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Articles by Nicholas A. Badcock in JoVE
JoVE Neuroscience
Avaliação da lateralização cerebral em crianças usando Funcional ultra-som Doppler transcraniano (fTCD)
Department of Experimental Psychology, University of Oxford
Funcional Doppler transcraniano (fTCD) é uma técnica de ultra-som simples e não invasivo, que pode ser usado para avaliar a lateralização das funções cognitivas, especialmente a linguagem, e é adequado para uso em crianças.
Other articles by Nicholas A. Badcock on PubMed
No Differential Attentional Blink in Dyslexia After Controlling for Baseline Sensitivity
Previous research has associated a prolonged attentional blink (AB) with adult dyslexia [Hari, R., Valta, M., & Uutela, K. (1999). Prolonged attentional dwell time in dyslexic adults. Neuroscience Letters, 271, 202-204]. The AB represents a limitation in temporal information processing, estimated as the time interval between two targets necessary for accurate recall (e.g., [Raymond, J. E., Shapiro, K. L., & Arnell, K. M. (1992). Temporary suppression of visual processing in an RSVP task: An attentional blink? Journal of Experimental Psychology: Human Perception and Performance, 18, 849-860]). Utilizing single- and dual-target procedures, this investigation extended upon previous research. When controlling for baseline sensitivity as estimated in the dual-target condition, there was no significant difference between dyslexic and control performance. Finding no evidence of a single-target task difference or prolonged AB effect in dyslexia, it is suggested that baseline sensitivity differences relate to difficulties with task demands in dyslexic readers.
Dyslexia and Practice in the Attentional Blink: Evidence of Slower Task Learning in Dyslexia
In this paper we provide an extension to our previous investigation into dyslexia and the attentional blink (AB) (Badcock et al., 2008). The AB is a phenomenon of temporal attention whereby there is a performance cost in reporting a second target when it appears within 500msec of a first target. We examined performance differences between the first and second 90 trials in a single AB session in a group of adult readers as well as in 6 blocks of 30 trials for T1 only. Overall, there was a significant improvement across the session but most critically, this improvement was greater in magnitude and slower in the phonological dyslexic observers than in control observers. Therefore, group differences were related to rate of improvement. In line with a recent review of the literature, it is suggested that the overall performance difference between the groups relates to general performance factors and not the AB per se. Whether extended practice would entirely attenuate the group difference remains to be seen but it is suggested that the general performance difference relates to development of successful coordination of visual and temporal uncertainties in the distracter and target stimuli.
Where Were Those Rabbits? A New Paradigm to Determine Cerebral Lateralisation of Visuospatial Memory Function in Children
In the majority of people, functional differences are observed between the two cerebral hemispheres: language production is typically subserved by the left hemisphere and visuospatial skills by the right hemisphere. The development of this division of labour is not well understood and lateralisation of visuospatial function has received little attention in children. In this study we devised a child-friendly version of a paradigm to assess lateralisation of visuospatial memory using functional transcranial Doppler ultrasound (fTCD). In a group of 24 adults we found this child-friendly version gave similar results to the original version of the task. In addition, fourteen children aged 6-8 years successfully completed the child-friendly fTCD task, showing a negative lateralisation index, indicating right hemispheric specialisation at the group level. Additionally, we assessed effects of task accuracy and reaction time on the lateralisation index. No effects were found, at the group level or at the level of single trials, in either the adult or the child group. We conclude that this new task reliably assesses lateralisation of visuospatial memory function in children as young as 6 years of age, using fTCD. As such, it holds promise for investigating development of lateralisation of visuospatial function in typically and atypically developing children.
Co-localisation of Abnormal Brain Structure and Function in Specific Language Impairment
We assessed the relationship between brain structure and function in 10 individuals with specific language impairment (SLI), compared to six unaffected siblings, and 16 unrelated control participants with typical language. Voxel-based morphometry indicated that grey matter in the SLI group, relative to controls, was increased in the left inferior frontal cortex and decreased in the right caudate nucleus and superior temporal cortex bilaterally. The unaffected siblings also showed reduced grey matter in the caudate nucleus relative to controls. In an auditory covert naming task, the SLI group showed reduced activation in the left inferior frontal cortex, right putamen, and in the superior temporal cortex bilaterally. Despite spatially coincident structural and functional abnormalities in frontal and temporal areas, the relationships between structure and function in these regions were different. These findings suggest multiple structural and functional abnormalities in SLI that are differently associated with receptive and expressive language processing.
Lateralised Visual Attention is Unrelated to Language Lateralisation, and Not Influenced by Task Difficulty - A Functional Transcranial Doppler Study
Historically, most theoretical accounts of hemispheric specialisation have proposed a single underlying factor that leads to left hemisphere language and right hemisphere visuospatial processing in the majority of people. More recently empirical evidence has started to challenge this view, suggesting lateralisation of language and visuospatial attention are independent. However, so far studies did not control for a possible confound, task difficulty. For this study, 20 healthy right-handed volunteers underwent functional laterality assessment using functional transcranial Doppler ultrasound (fTCD). We assessed laterality using both a word generation task and a novel variation of the visuospatial landmark task that can be adjusted along two dimensions of difficulty (temporal and spatial). The visuospatial laterality measures were highly intercorrelated and unaffected by task difficulty. Furthermore, there was no correlation between visuospatial and verbal lateralisation within individuals - neither qualitatively (in direction of lateralisation), nor quantitatively (in laterality index size). These results substantiate a growing body of evidence suggesting multiple independent biases leading to the hemispheric lateralisation of different cognitive domains, thus further questioning previously accepted models of laterality development and evolution.
DopOSCCI: A Functional Transcranial Doppler Ultrasonography Summary Suite for the Assessment of Cerebral Lateralization of Cognitive Function
We present a description of a new software package, 'dopOSCCI', which summarises data from experimental studies where functional transcranial Doppler ultrasonography (fTCD) is used to compare hemispheric rates of blood flow in order to assess lateralization of a cognitive process. The software provides a graphical user interface to summarise analogue and digital data collected using Multi-Dop Doppler Ultrasound devices (DWL Multidop T2: manufacturer, DWL Elektronische Systeme, Singen, Germany). The unique aspects of dopOSCCI allow multi-file processing, multi-event marker processing, behavioural and multi-session summaries, image file data visualization, and tab-delimited output files which includes split-half, single-trial summaries and data quality variables. The Matlab based software is available under the GNU GPL license and can be accessed online at https://databank.ora.ox.ac.uk/general/datasets/dopOSCCI, the Oxford University DataBank.
