scholarly journals Representational drift in primary olfactory cortex

2020 ◽  
Author(s):  
Carl E. Schoonover ◽  
Sarah N. Ohashi ◽  
Richard Axel ◽  
Andrew J.P. Fink
Keyword(s):  
Olfactory System ◽  
Piriform Cortex ◽  
External World ◽  
Olfactory Cortex ◽  
Linear Classifier ◽  
Electrophysiological Recordings ◽  
Primary Olfactory Cortex ◽  
Sensory Cortices ◽  
The Stability

SummaryRepresentations of the external world in sensory cortices may define the identity of a stimulus and should therefore vary little over the life of the organism. In the olfactory system the primary olfactory cortex, piriform, is thought to determine odor identity1–6. We have performed electrophysiological recordings of single units maintained over weeks to examine the stability of odor representations in the mouse piriform cortex. We observed that odor representations drift over time, such that the performance of a linear classifier trained on the first recording day approaches chance levels after 32 days. Daily exposure to the same odorant slows the rate of drift, but when exposure is halted that rate increases once again. Moreover, behavioral salience does not stabilize odor representations. Continuous drift poses the question of the role of piriform in odor identification. This instability may reflect the unstructured connectivity of piriform7–15 and may be a property of other unstructured cortices.

scholarly journals Differential serotonergic modulation of principal neurons and interneurons in the anterior piriform cortex

2022 ◽  
Author(s):  
Magor L Lőrincz ◽  
Ildikó Piszár
Keyword(s):  
Piriform Cortex ◽  
Sensory Information ◽  
Olfactory Cortex ◽  
Anterior Piriform Cortex ◽  
Electrophysiological Recordings ◽  
Primary Olfactory Cortex ◽  
Brainstem Raphe ◽  
Evoked Activity ◽  
Sensory Evoked

Originating from the brainstem raphe nuclei, serotonin is an important neuromodulator involved in a variety of physiological and pathological functions. Specific optogenetic stimulation of serotonergic neurons results in the divisive suppression of spontaneous, but not sensory evoked activity in the majority of neurons in the primary olfactory cortex and an increase in firing in a minority of neurons. To reveal the mechanisms involved in this dual serotonergic control of cortical activity we used a combination of in vitro electrophysiological recordings from identified neurons in the primary olfactory cortex, optogenetics and pharmacology and found that serotonin suppressed the activity of principal neurons, but excited local interneurons. The results have important implications in sensory information processing and other functions of the olfactory cortex and related brain areas.

Time Course of Odorant-Induced Activation in the Human Primary Olfactory Cortex

2000 ◽  
Vol 83 (1) ◽  
pp. 537-551 ◽  
Author(s):  
Noam Sobel ◽  
Vivek Prabhakaran ◽  
Zuo Zhao ◽  
John E. Desmond ◽  
Gary H. Glover ◽  
...  
Keyword(s):  
Time Course ◽  
Piriform Cortex ◽  
Signal Amplitude ◽  
Olfactory Cortex ◽  
Transient Increase ◽  
Functional Neuroanatomy ◽  
Functional Magnetic Resonance ◽  
Physiological Level ◽  
Temporal Variance ◽  
Primary Olfactory Cortex

Paradoxically, attempts to visualize odorant-induced functional magnetic resonance imaging (fMRI) activation in the human have yielded activations in secondary olfactory regions but not in the primary olfactory cortex-piriform cortex. We show that odorant-induced activation in primary olfactory cortex was not previously made evident with fMRI because of the unique time course of activity in this region: in primary olfactory cortex, odorants induced a strong early transient increase in signal amplitude that then habituated within 30–40 s of odorant presence. This time course of activation seen here in the primary olfactory cortex of the human is almost identical to that recorded electrophysiologically in the piriform cortex of the rat. Mapping activation with analyses that are sensitive to both this transient increase in signal amplitude, and temporal-variance, enabled us to use fMRI to consistently visualize odorant-induced activation in the human primary olfactory cortex. The combination of continued accurate odorant detection at the behavioral level despite primary olfactory cortex habituation at the physiological level suggests that the functional neuroanatomy of the olfactory response may change throughout prolonged olfactory stimulation.

