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Schmidig FJ, Ruch S, Henke K. Episodic long-term memory formation during slow-wave sleep. eLife 2024; 12:RP89601. [PMID: 38661727 PMCID: PMC11045222 DOI: 10.7554/elife.89601] [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] [Indexed: 04/26/2024] Open
Abstract
We are unresponsive during slow-wave sleep but continue monitoring external events for survival. Our brain wakens us when danger is imminent. If events are non-threatening, our brain might store them for later consideration to improve decision-making. To test this hypothesis, we examined whether novel vocabulary consisting of simultaneously played pseudowords and translation words are encoded/stored during sleep, and which neural-electrical events facilitate encoding/storage. An algorithm for brain-state-dependent stimulation selectively targeted word pairs to slow-wave peaks or troughs. Retrieval tests were given 12 and 36 hr later. These tests required decisions regarding the semantic category of previously sleep-played pseudowords. The sleep-played vocabulary influenced awake decision-making 36 hr later, if targeted to troughs. The words' linguistic processing raised neural complexity. The words' semantic-associative encoding was supported by increased theta power during the ensuing peak. Fast-spindle power ramped up during a second peak likely aiding consolidation. Hence, new vocabulary played during slow-wave sleep was stored and influenced decision-making days later.
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Affiliation(s)
| | - Simon Ruch
- Institute of Psychology, University of BernBernSwitzerland
- Faculty of Psychology, UniDistance SuisseBrigSwitzerland
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2
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Henke K, Ruch S. Unconscious processing effects manifest only if conscious processing is excluded. Cogn Neurosci 2024; 15:73-74. [PMID: 38666549 DOI: 10.1080/17588928.2024.2343658] [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: 04/02/2024] [Indexed: 05/31/2024]
Abstract
In their discussion paper Steinkrauss and Slotnick argue against a role for the hippocampus in unconscious memory formation and retrieval. Unfortunately, they omitted highly relevant evidence that supports a role for the hippocampus in unconscious memory. They criticize four articles, two from our laboratory, pointing out long-known confounds like residual consciousness. We uncover these reproaches as untrue allegations. In our own interest, we prevented conscious mnemonic processing because reliable unconscious memory effects manifest only if consciousness is completely excluded, and because we always knew that residual consciousness would be our Achilles heel for the proponents of the 'explicit memory dogma.'
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Affiliation(s)
- Katharina Henke
- Institute of Psychology, University of Bern, Bern, Switzerland
| | - Simon Ruch
- Faculty of Psychology, UniDistance Suisse, Brig, Switzerland
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3
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Thakral PP, Cutting ER, Lawless KE. The dead salmon strikes again: Reports of unconscious processing in the hippocampus may reflect Type-I error. Cogn Neurosci 2024; 15:79-82. [PMID: 38647209 DOI: 10.1080/17588928.2024.2343667] [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: 03/26/2024] [Indexed: 04/25/2024]
Abstract
Steinkrauss and Slotnick (2024) reviewed neuroimaging studies linking the hippocampus with implicit memory. They conclude that there is no convincing evidence that the hippocampus is associated with implicit memory because prior studies are confounded by explicit memory (among other factors). Here, we ask a different yet equally important question: do reports of unconscious hippocampal activity reflect a Type-I error (i.e. a false positive)? We find that 39% of studies linking the hippocampus with implicit memory (7 of 18) do not report correcting for multiple comparisons. These results indicate that many unconscious hippocampal effects may reflect a Type-I error.
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Affiliation(s)
- Preston P Thakral
- Department of Psychology and Neuroscience, Boston College, Chestnut Hill, MA, USA
- Department of Psychology, Smith College, Northampton, MA, USA
| | - Elizabeth R Cutting
- Department of Psychology and Neuroscience, Boston College, Chestnut Hill, MA, USA
| | - Kiera E Lawless
- Department of Psychology and Neuroscience, Boston College, Chestnut Hill, MA, USA
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4
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Züst MA. Dismissing the role of the hippocampus in implicit memory is special pleading. Cogn Neurosci 2024; 15:83-84. [PMID: 38647224 DOI: 10.1080/17588928.2024.2343663] [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: 03/07/2024] [Indexed: 04/25/2024]
Abstract
Steinkrauss and Slotnick (this issue) argue against hippocampal involvement in implicit memory, bringing up some important considerations. Their critique, however, exhibits significant flaws. The argumentation is based on an ill-defined key concept of 'implicit memory,' and important theoretical context is missed. Potential confounds are brought to bear against a rather narrow selection of studies, often without explaining how exactly the studies are biased. Refining the conceptual scope, including a broader range of literature, and arguing more inclusively would provide more nuanced insights into the hippocampus's role in implicit memory.
