1
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Federman N, Romano SA, Amigo-Duran M, Salomon L, Marin-Burgin A. Acquisition of non-olfactory encoding improves odour discrimination in olfactory cortex. Nat Commun 2024; 15:5572. [PMID: 38956072 PMCID: PMC11220071 DOI: 10.1038/s41467-024-49897-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Accepted: 06/20/2024] [Indexed: 07/04/2024] Open
Abstract
Olfaction is influenced by contextual factors, past experiences, and the animal's internal state. Whether this information is integrated at the initial stages of cortical odour processing is not known, nor how these signals may influence odour encoding. Here we revealed multiple and diverse non-olfactory responses in the primary olfactory (piriform) cortex (PCx), which dynamically enhance PCx odour discrimination according to behavioural demands. We performed recordings of PCx neurons from mice trained in a virtual reality task to associate odours with visual contexts to obtain a reward. We found that learning shifts PCx activity from encoding solely odours to a regime in which positional, contextual, and associative responses emerge on odour-responsive neurons that become mixed-selective. The modulation of PCx activity by these non-olfactory signals was dynamic, improving odour decoding during task engagement and in rewarded contexts. This improvement relied on the acquired mixed-selectivity, demonstrating how integrating extra-sensory inputs in sensory cortices can enhance sensory processing while encoding the behavioural relevance of stimuli.
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Grants
- 108878 Canadian International Development Agency (Agence Canadienne de Développement International)
- PICT2018-0880 Ministry of Science, Technology and Productive Innovation, Argentina | National Agency for Science and Technology, Argentina | Fondo para la Investigación Científica y Tecnológica (Fund for Scientific and Technological Research)
- PICT2020-0360 Ministry of Science, Technology and Productive Innovation, Argentina | National Agency for Science and Technology, Argentina | Fondo para la Investigación Científica y Tecnológica (Fund for Scientific and Technological Research)
- PICT2020-1536 Ministry of Science, Technology and Productive Innovation, Argentina | National Agency for Science and Technology, Argentina | Fondo para la Investigación Científica y Tecnológica (Fund for Scientific and Technological Research)
- PICT2016-2758 Ministry of Science, Technology and Productive Innovation, Argentina | National Agency for Science and Technology, Argentina | Fondo para la Investigación Científica y Tecnológica (Fund for Scientific and Technological Research)
- PICT2017-4023 Ministry of Science, Technology and Productive Innovation, Argentina | National Agency for Science and Technology, Argentina | Fondo para la Investigación Científica y Tecnológica (Fund for Scientific and Technological Research)
- PIP2787 Ministerio de Ciencia, Tecnología e Innovación Productiva (Ministry of Science, Technology and Productive Innovation, Argentina)
- SPIRIT 216044 Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung (Swiss National Science Foundation)
- Fondo para la convergencia estructural del Mercosur–FOCEM grant cOF 03/11
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Affiliation(s)
- Noel Federman
- Instituto de Investigación en Biomedicina de Buenos Aires (IBioBA)-CONICET-Partner Institute of the Max Planck Society, Godoy Cruz 2390, C1425FQD, Buenos Aires, Argentina.
| | - Sebastián A Romano
- Instituto de Investigación en Biomedicina de Buenos Aires (IBioBA)-CONICET-Partner Institute of the Max Planck Society, Godoy Cruz 2390, C1425FQD, Buenos Aires, Argentina.
| | - Macarena Amigo-Duran
- Instituto de Investigación en Biomedicina de Buenos Aires (IBioBA)-CONICET-Partner Institute of the Max Planck Society, Godoy Cruz 2390, C1425FQD, Buenos Aires, Argentina
- Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, PhD Program, Buenos Aires, Argentina
| | - Lucca Salomon
- Instituto de Investigación en Biomedicina de Buenos Aires (IBioBA)-CONICET-Partner Institute of the Max Planck Society, Godoy Cruz 2390, C1425FQD, Buenos Aires, Argentina
- Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, PhD Program, Buenos Aires, Argentina
| | - Antonia Marin-Burgin
- Instituto de Investigación en Biomedicina de Buenos Aires (IBioBA)-CONICET-Partner Institute of the Max Planck Society, Godoy Cruz 2390, C1425FQD, Buenos Aires, Argentina.
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2
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Zhang Y, Roy DS. Memory Storage in Distributed Engram Cell Ensembles. ADVANCES IN NEUROBIOLOGY 2024; 38:29-43. [PMID: 39008009 DOI: 10.1007/978-3-031-62983-9_3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/16/2024]
Abstract
One of the most fascinating aspects of the brain is its ability to acquire new information from experience and retain it over time as memory. The search for physical correlates of memory, the memory engram, has been a longstanding priority in modern neurobiology. Advanced genetic approaches have led to the localization of engram cells in a few brain regions, including the hippocampus and cortex. Additionally, engram cells exhibit learning-induced, persistent modifications and have at least two states, active and silent. However, it has been hypothesized that engrams for a specific memory are distributed among multiple brain regions that are functionally connected, referred to as a unified engram complex. Recent tissue-clearing techniques have permitted high-throughput analyses of intact brain samples, which have been used to obtain a map of the engram complex for a contextual fear memory. Careful examination of these engram complex maps has revealed a potentially underappreciated contribution of subcortical regions, specifically thalamic nuclei, to memory function. These more holistic studies support the unified engram complex hypothesis for memory storage and have important implications for understanding dysfunctional engrams in the context of human disease.