Early deficits in olfaction are associated with structural and molecular alterations in the olfactory system of a Huntington disease mouse model

2020 ◽  
Vol 29 (13) ◽  
pp. 2134-2147
Author(s):  
M Laroche ◽  
M Lessard-Beaudoin ◽  
M Garcia-Miralles ◽  
C Kreidy ◽  
E Peachey ◽  
...  
Keyword(s):  
Huntington Disease ◽  
Olfactory System ◽  
Piriform Cortex ◽  
Olfactory Dysfunction ◽  
Altered Expression ◽  
Neuronal Nuclei ◽  
Molecular Alterations ◽  
Cell Death Pathways ◽  
Structural Abnormalities

Abstract Olfactory dysfunction and altered neurogenesis are observed in several neurodegenerative disorders including Huntington disease (HD). These deficits occur early and correlate with a decline in global cognitive performance, depression and structural abnormalities of the olfactory system including the olfactory epithelium, bulb and cortices. However, the role of olfactory system dysfunction in the pathogenesis of HD remains poorly understood and the mechanisms underlying this dysfunction are unknown. We show that deficits in odour identification, discrimination and memory occur in HD individuals. Assessment of the olfactory system in an HD murine model demonstrates structural abnormalities in the olfactory bulb (OB) and piriform cortex, the primary cortical recipient of OB projections. Furthermore, a decrease in piriform neuronal counts and altered expression levels of neuronal nuclei and tyrosine hydroxylase in the OB are observed in the YAC128 HD model. Similar to the human HD condition, olfactory dysfunction is an early phenotype in the YAC128 mice and concurrent with caspase activation in the murine HD OB. These data provide a link between the structural olfactory brain region atrophy and olfactory dysfunction in HD and suggest that cell proliferation and cell death pathways are compromised and may contribute to the olfactory deficits in HD.

scholarly journals The Neurotransmitter Receptor Architecture of the Mouse Olfactory System

2021 ◽  
Vol 15 ◽  
Author(s):  
Kimberley Lothmann ◽  
Katrin Amunts ◽  
Christina Herold
Keyword(s):  
Olfactory System ◽  
Piriform Cortex ◽  
Hierarchical Cluster ◽  
Distribution Patterns ◽  
Olfactory Cortex ◽  
Cluster Solution ◽  
Olfactory Tubercle ◽  
Neurotransmitter Receptor ◽  
Heterogeneous Expression

The uptake, transmission and processing of sensory olfactory information is modulated by inhibitory and excitatory receptors in the olfactory system. Previous studies have focused on the function of individual receptors in distinct brain areas, but the receptor architecture of the whole system remains unclear. Here, we analyzed the receptor profiles of the whole olfactory system of adult male mice. We examined the distribution patterns of glutamatergic (AMPA, kainate, mGlu2/3, and NMDA), GABAergic (GABAA, GABAA(BZ), and GABAB), dopaminergic (D1/5) and noradrenergic (α1 and α2) neurotransmitter receptors by quantitative in vitro receptor autoradiography combined with an analysis of the cyto- and myelo-architecture. We observed that each subarea of the olfactory system is characterized by individual densities of distinct neurotransmitter receptor types, leading to a region- and layer-specific receptor profile. Thereby, the investigated receptors in the respective areas and strata showed a heterogeneous expression. Generally, we detected high densities of mGlu2/3Rs, GABAA(BZ)Rs and GABABRs. Noradrenergic receptors revealed a highly heterogenic distribution, while the dopaminergic receptor D1/5 displayed low concentrations, except in the olfactory tubercle and the dorsal endopiriform nucleus. The similarities and dissimilarities of the area-specific multireceptor profiles were analyzed by a hierarchical cluster analysis. A three-cluster solution was found that divided the areas into the (1) olfactory relay stations (main and accessory olfactory bulb), (2) the olfactory cortex (anterior olfactory cortex, dorsal peduncular cortex, taenia tecta, piriform cortex, endopiriform nucleus, entorhinal cortex, orbitofrontal cortex) and the (3) olfactory tubercle, constituting its own cluster. The multimodal receptor-architectonic analysis of each component of the olfactory system provides new insights into its neurochemical organization and future possibilities for pharmaceutic targeting.

