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Yang CCH, Kuo TBJ, Chen CH, Li WY, Hung CT, Li JY. Older rats show slow modulation of hippocampal theta rhythm during voluntary running. Exp Gerontol 2023; 173:112092. [PMID: 36669709 DOI: 10.1016/j.exger.2023.112092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2022] [Revised: 12/18/2022] [Accepted: 01/16/2023] [Indexed: 01/19/2023]
Abstract
Aging causes brain function degeneration and slows many motor and behavioural responses. The hippocampal theta rhythm (4-12 Hz) is related to cognition and locomotion. However, the findings on aging-related changes in the frequency and amplitude of hippocampal theta oscillations have been inconsistent. We hypothesized that older rats have slower responses in terms of hippocampal theta rhythm during voluntary wheel running than do young adult rats. By simultaneously recording electroencephalography and physical activity (PA), we evaluated theta oscillations in 8-week-old (young adult) and 60-week-old (middle-aged) rats before and during wheel running, which was conducted only during the rats' 12-h dark period. To test the alterations of hippocampal theta rhythm in voluntary wheel running, we analyzed the signals without (8-s) or with (2-s) chronological order. No significant difference was observed in total frequency (TP, 4-12 Hz), low-frequency (LT, 4-6.5 Hz), or high-frequency (9.5-12 Hz) theta activity between active waking and overall running in either group. The theta oscillations were slower in the middle-aged rats than in the young adult rats during wheel running but increased during running for both age groups. During wheel running, the middle-aged rats exhibited an increased LT, which was related to PA. On the basis of the chronological order of running, the young adult rats exhibited increased TP, and the middle-aged rats exhibited significant increases in middle-frequency (MT, 6.5-9.5 Hz) theta activity. The dominant modulations of MT in the middle-aged rats may have caused nonsignificant changes in total activity. These between-group differences in theta rhythm characteristics during voluntary running provide insights into age-related brain function decline.
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Affiliation(s)
- Cheryl C H Yang
- Institute of Brain Science, National Yang Ming Chiao Tung University, Taipei, Taiwan; Sleep Research Center, National Yang Ming Chiao Tung University, Taipei, Taiwan; Department of Education and Research, Taipei City Hospital, Taipei, Taiwan; Brain Research Center, National Yang Ming Chiao Tung University, Taipei, Taiwan
| | - Terry B J Kuo
- Institute of Brain Science, National Yang Ming Chiao Tung University, Taipei, Taiwan; Sleep Research Center, National Yang Ming Chiao Tung University, Taipei, Taiwan; Department of Education and Research, Taipei City Hospital, Taipei, Taiwan; Clinical Research Center, Tsoutun Psychiatric Center, Ministry of Health and Welfare, Nantou, Taiwan
| | - Chun-Hsiu Chen
- Department of Health and Leisure Management, Yuanpei University of Medical Technology, Hsinchu, Taiwan
| | - Wei-Yi Li
- Institute of Brain Science, National Yang Ming Chiao Tung University, Taipei, Taiwan
| | - Chang-Tsen Hung
- Department of Health and Leisure Management, Yuanpei University of Medical Technology, Hsinchu, Taiwan
| | - Jia-Yi Li
- Sleep Research Center, National Yang Ming Chiao Tung University, Taipei, Taiwan; Department of Health and Leisure Management, Yuanpei University of Medical Technology, Hsinchu, Taiwan.
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2
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Solórzano Hernández E, Cervantes Alfaro JM, Figueroa Rosales R, Gutiérrez Guzmán BÉ, López Vázquez MÁ, Olvera Cortés ME. Septal medial/diagonal band of Broca citalopram infusion reduces place learning efficiency and alters septohippocampal theta learning-related activity in rats. Behav Brain Res 2022; 435:114056. [PMID: 35963580 DOI: 10.1016/j.bbr.2022.114056] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2022] [Revised: 08/08/2022] [Accepted: 08/09/2022] [Indexed: 11/26/2022]
Abstract
Increases in power and frequency of hippocampal theta activity have been related to efficient place learning and memory acquisition in hippocampal-dependent tests. The complex medial septum-diagonal band of Broca (MS/DBB) is the pacemaker of hippocampal theta activity, influenced by the ascending synchronizing system, and modulated by serotonergic raphe medial afferents, acting on cholinergic and GABAergic septal neurons. The suppression of hippocampal theta expression and the modulation of hippocampal learning and memory are attributed to serotonin. To simultaneously test these hypotheses, a daily local serotonin increase was induced by citalopram (CIT) infusion (100 µM, 0.88 µl, 0.2 µl/m) 15 min before training in the Morris water maze. The theta activity was recorded in the MS/DBB, dentate gyrus (DG) and CA1 of one group infused with artificial cerebrospinal liquid (ACL) and the other with CIT on Days 1-6 of training. After a probe trial (Day 7) and one resting day, the treatments were reversed (Days 8-11). The CIT MS/DBB infusion in the first 6 training days reduced the efficiency of spatial learning in association with reduced power in the DG, reduced MS/DBB-DG coherence, increased DG-CA1 coherence, and a lack of a negative correlation between MS/DBB power and swam distances. No effect of the CIT occurred once the information was acquired under ACL training. These results support a role of serotonin, in acting on the MS/DBB in the fine tuning of hippocampal learning and memory efficiency through the modulation of learning-related theta activity power and septohipocampal synchronization.
