Olfactory bulb

BBSRC-funded postdoctoral project in Dr Jamie Johnston's lab investigating how the olfactory bulb, the first processing stage of the olfactory system, adjusts its encoding of odours in response to behavioural context. The fellow uses in vivo two-photon calcium imaging in mice, behavioural assays and computational modelling to track how learning-driven changes emerge in these early circuits and how they shape perception. The post sits in the School of Biomedical Sciences, Faculty of Biological Sciences, within a Leeds neuroscience community of more than 44 research labs. Grade 7, £41,064–£48,82

…and tufted cell (MTC) activity in the olfactory bulb. Yet, it remains unknown how sequential MTC activity is organized, and what role sequential activity plays in guiding perception. Here, we performed fast 2-photon calcium imaging of hundreds of MTCs with sub-sniff temporal resolution to a battery of odors. We constructed a space of MTC tuning using the pairwise correlations between

…nature and spatial organisation of the olfactory environment onto their temporal dynamics. Whilst insects and mammals alike can discern high-frequency information, how temporal properties of the olfactory environment are represented in the brain remains largely unknown. Here, we presented temporally rich and systematically varying odour stimuli whilst electrically recording from the output neuro

The mammalian olfactory system shows an exceptional ability for rapid and accurate decoding of both the identity and concentration of odorants. In a given scene, only a handful out of millions of possible odorants are present. Yet, the mammals can effectively distinguish these odorants using the dimensionally-reduced representation provided by olfactory receptor neurons. To account for this capability, normative compressed sensing models have been proposed by previous studies. However, these models do not map cleanly onto the unique anatomy and physiology of the olfactory bulb, nor have they d

Passive odor exposure can change olfactory perception beyond simple pattern separation. Recent studies reveal that principal neurons in the mouse olfactory bulb exhibit bi-directional changes in population- level representations that depend on input similarity. Our analysis reveals the presence of a systematic drift, manifested as rotation of population vectors away from their initial representations. We explain these phenomena using a recurrent inhibition feedback model with unsupervised Hebbian learning. Our model predicts a power- law decay in mean population activity over days of odor expo

…In the mammal olfactory system, the olfactory bulb (OB) and piriform cortex (PCx) are responsible for preliminary odor encoding and corresponding memory storage respectively. Recent evidence demonstrated the dynamic nature of OB and PCx odor representations upon frequent repetition of the same odors over days, and this phenomenon, termed representational drift, should be the consequence of highly plastic nature of biologically constrained synapses in the olfactory system. In this work, we buil

Understanding the neural mechanisms underlying odor representation and memory in the olfactory bulb (OB) is critical for advancing our knowledge of sensory processing and neural plasticity. Inspired by in vivo experimental findings [1, 2], we applied the eligibility propagation (e-prop) learning rule [3] to simulate the cholinergic and GABAergic responses to distinct odors. [1, 2] found differential activation patterns in glomeruli of the OB in response to different odor exposures. The modulation of activity by cholinergic and GABAergic projections from the horizontal diagonal band (HDB) was s

…dose of the olfactotoxin methimazole, olfactory sensory neurons in the nasal olfactory epithelium degener

…human alpha-synuclein into the olfactory bulb to trigger alpha-synucleinopathy in wildtype mice. Inoculums were obtained from post-mortem human temporal cortex tissues by sucrose gradient fractionation. C57Bl/6J male mice were inoculated with Lewy Body (LB)-containing fractions (hsyn+) from patients with idiopathic PD; control-injected mice were inoculated with non-LB PD fractions (hsyn-), aggregated non-toxic fractions from non-PD patients (hCtrl), or the corresponding vehicle (Veh). Mice were evaluate

Olfactory dysfunction is a common aspect of normal aging. It is also an early symptom of Alzheimer’s disease (AD). The olfactory bulb, the first processing station of olfactory information in the brain, receives cholinergic basal forebrain input, as does the neocortex and hippocampus contributing cognition and memory, respectively. This study aimed to clarify (1) the role of cholinergic input to the olfactory bulb in adult and aged rats, (2) the relationship between olfaction and cognitive function in older adults.In both adult and aged rats, under anesthesia, unilateral olfactory nerve stimul

…(LFP) within the rat olfactory bulb (OB) using a semi-intact, perfused nose-brain preparation, while monitoring the pressure pulsations induced by the peristaltic perfusion pump that in our setup operated within the physiological range of hea

Autism is a complex and heterogeneous neurodevelopmental condition. One of the major pathophysiological alterations in this disorder is an excitatory/inhibitory (E/I) neurotransmission imbalance. However, the underlying mechanisms of this imbalance remain poorly understood. The neuromodulator nitric oxide (NO) constitutively participates in E/I activity regulation by interacting with both glutamate and GABA. Little is known about how nitrergic system works in the autistic brain, although several studies suggest that dysregulations in this system may be involved in the pathogenesis of autism.We

