scholarly journals Opposing spatial gradients of inhibition and neural activity in mouse olfactory cortex

2017 ◽  
Author(s):  
Adam M. Large ◽  
Nathan W. Vogler ◽  
Martha Canto-Bustos ◽  
Paul Schick ◽  
Anne-Marie M. Oswald
Keyword(s):  
Sensory Processing ◽  
Neural Activity ◽  
Spatial Representation ◽  
Piriform Cortex ◽  
Pyramidal Cells ◽  
Spatial Gradients ◽  
Anterior Piriform Cortex ◽  
Odor Processing ◽  
Somatostatin Cells ◽  
Sensory Cortices

AbstractThe spatial representation of stimuli in primary sensory cortices is a convenient scaffold for elucidating the circuit mechanisms underlying sensory processing. In contrast, the anterior piriform cortex (APC) lacks topology for odor identity and appears homogenous in terms of afferent and intracortical excitatory circuitry. Here, we show that an increasing rostral-caudal (RC) gradient of inhibition onto pyramidal cells is commensurate with a decrease in active neurons along the RC axis following exploration of a novel odor environment. This inhibitory gradient is supported by somatostatin interneurons that provide an opposing, rostrally-biased, gradient of inhibition to interneurons. Optogenetic or chemogenetic modulation of somatostatin cells neutralizes the inhibitory gradient onto pyramidal cells. This suggests a novel circuit mechanism whereby opposing spatial gradients of inhibition and disinhibition regulate neural activity along the RC-axis. These findings challenge our current understanding of the spatial profiles of neural circuits and odor processing within APC.

scholarly journals Differential inhibition of pyramidal cells and inhibitory interneurons along the rostrocaudal axis of anterior piriform cortex

2018 ◽  
Vol 115 (34) ◽  
pp. E8067-E8076 ◽  
Author(s):  
Adam M. Large ◽  
Nathan W. Vogler ◽  
Martha Canto-Bustos ◽  
F. Kathryn Friason ◽  
Paul Schick ◽  
...  
Keyword(s):  
Sensory Processing ◽  
Spatial Representation ◽  
Piriform Cortex ◽  
Pyramidal Cells ◽  
Inhibitory Neurons ◽  
Gabaergic Interneurons ◽  
Inhibitory Circuits ◽  
Anterior Piriform Cortex ◽  
Odor Processing ◽  
Spatial Asymmetries

The spatial representation of stimuli in sensory neocortices provides a scaffold for elucidating circuit mechanisms underlying sensory processing. However, the anterior piriform cortex (APC) lacks topology for odor identity as well as afferent and intracortical excitation. Consequently, olfactory processing is considered homogenous along the APC rostral–caudal (RC) axis. We recorded excitatory and inhibitory neurons in APC while optogenetically activating GABAergic interneurons along the RC axis. In contrast to excitation, we find opposing, spatially asymmetric inhibition onto pyramidal cells (PCs) and interneurons. PCs are strongly inhibited by caudal stimulation sites, whereas interneurons are strongly inhibited by rostral sites. At least two mechanisms underlie spatial asymmetries. Enhanced caudal inhibition of PCs is due to increased synaptic strength, whereas rostrally biased inhibition of interneurons is mediated by increased somatostatin–interneuron density. Altogether, we show differences in rostral and caudal inhibitory circuits in APC that may underlie spatial variation in odor processing along the RC axis.

scholarly journals Maturation of pyramidal cells in anterior piriform cortex may be sufficient to explain the end of early olfactory learning in rats

2019 ◽  
Vol 27 (1) ◽  
pp. 20-32 ◽  
Author(s):  
Enver Miguel Oruro ◽  
Grace V.E. Pardo ◽  
Aldo B. Lucion ◽  
Maria Elisa Calcagnotto ◽  
Marco A. P. Idiart
Keyword(s):  
Piriform Cortex ◽  
Pyramidal Cells ◽  
Olfactory Learning ◽  
Anterior Piriform Cortex

scholarly journals Quantitative analysis of axon collaterals of single pyramidal cells of the anterior piriform cortex of the guinea pig