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Affiliation(s)
- Eduardo Solórzano Hernández
- Laboratorio de Neurociencias, División de Estudios de Posgrado, Facultad de Ciencias Médicas y Biológicas "Dr. Ignacio Chávez", Universidad Michoacana de San Nicolás de Hidalgo, Mexico; Laboratorio de Neurofisiología Experimental, División de Neurociencias, Centro de Investigación Biomédica de Michoacán, Instituto Mexicano del Seguro Social, Mexico.
| | - José Miguel Cervantes Alfaro
- Laboratorio de Neurociencias, División de Estudios de Posgrado, Facultad de Ciencias Médicas y Biológicas "Dr. Ignacio Chávez", Universidad Michoacana de San Nicolás de Hidalgo, Mexico.
| | - Rosalinda Figueroa Rosales
- Laboratorio de Neurofisiología Experimental, División de Neurociencias, Centro de Investigación Biomédica de Michoacán, Instituto Mexicano del Seguro Social, Mexico.
| | - Blanca Érika Gutiérrez Guzmán
- Laboratorio de Neurofisiología Experimental, División de Neurociencias, Centro de Investigación Biomédica de Michoacán, Instituto Mexicano del Seguro Social, Mexico.
| | - Miguel Ángel López Vázquez
- Laboratorio de Neuroplasticidad, División de Neurociencias, Centro de Investigación Biomédica de Michoacán, Instituto Mexicano del Seguro Social, Mexico.
| | - María Esther Olvera Cortés
- Laboratorio de Neurofisiología Experimental, División de Neurociencias, Centro de Investigación Biomédica de Michoacán, Instituto Mexicano del Seguro Social, Mexico.
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Blümel L, Brosda J, Bert B, Hamann M, Dietz GPH. Moderately aged OFA rats as a novel model for mild age-related alterations in learning and memory. Brain Cogn 2021; 154:105799. [PMID: 34543909 DOI: 10.1016/j.bandc.2021.105799] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Revised: 08/29/2021] [Accepted: 09/02/2021] [Indexed: 11/27/2022]
Abstract
Aged rodents have been used as preclinical models of age-associated cognitive decline. Most of those models displayed substantial impairments in learning and memory. The initial, more subtle changes that precede more severe losses in cognitive abilities have not been well characterized. Here, we established a model detecting initial subtle cognitive changes by comparing the performance of moderately aged Oncins France Strain A Sprague Dawley rats with young rats in the Morris water maze (MWM) and the Open Field (OF) test. Both age groups improved their performance during the training period at a similar rate; however, the older rats performed worse in several parameters measured in the MWM. Our results suggest that already at the age of 18-20 months rats show changes in their approach to solve the spatial memory task while their ability to learn is not yet diminished. The disparate spatial information processing of the moderately aged rats provides a novel animal model for early age-related cognitive alterations that could be useful to test the effect of early intervention strategies. Moreover, our results suggest that the sensitivity of cognitive tests in the elderly could be substantially enhanced if they assess both the improvement after several trials, and the strategy used to solve a certain task.
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Affiliation(s)
- Linda Blümel
- Institute of Pharmacology and Toxicology, Department of Veterinary Medicine, Freie Universität Berlin, Germany.
| | - Jan Brosda
- Institute of Pharmacology and Toxicology, Department of Veterinary Medicine, Freie Universität Berlin, Germany.
| | - Bettina Bert
- Institute of Pharmacology and Toxicology, Department of Veterinary Medicine, Freie Universität Berlin, Germany.
| | - Melanie Hamann
- Institute of Pharmacology and Toxicology, Department of Veterinary Medicine, Freie Universität Berlin, Germany.
| | - Gunnar P H Dietz
- Department of Global Medical Affairs, Dr. Willmar Schwabe GmbH & Co. KG, Karlsruhe, Germany.
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4
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McQuail JA, Dunn AR, Stern Y, Barnes CA, Kempermann G, Rapp PR, Kaczorowski CC, Foster TC. Cognitive Reserve in Model Systems for Mechanistic Discovery: The Importance of Longitudinal Studies. Front Aging Neurosci 2021; 12:607685. [PMID: 33551788 PMCID: PMC7859530 DOI: 10.3389/fnagi.2020.607685] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Accepted: 12/30/2020] [Indexed: 12/14/2022] Open
Abstract
The goal of this review article is to provide a resource for longitudinal studies, using animal models, directed at understanding and modifying the relationship between cognition and brain structure and function throughout life. We propose that forthcoming longitudinal studies will build upon a wealth of knowledge gleaned from prior cross-sectional designs to identify early predictors of variability in cognitive function during aging, and characterize fundamental neurobiological mechanisms that underlie the vulnerability to, and the trajectory of, cognitive decline. Finally, we present examples of biological measures that may differentiate mechanisms of the cognitive reserve at the molecular, cellular, and network level.
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Affiliation(s)
- Joseph A McQuail
- Department of Pharmacology, Physiology and Neuroscience, University of South Carolina School of Medicine, Columbia, SC, United States
| | - Amy R Dunn
- The Jackson Laboratory, Bar Harbor, ME, United States
| | - Yaakov Stern
- Cognitive Neuroscience Division, Department of Neurology, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, United States
| | - Carol A Barnes
- Departments of Psychology and Neuroscience, University of Arizona, Tucson, AZ, United States.,Evelyn F. McKnight Brain Institute, University of Arizona, Tucson, AZ, United States
| | - Gerd Kempermann
- CRTD-Center for Regenerative Therapies Dresden, Technische Universität Dresden, Dresden, Germany.,German Center for Neurodegenerative Diseases (DZNE), Helmholtz Association of German Research Centers (HZ), Dresden, Germany
| | - Peter R Rapp
- Laboratory of Behavioral Neuroscience, Neurocognitive Aging Section, National Institute on Aging, Baltimore, MD, United States
| | | | - Thomas C Foster
- Department of Neuroscience, McKnight Brain Institute, University of Florida, Gainesville, FL, United States.,Genetics and Genomics Program, University of Florida, Gainesville, FL, United States
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Li JY, Kuo TBJ, Hung CT, Yang CCH. Voluntary exercise enhances hippocampal theta rhythm and cognition in the rat. Behav Brain Res 2020; 399:112916. [PMID: 32949643 DOI: 10.1016/j.bbr.2020.112916] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 09/08/2020] [Accepted: 09/10/2020] [Indexed: 12/14/2022]
Abstract
Regular exercise promotes learning and memory functions. Theta activity is known to relate to various cognitive functions. An increase in theta power may be related to higher cognitive functioning and learning functions. However, evidence is lacking to directly confirm that exercise training can increase the theta activity and promote various cognitive functions simultaneously. We hypothesize that long-term voluntary exercise increases the activity of hippocampal theta rhythm and enhances memory behavior. We used the voluntary wheel running model and a training period of 8 weeks. We started the training when the rats were 12 weeks old. Before and after intervention, we performed a 24 -h electrophysiological recording and 8-arm radial maze test to analyze the hippocampal theta rhythm in awake stage, and spatial memory functions. We discovered that middle to high range frequency (6.5-12 Hz) of theta power was increased after exercise intervention. In addition, the working memory error of 8-arm radial maze test in the exercise group decreased significantly after the 8 weeks of treatment, and these reductions were negatively correlated with hippocampal theta activity. Our results demonstrate that 8-weeks voluntary exercise increases both hippocampal theta amplitude and spatial memory in the rats.