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Affiliation(s)
- Marc Alain Züst
- University Hospital of Old Age Psychiatry and Psychotherapy, University of Bern, Bern, Switzerland
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5
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Hannula DE, Minor GN, Slabbekoorn D. Conscious awareness and memory systems in the brain. WILEY INTERDISCIPLINARY REVIEWS. COGNITIVE SCIENCE 2023; 14:e1648. [PMID: 37012615 DOI: 10.1002/wcs.1648] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Revised: 01/06/2023] [Accepted: 03/05/2023] [Indexed: 04/05/2023]
Abstract
The term "memory" typically refers to conscious retrieval of events and experiences from our past, but experience can also change our behaviour without corresponding awareness of the learning process or the associated outcome. Based primarily on early neuropsychological work, theoretical perspectives have distinguished between conscious memory, said to depend critically on structures in the medial temporal lobe (MTL), and a collection of performance-based memories that do not. The most influential of these memory systems perspectives, the declarative memory theory, continues to be a mainstay of scientific work today despite mounting evidence suggesting that contributions of MTL structures go beyond the kinds or types of memory that can be explicitly reported. Consistent with these reports, more recent perspectives have focused increasingly on the processing operations supported by particular brain regions and the qualities or characteristics of resulting representations whether memory is expressed with or without awareness. These alternatives to the standard model generally converge on two key points. First, the hippocampus is critical for relational memory binding and representation even without awareness and, second, there may be little difference between some types of priming and explicit, familiarity-based recognition. Here, we examine the evolution of memory systems perspectives and critically evaluate scientific evidence that has challenged the status quo. Along the way, we highlight some of the challenges that researchers encounter in the context of this work, which can be contentious, and describe innovative methods that have been used to examine unconscious memory in the lab. This article is categorized under: Psychology > Memory Psychology > Theory and Methods Philosophy > Consciousness.
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6
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Zher-Wen, Yu R. Unconscious integration: Current evidence for integrative processing under subliminal conditions. Br J Psychol 2023; 114:430-456. [PMID: 36689339 DOI: 10.1111/bjop.12631] [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: 10/20/2022] [Accepted: 01/05/2023] [Indexed: 01/24/2023]
Abstract
Integrative processing is traditionally believed to be dependent on consciousness. While earlier studies within the last decade reported many types of integration under subliminal conditions (i.e. without perceptual awareness), these findings are widely challenged recently. This review evaluates the current evidence for 10 types of subliminal integration that are widely studied: arithmetic processing, object-context integration, multi-word processing, same-different processing, multisensory integration and 5 different types of associative learning. Potential methodological issues concerning awareness measures are also taken into account. It is concluded that while there is currently no reliable evidence for subliminal integration, this does not necessarily refute 'unconscious' integration defined through non-subliminal (e.g. implicit) approaches.
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Affiliation(s)
- Zher-Wen
- Department of Management, Hong Kong Baptist University, Hong Kong, China.,Department of Psychology, National University of Singapore, Singapore City, Singapore
| | - Rongjun Yu
- Department of Management, Hong Kong Baptist University, Hong Kong, China
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7
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Pang DKF, Elntib S. Further evidence and theoretical framework for a subliminal sensory buffer store (SSBS). Conscious Cogn 2023; 107:103452. [PMID: 36508898 DOI: 10.1016/j.concog.2022.103452] [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: 06/09/2022] [Revised: 11/28/2022] [Accepted: 11/28/2022] [Indexed: 12/14/2022]
Abstract
We recently provided evidence that strongly masked stimuli are not erased or overwritten but are briefly stored in a subliminal sensory buffer store (SSBS), where information can accumulate through repetition and become consciously accessible. SSBS supports a direct prediction made by the global workspace theory of consciousness (GWT) and has implications on discussions about conscious overflow and the problem of the criterion. Here we show that the presentation sequence and the time from the target presentation to evaluation does not significantly impact perception. We suggest that selected information from this subliminal sensory buffer store is transferred into a type of supraliminal short-term memory that keeps stable representations for longer durations with full conscious access. We argue that the level of conscious access of memory storage has a greater impact on subsequent reportability than initial phenomenology and needs to be included more prominently in discussions on perception and consciousness.