Astrocytes, beyond their pivotal role as supporting cells, are recently considered to be dynamic modulators of neuronal activity and synaptic plasticity. This effect is mainly through their Ca2+ signaling cascades which result in a release of gliotransmitters. Glutamate as an important neurotransmitter which is crucial for many cognitive functions can modulate astrocytic Ca2+ signaling via their receptors. Considering that these processes have largely been studied in young animals, along with the association of aging with various diseases, this study aims to explore the age-dependent changes i

Food sensory perception has emerged as a potent regulator of specialized feeding circuits; yet, the consequences on feeding behaviour and the underlying neuronal basis remain poorly understood. Here, we reveal a sensory pathway that coordinately integrates food odours to control forthcoming nutrient intake. Unbiased whole-brain mapping of food odours-induced brain activity revealed a potent activation of the medial septum (MS), where food odours selectively activate MS glutamatergic neurons (MSVGLUT2). Characterization of the activity dynamics of MSVGLUT2 neurons uncovered a biphasic modulatio

In the olfactory system, the glomeruli of the olfactory bulb define the first synapse processing odour information in the brain. Here, many synapses are established between olfactory sensory neurons (OSNs) and olfactory bulb neurons. Xenopus tropicalis tadpoles provide an excellent experimental platform to investigate the molecular mechanisms of synaptic transmission in vivo due to its experimental accessibility and transparency. We investigated long-lasting depolarizations (LLDs) occurring in the glomerular layer of the olfactory bulb by measuring changes in the local field potential. We reco

…sensory network we focus on the olfactory bulb (OB) of larval zebrafish. The OB is optically accessible and sufficiently small to enable dense ultrastructural reconstructions of neuronal cir

…the cortex, the hippocampus, and the olfactory bulb (OB). Several evidence indicate that part of the ID-ASD pathology can be ascribed to defects in synaptic morphology and

…neurons and mitral cells of the olfactory bulb (OB). They are also defective in IGF1, but little is known about other neurotrophic factors, which may act as neuroprotective molecules.The expression of different neurotrophic factors (IGF1, BDNF, VEGF-A and VEGF-B) was analyzed by qPCR and ELISA around cerebellar and bulbar degenerations of PCD mice. Then, we applied two different therapies depending on the affected region.1. We refined healthy bone marrow transplants to reduce the degeneration of mitral cells. PCD mice were transplanted

Olfactory dysfunction is an early symptom of Alzheimer’s disease (AD). The olfactory bulb and neocortex receive cholinergic basal forebrain inputs which degenerate in AD patients. Nicotinic acetylcholine receptors (nAChRs) in the brain play a crucial role in vasodilation in the neocortex induced by basal forebrain cholinergic activation or nicotine injection. Information about the sense of smell is conveyed by the olfactory nerve, or by the intranasal trigeminal nerve when irritating odors. We recently reported that nicotine potentiates the olfactory bulb vasodilation induced by olfactory nerv

…and stimulus-evoked activity in the olfactory bulb (OB) boosts the oscillatory entrainment of the downstream lateral entorhinal cortex (LEC) and hippocampus (HP). The tight anatomical connections between olfactory system and higher-order neuronal circuits might implicate the functional impact of olfactory outputs on cognitive functions along brain development. However, it is unclear whether early OB activity h

Olfactory dysfunction is an early symptom of neurodegenerative diseases, including Parkinson’s disease (PD) and multiple sclerosis (MS). Recent data showed that 30-40% MS patients and 90 % PD patients experience olfactory dysfunction. Studies have shown that adenosine signaling has a pivotal role in olfactory processing; thus, deciphering the changes in adenosine signaling may be crucial for understanding the disease pathogenesis. Aim of this study was to characterize olfactory dysfunction from the aspect of adenosine metabolism, focusing on ecto-5’ nucleotidase (CD73) in the olfactory bulb (O

The loss of a sensory input leads to reorganization of neuronal networks in remaining sensory cortices, which results in functional improvements. This shows remarkable adaptability of the mammalian brain. It remains elusive whether a traumatic brain injury (TBI) in a sensory cortex results in similar functional reorganization in spared sensory networks. We herein investigated global alterations in neuronal activity maps in the mouse brain subjected to a TBI in the visual cortex and delved into the underlying cellular mechanisms. Our data shows substantial differences in brain activity maps 2-3

Olfactory ensheathing cells (OECs) transplantation is emerging as promising nerve repair therapy, particularly for spinal cord injury (SCI), owing to their intrinsic regenerative capacity within the olfactory system. Perineural fibroblasts are natural partners of OECs within the olfactory nerve and co-transplantation with OECs may improve transplantation repair outcomes. However, little is known about the natural interactions of OECs and fibroblasts during the chaotic state following an injury. Using a mouse model, we temporarily damaged the olfactory nerves using methimazole. At key stages of

…newly generated neurons in the local olfactory bulb circuit. However, the effects of opioids drugs on the olfactory perception have been scarce studied, although some data suggests that they interfere with olfactory function, and the underlying mechanisms are unknown. We have previously shown that the activation of the dopamine D4 receptor (D4R) prevents both morphine addiction -by modulating dopamine signaling from nigral dopamine cells- and the development of morphine-induced analgesic toler