Roland H. Grabner

To retrieve or to calculate? Left angular gyrus mediates the retrieval of arithmetic facts during problem solving.

While there is consistent evidence from neuropsychological and brain imaging studies for an association between the left angular gyrus and mental arithmetic, its specific role in calculation has remained poorly understood. It has been speculated that the angular gyrus mediates the retrieval of arithmetic facts during problem solving, but this hypothesis has not been directly tested. In the present functional Magnetic Resonance Imaging study comprising 28 adults, we used trial-by-trial strategy self-reports to identify brain regions underpinning different strategies in arithmetic problem solving. Analyses revealed stronger activation of the left angular gyrus while solving arithmetic problems for which participants reported fact retrieval whereas the application of procedural strategies was accompanied by widespread activation in a fronto-parietal network. These data directly link the left angular gyrus with arithmetic fact retrieval and show that strategy self-reports can be used to predict differential patterns of brain activation.

The creative brain: Investigation of brain activity during creative problem solving by means of EEG and FMRI

Cortical activity in the EEG alpha band has proven to be particularly sensitive to creativity‐related demands, but its functional meaning in the context of creative cognition has not been clarified yet. Specifically, increases in alpha activity (i.e., alpha synchronisation) in response to creative thinking can be interpreted in different ways: As a functional correlate of cortical idling, as a sign of internal top‐down activity or, more specifically, as selective inhibition of brain regions. We measured brain activity during creative thinking in two studies employing different neurophysiological measurement methods (EEG and fMRI). In both studies, participants worked on four verbal tasks differentially drawing on creative idea generation. The EEG study revealed that the generation of original ideas was associated with alpha synchronisation in frontal brain regions and with a diffuse and widespread pattern of alpha synchronisation over parietal cortical regions. The fMRI study revealed that task performance was associated with strong activation in frontal regions of the left hemisphere. In addition, we found task‐specific effects in parietotemporal brain areas. The findings suggest that EEG alpha band synchronisation during creative thinking can be interpreted as a sign of active cognitive processes rather than cortical idling. Hum Brain Mapp, 2009.

Individual differences in mathematical competence predict parietal brain activation during mental calculation

Functional neuroimaging studies have revealed that parietal brain circuits subserve arithmetic problem solving and that their recruitment dynamically changes as a function of training and development. The present study investigated whether the brain activation during mental calculation is also modulated by individual differences in mathematical competence. Twenty-five adult students were selected from a larger pool based on their performance on standardized tests of intelligence and arithmetic and divided into groups of individuals with relatively lower and higher mathematical competence. These groups did not differ in their non-numerical intelligence or age. In an fMRI block-design, participants had to verify the correctness of single-digit and multi-digit multiplication problems. Analyses revealed that the individuals with higher mathematical competence displayed stronger activation of the left angular gyrus while solving both types of arithmetic problems. Additional correlational analyses corroborated the association between individual differences in mathematical competence and angular gyrus activation, even when variability in task performance was controlled for. These findings demonstrate that the recruitment of the left angular gyrus during arithmetic problem solving underlies individual differences in mathematical ability and suggests a stronger reliance on automatic, language-mediated processes in more competent individuals.

Enhancing creativity by means of cognitive stimulation: Evidence from an fMRI study.

Cognitive stimulation via the exposure to ideas of other people is an effective tool in stimulating creativity in group-based creativity techniques. In this fMRI study, we investigate whether creative cognition can be enhanced through idea sharing and how performance improvements are reflected in brain activity. Thirty-one participants had to generate alternative uses of everyday objects during fMRI recording. Additionally, participants performed this task after a time period in which they had to reflect on their ideas or in which they were confronted with stimulus-related ideas of others. Cognitive stimulation was effective in improving originality, and this performance improvement was associated with activation increases in a neural network including right-hemispheric temporo-parietal, medial frontal, and posterior cingulate cortices, bilaterally. Given the involvement of these brain areas in semantic integration, memory retrieval, and attentional processes, cognitive stimulation could have resulted in a modulation of bottom-up attention enabling participants to produce more original ideas.

Superior performance and neural efficiency : The impact of intelligence and expertise

Superior cognitive performance can be viewed from an intelligence perspective, emphasising general properties of the human information processing system (such as mental speed and working memory), and from an expertise perspective, highlighting the indispensable role of elaborated domain-specific knowledge and acquired skills. In exploring its neurophysiological basis, recent research has provided considerable evidence of the neural efficiency hypothesis of intelligence, indicating lower and more focussed brain activation in brighter individuals. The present EEG study investigates the impacts of intelligence and expertise on cognitive performance and the accompanying cortical activation patterns in the domain of tournament chess. Forty-seven tournament chess players of varying intelligence and expertise level worked on tasks drawing on mental speed, memory, and reasoning. Half of the tasks were representative for chess, while the other half was not. The cortical activation was quantified by means of event-related desynchronisation (ERD) in the upper alpha band. Independent effects of expertise and intelligence emerged at both, the performance and the neurophysiological level. Brighter participants performed better than less intelligent ones which was associated with more efficient brain functioning (lower ERD) across all tasks. Additionally, a high expertise level was beneficial for good task performance but exerted a topographically differentiated influence on the cortical activation patterns. The findings suggest that superior cognitive performance and the underlying cortical activation are not only a function of knowledge and domain-specific competences but also of the general efficiency of the information processing system.