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Affiliation(s)
- Damian K F Pang
- School of Arts and Sciences, University of Pennsylvania, Philadelphia, PA 19104, USA; Department of Psychological Sciences, Institute of Psychology, Health and Society, University of Liverpool, Liverpool L69 3BX, the United Kingdom of Great Britain and Northern Ireland.
| | - Stamatis Elntib
- Department of Psychological Sciences, Institute of Psychology, Health and Society, University of Liverpool, Liverpool L69 3BX, the United Kingdom of Great Britain and Northern Ireland; School of Psychology and Counselling, Faculty of Arts and Social Sciences, The Open University, the United Kingdom of Great Britain and Northern Ireland
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8
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Pacozzi L, Knüsel L, Ruch S, Henke K. Inverse forgetting in unconscious episodic memory. Sci Rep 2022; 12:20595. [PMID: 36446829 PMCID: PMC9709067 DOI: 10.1038/s41598-022-25100-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Accepted: 11/24/2022] [Indexed: 12/03/2022] Open
Abstract
Forming memories of experienced episodes calls upon the episodic memory system. Episodic encoding may proceed with and without awareness of episodes. While up to 60% of consciously encoded episodes are forgotten after 10 h, the fate of unconsciously encoded episodes is unknown. Here we track over 10 h, which are filled with sleep or daytime activities, the retention of unconsciously and consciously experienced episodes. The episodes were displayed in cartoon clips that were presented weakly and strongly masked for conscious and unconscious encoding, respectively. Clip retention was tested for distinct clips directly after encoding, 3 min and 10 h after encoding using a forced-choice test that demands deliberate responses in both consciousness conditions. When encoding was conscious, retrieval accuracy decreased by 25% from 3 min to 10 h, irrespective of sleep or wakefulness. When encoding was unconscious, retrieval accuracy increased from 3 min to 10 h and depended on sleep. Hence, opposite to the classic forgetting curve, unconsciously acquired episodic memories strengthen over time and hinge on sleep on the day of learning to gain influence over human behavior.
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Affiliation(s)
- Luca Pacozzi
- Institute of Psychology, University of Bern, 3012, Bern, Switzerland.
| | - Leona Knüsel
- Institute of Psychology, University of Bern, 3012, Bern, Switzerland
| | - Simon Ruch
- Institute for Neuromodulation and Neurotechnology, Department of Neurosurgery and Neurotechnology, University Hospital and University of Tuebingen, 72076, Tübingen, Germany
| | - Katharina Henke
- Institute of Psychology, University of Bern, 3012, Bern, Switzerland
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9
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Schneider E, Züst MA, Wuethrich S, Schmidig F, Klöppel S, Wiest R, Ruch S, Henke K. Larger capacity for unconscious versus conscious episodic memory. Curr Biol 2021; 31:3551-3563.e9. [PMID: 34256016 DOI: 10.1016/j.cub.2021.06.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 01/29/2021] [Accepted: 06/03/2021] [Indexed: 11/28/2022]
Abstract
Episodic memory is the memory for experienced events. A peak competence of episodic memory is the mental combination of events to infer commonalities. Inferring commonalities may proceed with and without consciousness of events. Yet what distinguishes conscious from unconscious inference? This question inspired nine experiments that featured strongly and weakly masked cartoon clips presented for unconscious and conscious inference. Each clip featured a scene with a visually impenetrable hiding place. Five animals crossed the scene one-by-one consecutively. One animal trajectory represented one event. The animals moved through the hiding place, where they might linger or not. The participants' task was to observe the animals' entrances and exits to maintain a mental record of which animals hid simultaneously. We manipulated information load to explore capacity limits. Memory of inferences was tested immediately, 3.5 or 6 min following encoding. The participants retrieved inferences well when encoding was conscious. When encoding was unconscious, the participants needed to respond intuitively. Only habitually intuitive decision makers exhibited a significant delayed retrieval of inferences drawn unconsciously. Their unconscious retrieval performance did not drop significantly with increasing information load, while conscious retrieval performance dropped significantly. A working memory network, including hippocampus, was activated during both conscious and unconscious inference and correlated with retrieval success. An episodic retrieval network, including hippocampus, was activated during both conscious and unconscious retrieval of inferences and correlated with retrieval success. Only conscious encoding/retrieval recruited additional brain regions outside these networks. Hence, levels of consciousness influenced the memories' behavioral impact, memory capacity, and the neural representational code.
