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| 2. |
- Fingelkurts, Andrew, et al.
(författare)
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Cortex Functional Connectivity as a Neurophysiological Correlate of Hypnosis : an EEG Case Study
- 2007
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Ingår i: Neuropsychologia. - : Elsevier. - 0028-3932 .- 1873-3514. ; 45:7, s. 1452-1462
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Tidskriftsartikel (refereegranskat)abstract
- Cortex functional connectivity associated with hypnosis was investigated in a single highly hypnotizable subject in a normal baseline condition and under neutral hypnosis during two sessions separated by a year. After the hypnotic induction, but without further suggestions as compared to the baseline condition, all studied parameters of local and remote functional connectivity were significantly changed. The significant differences between hypnosis and the baseline condition were observable (to different extent) in five studied independent frequency bands (delta, theta, alpha, beta, and gamma). The results were consistent and stable after 1 year. Based on these findings we conclude that alteration in functional connectivity of the brain may be regarded as a neuronal correlate of hypnosis (at least in very highly hypnotizable subjects) in which separate cognitive modules and subsystems may be temporarily incapable of communicating with each other normally
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| 4. |
- Jordan, Timothy R, et al.
(författare)
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Assessing effects of fixation demands on perception of lateralized words: a visual window technique for studying hemispheric asymmetry.
- 2006
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Ingår i: Neuropsychologia. - : Elsevier BV. - 0028-3932. ; 44:5, s. 686-692
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Tidskriftsartikel (refereegranskat)abstract
- A major concern when using lateralized words to study hemispheric asymmetry is that the retinal eccentricity of targets is matched across visual hemifields. The standard technique is to fixate a point fixed at the centre of the visual field. However, the demands of this fixation task are substantial and so may confound performance with lateralized targets. To investigate this possibility, words were presented unilaterally in each visual hemifield and retinal eccentricity was controlled using (a) a fixed central point or (b) a window technique that permitted small shifts in fixation while maintaining accurate retinal eccentricity by using automatic adjustments to target location. Fixation errors and time to fixate indicated that the demands of the standard technique were considerable and far greater than those of the window technique. Nevertheless, both techniques produced the same pattern of visual field effects, indicating that the demands of fixating a fixed central point do not confound performance with lateralized words. However, the window technique was more efficient and easier for participants to use and so offers a new improved methodology for studying hemispheric asymmetry.
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| 6. |
- Koivisto, Mika, et al.
(författare)
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The relationship between awareness and attention : Evidence from ERP responses
- 2009
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Ingår i: Neuropsychologia. - : Elsevier. - 0028-3932 .- 1873-3514. ; 47:13, s. 2891-2899
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Tidskriftsartikel (refereegranskat)abstract
- The relationship between attention and awareness is complex, because both concepts can be understood in different ways. Here we review our recent series of experiments which have tracked the independent contributions of different types of visual attention and awareness to electrophysiological brain responses, and then we report a new experiment focusing on spatial attention, nonspatial selection of objects, and visual consciousness at the same time. The results indicate that the earliest electrophysiological correlate of consciousness, assumed to correlate with “phenomenal consciousness”, was dependent on spatial attention, suggesting that spatial attention is a prerequisite for the internal representations of space that provide the medium for phenomenal experience. The correlate of phenomenal consciousness emerged independent of nonspatial selection of objects, but its later part was modified by it. By contrast, the correlate of access to later conscious processing stages (“reflective consciousness”) that take the selected contents of phenomenal consciousness as input for conceptual thought and working memory, was dependent on both spatial attention and nonspatial selection. These results imply that one should distinguish between different types of attention and different forms of awareness, when describing the relationship between attention and awareness.
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| 7. |
- Kompus, Kristiina, 1983-, et al.
(författare)
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Dynamic switching between semantic and episodic memory systems
- 2009
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Ingår i: Neuropsychologia. - : Elsevier BV. - 0028-3932 .- 1873-3514. ; 47:11, s. 2252-2260
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Tidskriftsartikel (refereegranskat)abstract
- It has been suggested that episodic and semantic long-term memory systems interact during retrieval. Here we examined the flexibility of memory retrieval in an associative task taxing memories of different strength, assumed to differentially engage episodic and semantic memory. Healthy volunteers were pre-trained on a set of 36 face-name pairs over a 6-week period. Another set of 36 items was shown only once during the same time period. About 3 months after the training period all items were presented in a randomly intermixed order in an event-related fMRI study of face-name memory. Once presented items differentially activated anterior cingulate cortex and a right prefrontal region that previously have been associated with episodic retrieval mode. High-familiar items were associated with stronger activation of posterior cortices and a left frontal region. These findings fit a model of memory retrieval by which early processes determine, on a trial-by-trial basis, if the task can be solved by the default semantic system. If not, there is a dynamic shift to cognitive control processes that guide retrieval from episodic memory.
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| 9. |
- MacDonald, Stuart W S, et al.
(författare)
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Extrastriatal dopamine D2 receptor binding modulates intraindividual variability in episodic recognition and executive functioning.
- 2009
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Ingår i: Neuropsychologia. - : Elsevier BV. - 0028-3932 .- 1873-3514. ; 47:11, s. 2299-2304
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Tidskriftsartikel (refereegranskat)abstract
- Intraindividual variability (IIV) reflects lawful but transient within-person changes in performance. Increased IIV in cognition shares systematic associations with numerous conditions characterized by alterations in dopamine (DA) neuromodulation (e.g., old age, ADHD, schizophrenia, and Parkinson's disease). In a group of normal middle-aged adults, we examined links between PET-derived measures of D2 receptor binding in striatum, orbitofrontal cortex (OFC), anterior cingulate cortex (ACC), and hippocampus (HC) and IIV for tasks assessing recognition memory and executive functioning. An index of IIV, the intraindividual standard deviation (ISD), was computed across successful response latency trials for each cognitive outcome. Lower D2 binding in OC, ACC, and HC, but not striatum, was associated with increasing ISDs for the memory and executive measures. Consistent with neurocomputational models, the present findings suggest a role for extrastriatal DA neurotransmission in modulating variability in cognitive functioning.
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| 10. |
- McNab, Fiona, et al.
(författare)
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Common and unique components of inhibition and working memory : An fMRI, within-subjects investigation
- 2008
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Ingår i: Neuropsychologia. - : Elsevier BV. - 0028-3932 .- 1873-3514. ; 46:11, s. 2668-2682
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Tidskriftsartikel (refereegranskat)abstract
- Behavioural findings indicate that the core executive functions of inhibition and working memory are closely linked, and neuroimaging studies indicate overlap between their neural correlates. There has not, however, been a comprehensive study, including several inhibition tasks and several working memory tasks, performed by the same subjects. In the present study, 11 healthy adult subjects completed separate blocks of 3 inhibition tasks (a stop task, a go/no-go task and a flanker task), and 2 working memory tasks (one spatial and one verbal). Activation common to all 5 tasks was identified in the right inferior frontal gyrus, and, at a lower threshold, also the right middle frontal gyrus and right parietal regions (BA 40 and BA 7). Left inferior frontal regions of interest (ROIs) showed a significant conjunction between all tasks except the flanker task. The present study could not pinpoint the specific function of each common region, but the parietal region identified here has previously been consistently related to working memory storage and the right inferior frontal gyrus has been associated with inhibition in both lesion and imaging studies. These results support the notion that inhibitory and working memory tasks involve common neural components, which may provide a neural basis for the interrelationship between the two systems.
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