Dataset Information

Distinct memories of odor intensity and quality in Drosophila.

ABSTRACT: Even in a simple Pavlovian memory task an animal may form several associations that can be independently assessed by the appropriate tests. Studying conditioned odor discrimination of the fruit fly Drosophila melanogaster we found that animals store quality and intensity of an odor as separate memory traces. The trace of odor intensity is short-lived, decaying in <3 h. Only the last intensity value is stored. In contrast to odor-quality memory, odor-intensity memory does not require the rutabaga-dependent cAMP signaling pathway. Flies rely on their memory of intensity in a narrow concentration range in which they can generalize intensity. Larger concentration differences they treat like different qualities. This study shows that the perceptual identity of an odor is based on at least three lines of processing in the brain: (i) a memory of odor quality, (ii) a memory of odor intensity, and (iii) a range of intensities (and qualities), in which the odor is generalized.

SUBMITTER: Masek P

PROVIDER: S-EPMC2556361 | biostudies-literature | 2008 Oct

REPOSITORIES: biostudies-literature

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Distinct memories of odor intensity and quality in Drosophila.

Masek Pavel P Heisenberg Martin M

Proceedings of the National Academy of Sciences of the United States of America 20080929 41

Even in a simple Pavlovian memory task an animal may form several associations that can be independently assessed by the appropriate tests. Studying conditioned odor discrimination of the fruit fly Drosophila melanogaster we found that animals store quality and intensity of an odor as separate memory traces. The trace of odor intensity is short-lived, decaying in <3 h. Only the last intensity value is stored. In contrast to odor-quality memory, odor-intensity memory does not require the rutabaga ...[more]

PMID: 18824685

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Project description:The sensitivity of animals to sensory input must be regulated to ensure that signals are detected and also discriminable. However, how circuits regulate the dynamic range of sensitivity to sensory stimuli is not well understood. A given odor is represented in the insect mushroom bodies (MBs) by sparse combinatorial coding by Kenyon cells (KCs), forming an odor quality representation. To address how intensity of sensory stimuli is processed at the level of the MB input region, the calyx, we characterized a set of novel mushroom body output neurons that respond preferentially to high odor concentrations. We show that a pair of MB calyx output neurons, MBON-a1/2, are postsynaptic in the MB calyx, where they receive extensive synaptic inputs from KC dendrites, the inhibitory feedback neuron APL, and octopaminergic sVUM1 neurons, but relatively few inputs from projection neurons. This pattern is broadly consistent in the third-instar larva as well as in the first instar connectome. MBON-a1/a2 presynaptic terminals innervate a region immediately surrounding the MB medial lobe output region in the ipsilateral and contralateral brain hemispheres. By monitoring calcium activity using jRCamP1b, we find that MBON-a1/a2 responses are odor-concentration dependent, responding only to ethyl acetate (EA) concentrations higher than a 200-fold dilution, in contrast to MB neurons which are more concentration-invariant and respond to EA dilutions as low as 10–4. Optogenetic activation of the calyx-innervating sVUM1 modulatory neurons originating in the SEZ (Subesophageal zone), did not show a detectable effect on MBON-a1/a2 odor responses. Optogenetic activation of MBON-a1/a2 using CsChrimson impaired odor discrimination learning compared to controls. We propose that MBON-a1/a2 form an output channel of the calyx, summing convergent sensory and modulatory input, firing preferentially to high odor concentration, and might affect the activity of downstream MB targets.

Project description:ImportanceMajor depressive disorder (MDD) is associated with deficits in autobiographical memory (AM) recall, which is thought to stem from disruptions in effortful recall. Understanding whether these deficits are mitigated when recall is stimulated more directly, such as by odor cues, could inform therapeutic interventions for MDD.ObjectiveTo evaluate whether deficits in specific AM recall in MDD are mitigated when odor cues vs word cues are used to prompt memory.Design, setting, and participantsThis cross-sectional study assessed recall of specific AMs in response to both odor cues and word cues (in a randomized, counterbalanced order) in a repeated measures design. Data were collected between September 2021 and November 2022. The study took place at the University of Pittsburgh School of Medicine in Pennsylvania and included adults with a primary diagnosis of MDD, according to the Mini International Neuropsychiatric Interview. Data were analyzed from January to June 2023.Main outcomes and measuresThe primary outcome measure was the percentage of specific AMs recalled in response to odor-cued memories vs word-cued memories. Additional outcome measures included ratings of arousal, vividness, repetition, and recall response time for odor-cued memories vs word-cued memories.ResultsThirty-two adults (mean [SD] age, 30.0 [10.1] years; 26 [81.3%] female; 6 [18.8%] male) with a primary diagnosis of MDD completed the study. Participants recalled more specific AMs for odor cues than word cues (mean [SD], 68.4% [20.4%] vs 52.1% [23.3%]; Cohen d, 0.78; P < .001). Additionally, odor-cued recall was rated more arousing (mean [SD], 3.0 [0.8] vs 2.6 [0.7]; Cohen d, 1.28; P < .001) and vivid (mean [SD], 3.3 [0.7] vs 3.0 [0.7]; Cohen d, 0.67; P < .001), and was slower than word-cued recall (mean [SD], 14.5 [3.6] vs 8.9 [3.4] seconds; Cohen d, 1.18; P < .001). When compared with the population mean for word cues in healthy controls (80%), participants recalled fewer specific memories in response to words (Cohen d, 1.18; P < .001), supporting the presence of overgenerality. Notably, the percentage of specific memories recalled in response to odor cues did not differ from the healthy control population mean (Cohen d, 0.26; P = .15).Conclusions and relevanceIn this cross-sectional study, adults with MDD recalled more specific AMs in response to odor cues compared with word cues. This study suggests that AM deficits may only be observed when verbal cues are used and provides a potential new method for increasing specific AM recall in patients with MDD.

Dataset Information

Distinct memories of odor intensity and quality in Drosophila.

Publications

Distinct memories of odor intensity and quality in Drosophila.

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