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Neural evidence for non-conscious working memory
Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Faculty of Psychology and Educational Sciences, University of Coimbra, Portugal.
Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI).
2018 (Engelska)Ingår i: Cerebral Cortex, ISSN 1047-3211, E-ISSN 1460-2199, Vol. 28, nr 9, s. 3217-3228Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Recent studies have found that non-consciously perceived information can be retained for several seconds, a feat that has been attributed to non-conscious working memory processes. However, these studies have mainly relied on subjective measures of visual experience, and the neural processes responsible for non-conscious short-term retention remains unclear. Here we used continuous flash suppression to render stimuli non-conscious in a delayed match-to-sample task together with fMRI to investigate the neural correlates of non-conscious short-term (5-15 s) retention. The participants' behavioral performance was at chance level when they reported no visual experience of the sample stimulus. Critically, multivariate pattern analyses of BOLD signal during the delay phase could classify presence versus absence of sample stimuli based on signal patterns in frontal cortex, and its spatial position based on signal patterns in occipital cortex. In addition, univariate analyses revealed increased BOLD signal change in prefrontal regions during memory recognition. Thus, our findings demonstrate short-term maintenance of information presented non-consciously, defined by chance performance behaviorally. This non-consciously retained information seems to rely on persistent neural activity in frontal and occipital cortex, and may engage further cognitive control processes during memory recognition.

Ort, förlag, år, upplaga, sidor
Oxford University Press, 2018. Vol. 28, nr 9, s. 3217-3228
Nyckelord [en]
consciousness, continuous flash suppression, fMRI, unconscious, subjective measure, working memory
Nationell ämneskategori
Neurovetenskaper Psykologi
Identifikatorer
URN: urn:nbn:se:umu:diva-124806DOI: 10.1093/cercor/bhx193ISI: 000443545600012PubMedID: 28981609OAI: oai:DiVA.org:umu-124806DiVA, id: diva2:955526
Forskningsfinansiär
VetenskapsrådetEU, FP7, Sjunde ramprogrammet, 604102
Anmärkning

Originally included in thesis in manuscript form with title "Neural evidence for non-conscious short-term memory".

Tillgänglig från: 2016-08-25 Skapad: 2016-08-25 Senast uppdaterad: 2018-10-25Bibliografiskt granskad
Ingår i avhandling
1. The neural substrates of non-conscious working memory
Öppna denna publikation i ny flik eller fönster >>The neural substrates of non-conscious working memory
2016 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Alternativ titel[sv]
Neurala substrat till icke-medvetet arbetsminne
Abstract [en]

Background: Despite our distinct impression to the contrary, we are only conscious of a fraction of all the neural activity underlying our thoughts and behavior. Most neural processes occur non-consciously, and in parallel with our conscious experience. However, it is still unclear what the limits of non-conscious processes are in terms of higher cognitive functions. Many recent studies have shown that increasingly more advanced functions can operate non-consciously, but non-conscious information is still thought to be fleeting and undetectable within 500 milliseconds. Here we used various techniques to render information non-conscious, together with functional magnetic resonance imaging (fMRI), to investigate if non-consciously presented information can be retained for several seconds, what the neural substrates of such retention are, and if it is consistent with working memory maintenance.

Results: In Study I we used an attentional blink paradigm to render stimuli (single letters) non-conscious, and a variable delay period (5 – 15 s) prior to memory test. It was found that non-conscious memory performance was above chance after all delay durations, and showed no signs of decline over time. Univariate fMRI analysis showed that the durable retention was associated with sustained BOLD signal change in the prefrontal cortex and cerebellum during the delay period. In Study II we used continuous flash suppression (CFS) to render stimuli (faces and tools) non-conscious, and a variable delay period (5 or 15 s) prior to memory test. The durable retention of up to 15 s was replicated, and it was found that stimuli identity and spatial position was retained until prospective use. In Study III we used CFS to render tools non-conscious, and a variable delay period (5 – 15 s) prior to memory test. It was found that memory performance was not better than chance. However, by using multi-voxel pattern analysis it was nonetheless possible to detect the presence vs. absence of non-conscious stimuli in the frontal cortex,and their spatial position (left vs. right) in the occipital cortex during the delay.

Conclusions: Overall these findings suggest that non-consciously presented information (identity and/or position) can be retained for several seconds,and is associated with BOLD signal in frontal and posterior regions. These findings are consistent with working memory maintenance of non-consciously presented information, and thereby constrain models of working memory and theories of consciousness.

Ort, förlag, år, upplaga, sidor
Umeå: Umeå University, 2016. s. 99
Serie
Umeå University medical dissertations, ISSN 0346-6612 ; 1835
Nyckelord
non-conscious, working memory, neural substrates, visual perception, consciousness, functional magnetic resonance imaging (fMRI)
Nationell ämneskategori
Neurovetenskaper Psykologi
Identifikatorer
urn:nbn:se:umu:diva-124808 (URN)978-91-7601-543-8 (ISBN)
Disputation
2016-09-16, Hörsal E, Humanisthuset, Umeå University, 901 87 Umeå, Sweden, Umeå, 09:00 (Engelska)
Opponent
Handledare
Tillgänglig från: 2016-08-26 Skapad: 2016-08-25 Senast uppdaterad: 2018-06-07Bibliografiskt granskad

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Bergström, FredrikEriksson, Johan

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