Jac Billington

Savant Memory for Digits in a Case of Synaesthesia and Asperger Syndrome is Related to Hyperactivity in the Lateral Prefrontal Cortex

Single case: DT is a savant with exceptional abilities in numerical memory and mathematical calculations. DT also has an elaborate form of synaesthesia for visually presented digits. Further more, DT also has Asperger syndrome (AS). We carried out two preliminary investigations to establish whether these conditions may contribute to his savant abilities. Neuroimaging: In an fMRI digit span study, DT showed hyperactivity in lateral prefrontal cortex when encoding digits, compared with controls. In addition, while controls showed raised lateral prefrontal activation in response to structured (compared to unstructured) sequences of digits, DTs neural activity did not differ between these two conditions. In addition, controls showed a significant performance advantage for structured, compared with unstructured sequences whereas no such pattern was found for DT. We suggest that this performance pattern reflects that DT focuses less on external mathematical structure, since for him all digit sequences have internal structure linked to his synaesthesia. Finally, DT did not activate extra-striate regions normally associated with synaesthesia, suggesting that he has an unusual and more abstract and conceptual form of synaesthesia. This appears to generate structured, highly-chunked content that enhances encoding of digits and aids both recall and calculation. Neuropsychology: People with AS preferentially attend to local features of stimuli. To test this in DT, we administered the Navon task. Relative to controls, DT was faster at finding a target at the local level, and was less distracted by interference from the global level. Discussion: The propensity to focus on local detail, in concert with a form of synaesthesia that provides structure to all digits, may account for DTs exceptional numerical memory and calculation ability. This neural and cognitive pattern needs to be tested in a series of similar cases, and with more constrained control groups, to confirm the significance of this association.

Neural processing of imminent collision in humans

Detecting a looming object and its imminent collision is imperative to survival. For most humans, it is a fundamental aspect of daily activities such as driving, road crossing and participating in sport, yet little is known about how the brain both detects and responds to such stimuli. Here we use functional magnetic resonance imaging to assess neural response to looming stimuli in comparison with receding stimuli and motion-controlled static stimuli. We demonstrate for the first time that, in the human, the superior colliculus and the pulvinar nucleus of the thalamus respond to looming in addition to cortical regions associated with motor preparation. We also implicate the anterior insula in making timing computations for collision events.

Systemizing influences attentional processes during the Navon task : An fMRI study

Systemizing ability exists on a spectrum, with a high systemizing style meaning proficiency in analysing the rules of a system, to predict how that system works. This study uses fMRI to investigate a spectrum of low to high systemizing, to assess whether individuals with a high systemizing style exhibit an attentional bias towards local details. This is the first study to test for the neural correlates of systemizing. Participants with a range of scores on the Systemizing Quotient (SQ) were given a version of the Navon task during fMRI, which elicits perceptual conflict between local and global levels of visual attention. SQ score was correlated with a focus on local detail in the behavioural study. During conditions eliciting perceptual conflict SQ score was associated with increased activation in the lateral prefrontal, parietal and extrastriate visual cortices. However, neural investigations did not imply a neural correlate of systemizing during local processing per se. Results are discussed in terms of a heightened ability to maintain an attentional set in those with a high systemizing cognitive style.

Mirror neuron activation in children with developmental coordination disorder: A functional MRI study.

The aim of this study was to reveal cortical areas that may contribute to the movement difficulties seen in children with Developmental Coordination Disorder (DCD). Specifically, we hypothesized that there may be a deficit in the mirror neuron system (MNS), a neural system that responds to both performed and observed actions. Using functional MRI, 14 boys with DCD ( x¯=10.08 years ± 1.31, range = 7.83 − 11.58 years) and 12 typically developing controls ( x¯=10.10 years ± 1.15, range = 8.33–12.00 years) were scanned observing, executing and imitating a finger sequencing task using their right hand. Cortical activations of mirror neuron regions, including posterior inferior frontal gyrus (IFG), ventral premotor cortex, anterior inferior parietal lobule and superior temporal sulcus were examined. Children with DCD had decreased cortical activation mirror neuron related regions, including the precentral gyrus and IFG, as well as in the posterior cingulate and precuneus complex when observing the sequencing task. Region of interest analysis revealed lower activation in the pars opercularis, a primary MNS region, during imitation in the DCD group compared to controls. These findings provide some preliminary evidence to support a possible MNS dysfunction in children with DCD.

Reduced relative volume in motor and attention regions in developmental coordination disorder: A voxel-based morphometry study

Developmental coordination disorder (DCD) is a prevalent childhood movement disorder, impacting the ability to perform movement skills at an age appropriate level. Although differences in grey matter (GM) volumes have been found in related developmental disorders, no such evidence has been linked with DCD to date. This cross‐sectional study assessed structural brain differences in children with and without DCD.

The involvement of the fronto-parietal brain network in oculomotor sequence learning using fMRI.