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Affiliation(s)
- Ying Zhang
- Center for Life Sciences & IDG/McGovern Institute for Brain Research, School of Life Sciences, Tsinghua University, Haidian District, Beijing, China
| | - Dheeraj S Roy
- Department of Physiology and Biophysics, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, USA.
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3
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Colombel N, Ferreira G, Sullivan RM, Coureaud G. Dynamic developmental changes in neurotransmitters supporting infant attachment learning. Neurosci Biobehav Rev 2023; 151:105249. [PMID: 37257712 PMCID: PMC10754360 DOI: 10.1016/j.neubiorev.2023.105249] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Revised: 05/15/2023] [Accepted: 05/26/2023] [Indexed: 06/02/2023]
Abstract
Infant survival relies on rapid identification, remembering and behavioral responsiveness to caregivers' sensory cues. While neural circuits supporting infant attachment learning have largely remained elusive in children, use of invasive techniques has uncovered some of its features in rodents. During a 10-day sensitive period from birth, newborn rodents associate maternal odors with maternal pleasant or noxious thermo-tactile stimulation, which gives rise to a preference and approach behavior towards these odors, and blockade of avoidance learning. Here we review the neural circuitry supporting this neonatal odor learning, unique compared to adults, focusing specifically on the early roles of neurotransmitters such as glutamate, GABA (Gamma-AminoButyric Acid), serotonin, dopamine and norepinephrine, in the olfactory bulb, the anterior piriform cortex and amygdala. The review highlights the importance of deepening our knowledge of age-specific infant brain neurotransmitters and behavioral functioning that can be translated to improve the well-being of children during typical development and aid in treatment during atypical development in childhood clinical practice, and the care during rearing of domestic animals.
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Affiliation(s)
- Nina Colombel
- Ecole Normale Supérieure de Lyon, Lyon 1 Claude Bernard University, Lyon, France
| | - Guillaume Ferreira
- FoodCircus group, NutriNeuro Lab, INRAE 1286, Bordeaux University, Bordeaux, France
| | - Regina M Sullivan
- Emotional Brain Institute, The Nathan Kline Institute, Orangeburg, NY, USA; Child and Adolescent Psychiatry, New York University Langone Medical Center, New York, USA
| | - Gérard Coureaud
- Sensory NeuroEthology Group, Lyon Neuroscience Research Center, INSERM U1028, CNRS UMR 5292, Lyon 1 University, Jean-Monnet University, Bron, France.
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4
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Roy DS, Park YG, Kim ME, Zhang Y, Ogawa SK, DiNapoli N, Gu X, Cho JH, Choi H, Kamentsky L, Martin J, Mosto O, Aida T, Chung K, Tonegawa S. Brain-wide mapping reveals that engrams for a single memory are distributed across multiple brain regions. Nat Commun 2022; 13:1799. [PMID: 35379803 PMCID: PMC8980018 DOI: 10.1038/s41467-022-29384-4] [Citation(s) in RCA: 64] [Impact Index Per Article: 32.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Accepted: 03/10/2022] [Indexed: 11/28/2022] Open
Abstract
Neuronal ensembles that hold specific memory (memory engrams) have been identified in the hippocampus, amygdala, or cortex. However, it has been hypothesized that engrams of a specific memory are distributed among multiple brain regions that are functionally connected, referred to as a unified engram complex. Here, we report a partial map of the engram complex for contextual fear conditioning memory by characterizing encoding activated neuronal ensembles in 247 regions using tissue phenotyping in mice. The mapping was aided by an engram index, which identified 117 cFos+ brain regions holding engrams with high probability, and brain-wide reactivation of these neuronal ensembles by recall. Optogenetic manipulation experiments revealed engram ensembles, many of which were functionally connected to hippocampal or amygdala engrams. Simultaneous chemogenetic reactivation of multiple engram ensembles conferred a greater level of memory recall than reactivation of a single engram ensemble, reflecting the natural memory recall process. Overall, our study supports the unified engram complex hypothesis for memory storage.
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Affiliation(s)
- Dheeraj S Roy
- RIKEN-MIT Laboratory for Neural Circuit Genetics at the Picower Institute for Learning and Memory, Department of Biology and Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.
- Broad Institute of MIT and Harvard, Cambridge, MA, 02142, USA.
| | - Young-Gyun Park
- Institute for Medical Engineering and Science, Picower Institute for Learning and Memory, Department of Chemical Engineering and Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
- Department of Bio and Brain Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, South Korea
| | - Minyoung E Kim
- Institute for Medical Engineering and Science, Picower Institute for Learning and Memory, Department of Chemical Engineering and Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Ying Zhang
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Sachie K Ogawa
- RIKEN-MIT Laboratory for Neural Circuit Genetics at the Picower Institute for Learning and Memory, Department of Biology and Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
- Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Nicholas DiNapoli
- Institute for Medical Engineering and Science, Picower Institute for Learning and Memory, Department of Chemical Engineering and Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Xinyi Gu
- Institute for Medical Engineering and Science, Picower Institute for Learning and Memory, Department of Chemical Engineering and Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Jae H Cho
- Institute for Medical Engineering and Science, Picower Institute for Learning and Memory, Department of Chemical Engineering and Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Heejin Choi
- Institute for Medical Engineering and Science, Picower Institute for Learning and Memory, Department of Chemical Engineering and Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Lee Kamentsky
- Institute for Medical Engineering and Science, Picower Institute for Learning and Memory, Department of Chemical Engineering and Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Jared Martin
- RIKEN-MIT Laboratory for Neural Circuit Genetics at the Picower Institute for Learning and Memory, Department of Biology and Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Olivia Mosto
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Tomomi Aida
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Kwanghun Chung
- Broad Institute of MIT and Harvard, Cambridge, MA, 02142, USA.
