Learning to name smells increases activity in heteromodal semantic areas

Abstract

Semantic description of odors is a cognitively demanding task. Learning to name smells is, however, possible with training. This study set out to examine how improvement in olfactory semantic knowledge following training reorganizes the neural representation of smells. First, 19 nonexpert volunteers were trained for 3 days; they were exposed (i) to odorants presented without verbal labels (perceptual learning) and (ii) to other odorants paired with lexicosemantic labels (associative learning). Second, the same participants were tested in a brain imaging study (fMRI) measuring hemodynamic responses to learned odors presented in both the perceptual and associative learning conditions. The lexicosemantic training enhanced the ability to describe smells semantically. Neurally, this change was associated with enhanced activity in a set of heteromodal areas-including superior frontal gyrus-and parietal areas. These findings demonstrate that odor-name associative learning induces recruitment of brain areas involved in the integration and representation of semantic attributes of sensory events. They also offer new insights into the brain plasticity underlying the acquisition of olfactory expertise in lay people. Hum Brain Mapp 38:5958-5969, 2017. © 2017 Wiley Periodicals, Inc.

Effectiveness of olfactory training on different severities of posttraumatic loss of smell

“…In a recent study, training individuals for 3 days to associate a specific smell with lexicosemantic features generated large activations in the superior frontal gyrus (SFG) and AG compared to perceptual learning or no training. Training effects showed increased ability in a semantic task that positively correlated with SFG activations . Additionally, another study using a yes‐no odor recognition paradigm showed the middle frontal gyrus, cingulate, and AG to be activated during odor recognition .…”

“…The angular gyrus (AG) connects to ipsilateral frontal areas via the superior longitudinal fasciculus . Semantic processing is the most consistent function that activates the left AG . Similar to the AG, the left superior frontal gyrus is strongly connected to Broca's area, and is associated with semantic functions .…”

“…45 Semantic processing is the most consistent function that activates the left AG. [46][47][48][49][50] Similar to the AG, the left superior frontal gyrus is strongly connected to Broca's area, 44 and is associated with semantic functions. 51 Our study saw activations in the posterior superior frontal gyrus, which has anatomical connections with the thalamus, precentral gyrus, and inferior frontal gyrus.…”

“…Training effects showed increased ability in a semantic task that positively correlated with SFG activations. 47 Additionally, another study using a yes-no odor recognition paradigm showed the middle frontal gyrus, cingulate, and AG to be activated during odor recognition. 53 In the current study, we show activation in these areas after olfactory training for hyposmic patients whose ability to identify the odors presented increased.…”

Consistent verbal labels promote odor category learning

“…Second, a design where participants implicitly learn how a new label relates to odors, commonly known to represent "the muted sense" (Olofson & Gotfried, 2015), enables us to compare category formation patterns when olfactory cues are "unmuted" either with concordantly or discordantly paired linguistic cues. Third, working with a modality where stimulus identification is difficult but trainable (Fournel, Sezille, Licon, Sinding, et al 2017;Morquecho-Campos, Larsson, Boesveldt, Olofsson, 2019) helps avoid rapid ceiling effects. We can work with a modality where initial categorization performance is likely to be near chance level with gradual accuracy increases over learning.…”