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Kim K, Nokia MS, Palva S. Distinct Hippocampal Oscillation Dynamics in Trace Eyeblink Conditioning Task for Retrieval and Consolidation of Associations. eNeuro 2024; 11:ENEURO.0030-23.2024. [PMID: 38627063 PMCID: PMC11046259 DOI: 10.1523/eneuro.0030-23.2024] [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: 01/24/2023] [Revised: 04/04/2024] [Accepted: 04/10/2024] [Indexed: 04/28/2024] Open
Abstract
Trace eyeblink conditioning (TEBC) has been widely used to study associative learning in both animals and humans. In this paradigm, conditioned responses (CRs) to conditioned stimuli (CS) serve as a measure for retrieving learned associations between the CS and the unconditioned stimuli (US) within a trial. Memory consolidation, that is, learning over time, can be quantified as an increase in the proportion of CRs across training sessions. However, how hippocampal oscillations differentiate between successful memory retrieval within a session and consolidation across TEBC training sessions remains unknown. To address this question, we recorded local field potentials (LFPs) from the rat dorsal hippocampus during TEBC and investigated hippocampal oscillation dynamics associated with these two functions. We show that transient broadband responses to the CS were correlated with memory consolidation, as indexed by an increase in CRs across TEBC sessions. In contrast, induced alpha (8-10 Hz) and beta (16-20 Hz) band responses were correlated with the successful retrieval of the CS-US association within a session, as indexed by the difference in trials with and without CR.
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Affiliation(s)
- Kayeon Kim
- Neuroscience Center, Helsinki Institute of Life Sciences, University of Helsinki, Helsinki FI-00014, Finland
- Department of Neuroscience, Faculty of Health and Medical Science, University of Copenhagen, Copenhagen N DK-2200, Denmark
| | - Miriam S Nokia
- Department of Psychology, University of Jyväskylä, Jyväskylä FI-40014, Finland
| | - Satu Palva
- Neuroscience Center, Helsinki Institute of Life Sciences, University of Helsinki, Helsinki FI-00014, Finland
- Centre for Cognitive Neuroscience, School of Psychology and Neuroscience, University of Glasgow, Glasgow G12 8QQ, Scotland
- Division of psychology, VISE, Faculty of Education and Psychology, University of Oulu, Oulu, Ostrobothnia FI-90014, Finland
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Nokia MS, Waselius T, Penttonen M. CA3-CA1 long-term potentiation occurs regardless of respiration and cardiac cycle phases in urethane-anesthetized rats. Hippocampus 2023; 33:1228-1232. [PMID: 37221699 DOI: 10.1002/hipo.23551] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 05/08/2023] [Accepted: 05/10/2023] [Indexed: 05/25/2023]
Abstract
Breathing and heartbeat synchronize to each other and to brain function and affect cognition in humans. However, it is not clear how cardiorespiratory rhythms modulate such basic processes as synaptic plasticity thought to underlie learning. Thus, we studied if respiration and cardiac cycle phases at burst stimulation onset affect hippocampal long-term potentiation (LTP) in the CA3-CA1 synapse in urethane-anesthetized adult male Sprague-Dawley rats. In a between-subjects design, we timed burst stimulation of the ventral hippocampal commissure (vHC) to systole or diastole either during expiration or inspiration and recorded responses throughout the hippocampus with a linear probe. As classical conditioning in humans seems to be most efficient at expiration-diastole, we also expected LTP to be most efficient if burst stimulation was targeted to expiration-diastole. However, LTP was induced equally in all four groups and respiration and cardiac cycle phase did not modulate CA1 responses to vHC stimulation overall. This could be perhaps because we bypassed all natural routes of external influences on the CA1 by directly stimulating the vHC. In the future, the effect of cardiorespiratory rhythms on synaptic plasticity could also be studied in awake state and in other parts of the hippocampal tri-synaptic loop.