2017 ◽  
Vol 18 (1) ◽  
Author(s):  
Junli Yang ◽  
Gerhard Litscher ◽  
Zhongren Sun ◽  
Qiang Tang ◽  
Kiyoshi Kishi ◽  
...  
Keyword(s):  
Quantitative Analysis ◽  
Guinea Pig ◽  
Piriform Cortex ◽  
Pyramidal Cells ◽  
Anterior Piriform Cortex ◽  
Axon Collaterals

scholarly journals Insulin Modulates Neural Activity of Pyramidal Neurons in the Anterior Piriform Cortex

2017 ◽  
Vol 11 ◽  
Author(s):  
Yang Zhou ◽  
Xiaojie Wang ◽  
Tiantian Cao ◽  
Jinshan Xu ◽  
Dejuan Wang ◽  
...  
Keyword(s):  
Neural Activity ◽  
Pyramidal Neurons ◽  
Piriform Cortex ◽  
Anterior Piriform Cortex

scholarly journals Increased pattern similarity in two major olfactory cortices despite higher sparseness levels

2021 ◽  
Author(s):  
Chaviva Markind ◽  
Prosenjit Kundu ◽  
Mor Barak ◽  
Rafi Haddad
Keyword(s):  
Activity Patterns ◽  
Piriform Cortex ◽  
List Type ◽  
Activity Levels ◽  
Anterior Piriform Cortex ◽  
Odor Processing ◽  
Pattern Similarity ◽  
Fundamental Process ◽  
Cortical Regions ◽  
Odor Representation

AbstractPattern separation is a fundamental process that enhances discrimination of similar stimuli and can be achieved by sparsening the neural activity and expanding the coding space. Odor stimuli evoke patterns of activity in the olfactory bulb (OB) and these activity patterns are projected to several cortical regions that contain larger numbers of neurons and show sparser activity levels. However, whether these projected patterns are better separated is still unclear. Here we compared odor responses in the OB, anterior piriform cortex (aPC) and anterior olfactory nucleus (AON) to the exact same odor stimuli. We found that odor representations are more similar, noisier and less distinctive in aPC and AON than in the OB. The increase in similarity was observed for both similar and dissimilar odors. Modeling odor transformation from the OB to the olfactory cortex using simulated as well as actual OB odor responses as inputs, demonstrates that the observed rise in odor representation similarity can be explained by assuming biologically plausible variation in the number of OB inputs each cortical neuron receives. We discuss the possible advantages of our findings to odor processing in the aPC and AON.HighlightsOdor representations in the aPC and AON are more correlated despite increase in sparseness levels.Odor identity is best represented in the OB.Variance in the number of inputs from OB can explain the reduction in odor separation.

scholarly journals Balanced feedforward inhibition and dominant recurrent inhibition in olfactory cortex

2016 ◽  
Vol 113 (8) ◽  
pp. 2276-2281 ◽  
Author(s):  
Adam M. Large ◽  
Nathan W. Vogler ◽  
Samantha Mielo ◽  
Anne-Marie M. Oswald
Keyword(s):  
Piriform Cortex ◽  
Intracortical Inhibition ◽  
Recurrent Inhibition ◽  
Inhibitory Input ◽  
Anterior Piriform Cortex ◽  
Intracortical Circuits ◽  
Cell Class ◽  
Ideal System ◽  
Inhibitory Strength ◽  
Sensory Cortices

Throughout the brain, the recruitment of feedforward and recurrent inhibition shapes neural responses. However, disentangling the relative contributions of these often-overlapping cortical circuits is challenging. The piriform cortex provides an ideal system to address this issue because the interneurons responsible for feedforward and recurrent inhibition are anatomically segregated in layer (L) 1 and L2/3 respectively. Here we use a combination of optical and electrical activation of interneurons to profile the inhibitory input received by three classes of principal excitatory neuron in the anterior piriform cortex. In all classes, we find that L1 interneurons provide weaker inhibition than L2/3 interneurons. Nonetheless, feedforward inhibitory strength covaries with the amount of afferent excitation received by each class of principal neuron. In contrast, intracortical stimulation of L2/3 evokes strong inhibition that dominates recurrent excitation in all classes. Finally, we find that the relative contributions of feedforward and recurrent pathways differ between principal neuron classes. Specifically, L2 neurons receive more reliable afferent drive and less overall inhibition than L3 neurons. Alternatively, L3 neurons receive substantially more intracortical inhibition. These three features—balanced afferent drive, dominant recurrent inhibition, and differential recruitment by afferent vs. intracortical circuits, dependent on cell class—suggest mechanisms for olfactory processing that may extend to other sensory cortices.