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Affiliation(s)
- Else Schneider
- Institute of Psychology, University of Bern, Fabrikstrasse 8, 3012 Bern, Switzerland
| | - Marc Alain Züst
- Institute of Psychology, University of Bern, Fabrikstrasse 8, 3012 Bern, Switzerland; University Hospital of Old Age Psychiatry and Psychotherapy, University of Bern, Bolligenstraße 111, 3000 Bern, Switzerland
| | - Sergej Wuethrich
- Institute of Psychology, University of Bern, Fabrikstrasse 8, 3012 Bern, Switzerland
| | - Flavio Schmidig
- Institute of Psychology, University of Bern, Fabrikstrasse 8, 3012 Bern, Switzerland
| | - Stefan Klöppel
- University Hospital of Old Age Psychiatry and Psychotherapy, University of Bern, Bolligenstraße 111, 3000 Bern, Switzerland
| | - Roland Wiest
- Institute of Diagnostic and Interventional Neuroradiology, University Hospital Bern, Freiburgstrasse 18, 3010 Bern, Switzerland
| | - Simon Ruch
- Institute of Psychology, University of Bern, Fabrikstrasse 8, 3012 Bern, Switzerland
| | - Katharina Henke
- Institute of Psychology, University of Bern, Fabrikstrasse 8, 3012 Bern, Switzerland.
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10
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Pang DKF, Elntib S. Strongly masked content retained in memory made accessible through repetition. Sci Rep 2021; 11:10284. [PMID: 33986370 PMCID: PMC8119432 DOI: 10.1038/s41598-021-89512-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Accepted: 04/21/2021] [Indexed: 02/03/2023] Open
Abstract
A growing body of evidence indicates that information can be stored even in the absence of conscious awareness. Despite these findings, unconscious memory is still poorly understood with limited evidence for unconscious iconic memory storage. Here we show that strongly masked visual data can be stored and accumulate to elicit clear perception. We used a repetition method across a wide range of conditions (Experiment 1) and a more focused follow-up experiment with enhanced masking conditions (Experiment 2). Information was stored despite being masked, demonstrating that masking did not erase or overwrite memory traces but limited perception. We examined the temporal properties and found that stored information followed a gradual but rapid decay. Extraction of meaningful information was severely impaired after 300 ms, and most data was lost after 700 ms. Our findings are congruent with theories of consciousness that are based on an integration of subliminal information and support theoretical predictions based on the global workspace theory of consciousness, especially the existence of an implicit iconic memory buffer store.
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Affiliation(s)
- Damian K. F. Pang
- grid.10025.360000 0004 1936 8470Department of Psychological Sciences, Institute of Psychology, Health and Society, University of Liverpool, Liverpool, L69 3BX UK ,grid.25879.310000 0004 1936 8972School of Arts and Sciences, University of Pennsylvania, Philadelphia, PA 19104 USA
| | - Stamatis Elntib
- grid.10025.360000 0004 1936 8470Department of Psychological Sciences, Institute of Psychology, Health and Society, University of Liverpool, Liverpool, L69 3BX UK
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11
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Drews HJ. Connecting sleep, the neurocognitive memory system, and Bourdieu's habitus concept: Is sleep a generative force of the habitus? JOURNAL FOR THE THEORY OF SOCIAL BEHAVIOUR 2021. [DOI: 10.1111/jtsb.12268] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- Henning Johannes Drews
- Department of Mental Health Norwegian University of Science and Technology Trondheim Norway
- Department of Sociology Christian‐Albrechts‐University Kiel Germany
- Department of Psychiatry and Psychotherapy Christian‐Albrechts‐University Kiel Germany
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12
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The superior longitudinal fasciculus and its functional triple-network mechanisms in brooding. NEUROIMAGE-CLINICAL 2019; 24:101935. [PMID: 31352219 PMCID: PMC6664225 DOI: 10.1016/j.nicl.2019.101935] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/02/2019] [Revised: 07/10/2019] [Accepted: 07/13/2019] [Indexed: 12/16/2022]