- Institute for Medical Engineering and Science, Picower Institute for Learning and Memory, Department of Chemical Engineering and Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.
- Yonsei-IBS Institute, Yonsei University, Seoul, 03722, Republic of Korea.
| | - Susumu Tonegawa
- RIKEN-MIT Laboratory for Neural Circuit Genetics at the Picower Institute for Learning and Memory, Department of Biology and Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.
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5
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Tavoni G, Kersen DEC, Balasubramanian V. Cortical feedback and gating in odor discrimination and generalization. PLoS Comput Biol 2021; 17:e1009479. [PMID: 34634035 PMCID: PMC8530364 DOI: 10.1371/journal.pcbi.1009479] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2021] [Revised: 10/21/2021] [Accepted: 09/24/2021] [Indexed: 11/30/2022] Open
Abstract
A central question in neuroscience is how context changes perception. In the olfactory system, for example, experiments show that task demands can drive divergence and convergence of cortical odor responses, likely underpinning olfactory discrimination and generalization. Here, we propose a simple statistical mechanism for this effect based on unstructured feedback from the central brain to the olfactory bulb, which represents the context associated with an odor, and sufficiently selective cortical gating of sensory inputs. Strikingly, the model predicts that both convergence and divergence of cortical odor patterns should increase when odors are initially more similar, an effect reported in recent experiments. The theory in turn predicts reversals of these trends following experimental manipulations and in neurological conditions that increase cortical excitability.
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Affiliation(s)
- Gaia Tavoni
- Computational Neuroscience Initiative, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- Department of Neuroscience, Washington University in St. Louis, St. Louis, Missouri, United States of America
| | - David E. Chen Kersen
- Computational Neuroscience Initiative, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- Department of Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Vijay Balasubramanian
- Computational Neuroscience Initiative, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- Department of Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- Department of Neuroscience, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
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6
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Nartey MN, Peña-Castillo L, LeGrow M, Doré J, Bhattacharya S, Darby-King A, Carew SJ, Yuan Q, Harley CW, McLean JH. Learning-induced mRNA alterations in olfactory bulb mitral cells in neonatal rats. ACTA ACUST UNITED AC 2020; 27:209-221. [PMID: 32295841 PMCID: PMC7164515 DOI: 10.1101/lm.051177.119] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2019] [Accepted: 02/11/2020] [Indexed: 12/20/2022]
Abstract
In the olfactory bulb, a cAMP/PKA/CREB-dependent form of learning occurs in the first week of life that provides a unique mammalian model for defining the epigenetic role of this evolutionarily ancient plasticity cascade. Odor preference learning in the week-old rat pup is rapidly induced by a 10-min pairing of odor and stroking. Memory is demonstrable at 24 h, but not 48 h, posttraining. Using this paradigm, pups that showed peppermint preference 30 min posttraining were sacrificed 20 min later for laser microdissection of odor-encoding mitral cells. Controls were given odor only. Microarray analysis revealed that 13 nonprotein-coding mRNAs linked to mRNA translation and splicing and 11 protein-coding mRNAs linked to transcription differed with odor preference training. MicroRNA23b, a translation inhibitor of multiple plasticity-related mRNAs, was down-regulated. Protein-coding transcription was up-regulated for Sec23b, Clic2, Rpp14, Dcbld1, Magee2, Mstn, Fam229b, RGD1566265, and Mgst2. Gng12 and Srcg1 mRNAs were down-regulated. Increases in Sec23b, Clic2, and Dcbld1 proteins were confirmed in mitral cells in situ at the same time point following training. The protein-coding changes are consistent with extracellular matrix remodeling and ryanodine receptor involvement in odor preference learning. A role for CREB and AP1 as triggers of memory-related mRNA regulation is supported. The small number of gene changes identified in the mitral cell input/output link for 24 h memory will facilitate investigation of the nature, and reversibility, of changes supporting temporally restricted long-term memory.