Odor Specificity of Habituation in the Rat Anterior Piriform Cortex

2000 ◽  
Vol 83 (1) ◽  
pp. 139-145 ◽  
Author(s):  
Donald A. Wilson
Keyword(s):  
Cortical Plasticity ◽  
Piriform Cortex ◽  
Afferent Input ◽  
Straight Chain ◽  
Anterior Piriform Cortex ◽  
Odor Processing ◽  
Before And After ◽  
Odor Mixtures ◽  
Evoked Activity ◽  
High Degree

Exposure to odorants results in a rapid (<10 s) reduction in odor-evoked activity in the rat piriform cortex despite relatively maintained afferent input from olfactory bulb mitral cells. To further understand this form of cortical plasticity, a detailed analysis of its odor specificity was performed. Habituation of odor responses in anterior piriform cortex single units was examined in anesthetized, freely breathing rats. The magnitude of single-unit responses of layer II/III neurons to 2-s odor pulses were examined before and after a 50-s habituating stimulus of either the same or different odor. The results demonstrated that odor habituation was odor specific, with no significant cross-habituation between either markedly different single odors or between odors within a series of straight chain alkanes. Furthermore, habituation to binary 1:1 mixtures produced minimal cross-habituation to the components of that mixture. These latter results may suggest synthetic odor processing in the olfactory system, with novel odor mixtures processed as unique stimuli. Potential mechanisms of odor habituation in the piriform cortex must be able to account for the high degree of specificity of this effect.

A study of the axon initial segment and proximal axon of neurons in the primate motor and somatic sensory cortices

1979 ◽  
Vol 285 (1006) ◽  
pp. 173-197 ◽  
Keyword(s):  
Initial Segment ◽  
Pyramidal Cells ◽  
Stellate Cells ◽  
Myelinated Axon ◽  
Full Length ◽  
Unmyelinated Axon ◽  
Parent Cell ◽  
Axon Terminals ◽  
Sensory Cortices ◽  
Axon Initial Segments

The axon initial segments of pyramidal cells and large and small stellate cells in the primate sensori-motor cortex have a typical membrane undercoating and bundles of neurotubules. Those of pyramidal cells are directed towards the white matter whereas those of large and small stellate cells often run obliquely or towards the cortical surface and may be curved. Cisternal organs in these initial segments are related to symmetrical axon terminals, frequently coming into close apposition to the non-synaptic part of these terminals adjacent to the synapse between the axon terminal and initial segment. The dense plates of cisternal organs and the membrane undercoating of the initial segment are specifically stained by ethanolic phosphotungstic acid (ethanolic PTA). Pyramidal initial segments have spines which receive only symmetrical synapses, as do the shafts of the initial segments of each cell type. The full length of the initial segment was studied for fourteen pyramidal and two large stellate cells. All gave rise to myelinated axons although two pyramidal cells had lengths of unmyelinated axon between the initial segment and myelinated axon. One of these lengths of unmyelinated axon made an asymmetric synapse on to a dendrite just after losing its initial segment features. Quantitative analysis of these complete initial segments showed that whereas the diameter of the initial segment and the axon it gave rise to were approximately proportional to the size of the parent cell soma over a considerable range of cell diameters, the length of the initial segment appeared to be unrelated to either its diameter or the size of its parent soma but varied between 30 and 55 μm apparently at random. Synapses were evenly distributed along the full length of the complete pyramidal initial segments, but the density of synapses on the initial segments of supragranular pyramids was about three times that on those of infragranular pyramids and cisternal organs were similarly more frequent in the initial segments of supragranular pyramids.

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