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Pribadi AK, Chalasani SH. Fear conditioning in invertebrates. Front Behav Neurosci 2022; 16:1008818. [PMID: 36439964 PMCID: PMC9686301 DOI: 10.3389/fnbeh.2022.1008818] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Accepted: 10/19/2022] [Indexed: 09/30/2023] Open
Abstract
Learning to identify and predict threats is a basic skill that allows animals to avoid harm. Studies in invertebrates like Aplysia californica, Drosophila melanogaster, and Caenorhabditis elegans have revealed that the basic mechanisms of learning and memory are conserved. We will summarize these studies and highlight the common pathways and mechanisms in invertebrate fear-associated behavioral changes. Fear conditioning studies utilizing electric shock in Aplysia and Drosophila have demonstrated that serotonin or dopamine are typically involved in relaying aversive stimuli, leading to changes in intracellular calcium levels and increased presynaptic neurotransmitter release and short-term changes in behavior. Long-term changes in behavior typically require multiple, spaced trials, and involve changes in gene expression. C. elegans studies have demonstrated these basic aversive learning principles as well; however, fear conditioning has yet to be explicitly demonstrated in this model due to stimulus choice. Because predator-prey relationships can be used to study learned fear in a naturalistic context, this review also summarizes what is known about predator-induced behaviors in these three organisms, and their potential applications for future investigations into fear conditioning.
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Affiliation(s)
- Amy K. Pribadi
- Biological Sciences Graduate Program, University of California, San Diego, La Jolla, San Diego, CA, United States
- Molecular Neurobiology Laboratory, The Salk Institute for Biological Studies, La Jolla, CA, United States
| | - Sreekanth H. Chalasani
- Biological Sciences Graduate Program, University of California, San Diego, La Jolla, San Diego, CA, United States
- Molecular Neurobiology Laboratory, The Salk Institute for Biological Studies, La Jolla, CA, United States
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Jaap C, Maack MC, Taesler P, Steinicke F, Rose M. Enriched environments enhance the development of explicit memory in an incidental learning task. Sci Rep 2022; 12:18717. [PMID: 36333393 PMCID: PMC9636381 DOI: 10.1038/s41598-022-23226-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2022] [Accepted: 10/27/2022] [Indexed: 11/06/2022] Open
Abstract
Learning, rendered in an implicit (unconscious) or explicit (conscious) way, is a crucial part of our daily life. Different factors, like attention or motivation, influence the transformation from implicit to explicit memory. Via virtual reality a lively and engaging surrounding can be created, whereby motivational processes are assumed to be a vital part of the transition from implicit to explicit memory. In the present study, we tested the impact of an enriched virtual reality compared to two conventional, non-enriched 2D-computer-screen based tasks on implicit to explicit memory transformation, using an audio-visual sequential association task. We hypothesized, that the immersive nature of the VR surrounding enhances the transfer from implicit to explicit memory. Notably, the overall amount of learned sequence pairs were not significantly different between experimental groups, but the degree of awareness was affected by the different settings. However, we observed an increased level of explicitly remembered pairs within the VR group compared to two screen-based groups. This finding clearly demonstrates that a near-natural experimental setting affects the transformation process from implicit to explicit memory.
