Research

 

My research seeks to understand the brain mechanisms of  visual perception. Click here for a list of my published papers.

I am currently working on aspects of motion perception with Dr Ignacio Serrano Pedraza of the Complutense University in Madrid and Dr Louise Delicato of the University of Sunderland. We are interested in the relationship between the spatial structure of briefly-presented moving patterns and human ability to discriminate their direction of motion. Our work builds on a two accepted facts about human visual processing:-

  • Information about direction and speed of motion of local features in the visual image is extracted at a very early stage of visual processing.
  • Information about motion is extracted separately for fine-scale features – such as the features in a face – and coarse-scale features – such as the head, of which the face is a part. Different mechanisms process the motion of fine features and coarse features.
The phenomena we are interested in are seen only with with very brief stimuli, lasting 20-30 msecs. Under these conditions it is impossible for observers to infer the direction of motion of an object by tracking changes in its position over time. We use random patterns containing both coarse-scale and fine scale features. We find that the perception of the motion of patterns containing moving fine-scale features is disturbed when there are coarse-scale features present.   If the coarse scale features are static, motion is seen in the opposite direction to that which is occurring. If the coarse-scale features move with the fine-scale features, it is harder, in the sense that a higher speed is necessary, to discriminate direction.
These results suggest that there is an antagonistic interaction between motion-sensing mechanisms that operate on fine features and those that operate on coarse features. We are developing experiments to test whether this interaction reflects the operation of a mechanism that combines coarse and fine motion signals to extract information about other aspects of the image. So far we have shown that the size, location and contrast of the pattern are critical.

 

 Posted by at 19:41