Special Issue "Neural Mechanisms of Learning and Memory"

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A special issue of Biology (ISSN 2079-7737).

Deadline for manuscript submissions: closed (31 August 2014)

Special Issue Editor

Guest Editor
Prof. Dr. Bertram Opitz (Website)

School of Psychology, University of Surrey, Guildford, Surrey, GU2 7XH, UK
Interests: neural basis of learning and memory; long term memory formation; second language acquisition; feedback based learning

Special Issue Information

Dear Colleagues,

Our brains hold a seemingly endless amount of information, from childhood memories to our home addresses. Not only neuroscience is already attempting to answer the question how are we able to learn, store, and recall all this information with such ease?

In a special issue of Biology we are going to rely on the huge range of concepts and techniques, from molecular events in the nervous system and human system neuroscientific approaches, to computational models aiming at a holistic picture of the neural mechanisms involved.

Advances in molecular biology and genetics are offering new clues about key molecules and proteins that influence memory. Research at the cellular level has shown that brain cells undergo chemical and structural changes during learning by changing the number or strength of connections between themselves. Recent animal studies suggest that manipulating these molecules could lead to new ways of modifying memories. Other studies on human participants have attempted to identify how different areas of the brain work together to enhance memory formation and storage.

For this special issue of Biology, we invite research articles from any field of neuroscience to help expand our understanding of the neural mechanisms of learning and memory.

Prof. Dr. Bertram Opitz
Guest Editor

Submission

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Biology is an international peer-reviewed Open Access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 600 CHF (Swiss Francs). English correction and/or formatting fees of 250 CHF (Swiss Francs) will be charged in certain cases for those articles accepted for publication that require extensive additional formatting and/or English corrections.

Published Papers (4 papers)

