which readers recognize a word visually, as in "sight reading"; and comprehension. Because reading can involve multiple processes, dyslexia might be a heterogeneous disorder. This study investigated behavior and gross lobar anatomy in subtypes of dyslexic and control subjects. Subjects aged 18 to 25 years with identified reading problems and a group of healthy controls were given cognitive and behavioral tests and volumetric brain magnetic resonance imaging (MRI). Because atypical cerebral laterality has been proposed as a potential neural risk for dyslexia, dyslexic and control subjects were compared on anatomy of gross lobar regions. On asymmetry quotients, no significant differences were found between groups. Examination of the percentage of total brain volume of each structure revealed that control and dyslexic subjects were significantly different (P = .018). Dyslexic subjects had a larger percentage of brain volume than did the controls in the areas of total prefrontal (P = .003; 9.30% larger) and superior prefrontal (P = .004; 11.48% larger region). A Pearson correlation was performed to investigate whether a relationship existed between behavioral measures and either volumes of total prefrontal and total occipital regions or asymmetry quotients. A significant positive relationship between the left total occipital and word identification performance existed (R = .452, P = .045). Because it is believed by some that dyslexia occurs in varying degrees of severity, and because one of the research questions in this study is whether anatomy relates to severity or to distinct biologic groups, subjects were grouped according to both the nature and distinct pattern of reading or language performance and the degree of deficit. A battery of reading tests revealed five clinical subgroups of control (two) and dyslexic (three) subjects. These subgroups were statistically different on all cognitive and behavioral measures. When asymmetry was investigated across subgroups, significant differences between subgroups were found at the multivariate level (P = .043). Only the phonologic deficit groups (weak phonologic controls, phonologic deficit dyslexic subjects) had atypical asymmetry patterns. This finding suggests that lack of subtyping could have confounded earlier studies and that anomalous asymmetry might be related to phonologic dyslexia, whereas other subtypes might be reflective of environmental factors. Examination of volume at the subgroup level also showed differences between subgroups that might have implications for the nature of compensation. This study supports the concept that anomalous anatomy might reflect anomalous functional cerebral laterality, which could be a risk factor for developmental dyslexia, varying according to the nature of the deficit.

Variability in perisylvian brain anatomy in healthy adults.

Gray matter volumes of Heschl's gyrus (HG), planum temporale (PT), pars triangularis (PTR), and pars opercularis were measured on MRI in 48 healthy right-handers. There was the expected leftward PT asymmetry in 70.8%, and leftward PTR asymmetry in 64.6% of the sample. When asymmetry patterns within individuals were examined, there was not one typical pattern, rather several typical configurations were found. In addition, some combinations of asymmetry did not exist in our sample suggesting that some perisylvian anatomical configurations may provide a more suitable neural substrate for the development of language than others. There were also sex differences in HG. Men had rightward asymmetry and women demonstrated leftward asymmetry, due to women having smaller right HG, compared to men.

Handedness in Children With Autism Spectrum Disorder.

The left hemisphere is usually predominant in manual skills and language, suggesting a link between hand dominance and language. Studies of autism spectrum disorder show atypical handedness; however, few have examined language-handedness associations. Handedness, assessed by task performance, and standardized receptive and expressive language tests were completed in 110 autism spectrum disorder children (96 boys; M age = 8.3 years, SD = 3.8) and 45 typically developing children (37 boys; M age = 8.6 years, SD = 4.3), 3 to 17 years of age. The autism spectrum disorder group had a lower handedness score (was less strongly lateralized) than the control group. In the autism spectrum disorder group, there was a small effect of handedness on language; right-handers had better language than non-right-handers. Results suggest poorer language prognosis may be associated with left- or mixed-handedness in autism spectrum disorder.

Cortical activity during cued picture naming predicts individual differences in stuttering frequency.

OBJECTIVE: Developmental stuttering is characterized by fluent speech punctuated by stuttering events, the frequency of which varies among individuals and contexts. Most stuttering events occur at the beginning of an utterance, suggesting neural dynamics associated with stuttering may be evident during speech preparation. METHODS: This study used EEG to measure cortical activity during speech preparation in men who stutter, and compared the EEG measures to individual differences in stuttering rate as well as to a fluent control group. Each trial contained a cue followed by an acoustic probe at one of two onset times (early or late), and then a picture. There were two conditions: a speech condition where cues induced speech preparation of the picture's name and a control condition that minimized speech preparation. RESULTS: Across conditions stuttering frequency correlated to cue-related EEG beta power and auditory ERP slow waves from early onset acoustic probes. CONCLUSIONS: The findings reveal two new cortical markers of stuttering frequency that were present in both conditions, manifest at different times, are elicited by different stimuli (visual cue, auditory probe), and have different EEG responses (beta power, ERP slow wave). SIGNIFICANCE: The cue-target paradigm evoked brain responses that correlated to pre-experimental stuttering rate.

