abstract Denes Szucs

Denes Szucs (University of Cambridge, Department of Experimental Psychology, Centre for Neuroscience in Education)

Behavioral and event-related brain potential investigations of normal and impaired numerical cognition in adults and children

I will provide an overview of our laboratory's recent behavioral and electro-magnetic investigations of normal and impaired numerical cognition in adults and children. The main neuroimaging methodology used is event-related brain potentials (ERPs) which offer a virtually unlimited time resolution of brain activity on-going even before behavioural responses happen. By exploiting the strengths of the EEG methodology several studies focused on detecting the speed of automatic access to magnitude information represented by digits in Numerical Stroop tasks. First, we demonstrated that the activation speed of numerical information was similar in Grade 3 and 5 children and adults even when numerical information was not task relevant. Further, we demonstrated that the developmental pathways of interference and distance effects were dissociated. Interference effects dominated ERPs in Grade 1, while the numerical distance effect dominated in Grade 3. The data suggest a shift in accessing number information from control functions to increased automaticity from Grade 1 to Grade 3. This data is in line with our further experiments focused on executive functioning. Behavioral experiments extended ERP findings by studying the automatic access to spatial-numerical information associated with digits in Grades 1-3 and by studying automatic access to magnitudes represented by fractions. Overall, results consistently show increased automaticity with magnitude and spatial processing of numbers in normal populations. I will also describe adult experiments using violation of expectancy paradigms in an attempt to dissociate semantic and syntactic processing of multi-digit numbers. These paradigms may open up investigations of more complex numerical knowledge in children. In the final part I will describe our ERP results in developmental dyscalculia and our initial results from a large scale investigation of dyscalculia in the UK.