The article by Jeffery et al. reviews the literature on spatial cognition relative to three-dimensional environments, which is an area vastly less investigated than are two-dimensional (or planar) environments. The authors have concluded that three-dimensional spaces are represented in a quasi-planar fashion. Here we add to the discussion by examining the role played by developmental vision on the structure and functioning of brain areas involved in spatial cognition, and the results of studies investigating the role of spatial learning on three-dimensional space representation.

The role of developmental vision in spatial representation has been reported by numerous studies on humans (Pasqualotto et al. Reference Pasqualotto, Spiller, Jansari and Proulx2013; Postma et al. Reference Postma, Zuidhoek, Noordzij and Kappers2007; Röder et al. Reference Röder, Kusmierek, Spence and Schicke2007; Vecchi et al. Reference Vecchi, Tinti and Cornoldi2004; see Pasqualotto & Proulx [Reference Pasqualotto and Proulx2012] for a review) and animals (Buhot et al. Reference Buhot, Dubayle, Malleret, Javerzat and Segu2001; Hyvärinen et al. Reference Hyvärinen, Hyvärinen and Linnankoski1981; Paz-Villagrán et al. Reference Paz-Villagrán, Lenck-Santini, Save and Poucet2002). Yet, the role played by vision on the establishment of the quasi-planar representation of three-dimensional spaces has not been investigated. This represents a broad avenue for future studies. Due to the crucial role played by vision in spatial cognition (e.g., Frankenstein et al. Reference Frankenstein, Mohler, Bülthoff and Meilinger2012) and vertical spatial perception (Ooi et al. Reference Ooi, Wu and He2001; Sinai et al. Reference Sinai, Ooi and He1998), it is conceivable that visual experience has an effect on both horizontal and vertical spatial representation, and, therefore, the results discussed by Jeffery et al. may be driven by experience with the visual world. In other words, blind individuals, especially if congenitally blind, may not exhibit quasi-planar spatial representation of three-dimensional environments. This hypothesis may be well supported by studies reporting the role of blindness in the functioning of hippocampal cells in rodents (Hill & Best Reference Hill and Best1981; Larsen et al. Reference Larsen, Luu, Burns and Krubitzer2009; Paz-Villagrán et al. Reference Paz-Villagrán, Lenck-Santini, Save and Poucet2002; Poucet et al. Reference Poucet, Save and Lenck-Santini2000) and on hippocampal structure and activation in humans (Chebat et al. Reference Chebat, Chen, Schneider, Ptito, Kupers and Ptito2007; Deutschländer et al. Reference Deutschländer, Stephan, Hüfner, Wagner, Wiesmann, Strupp, Brandt and Jahn2009; Kupers et al. Reference Kupers, Chebat, Madsen, Paulson and Ptito2010; Leporé et al. Reference Leporé, Shi, Lepore, Fortin, Voss, Chou, Lord, Lassonde, Dinov, Toga and Thompson2009).

The study by Passini and Proulx (Reference Passini and Proulx1988) represents a rare investigation on the spatial representation of a three-dimensional environment by congenitally blind and sighted participants. They found that overall, blind participants took more decisions at crucial points of the environment than did sighted ones. These points included intersections, stairs, open spaces, etc. Crucially, vertical structures of the environment did not receive more attention than horizontal ones.

In a recent article, Thibault et al. (Reference Thibault, Pasqualotto, Vidal, Droulez and Berthoz2013) investigated the effect of spatial learning on memory of a virtual three-dimensional building. The same building was learned either through “planar” or “columnar” exploration. It was followed by a spatial memory task where participants re-experienced a segment of the exploratory route. The results showed that the group of participants who underwent planar exploration had superior spatial memory performance. Yet, Thibault et al. also found that for both groups, the spatial memory task was better performed when participants re-experienced the same segments as during the exploratory phase (i.e., congruency effect). This suggests that, according to the learning type, participants could store the three-dimensional building in quasi-planar and quasi-columnar fashions.

These results suggest that quasi-planar spatial representation may be the result of quasi-planar spatial exploration. In other words, by using virtual reality (Lahav & Mioduser Reference Lahav and Mioduser2008; Péruch et al. Reference Péruch, Vercher and Gauthier1995) or sensory substitution devices (Kupers et al. Reference Kupers, Chebat, Madsen, Paulson and Ptito2010; Proulx et al. Reference Proulx, Stoerig, Ludowig and Knoll2008; Reference Proulx, Brown, Pasqualotto and Meijer2012), three-dimensional environments could be explored and stored according to any fashion (i.e., planar or columnar). These devices would overcome the energetic cost associated with vertical exploration (Butler et al. Reference Butler, Acquino, Hissong and Scott1993; Hölscher et al. Reference Hölscher, Meilinger, Vrachliotis, Brösamle and Knauff2006). Finally, the ability of the brain to learn and carry out spatial memory tasks in non-planar fashion is supported by studies in “gravity-less” three-dimensional virtual mazes (Vidal et al. Reference Vidal, Lipshits, McIntyre and Berthoz2003; Reference Vidal, Amorim and Berthoz2004). Therefore, we advocate that future research should address the role played by visual experience and spatial learning on spatial representation of three-dimensional environments.