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The conscious brain: Empirical investigations of the neural correlates of perceptual awareness
Umeå University, Faculty of Social Sciences, Department of Psychology.
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Although consciousness has been studied since ancient time, how the brain implements consciousness is still considered a great mystery by most. This thesis investigates the neural correlates of consciousness by measuring brain activity with functional magnetic resonance imaging (fMRI) while specific contents of consciousness are defined and maintained in various experimental settings. Study 1 showed that the brain works differently when creating a new conscious percept compared to when maintaining the same percept over time. Specifically, sensory and fronto-parietal regions were activated for both conditions but with different activation patterns within these regions. This distinction between creating and maintaining a conscious percept was further supported by Study 2, which in addition showed that there are both differences and similarities in how the brain works when defining a visual compared to an auditory percept. In particular, frontal cortex was commonly activated while posterior cortical activity was modality specific. Study 3 showed that task difficulty influenced the degree of frontal and parietal cortex involvement, such that fronto-parietal activity decreased as a function of ease of identification. This is interpreted as evidence of the non-necessity of these regions for conscious perception in situations where the stimuli are distinct and apparent. Based on these results a model is proposed where sensory regions interact with controlling regions to enable conscious perception. The amount and type of required interaction depend on stimuli and task characteristics, to the extent that higher-order cortical involvement may not be required at all for easily recognizable stimuli.

Place, publisher, year, edition, pages
Umeå: Psykologi , 2007. , 68 p.
Series
Umeå studies in cognitive science, ISSN 1654-2568 ; 4
Keyword [en]
consciousness, visual perception, object identification, functional neuroimaging, top-down processing, prefrontal cortex, auditory perception
National Category
Neurosciences
Identifiers
URN: urn:nbn:se:umu:diva-1430ISBN: 978-91-7264-457-1 (print)OAI: oai:DiVA.org:umu-1430DiVA: diva2:141028
Public defence
2007-12-07, MA 121, MIT-huset, Umeå Universitet, Umeå, 10:15
Opponent
Supervisors
Available from: 2007-11-13 Created: 2007-11-13 Last updated: 2011-01-27Bibliographically approved
List of papers
1. Visual consciousness: dissociating the neural correlates of perceptual transitions from sustained perception with fMRI
Open this publication in new window or tab >>Visual consciousness: dissociating the neural correlates of perceptual transitions from sustained perception with fMRI
2004 (English)In: Consciousness and Cognition, ISSN 1053-8100, E-ISSN 1090-2376, Vol. 13, no 1, 61-72 p.Article in journal (Refereed) Published
Abstract [en]

To investigate the possible dichotomy between the neurophysiological bases of perceptual transitions versus sustaining a particular percept over time, an fMRI study was conducted with subjects viewing fragmented pictures. Unlike most other perceptually unstable stimuli, fragmented pictures give rise to only one perceptual transition and a continuous period of sustained perception. Earlier research is inconclusive on the subject of which anatomical regions should be attributed to what temporal aspect of perception, and the aim of the present study was to shed more light on the subject. In this study occipitotemporal and fronto-parietal regions were found to be activated for both aspects. However, regions in the medial-temporal lobe were activated specifically for transitions, whereas medial and dorsolateral prefrontal regions were activated specifically for sustained perception. These results provide further support for the theory that the initial creation of perceptual awareness and upholding perceptual awareness over time are separate processes involving different brain regions.

Place, publisher, year, edition, pages
San Diego, Calif.: Academic Press, 2004
National Category
Neurosciences
Identifiers
urn:nbn:se:umu:diva-14902 (URN)10.1016/S1053-8100(03)00050-3 (DOI)14990241 (PubMedID)
Available from: 2007-02-23 Created: 2007-02-23 Last updated: 2017-12-14Bibliographically approved
2. Similar frontal and distinct posterior cortical regions mediate visual and auditory perceptual awareness
Open this publication in new window or tab >>Similar frontal and distinct posterior cortical regions mediate visual and auditory perceptual awareness
2007 (English)In: Cerebral Cortex, ISSN 1047-3211, E-ISSN 1460-2199, Vol. 17, no 4, 760-765 p.Article in journal (Refereed) Published
Abstract [en]

Activity in ventral visual cortex is a consistent neural correlate of visual consciousness. However, activity in this area seems insufficient to produce awareness without additional involvement of frontoparietal regions. To test the generality of the frontoparietal response, neural correlates of auditory awareness were investigated in a paradigm that previously has revealed frontoparietal activity during conscious visual perception. A within-experiment comparison showed that frontal regions were related to both visual and auditory awareness, whereas parietal activity was correlated with visual awareness and superior temporal activity with auditory awareness. These results indicate that frontal regions interact with specific posterior regions to produce awareness in different sensory modalities.

Keyword
auditory awareness, fMRI, parietal cortex, prefrontal cortex, visual awareness
National Category
Neurosciences
Identifiers
urn:nbn:se:umu:diva-2762 (URN)10.1093/cercor/bhk029 (DOI)
Available from: 2007-11-13 Created: 2007-11-13 Last updated: 2017-12-14Bibliographically approved
3. Item-specific training reduces prefrontal cortical involvement in perceptual awareness
Open this publication in new window or tab >>Item-specific training reduces prefrontal cortical involvement in perceptual awareness
(English)Manuscript (Other academic)
Identifiers
urn:nbn:se:umu:diva-2763 (URN)
Available from: 2007-11-13 Created: 2007-11-13 Last updated: 2010-06-23Bibliographically approved

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CiteExportLink to record
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Citation style
  • apa
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Output format
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