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Affiliation(s)
- Jia-Yi Li
- Department of Health and Leisure Management, Yuanpei University of Medical Technology, Hsinchu, Taiwan; Sleep Research Center, National Yang-Ming University, Taipei, Taiwan
| | - Terry B J Kuo
- Sleep Research Center, National Yang-Ming University, Taipei, Taiwan; Institute of Brain Science, National Yang-Ming University, Taipei, Taiwan; Brain Research Center, National Yang-Ming University, Taipei, Taiwan; Department of Education and Research, Taipei City Hospital, Taipei, Taiwan
| | - Chang-Tsen Hung
- Department of Health and Leisure Management, Yuanpei University of Medical Technology, Hsinchu, Taiwan
| | - Cheryl C H Yang
- Sleep Research Center, National Yang-Ming University, Taipei, Taiwan; Institute of Brain Science, National Yang-Ming University, Taipei, Taiwan; Brain Research Center, National Yang-Ming University, Taipei, Taiwan; Department of Education and Research, Taipei City Hospital, Taipei, Taiwan.
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Aging Alters Olfactory Bulb Network Oscillations and Connectivity: Relevance for Aging-Related Neurodegeneration Studies. Neural Plast 2020; 2020:1703969. [PMID: 32774353 PMCID: PMC7396091 DOI: 10.1155/2020/1703969] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Revised: 01/27/2020] [Accepted: 02/12/2020] [Indexed: 11/18/2022] Open
Abstract
The aging process eventually cause a breakdown in critical synaptic plasticity and connectivity leading to deficits in memory function. The olfactory bulb (OB) and the hippocampus, both regions of the brain considered critical for the processing of odors and spatial memory, are commonly affected by aging. Using an aged wild-type C57B/6 mouse model, we sought to define the effects of aging on hippocampal plasticity and the integrity of cortical circuits. Specifically, we measured the long-term potentiation of high-frequency stimulation (HFS-LTP) at the Shaffer-Collateral CA1 pyramidal synapses. Next, local field potential (LFP) spectra, phase-amplitude theta-gamma coupling (PAC), and connectivity through coherence were assessed in the olfactory bulb, frontal and entorhinal cortices, CA1, and amygdala circuits. The OB of aged mice showed a significant increase in the number of histone H2AX-positive neurons, a marker of DNA damage. While the input-output relationship measure of basal synaptic activity was found not to differ between young and aged mice, a pronounced decline in the slope of field excitatory postsynaptic potential (fEPSP) and the population spike amplitude (PSA) were found in aged mice. Furthermore, aging was accompanied by deficits in gamma network oscillations, a shift to slow oscillations, reduced coherence and theta-gamma PAC in the OB circuit. Thus, while the basal synaptic activity was unaltered in older mice, impairment in hippocampal synaptic transmission was observed only in response to HFS. However, age-dependent alterations in neural network appeared spontaneously in the OB circuit, suggesting the neurophysiological basis of synaptic deficits underlying olfactory processing. Taken together, the results highlight the sensitivity and therefore potential use of LFP quantitative network oscillations and connectivity at the OB level as objective electrophysiological markers that will help reveal specific dysfunctional circuits in aging-related neurodegeneration studies.
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7
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Pu Y, Cornwell BR, Cheyne D, Johnson BW. Gender differences in navigation performance are associated with differential theta and high-gamma activities in the hippocampus and parahippocampus. Behav Brain Res 2020; 391:112664. [DOI: 10.1016/j.bbr.2020.112664] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 03/12/2020] [Accepted: 04/20/2020] [Indexed: 01/07/2023]
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8
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Ma Q, Geng Y, Wang HL, Han B, Wang YY, Li XL, Wang L, Wang MW. High Frequency Repetitive Transcranial Magnetic Stimulation Alleviates Cognitive Impairment and Modulates Hippocampal Synaptic Structural Plasticity in Aged Mice. Front Aging Neurosci 2019; 11:235. [PMID: 31619982 PMCID: PMC6759649 DOI: 10.3389/fnagi.2019.00235] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Accepted: 08/14/2019] [Indexed: 01/11/2023] Open
Abstract
Normal aging is accompanied by hippocampus-dependent cognitive impairment, which is a risk factor of Alzheimer’s disease. This study aims to investigate the effect of high frequency-repetitive transcranial magnetic stimulation (HF-rTMS) on hippocampus-dependent learning and memory in aged mice and explore its underlying mechanisms. Forty-five male Kunming mice (15 months old) were randomly divided into three groups: aged sham, 5 Hz rTMS, and 25 Hz rTMS. Two sessions of 5 Hz or 25 Hz rTMS comprising 1,000 pulses in 10 trains were delivered once a day for 14 consecutive days. The aged sham group was treated by the reverse side of the coil. In the adult sham group, 15 male Kunming mice (3 months old) were treated the same way as the aged sham group. A Morris water maze (MWM) was conducted following the stimulation, and synaptic ultrastructure was observed through a transmission electron microscope. HF-rTMS improved spatial learning and memory impairment in the aged mice, and 5 Hz was more significant than 25 Hz. Synaptic plasticity-associated gene profiles were modified by HF-rTMS, especially neurotrophin signaling pathways and cyclic adenosine monophosphate response element binding protein (CREB) cofactors. Compared to the aged sham group, synaptic plasticity-associated proteins, i.e., synaptophysin (SYN) and postsynaptic density (PSD)-95 were increased; brain-derived neurotrophic factor (BDNF) and phosphorylated CREB (pCREB) significantly increased after the 5 Hz HF-rTMS treatment. Collectively, our results suggest that HF-rTMS ameliorated cognitive deficits in naturally aged mice. The 5 Hz rTMS treatment significantly enhanced synaptic structural plasticity and activated the BDNF/CREB pathway in the hippocampus.
