Abstract
Blindness can be a driving force behind a variety of changes in sensory systems. When vision is missing, other modalities and higher cognitive functions can become hyper-developed through a mechanism called sensory compensation. Overall, previous studies suggest that olfactory memory in blind people can be better than that of the sighted individuals. Better performance of blind individuals in other-sensory modalities was hypothesized to be a result of, among others, intense perceptual training. At the same time, if the superiority of blind people in olfactory abilities indeed results from training, their scores should not decrease with age to such an extent as among the sighted people. Here, this hypothesis was tested in a large sample of 94 blind individuals. Olfactory memory was assessed using the Test for Olfactory Memory, comprising episodic odor recognition (discriminating previously presented odors from new odors) and two forms of semantic memory (cued and free identification of odors). Regarding episodic olfactory memory, we observed an age-related decline in correct hits in blind participants, but an age-related increase in false alarms in sighted participants. Further, age moderated the between-group differences for correct hits, but the direction of the observed effect was contrary to our expectations. The difference between blind and sighted individuals younger than 40 years old was non-significant, but older sighted individuals outperformed their blind counterparts. In conclusion, we found no positive effect of visual impairment on olfactory memory. We suggest that daily perceptual training is not enough to increase olfactory memory function in blind people.
Highlights
Blindness can be a driving force behind a variety of changes in sensory systems
Several studies demonstrated that blind people performed better than sighted individuals in olfactory discrimination, which is often considered to reflect short-term olfactory memory (Cuevas et al, 2009, 2010; Rombaux et al, 2010; Renier et al, 2013; Çomoglu et al, 2015)
No differences between sighted and blind individuals were observed in the remaining cases – false alarm rate, correct rejection rate and d scores were similar in both groups (Figure 2)
Summary
Blindness can be a driving force behind a variety of changes in sensory systems. When vision is missing, other modalities and higher cognitive functions can become hyper-developed (PascualLeone et al, 2005) through a mechanism called sensory compensation (Kupers and Ptito, 2014). Better performance of blind individuals in other-sensory modalities was hypothesized to be a result of either intense perceptual training (Gagnon et al, 2015), reorganization of various brain areas (e.g., the occipital cortex, Leclerc et al, 2000), or a combination of both of these mechanisms (Röder and Rösler, 2003). Free identification time was shorter among blind compared to sighted individuals (Rosenbluth et al, 2000; Gagnon et al, 2015), highlighting proficiency of visually impaired people in smellrelated memory tasks. Several studies demonstrated that blind people performed better than sighted individuals in olfactory discrimination, which is often considered to reflect short-term olfactory memory (Cuevas et al, 2009, 2010; Rombaux et al, 2010; Renier et al, 2013; Çomoglu et al, 2015). In the case of this olfactory ability the results were not consistent – other researchers demonstrated that olfactory discrimination skills do not depend on visual status (Schwenn et al, 2002; Beaulieu-Lefebvre et al, 2011; Oniz et al, 2011; Luers et al, 2014; Majchrzak and Eberhard, 2014; Cornell Kärnekull et al, 2016; Guducu et al, 2016; Sorokowska, 2016)
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