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Affiliation(s)
- Michaelina N Nartey
- Divison of Biomedical Sciences, Memorial University of Newfoundland, St. John's, Newfoundland A1B3V6, Canada
| | - Lourdes Peña-Castillo
- Department of Computer Science, Memorial University of Newfoundland, St. John's, Newfoundland A1B3X5, Canada
| | - Megan LeGrow
- Divison of Biomedical Sciences, Memorial University of Newfoundland, St. John's, Newfoundland A1B3V6, Canada
| | - Jules Doré
- Divison of Biomedical Sciences, Memorial University of Newfoundland, St. John's, Newfoundland A1B3V6, Canada
| | - Sriya Bhattacharya
- Divison of Biomedical Sciences, Memorial University of Newfoundland, St. John's, Newfoundland A1B3V6, Canada
| | - Andrea Darby-King
- Divison of Biomedical Sciences, Memorial University of Newfoundland, St. John's, Newfoundland A1B3V6, Canada
| | - Samantha J Carew
- Divison of Biomedical Sciences, Memorial University of Newfoundland, St. John's, Newfoundland A1B3V6, Canada
| | - Qi Yuan
- Divison of Biomedical Sciences, Memorial University of Newfoundland, St. John's, Newfoundland A1B3V6, Canada
| | - Carolyn W Harley
- Department of Psychology, Memorial University of Newfoundland, St. John's, Newfoundland A1B3X9, Canada
| | - John H McLean
- Divison of Biomedical Sciences, Memorial University of Newfoundland, St. John's, Newfoundland A1B3V6, Canada
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7
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Frank T, Mönig NR, Satou C, Higashijima SI, Friedrich RW. Associative conditioning remaps odor representations and modifies inhibition in a higher olfactory brain area. Nat Neurosci 2019; 22:1844-1856. [PMID: 31591559 PMCID: PMC6858881 DOI: 10.1038/s41593-019-0495-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Accepted: 08/09/2019] [Indexed: 11/30/2022]
Abstract
Intelligent behavior involves associations between high-dimensional sensory representations and behaviorally relevant qualities such as valence. Learning of associations involves plasticity of excitatory connectivity but it remains poorly understood how information flow is reorganized in networks and how inhibition contributes to this process. We trained adult zebrafish in an appetitive odor discrimination task and analyzed odor representations in a specific compartment of telencephalic area Dp, the homolog of olfactory cortex. Associative conditioning enhanced responses with a preference for the positively conditioned odor (CS+). Moreover, conditioning systematically remapped odor representations along an axis in coding space that represented attractiveness (valence). Inter-individual variations in this mapping predicted variations in behavioral odor preference. Photoinhibition of interneurons resulted in specific modifications of odor representations that mirrored effects of conditioning and reduced experience-dependent, inter-individual variations in odor-valence mapping. These results reveal an individualized odor-to-valence map that is shaped by inhibition and reorganized during learning.
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Affiliation(s)
- Thomas Frank
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland.
| | - Nila R Mönig
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Chie Satou
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - Shin-Ichi Higashijima
- National Institutes of Natural Sciences, Exploratory Research Center on Life and Living Systems, National Institute for Basic Biology, Okazaki, Japan
| | - Rainer W Friedrich
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland. .,University of Basel, Basel, Switzerland.
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8
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Carew SJ, Mukherjee B, MacIntyre ITK, Ghosh A, Li S, Kirouac GJ, Harley CW, Yuan Q. Pheromone-Induced Odor Associative Fear Learning in Rats. Sci Rep 2018; 8:17701. [PMID: 30532054 PMCID: PMC6286391 DOI: 10.1038/s41598-018-36023-w] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Accepted: 11/14/2018] [Indexed: 12/02/2022] Open
Abstract
Alarm pheromones alert conspecifics to the presence of danger. Can pheromone communication aid in learning specific cues? Such facilitation has an evident evolutionary advantage. We use two associative learning paradigms to test this hypothesis. The first is stressed cage mate-induced conditioning. One pair-housed adult rat received 4 pairings of terpinene + shock over 30 min. Ten minutes after return to the home cage, its companion rat was removed and exposed to terpinene. Single-housed controls were exposed to either terpinene or shock only. Companion rats showed terpinene-specific freezing, which was prevented by β-adrenoceptor blockade. Using Arc to index neuronal activation in response to terpinene re-exposure, stressed cage-mate induced associative learning was measured. Companion rats showed increased neuronal activity in the accessory olfactory bulb, while terpinene + shock-conditioned rats showed increased activity in the main olfactory bulb. Both groups had enhanced activity in the anterior basolateral amygdala and central amygdala. To test involvement of pheromone mediation, in the 2nd paradigm, we paired terpinene with soiled bedding from odor + shock rats or a rat alarm pheromone. Both conditioning increased rats’ freezing to terpinene. Blocking NMDA receptors in the basolateral amygdala prevented odor-specific learning suggesting shock and pheromone-paired pathways converge in the amygdala. An alarm pheromone thus enables cue-specific learning as well as signalling danger.
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Affiliation(s)
- Samantha J Carew
- Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, A1B 3V6, Canada
| | - Bandhan Mukherjee
- Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, A1B 3V6, Canada
| | - Iain T K MacIntyre
- Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, A1B 3V6, Canada
| | - Abhinaba Ghosh
- Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, A1B 3V6, Canada
| | - Sa Li
- Department of Oral Biology and Psychiatry, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, R3E 0W2, Canada
| | - Gilbert J Kirouac
- Department of Oral Biology and Psychiatry, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, R3E 0W2, Canada
| | - Carolyn W Harley
- Psychology Department, Faculty of Science, Memorial University of Newfoundland, St. John's, A1B 3X9, Canada
| | - Qi Yuan
- Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, A1B 3V6, Canada.