The basis of motor learning involves decomposing complete actions into a series of predictive individual components that form the whole. The present fMRI study investigated the areas of the human brain important for oculomotor short-term learning, by using a novel sequence learning paradigm that is equivalent in visual and temporal properties for both saccades and pursuit, enabling more direct comparisons between the oculomotor subsystems. In contrast with previous studies that have implemented a series of discrete ramps to observe predictive behaviour as evidence for learning, we presented a continuous sequence of interlinked components that better represents sequences of actions. We implemented both a classic univariate fMRI analysis, followed by a further multivariate pattern analysis (MVPA) within a priori regions of interest, to investigate oculomotor sequence learning in the brain and to determine whether these mechanisms overlap in pursuit and saccades as part of a higher order learning network. This study has uniquely identified an equivalent frontal-parietal network (dorsolateral prefrontal cortex, frontal eye fields and posterior parietal cortex) in both saccades and pursuit sequence learning. In addition, this is the first study to investigate oculomotor sequence learning during fMRI brain imaging, and makes significant contributions to understanding the role of the dorsal networks in motor learning.

Cortical responses to congruent and incongruent stereo cues for objects on a collision path with the observer

Abstract We explored the cortical responses to visual collision events that were presented via stimuli that changed in size (looming) or stereo-depth (binocular motion), or both. In particular we examined the differences in cortical response when the looming and binocular cues were congruent or incongruent in the collision information they provided. A stereoscopic goggle system was used within the fMRI environment and allowed us to present looming and disparity cues in isolation, or in congruent or incongruent combinations. Comparison across conditions showed that incongruent cues elicited additional activation in cortical areas know to both process error and locate objects in spatio-topic coordinates. Results are discussed in terms of cognitive and motor responses to seeing incongruent cues.

Mirror neuron system activation in children with developmental coordination disorder: A replication functional MRI study

BACKGROUND It has been hypothesised that abnormal functioning of the mirror neuron system (MNS) may lead to deficits in imitation and the internal representation of movement, potentially contributing to the motor impairments associated with developmental coordination disorder (DCD). AIMS Using fMRI, this study examined brain activation patterns in children with and without DCD on a finger adduction/abduction task during four MNS activation states: observation; motor imagery; execution; and imitation. METHODS AND PROCEDURES Nineteen boys (8.25-12.75 years) participated, including 10 children with DCD (≤16th percentile on MABC-2; no ADHD/ASD), and nine typically developing controls (≥25th percentile on MABC-2). OUTCOMES AND RESULTS Even though children with DCD displayed deficits behaviourally on imitation (Sensory Integration & Praxis Test Subtests) and motor imagery assessments prior to scanning, no differences in MNS activation were seen between the DCD and control groups at a neurological level, with both groups activating mirror regions effectively across conditions. Small clusters of decreased activation during imitation were identified in non-mirror regions in the DCD group, including the thalamus, caudate, and posterior cingulate - regions involved in motor planning and attentional processes. CONCLUSIONS AND IMPLICATIONS The results of this study do not provide support for the MNS dysfunction theory as a possible causal mechanism for DCD. Further research to explore attentional and motor planning processes and how they may interact at a network level may enhance our understanding of this complex disorder.

Reading and visual word recognition ability in semantic dementia is not predicted by semantic performance

ABSTRACT This paper describes longitudinal testing of two Semantic Dementia (SD) cases. It is common for patients with SD to present with deficits in reading aloud irregular words (i.e. surface dyslexia), and in lexical decision. Theorists from the connectionist tradition (e.g. Woollams et al., 2007) argue that in SD cases with concurrent surface dyslexia, the deterioration of irregular word reading and recognition performance is related to the extent of the deterioration of the semantic system. The Dual Route Cascaded model (DRC; Coltheart et al., 2001) makes no such prediction. We examined this issue using a battery of cognitive tests and two structural scans undertaken at different points in each cases time course. Across both cases, our behavioural testing found little evidence of a key putative link between semantic impairment and the decline of irregular word reading or lexical decision. In addition, our neuroimaging analyses suggested that it may be the emergence of atrophy to key neural regions both inside and outside the anterior temporal lobes that may best capture the emergence of impairments of irregular word reading, and implicated inferior temporal cortex in surface dyslexia. HIGHLIGHTSReading aloud of irregular words is not predicted by semantic performance in SD.Lexical decision accuracy is not predicted by semantic performance in SD.Surface dyslexia is not solely related to anterior temporal lobe damage.Inferior temporal cortex is implicated in irregular word reading deficits.

Cortical responses to congruent and incongruent stereo cues for objects on a collision path with the observer.

It has been established that binocular motion and visual looming are two primary sources of information for judging object motion. These cues are normally congruent when viewing motion in natural scenes. We explored the cortical responses to visual collision events that were presented via stimuli that changed in size (looming) or stereo-depth (binocular motion), or both. In particular we examined the differences in cortical response when the looming and binocular cues were congruent or incongruent in the collision information they provided. A stereoscopic goggle system was used within the fMRI environment and allowed us to present looming and disparity cues in isolation, or in congruent and incongruent combinations. Following univariate analysis it was found that incongruent looming and binocular motion cues elicited additional activation in cortical areas known to process error and locate objects in spatio-topic coordinates. Visual regions which showed high predictor values using multivariate pattern analysis concurred with research which has highlighted areas V1 - V3 and V6 in disparity processing. Results are discussed in terms of visual, cognitive and motor responses to seeing incongruent cues. Meeting abstract presented at VSS 2015.