scholarly journals Post-traumatic olfactory loss and brain response beyond olfactory cortex

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Robert Pellegrino ◽  
Michael C. Farruggia ◽  
Dana M. Small ◽  
Maria G. Veldhuizen
Keyword(s):  
Piriform Cortex ◽  
Posterior Cingulate Cortex ◽  
Olfactory Cortex ◽  
Neural Responses ◽  
Brain Response ◽  
Olfactory Loss ◽  
Frontal Operculum ◽  
Post Traumatic ◽  
Olfactory Impairment

AbstractOlfactory impairment after a traumatic impact to the head is associated with changes in olfactory cortex, including decreased gray matter density and decreased BOLD response to odors. Much less is known about the role of other cortical areas in olfactory impairment. We used fMRI in a sample of 63 participants, consisting of 25 with post-traumatic functional anosmia, 16 with post-traumatic hyposmia, and 22 healthy controls with normosmia to investigate whole brain response to odors. Similar neural responses were observed across the groups to odor versus odorless stimuli in the primary olfactory areas in piriform cortex, whereas response in the frontal operculum and anterior insula (fO/aI) increased with olfactory function (normosmia > hyposmia > functional anosmia). Unexpectedly, a negative association was observed between response and olfactory perceptual function in the mediodorsal thalamus (mdT), ventromedial prefrontal cortex (vmPFC) and posterior cingulate cortex (pCC). Finally, connectivity within a network consisting of vmPFC, fO, and pCC could be used to successfully classify participants as having functional anosmia or normosmia. We conclude that, at the neural level, olfactory impairment due to head trauma is best characterized by heightened responses and differential connectivity in higher-order areas beyond olfactory cortex.

scholarly journals Characterizing functional pathways of the human olfactory system

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Guangyu Zhou ◽  
Gregory Lane ◽  
Shiloh L Cooper ◽  
Thorsten Kahnt ◽  
Christina Zelano
Keyword(s):  
Functional Connectivity ◽  
Olfactory System ◽  
Large Scale ◽  
Brain Structures ◽  
Olfactory Cortex ◽  
Data Set ◽  
Whole Brain ◽  
Central Processing ◽  
Primary Olfactory Cortex ◽  
Processing Pathways

The central processing pathways of the human olfactory system are not fully understood. The olfactory bulb projects directly to a number of cortical brain structures, but the distinct networks formed by projections from each of these structures to the rest of the brain have not been well-defined. Here, we used functional magnetic resonance imaging and k-means clustering to parcellate human primary olfactory cortex into clusters based on whole-brain functional connectivity patterns. Resulting clusters accurately corresponded to anterior olfactory nucleus, olfactory tubercle, and frontal and temporal piriform cortices, suggesting dissociable whole-brain networks formed by the subregions of primary olfactory cortex. This result was replicated in an independent data set. We then characterized the unique functional connectivity profiles of each subregion, producing a map of the large-scale processing pathways of the human olfactory system. These results provide insight into the functional and anatomical organization of the human olfactory system.

scholarly journals 50 years of decoding olfaction

2018 ◽  
Vol 2 ◽  
pp. 239821281881749 ◽  
Author(s):  
Peter A Brennan
Keyword(s):  
Olfactory Bulb ◽  
Olfactory System ◽  
Piriform Cortex ◽  
Vomeronasal System ◽  
Main Olfactory Bulb ◽  
Late 20Th Century ◽  
Fundamental Insight ◽  
Main Olfactory System ◽  
G Protein Coupled

