| 1. |
- Kompus, Kristiina
(author)
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Default mode network gates the retrieval of task-irrelevant incidental memories
- 2011
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In: Neuroscience Letters. - : Elsevier. - 0304-3940 .- 1872-7972. ; 487:3, s. 318-321
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Journal article (peer-reviewed)abstract
- Episodic memories can be retrieved by an intentional search for certain information. Alternatively, a past episode may enter our consciousness without any intention to retrieve it, prompted by a stimulus in our surroundings. Incidental retrieval does not occur upon each encounter with a familiar stimulus, suggesting that a gating mechanism exists which regulates incidental retrieval activity. We analyzed data from a functional magnetic resonance imaging study on incidental retrieval in healthy young adults and found that failure to incidentally retrieve was selectively associated with reduced activation of lateral and medial parietal regions as well as ventromedial frontal cortex, areas implicated in default mode network. This is the first demonstration that relative deactivation of the brain regions associated with the default mode gates the consciousness from currently irrelevant memories.
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| 2. |
- Kompus, Kristiina, et al.
(author)
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Deficits in inhibitory executive functions in Klinefelter (47, XXY) syndrome
- 2011
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In: Psychiatry Research. - : Elsevier BV. - 0165-1781 .- 1872-7123. ; 189:1, s. 135-140
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Journal article (peer-reviewed)abstract
- Klinefelter syndrome (47, XXY) is a sex chromosome aneuploidy associated with mild deficits in cognitive and language functions. Dysfunctions have also been reported in performance of tasks which examine executive functions. However, it is unclear whether the impaired performance is caused or accentuated by problems with semantic processing and information processing speed. In the present study we used an experimental task which is relatively insensitive to these confounding factors. We examined inhibitory executive functions in a group of XXY males compared with male (XY) and female (XX) controls, using a dichotic listening speech sound task with instructions to focus attention on either the right or the left ear stimulus. With this task, inhibitory executive functions can be assessed separately from language, processing speed, and attention orientation abilities. We found that XXY males showed a selective deficit in inhibitory executive functions compared to both control groups, whereas attentional orientation was not impaired. The present findings suggest that executive dysfunctions associated to Klinefelter syndrome can be selectively identified, and are particularly accentuated in the inhibitory sub-component. Such improved understanding of the nature of executive dysfunctions in XXY males may aid the development of specific neuropsychological rehabilitation strategies.
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| 3. |
- Kompus, Kristiina, 1983-, et al.
(author)
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Multimodal imaging of incidental retrieval : the low route to memory
- 2011
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In: Journal of cognitive neuroscience. - : MIT Press - Journals. - 0898-929X .- 1530-8898. ; 23:4, s. 947-960
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Journal article (peer-reviewed)abstract
- Memories of past episodes frequently come to mind incidentally, without directed search. It has remained unclear how incidental retrieval processes are initiated in the brain. Here we used fMRI and ERP recordings to find brain activity that specifically correlates with incidental retrieval, as compared to intentional retrieval. Intentional retrieval was associated with increased activation in the dorsolateral prefrontal cortex. By contrast, incidental retrieval was associated with a reduced fMRI signal in posterior brain regions, including extrastriate and parahippocampal cortex, and a modulation of a posterior ERP component 170 ms after the onset of visual retrieval cues. Successful retrieval under both intentional and incidental conditions was associated with increased activation in hippocampus, precuneus and ventrolateral prefrontal cortex, as well as increased amplitude of the P600 ERP component. These results demonstrate how early bottom-up signals from the posterior cortex can lead to reactivation of episodic memories in the absence of strategic retrieval attempts.
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| 4. |
- Kompus, Kristiina, et al.
(author)
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The size of the anterior corpus callosum correlates with the strength of hemispheric encoding-retrieval asymmetry in the ventrolateral prefrontal cortex
- 2011
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In: Brain Research. - Amsterdam : Elsevier BV. - 0006-8993 .- 1872-6240. ; 1419, s. 61-67
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Journal article (peer-reviewed)abstract
- Functional lateralization of episodic memory processes in the frontal lobe is an area of intense study in the field of cognitive neuroimaging. Yet, to date there is insufficient knowledge of what role the interhemispheric structural connectivity plays in this lateralized organization. We analyzed functional and structural magnetic resonance imaging data from healthy adult volunteers who performed an associative encoding and retrieval task. We examined the relationship between functional voxel-based relative asymmetry of encoding and retrieval in the frontal lobes and the size of the anterior corpus callosum (antCC; corrected for brain size). The size of the antCC was strongly associated to the relative encoding-retrieval asymmetry in the ventrolateral prefrontal cortex (BA 47). These findings show that the functional asymmetry of episodic memory processes in the frontal lobes is associated with the structural connectivity between the hemispheres.
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