scholarly journals Parallel processing by distinct classes of principal neurons in the olfactory cortex

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Shivathmihai Nagappan ◽  
Kevin M Franks
Keyword(s):  
Parallel Processing ◽  
Olfactory Bulb ◽  
Neural Circuit ◽  
Olfactory Cortex ◽  
Local Connectivity ◽  
Biophysical Properties ◽  
Associative Cortex ◽  
Odor Processing ◽  
Parallel Channels ◽  
Response Discriminability

Understanding how distinct neuron types in a neural circuit process and propagate information is essential for understanding what the circuit does and how it does it. The olfactory (piriform, PCx) cortex contains two main types of principal neurons, semilunar (SL) and superficial pyramidal (PYR) cells. SLs and PYRs have distinct morphologies, local connectivity, biophysical properties, and downstream projection targets. Odor processing in PCx is thought to occur in two sequential stages. First, SLs receive and integrate olfactory bulb input and then PYRs receive, transform, and transmit SL input. To test this model, we recorded from populations of optogenetically identified SLs and PYRs in awake, head-fixed mice. Notably, silencing SLs did not alter PYR odor responses, and SLs and PYRs exhibited differences in odor tuning properties and response discriminability that were consistent with their distinct embeddings within a sensory-associative cortex. Our results therefore suggest that SLs and PYRs form parallel channels for differentially processing odor information in and through PCx.

scholarly journals Parallel processing by distinct classes of principal neurons in the olfactory cortex

2021 ◽  
Author(s):  
Shivathmihai Nagappan ◽  
Kevin Franks
Keyword(s):  
Parallel Processing ◽  
Olfactory Bulb ◽  
Neural Circuit ◽  
Olfactory Cortex ◽  
Biophysical Properties ◽  
Odor Processing ◽  
Evoked Activity ◽  
Two Stages

Understanding the specific roles that different neuron types play within a neural circuit is essential for understanding what that circuit does and how it does it. The primary olfactory (piriform, PCx) cortex contains two main types of principal neurons: semilunar (SL) and pyramidal (PYR). SLs and PYRs have different morphologies, connectivity, biophysical properties, and downstream projections, predicting distinct roles in cortical odor processing. The prevailing model is that odor processing in PCx occurs in two stages, where SLs are the primary recipients of olfactory bulb (OB) input, and PYRs receive and transform information from SLs. Here we recorded from optogenetically-identified SLs and PYRs in awake, head-fixed mice. We found differences in SL and PYR odor-evoked activity that reflect their different connectivity profiles. But SL responses did not precede PYR responses and suppressing SL activity had little effect on PYR odor responses. These results suggest that SLs and PYRs form parallel odor processing channels.

scholarly journals Excitability of Neural Activity is Enhanced, but Neural Discrimination of Odors is Slightly Decreased, in the Olfactory Bulb of Fasted Mice

Genes ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 433 ◽  
Author(s):  
Jing Wu ◽  
Penglai Liu ◽  
Fengjiao Chen ◽  
Lingying Ge ◽  
Yifan Lu ◽  
...  
Keyword(s):  
Olfactory Bulb ◽  
Neural Activity ◽  
Neural Circuit ◽  
Field Potential ◽  
Gamma Oscillations ◽  
Odor Processing ◽  
Fasted State ◽  
New Information ◽  
Tufted Cells ◽  
Olfactory Abilities

Olfaction and satiety status influence each other: cues from the olfactory system modulate eating behavior, and satiety affects olfactory abilities. However, the neural mechanisms governing the interactions between olfaction and satiety are unknown. Here, we investigate how an animal’s nutritional state modulates neural activity and odor representation in the mitral/tufted cells of the olfactory bulb, a key olfactory center that plays important roles in odor processing and representation. At the single-cell level, we found that the spontaneous firing rate of mitral/tufted cells and the number of cells showing an excitatory response both increased when mice were in a fasted state. However, the neural discrimination of odors slightly decreased. Although ongoing baseline and odor-evoked beta oscillations in the local field potential in the olfactory bulb were unchanged with fasting, the amplitude of odor-evoked gamma oscillations significantly decreased in a fasted state. These neural changes in the olfactory bulb were independent of the sniffing pattern, since both sniffing frequency and mean inhalation duration did not change with fasting. These results provide new information toward understanding the neural circuit mechanisms by which olfaction is modulated by nutritional status.

Retronasal Smell

Neuroenology ◽  
2016 ◽  
pp. 128-134
Author(s):  
Gordon M. Shepherd
Keyword(s):  
Olfactory Bulb ◽  
Olfactory Receptors ◽  
Olfactory Cortex ◽  
Initial Experience

We compare the initial experience of the aroma of the wine in the glass with the experience of the retronasal aroma as it contributes to the full flavor of the wine in the mouth and throat. We discuss the controversy over whether retronasal smell is less sensitive than orthonasal smell, and what could be the reasons. The processing of retronasal smell images is described from the olfactory receptors to the olfactory bulb, olfactory cortex, and highest cortical levels.