The identification, in the late 20th century, of unexpectedly large families of G-protein-coupled chemosensory receptors revolutionised our understanding of the olfactory system. The discovery that non-selective olfactory sensory neurons express a single olfactory receptor type and project to a specific glomerulus in the main olfactory bulb provided fundamental insight into the spatial pattern of odour representation in the main olfactory bulb. Studies using head-fixed awake mice and optogenetics have revealed the importance of the timing of glomerular input in relation to the sniff cycle and the role of piriform cortex in odour object recognition. What in the 1970s had appeared to be a relatively simple dichotomy between odour detection by the main olfactory system and pheromone detection by the vomeronasal system has been found to consist of multiple subsystems. These mediate innate responses to odours and pheromones and to substances as diverse as O2, volatile urinary constituents, peptides and proteins.

scholarly journals The causal role of auditory cortex in auditory working memory

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Liping Yu ◽  
Jiawei Hu ◽  
Chenlin Shi ◽  
Li Zhou ◽  
Maozhi Tian ◽  
...  
Keyword(s):  
Working Memory ◽  
Auditory Cortex ◽  
Neural Activity ◽  
Functional Role ◽  
Delay Period ◽  
Causal Role ◽  
Information Encoding ◽  
Electrophysiological Recordings ◽  
Sensory Cortices

Working memory (WM), the ability to actively hold information in memory over a delay period of seconds, is a fundamental constituent of cognition. Delay-period activity in sensory cortices has been observed in WM tasks, but whether and when the activity plays a functional role for memory maintenance remains unclear. Here we investigated the causal role of auditory cortex (AC) for memory maintenance in mice performing an auditory WM task. Electrophysiological recordings revealed that AC neurons were active not only during the presentation of the auditory stimulus but also early in the delay period. Furthermore, optogenetic suppression of neural activity in AC during the stimulus epoch and early delay period impaired WM performance, whereas suppression later in the delay period did not. Thus, AC is essential for information encoding and maintenance in auditory WM task, especially during the early delay period.

scholarly journals Dynamic representation of taste-related decisions in the gustatory insular cortex of mice

2019 ◽  
Author(s):  
Roberto Vincis ◽  
Ke Chen ◽  
Lindsey Czarnecki ◽  
John Chen ◽  
Alfredo Fontanini
Keyword(s):  
Decision Making ◽  
Insular Cortex ◽  
Sampling Period ◽  
Delay Period ◽  
Dynamic Representation ◽  
Electrophysiological Recordings ◽  
Sensory Cortices ◽  
Alternative Choice ◽  
Temporal Windows

SUMMARYResearch over the past decade has established the gustatory insular cortex (GC) as a model for studying how primary sensory cortices integrate multiple sensory, affective and cognitive signals. This integration occurs through time varying patterns of neural activity. Selective silencing of GC activity during specific temporal windows provided evidence for GC’s role in mediating taste palatability and expectation. Recent results also suggest that this area may play a role in decision making. However, existing data are limited to GC involvement in controlling the timing of stereotyped, orofacial reactions to aversive tastants during consumption. Here we present electrophysiological, chemogenetic and optogenetic results demonstrating the key role of GC in the execution of a taste-guided, reward-directed decision making task. Mice were trained in a taste-based, two-alternative choice task, in which they had to associate tastants sampled from a central spout with different actions (i.e., licking either a left or a right spout). Stimulus sampling and action were separated by a delay period. Electrophysiological recordings of single units revealed chemosensory processing during the sampling period and the emergence of task-related, cognitive signals during the delay period. Chemogenetic silencing of GC impaired task performance. Optogenetic silencing of GC allowed us to tease apart the contribution of activity during the sampling and the delay periods. While silencing during the sampling period had no effect, silencing during the delay period significantly impacted behavioral performance, demonstrating the importance of the cognitive signals processed by GC during this temporal window in driving decision making.Altogether, our data highlight a novel role of GC in controlling taste-guided, reward-directed choices and actions.

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