| 1. |
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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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| 3. |
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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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| 5. |
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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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| 8. |
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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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| 11. |
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| 12. |
- Moberget, Torgeir, et al.
(författare)
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Detecting violations of sensory expectancies following cerebellar degeneration
- 2008
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Ingår i: Neuropsychologia. - : Elsevier BV. - 1873-3514 .- 0028-3932. ; 46:10, s. 2569-2579
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Tidskriftsartikel (refereegranskat)abstract
- Two hypotheses concerning cerebellar function and predictive behavior are the sensory prediction hypothesis and the timing hypothesis. The former postulates that the cerebellum is critical in generating expectancies regarding forthcoming sensory information. The latter postulates that this structure is critical in generating expectancies that are precisely timed; for example, the expected duration of an event or the time between events. As such, the timing hypothesis constitutes a more specific form of prediction. The present experiment contrasted these two hypotheses by examining the mismatch negativity (MMN) response in patients with cerebellar cortical atrophy and matched controls. While watching a silent movie, a stream of task-irrelevant sounds was presented. A standard sound was presented 60% of the time, whereas the remaining sounds deviated from the standard on one of four dimensions: duration, intensity, pitch, or location. The timing between stimuli was either periodic or aperiodic. Based on the sensory prediction hypothesis, the MMN for the patients should be abnormal across all four dimensions. In contrast, the timing hypothesis would predict a selective impairment of the duration MMN. Moreover, the timing hypothesis would also predict that the enhancement of the MMN observed in controls when the stimuli are presented periodically should be attenuated in the patients. Compared to controls, the patients exhibited a delayed latency in the MMN to duration deviants and a similar trend for the intensity deviants, while pitch and location MMNs did not differ between groups. Periodicity had limited and somewhat inconsistent effects. The present results are at odds with a general role for the cerebellum in sensory prediction and provide partial support for the timing hypothesis.
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| 13. |
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| 14. |
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| 15. |
- Persson, Jonas, et al.
(författare)
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Altered deactivation in individuals with genetic risk for Alzheimer's disease
- 2008
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Ingår i: Neuropsychologia. - : Elsevier BV. - 0028-3932 .- 1873-3514. ; 46:6, s. 1679-1687
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Tidskriftsartikel (refereegranskat)abstract
- Regions that show task-induced deactivations may be part of a default-mode network related to processes that are more engaged during passive than active task conditions. Alteration of task-induced deactivations with age and dementia is indicated by atypical engagement of default-mode network regions. Genetic studies show a relation between the apolipoprotein E4 (APOE4) allele and the common form of Alzheimer’s disease (AD), and altered functional brain activation has been observed in non-demented APOE4 carriers compared to non-carriers. Here we investigate the hypothesis of altered default-mode network brain responses in individuals with genetic risk for AD. Functional MRI was used to assess task-induced deactivation in 60 subjects of which 30 carried at least one copy of the APOE4 allele, and 30 non-carriers. Subjects were scanned while performing a semantic categorization task shown to promote episodic memory encoding. The results show patterns of deactivation consistent with the default-mode network. We also found reduced deactivation in non-demented APOE4 carriers compared to non-carriers, suggesting alterations in the default-mode network in the absence of dementia. These results implicate possibilities for investigatin altered properties of task-induced deactivations in individuals with genetic risk for AD, and may prove useful for pre-clinical identification of individuals susceptible to memory problems and AD.
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| 16. |
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| 17. |
- Rudner, Mary, et al.
(författare)
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Neural representation of binding lexical signs and words in the episodic buffer of working memory
- 2007
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Ingår i: Neuropsychologia. - Oxford : Elsevier BV. - 0028-3932 .- 1873-3514. ; 45:10, s. 2258-2276
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Tidskriftsartikel (refereegranskat)abstract
- The episodic buffer accommodates formation and maintenance of unitary multidimensional representations based on information in different codes from different sources. Formation, based on submorphemic units, engages posterior brain regions, while maintenance engages frontal regions. Using a hybrid fMRI design, that allows separate analysis of transient and sustained components, an n-back task and an experimental group of 13 hearing native signers, with experience of Swedish Sign Language and Swedish since birth, we investigated binding of lexical signs and words in working memory. Results show that the transient component of these functions is supported by a buffer-specific network of posterior regions including the right middle temporal lobe, possibly relating to binding of phonological loop representations with semantic representations in long-term memory, as well as a loop-specific network, in line with predictions of a functional relationship between loop and buffer. The left hippocampus was engaged in transient and sustained components of buffer processing, possibly reflecting the meaningful nature of the stimuli. Only a minor role was found for executive functions in line with other recent work. A novel representation of the sustained component of working memory for audiovisual language in the right inferior temporal lobe may be related to perception of speech-related facial gestures. Previous findings of sign and speech loop representation in working memory were replicated and extended. Together, these findings support the notion of a module that mediates between codes and sources, such as the episodic buffer, and further our understanding of its nature.
