Maria Larsson

Cognitive factors in odor detection, odor discrimination, and odor identification tasks

The purpose of this study was to determine cognitive correlates of olfactory performance across three different tasks. A total of 170 men and women (30–87 years of age) were assessed in olfactory sensitivity, discrimination, and identification. Also, participants were tested in a range of cognitive tests covering executive functioning, semantic memory, and episodic memory. Hierarchical regression analyses showed that proficiency in executive functioning and semantic memory contributed significantly to odor discrimination and identification performance, whereas all of the cognitive factors proved unrelated to performance in the odor threshold test. This pattern of outcome suggests that an individuals cognitive profile exerts a reliable influence on performance in higher order olfactory tasks.

Smell your way back to childhood: Autobiographical odor memory

This study addressed age distributions and experiential qualities of autobiographical memories evoked by different sensory cues. Ninety-three older adults were presented with one of three cue types (word, picture, or odor) and were asked to relate any autobiographical event for the given cue. The main aims were to explore whether (1) the age distribution of olfactory-evoked memories differs from memories cued by words and pictures and (2) the experiential qualities of the evoked memories vary over the different cues. The results showed that autobiographical memories triggered by olfactory information were older than memories associated with verbal and visual information. Specifically, most odor-cued memories were located to the first decade of life (<10 years), whereas memories associated with verbal and visual cues peaked in early adulthood (11–20 years). Also, odor-evoked memories were associated with stronger feelings of being brought back in time and had been thought of less often than memories evoked by verbal and visual information. This pattern of findings suggests that odor-evoked memories may be different from other memory experiences. nt|mis|This work was supported by a grant from the Swedish Research Council (No. F0647/2001) to M.L.

Differential sex effects in olfactory functioning: The role of verbal processing

We investigated sex difference across a number of olfactory tasks. Thirty-six men and 35 women ranging in age from 19 to 36 years were assessed in 6 different tasks: absolute sensitivity for n-butanol, intensity discrimination, quality discrimination, episodic recognition memory for familiar and unfamiliar odors, and odor identification. No sex differences were observed in the tasks tapping primarily sensory acuity (i.e., odor sensitivity, intensity discrimination, and quality discrimination) or in episodic memory for unfamiliar odors. By contrast, women outperformed men in the tasks involving verbal processing (i.e., memory for familiar odors and odor identification). Interestingly, controlling for odor naming ability resulted in that the observed sex difference in episodic odor memory for familiar odors disappeared. This outcome suggests that womens superiority in episodic odor memory is largely mediated by their higher proficiency in odor identification.

Olfaction and emotion: The case of autobiographical memory

This study investigated (1) the influence of verbal and conceptual processing on the retrieval and phenomenological evaluation of olfactory evoked memories, and (2) whether the experienced qualities of retrieved information are affected by olfactory exposure per se. Seventy-two older adults were randomized into one of three cue conditions (odor only, name only, or odor name) and asked to relate any autobiographical event for the given cue. The results indicated that semantic knowledge of an odor’s name significantly affects the age distribution of memories such that the memory peak in childhood observed for odors only was attenuated. Also, experiential factors such as pleasantness and feelings of being brought back in time were lower when odors were presented with their respective names. Olfactory evoked memories were associated with a higher emotional arousal that could not be accounted for by the perceptual stimulation alone. Taken together, the overall pattern of findings suggests that retrieval of olfactory evoked information is sensitive to semantic and conceptual processing, and that odor-evoked representations are more emotional than memories triggered by verbal information.

What people believe about memory.

Two representative samples of adult Norwegians (n=2000) were asked a set of general and specific questions regarding their beliefs and opinions about human memory. The results indicate that on many questions, such as time of the earliest memories, inhibiting effects of collaboration, and memory for dramatic versus ordinary events, the views of the general public concurred with current research findings, and people in general had realistic views about their own memory performance. On other questions, such as the reliability of olfactory as compared with visual and auditory memory, the memory of small children in comparison with that of adults, the likelihood of repression of adult traumatic memories, and on more general questions such as the possibility of training memory and the capacity limitations of long-term memory, a large proportion of the participants expressed views that are less supported by scientific evidence. Implications of these findings are briefly discussed.

Depth of olfactory sulcus and olfactory function.

