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A specialized odor memory buffer in primary olfactory cortex.

Zelano C, Montag J, Khan R, Sobel N - PLoS ONE (2009)

Bottom Line: The neural substrates of olfactory working memory are unknown.We addressed the questions of whether olfactory working memory involves a verbal representation of the odor, or a sensory image of the odor, or both, and the location of the neural substrates of these processes.These findings suggest a novel dedicated mechanism in primary olfactory cortex, where odor information is maintained in temporary storage to subserve ongoing tasks.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurobiology, Weizmann Institute of Science, Rehovot, Israel. czelano@gmail.com

ABSTRACT

Background: The neural substrates of olfactory working memory are unknown. We addressed the questions of whether olfactory working memory involves a verbal representation of the odor, or a sensory image of the odor, or both, and the location of the neural substrates of these processes.

Methodology/principal findings: We used functional magnetic resonance imaging to measure activity in the brains of subjects who were remembering either nameable or unnameable odorants. We found a double dissociation whereby remembering nameable odorants was reflected in sustained activity in prefrontal language areas, and remembering unnameable odorants was reflected in sustained activity in primary olfactory cortex.

Conclusions/significance: These findings suggest a novel dedicated mechanism in primary olfactory cortex, where odor information is maintained in temporary storage to subserve ongoing tasks.

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Related in: MedlinePlus

Memory-related activity in piriform cortex.Each panel shows the time course of activity that has been normalized such that the maximum response to sniff-one is equal to 1. This enabled comparisons of activity levels during the delay period. Only the nameable (in black) and unnameable (in red) 10-second-delay conditions are shown along with an additional control condition in which subjects remembered auditory pitches (in green) for 10 seconds. Bar graphs depict the minimum activity level from 6-seconds after the first sniff to the time that the subject was instructed to prepare for the second sniff. This provides a measure of how well activity levels were sustained during the delay (note that because the bar graphs in this figure depict the minimal value, the bar may reveal a negative value even when the mean was positive, e.g., black line in panel A). A. Memory-related activity in right frontal piriform cortex. B. Memory-related activity in right frontal olfactory area. C. Memory-related activity in left frontal piriform cortex. D. Memory-related activity in left frontal olfactory area. In all subregions, the level of activity during the delay period was greater when subjects were remembering unnameable odorants as compared to nameable odorants. In the olfactory area, activity levels were hierarchically organized in the following manner: unnameable>nameable>auditory pitch. In frontal piriform cortex, remembering unnameable odors elicited more activity than nameable odors, but remembering nameable odors and auditory pitches both elicited a similar level of activity during the delay (unnameable>nameable = auditory pitch).
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pone-0004965-g005: Memory-related activity in piriform cortex.Each panel shows the time course of activity that has been normalized such that the maximum response to sniff-one is equal to 1. This enabled comparisons of activity levels during the delay period. Only the nameable (in black) and unnameable (in red) 10-second-delay conditions are shown along with an additional control condition in which subjects remembered auditory pitches (in green) for 10 seconds. Bar graphs depict the minimum activity level from 6-seconds after the first sniff to the time that the subject was instructed to prepare for the second sniff. This provides a measure of how well activity levels were sustained during the delay (note that because the bar graphs in this figure depict the minimal value, the bar may reveal a negative value even when the mean was positive, e.g., black line in panel A). A. Memory-related activity in right frontal piriform cortex. B. Memory-related activity in right frontal olfactory area. C. Memory-related activity in left frontal piriform cortex. D. Memory-related activity in left frontal olfactory area. In all subregions, the level of activity during the delay period was greater when subjects were remembering unnameable odorants as compared to nameable odorants. In the olfactory area, activity levels were hierarchically organized in the following manner: unnameable>nameable>auditory pitch. In frontal piriform cortex, remembering unnameable odors elicited more activity than nameable odors, but remembering nameable odors and auditory pitches both elicited a similar level of activity during the delay (unnameable>nameable = auditory pitch).

Mentions: Next, to ask whether sustained activity due to remembering nameable and unnameable odorants was dissociable in primary olfactory cortex, we compared levels of sustained activity during the delay period of the delayed match to sample task (figure 5A–D, figure S3A). Given that the initial response to nameable and unnameable odorants differed in primary olfactory cortex, we normalized the response to the first sniff so that it was the same for nameable and unnameable odorants, allowing for a meaningful comparison between the two odorant categories during the delay (see methods). Because of the lower reliably in dissociating responses from two sniffs taken 5 seconds apart (due to the temporal resolution of fMRI), we restricted this analysis to include only the 10-second delay conditions of the delayed match to sample task.