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Affiliation(s)
- Miriam S Nokia
- Department of Psychology and Centre for Interdisciplinary Brain Research, University of Jyvaskyla, Jyväskylä, Finland
| | - Tomi Waselius
- Department of Psychology and Centre for Interdisciplinary Brain Research, University of Jyvaskyla, Jyväskylä, Finland
| | - Markku Penttonen
- Department of Psychology and Centre for Interdisciplinary Brain Research, University of Jyvaskyla, Jyväskylä, Finland
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Waselius T, Xu W, Sparre JI, Penttonen M, Nokia MS. -Cardiac cycle and respiration phase affect responses to the conditioned stimulus in young adults trained in trace eyeblink conditioning. J Neurophysiol 2022; 127:767-775. [PMID: 35138956 DOI: 10.1152/jn.00298.2021] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Rhythms of breathing and heartbeat are linked to each other as well as to rhythms of the brain. Our recent studies suggest that presenting the conditioned stimulus during expiration or during the diastolic phase of the cardiac cycle facilitates neural processing of that stimulus and improves learning an eyeblink classical conditioning task. To date, it has not been examined whether utilizing information from both respiration and cardiac cycle phases simultaneously allows even more efficient modulation of learning. Here we studied whether the timing of the conditioned stimulus to different cardiorespiratory rhythm phase combinations affects learning trace eyeblink conditioning in healthy young adults. The results were consistent with previous reports: Timing the conditioned stimulus to diastole during expiration was more beneficial for learning than timing it to systole during inspiration. Cardiac cycle phase seemed to explain most of this variation in learning at the behavioral level. Brain evoked potentials (N1) elicited by the conditioned stimulus and recorded using electroencephalogram were larger when the conditioned stimulus was presented to diastole during expiration than when it was presented to systole during inspiration. Breathing phase explained the variation in the N1 amplitude. To conclude, our findings suggest that non-invasive monitoring of bodily rhythms combined with closed-loop control of stimulation can be used to promote learning in humans. The next step will be to test if performance can also be improved in humans with compromised cognitive ability, such as in older people with memory impairments.
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Affiliation(s)
- Tomi Waselius
- Department of Psychology and Centre for Interdisciplinary Brain Research, University of Jyväskylä, Jyväskylä, Finland
| | - Weiyong Xu
- Department of Psychology and Centre for Interdisciplinary Brain Research, University of Jyväskylä, Jyväskylä, Finland
| | - Julia Isabella Sparre
- Department of Psychology and Centre for Interdisciplinary Brain Research, University of Jyväskylä, Jyväskylä, Finland
| | - Markku Penttonen
- Department of Psychology and Centre for Interdisciplinary Brain Research, University of Jyväskylä, Jyväskylä, Finland
| | - Miriam S Nokia
- Department of Psychology and Centre for Interdisciplinary Brain Research, University of Jyväskylä, Jyväskylä, Finland
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Bruegger D, Abegg M. Prediction of cortical theta oscillations in humans for phase-locked visual stimulation. J Neurosci Methods 2021; 361:109288. [PMID: 34274403 DOI: 10.1016/j.jneumeth.2021.109288] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Revised: 07/09/2021] [Accepted: 07/10/2021] [Indexed: 11/17/2022]
Abstract
BACKGROUND The timing of an event within an oscillatory phase is considered to be one of the key strategies used by the brain to code and process neural information. Whereas existing methods of studying this phenomenon are chiefly based on retrospective analysis of electroencephalography (EEG) data, we now present a method to study it prospectively. New method: We present a system that allows for the delivery of visual stimuli at a specific phase of the cortical theta oscillation by fitting a sine to raw surface EEG data to estimate and predict the phase. One noteworthy feature of the method is that it can minimize potentially confounding effects of previous trials by using only a short sequence of past data. RESULTS In a trial with 10 human participants we achieved a significant phase locking with an inter-trial phase coherence of 0.39. We demonstrated successful phase locking on synthetic signals with a signal-to-noise ratio of less than - 20 dB. Comparison with existing method(s): We compared the new method to an autoregressive method published in the literature and found the new method was superior in mean phase offset, circular standard deviation, and prediction latency. CONCLUSIONS By fitting sine waves to raw EEG traces, we locked visual stimuli to arbitrary phases within the theta oscillatory cycle of healthy humans.
