A penny for your thoughts! patterns of fMRI activity reveal the content and the spatial topography of visual mental images

Abstract

Visual mental imagery is a complex process that may be influenced by the content of mental images. Neuropsychological evidence from patients with hemineglect suggests that in the imagery domain environments and objects may be represented separately and may be selectively affected by brain lesions. In the present study, we used functional magnetic resonance imaging (fMRI) to assess the possibility of neural segregation among mental images depicting parts of an object, of an environment (imagined from a first-person perspective), and of a geographical map, using both a mass univariate and a multivariate approach. Data show that different brain areas are involved in different types of mental images. Imagining an environment relies mainly on regions known to be involved in navigational skills, such as the retrosplenial complex and parahippocampal gyrus, whereas imagining a geographical map mainly requires activation of the left angular gyrus, known to be involved in the representation of categorical relations. Imagining a familiar object mainly requires activation of parietal areas involved in visual space analysis in both the imagery and the perceptual domain. We also found that the pattern of activity in most of these areas specifically codes for the spatial arrangement of the parts of the mental image. Our results clearly demonstrate a functional neural segregation for different contents of mental images and suggest that visuospatial information is coded by different patterns of activity in brain areas involved in visual mental imagery.

Where did you “left” Piazza del Popolo? At your “right” temporo-parietal junction

“…Importantly, the posterior angular gyrus is connected to the posterior parahippocampal cortex (Rushworth, Behrens, & Johansen-Berg, 2006), which houses place representations. This means that the detected area, besides direct involvement in first-person perspective change, is connected with relevant regions for navigation and retrieval from autobiographical memory (with its familiar spatial contexts), in agreement with the navigational deficits described in patients with representational neglect for places (Guariglia et al, 2013) and with the results of a recent fMRI study in healthy individuals (Boccia et al, 2015). Interestingly, the deficit of imposing an egocentric perspective to the mental image of the environment can provide an explanation for why patients often name landmarks that are in fact not visible from a given vantage point [see, for example, landmarks 4 and 5 in Fig.…”

“…Representational neglect for places is also more frequent and persistent in time than previously expected, maybe because it is rarely the object of dedicated rehabilitation or of informal reminders (Salvato, Sedda, & Bottini, 2014). Moreover, it is associated with navigational deficits in tasks resembling the water maze (Nico et al, 2008), so that a dualaccount of space representation within mental imagery has been proposed (Guariglia & Pizzamiglio, 2006), where topological versus non-topological visual images reflect representations in which it is possible to navigate or not, respectively (see also Boccia et al, 2015).…”

Perspective changing in WalCT and VR-WalCT: A gender difference study [WalCT – VR-WalCT: Gender differences]

“…Evidence from a neuroimaging study shows that neural correlates involved in real environments differed from those involved in geographical map representation, further stressing that primary and secondary learning could activate different cerebral areas. Specifically, Boccia et al (2015) found that imagining a familiar environment relies mainly on regions known to be involved in navigational skills, such as the retrosplenial complex and parahippocampal gyrus, whereas imagining a geographical map, even if the environment is well-known and familiar, mainly requires activation of the left angular gyrus, known to be involved in the representation of categorical relations. This result is also in line with previous data from the same authors (Boccia et al, 2014) who demonstrated in a behavioral study that a geographical map (i.e., the map of Italy) was mainly processed as a common object (i.e., a clock; through categorical spatial relations), whereas navigational images (i.e., the campus) were mainly processed as familiar navigational objects (through coordinate spatial relations).…”

“…Such a task involves locating a landmark or an object from an imagined perspective, projecting a self-to-object frame of reference (i.e., egocentric frame of reference) into a spatial position, orienting it accordingly, and then using it to compute the location of the target (Avraamides, Ioannidou, & Kyranidou, 2007). Several studies from the spatial cognition domain have analyzed how spatial information is acquired by primary, secondary learning and have tried to describe how navigational memory is organized (Boccia, Nemmi, & Guariglia, 2014;Boccia et al, 2015;Nemmi, Boccia, Piccardi, Galati, & Guariglia, 2013;Nori et al, 2015;Piccardi, Bianchini, Iasevoli, Giannone, & Guariglia, 2011b;Piccardi et al, 2011a). Perspective-taking, a popular task in spatial cognition research, is frequently used to investigate the organizational structure of spatial memory (e.g., Mou et al, 2004;Greenauer & Waller, 2010;Kelly & Avraamides, 2011).…”

A dedicated system for topographical working memory: evidence from domain-specific interference tests

“…In particular, the calcarine cortex, the lingual gyrus and the dorsolateral prefrontal cortex in the right hemisphere are selectively involved in learning within navigational space, while the middle occipital gyrus, the inferior temporal gyrus and lingual and fusiform gyrus in the left hemisphere are selectively involved in learning within reaching space (Nemmi et al 2013). Furthermore, Boccia et al (2014a) demonstrated that neural correlates underlying geographical knowledge are different from those underlying familiar environments. This finding is also supported by a behavioural study, suggesting a subdivision between graphical representations (i.e.…”