Funding was provided by NINDS R01 NS069679, the Klingenstein Fund, the Rita Allen Foundation (R.M.B.), selleck compound NIGMS T32 GM07367-35 (A.R.), and the Max Planck Society (M.O.). “
“Time and space have such a close relationship in human perception that, according to Piaget, “time and space form an inseparable whole” (Piaget, 1927, p. 1). Temporal and spatial perceptions interfere with each other in both humans and monkeys (Casasanto and Boroditsky, 2008, Merritt et al., 2010 and Xuan

et al., 2007), saccadic eye movements compress magnitude judgments of both space and time (Morrone et al., 2005), and spatial manipulations such as prism adaptation cause misperceptions of time intervals (Magnani et al., 2011). These and other psychophysical interactions have led to the idea that the brain encodes magnitude in domain-general representations that include space and

time, as well as number, size, and speed (Gallistel and Gelman, 2000 and Walsh, 2003). According to this theory, some neural networks encode a greater or lesser quantity in the abstract, independent of metrics such as distance, duration, speed, numerosity, etc. Although some findings support an abstract neural representation of magnitude, such as the effect of cortical damage on both space and time perception (Basso et al., Antidiabetic Compound Library order 1996, Mitchell and Davis, 1987 and Zorzi et al., 2002), other results seem to contradict this idea. For example, some patients with lesions of different frontal and parietal areas have deficits in perceiving either numbers or durations, but not both (Cappelletti et al., 2009 and Cappelletti et al., 2011). Likewise, an asymmetry in the interference between temporal and spatial perceptions indicates separate, domain-specific mechanisms that interact with each other, rather than a common representation of magnitude (Casasanto et al., 2010). Neurons in the prefrontal (PF) and parietal cortex

encode space, time, and number (Nieder and Miller, 2004a, Nieder and Miller, 2004b, Tudusciuc and Nieder, 2007 and Tudusciuc and Nieder, 2009), including categories of these these metrics (Merchant et al., 2011), and several contemporary theories of the PF cortex have stressed domain generality and cross-domain information processing (Baars et al., 2003, Duncan, 2010 and Wilson et al., 2010). In two previous reports, we have described PF activity during the discrimination of relative durations (Genovesio et al., 2009) and relative distances (Genovesio et al., 2011) recorded in the same PF areas. These reports do not, however, address whether individual neurons in these areas encode relative magnitude in both cognitive domains. In order to search for a representation of common magnitude, we analyzed the activity of cells that were recorded in both of these discrimination tasks, along with a control task that we used to identify goal coding.