229 research outputs found
sj-docx-1-aut-10.1177_13623613211049011 – Supplemental material for Early diagnosis of autism in the community is associated with marked improvement in social symptoms within 1–2 years
No full textSupplemental material, sj-docx-1-aut-10.1177_13623613211049011 for Early diagnosis of autism in the community is associated with marked improvement in social symptoms within 1–2 years by Nitzan Gabbay-Dizdar, Michal Ilan, Gal Meiri, Michal Faroy, Analya Michaelovski, Hagit Flusser, Idan Menashe, Judah Koller, Ditza A Zachor and Ilan Dinstein in Autism</p
Human Cortex: Reflections of Mirror Neurons
No full textSummaryClaims to have identified mirror neurons in human cortex have been controversial. A recent study has applied an fMRI adaptation protocol to the problem and come up with novel evidence for the existence of movement-selective mirror neurons in human cortex
Movement selectivity and the human mirror system
No full textMirror neurons are unique visuomotor neurons that respond when executing a particular movement (e.g. grasping, placing, or manipulating) and also when passively observing someone else performing that same movement. Importantly, subpopulations of mirror neurons respond in a selective manner to one preferred movement whether executed or observed. It has been proposed that the activity of mirror neurons during observation of actions represents an internal "simulation" of the observed action, which enables us to perceive its goal and intention, thereby forming the foundation for social interactions. Mirror neurons are thought to exist in two cortical areas, the anterior intraparietal sulcus (aIPS) and the ventral premotor (vPM), which have been called the human mirror system. A dysfunction in the responses of this system has been hypothesized to cause an impairment in the ability to understand one another resulting in Autism. Here we conducted three studies to characterize the responses of the human mirror system and to test the hypothesis that a dysfunction of the system underlies Autism. In two separate studies we used fMRI adaptation and classification techniques to assess the selectivity of several cortical areas, including mirror system areas, for observed and executed hand movements. Movement-selectivity is a critical feature of neurons involved in movement perception, including mirror neurons. For us to understand the meaning of observed movements we must be able to differentiate between them and represent each with a unique neural response. Converging results from both of the studies showed that both mirror system areas responded in a movement-selective manner. We suggest that these responses were generated by overlapping visual, motor, and visuomotor neural populations, perhaps including mirror neurons, that responded selectively to particular movements. These results elucidate the functional characteristics of neural populations in human mirror system areas and highlight their role in movement perception. In a third study we used the adaptation methodology to compare mirror system responses between Autistic individuals and controls. The results showed that, on average, Autistic individuals exhibited indistinguishable movement-selective responses from those of controls, indicative of intact movement perception. However, the responses of several cortical areas (including, but not limited to the mirror system) were more variable in Autistic individuals than in controls. Taken together, these results suggest that Autistic individuals do not have a selective dysfunction in mirror system areas, but rather exhibit generally noisy and unreliable neural responses, perhaps due to an imbalance of excitation and inhibition throughout multiple brain areas
Effector-invariant movement encoding in the human motor system
No full textIpsilateral motor areas of cerebral cortex are active during arm movements and even reliably predict movement direction. Is coding similar during ipsilateral and contralateral movements? If so, is it in extrinsic (world-centered) or intrinsic (joint-configuration) coordinates? We addressed these questions by examining the similarity of multivoxel fMRI patterns in visuomotor cortical regions during unilateral reaching movements with both arms. The results of three complementary analyses revealed that fMRI response patterns were similar across right and left arm movements to identical targets (extrinsic coordinates) in visual cortices, and across movements with equivalent joint-angles (intrinsic coordinates) in motor cortices. We interpret this as evidence for the existence of distributed neural populations in multiple motor system areas that encode ipsilateral and contralateral movements in a similar manner: according to their intrinsic/joint coordinates
Individual movement variability magnitudes are explained by cortical neural variability
No full textHumans exhibit considerable motor variability even across trivial reaching movements. This variability can be separated into specific kinematic components such as extent and direction that are thought to be governed by distinct neural processes. Here, we report that individual subjects (males and females) exhibit different magnitudes of kinematic variability, which are consistent (within individual) across movements to different targets and regardless of which arm (right or left) was used to perform the movements. Simultaneous fMRI recordings revealed that the same subjects also exhibited different magnitudes of fMRI variability across movements in a variety of motor system areas. These fMRI variability magnitudes were also consistent across movements to different targets when performed with either arm. Cortical fMRI variability in the posterior–parietal cortex of individual subjects explained their movement–extent variability. This relationship was apparent only in posterior-parietal cortex and not in other motor system areas, thereby suggesting that individuals with more variable movement preparation exhibit larger kinematic variability. We therefore propose that neural and kinematic variability are reliable and interrelated individual characteristics that may predispose individual subjects to exhibit distinct motor capabilities
No evidence of early head circumference enlargements in children later diagnosed with autism in Israel
No full textBackground
Large controversy exists regarding the potential existence and clinical significance of larger brain volumes in toddlers who later develop autism. Assessing this relationship is important for determining the clinical utility of early head circumference (HC) measures and for assessing the validity of the early overgrowth hypothesis of autism, which suggests that early accelerated brain development may be a hallmark of the disorder.
Methods
We performed a retrospective comparison of HC, height, and weight measurements between 66 toddlers who were later diagnosed with autism and 66 matched controls. These toddlers represent an unbiased regional sample from a single health service provider in the southern district of Israel. On average, participating toddlers had >8 measurements between birth and the age of two, which enabled us to characterize individual HC, height, and weight development with high precision and fit a negative exponential growth model to the data of each toddler with exceptional accuracy.
Results
The analyses revealed that HC sizes and growth rates were not significantly larger in toddlers with autism even when stratifying the autism group based on verbal capabilities at the time of diagnosis. In addition, there were no significant correlations between ADOS scores at the time of diagnosis and HC at any time-point during the first 2 years of life.
Conclusions
These negative results add to accumulating evidence, which suggest that brain volume is not necessarily larger in toddlers who develop autism. We believe that conflicting results reported in other studies are due to small sample sizes, use of misleading population norms, changes in the clinical definition of autism over time, and/or inclusion of individuals with syndromic autism. While abnormally large brains may be evident in some individuals with autism and more clearly visible in MRI scans, converging evidence from this and other studies suggests that enlarged HC is not a common etiology of the entire autism population. Early HC measures, therefore, offer very limited clinical utility for assessment of autism risk in the general population
The Magnitude of Trial-By-Trial Neural Variability Is Reproducible over Time and across Tasks in Humans
No full textAbstractNumerous studies have shown that neural activity in sensory cortices is remarkably variable over time and across trials even when subjects are presented with an identical repeating stimulus or task. This trial-by-trial neural variability is relatively large in the prestimulus period and considerably smaller (quenched) following stimulus presentation. Previous studies have suggested that the magnitude of neural variability affects behavior such that perceptual performance is better on trials and in individuals where variability quenching is larger. To what degree are neural variability magnitudes of individual subjects flexible or static? Here, we used EEG recordings from adult humans to demonstrate that neural variability magnitudes in visual cortex are remarkably consistent across different tasks and recording sessions. While magnitudes of neural variability differed dramatically across individual subjects, they were surprisingly stable across four tasks with different stimuli, temporal structures, and attentional/cognitive demands as well as across experimental sessions separated by one year. These experiments reveal that, in adults, neural variability magnitudes are mostly solidified individual characteristics that change little with task or time, and are likely to predispose individual subjects to exhibit distinct behavioral capabilities.</jats:p
Perceptual thresholds are better in individuals with lower trial-by-trial neural variability
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