The aim of this study was to identify whether the depth of the olfactory sulcus relates to olfactory function in healthy subjects. Forty-four healthy, male volunteers (age range 22-45 years, mean age 28.3 years) were included in this study. Olfactory function was measured for phenyl ethyl alcohol odor thresholds, odor discrimination, and odor identification. Magnetic resonance imaging of the olfactory sulcus was performed immediately following olfactometry. Based on previous investigations the depth of the olfactory sulcus was measured in the plane of the posterior tangent through the eyeballs. Olfactory function correlated significantly with left-sided depth of the olfactory sulcus (r(44)=0.33, P=0.03); no such correlation was seen for the right side. In addition, olfactory sulcus depth was found to be significantly deeper on the right compared to the left side (t=5.61, P<0.001). The present results suggest that there is small, but significant relation between morphological brain structures and measures of olfactory function. Further, lateralization of olfactory sulcus depth may correlate to functional lateralization in the olfactory system. Thus, it may be carefully speculated that sensory input in the olfactory system results in cortical growth in the area of the olfactory sulcus, at least at some developmental stage.

Semantic activation and episodic odor recognition in young and older adults

Young, young-old, and old adults were examined in immediate and delayed episodic recognition of common odors. Items were presented in 3 different formats: name-only, odor-only, or odor-name. Ss made familiarity ratings for all items at study. In the delayed recognition test, Ss were asked to name the odors. Young Ss outperformed the 2 older age groups in both recognition tests, although the 2 older groups did not differ. Performance was higher in the odor-name condition than in the single-format conditions. Both familiarity and naming were related to recognition in all age groups. Most important, when naming was statistically controlled, age differences in odor recognition disappeared, suggesting that access to verbal labels largely determine age differences in recognition of common odors. Finally, the finding that recognition was enhanced in both young and older Ss in the odor-name condition suggests that odor memory may involve a similar degree of plasticity as other varieties of episodic memory.

Low episodic memory performance as a premorbid marker of depression: evidence from a 3‐year follow‐up

Objective:  To examine low episodic memory scores as a potential risk factor for depression.

Autobiographical Odor Memory

This overview focuses on autobiographical odor memory and how information evoked by the olfactory sense may differ from memories evoked by visual or verbal information. Three key topics are addressed: (a) age distributions of evoked memories; (b) phenomenological experience; and (c) semantic processing. Current evidence suggests that memories triggered by olfactory information are localized to the first decade of life (< 10 years) rather than to young adulthood (10–30 years) which is the typical finding for memories evoked by verbal and visual information. Further, empirical evidence indicates that odor evoked memories are more emotional, associated with stronger feelings of being brought back in time, and have been thought of less often as compared to memories evoked by other sensory cues. Finally, previous observations of a significant impact of semantic influences on olfactory processing may also be generalized to retrieval of odor evoked autobiographical information. Specifically, both the age distribution and phenomenological qualities are affected by explicit knowledge of the odor cue. Taken together, the overall pattern of findings indicates that personal memories evoked by olfactory information are different from memories evoked by verbal or visual information.

The functional neuroanatomy of odor evoked autobiographical memories cued by odors and words

Behavioral evidence indicates that odor evoked autobiographical memories (OEAMs) are older, more emotional, less thought of and induce stronger time traveling characteristics than autobiographical memories (AMs) evoked by other modalities. The main aim of this study was to explore the neural correlates of AMs evoked by odors as a function of retrieval cue. Participants were screened for specific OEAMs and later presented with the odor cue and its verbal referent in an fMRI paradigm. Because the same OEAM was retrieved across both cue formats (odor and word), potential cue dependent brain activations were investigated. The overall results showed that odor and word cued OEAMs activated regions typically associated with recollection of autobiographical information. Although no odors were presented, a verbal cuing of the OEAMs activated areas associated with olfactory perception (e.g., piriform cortex). However, relative to word cuing, an odor cuing of OEAMs resulted in more activity in MTL regions such as the parahippocampus, and areas involved in visual vividness (e.g., occipital gyrus and precuneus). Furthermore, odor cues activated areas related to emotional processing, such as limbic and tempopolar regions significantly more. In contrast, word cues relative to odor cues recruited a more widespread and bilateral prefrontal activity. Hippocampus activity did not vary as function of the remoteness of the memory, but recollection of OEAMs from the 1(st) vs the 2(nd) decade of life showed specific activation in the right OFC, whereas the 2(nd) reflected a higher activation in the left inferior frontal gyrus.