Olfactory Context Dependent Memory: Direct Presentation of Odorants

Summary

The use of an olfactometer for directly presenting odorants opens exciting opportunities for researchers of olfactory memory. The current paper discusses issues related to this methodology as related to a previously published experiment on olfactory context dependent memory.

Abstract

Information is retrieved more effectively when the retrieval occurs in the same context as that in which the information was first encoded. This is termed context dependent memory (CDM). One category of cues that have been shown to effectively produce CDM effects are odors. However, it is unclear what the boundary conditions of these CDM effects are. In particular, given that olfaction has been called an implicit sense, it is possible that odors are only effective mnemonic cues when they are presented in the background. This assertion seems even more likely given that previous research has shown odors to be poor cues during paired associate memory tests, where odors are in the focus of attention as mnemonic cues for other information. In order to determine whether odors are only effective contextual mnemonic cues when presented outside the central focus of an observer, an olfactory CDM experiment was performed in which odorants were presented directly, rather than ambiently. Direct presentation was accomplished with the aid of an olfactometer. The olfactometer not only allows for direct presentation of odorants, but provides other methodological benefits, including the allowance of trial by trial manipulations of odorant presentations and, relatedly, time-specific releases of odorants. The presence of the same odor during both encoding and retrieval enhanced memory performance, regardless of whether the odor was presented ambiently or directly. This finding can serve as a basis for future olfactory CDM research which can utilize the benefits of direct presentation.

Introduction

Retrieval is enhanced when it occurs in the same context as encoding^1,2; this is termed context dependent memory (CDM). Many stimuli have been shown to be effective contextual cues for enhancing retrieval³. In line with this general research, it has been shown that information that is learned and retrieved in the presence of the same odor is remembered better than information that is retrieved in the presence of a different odor⁴ or information that is neither learned nor retrieved in the presence of an extra olfactory context⁵; this has b....

Protocol

All data collection in the original experiment¹⁵ was performed in accordance with the ethical guidelines of the American Psychological Association as well as the World Medical Association’s Declaration of Helsinki. The experiment was preapproved by the local Ethik-Kommission (equivalent to an Institutional Review Board). All subjects were made aware that their participation was voluntary and could at any time and without fear of penalty be terminated. All subjects signed informed consent.

1. Participant Recruitment and Pre-study Instructions

1. Recruitment:
   1. Recruit particip....

Results

One of the main purposes of the current experiment was to determine whether OCDM effects could be found when the olfactory context was presented directly, rather than ambiently. There were three main dependent variables (in line with common signal detection theory analyses²⁶): the proportion of hits, the proportion of false alarms, and a corrected accuracy score termed d'. Given the focus of interest here, the data from the two odor groups from the ori.......

Discussion

The method described here, in which an olfactometer is used to directly present odorants as contextual stimuli, represents an expansion of the utility of olfactometers in olfactory memory research^16,17. Specifically, this method allows for an expansion of the area of OCDM research. Previous research had shown that odors are indeed effective contextual mnemonic cues^4,14, but all research to this point has .......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Olfactometer	Burghart Messtechnik	OG001	Discrete presentation olfactometer
Odiferous material_Onion	Burghart Messtechnik	LA-13-00236	Liquid used in olfactometer to produce onion odor
Odiferous material_Peach	Burghart Messtechnik	LA-13-00245	Liquid used in olfactometer to produce peach odor
E-Prime 2.0	Psychology Software Tools		Experiment control software