Parallel Tufted Cell and Mitral Cell Pathways from the Olfactory Bulb to the Olfactory Cortex

2014 ◽  
pp. 133-160 ◽  
Author(s):  
Shin Nagayama ◽  
Kei M. Igarashi ◽  
Hiroyuki Manabe ◽  
Kensaku Mori
Keyword(s):  
Olfactory Bulb ◽  
Mitral Cell ◽  
Olfactory Cortex ◽  
Tufted Cell

Disorders of the Cranial Nerves and Brainstem

2021 ◽  
pp. 851-861
Author(s):  
Kelly D. Flemming
Keyword(s):  
Olfactory Bulb ◽  
Olfactory Receptor ◽  
Cranial Nerves ◽  
Olfactory Nerve ◽  
Mitral Cell ◽  
Olfactory Cortex ◽  
Olfactory Receptor Cells ◽  
Receptor Cells ◽  
Clinical Disorders ◽  
Primary Olfactory Cortex

This chapter briefly repeats key anatomic characteristics and then reviews clinical disorders affecting each cranial nerve in addition to the brainstem. More specifically, this chapter covers cranial nerves I, V, VII, and IX through XII plus the brainstem. The olfactory nerve is a special visceral afferent nerve that functions in the sense of smell. The axons of the olfactory receptor cells within the nasal cavity extend through the cribriform plate to the olfactory bulb. These olfactory receptor cell axons synapse with mitral cells in the olfactory bulb. Mitral cell axons project to the primary olfactory cortex and amygdala. The olfactory cortex interconnects with various autonomic and visceral centers.

scholarly journals Th17 lymphocytes drive vascular and neuronal deficits in a mouse model of postinfectious autoimmune encephalitis

2020 ◽  
Vol 117 (12) ◽  
pp. 6708-6716 ◽  
Author(s):  
Maryann P. Platt ◽  
Kevin A. Bolding ◽  
Charlotte R. Wayne ◽  
Sarah Chaudhry ◽  
Tyler Cutforth ◽  
...  
Keyword(s):  
Microglial Activation ◽  
Neural Circuit ◽  
Psychiatric Symptoms ◽  
Neuropsychiatric Symptoms ◽  
Autoimmune Encephalitis ◽  
Abrupt Onset ◽  
Synaptic Proteins ◽  
Excitatory Synapses ◽  
Odor Processing ◽  
Th17 Lymphocytes

Antibodies against neuronal receptors and synaptic proteins are associated with a group of ill-defined central nervous system (CNS) autoimmune diseases termed autoimmune encephalitides (AE), which are characterized by abrupt onset of seizures and/or movement and psychiatric symptoms. Basal ganglia encephalitis (BGE), representing a subset of AE syndromes, is triggered in children by repeated group AStreptococcus(GAS) infections that lead to neuropsychiatric symptoms. We have previously shown that multiple GAS infections of mice induce migration of Th17 lymphocytes from the nose into the brain, causing blood–brain barrier (BBB) breakdown, extravasation of autoantibodies into the CNS, and loss of excitatory synapses within the olfactory bulb (OB). Whether these pathologies induce functional olfactory deficits, and the mechanistic role of Th17 lymphocytes, is unknown. Here, we demonstrate that, whereas loss of excitatory synapses in the OB is transient after multiple GAS infections, functional deficits in odor processing persist. Moreover, mice lacking Th17 lymphocytes have reduced BBB leakage, microglial activation, and antibody infiltration into the CNS, and have their olfactory function partially restored. Th17 lymphocytes are therefore critical for selective CNS entry of autoantibodies, microglial activation, and neural circuit impairment during postinfectious BGE.

scholarly journals Recurrent cortical circuits implement concentration-invariant odor coding

Science ◽  
2018 ◽  
Vol 361 (6407) ◽  
pp. eaat6904 ◽  
Author(s):  
Kevin A. Bolding ◽  
Kevin M. Franks
Keyword(s):  
Olfactory Bulb ◽  
Concentration Dependence ◽  
Neural Circuit ◽  
Feedback Inhibition ◽  
Piriform Cortex ◽  
Cortical Activity ◽  
Cortical Circuits ◽  
Odor Coding ◽  
Recurrent Collateral ◽  
The Impact

Animals rely on olfaction to find food, attract mates, and avoid predators. To support these behaviors, they must be able to identify odors across different odorant concentrations. The neural circuit operations that implement this concentration invariance remain unclear. We found that despite concentration-dependence in the olfactory bulb (OB), representations of odor identity were preserved downstream, in the piriform cortex (PCx). The OB cells responding earliest after inhalation drove robust responses in sparse subsets of PCx neurons. Recurrent collateral connections broadcast their activation across the PCx, recruiting global feedback inhibition that rapidly truncated and suppressed cortical activity for the remainder of the sniff, discounting the impact of slower, concentration-dependent OB inputs. Eliminating recurrent collateral output amplified PCx odor responses rendered the cortex steeply concentration-dependent and abolished concentration-invariant identity decoding.

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