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9
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Ikeda K, Suzuki N, Bekkers JM. Sodium and potassium conductances in principal neurons of the mouse piriform cortex: a quantitative description. J Physiol 2018; 596:5397-5414. [PMID: 30194865 DOI: 10.1113/jp275824] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Accepted: 08/21/2018] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS The primary olfactory (or piriform) cortex is a promising model system for understanding how the cerebral cortex processes sensory information, although an investigation of the piriform cortex is hindered by a lack of detailed information about the intrinsic electrical properties of its component neurons. In the present study, we quantify the properties of voltage-dependent sodium currents and voltage- and calcium-dependent potassium currents in two important classes of excitatory neurons in the main input layer of the piriform cortex. We identify several classes of these currents and show that their properties are similar to those found in better-studied cortical regions. Our detailed quantitative descriptions of these currents will be valuable to computational neuroscientists who aim to build models that explain how the piriform cortex encodes odours. ABSTRACT The primary olfactory cortex (or piriform cortex, PC) is an anatomically simple palaeocortex that is increasingly used as a model system for investigating cortical sensory processing. However, little information is available on the intrinsic electrical conductances in neurons of the PC, hampering efforts to build realistic computational models of this cortex. In the present study, we used nucleated macropatches and whole-cell recordings to rigorously quantify the biophysical properties of voltage-gated sodium (NaV ), voltage-gated potassium (KV ) and calcium-activated potassium (KCa ) conductances in two major classes of glutamatergic neurons in layer 2 of the PC, semilunar (SL) cells and superficial pyramidal (SP) cells. We found that SL and SP cells both express a fast-inactivating NaV current, two types of KV current (A-type and delayed rectifier-type) and three types of KCa current (fast-, medium- and slow-afterhyperpolarization currents). The kinetic and voltage-dependent properties of the NaV and KV conductances were, with some exceptions, identical in SL and SP cells and similar to those found in neocortical pyramidal neurons. The KCa conductances were also similar across the different types of neurons. Our results are summarized in a series of empirical equations that should prove useful to computational neuroscientists seeking to model the PC. More broadly, our findings indicate that, at the level of single-cell electrical properties, this palaeocortex is not so different from the neocortex, vindicating efforts to use the PC as a model of cortical sensory processing in general.
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Affiliation(s)
- Kaori Ikeda
- Eccles Institute of Neuroscience, John Curtin School of Medical Research, The Australian National University, Canberra, ACT, Australia
| | | | - John M Bekkers
- Eccles Institute of Neuroscience, John Curtin School of Medical Research, The Australian National University, Canberra, ACT, Australia
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10
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Beukema P, Cecil KL, Peterson E, Mann VR, Matsushita M, Takashima Y, Navlakha S, Barth AL. TrpM8-mediated somatosensation in mouse neocortex. J Comp Neurol 2018; 526:1444-1456. [PMID: 29484652 PMCID: PMC5899639 DOI: 10.1002/cne.24418] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Revised: 02/06/2018] [Accepted: 02/12/2018] [Indexed: 12/29/2022]
Abstract
Somatosensation is a complex sense mediated by more than a dozen distinct neural subtypes in the periphery. Although pressure and touch sensation have been mapped to primary somatosensory cortex in rodents, it has been controversial whether pain and temperature inputs are also directed to this area. Here we use a well-defined somatosensory modality, cool sensation mediated by peripheral TrpM8-receptors, to investigate the neural substrate for cool perception in the mouse neocortex. Using activation of cutaneous TrpM8 receptor-expressing neurons, we identify candidate neocortical areas responsive for cool sensation. Initially, we optimized TrpM8 stimulation and determined that menthol, a selective TrpM8 agonist, was more effective than cool stimulation at inducing expression of the immediate-early gene c-fos in the spinal cord. We developed a broad-scale brain survey method for identification of activated brain areas, using automated methods to quantify c-fos immunoreactivity (fos-IR) across animals. Brain areas corresponding to the posterior insular cortex and secondary somatosensory (S2) show elevated fos-IR after menthol stimulation, in contrast to weaker activation in primary somatosensory cortex (S1). In addition, menthol exposure triggered fos-IR in piriform cortex, the amygdala, and the hypothalamus. Menthol-mediated activation was absent in TrpM8-knock-out animals. Our results indicate that cool somatosensory input broadly drives neural activity across the mouse brain, with neocortical signal most elevated in the posterior insula, as well as S2 and S1. These findings are consistent with data from humans indicating that the posterior insula is specialized for somatosensory information encoding temperature, pain, and gentle touch.
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Affiliation(s)
- Patrick Beukema
- Department of Neuroscience, Center for Neuroscience at the University of Pittsburgh, Pittsburgh, Pennsylvania, 15260
| | | | - Elena Peterson
- Department of Psychology, University of California, Los Angeles, Los Angeles, CA, 90095
| | - Victor R Mann
- Department of Chemistry, University of California, Berkeley, California, 94720
| | - Megumi Matsushita
- Department of Biological Sciences and Center for the Neural Basis of Cognition, Carnegie Mellon University, Pittsburgh, Pennsylvania, 15213
| | - Yoshio Takashima
- Department of Psychology, University of California, Los Angeles, Los Angeles, CA, 90095
| | - Saket Navlakha
- Integrative Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, California, 92037
| | - Alison L Barth
- Department of Biological Sciences and Center for the Neural Basis of Cognition, Carnegie Mellon University, Pittsburgh, Pennsylvania, 15213
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11
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Mukherjee B, Harley CW, Yuan Q. Learning-Induced Metaplasticity? Associative Training for Early Odor Preference Learning Down-Regulates Synapse-Specific NMDA Receptors via mGluR and Calcineurin Activation. Cereb Cortex 2018; 27:616-624. [PMID: 26503266 DOI: 10.1093/cercor/bhv256] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Rat pups readily form a 24-h associative odor preference after a single trial of odor paired with intermittent stroking. Recent evidence shows that this training trial, which normally increases AMPA receptor responses in the anterior piriform cortex both 3 and 24 h following training, induces a down-regulation of NMDA receptors 3 h later followed by NMDA receptor up-regulation at 24 h. When retrained with the same odor at 3 h, rat pups unlearn the original odor preference. Unlearning can be prevented by blocking NMDA receptors during retraining. Here, the mechanisms that initiate NMDA receptor down-regulation are assessed. Blocking mGluR receptors or calcineurin during training prevents down-regulation of NMDA receptors 3 h following training. Blocking NMDA receptors during training does not affect NMDA receptor down-regulation. Thus, down-regulation can be engaged separately from associative learning. When unlearning occurs, AMPA and NMDA receptor levels at 24 h are reset to control levels. Calcineurin blockade during retraining prevents unlearning consistent with the role of NMDA receptor down-regulation. The relationship of these events to the metaplasticity and plasticity mechanisms of long-term depression and depotentiation is discussed. We suggest a possible functional role of NMDA receptor down-regulation in offline stabilization of learned odor representations.