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Research

Open AccessArticle Environmental Enrichment Reverses Histone Methylation Changes in the Aged Hippocampus and Restores Age-Related Memory Deficits
Biology 2015, 4(2), 298-313; doi:10.3390/biology4020298
Received: 17 January 2015 / Revised: 10 March 2015 / Accepted: 19 March 2015 / Published: 1 April 2015
Cited by 2 | PDF Full-text (809 KB) | HTML Full-text | XML Full-text
Abstract
A decline in long-term memory (LTM) formation is a common feature of the normal aging process, which corresponds with abnormal expression of memory-related genes in the aged hippocampus. Epigenetic modulation of chromatin structure is required for proper transcriptional control of genes, such [...] Read more.
A decline in long-term memory (LTM) formation is a common feature of the normal aging process, which corresponds with abnormal expression of memory-related genes in the aged hippocampus. Epigenetic modulation of chromatin structure is required for proper transcriptional control of genes, such as the brain-derived neurotrophic factor (Bdnf) and Zif268 in the hippocampus during the consolidation of new memories. Recently, the view has emerged that aberrant transcriptional regulation of memory-related genes may be reflective of an altered epigenetic landscape within the aged hippocampus, resulting in memory deficits with aging. Here, we found that baseline resting levels for tri-methylation of histone H3 at lysine 4 (H3K4me3) and acetylation of histone H3 at lysine 9 and 14 (H3K9,K14ac) were altered in the aged hippocampus as compared to levels in the hippocampus of young adult rats. Interestingly, object learning failed to increase activity-dependent H3K4me3 and di-methylation of histone H3 at lysine 9 (H3K9me2) levels in the hippocampus of aged adults as compared to young adults. Treatment with the LSD-1 histone demethylase inhibitor, t-PCP, increased baseline resting H3K4me3 and H3K9,K14ac levels in the young adult hippocampus, while young adult rats exhibited similar memory deficits as observed in aged rats. After environmental enrichment (EE), we found that object learning induced increases in H3K4me3 levels around the Bdnf, but not the Zif268, gene region in the aged hippocampus and rescued memory deficits in aged adults. Collectively, these results suggest that histone lysine methylation levels are abnormally regulated in the aged hippocampus and identify histone lysine methylation as a transcriptional mechanism by which EE may serve to restore memory formation with aging. Full article
(This article belongs to the Special Issue Neural Mechanisms of Learning and Memory)
Open AccessArticle Effects of Anodal Transcranial Direct Current Stimulation on Visually Guided Learning of Grip Force Control
Biology 2015, 4(1), 173-186; doi:10.3390/biology4010173
Received: 3 November 2014 / Revised: 10 December 2014 / Accepted: 25 February 2015 / Published: 2 March 2015
Cited by 1 | PDF Full-text (634 KB) | HTML Full-text | XML Full-text
Abstract
Anodal transcranial Direct Current Stimulation (tDCS) has been shown to be an effective non-invasive brain stimulation method for improving cognitive and motor functioning in patients with neurological deficits. tDCS over motor cortex (M1), for instance, facilitates motor learning in stroke patients. However, [...] Read more.
Anodal transcranial Direct Current Stimulation (tDCS) has been shown to be an effective non-invasive brain stimulation method for improving cognitive and motor functioning in patients with neurological deficits. tDCS over motor cortex (M1), for instance, facilitates motor learning in stroke patients. However, the literature on anodal tDCS effects on motor learning in healthy participants is inconclusive, and the effects of tDCS on visuo-motor integration are not well understood. In the present study we examined whether tDCS over the contralateral motor cortex enhances learning of grip-force output in a visually guided feedback task in young and neurologically healthy volunteers. Twenty minutes of 1 mA anodal tDCS were applied over the primary motor cortex (M1) contralateral to the dominant (right) hand, during the first half of a 40 min power-grip task. This task required the control of a visual signal by modulating the strength of the power-grip for six seconds per trial. Each participant completed a two-session sham-controlled crossover protocol. The stimulation conditions were counterbalanced across participants and the sessions were one week apart. Performance measures comprised time-on-target and target-deviation, and were calculated for the periods of stimulation (or sham) and during the afterphase respectively. Statistical analyses revealed significant performance improvements over the stimulation and the afterphase, but this learning effect was not modulated by tDCS condition. This suggests that the form of visuomotor learning taking place in the present task was not sensitive to neurostimulation. These null effects, together with similar reports for other types of motor tasks, lead to the proposition that tDCS facilitation of motor learning might be restricted to cases or situations where the motor system is challenged, such as motor deficits, advanced age, or very high task demand. Full article
(This article belongs to the Special Issue Neural Mechanisms of Learning and Memory)
Open AccessArticle Interacting Memory Systems—Does EEG Alpha Activity Respond to Semantic Long-Term Memory Access in a Working Memory Task?
Biology 2015, 4(1), 1-16; doi:10.3390/biology4010001
Received: 18 August 2014 / Accepted: 15 December 2014 / Published: 24 December 2014
Cited by 3 | PDF Full-text (751 KB) | HTML Full-text | XML Full-text
Abstract
Memory consists of various individual processes which form a dynamic system co-ordinated by central (executive) functions. The episodic buffer as direct interface between episodic long-term memory (LTM) and working memory (WM) is fairly well studied but such direct interaction is less clear [...] Read more.
Memory consists of various individual processes which form a dynamic system co-ordinated by central (executive) functions. The episodic buffer as direct interface between episodic long-term memory (LTM) and working memory (WM) is fairly well studied but such direct interaction is less clear in semantic LTM. Here, we designed a verbal delayed-match-to-sample task specifically to differentiate between pure information maintenance and mental manipulation of memory traces with and without involvement of access to semantic LTM. Task-related amplitude differences of electroencephalographic (EEG) oscillatory brain activity showed a linear increase in frontal-midline theta and linear suppression of parietal beta amplitudes relative to memory operation complexity. Amplitude suppression at upper alpha frequency, which was previously found to indicate access to semantic LTM, was only sensitive to mental manipulation in general, irrespective of LTM involvement. This suggests that suppression of upper EEG alpha activity might rather reflect unspecific distributed cortical activation during complex mental processes than accessing semantic LTM. Full article
(This article belongs to the Special Issue Neural Mechanisms of Learning and Memory)
Open AccessArticle Pre- and Postsynaptic Role of Dopamine D2 Receptor DD2R in Drosophila Olfactory Associative Learning
Biology 2014, 3(4), 831-845; doi:10.3390/biology3040831
Received: 1 October 2014 / Revised: 29 October 2014 / Accepted: 12 November 2014 / Published: 21 November 2014
Cited by 1 | PDF Full-text (684 KB) | HTML Full-text | XML Full-text
Abstract
Dopaminergic neurons in Drosophila play critical roles in diverse brain functions such as motor control, arousal, learning, and memory. Using genetic and behavioral approaches, it has been firmly established that proper dopamine signaling is required for olfactory classical conditioning (e.g., aversive and [...] Read more.
Dopaminergic neurons in Drosophila play critical roles in diverse brain functions such as motor control, arousal, learning, and memory. Using genetic and behavioral approaches, it has been firmly established that proper dopamine signaling is required for olfactory classical conditioning (e.g., aversive and appetitive learning). Dopamine mediates its functions through interaction with its receptors. There are two different types of dopamine receptors in Drosophila: D1-like (dDA1, DAMB) and D2-like receptors (DD2R). Currently, no study has attempted to characterize the role of DD2R in Drosophila learning and memory. Using a DD2R-RNAi transgenic line, we have examined the role of DD2R, expressed in dopamine neurons (i.e., the presynaptic DD2R autoreceptor), in larval olfactory learning. The function of postsynaptic DD2R expressed in mushroom body (MB) was also studied as MB is the center for Drosophila learning, with a function analogous to that of the mammalian hippocampus. Our results showed that suppression of presynaptic DD2R autoreceptors impairs both appetitive and aversive learning. Similarly, postsynaptic DD2R in MB neurons appears to be involved in both appetitive and aversive learning. The data confirm, for the first time, that DD2R plays an important role in Drosophila olfactory learning. Full article
(This article belongs to the Special Issue Neural Mechanisms of Learning and Memory)

Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Type of Paper: Article
Title: Interacting memory systems - does EEG alpha activity respond to semantic long-term memory access in a working memory task?
Authors: Barbara Berger, Serif Omer, Annette Sterr and Paul Sauseng
Affiliation: School of Psychology, Faculty of Arts and Human Sciences, University of Surrey, Guildford GU2 7XH, UK; E-Mails: b.berger@surrey.ac.uk (B.B.); p.sauseng@surrey.ac.uk (P.S.)
Abstract: Memory consists of various individual processes which form a dynamic system co-ordinated by central (executive) functions. The episodic buffer as direct interface between episodic long-term memory (LTM) and working memory (WM) is fairly well studied but such direct interaction is less clear in semantic LTM. Here we designed a verbal late-match-to-sample task specifically to differentiate between pure information maintenance and mental manipulation of memory traces with and without involvement of access to semantic LTM. Task-related amplitude differences of electroencephalographic (EEG) oscillatory brain activity showed a linear increase in frontal-midline theta and linear suppression of parietal beta amplitudes relative to memory operation complexity. Amplitude suppression at fast alpha frequency, which was previously found to indicate access to semantic LTM, was only sensitive to mental manipulation in general, irrespective of LTM involvement.
This suggests that suppression of fast EEG alpha activity might rather reflect unspecific distributed cortical activation during complex mental processes than accessing semantic LTM.

Type of Paper: Article
Title: Effects of anodal transcranial Direct Current Stimulation on visuo-motor learning
Authors: Tamas Minarik, Paul Sauseng and Annette Sterr
Affiliation: Brain and Behaviour Research Group, School of Psychology, University of Surrey, UK; E-Mail: a.sterr@surrey.ac.uk
Abstract: Anodal transcranial Direct Current Stimulation (anodal-tDCS) has been shown to be an effective non-invasive brain stimulation method for improving cognitive and motor functioning in patients with neurological deficits. Anodal-tDCS over motor cortex, for instance, facilitates motor learning in stroke patients. However, findings on the effects of motor cortex anodal-tDCS on motor learning in healthy participants are inconclusive. Furthermore, its effect on visuo-motor integration is not well understood. In the present study we examined whether anodal-tDCS over the motor cortex enhances visuo-motor learning in a power-grip task in a healthy population. Participants completed a 2-session protocol with 40 minutes power-grip task in each session. This task required the control of a visual signal by modulating the strength of the power-grip for 6 seconds per trial and was carried out under anodal-tDCS and sham condition for each participant. The neurosimulation protocol comprised a standard montage with the active electrode over the contralateral motor cortex and 20 minutes of 1mA stimulation or sham stimulation (counterbalanced), with a week apart. Performance measures derived from time-on-target and target-deviation showed significant improvement over time for both stimulation conditions; during and after anodal-tDCS. Importantly, however, the results suggest that the applied neurostimulation did not influence visuo-motor learning. Specifically, anodal-tDCS had an impact neither within session nor between sessions (consolidation) on these performance measures. These findings in combination with previous studies indicate that anodal-tDCS improvements might be limited to cases where the motor system is challenged, i.e. patients with motor deficits or situations of very high task demand.

Type of Paper: Review
Title: Environmental enrichment reverses age-related changes in histone methylation levels in the hippocampus during memory consolidation
Authors: Sarah J. Morse, Robin L. Davis, Anderson A. Butler, Ian J. Soller, Jasmyne S. Thomas and Farah D. Lubin*
Affiliation: The Evelyn F. McKnight Brain Institute, Department of Neurobiology, University of Alabama at Birmingham, 1825 University Boulevard, Birmingham, AL 35294, USA; E-Mail: flubin@uab.edu
Abstract: Age-related memory decline is associated with gene expression changes in the hippocampus. Histone methylation-mediated gene transcription in the hippocampus is necessary for memory formation. Here we found that resting histone H3 lysine 4 trimethylation (H3K4me3) and H3 lysine 9 dimethylation (H3K9me2) levels increased in the aged hippocampus. We found that with increased H3K9me2, histone H3 lysines 9 and 14 acetylation was significantly decreased in the aged hippocampus. Inhibition of the histone demethylase LSD1 reproduced age-related changes in H3K4me3, but not H3K9me2, levels in area CA1 of young adults, which was associated with memory impairments. We found that environmental enrichment (EE) rescued deficits in brain derived neurotrophic factor (Bdnf) but not Zif268 gene expression in area CA1 of aged adults along with H3K9me2 levels at the Bdnf promoter. Together, these results suggest that histone methylation dysregulation in the hippocampus contributes to age-related memory decline and identify histone methylation as a transcriptional mechanism by which EE may serve to restore memory function with aging.

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