Sensitivity of human EEG alpha band desynchronization to different working memory components and increasing levels of memory load

Event-related alpha band desynchronization is frequently used to analyze spatiotemporal cortical activation patterns during the performance of cognitive tasks. In the present paper the sensitivity of alpha band desynchronization to increasing levels of cognitive load and to different cognitive working memory components is investigated. A 27-channel electroencephalogram of 62 participants while solving (a) a short-term memory and (b) a working memory task (dual task), each with five levels of memory load, was analyzed. We found (a) a linearly increasing desynchronization in the upper alpha band with ascending cognitive load, and (b) evidence of the involvement of distinguishable cognitive components (storage and controlled attention) in the memory tasks.

Divergent thinking training is related to frontal electroencephalogram alpha synchronization.

Cortical activity in the human electroencephalogram alpha band was measured (by means of an event‐related approach) in a pre‐ and a post‐test (with intermediate training) while participants (n = 30) were confronted with divergent thinking tasks. Half of the participants received a divergent thinking training (over a time period of 2 weeks) which was composed of exercises structurally similar to those used in the pre‐ and post‐test. Analyses revealed that the training group displayed higher task‐related synchronization of frontal alpha activity (i.e. increases in alpha power from the pre‐stimulus reference to the activation interval) than the control group. These findings are in line with the view of frontal alpha synchronization as a selective top–down inhibition process that prevents internal or top–down information processing being disturbed by incoming external input.

Brain correlates of self-rated originality of ideas : Evidence from event-related power and phase-locking changes in the EEG

In the present study, we contrast oscillatory brain activity during the production of subjectively more versus less original ideas. A sample of 26 participants worked on two verbal creativity problems and subsequently rated the produced ideas with respect to their originality. On the basis of these self-ratings, ideas were divided into a more and a less original list within each participant. Cortical activity was assessed by means of event-related changes in EEG power (synchronization and desynchronization) and phase locking in two alpha bands. Analyses revealed that more, as compared with less, original ideas elicited a stronger event-related synchronization of alpha activity (power increases from the pre-stimulus reference to the activation interval) and higher phase coupling in the right hemisphere. These findings corroborate the importance of right-hemispheric cortical networks in creative idea generation.

Fact learning in complex arithmetic and figural-spatial tasks: the role of the angular gyrus and its relation to mathematical competence.

Neuroimaging studies have revealed a strong link between mental calculation and the angular gyrus (AG) which has been interpreted to reflect arithmetic fact retrieval. Moreover, a stronger AG activation in individuals with higher mathematical competence has been reported. The present fMRI study investigates the specificity of the AG for arithmetic fact learning and the interplay between training and mathematical competence on brain activation. Adults of lower and higher mathematical competence underwent a five‐day training on sets of complex multiplication and figural‐spatial problems. In the following fMRI test session, trained and untrained problems were presented. Similar training effects were observed in both problem types, consisting of AG activation increases bilaterally and wide‐spread activation decreases in frontal and parietal regions. This finding indicates that the AG is not specifically involved in the learning of arithmetic facts. Competence‐related differences in the AG only emerged in untrained but not in trained multiplication problems. The relation between AG activation and mathematical competence in arithmetic problem solving therefore seems to be due to differences in arithmetic fact retrieval which can be attenuated through training. Hum Brain Mapp 2009.

Long-term stability and consistency of EEG event-related (de-)synchronization across different cognitive tasks.

OBJECTIVE We examined whether task-related band power changes (event-related desynchronization/synchronization; ERD/ERS) that have been linked to individual differences in cognitive ability demonstrate satisfying temporal stability and cross-situational consistency. METHODS Multi-channel EEG recordings from 29 adults, assessed at three different occasions over 2 years were examined. Between-session correlations and consistency coefficients (Cronbachs alpha) across the three experiments were evaluated for both, spectral power features of the resting EEG and ERD/ERS estimates while the participants performed some cognitive task (i.e. different elementary cognitive tasks that put comparable demands on the participants). RESULTS ERD/ERS values, while subjects performed a cognitive task, demonstrated satisfactory stability and consistency (i.e. >0.7), whereby the degree of consistency varied as a function of frequency band and brain region. Highest consistency was found for the 8-10 Hz ERD in parieto-occipital recording sites (i.e. >0.9). In resting EEG, mean alpha (gravity) frequency was the most stable EEG feature. CONCLUSIONS The present data suggest that ERD/ERS phenomena in different narrow frequency bands are rather stable over time and across different situations. The relatively high reproducibility of ERD/ERS promotes the usefulness of this measure in assessing individual differences of physiological activation patterns accompanying cognitive performance. SIGNIFICANCE This study addresses the issue of reproducibility of EEG in general and ERD/ERS experiments in particular, which is a prerequisite for both basic research and clinical studies.