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Affiliation(s)
| | - Carolyn W Harley
- Department of Psychology, Faculty of Science, Memorial University of Newfoundland, St. John's, NL, Canada
| | - Qi Yuan
- Division of Biomedical Sciences, Faculty of Medicine
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12
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Piriform cortical glutamatergic and GABAergic neurons express coordinated plasticity for whisker-induced odor recall. Oncotarget 2017; 8:95719-95740. [PMID: 29221161 PMCID: PMC5707055 DOI: 10.18632/oncotarget.21207] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2017] [Accepted: 08/17/2017] [Indexed: 12/15/2022] Open
Abstract
Neural plasticity occurs in learning and memory. Coordinated plasticity at glutamatergic and GABAergic neurons during memory formation remains elusive, which we investigate in a mouse model of associative learning by cellular imaging and electrophysiology. Paired odor and whisker stimulations lead to whisker-induced olfaction response. In mice that express this cross-modal memory, the neurons in the piriform cortex are recruited to encode newly acquired whisker signal alongside innate odor signal, and their response patterns to these associated signals are different. There are emerged synaptic innervations from barrel cortical neurons to piriform cortical neurons from these mice. These results indicate the recruitment of associative memory cells in the piriform cortex after associative memory. In terms of the structural and functional plasticity at these associative memory cells in the piriform cortex, glutamatergic neurons and synapses are upregulated, GABAergic neurons and synapses are downregulated as well as their mutual innervations are refined in the coordinated manner. Therefore, the associated activations of sensory cortices triggered by their input signals induce the formation of their mutual synapse innervations, the recruitment of associative memory cells and the coordinated plasticity between the GABAergic and glutamatergic neurons, which work for associative memory cells to encode cross-modal associated signals in their integration, associative storage and distinguishable retrieval.
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13
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Experience-Dependent Plasticity in Accessory Olfactory Bulb Interneurons following Male-Male Social Interaction. J Neurosci 2017; 37:7240-7252. [PMID: 28659282 DOI: 10.1523/jneurosci.1031-17.2017] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2017] [Revised: 06/01/2017] [Accepted: 06/22/2017] [Indexed: 12/19/2022] Open
Abstract
Chemosensory information processing in the mouse accessory olfactory system guides the expression of social behavior. After salient chemosensory encounters, the accessory olfactory bulb (AOB) experiences changes in the balance of excitation and inhibition at reciprocal synapses between mitral cells (MCs) and local interneurons. The mechanisms underlying these changes remain controversial. Moreover, it remains unclear whether MC-interneuron plasticity is unique to specific behaviors, such as mating, or whether it is a more general feature of the AOB circuit. Here, we describe targeted electrophysiological studies of AOB inhibitory internal granule cells (IGCs), many of which upregulate the immediate-early gene Arc after male-male social experience. Following the resident-intruder paradigm, Arc-expressing IGCs in acute AOB slices from resident males displayed stronger excitation than nonexpressing neighbors when sensory inputs were stimulated. The increased excitability of Arc-expressing IGCs was not correlated with changes in the strength or number of excitatory synapses with MCs but was instead associated with increased intrinsic excitability and decreased HCN channel-mediated IH currents. Consistent with increased inhibition by IGCs, MCs responded to sensory input stimulation with decreased depolarization and spiking following resident-intruder encounters. These results reveal that nonmating behaviors drive AOB inhibitory plasticity and indicate that increased MC inhibition involves intrinsic excitability changes in Arc-expressing interneurons.SIGNIFICANCE STATEMENT The accessory olfactory bulb (AOB) is a site of experience-dependent plasticity between excitatory mitral cells (MCs) and inhibitory internal granule cells (IGCs), but the physiological mechanisms and behavioral conditions driving this plasticity remain unclear. Here, we report studies of AOB neuronal plasticity following male-male social chemosensory encounters. We show that the plasticity-associated immediate-early gene Arc is selectively expressed in IGCs from resident males following the resident-intruder assay. After behavior, Arc-expressing IGCs are more strongly excited by sensory input stimulation and MC activation is suppressed. Arc-expressing IGCs do not show increased excitatory synaptic drive but instead show increased intrinsic excitability. These data indicate that MC-IGC plasticity is induced after male-male social chemosensory encounters, resulting in enhanced MC suppression by Arc-expressing IGCs.