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Affiliation(s)
- D Bruegger
- Department of Ophthalmology, Inselspital, Bern University Hospital, University of Bern, Switzerland; Graduate School for Cellular and Biomedical Sciences (GCB), University of Bern, Switzerland.
| | - M Abegg
- Department of Ophthalmology, Inselspital, Bern University Hospital, University of Bern, Switzerland.
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Nokia MS, Waselius T, Sahramäki J, Penttonen M. Most hippocampal CA1 pyramidal cells in rabbits increase firing during awake sharp-wave ripples and some do so in response to external stimulation and theta. J Neurophysiol 2020; 123:1671-1681. [PMID: 32208887 DOI: 10.1152/jn.00056.2020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Hippocampus forms neural representations of real-life events including multimodal information of spatial and temporal context. These representations, i.e., organized sequences of neuronal firing, are repeated during following rest and sleep, especially when so-called sharp-wave ripples (SPW-Rs) characterize hippocampal local field potentials. This SPW-R -related replay is thought to underlie memory consolidation. Here, we set out to explore how hippocampal CA1 pyramidal cells respond to the conditioned stimulus during trace eyeblink conditioning and how these responses manifest during SPW-Rs in awake adult female New Zealand White rabbits. Based on reports in rodents, we expected SPW-Rs to take place in bursts, possibly according to a slow endogenous rhythm. In awake rabbits, half of all SPW-Rs took place in bursts, but no endogenous slow rhythm appeared. Conditioning trials suppressed SPW-Rs while increasing theta for a period of several seconds. As expected based on previous findings, only a quarter of the putative CA1 pyramidal cells increased firing in response to the conditioned stimulus. Compared with other cells, rate-increasing cells were more active during spontaneous epochs of hippocampal theta while response profile during conditioning did not affect firing during SPW-Rs. Taken together, CA1 pyramidal cell firing during SPW-Rs is not limited to cells that fired during the preceding experience. Furthermore, the importance of possible reactivations taking place during theta epochs on memory consolidation warrants further investigation.NEW & NOTEWORTHY We studied hippocampal sharp-wave ripples and theta and CA1 pyramidal cell activity during trace eyeblink conditioning in rabbits. Conditioning trials suppressed ripples while increasing theta for a period of several seconds. A quarter of the cells increased firing in response to the conditioned stimulus and fired extensively during endogenous theta as well as ripples. The role of endogenous theta epochs in off-line memory consolidation should be studied further.
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Affiliation(s)
- Miriam S Nokia
- Department of Psychology, University of Jyväskylä, Jyväskylä, Finland
| | - Tomi Waselius
- Department of Psychology, University of Jyväskylä, Jyväskylä, Finland
| | - Joonas Sahramäki
- Department of Psychology, University of Jyväskylä, Jyväskylä, Finland
| | - Markku Penttonen
- Department of Psychology, University of Jyväskylä, Jyväskylä, Finland
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Suter EE, Weiss C, Disterhoft JF. Differential responsivity of neurons in perirhinal cortex, lateral entorhinal cortex, and dentate gyrus during time-bridging learning. Hippocampus 2019; 29:511-526. [PMID: 30311282 PMCID: PMC6615905 DOI: 10.1002/hipo.23041] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Revised: 08/29/2018] [Accepted: 09/24/2018] [Indexed: 12/30/2022]
Abstract