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Affiliation(s)
- Carina Jaap
- grid.13648.380000 0001 2180 3484NeuroImage Nord, Department for Systems Neuroscience, University Medical Center Hamburg Eppendorf, Martinistrasse 52, 20246 Hamburg, Germany
| | - Marike C. Maack
- grid.13648.380000 0001 2180 3484NeuroImage Nord, Department for Systems Neuroscience, University Medical Center Hamburg Eppendorf, Martinistrasse 52, 20246 Hamburg, Germany
| | - Philipp Taesler
- grid.13648.380000 0001 2180 3484NeuroImage Nord, Department for Systems Neuroscience, University Medical Center Hamburg Eppendorf, Martinistrasse 52, 20246 Hamburg, Germany
| | - Frank Steinicke
- grid.9026.d0000 0001 2287 2617Human-Computer Interaction, Department of Informatics, University of Hamburg, Vogt-Kölln-Str. 30, 22527 Hamburg, Germany
| | - Michael Rose
- grid.13648.380000 0001 2180 3484NeuroImage Nord, Department for Systems Neuroscience, University Medical Center Hamburg Eppendorf, Martinistrasse 52, 20246 Hamburg, Germany
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King EM, Edwards LL, Borich MR. Effects of short-term arm immobilization on motor skill acquisition. PLoS One 2022; 17:e0276060. [PMID: 36240219 PMCID: PMC9565666 DOI: 10.1371/journal.pone.0276060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Accepted: 09/28/2022] [Indexed: 01/17/2023] Open
Abstract
Learning to sequence movements is necessary for skillful interaction with the environment. Neuroplasticity, particularly long-term potentiation (LTP), within sensorimotor networks underlies the acquisition of motor skill. Short-term immobilization of the arm, even less than 12 hours, can reduce corticospinal excitability and increase the capacity for LTP-like plasticity within the contralateral primary motor cortex. However, it is still unclear whether short-term immobilization influences motor skill acquisition. The current study aimed to evaluate the effect of short-term arm immobilization on implicit, sequence-specific motor skill acquisition using a modified Serial Reaction Time Task (SRTT). Twenty young, neurotypical adults underwent a single SRTT training session after six hours of immobilization of the non-dominant arm or an equivalent period of no immobilization. Our results demonstrated that participants improved SRTT performance overall after training, but there was no evidence of an effect of immobilization prior to task training on performance improvement. Further, improvements on the SRTT were not sequence-specific. Taken together, motor skill acquisition for sequential, individuated finger movements improved following training but the effect of six hours of immobilization was difficult to discern.
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Affiliation(s)
- Erin M. King
- Neuroscience Graduate Program, Graduate Division of Biological and Biomedical Sciences, Emory University, Atlanta, GA, United States of America
- Division of Physical Therapy, Department of Rehabilitation Medicine, Emory University, Atlanta, GA, United States of America
| | - Lauren L. Edwards
- Division of Physical Therapy, Department of Rehabilitation Medicine, Emory University, Atlanta, GA, United States of America
| | - Michael R. Borich
- Division of Physical Therapy, Department of Rehabilitation Medicine, Emory University, Atlanta, GA, United States of America
- Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, United States of America
- * E-mail:
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Dopamine Enhances Item Novelty Detection via Hippocampal and Associative Recall via Left Lateral Prefrontal Cortex Mechanisms. J Neurosci 2019; 39:7920-7933. [PMID: 31405927 DOI: 10.1523/jneurosci.0495-19.2019] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Revised: 07/04/2019] [Accepted: 07/16/2019] [Indexed: 11/21/2022] Open
Abstract
The involvement of fronto-striatal circuits in item and associative memory retrieval as well as in the stabilization of memories by retrieval practice suggests that both retrieval and re-encoding of stored memories might rely on dopaminergic mechanisms in humans. We tested these hypotheses in a placebo-controlled pharmacological fMRI study using 2 mg of the D2 antagonist haloperidol administered acutely before a cued associative recall task of previously encoded picture-word pairs in 53 healthy humans of both sexes. The cued associative recall was moreover repeated 3 d later outside the scanner without pharmacological intervention. Dopaminergic modulation significantly improved associative recall performance and recognition accuracy of verbal items. Moreover, we observed a significant dopamine effect on re-encoding in terms of increased specificity of associative memories from the first to the second cued associative recall. Better association memory under haloperidol was linked with higher activity in the left lateral prefrontal cortex and right parietal cortex, suggesting that dopamine facilitates associative retrieval through increased recruitment of frontoparietal monitoring processes. In contrast, improved recognition of verbal items under haloperidol was reflected by enhanced novelty detection in the hippocampus and increased activity in saliency networks. Together, these results show distinct but concomitant positive effects of dopamine on associative recall and item recognition and suggest that the specificity of associative recall through re-encoding mechanisms is likewise augmented by dopamine.SIGNIFICANCE STATEMENT Although the neurotransmitter dopamine has been linked with learning and memory for a long time, dopaminergic effects on item recognition in humans were demonstrated only recently. The involvement of fronto-striatal monitoring processes in association retrieval suggests that associative memory might be particularly affected by dopamine. Moreover, fronto-striatal dopaminergic signals have been hypothesized to determine the updating and re-encoding of previously retrieved memories. We here demonstrate clear facilitative effects of dopamine on associative recall and item recognition mediated by prefrontal and hippocampal mechanisms respectively. Additionally, effects on re-encoding were reflected by increased specificity of associative memories. These results augment our understanding of dopaminergic processes in episodic memory retrieval and offer new perspectives on memory impairments in dopamine-related disorders and their treatment.