Abstract
Brooding, which refers to a repetitive focus on one's distress, is associated with functional connectivity within Default-Mode, Salience, and Executive-Control networks (DMN; SN; ECN), comprising the so-called "triple-network" of attention. Individual differences in brain structure that might perseverate dysfunctional connectivity of brain networks associated with brooding are less clear, however. Using diffusion and functional Magnetic Resonance Imaging, we explored multimodal relationships between brooding severity, white-matter microstructure, and resting-state functional connectivity in depressed adults (N = 32-44), and then examined whether findings directly replicated in a demographically-similar, independent sample (N = 36-45). Among the fully-replicated results, three core findings emerged. First, brooding severity is associated with functional integration and segregation of the triple-network, particularly with a Precuneal subnetwork of the DMN. Second, microstructural asymmetry of the Superior Longitudinal Fasciculus (SLF) provides a robust structural connectivity basis for brooding and may account for over 20% of its severity (Discovery: adj. R2 = 0.18; Replication: adj. R2 = 0.22; MSE = 0.06, Predictive R2 = 0.22). Finally, microstructure of the right SLF and auxiliary white-matter is associated with the functional connectivity correlates of brooding, both within and between components of the triple-network (Discovery: adj. R2 = 0.21; Replication: adj. R2 = 0.18; MSE = 0.03, Predictive R2 = 0.21-0.22). By cross-validating multimodal discovery with replication, the present findings help to reproducibly unify disparate perspectives of brooding etiology. Based on that synthesis, our study reformulates brooding as a microstructural-functional connectivity neurophenotype.
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13
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Züst MA, Ruch S, Wiest R, Henke K. Implicit Vocabulary Learning during Sleep Is Bound to Slow-Wave Peaks. Curr Biol 2019; 29:541-553.e7. [DOI: 10.1016/j.cub.2018.12.038] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Revised: 09/25/2018] [Accepted: 12/20/2018] [Indexed: 01/13/2023]
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14
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Otsuka K, Cornelissen G, Kubo Y, Shibata K, Hayashi M, Mizuno K, Ohshima H, Furukawa S, Mukai C. Circadian challenge of astronauts' unconscious mind adapting to microgravity in space, estimated by heart rate variability. Sci Rep 2018; 8:10381. [PMID: 29991811 PMCID: PMC6039530 DOI: 10.1038/s41598-018-28740-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Accepted: 06/28/2018] [Indexed: 12/12/2022] Open
Abstract
It is critical that the regulatory system functions well in space's microgravity. However, the "intrinsic" cardiovascular regulatory system (β), estimated by the fractal scaling of heart rate variability (HRV) (0.0001-0.01 Hz), does not adapt to the space environment during long-duration (6-month) space flights. Neuroimaging studies suggest that the default mode network (DMN) serves a broad adaptive purpose, its topology changing over time in association with different brain states of adaptive behavior. Hypothesizing that HRV varies in concert with changes in brain's functional connectivity, we analyzed 24-hour HRV records from 8 healthy astronauts (51.8 ± 3.7 years; 6 men) on long (174.5 ± 13.8 days) space missions, obtained before launch, after about 21 (ISS01), 73 (ISS02), and 156 (ISS03) days in space, and after return to Earth. Spectral power in 8 frequency regions reflecting activity in different brain regions was computed by maximal entropy. Improved β (p < 0.05) found in 4 astronauts with a positive activation in the "HRV slow-frequency oscillation" (0.10-0.20 Hz) occurred even in the absence of consciousness. The adaptive response was stronger in the evening and early sleep compared to morning (p = 0.039). Brain functional networks, the DMN in particular, can help adapt to microgravity in space with help from the circadian clock.
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Affiliation(s)
- Kuniaki Otsuka
- Executive Medical Center, Totsuka Royal Clinic, Tokyo Women's Medical University, Tokyo, Japan.