Speech preparation in adults with persistent developmental stuttering.

Motor efference copy conveys movement information to sensory areas before and during vocalization. We hypothesized speech preparation would modulate auditory processing, via motor efference copy, differently in men who stutter (MWS) vs. fluent adults. Participants (n=12/group) had EEG recorded during a cue-target paradigm with two conditions: speech which allowed for speech preparation, while a control condition did not. Acoustic stimuli probed auditory responsiveness between the cue and target. MWS had longer vocal reaction times (p<0.01) when the cue-target differed (10% of trials), suggesting a difficulty of rapidly updating their speech plans. Acoustic probes elicited a negative slow wave indexing motor efference copy that was smaller in MWS vs. fluent adults (p<0.03). Current density responses in MWS showed smaller left prefrontal responses and auditory responses that were delayed and correlated to stuttering rate. Taken together, the results provide insight into the cortical mechanisms underlying atypical speech planning and dysfluencies in MWS.

Ipsilesional neglect: behavioral and anatomical correlates.

UNLABELLED: [Correction Notice: An Erratum for this article was reported in Vol 29(2) of Neuropsychology (see record 2014-42242-001). The funding source information was missing from the author note, and A. M. Barrett's institutional affiliation was incorrect. The funding source information and Barrett's correct institutional affiliation are provided in the erratum.] OBJECTIVE: The sparse existing research on ipsilesional neglect supports an association of this disorder with damage to the right frontal and subcortical brain networks. It is believed that dysfunction in these networks may result in primarily "aiming" motor-intentional spatial errors. The purpose of this study was to confirm whether frontal-subcortical circuits are indeed commonly affected in ipsilesional neglect and to determine the relative presence of "aiming" motor-intentional versus "where" perceptual-attentional spatial errors in these individuals. METHODS: We identified 12 participants with ipsilesional neglect based on a computerized line bisection task and used the line bisection data to quantify participants' perceptual-attentional and motor-intentional errors. We were able to discriminate between these 2 biases using the algebraic solutions for 2 separate equations, one for "aiming" and one for "where" biases. Lesion mapping was conducted for all participants using MRIcron software; lesion checklist and overlap analysis were created from these images. RESULTS: A greater percentage of participants with ipsilesional neglect had frontal/subcortical damage (83%) compared with the expected percentage (27%) observed in published patient samples with contralesional neglect. We observed the greatest area of lesion overlap in frontal lobe white matter pathways. Nevertheless, participants with ipsilesional neglect made primarily "where" rather than "aiming" spatial errors. CONCLUSION: Our data confirm previous research suggesting that ipsilesional neglect may result from lesions to the right frontal-subcortical networks. Furthermore, in our group, ipsilesional neglect was also strongly associated with primarily "where" perceptual-attentional bias, and less so with "aiming" motor-intentional spatial bias.

Sex-linked differences in the anatomy of the perisylvian language cortex: a volumetric MRI study of gray matter volumes.

Perisylvian regions important for auditory processing include Heschl's gyrus (HG), the planum temporale (PT), the posterior superior temporal gyrus (pSTG), and the posterior ascending ramus (PAR). Sex-linked differences in language functions and anatomy have been suggested. To examine sex-linked differences, the authors used MRI to measure HG, PT, pSTG, and PAR volumes. Sex differences were found in right HG and right pSTG volumes but not in the left volumes of these structures. For the PT, there were sex differences in asymmetry; women exhibited leftward asymmetry of the PT, whereas men did not exhibit PT asymmetry. These findings suggest that there are sex-linked differences in the anatomy of primary and association auditory cortices.

Variability in the anatomy of the planum temporale and posterior ascending ramus: do right- and left handers differ?

The anatomy of the planum temporale (PT) and posterior ascending ramus (PAR) was studied in vivo in 67 healthy right- and left-handed adults using MRI-based morphometry. The left PT was significantly larger than the right, and there was a weakly significant effect of the right PAR larger than the left. A leftward PT asymmetry was found in 72%, and a rightward PAR asymmetry was found in 64% of the sample. The "typical" configuration of a larger left PT and larger right PAR co-occurred in 56% of the subjects studied, which was only slightly more often than predicted by chance. Eight of 67 subjects had "reversed" PT and PAR asymmetries, with consistent left and mixed handers over-represented in this group. Right PAR size was the only variable that predicted writing hand, and left PT size was the only measure that differed by sex. The left PT was expanded relative to the left PAR in 93% of the sample, suggesting that this configuration may be developmentally regulated and may be a critical substrate for the development of language. These findings demonstrate that important relationships exist between hand preference, and the anatomy of posterior cortical language areas.