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14
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Hill ES, Vasireddi SK, Wang J, Bruno AM, Frost WN. Watching a memory form-VSD imaging reveals a novel memory mechanism. Commun Integr Biol 2016; 9:e1212142. [PMID: 28003862 PMCID: PMC5154357 DOI: 10.1080/19420889.2016.1212142] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Accepted: 07/06/2016] [Indexed: 11/30/2022] Open
Abstract
Studies of the mechanisms underlying memory formation have largely focused on the
synapse. However, recent evidence suggests that additional, non-synaptic, mechanisms also
play important roles in this process. We recently described a novel memory mechanism
whereby a particular class of neurons was recruited into the Tritonia
escape swim network with sensitization, a non-associative form of learning. Neurons that
in the naïve state were loosely-affiliated with the network were rapidly recruited
in, transitioning from variably bursting (VB) to reliably bursting (RB). Even after the
memory had faded some new neurons remained, and some original members had left, leaving
the network in an altered state. Further, we identified a candidate cellular mechanism
underlying these network changes. Our study supports the view that brain networks may have
surprisingly fluid functional structures and adds to the growing body of evidence that
non-synaptic mechanisms often operate synergistically with changes at the synapse to
mediate memory formation.
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Affiliation(s)
- Evan S Hill
- Department of Cell Biology and Anatomy, Rosalind Franklin University , North Chicago, IL, USA
| | - Sunil K Vasireddi
- Department of Cell Biology and Anatomy, Rosalind Franklin University , North Chicago, IL, USA
| | - Jean Wang
- Department of Cell Biology and Anatomy, Rosalind Franklin University , North Chicago, IL, USA
| | - Angela M Bruno
- Department of Cell Biology and Anatomy, Rosalind Franklin University, North Chicago, IL, USA; Department of Neuroscience, Rosalind Franklin University, North Chicago, IL, USA
| | - William N Frost
- Department of Cell Biology and Anatomy, Rosalind Franklin University , North Chicago, IL, USA
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15
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Modarresi S, Mukherjee B, McLean JH, Harley CW, Yuan Q. CaMKII mediates stimulus specificity in early odor preference learning in rats. J Neurophysiol 2016; 116:404-10. [PMID: 27121578 DOI: 10.1152/jn.00176.2016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Accepted: 04/27/2016] [Indexed: 01/20/2023] Open
Abstract
After naturalistic odor preference training, Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) was rapidly phosphorylated in the olfactory bulb, specifically in the odor encoding regions of the glomerular layer and external plexiform layer. Intrabulbar CaMKII antagonist experiments revealed that CaMKII supports short- and long-term preference memory formation. With bulbar PKA activation as the unconditioned stimulus odor preferences could be induced despite CaMKII blockade, but now odor specificity was lost, with odor preference generalizing to an untrained odor. Odor-specific learning was associated with increased membrane-associated AMPA receptors, while nonspecific odor preference was not. Thus CaMKII activation provides a tag to confer stimulus specificity as well as supporting natural odor preference learning.
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Affiliation(s)
- Shirin Modarresi
- Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, Newfoundland, Canada; and
| | - Bandhan Mukherjee
- Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, Newfoundland, Canada; and
| | - John H McLean
- Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, Newfoundland, Canada; and
| | - Carolyn W Harley
- Department of Psychology, Faculty of Science, Memorial University of Newfoundland, St. John's, Newfoundland, Canada
| | - Qi Yuan
- Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, Newfoundland, Canada; and
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16
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Arc-Expressing Neuronal Ensembles Supporting Pattern Separation Require Adrenergic Activity in Anterior Piriform Cortex: An Exploration of Neural Constraints on Learning. J Neurosci 2016; 35:14070-5. [PMID: 26468206 DOI: 10.1523/jneurosci.2690-15.2015] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED Arc ensembles in adult rat olfactory bulb (OB) and anterior piriform cortex (PC) were assessed after discrimination training on highly similar odor pairs. Nonselective α- and β-adrenergic antagonists or saline were infused in the OB or anterior PC during training. OB adrenergic blockade slowed, but did not prevent, odor discrimination learning. After criterion performance, Arc ensembles in anterior piriform showed enhanced stability for the rewarded odor and pattern separation for the discriminated odors as described previously. Anterior piriform adrenergic blockade prevented acquisition of similar odor discrimination and of OB ensemble changes, even with extended overtraining. Mitral and granule cell Arc ensembles in OB showed enhanced stability for rewarded odor only in the saline group. Pattern separation was not seen in the OB. Similar odor discrimination co-occurs with increased stability in rewarded odor representations and pattern separation to reduce encoding overlap. The difficulty of similar discriminations may relate to the necessity to both strengthen rewarded representations and weaken overlap across similar representations. SIGNIFICANCE STATEMENT We show for the first time that adrenoceptors in anterior piriform cortex (aPC) must be engaged for adult rats to learn to discriminate highly similar odors. Loss of adrenergic activation in olfactory bulb (OB) slows, but does not prevent, discrimination learning. Both increased stability of the rewarded odor representation and increased pattern separation of the rewarded and unrewarded odors in aPC accompany successful discrimination. In the OB, rewarded odors increase in ensemble stability, but there is no evidence of pattern separation. We suggest that the slow acquisition of similar odor discriminations is related to the differing plasticity requirements for increased stability and pattern separation.
