David Alexander

Nationality

Australian

Function

Researcher

Function Description

My central interest is in the relationship between spatio-temporal dynamics of the cortex and topographic maps in the cortex. These interests combine into three broad topics of (1) analysis of global EEG/MEG, (2) contextual modulation in the primary visual cortex and (3) generalization of learning.

I am engaged in analysis of global spatio-temporal waves in EEG/MEG. Whole scalp measurements are used to identify epochs of wave activity. These spatio-temporal waves are hypothesized to be involved in the coordination of cognition at the global scale of the cortex. The wave activity can be elicited under conditions that elicit event-related potentials such as the P2 and P3. The frequency and latency of the wave activity is consistent with a relationship to these event-related potentials. The study of event-related wave activity has been applied to various clinical disorders.

I am interested in contextual modulation in the primary visual cortex. Review of measurements of contextual modulation indicates that distal stimulus features can increase activity in a neuron even where that distal feature lies far from the receptive field of the neuron. When stimulus features are converted into cortical coordinates, contextual modulation can be shown to occur over distances of several centimetres in the primary visual cortex. I am currently researching how these contextual features may be mapped at a local scale (~400 µm) into the primary visual cortex.

Generalization from limited information is a powerful cognitive process, whether it involves largely automatic processes like generalization of perceptual patterns or higher level cognition like generalization of grammatical rules. For example, a square is immediately recognized as a square regardless of variation in its size, position, velocity, colour or the context in which it is embedded--a square window for example. In the present research I am exploring two aspects of how the cortex generalizes from limited information. The first aspect of the research models processes by which topographic maps in the cortex store transient patterns of activity in such a way that future perceptual variation can be anticipated. The second aspect of the research models processes by which topographic maps in the cortex can be learned such that they have the property that they allow generalization from limited information.

Projects

Generalization of Learning: David Alexander, Bas van Oostveen
Spatio-temporal Waves in Global Cortex: David Alexander
Contextual Modulation in the Primary Visual Cortex: David Alexander

Staff

David Alexander

Nationality

Function

Function Description

Projects

CV

Publications

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