- Halberg Chronobiology Center, University of Minnesota, Minneapolis, Minnesota, USA.
| | - Germaine Cornelissen
- Halberg Chronobiology Center, University of Minnesota, Minneapolis, Minnesota, USA
| | - Yutaka Kubo
- Department of Medicine, Tokyo Women's Medical University, Medical Center East, Tokyo, Japan
| | - Koichi Shibata
- Department of Medicine, Tokyo Women's Medical University, Medical Center East, Tokyo, Japan
| | - Mitsutoshi Hayashi
- Department of Medicine, Tokyo Women's Medical University, Medical Center East, Tokyo, Japan
| | - Koh Mizuno
- Faculty of Education, Tohoku Fukushi University, Miyagi, Japan
- Space Biomedical Research Group, Japan Aerospace Exploration Agency, Tokyo, Japan
| | - Hiroshi Ohshima
- Space Biomedical Research Group, Japan Aerospace Exploration Agency, Tokyo, Japan
| | - Satoshi Furukawa
- Space Biomedical Research Group, Japan Aerospace Exploration Agency, Tokyo, Japan
| | - Chiaki Mukai
- Space Biomedical Research Group, Japan Aerospace Exploration Agency, Tokyo, Japan
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15
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Borsook D, Youssef AM, Barakat N, Sieberg CB, Elman I. Subliminal (latent) processing of pain and its evolution to conscious awareness. Neurosci Biobehav Rev 2018; 88:1-15. [PMID: 29476771 DOI: 10.1016/j.neubiorev.2018.02.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 02/07/2018] [Accepted: 02/19/2018] [Indexed: 12/18/2022]
Abstract
By unconscious or covert processing of pain we refer to nascent interactions that affect the eventual deliverance of pain awareness. Thus, internal processes (viz., repeated nociceptive events, inflammatory kindling, reorganization of brain networks, genetic) or external processes (viz., environment, socioeconomic levels, modulation of epigenetic status) contribute to enhancing or inhibiting the presentation of pain awareness. Here we put forward the notion that for many patients, ongoing sub-conscious changes in brain function are significant players in the eventual manifestation of chronic pain. In this review, we provide clinical examples of nascent or what we term pre-pain processes and the neurobiological mechanisms of how these changes may contribute to pain, but also potential opportunities to define the process for early therapeutic interventions.
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Affiliation(s)
- David Borsook
- Center for Pain and the Brain, 9 Hope Avenue, Mailbox 26, Waltham, MA, 06524-9936, United States.
| | - Andrew M Youssef
- Center for Pain and the Brain, 9 Hope Avenue, Mailbox 26, Waltham, MA, 06524-9936, United States
| | - Nadia Barakat
- Center for Pain and the Brain, 9 Hope Avenue, Mailbox 26, Waltham, MA, 06524-9936, United States
| | - Christine B Sieberg
- Center for Pain and the Brain, 9 Hope Avenue, Mailbox 26, Waltham, MA, 06524-9936, United States
| | - Igor Elman
- Dayton Veterans Affairs Medical Center 4100 West Third Street Dayton, OH, 45428, United States
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16
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Ruch S, Herbert E, Henke K. Subliminally and Supraliminally Acquired Long-Term Memories Jointly Bias Delayed Decisions. Front Psychol 2017; 8:1542. [PMID: 28955268 PMCID: PMC5600932 DOI: 10.3389/fpsyg.2017.01542] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2016] [Accepted: 08/24/2017] [Indexed: 11/13/2022] Open
Abstract
Common wisdom and scientific evidence suggest that good decisions require conscious deliberation. But growing evidence demonstrates that not only conscious but also unconscious thoughts influence decision-making. Here, we hypothesize that both consciously and unconsciously acquired memories guide decisions. Our experiment measured the influence of subliminally and supraliminally presented information on delayed (30-40 min) decision-making. Participants were presented with subliminal pairs of faces and written occupations for unconscious encoding. Following a delay of 20 min, participants consciously (re-)encoded the same faces now presented supraliminally along with either the same written occupations, occupations congruous to the subliminally presented occupations (same wage-category), or incongruous occupations (opposite wage-category). To measure decision-making, participants viewed the same faces again (with occupations absent) and decided on the putative income of each person: low, low-average, high-average, or high. Participants were encouraged to decide spontaneously and intuitively. Hence, the decision task was an implicit or indirect test of relational memory. If conscious thought alone guided decisions (= H0), supraliminal information should determine decision outcomes independently of the encoded subliminal information. This was, however, not the case. Instead, both unconsciously and consciously encoded memories influenced decisions: identical unconscious and conscious memories exerted the strongest bias on income decisions, while both incongruous and congruous (i.e., non-identical) subliminally and supraliminally formed memories canceled each other out leaving no bias on decisions. Importantly, the increased decision bias following the formation of identical unconscious and conscious memories and the reduced decision bias following to the formation of non-identical memories were determined relative to a control condition, where conscious memory formation alone could influence decisions. In view of the much weaker representational strength of subliminally vs. supraliminally formed memories, their long-lasting impact on decision-making is noteworthy.