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17
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Ghosh A, Purchase NC, Chen X, Yuan Q. Norepinephrine Modulates Pyramidal Cell Synaptic Properties in the Anterior Piriform Cortex of Mice: Age-Dependent Effects of β-adrenoceptors. Front Cell Neurosci 2015; 9:450. [PMID: 26635530 PMCID: PMC4652601 DOI: 10.3389/fncel.2015.00450] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Accepted: 11/02/2015] [Indexed: 12/31/2022] Open
Abstract
Early odor preference learning in rodents occurs within a sensitive period [≤postnatal day (P)10–12], during which pups show a heightened ability to form an odor preference when a novel odor is paired with a tactile stimulation (e.g., stroking). Norepinephrine (NE) release from the locus coeruleus during stroking mediates this learning. However, in older pups, stroking loses its ability to induce learning. The cellular and circuitry mechanisms underpinning the sensitive period for odor preference learning is not well understood. We first established the sensitive period learning model in mice – odor paired with stroking induced odor preference in P8 but not P14 mice. This learning was dependent on NE-β-adrenoceptors as it was prevented by propranolol injection prior to training. We then tested whether there are developmental changes in pyramidal cell excitability and NE responsiveness in the anterior piriform cortex (aPC) in mouse pups. Although significant differences of pyramidal cell intrinsic properties were found in two age groups (P8–11 and P14+), NE at two concentrations (0.1 and 10 μM) did not alter intrinsic properties in either group. In contrast, in P8–11 pups, NE at 0.1 μM presynaptically decreased miniature IPSC and increased miniature EPSC frequencies. These effects were reversed with a higher dose of NE (10 μM), suggesting involvement of different adrenoceptor subtypes. In P14+ pups, NE at higher doses (1 and 10 μM) acted both pre- and postsynaptically to promote inhibition. These results suggest that enhanced synaptic excitation and reduced inhibition by NE in the aPC network may underlie the sensitive period.
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Affiliation(s)
- Abhinaba Ghosh
- Division of BioMedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's NL, Canada
| | - Nicole C Purchase
- Division of BioMedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's NL, Canada
| | - Xihua Chen
- Division of BioMedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's NL, Canada
| | - Qi Yuan
- Division of BioMedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's NL, Canada
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18
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de Almeida L, Reiner SJ, Ennis M, Linster C. Computational modeling suggests distinct, location-specific function of norepinephrine in olfactory bulb and piriform cortex. Front Comput Neurosci 2015; 9:73. [PMID: 26136678 PMCID: PMC4468384 DOI: 10.3389/fncom.2015.00073] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2015] [Accepted: 05/27/2015] [Indexed: 12/02/2022] Open
Abstract
Noradrenergic modulation from the locus coerulus is often associated with the regulation of sensory signal-to-noise ratio. In the olfactory system, noradrenergic modulation affects both bulbar and cortical processing, and has been shown to modulate the detection of low concentration stimuli. We here implemented a computational model of the olfactory bulb and piriform cortex, based on known experimental results, to explore how noradrenergic modulation in the olfactory bulb and piriform cortex interact to regulate odor processing. We show that as predicted by behavioral experiments in our lab, norepinephrine can play a critical role in modulating the detection and associative learning of very low odor concentrations. Our simulations show that bulbar norepinephrine serves to pre-process odor representations to facilitate cortical learning, but not recall. We observe the typical non-uniform dose—response functions described for norepinephrine modulation and show that these are imposed mainly by bulbar, but not cortical processing.
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Affiliation(s)
- Licurgo de Almeida
- Computational Physiology Lab, Department of Neurobiology and Behavior, Cornell University Ithaca, NY, USA
| | - Seungdo J Reiner
- Computational Physiology Lab, Department of Neurobiology and Behavior, Cornell University Ithaca, NY, USA
| | - Matthew Ennis
- Computational Physiology Lab, Department of Neurobiology and Behavior, Cornell University Ithaca, NY, USA
| | - Christiane Linster
- Computational Physiology Lab, Department of Neurobiology and Behavior, Cornell University Ithaca, NY, USA
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19
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Yuan Q, Harley CW. Learning modulation of odor representations: new findings from Arc-indexed networks. Front Cell Neurosci 2015; 8:423. [PMID: 25565958 PMCID: PMC4271698 DOI: 10.3389/fncel.2014.00423] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2014] [Accepted: 11/23/2014] [Indexed: 11/13/2022] Open
Abstract
We first review our understanding of odor representations in rodent olfactory bulb (OB) and anterior piriform cortex (APC). We then consider learning-induced representation changes. Finally we describe the perspective on network representations gained from examining Arc-indexed odor networks of awake rats. Arc-indexed networks are sparse and distributed, consistent with current views. However Arc provides representations of repeated odors. Arc-indexed repeated odor representations are quite variable. Sparse representations are assumed to be compact and reliable memory codes. Arc suggests this is not necessarily the case. The variability seen is consistent with electrophysiology in awake animals and may reflect top-down cortical modulation of context. Arc-indexing shows that distinct odors share larger than predicted neuron pools. These may be low-threshold neuronal subsets. Learning’s effect on Arc-indexed representations is to increase the stable or overlapping component of rewarded odor representations. This component can decrease for similar odors when their discrimination is rewarded. The learning effects seen are supported by electrophysiology, but mechanisms remain to be elucidated.
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Affiliation(s)
- Qi Yuan
- Division of Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland St. John's, NL, Canada
| | - Carolyn W Harley
- Department of Psychology, Faculty of Science, Memorial University of Newfoundland St. John's, NL, Canada
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