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Belén María Montabes de la Cruz, Clement Abbatecola, Petra Vetter, Johanna Bergmann, Lucy Petro, Lars Muckli; Investigating sound content in the early visual cortex of aphantasia participants. Invest. Ophthalmol. Vis. Sci. 2021;62(8):624.
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Sound content can be decoded from brain activity patterns in the early visual cortex of blindfolded (Vetter et al. 2014) and congenitally blind (Vetter et al., 2020) participants, especially in the periphery. What is the role of visual imagery in this effect? We explored this question by replicating Vetter et al.’s (2014) experimental design on a sample of aphantasic individuals who experience no visual imagery.
We controlled 5 self-reported aphantasics (4 females, Mage=34, SD=15.65) with the voluntary visual imagery questionnaire (VVIQ; Marks, 1973) and for involuntary imagery with the spontaneous use of imagery scale (SUIS; Kosslyn et al., 1998). We also used a behavioural test assessing the degree to which imagery can prime a binocular rivalry display (Bergmann et al., preprint).In a 3T fMRI experiment we presented our blindfolded participants with 3 natural sounds in a block design. We functionally localised auditory (positive control) and motor areas (negative control), early visual areas (V1, V2 and V3) and their respective eccentricities (fovea, periphery, far periphery). We fed each area’s Z-normalised beta weights signal into a linear support vector machine classification algorithm (LIBSVM) contrasting auditory scenes. We assessed the statistical significance of our classification with a permutation test.
Our participants scored low on the VVIQ (Mean=19.8, SD=1.92), SUIS (Mean=19.4; SD=3.85) and had close to chance priming scores (Mean=0.54, SD=0.07).Our positive (p<0.001) and negative (p>0.05) controls performed as expected.Two participants had significant classification accuracies in visual areas. However, at the group level our permutation analysis rendered non-significant accuracies in all retinotopic areas (whole early visual cortex:43%, V1:42%, V2:40% and V3:42%; all p>0.05) and in their respective eccentricities (all p>0.05).
Since our participants scored low for spontaneous visual imagery, and because Vetter et al.’s (2014) reported deactivation patterns and eccentricity differences do not fit a voluntary visual imagery account, we suggest that our lack of findings arose from our participants’ inability to engage in involuntary imagery. Moreover, we propose that auditory feedback to the early visual cortex may stand as a form of involuntary imagery which does not necessitate awareness, being elicited through previously integrated multisensory associations.
This is a 2021 ARVO Annual Meeting abstract.
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