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Affiliation(s)
- Qinying Ma
- Department of Neurology, the First Hospital of Hebei Medical University, Shijiazhuang, China.,Brain Aging and Cognitive Neuroscience Key Laboratory of Hebei, Shijiazhuang, China
| | - Yuan Geng
- Department of Neurology, the First Hospital of Hebei Medical University, Shijiazhuang, China.,Brain Aging and Cognitive Neuroscience Key Laboratory of Hebei, Shijiazhuang, China
| | - Hua-Long Wang
- Department of Neurology, the First Hospital of Hebei Medical University, Shijiazhuang, China.,Brain Aging and Cognitive Neuroscience Key Laboratory of Hebei, Shijiazhuang, China
| | - Bing Han
- Department of Neurology, the First Hospital of Hebei Medical University, Shijiazhuang, China.,Brain Aging and Cognitive Neuroscience Key Laboratory of Hebei, Shijiazhuang, China
| | - Yan-Yong Wang
- Department of Neurology, the First Hospital of Hebei Medical University, Shijiazhuang, China.,Brain Aging and Cognitive Neuroscience Key Laboratory of Hebei, Shijiazhuang, China
| | - Xiao-Li Li
- Department of Neurology, the First Hospital of Shijiazhuang, Shijiazhuang, China
| | - Lin Wang
- Emergency Department, CNPC Central Hospital, Langfang, China
| | - Ming-Wei Wang
- Department of Neurology, the First Hospital of Hebei Medical University, Shijiazhuang, China.,Brain Aging and Cognitive Neuroscience Key Laboratory of Hebei, Shijiazhuang, China
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López-Vázquez MÁ, Gama-García CE, Estrada-Reyes Y, Gaytán-Tocavén L, Alfaro JMC, Olvera-Cortés ME. Neonatal Monosodium Glutamate Administration Disrupts Place Learning and Alters Hippocampal-Prefrontal Learning-Related Theta Activity in the Adult Rat. Neuroscience 2019; 414:228-244. [PMID: 31299349 DOI: 10.1016/j.neuroscience.2019.07.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Revised: 06/23/2019] [Accepted: 07/01/2019] [Indexed: 01/30/2023]
Abstract
Neonatal treatment with monosodium glutamate causes profound deficits in place learning and memory in adult rats evaluated in the Morris maze. Theta activity has been related to hippocampal learning, and increased high-frequency theta activity occurs through efficient place learning training in the Morris maze. We wondered whether the place learning deficits observed in adult rats that had been neonatally treated with monosodium glutamate (MSG), were related to altered theta patterns in the hippocampus and prelimbic cortex, which were recorded during place learning training in the Morris maze. The MSG-treated group had a profound deficit in place learning ability, with a marginal reduction in escape latencies during the final days of training. Learning-related changes were observed in the relative power distribution in control and MSG-treated groups in the hippocampal EEG, but not in the prelimbic cortex. Increased prefrontal and reduced hippocampal absolute power that appeared principally during the final days of training, and reduced coherence between regions throughout the training (4-12 Hz), were observed in the MSG-treated rats, thereby suggesting a misfunction of the circuits rather than a hyperexcitable general state. In conclusion, neonatal administration of MSG, which caused a profound deficit in place learning at the adult age, also altered the theta pattern both in the hippocampus and prelimbic cortex.
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Affiliation(s)
- Miguel Ángel López-Vázquez
- Laboratorio de Neuroplasticidad de los Procesos Cognitivos, División de Neurociencias, Centro de Investigación Biomédica de Michoacán, Instituto Mexicano del Seguro Social, Camino de la Arboleda 300, Ex-Hacienda de San José de la Huerta, C.P., 58341, Morelia, Michoacán, México.