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Affiliation(s)
- Simon Ruch
- Department of Psychology, University of BernBern, Switzerland.,Center for Cognition, Learning and Memory, University of BernBern, Switzerland
| | - Elizabeth Herbert
- School of Physiology, Pharmacology and Neuroscience, University of BristolBristol, United Kingdom
| | - Katharina Henke
- Department of Psychology, University of BernBern, Switzerland.,Center for Cognition, Learning and Memory, University of BernBern, Switzerland
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17
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Ruch S, Züst MA, Henke K. Subliminal messages exert long-term effects on decision-making. Neurosci Conscious 2016; 2016:niw013. [PMID: 30386634 PMCID: PMC6204644 DOI: 10.1093/nc/niw013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Revised: 07/01/2016] [Accepted: 07/22/2016] [Indexed: 01/02/2023] Open
Abstract
Subliminal manipulation is often considered harmless because its effects typically decay within a second. So far, subliminal long-term effects on behavior were only observed in studies which repeatedly presented highly familiar information such as single words. These studies suggest that subliminal messages are only slowly stored and might not be stored at all if they provide novel, unfamiliar information. We speculated that subliminal messages might affect delayed decision-making especially if messages contain several pieces of novel information that must be relationally bound in long-term memory. Relational binding engages the hippocampal memory system, which can rapidly encode and durably store novel relations. Here, we hypothesized that subliminally presented stimulus pairs would be relationally processed influencing the direction of delayed conscious decisions. In experiment 1, subliminal face–occupation pairs affected conscious decisions about the income of these individuals almost half an hour later. In experiment 2, subliminal presentation of vocabulary of a foreign language enabled participants to later decide whether these foreign words are presented with correct or incorrect translations. Subliminal influence did not significantly decay if probed after 25 versus 15 min. This is unprecedented evidence of the longevity and impact of subliminal messages on conscious, rational decision-making.
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Affiliation(s)
- Simon Ruch
- Department of Psychology, University of Bern, Switzerland and Center for Cognition, Learning and Memory, University of Bern, Switzerland
| | - Marc Alain Züst
- Department of Psychology, University of Bern, Switzerland and Center for Cognition, Learning and Memory, University of Bern, Switzerland
| | - Katharina Henke
- Department of Psychology, University of Bern, Switzerland and Center for Cognition, Learning and Memory, University of Bern, Switzerland
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Sand A, Nilsson ME. Subliminal or not? Comparing null-hypothesis and Bayesian methods for testing subliminal priming. Conscious Cogn 2016; 44:29-40. [PMID: 27351780 DOI: 10.1016/j.concog.2016.06.012] [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: 11/17/2015] [Revised: 04/27/2016] [Accepted: 06/17/2016] [Indexed: 10/21/2022]
Abstract
A difficulty for reports of subliminal priming is demonstrating that participants who actually perceived the prime are not driving the priming effects. There are two conventional methods for testing this. One is to test whether a direct measure of stimulus perception is not significantly above chance on a group level. The other is to use regression to test if an indirect measure of stimulus processing is significantly above zero when the direct measure is at chance. Here we simulated samples in which we assumed that only participants who perceived the primes were primed by it. Conventional analyses applied to these samples had a very large error rate of falsely supporting subliminal priming. Calculating a Bayes factor for the samples very seldom falsely supported subliminal priming. We conclude that conventional tests are not reliable diagnostics of subliminal priming. Instead, we recommend that experimenters calculate a Bayes factor when investigating subliminal priming.
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Affiliation(s)
- Anders Sand
- Gösta Ekmans Laboratory, Department of Psychology, Stockholm University, SE-106 91 Stockholm, Sweden.
| | - Mats E Nilsson
- Gösta Ekmans Laboratory, Department of Psychology, Stockholm University, SE-106 91 Stockholm, Sweden
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