About Dr Alex Holcombe
In my lab, we're curious about temporal aspects of human visual information processing - how quickly do different cortical modules and stages process information, and how are they coordinated in time? We use behavioral experiments, using animated displays like those at http://www.psych.usyd.edu.au/staff/alexh/, to compare speed limits for different features and the dynamics of how these features are bound into a coherent percept. One coordination problem occurs because when an object moves across the visual field, it stimulates different populations of neurons in early visual cortex, so we're testing how the signals from different areas are combined by later stages of the brain. Overall, fast processes somehow work together with others that are very sluggish in order to yield conscious perception. Recently, we've begun experiments to see how these limitations constrain our attempts to interact with moving objects.
Our lab has several experimental paradigms set up to reveal the hidden workings of human visual perception. Most experiments are directed at temporal aspects of human information processing. The brain takes time to process visual information, meaning that in many cases our brains are living in the past and having to predict events just to be less far behind the present. We have recently found evidence that the lag in perception increases when people split their attention among multiple objects. This lag, although usually only a fraction of a second, can be very costly when one is attempting to intercept or avoid moving objects. Current experiments investigate the mechanism that updates our representation of object features and position. An aspect of feature processing important for understanding neural computation is the additional issue of binding the multiple features of an object. The various features of an object, such as its shape, color, and sound are processed by distinct brain areas but must be represented as belonging together to create our perception of a unified world. Experiments underway are revealing the way these features are paired and updated asynchronously. Our laboratory provides a number of ways for a motivated PhD student to be on the forefront of international research in human visual perception. The presence of four other labs in the building conducting internationally renowned research in related fields provides a stimulating environment where students are exposed to a wealth of knowledge in the area and a broad education in current techniques. The creative student can capitalize on these resources to make their own mark in the understanding of human information processing. Department support allows doctoral students to present their research at domestic and international conferences in the field.
Work by Dr. Holcombe and his collaborators has been published in some of the most prestigious outlets for scientific work, including Nature and Nature Neuroscience. Dr. Holcombe is regularly asked by such journals to evaluate others' work as well. A full list of his publications can be found at http://www.psych.usyd.edu.au/staff/alexh/research/cv.html
- Holcombe, A.O. & Cavanagh, P. (2008). Independent, synchronous access to color and motion features. Cognition.
- Howard, C.J. & Holcombe, A. O. (2008). Tracking the changing features of multiple objects: Progressively poorer precision and progressively greater lag. Vision Research
- Holcombe, A. O. & Judson, J. (2007). Visual binding of English and Chinese word parts is limited to low temporal frequencies. Perception, 36(1):49-74.
- Clifford, C.W.G., Holcombe, A.O., & Pearson, J. (2004). Rapid global form binding with loss of associated colors. Journal of Vision, 4, 1090-1101.
- Kline, K., Holcombe, A. O., & Eagleman, D. M. (2004). Illusory motion reversal is not caused by perceptual snapshots of the visual field. Vision Research, 44(23), 2653-2658.
- Huang, L., Holcombe, A.O., & Pashler, H. (2004). Repetition priming in visual search: Episodic memory, not feature priming. Memory & Cognition, 32(1), 12-20.
- Holcombe, A.O., & Cavanagh, P. (2001). Early binding of feature pairs for visual perception. Nature Neuroscience, 4(2), 127-128.
- Blaser, E., Pylyshyn, Z., & Holcombe, A.O. (2000). Tracking an object through feature-space. Nature, 408, pp.196-199.
- Kubovy, M. Holcombe, A.O., & Wagemans, J. (1998). On the lawfulness of grouping by proximity. Cognitive Psychology, 35(1), 71-98.
- Cavanagh, P., Holcombe, A.O., & Chou, W-L. (in press) Mobile computation: Spatiotemporal integration of the properties of objects in motion. Journal of Vision.