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Macquarie Centre for Cognitive Science

Current MEG Research Projects

Acquiring expertise in the mental manipulation of visual images: Effects on brain and behaviour

Blake Johnson

pictures of three dimensional objects with rotational transformationsShepard and Metzler's (1971) mental rotation task has provided the primary experimental tool for investigating spatial cognition. It measures the time taken by participants to classify pictures of three dimensional objects as either matching or mismatching under a rotational transformation (e.g., Figure 1). Response time (RT) increases monotonically and often linearly with angle of rotation, suggesting that participants mentally rotate one image into alignment with the other, a conclusion that has been strongly supported by subsequent behavioural investigations. However, after practice with the same set of stimuli, RT not only decreases but can also becomes insensitive to rotation angle, but , this effect does not generalize to unpractised stimuli, suggesting that expertise involves a functional reorganization that allows the task to be performed directly via perceptual categorization, rather than improvement in a domain general skill. This project will integrate Cognitive and Brain Science approaches to the development of expertise in spatial cognition.

MEG investigation of sentence context effects on spoken word processing

Jon Brock and Blake Johnson

Our goal is to use MEG to specify the nature of cognitive integration deficits associated with autism and to directly investigate the link with neural connectivity. In the first instance, we plan to focus on language comprehension -a process that necessarily involves the integration of multiple sources of information.The proposed study will develop an MEG paradigm with typical adults to be used in a future study of individuals with autism and language impairment and to support future grant proposals. Pilot testing will (a) confirm that predicted effects are found; (b) allow clear predictions to be made for studies of autism; (c) determine the minimum number of trials needed to obtain reliable effects; (d) identify those items that reliably produce the expected effects and hence minimize the number of trials needed in studies of autism.

How children process Negative polarity items

Stephen Crain, Graciela Tesan and Rosalind Thornton

language sources on MRIThe aim of this study is to investigate children's brain responses to the word any in two conditions, first where any is permitted, as in Nobody ate any fruit, and second where it is not permitted, as in Everybody ate *any fruit. As these examples indicate, the word any can only appear in the certain linguistic environments, such as following nobody. When it follows other linguistic expressions, such as everybody, it is anomalous. We are conducting an auditory experiment, designed to measure how the brain responds to such anomalies without directing subject's attention to the anomalies. The study uses Magnetoencephalography (MEG) to measure the neural indicators of the on-line lexical access of the word any in two conditions, following nobody/before and following everybody/after. In analysing the data, we are seeking to identify the magnetic equivalent of a component that has been associated with integration of anomalies involving real-world knowledge in the ERP literature: the N400, elicited in response to sentences like I buttered the bread with socks. The experimental hypothesis is that the detection of the semantic anomaly upon lexical access in should precede the integration of real-world knowledge associated with the N400 component in the ERP literature.