Many studies have focused on the function of hippocampal region CA1 as a critical site for associative memory, but much less is known about changes in the afferents to CA1. Here we report the activity of multiple single neurons from perirhinal and entorhinal cortex and from dentate gyrus during trace eyeblink conditioning as well as consolidated recall, and in pseudo-conditioned control rabbits. We also report an analysis of theta activity filtered from the local field potential (LFP). Our results show early associative changes in single-neuron firing rate as well as theta oscillations in lateral entorhinal cortex (EC) and dentate gyrus (DG), and increases in the number of responsive neurons in perirhinal cortex. In both EC and DG, a subset of neurons from conditioned animals exhibited an elevated baseline firing rate and large responses to the conditioned stimulus and trace period. A similar population of cells has been seen in DG and in medial, but not lateral, EC during spatial tasks, suggesting that lateral EC contains cells responsive to a temporal associative task. In contrast to recent studies in our laboratory that found significant CA1 contributions to long-term memory, the activity profiles of neurons within EC and DG were similar for conditioned and pseudoconditioned rabbits during post-consolidation sessions. Collectively these results demonstrate that individual subregions of medial temporal lobe differentially support new and remotely acquired memories. Neuron firing profiles were similar on training trials when conditioned responses were and were not exhibited, demonstrating that these temporal lobe regions represent the CS-US association and do not control the behavioral response. The analysis of theta activity revealed that theta power was modulated by the conditioning stimuli in both the conditioned and pseudoconditioned groups and that although both groups exhibited a resetting of phase to the corneal airpuff, only the conditioned group exhibited a resetting of phase to the whisker conditioned stimulus.
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Affiliation(s)
- Eugénie E Suter
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - Craig Weiss
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - John F Disterhoft
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
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Waselius T, Wikgren J, Halkola H, Penttonen M, Nokia MS. Learning by heart: cardiac cycle reveals an effective time window for learning. J Neurophysiol 2018; 120:830-838. [PMID: 29742028 DOI: 10.1152/jn.00128.2018] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cardiac cycle phase is known to modulate processing of simple sensory information. This effect of the heartbeat on brain function is likely exerted via baroreceptors, the neurons sensitive for changes in blood pressure. From baroreceptors, the signal is conveyed all the way to the forebrain and the medial prefrontal cortex. In the two experiments reported, we examined whether learning, as a more complex form of cognition, can be modulated by the cardiac cycle phase. Human participants ( experiment 1) and rabbits ( experiment 2) were trained in trace eyeblink conditioning while neural activity was recorded. The conditioned stimulus was presented contingently with either the systolic or diastolic phase of the cycle. The tone used as the conditioned stimulus evoked amplified responses in both humans (electroencephalogram from "vertex," Cz) and rabbits (hippocampal CA1 local field potential) when its onset was timed at systole. In humans, the cardiac cycle phase did not affect learning, but rabbits trained at diastole learned significantly better than those trained at a random phase of the cardiac cycle. In summary, our results suggest that neural processing of external stimuli and also learning can be affected by targeting stimuli on the basis of cardiac cycle phase. These findings might be useful in applications aimed at maximizing or minimizing the effects of external stimulation. NEW & NOTEWORTHY It has been shown that rapid changes in bodily states modulate neural processing of external stimulus in brain. In this study, we show that modulation of neural processing of external stimulus and learning about it depends on the phase of the cardiac cycle. This is a novel finding that can be applied to optimize associative learning.
