Reduced Taste Sensitivity in Congenital Blindness

Abstract

Sight is undoubtedly not only important for food identification and selection but also for the modulation of gustatory sensitivity. We can, therefore, assume that taste sensitivity and eating habits are affected by visual deprivation from birth. We measured taste detection and identification thresholds of the 5 basic tastants in 13 congenitally blind and 13 sighted control subjects. Participants also answered several eating habits questionnaires, including the Food Neophobia Scale, the Food Variety Seeking Tendency Scale, the Intuitive Eating Scale, and the Body Awareness Questionnaire. Our behavioral results showed that compared with the normal sighted, blind subjects have increased thresholds for taste detection and taste identification. This finding is at odds with the superior performance of congenitally blind subjects in several tactile, auditory and olfactory tasks. Our psychometric data further indicate that blind subjects more strongly rely on internal hunger and satiety cues, instead of external contextual or emotional cues, to decide when and what to eat. We suggest that the lower taste sensitivity observed in congenitally blind individuals is due to various blindness-related obstacles when shopping for food, cooking and eating out, all of which contribute to underexpose the gustatory system to a larger variety of taste stimuli.

Making Sense of the Chemical Senses

“…2C and 2D. Our group further demonstrated that congenitally blind subjects have a better intuitive eating at titude (Tylka, 2006) compared to sighted subjects (Gagnon et al, 2013), a finding that was replicated by compiling data from our Danish and Canadian samples (Fig. IB).…”

“…Importantly, we have shown that taste sensitivity is lowered in congenital blindness (Gagnon et al, 2013), mak ing gustation the only remaining sensory modality in which the blind do not outperform the sighted. Indeed, taste detection and identification thresholds are significantly elevated in congenitally blind subjects compared to blind folded sighted controls, as illustrated in Fig.…”

“…This advantage is associated with a cross-modal plas tic response involving recruitment of the deprived visual cortex together with a general increased activity of chemosensory processing areas compared to normal sighted (Kupers et al,201 lb). However, when blind individuals pro cess chemosensory stimuli located inside their body, such as sweet, bitter and other basic tastes (Gagnon et al, 2013) and retronasal odours (Gagnon et al, subm. a), they perform worse than normal sighted subjects.…”

“…b). Based upon the blind's reduced gustatory performance in detecting and iden tifying tastants (Gagnon et al, 2013), and functional imaging studies showing correlations between occipital activity and sensory performance (Amedi et al, 2003;Gougoux et al, 2005;Ptito et al, 2005;Renier et al, 2013), we hypoth esized that congenitally blind would not recruit their occipital cortex to process taste information. Functional magnetic resonance imaging (fMRI) during a task requiring the rating of the intensity or pleasantness of tasty (sweet, bitter) and tasteless (artificial saliva) liquids showed blood-oxygen-level dependant (BOLD) signal increases in both blind and sighted groups in the left primary taste and somatosensory cortices in response to tastants compared to saliva.…”

Compensatory plasticity: time matters

“…Sighted controls in this case show the same lateralized right-olfactory and left-verbal pattern but all over their brain with no or little occipital activations (Renier et al, 2013). Fewer studies explored taste differences between blind and sighted and recent results show increased thresholds in taste detection and identification in the blind (Gagnon et al, 2013). …”