True and False Recognition Memories of Odors Induce Distinct Neural Signatures

Abstract

Neural bases of human olfactory memory are poorly understood. Very few studies have examined neural substrates associated with correct odor recognition, and none has tackled neural networks associated with incorrect odor recognition. We investigated the neural basis of task performance during a yes–no odor recognition memory paradigm in young and elderly subjects using event-related functional magnetic resonance imaging. We explored four response categories: correct (Hit) and incorrect false alarm (FA) recognition, as well as correct (CR) and incorrect (Miss) rejection, and we characterized corresponding brain responses using multivariate analysis and linear regression analysis. We hypothesized that areas of the medial temporal lobe were differentially involved depending on the accuracy of odor recognition. In young adults, we found that significant activity in the hippocampus and the parahippocampal gyrus was associated with correct (true) recognition of odors, whereas the perirhinal cortex was associated with FAs and Misses. These findings are consistent with literature regarding hypothetical functional organization for memory processing. We also found that for correct recognition and rejection responses, the involvement of the hippocampus decreased when memory performances improved. In contrast to young individuals, elderly subjects were more prone to false memories and exhibited less specific activation patterns for the four response categories. Activation in the hippocampus and the parahippocampal gyrus was positively correlated with response bias scores for true and false recognition, demonstrating that conservative subjects produced an additional search effort leading to more activation of these two medial temporal lobe regions. These findings demonstrate that correct and incorrect recognition and rejection induce distinct neural signatures.

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

“…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 . In the current study, we show activation in these areas after olfactory training for hyposmic patients whose ability to identify the odors presented increased.…”

False memories with age: Neural and cognitive underpinnings

“…Corroborating findings have been reported using fMRI; unlike younger adults, older adults do not display differential activation for novel items conceptually similar to or different from studied information (Bowman and Dennis, 2015). Older adults also exhibit less specific activation patterns during recollection of true and false information (Duarte et al, 2010; Royet et al, 2011). The overlap in neural signatures with age suggests that older adults process information similarly regardless of novelty or authenticity, and are indicative of age-related difficulties in using distinctive item-specific information to make source decisions.…”

Default mode network deactivation during odor–visual association

“…Since the anterior POC is implicated in deciphering chemical identity of odorants and the posterior POC in mediating perceptual features, these two networks are hypothesized to handle primary olfactory-related processing [Gottfried, 2010;Karunanayaka et al, 2014]. Additionally, the hippocampus/parahippocampal region is differentially synchronized with the PON1 and the DMN during odor 1 visual (or visual-only) trial conditions and interleaved rest conditions [Goodrich-Hunsaker et al, 2009;Lehn et al, 2013;Royet et al, 2011]. Figure 2(i) and (ii) right shows the corresponding time courses of PON1 and PON2 networks.…”