| | - Carla Estefanía Gama-García
- Laboratorio de Neurofisiología Experimental, División de Neurociencias, Centro de Investigación Biomédica de Michoacán, Instituto Mexicano del Seguro Social, Camino de la Arboleda 300, Ex-Hacienda de San José de la Huerta, C.P., 58341, Morelia, Michoacán, México
| | - Yoana Estrada-Reyes
- Laboratorio de Neuroplasticidad de los Procesos Cognitivos, División de Neurociencias, Centro de Investigación Biomédica de Michoacán, Instituto Mexicano del Seguro Social, Camino de la Arboleda 300, Ex-Hacienda de San José de la Huerta, C.P., 58341, Morelia, Michoacán, México
| | - Lorena Gaytán-Tocavén
- Laboratorio de Neurofisiología Experimental, División de Neurociencias, Centro de Investigación Biomédica de Michoacán, Instituto Mexicano del Seguro Social, Camino de la Arboleda 300, Ex-Hacienda de San José de la Huerta, C.P., 58341, Morelia, Michoacán, México
| | - José Miguel Cervantes Alfaro
- Laboratorio de Neurociencias, Departamento de Postgrado, Facultad de Medicina "Dr. Ignacio Chávez", Universidad Michoacana de San Nicolás de Hidalgo, Rafael Carrillo esq. Salvador González Herrejón S/N. C.P., 58000, Colonia Centro, Morelia, Michoacán, México
| | - María Esther Olvera-Cortés
- Laboratorio de Neurofisiología Experimental, División de Neurociencias, Centro de Investigación Biomédica de Michoacán, Instituto Mexicano del Seguro Social, Camino de la Arboleda 300, Ex-Hacienda de San José de la Huerta, C.P., 58341, Morelia, Michoacán, México
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10
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Pu Y, Cheyne DO, Cornwell BR, Johnson BW. Non-invasive Investigation of Human Hippocampal Rhythms Using Magnetoencephalography: A Review. Front Neurosci 2018; 12:273. [PMID: 29755314 PMCID: PMC5932174 DOI: 10.3389/fnins.2018.00273] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Accepted: 04/09/2018] [Indexed: 02/06/2023] Open
Abstract
Hippocampal rhythms are believed to support crucial cognitive processes including memory, navigation, and language. Due to the location of the hippocampus deep in the brain, studying hippocampal rhythms using non-invasive magnetoencephalography (MEG) recordings has generally been assumed to be methodologically challenging. However, with the advent of whole-head MEG systems in the 1990s and development of advanced source localization techniques, simulation and empirical studies have provided evidence that human hippocampal signals can be sensed by MEG and reliably reconstructed by source localization algorithms. This paper systematically reviews simulation studies and empirical evidence of the current capacities and limitations of MEG “deep source imaging” of the human hippocampus. Overall, these studies confirm that MEG provides a unique avenue to investigate human hippocampal rhythms in cognition, and can bridge the gap between animal studies and human hippocampal research, as well as elucidate the functional role and the behavioral correlates of human hippocampal oscillations.
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Affiliation(s)
- Yi Pu
- ARC Centre of Excellence in Cognition and its Disorders, Macquarie University, Sydney, NSW, Australia.,Department of Cognitive Science, Macquarie University, Sydney, NSW, Australia
| | - Douglas O Cheyne
- Program in Neurosciences and Mental Health, Hospital for Sick Children Research Institute, Toronto, ON, Canada.,Department of Medical Imaging, University of Toronto, Toronto, ON, Canada
| | - Brian R Cornwell
- Brain and Psychological Sciences Research Centre, Swinburne University of Technology, Melbourne, VIC, Australia
| | - Blake W Johnson
- ARC Centre of Excellence in Cognition and its Disorders, Macquarie University, Sydney, NSW, Australia.,Department of Cognitive Science, Macquarie University, Sydney, NSW, Australia
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11
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Gutiérrez-Guzmán BE, Hernández-Pérez JJ, Olvera-Cortés ME. Serotonergic modulation of septo-hippocampal and septo-mammillary theta activity during spatial learning, in the rat. Behav Brain Res 2017; 319:73-86. [DOI: 10.1016/j.bbr.2016.11.017] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Revised: 11/08/2016] [Accepted: 11/08/2016] [Indexed: 11/16/2022]
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12
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Pu Y, Cornwell BR, Cheyne D, Johnson BW. The functional role of human right hippocampal/parahippocampal theta rhythm in environmental encoding during virtual spatial navigation. Hum Brain Mapp 2016; 38:1347-1361. [PMID: 27813230 DOI: 10.1002/hbm.23458] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Revised: 08/28/2016] [Accepted: 10/25/2016] [Indexed: 12/19/2022] Open
Abstract
Low frequency theta band oscillations (4-8 Hz) are thought to provide a timing mechanism for hippocampal place cell firing and to mediate the formation of spatial memory. In rodents, hippocampal theta has been shown to play an important role in encoding a new environment during spatial navigation, but a similar functional role of hippocampal theta in humans has not been firmly established. To investigate this question, we recorded healthy participants' brain responses with a 160-channel whole-head MEG system as they performed two training sets of a virtual Morris water maze task. Environment layouts (except for platform locations) of the two sets were kept constant to measure theta activity during spatial learning in new and familiar environments. In line with previous findings, left hippocampal/parahippocampal theta showed more activation navigating to a hidden platform relative to random swimming. Consistent with our hypothesis, right hippocampal/parahippocampal theta was stronger during the first training set compared to the second one. Notably, theta in this region during the first training set correlated with spatial navigation performance across individuals in both training sets. These results strongly argue for the functional importance of right hippocampal theta in initial encoding of configural properties of an environment during spatial navigation. Our findings provide important evidence that right hippocampal/parahippocampal theta activity is associated with environmental encoding in the human brain. Hum Brain Mapp 38:1347-1361, 2017. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Yi Pu
- ARC Centre of Excellence in Cognition and its Disorders, Macquarie University, Sydney, New South Wales, Australia.,Department of Cognitive Science, Macquarie University, Sydney, New South Wales, Australia
| | - Brian R Cornwell
- Brain and Psychological Sciences Research Centre, Swinburne University of Technology, Melbourne, Victoria, Australia
| | - Douglas Cheyne
- Program in Neurosciences and Mental Health, Hospital for Sick Children Research Institute, Toronto, Ontario, Canada.,Institute of Medical Sciences and Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada.,Department of Medical Imaging, University of Toronto, Toronto, Ontario, Canada
| | - Blake W Johnson
- ARC Centre of Excellence in Cognition and its Disorders, Macquarie University, Sydney, New South Wales, Australia.,Department of Cognitive Science, Macquarie University, Sydney, New South Wales, Australia
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Li JY, Kuo TB, Yang CC. Aged rats show dominant modulation of lower frequency hippocampal theta rhythm during running. Exp Gerontol 2016; 83:63-70. [DOI: 10.1016/j.exger.2016.08.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Revised: 07/30/2016] [Accepted: 08/02/2016] [Indexed: 10/21/2022]
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Hernández-Pérez JJ, Gutiérrez-Guzmán BE, Olvera-Cortés ME. Hippocampal strata theta oscillations change their frequency and coupling during spatial learning. Neuroscience 2016; 337:224-241. [PMID: 27615031 DOI: 10.1016/j.neuroscience.2016.09.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Revised: 08/24/2016] [Accepted: 09/01/2016] [Indexed: 11/18/2022]
Abstract
The theta rhythm is necessary for hippocampal-dependent spatial learning. It has been proposed that each hippocampal stratum can generate a current theta dipole. Therefore, considering that each hippocampal circuit (CA1, CA3, and Dentate Gyrus (DG)) contributes differently to distinct aspects of a spatial memory, the theta oscillations on each stratum and their couplings may exhibit oscillatory dynamics associated with different stages of learning. To test this hypothesis, the theta oscillations from five hippocampal strata were recorded in the rat during different stages of learning in a Morris maze. The peak power, the relative power (RP) and the coherence between hippocampal strata were analyzed. The early acquisition stage of the Morris task was characterized by the predominance of slow frequency theta activity and high coupling between specific hippocampal strata at slow frequencies. However, on the last training day, the theta oscillations were faster in all hippocampal strata, with tighter coupling at fast frequencies between the CA3 pyramidal stratum and other strata. Our results suggest that modifications to the theta frequency and its coupling can be a means by which the hippocampus differentially operates during acquisition and retrieval states.
