Upcoming sessions:

From 'social loafing' to academic assertiveness: Evaluating and developing students' group working skills
Dr. Marcia Worrel & Dr. Gina Pauli, Roehampton
POSTPONED

28 February 2013, 4pm, SCI 3.05
Dr. Paul Engelhardt, UEA

14 March 2013, 4pm, TPSC 1.1
Professor Essi Viding, UCL

21 March 2013, 4pm, TPSC 1.1
Birgit Larsson, UEA

25 April 2013, 4pm, TPSC 0.1 
Ellen Lynch, UEA

9 May 2013, 4pm, TPSC 0.1
Dr. Jacqueline Blissett, University of Birmingham.

16 May 2013, 4pm, EFB 1.01
Dr. Elizabeth Meins, Durham

23 May 2013, 4pm, EDU 0.112
Billy MacFarlane, UEA

30 May 2013, 4pm, TPSC 0.1
Dr. Piers Fleming, UEA

Previous sessions:

Why do things look as they do? The contribution of primary visual cortex to size perception
Dr. Irene Sperandio, UEA
17 January 2013, 4pm, TPSC 1.5

An afterimage looks larger when one fixates on a distant as opposed to a near surface. In conjunction with functional magnetic resonance imaging (fMRI), afterimages can be used to study the neural substrates of size-distance scaling. Using fMRI, we showed that the retinotopic activity in the primary visual cortex (V1) associated with viewing an afterimage is modulated by perceived size, even though the size of the retinal image remains constant.  This suggests that size constancy plays out in V1.  But is V1 always critical for size constancy? We carried out a size constancy study on patient M.C., who has large bilateral occipital lesions that include V1. We first measured M.C.'s ability to estimate the perceived size and distance of objects of different physical sizes positioned at varying distances. M.C.'s size and distance estimates were poorly scaled to the physical size and distance of the objects and were correlated instead with their retinal image size. In short, she showed no evidence of perceptual size constancy.  In contrast, when we asked M.C. to reach out and pick up objects positioned at different distances, her grip aperture scaled to the real width of the object at all viewing distances. Taken together, our results strongly suggest that the neural mechanisms that underlie size constancy for perception and action are distinct, and lend further support to the hypothesis that V1 plays an important role in conscious visual perception.