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Professor Horace Barlow

Professor Horace Barlow

Research Worker (retired)

Office Phone: +44 (0) 1223 333813

Research Interests

Almost all my research has been in the field of vision. My main aim has been to understand the visual system at the level of single neurons and their interactions, a level that may hold the key to a quantitative understanding of the useful work our brains do for us. This work can be measured by estimating the statistical efficiency with which a task can be performed, and the same measure can be applied both to responses of single neurons, and to behavioural responses of a whole animal or human observer. It seems to be turning out that both single neurons, and intact brains, can perform carefully selected tasks quite close to the statistical limit imposed by a known amount of noise deliberately added to the input by the experimenter. This fact shows that brains are not incurably noisy, and it should allow us to find out how our brains track down the symmetries and suspicious coincidences in our environment, tasks that are required for intelligent cognitive judgements.

I'm currently interested in testing a hypothesis about the role of motion blur in helping us to determine the direction of motion of moving images. Motion blur results from the failure of the photoreceptors to follow the rapid fluctuations of intensity that occur when an image moves, and it causes a severe loss of acuity in the direction of motion, even when the velocity is only a few degrees/sec. This is shown at top left by the 2-D spatial frequency filter calculated for motion at 2 deg/sec. Our hypothesis is that the static patterns shown below (called Glass patterns after their discoverer) mimic the patterns of attenuation of high spatial frequencies that occur from the patterns of motion caused by optic flow, which are the image movements that occur when an observer moves through a fixed environment. A paper (with Bruno Olshausen) describing the hypothesis and some supporting observations is available at the Journal of Vision.

Key Publications

Barlow HB, (2013), Linking minds and brains, Vis Neurosci, 30(5-6):207-17

Barlow HB, Berry DL, (2010), Cross- and auto-correlation in early vision, Proceedings of the Royal Society, 278 (1714):2069-75

Barlow HB, (2009), Grandmother Cells, Symmetry, and Invariance: How the Term Arose and What the Facts Suggest, in The Cognitive Neurosciences, MIT Press, Cambridge, Mass, Ch21: 309-320

Above: This figure shows the extra attenuation at all orientations and spatial frequencies caused by 2 deg/sec motion of an image downward and to the right. It was calculated from measurements of Koenderinck and van Doorn (1979) made using counterphase flickering gratings. The colours crossed by the solid line show the attenuations at different frequencies for spatial frequency components modulated in the direction of motion. The red segments show the lack of attenuation at all spatial frequencies for modulation directions orthogonal to the motion, but the segments are narrow and should yield accurate information about the direction of the orthogonal. The dotted line is at 84° to the direction of motion, 6° from the orthogonal, and there is already considerable attenuation of high spatial frequencie