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Affiliation(s)
- J Jesús Hernández-Pérez
- Laboratorio de Neurofisiología Experimental, División de Neurociencias, Centro de Investigación Biomédica de Michoacán, Instituto Mexicano del Seguro Social, Morelia, Michoacán, Mexico; Instituto de Neurobiología, Universidad Nacional Autónoma de México, Juriquilla, Querétaro, Mexico.
| | - Blanca E Gutiérrez-Guzmán
- Laboratorio de Neurofisiología Experimental, División de Neurociencias, Centro de Investigación Biomédica de Michoacán, Instituto Mexicano del Seguro Social, Morelia, Michoacán, Mexico; Instituto de Neurobiología, Universidad Nacional Autónoma de México, Juriquilla, Querétaro, Mexico
| | - María E Olvera-Cortés
- Laboratorio de Neurofisiología Experimental, División de Neurociencias, Centro de Investigación Biomédica de Michoacán, Instituto Mexicano del Seguro Social, Morelia, Michoacán, Mexico
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López-Loeza E, Rangel-Argueta AR, López-Vázquez MÁ, Cervantes M, Olvera-Cortés ME. Differences in EEG power in young and mature healthy adults during an incidental/spatial learning task are related to age and execution efficiency. AGE (DORDRECHT, NETHERLANDS) 2016; 38:37. [PMID: 26961695 PMCID: PMC5005903 DOI: 10.1007/s11357-016-9896-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Accepted: 02/23/2016] [Indexed: 04/16/2023]
Abstract
The differential characteristics of absolute power in the EEG theta (4-8 Hz) and gamma (30-45 Hz) frequency bands have been analysed in young (18-25 years old, n = 14) and mature adults (45-65 years old, n = 12) during the incidental or intentional behavioural conditions of learning and recalling in a visuospatial task. A printed drawing of a maze including eight figures of common objects in specific placements, solved by connecting its entrance and exit points, allowed the subject's performance efficiency to be measured based on the number, position accuracy and/or identity of incidentally or intentionally learned and remembered objects. Meanwhile, EEG recordings from frontal, parietal and temporal derivations were obtained to determine the power values of the theta (4-8 Hz) and gamma (30-45 Hz) bands for each behavioural condition and derivation. Relative to the young adults, the mature adults generally showed lower absolute theta power values, mainly due to their low theta powers under the basal and incidental learning conditions, and higher absolute gamma power values in the frontal and temporal regions. Furthermore, higher theta band power in the frontal regions was related to higher performance efficiency in both incidental and intentional learning, regardless of the subjects' age. A significant negative correlation between the parameters of individual incidental or intentional learning performance and age was also found. Indeed, a differential accuracy of remembered information seems to be associated with age and incidental or intentional learning/memory testing conditions. These data support an increasing vulnerability of visuospatial learning abilities at mature ages and as ageing progresses.
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Affiliation(s)
- Elisa López-Loeza
- Laboratorio de Biofísica, Instituto de Física y Matemáticas, Universidad Michoacana de San Nicolás de Hidalgo, Edificio C3, Ciudad Universitaria, Francisco J. Múgica s/n, Col. Felicitas del Río, 58040, Morelia, Michoacán, México
| | - Ana Rosa Rangel-Argueta
- Laboratorio de Biofísica, Instituto de Física y Matemáticas, Universidad Michoacana de San Nicolás de Hidalgo, Edificio C3, Ciudad Universitaria, Francisco J. Múgica s/n, Col. Felicitas del Río, 58040, Morelia, Michoacán, México
| | - Miguel Ángel López-Vázquez
- Laboratorio de Biofísica, Instituto de Física y Matemáticas, Universidad Michoacana de San Nicolás de Hidalgo, Edificio C3, Ciudad Universitaria, Francisco J. Múgica s/n, Col. Felicitas del Río, 58040, Morelia, Michoacán, México
- Laboratorio de Neuroplasticidad de los procesos cognoscitivos, División de Neurociencias, Centro de Investigación Biomédica de Michoacán, Instituto Mexicano del Seguro Social, Camino de la Arboleda 300, Exhacienda de San José de la Huerta, 58341, Morelia, Michoacán, México
| | - Miguel Cervantes
- División de Estudios de Posgrado, Facultad de Ciencias Médicas y Biológicas "Dr. Ignacio Chávez", Universidad Michoacana de San Nicolás de Hidalgo, Rafael Carrillo esquina con Salvador González Herrejón s/n, Col. Centro, 58000, Morelia, Michoacán, México
| | - María Esther Olvera-Cortés
- Laboratorio de Neurofisiología Experimental, División de Neurociencias, Centro de Investigación Biomédica de Michoacán, Instituto Mexicano del Seguro Social, Camino de la Arboleda 300, Ex hacienda de San José de la Huerta, 58341, Morelia, Michoacán, México.