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Affiliation(s)
- Tomi Waselius
- Department of Psychology, University of Jyväskylä , Jyväskylä , Finland
| | - Jan Wikgren
- Department of Psychology, University of Jyväskylä , Jyväskylä , Finland.,Centre for Interdisciplinary Brain Research, University of Jyväskylä , Jyväskylä , Finland
| | - Hanna Halkola
- Department of Psychology, University of Jyväskylä , Jyväskylä , Finland
| | - Markku Penttonen
- Department of Psychology, University of Jyväskylä , Jyväskylä , Finland
| | - Miriam S Nokia
- Department of Psychology, University of Jyväskylä , Jyväskylä , Finland
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Waselius T, Pöllänen E, Wikgren J, Penttonen M, Nokia MS. Hippocampal theta phase-contingent memory retrieval in delay and trace eyeblink conditioning. Behav Brain Res 2018; 337:264-270. [PMID: 28882692 DOI: 10.1016/j.bbr.2017.09.001] [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: 04/26/2017] [Revised: 08/25/2017] [Accepted: 09/01/2017] [Indexed: 10/18/2022]
Abstract
Hippocampal theta oscillations (3-12Hz) play a prominent role in learning. It has been suggested that encoding and retrieval of memories are supported by different phases of the theta cycle. Our previous study on trace eyeblink conditioning in rabbits suggests that the timing of the conditioned stimulus (CS) in relation to theta phase affects encoding but not retrieval of the memory trace. Here, we directly tested the effects of hippocampal theta phase on memory retrieval in two experiments conducted on adult female New Zealand White rabbits. In Experiment 1, animals were trained in trace eyeblink conditioning followed by extinction, and memory retrieval was tested by presenting the CS at troughs and peaks of the theta cycle during different stages of learning. In Experiment 2, animals were trained in delay conditioning either contingent on a high level of theta or at a random neural state. Conditioning was then followed by extinction conducted either at a random state, contingent on theta trough or contingent on theta peak. Our current results indicate that the phase of theta at CS onset has no effect on the performance of the behavioral learned response at any stage of classical eyeblink conditioning or extinction. In addition, theta-contingent trial presentation does not improve learning during delay eyeblink conditioning. The results are consistent with our earlier findings and suggest that the theta phase alone is not sufficient to affect learning at the behavioral level. It seems that the retrieval of recently acquired memories and consequently performing a learned response is moderated by neural mechanisms other than hippocampal theta.
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Affiliation(s)
- Tomi Waselius
- Department of Psychology, P.O. Box 35, 40014, University of Jyvaskyla, Finland; Centre for Interdisciplinary Brain Research, University of Jyvaskyla, Finland.
| | - Eveliina Pöllänen
- Department of Psychology, P.O. Box 35, 40014, University of Jyvaskyla, Finland
| | - Jan Wikgren
- Department of Psychology, P.O. Box 35, 40014, University of Jyvaskyla, Finland; Centre for Interdisciplinary Brain Research, University of Jyvaskyla, Finland
| | - Markku Penttonen
- Department of Psychology, P.O. Box 35, 40014, University of Jyvaskyla, Finland
| | - Miriam S Nokia
- Department of Psychology, P.O. Box 35, 40014, University of Jyvaskyla, Finland
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Nokia MS, Gureviciene I, Waselius T, Tanila H, Penttonen M. Hippocampal electrical stimulation disrupts associative learning when targeted at dentate spikes. J Physiol 2017; 595:4961-4971. [PMID: 28426128 DOI: 10.1113/jp274023] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Accepted: 04/10/2017] [Indexed: 01/23/2023] Open
Abstract
KEY POINTS Dentate spikes are fast fluctuations of hilar local-field potentials that take place during rest and are thought to reflect input arriving from the entorhinal cortex to the hippocampus. During dentate spikes, neuronal firing in hippocampal input (dentate gyrus) and output (CA1/CA3) regions is uncoupled. To date, the behavioural significance of dentate spikes is unknown. Here, we provide evidence that disrupting the dentate spike-related uncoupling of the dentate gyrus and the CA1/CA3 subregions for 1 h after training retards associative learning. We suggest dentate spikes play a significant role in memory consolidation. ABSTRACT Hippocampal electrophysiological oscillations, namely theta and ripples, have been implicated in encoding and consolidation of new memories, respectively. According to existing literature, hippocampal dentate spikes are prominent, short-duration (<30 ms), large-amplitude (∼2-4 mV) fluctuations in hilar local-field potentials that take place during awake immobility and sleep. Interestingly, previous studies indicate that during dentate spikes dentate gyrus granule cells increase their firing while firing of CA1 pyramidal cells are suppressed, thus resulting in momentary uncoupling of the two hippocampal subregions. To date, the behavioural significance of dentate spikes is unknown. Here, to study the possible role of dentate spikes in learning, we trained adult male Sprague-Dawley rats in trace eyeblink classical conditioning. For 1 h immediately following each conditioning session, one group of animals received hippocampal stimulation via the ventral hippocampal commissure (vHC) contingent on dentate spikes to disrupt the uncoupling between the dentate gyrus and the CA1 subregions. A yoked control group was stimulated during immobility, irrespective of brain state, and another control group was not stimulated at all. As a result, learning was impaired only in the group where vHC stimulation was administered contingent on dentate spikes. Our results suggest dentate spikes and/or the associated uncoupling of the dentate gyrus and the CA1 play a significant role in memory consolidation. Dentate spikes could possibly reflect reactivation and refinement of a memory trace within the dentate gyrus triggered by input from the entorhinal cortex.