A specialized odor memory buffer in primary olfactory cortex.

Zelano C, Montag J, Khan R, Sobel N - PLoS ONE (2009)

Memory-related activity in piriform cortex.Each panel shows the time course of activity that has been normalized such that the maximum response to sniff-one is equal to 1. This enabled comparisons of activity levels during the delay period. Only the nameable (in black) and unnameable (in red) 10-second-delay conditions are shown along with an additional control condition in which subjects remembered auditory pitches (in green) for 10 seconds. Bar graphs depict the minimum activity level from 6-seconds after the first sniff to the time that the subject was instructed to prepare for the second sniff. This provides a measure of how well activity levels were sustained during the delay (note that because the bar graphs in this figure depict the minimal value, the bar may reveal a negative value even when the mean was positive, e.g., black line in panel A). A. Memory-related activity in right frontal piriform cortex. B. Memory-related activity in right frontal olfactory area. C. Memory-related activity in left frontal piriform cortex. D. Memory-related activity in left frontal olfactory area. In all subregions, the level of activity during the delay period was greater when subjects were remembering unnameable odorants as compared to nameable odorants. In the olfactory area, activity levels were hierarchically organized in the following manner: unnameable>nameable>auditory pitch. In frontal piriform cortex, remembering unnameable odors elicited more activity than nameable odors, but remembering nameable odors and auditory pitches both elicited a similar level of activity during the delay (unnameable>nameable = auditory pitch).
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2654926&req=5

pone-0004965-g005: Memory-related activity in piriform cortex.Each panel shows the time course of activity that has been normalized such that the maximum response to sniff-one is equal to 1. This enabled comparisons of activity levels during the delay period. Only the nameable (in black) and unnameable (in red) 10-second-delay conditions are shown along with an additional control condition in which subjects remembered auditory pitches (in green) for 10 seconds. Bar graphs depict the minimum activity level from 6-seconds after the first sniff to the time that the subject was instructed to prepare for the second sniff. This provides a measure of how well activity levels were sustained during the delay (note that because the bar graphs in this figure depict the minimal value, the bar may reveal a negative value even when the mean was positive, e.g., black line in panel A). A. Memory-related activity in right frontal piriform cortex. B. Memory-related activity in right frontal olfactory area. C. Memory-related activity in left frontal piriform cortex. D. Memory-related activity in left frontal olfactory area. In all subregions, the level of activity during the delay period was greater when subjects were remembering unnameable odorants as compared to nameable odorants. In the olfactory area, activity levels were hierarchically organized in the following manner: unnameable>nameable>auditory pitch. In frontal piriform cortex, remembering unnameable odors elicited more activity than nameable odors, but remembering nameable odors and auditory pitches both elicited a similar level of activity during the delay (unnameable>nameable = auditory pitch).
Mentions: Next, to ask whether sustained activity due to remembering nameable and unnameable odorants was dissociable in primary olfactory cortex, we compared levels of sustained activity during the delay period of the delayed match to sample task (figure 5A–D, figure S3A). Given that the initial response to nameable and unnameable odorants differed in primary olfactory cortex, we normalized the response to the first sniff so that it was the same for nameable and unnameable odorants, allowing for a meaningful comparison between the two odorant categories during the delay (see methods). Because of the lower reliably in dissociating responses from two sniffs taken 5 seconds apart (due to the temporal resolution of fMRI), we restricted this analysis to include only the 10-second delay conditions of the delayed match to sample task.

Bottom Line: The neural substrates of olfactory working memory are unknown.We addressed the questions of whether olfactory working memory involves a verbal representation of the odor, or a sensory image of the odor, or both, and the location of the neural substrates of these processes.These findings suggest a novel dedicated mechanism in primary olfactory cortex, where odor information is maintained in temporary storage to subserve ongoing tasks.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurobiology, Weizmann Institute of Science, Rehovot, Israel. czelano@gmail.com

ABSTRACT

Background: The neural substrates of olfactory working memory are unknown. We addressed the questions of whether olfactory working memory involves a verbal representation of the odor, or a sensory image of the odor, or both, and the location of the neural substrates of these processes.

Methodology/principal findings: We used functional magnetic resonance imaging to measure activity in the brains of subjects who were remembering either nameable or unnameable odorants. We found a double dissociation whereby remembering nameable odorants was reflected in sustained activity in prefrontal language areas, and remembering unnameable odorants was reflected in sustained activity in primary olfactory cortex.

Conclusions/significance: These findings suggest a novel dedicated mechanism in primary olfactory cortex, where odor information is maintained in temporary storage to subserve ongoing tasks.

Show MeSH
Related in: MedlinePlus