The parietal cortex and the representation of time, space, number and other magnitudes

Abstract

The development of sub-disciplines within cognitive neuroscience follows common sense categories such as language, audition, action, memory, emotion and perception among others. There are also well-established research programmes into temporal perception, spatial perception and mathematical cognition that also reflect the subjective impression of how experience is constructed. There is of course no reason why the brain should respect these common sense, text book divisions and, here, we discuss the contention that generalized magnitude processing is a more accurate conceptual description of how the brain deals with information about time, space, number and other dimensions. The roots of the case for linking magnitudes are based on the use to which magnitude information is put (action), the way in which we learn about magnitudes (ontogeny), shared properties and locations of magnitude processing neurons, the effects of brain lesions and behavioural interference studies. Here, we assess this idea in the context of a theory of magnitude, which proposed common processing mechanisms of time, space, number and other dimensions.

Figure 1

(a) Left and (b) right hemisphere views of the human visual cortex showing activation sites reported in some functional magnetic resonance imaging studies of time (green dots), space (yellow dots), number (red dots) and size (blue dots) perceptions. These plots are based on Maquet et al. (1996), Schubotz et al. (2000), Rao et al. (2001), Macar et al. (2002), Ferrandez et al. (2003), Lewis & Miall (2003), Coull et al. (2004), Pouthas et al. (2005) and Bueti et al. (2008a,. Note the spread of numerical activations along the length of the intraparietal sulcus (IPS) in areas also associated with space, time, size and luminance (white dots). SFS, superior frontal sulcus.