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Affiliation(s)
- Miriam S Nokia
- Department of Psychology, University of Jyväskylä, PO Box 35, FI-40014, Finland
| | - Irina Gureviciene
- Department of Psychology, University of Jyväskylä, PO Box 35, FI-40014, Finland.,University of Eastern Finland, A.I.Virtanen Institute for Molecular Sciences, PO Box 1627, FI-70211, Kuopio, Finland
| | - Tomi Waselius
- Department of Psychology, University of Jyväskylä, PO Box 35, FI-40014, Finland
| | - Heikki Tanila
- University of Eastern Finland, A.I.Virtanen Institute for Molecular Sciences, PO Box 1627, FI-70211, Kuopio, Finland
| | - Markku Penttonen
- Department of Psychology, University of Jyväskylä, PO Box 35, FI-40014, Finland
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Cicchese JJ, Berry SD. Hippocampal Non-Theta-Contingent Eyeblink Classical Conditioning: A Model System for Neurobiological Dysfunction. Front Psychiatry 2016; 7:1. [PMID: 26903886 PMCID: PMC4751249 DOI: 10.3389/fpsyt.2016.00001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Accepted: 01/01/2016] [Indexed: 11/30/2022] Open
Abstract
Typical information processing is thought to depend on the integrity of neurobiological oscillations that may underlie coordination and timing of cells and assemblies within and between structures. The 3-7 Hz bandwidth of hippocampal theta rhythm is associated with cognitive processes essential to learning and depends on the integrity of cholinergic, GABAergic, and glutamatergic forebrain systems. Since several significant psychiatric disorders appear to result from dysfunction of medial temporal lobe (MTL) neurochemical systems, preclinical studies on animal models may be an important step in defining and treating such syndromes. Many studies have shown that the amount of hippocampal theta in the rabbit strongly predicts the acquisition rate of classical eyeblink conditioning and that impairment of this system substantially slows the rate of learning and attainment of asymptotic performance. Our lab has developed a brain-computer interface that makes eyeblink training trials contingent upon the explicit presence or absence of hippocampal theta. The behavioral benefit of theta-contingent training has been demonstrated in both delay and trace forms of the paradigm with a two- to fourfold increase in learning speed over non-theta states. The non-theta behavioral impairment is accompanied by disruption of the amplitude and synchrony of hippocampal local field potentials, multiple-unit excitation, and single-unit response patterns dependent on theta state. Our findings indicate a significant electrophysiological and behavioral impact of the pretrial state of the hippocampus that suggests an important role for this MTL system in associative learning and a significant deleterious impact in the absence of theta. Here, we focus on the impairments in the non-theta state, integrate them into current models of psychiatric disorders, and suggest how improvement in our understanding of neurobiological oscillations is critical for theories and treatment of psychiatric pathology.
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Affiliation(s)
- Joseph J Cicchese
- Department of Psychology, Center for Neuroscience, Miami University , Oxford, OH , USA
| | - Stephen D Berry
- Department of Psychology, Center for Neuroscience, Miami University , Oxford, OH , USA
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