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Hernández-Pérez JJ, Gutiérrez-Guzmán BE, López-Vázquez MÁ, Olvera-Cortés ME. Supramammillary serotonin reduction alters place learning and concomitant hippocampal, septal, and supramammillar theta activity in a Morris water maze. Front Pharmacol 2015; 6:250. [PMID: 26578960 PMCID: PMC4625187 DOI: 10.3389/fphar.2015.00250] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Accepted: 10/14/2015] [Indexed: 11/29/2022] Open
Abstract
Hippocampal theta activity is related to spatial information processing, and high-frequency theta activity, in particular, has been linked to efficient spatial memory performance. Theta activity is regulated by the synchronizing ascending system (SAS), which includes mesencephalic and diencephalic relays. The supramamillary nucleus (SUMn) is located between the reticularis pontis oralis and the medial septum (MS), in close relation with the posterior hypothalamic nucleus (PHn), all of which are part of this ascending system. It has been proposed that the SUMn plays a role in the modulation of hippocampal theta-frequency; this could occur through direct connections between the SUMn and the hippocampus or through the influence of the SUMn on the MS. Serotonergic raphe neurons prominently innervate the hippocampus and several components of the SAS, including the SUMn. Serotonin desynchronizes hippocampal theta activity, and it has been proposed that serotonin may regulate learning through the modulation of hippocampal synchrony. In agreement with this hypothesis, serotonin depletion in the SUMn/PHn results in deficient spatial learning and alterations in CA1 theta activity-related learning in a Morris water maze. Because it has been reported that SUMn inactivation with lidocaine impairs the consolidation of reference memory, we asked whether changes in hippocampal theta activity related to learning would occur through serotonin depletion in the SUMn, together with deficiencies in memory. We infused 5,7-DHT bilaterally into the SUMn in rats and evaluated place learning in the standard Morris water maze task. Hippocampal (CA1 and dentate gyrus), septal and SUMn EEG were recorded during training of the test. The EEG power in each region and the coherence between the different regions were evaluated. Serotonin depletion in the SUMn induced deficient spatial learning and altered the expression of hippocampal high-frequency theta activity. These results provide evidence in support of a role for serotonin as a modulator of hippocampal learning, acting through changes in the synchronicity evoked in several relays of the SAS.
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Affiliation(s)
- J. Jesús Hernández-Pérez
- Laboratorio de Neurofisiología Experimental, División de Neurociencias, Centro de Investigación Biomédica de Michoacán, Instituto Mexicano del Seguro SocialMorelia, México
| | - Blanca E. Gutiérrez-Guzmán
- Laboratorio de Neurofisiología Experimental, División de Neurociencias, Centro de Investigación Biomédica de Michoacán, Instituto Mexicano del Seguro SocialMorelia, México
| | - Miguel Á. López-Vázquez
- Laboratorio de Neuroplasticidad de los Procesos Cognitivos, División de Neurociencias, Centro de Investigación Biomédica de Michoacán, Instituto Mexicano del Seguro SocialMorelia, México
- Instituto de Física y Matemáticas, Universidad Michoacana de San Nicolás de HidalgoMorelia, México
| | - María E. Olvera-Cortés
- Laboratorio de Neurofisiología Experimental, División de Neurociencias, Centro de Investigación Biomédica de Michoacán, Instituto Mexicano del Seguro SocialMorelia, México
- *Correspondence: María E. Olvera-Cortés
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Orzeł-Gryglewska J, Matulewicz P, Jurkowlaniec E. Theta activity in local field potential of the ventral tegmental area in sleeping and waking rats. Behav Brain Res 2014; 265:84-92. [DOI: 10.1016/j.bbr.2014.02.023] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2013] [Revised: 02/11/2014] [Accepted: 02/15/2014] [Indexed: 10/25/2022]
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González-Ramírez MM, Velázquez-Zamora DA, Olvera-Cortés ME, González-Burgos I. Changes in the plastic properties of hippocampal dendritic spines underlie the attenuation of place learning in healthy aged rats. Neurobiol Learn Mem 2014; 109:94-103. [DOI: 10.1016/j.nlm.2013.11.017] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2013] [Revised: 11/19/2013] [Accepted: 11/24/2013] [Indexed: 12/23/2022]
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The decline in rat hippocampal theta activity during response inhibition for the compound stimulus of negative patterning and simultaneous feature-negative tasks. Behav Brain Res 2013; 257:111-7. [PMID: 24045064 DOI: 10.1016/j.bbr.2013.09.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Revised: 09/03/2013] [Accepted: 09/07/2013] [Indexed: 11/24/2022]
Abstract
In experiment 1 of this study, we compared hippocampal theta activity between negative patterning and simple discrimination tasks. Our results demonstrated a transient decline in theta activity during response inhibition for a compound stimulus in the negative patterning task. In experiment 2 of this study, we compared hippocampal theta activity among simultaneous feature-negative, compound stimulus discrimination, and simple discrimination tasks in order to determine the cause of the decline in hippocampal theta activity during negative patterning tasks. Our results revealed that the decline in hippocampal theta activity occurred during the response inhibition for a compound stimulus in the simultaneous feature-negative task but not during the compound stimulus discrimination or simple discrimination tasks. Thus, we conclude that the transient decline in hippocampal theta activity is related to the inhibition in response to a compound stimulus that has an element that overlaps with a single stimulus.