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Clos M, Bunzeck N, Sommer T. Dopamine is a double-edged sword: dopaminergic modulation enhances memory retrieval performance but impairs metacognition. Neuropsychopharmacology 2019; 44:555-563. [PMID: 30356095 PMCID: PMC6333779 DOI: 10.1038/s41386-018-0246-y] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Revised: 10/09/2018] [Accepted: 10/12/2018] [Indexed: 12/30/2022]
Abstract
While memory encoding and consolidation processes have been linked with dopaminergic signaling for a long time, the role of dopamine in episodic memory retrieval remained mostly unexplored. Based on previous observations of striatal activity during memory retrieval, we used pharmacological functional magnetic resonance imaging to investigate the effects of dopamine on retrieval performance and metacognitive memory confidence in healthy humans. Dopaminergic modulation by the D2 antagonist haloperidol administered acutely during the retrieval phase improved recognition accuracy of previously learned pictures significantly and was associated with increased activity in the substantia nigra/ventral tegmental area, locus coeruleus, hippocampus, and amygdala during retrieval. In contrast, confidence for new decisions was impaired by unsystematically increased activity of the striatum across confidence levels and restricted range of responsiveness in frontostriatal networks under haloperidol. These findings offer new insights into the mechanisms underlying memory retrieval and metacognition and provide a broader perspective on the presence of memory problems in dopamine-related diseases and the treatment of memory disorders.
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Affiliation(s)
- Mareike Clos
- Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
| | - Nico Bunzeck
- 0000 0001 2180 3484grid.13648.38Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Hamburg, Germany ,0000 0001 0057 2672grid.4562.5Institute of Psychology I, University of Lübeck, Lübeck, Germany
| | - Tobias Sommer
- 0000 0001 2180 3484grid.13648.38Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
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Cerreta AGB, Vickery TJ, Berryhill ME. Visual statistical learning deficits in memory-impaired individuals. Neurocase 2018; 24:259-265. [PMID: 30794056 DOI: 10.1080/13554794.2019.1579843] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Visual statistical learning (VSL) refers to the learning of environmental regularities. Classically considered an implicit process, one patient with isolated hippocampal damage is severely impaired at VSL tasks, suggesting involvement of explicit memory. Here, we asked whether memory impairment (MI) alone, absent of clear hippocampal pathology, predicted deficits across different VSL tasks. A classic VSL task revealed no learning in MI participants (Exp. 1), while imposing attentional demands (Exp. 2: flicker detection, Exp. 3: gender/location categorization) during familiarization revealed modest residual VSL. MI with nonspecific neural correlates predicted impaired VSL overall, but attentional processes may be harnessed for rehabilitation.
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Affiliation(s)
| | - Timothy J Vickery
- b Department of Psychological and Brain Sciences , University of Delaware , Newark , DE , USA
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