Topographical map for quantities – Indeed? Commentary on Harvey et al 2013, 2017

In an fMRI passive viewing task made in a 7T scanner, Harvey et al (2013) asked adult participants to passively view dots on a screen and reported a topographical map of quantities in the human intraparietal sulcus (IPS), suggesting that quantities are directly perceived, and their cortical organization may be fundamental to human abilities in mathematics. This paper, which was published in Science, got lots of attention and was cited 469 times since. In a later Neuroimage paper (2017), the authors analyzed the response to the visual features of the stimuli and suggested that the neural responses do not reflect the processing of visual features. I raise several reasons to restrict these conclusions. (1) the study design emphasized quantity over continuous magnitudes such as density and area. This may be problematic since neural activity can be influenced by attending to a specific dimension. (2) Poor control over continuous magnitudes. (3) The conclusions should be restricted to small quantities. (4) Task context influences neural activity, and (5) When the analysis is restricted to a specific cortical area, the conclusion should be restricted as well.