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Olvera-Cortés ME, Gutiérrez-Guzmán BE, López-Loeza E, Hernández-Pérez JJ, López-Vázquez MÁ. Serotonergic modulation of hippocampal theta activity in relation to hippocampal information processing. Exp Brain Res 2013; 230:407-26. [DOI: 10.1007/s00221-013-3679-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2013] [Accepted: 08/07/2013] [Indexed: 10/26/2022]
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Transient decline in hippocampal theta activity during the acquisition process of the negative patterning task. PLoS One 2013; 8:e70756. [PMID: 23936249 PMCID: PMC3729686 DOI: 10.1371/journal.pone.0070756] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2013] [Accepted: 06/23/2013] [Indexed: 11/19/2022] Open
Abstract
Hippocampal function is important in the acquisition of negative patterning but not of simple discrimination. This study examined rat hippocampal theta activity during the acquisition stages (early, middle, and late) of the negative patterning task (A+, B+, AB-). The results showed that hippocampal theta activity began to decline transiently (for 500 ms after non-reinforced stimulus presentation) during the late stage of learning in the negative patterning task. In addition, this transient decline in hippocampal theta activity in the late stage was lower in the negative patterning task than in the simple discrimination task. This transient decline during the late stage of task acquisition may be related to a learning process distinctive of the negative patterning task but not the simple discrimination task. We propose that the transient decline of hippocampal theta activity reflects inhibitory learning and/or response inhibition after the presentation of a compound stimulus specific to the negative patterning task.
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22
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Lu CB, Li CZ, Li DL, Henderson Z. Nicotine induction of theta frequency oscillations in rodent medial septal diagonal band in vitro. Acta Pharmacol Sin 2013; 34:819-29. [PMID: 23524566 DOI: 10.1038/aps.2012.198] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
AIM This study aimed to examine the role of the nicotinic receptor (nAChR) in the generation of theta oscillations (4-12 Hz) in vitro. METHODS Electrophysiological studies were performed on medial septal diagonal band area (MSDB) slices to measure theta oscillation. Immunofluorescence and confocal microscopy studies were carried out to detect α4 nAChR and β2 nAChR subunits in perfused-fixed tissue from VGluT2-GFP and GAD67-GFP transgenic mice. RESULTS Application of nicotine to MSDB slices produced persistent theta oscillations in which area power increased in a dose-responsive manner. This activity was inhibited by GABAA receptor antagonists and partially by ionotropic glutamate receptor antagonists, indicating the involvement of local GABAergic and glutamatergic neurons in the production of the rhythmic activity. The nicotine-induced theta activity was also inhibited selectively by non-α7*nAChR antagonists, suggesting the presence of these receptor types on GABAergic and glutamatergic neuron populations in the MSDB. This was confirmed by immunofluorescence and confocal microscopy studies in transgenic mice in which the GABAergic and glutamatergic neurons express green fluorescent protein (GFP), showing localisation of β2 nAChR and α4 nAChR subunits, the most common constituents of non-α7*nAChRs, in both cell types in the MSDB. CONCLUSION Theta activity in the MSDB may be generated by tonic stimulation of non-α7*nAChRs.
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Orzeł-Gryglewska J, Kuśmierczak M, Matulewicz P, Jurkowlaniec E. Dopaminergic transmission in the midbrain ventral tegmental area in the induction of hippocampal theta rhythm. Brain Res 2013; 1510:63-77. [DOI: 10.1016/j.brainres.2013.03.021] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2012] [Revised: 03/04/2013] [Accepted: 03/19/2013] [Indexed: 12/11/2022]
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Gutiérrez-Guzmán BE, Hernández-Pérez JJ, López-Vázquez MÁ, Fregozo CS, Guevara MÁ, Olvera-Cortés ME. Serotonin depletion of supramammillary/posterior hypothalamus nuclei produces place learning deficiencies and alters the concomitant hippocampal theta activity in rats. Eur J Pharmacol 2012; 682:99-109. [PMID: 22387092 DOI: 10.1016/j.ejphar.2012.02.024] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2011] [Revised: 02/10/2012] [Accepted: 02/15/2012] [Indexed: 11/25/2022]
Abstract
Hippocampal theta activity is important for the acquisition of spatial information and is strongly influenced and regulated by extra-hippocampal inputs from the synchronising ascending system (SAS), which includes the supramammillary nucleus (SUMn) and the posterior hypothalamic nucleus (PHn). Together these nuclei play an important role in controlling the frequency encoding of theta activity and are innervated by serotonin synapses, which also regulate theta activity and learning abilities. The participation of the SUMn in place learning and modulation of hippocampal theta activity were recently shown; thus, we questioned whether serotonin acting on SUMn/PHn could modulate place learning ability and concurrent hippocampal theta activity. The serotonergic terminals of the SUMn/PHn in rats were lesioned through 5,7-dihydroxytryptamine (5,7-DHT) infusion, and hippocampal theta activity during the Morris water maze test was recorded. Rats in the vehicle group learned the task efficiently and showed learning-related theta changes in the CA1 and dentate gyrus regions throughout the training. The 5-HT-depleted rats were deficient in the Morris water maze task and showed theta activity in the CA1 and dentate gyrus that were unrelated to the processing of learning. We conclude that serotonin can regulate the hippocampal theta activity acting on the SUMn/PHn relay of the SAS and that the influence of 5-HT in these nuclei is required for the learning-related changes in hippocampal theta activity that underlie the successful resolution of the Morris water maze task.
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Affiliation(s)
- Blanca Erika Gutiérrez-Guzmán
- Laboratorio de Neurofisiología Experimental, Centro de Investigación Biomédica de Michoacán, Instituto Mexicano del Seguro Social, Camino de la Arboleda # 300, Ex-hacienda de San José de la Huerta, C.P. 58341, Morelia, Mich., México.
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