Terry Pratchett (1948–2015), fantasy writer, affected in later life by posterior cortical atrophy (PCA), visual variant of Alzheimer's disease, claimed that “Stories of imagination tend to upset those without one.” While, engagement into imaginary worlds is a very rewarding experience for individuals with high openness to experience and novelty preference as emphasized by Dubourg and Baumard (D&B) and the experience of imagery may be regarded on a continuum from hyperphantasia to aphantasia. Hyperphantasia is related to creativity (Zeman et al., Reference Zeman, Milton, Della Sala, Dewar, Frayling, Gaddum and Winlove2020). Aphantasia, a clinical syndrome consisting of the inability to create mental “images” is sometimes associated with face recognition deficits and autism spectrum traits (Milton et al., Reference Milton, Fulford, Dance, Gaddum, Heuerman-Williamson, Jones and Zeman2021). Voluntary mental imagery is a complex top-down process initiated in the frontal cortex that triggers stored information/memory traces from posterior brain areas (Goodale & Milner, Reference Goodale and Milner1992; Goodale & Westwood, Reference Goodale and Westwood2004). We argue that change in preference for imaginary worlds may be related to cognitive or personality changes in the course of a neurodegenerative disease. The discussion on the engagement into the imaginary worlds seems to have clinical implications for dementia, while till now aphantasia has been described mainly in focal brain damage (Zeman et al., Reference Zeman, Della Sala, Torrens, Gountouna, McGonigle and Logie2010) or as a congenital disorder (Zeman, Dewar, & Della Sala, Reference Zeman, Dewar and Della Sala2015). We hypothesize that change in preference for imaginary worlds could be a clinically relevant phenomenon, potentially helpful in neurological diagnosis or patient monitoring.

Although Galton noted high variability of mental imagery in 1880 (Galton, Reference Galton1880), the first case of impaired imagery was described from neurological perspective by Charcot and Bernard in 1883 (Zago et al., Reference Zago, Allegri, Cristoffanini, Ferrucci, Porta and Priori2011). Monsieur X complained that he suddenly lost mental imagery, not only was he unable to form mental images but also noticed its emotional implications (see Young & Wal, Reference Young, Wal, Code, Wallesch, Joannette and Roch Lecours1996).

D&B discuss individual differences in novelty preferences and interest in imaginary worlds. Could these individual differences be relevant also for neuropsychological characteristics of dementia syndromes? Reading/watching fictions or playing computer games including imaginary worlds engages a variety of cognitive functions. As D&B noted discussing the example of No Man's Sky (2016) the preference for a complex (but not too complex) imaginary world may be associated with human cognitive limitations. Are progressive neurodegenerative disorders are also associated with reduced preference for imaginary worlds due to cognitive deficits? While reading a fictional narrative healthy individuals use visualizing (Brosch, Reference Brosch2018). Although reading aloud may be, except for PCA, relatively well preserved until late in the course of dementia, people with dementia usually read less or stop reading fiction novels because of the failure to concentrate and/or track the plot (Clement, Belleville, & Gauthier, Reference Clément, Belleville and Gauthier2008).

Focal cognitive deficits, such as acalculia (Mendez, Moheb, Desarzant, & Teng, Reference Mendez, Moheb, Desarzant and Teng2018) or prosopagnosia (Evans, Heggs, Antoun, & Hodges, Reference Evans, Heggs, Antoun and Hodges1995), may be a harbinger of dementia. Scopus search [TITLE-ABS-KEY (aphantasia) AND TITLE-ABS-KEY (dementia OR Alzheimer OR progressive OR neurodegenerative)] conducted on September 24, 2021 failed to identify any link between aphantasia and dementia. We hypothesize that four different types of progressive aphantasia could be a harbinger of dementia:

We assume that apperceptive and associative aphantasia (named after apperceptive and associative agnosia and prosopagnosia) would be related to posterior brain dysfunction and could be a harbinger of PCA. On the contrary, ideational (inability to visualize a sequence of scenes) and adynamic aphantasia (inability to initiate the mental image) would be associated with frontal/fronto-striatal dysfunction and could be an early symptom of frontotemporal dementia, progressive supranuclear palsy (PSP), or Huntington's disease (HD).

Although, literature lacks in studies providing direct support for our hypotheses, there is scarce data somewhat consistent with our predictions. In PCA visual imagery deficits lead to poor scene construction (Ramanan et al., Reference Ramanan, Alaeddin, Goldberg, Strikwerda-Brown, Hodges and Irish2018), which would correspond to associative aphantasia. Spatial integration of the scene engages not only parietal areas, but also the right hippocampus, and it is affected also in frontotemporal dementia (Wilson et al, Reference Wilson, Ramanan, Roquet, Goldberg, Hodges, Piguet and Irish2020).

In PSP generation (Robinson, Spooner, & Harrison, Reference Robinson, Spooner and Harrison2015) and/or sequencing of novel thought (Robinson, Reference Robinson2013) may be significantly deficient. The former could be associated with adynamic aphantasia, while the latter with ideational aphantasia. Both seem closely related to executive dysfunction. It is open to debate if social cognition and decision-making deficits in the early phases of HD (Mason, Schaepers, & Barker, Reference Mason, Schaepers and Barker2021) could also be related to some extent to aphantasia, as efficient decision-making may involve imagining future outcome (Nanay, Reference Nanay2016).

On the other hand, D&B emphasize the relationship between engagement into imaginary worlds and novelty preference as well as openness to experience. Engagement into imaginary world may be a potential reward source for individuals with high novelty preference. Parkinson's disease (PD) has been associated with low novelty seeking (Cerasa, Reference Cerasa2018) and low openness to experience (Santangelo et al., Reference Santangelo, Garramone, Baiano, D'Iorio, Piscopo, Raimo and Vitale2018). Of note, dopaminergic treatment in PD may promote creativity (Garcia-Ruiz, Martinez Castrillo, & Desojo, Reference Garcia-Ruiz, Martinez Castrillo and Desojo2019), as striatal dopamine is related to flexible creative processes and prefrontal dopamine to persistence-driven creativity (Boot, Baas, van Gaal, Cools, & De Dreu, Reference Boot, Baas, van Gaal, Cools and De Dreu2017). However, dopaminergic treatment may also lead to impulse control disorders (ICD). Could dopamine replacement therapy influence aphantasia? Could it provoke a sudden interest in the imaginary worlds?

Aphantasia in the field of neurodegenerative disease remains largely an undiscovered land. Openness to experience, as a personality trait, may be a protective factor against cognitive decline (Rodriguez et al., Reference Rodriguez, Albanese, Pegna, Toma, Ackermann, Tombeur and Giannakopoulos2016) as is cognitive activity (including reading) (Floud et al., Reference Floud, Balkwill, Sweetland, Brown, Reus, Hofman and Beral2021). If openness to experience is associated with a preference for imaginary worlds, does behavioral engagement into imaginary worlds promote cognitive health in later life? Should we incorporate questions about literary preferences to interviews at dementia clinics? Also, as playing computer games compulsively may be a symptom of ICD in PD, should we study patients' game preferences in the future? Would we identify individuals with high risk of developing ICD among lovers of imaginary worlds? Is mesolimbic dopaminergic pathway activity, implicated in PD, also associated with preference for imaginary worlds?