The organization of centrifugal projections from the anterior olfactory nucleus, ventral hippocampal rudiment, and piriform cortex to the main olfactory bulb in the hamster: An autoradiographic study

Odorants, inhaled through the nose or exhaled from the mouth through the nose, bind to receptors on olfactory sensory neurons. Olfactory sensory neurons project in a highly stereotyped fashion into the forebrain to a structure called the olfactory bulb, where odorant-specific spatial patterns of neural activity are evoked. These patterns appear to reflect the molecular features of the inhaled stimulus. The olfactory bulb, in turn, projects to the olfactory cortex, which is composed of multiple sub-units including the anterior olfactory nucleus, the olfactory tubercle, the cortical nucleus of the amygdala, the anterior and posterior piriform cortex, and the lateral entorhinal cortex. Due to differences in olfactory bulb inputs, local circuitry and other factors, each of these cortical sub-regions appears to contribute to different aspects of the overall odor percept. For example, there appears to be some spatial organization of olfactory bulb inputs to the cortical nucleus of the amygdala, and this region may be involved in the expression of innate odor hedonic preferences. In contrast, the olfactory bulb projection to the piriform cortex is highly distributed and not spatially organized, allowing the piriform to function as a combinatorial, associative array, producing the emergence of experience-dependent odor-objects (e.g., strawberry) from the molecular features extracted in the periphery. Thus, the full perceptual experience of an odor requires involvement of a large, highly dynamic cortical network.

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Habituation of Odor Responses in the Rat Anterior Piriform Cortex

Journal of Neurophysiology ◽

10.1152/jn.1998.79.3.1425 ◽

1998 ◽

Vol 79 (3) ◽

pp. 1425-1440 ◽

Cited By ~ 136

Author(s):

Donald A. Wilson

Keyword(s):

Olfactory Bulb ◽

Respiration Rate ◽

Single Unit ◽

Piriform Cortex ◽

Firing Frequency ◽

Respiratory Cycle ◽

Intracellular Recordings ◽

Main Olfactory Bulb ◽

Anterior Piriform Cortex ◽

Initial Basis

Wilson, Donald A. Habituation of odor responses in the rat anterior piriform cortex. J. Neurophysiol. 79: 1425–1440, 1998. Simultaneous recordings of main olfactory bulb (MOB) and anterior piriform cortex (aPCX) neuron responses to repeated and prolonged odor pulses were examined in freely breathing, urethan-anesthetized rats. Comparisons of odor responses were made between multi-unit recordings of MOB activity and single-unit extracellular and intracellular recordings of Layer II/III aPCX neurons. Odor stimuli consisted of either 2-s pulses repeated at 30-s intervals or a single, prolonged 50-s stimulus. Respiration rate was monitored throughout. MOB and aPCX neuron responses to odor were quantified both through firing frequency and through the temporal patterning of firing over the respiratory cycle. The results demonstrate that aPCX neurons habituate significantly more (faster) than MOB neurons with both repeated and prolonged stimulation paradigms. This enhanced habituation is expressed as both a decrease in aPCX firing despite maintained odor-evoked MOB input and as a decrease in aPCX respiratory cycle entrainment despite maintained MOB cyclic input. Intracellular aPCX recordings suggest that several mechanisms may be involved in this experience-induced change in aPCX function, including 1) decreased excitatory driveof aPCX neurons, 2) decreased excitability of aPCX neurons,and/or 3) enhancement in odor-evoked inhibition of aPCX neurons. These studies provide the initial basis for understanding the mechanisms of nonassociative plasticity in olfactory cortex.

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Functional ultrasound imaging reveals different odor-evoked patterns of vascular activity in the main olfactory bulb and the anterior piriform cortex

NeuroImage ◽

10.1016/j.neuroimage.2014.03.054 ◽

2014 ◽

Vol 95 ◽

pp. 176-184 ◽

Cited By ~ 36

Author(s):

B.F. Osmanski ◽

C. Martin ◽

G. Montaldo ◽

P. Lanièce ◽

F. Pain ◽

...

Keyword(s):

Olfactory Bulb ◽

Ultrasound Imaging ◽

Piriform Cortex ◽

Main Olfactory Bulb ◽

Anterior Piriform Cortex ◽

Vascular Activity

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Topographic organization of connections between the main olfactory bulb and pars externa of the anterior olfactory nucleus in the hamster

The Journal of Comparative Neurology ◽

10.1002/cne.902270113 ◽

1984 ◽

Vol 227 (1) ◽

pp. 121-135 ◽

Cited By ~ 86

Author(s):

Thomas A. Schoenfeld ◽

Foteos Macrides

Keyword(s):

Olfactory Bulb ◽

Main Olfactory Bulb ◽

Anterior Olfactory Nucleus ◽

Topographic Organization

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The anterior olfactory nucleus is an important relay point connecting the main olfactory bulb and the amygdala in social buffering

Neuroscience Research ◽

10.1016/j.neures.2011.07.1686 ◽

2011 ◽

Vol 71 ◽

pp. e384

Author(s):

Yasushi Kiyokawa ◽

Yukari Takeuchi ◽

Yuji Mori

Keyword(s):

Olfactory Bulb ◽

Main Olfactory Bulb ◽

Anterior Olfactory Nucleus ◽

Social Buffering

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50 years of decoding olfaction

Brain and Neuroscience Advances ◽

10.1177/2398212818817496 ◽

2018 ◽

Vol 2 ◽

pp. 239821281881749 ◽

Cited By ~ 1

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.

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