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| 18. |
- Rönnlund, Michael, 1967-, et al.
(författare)
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Flynn effects on sub-factors of episodic and semantic memory : Parallel gains over time and the same set of determining factors
- 2009
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Ingår i: Neuropsychologia. - : Elsevier. - 0028-3932 .- 1873-3514. ; 47:11, s. 2174-2180
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Tidskriftsartikel (refereegranskat)abstract
- The study examined the extent to which time-related gains in cognitive performance, so-called Flynn effects, generalize across sub-factors of episodic memory (recall and recognition) and semantic memory (knowledge and fluency). We conducted time-sequential analyses of data drawn from the Betula prospective cohort study, involving four age-matched samples (35–80 years; N = 2996) tested on the same battery of memory tasks on either of four occasions (1989, 1995, 1999, and 2004). The results demonstrate substantial time-related improvements on recall and recognition as well as on fluency and knowledge, with a trend of larger gains on semantic as compared with episodic memory [Rönnlund, M., & Nilsson, L. -G. (2008). The magnitude, generality, and determinants of Flynn effects on forms of declarative memory: Time-sequential analyses of data from a Swedish cohort study. Intelligence], but highly similar gains across the sub-factors. Finally, the association with markers of environmental change was similar, with evidence that historical increases in quantity of schooling was a main driving force behind the gains, both on the episodic and semantic sub-factors. The results obtained are discussed in terms of brain regions involved.
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| 19. |
- Tajadura, Ana, 1979, et al.
(författare)
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Auditory–somatosensory multisensory interactions are spatially modulated by stimulated body surface and acoustic spectra
- 2009
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Ingår i: Neuropsychologia. - : Elsevier BV. - 0028-3932. ; 47:1, s. 195-203
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Tidskriftsartikel (refereegranskat)abstract
- Previous research has provided inconsistent results regarding the spatial modulation of auditory–somatosensory interactions. The present study reports three experiments designed to investigate the nature of these interactions in the space close to the head. Human participants made speeded detection responses to unimodal auditory, somatosensory, or simultaneous auditory–somatosensory stimuli. In Experiment 1, electrocutaneous stimuli were presented to either earlobe, while auditory stimuli were presented from the same versus opposite sides, and from one of two distances (20 vs. 70 cm) from the participant's head. The results demonstrated a spatial modulation of auditory–somatosensory interactions when auditory stimuli were presented from close to the head. In Experiment 2, electrocutaneous stimuli were delivered to the hands, which were placed either close to or far from the head, while the auditory stimuli were again presented at one of two distances. The results revealed that the spatial modulation observed in Experiment 1 was specific to the particular body part stimulated (head) rather than to the region of space (i.e. around the head) where the stimuli were presented. The results of Experiment 3 demonstrate that sounds that contain high-frequency components are particularly effective in eliciting this auditory–somatosensory spatial effect. Taken together, these findings help to resolve inconsistencies in the previous literature and suggest that auditory–somatosensory multisensory integration is modulated by the stimulated body surface and acoustic spectra of the stimuli presented.
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| 20. |
- Warkentin, Siegbert, et al.
(författare)
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rCBF pathology in Alzheimer's disease is associated with slow processing speed
- 2008
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Ingår i: Neuropsychologia. - : Elsevier BV. - 1873-3514 .- 0028-3932. ; 46:5, s. 1193-1200
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Tidskriftsartikel (refereegranskat)abstract
- Decreased information processing speed (mental slowing) is a known sequelae of many brain disorders, and can be assessed by continuous naming tasks. Functional imaging studies have shown that pause and articulation times in continuous speech are normally associated with different brain regions, but knowledge about such association in dementia is lacking. We therefore tested the hypothesis that perfusion deficits in Alzheimer's disease (AD) are not only associated with slower processing, but also with these speech measures. Using regional cerebral blood flow (rCBF) measurements during the performance of a continuous colour and form-naming task, we found that naming speed was substantially slower in AD patients than in controls. This slower naming was exclusively determined by an increase in mean pause time, and only to a limited extent by articulation time. The increased pause time was uniquely associated with temporo-parietal rCBF reductions of the patients, while articulation was not. By contrast, the rCBF of healthy elderly control subjects was consistently accompanied by substantially shorter articulation and pause times, although the naming measures were not statistically associated with rCBF. These findings suggest that pause time (in contrast to articulation time) may serve as a sensitive measure in the assessment of information processing speed deficits in dementia, by virtue of its close association with brain pathology. (C) 2007 Elsevier Ltd. All rights reserved.
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