The moderating influence of extraversion on the relationship between IQ and cortical activation

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 alpha band ERD to individual differences in cognition

According to the neural efficiency hypothesis, brighter individuals might be characterized by lower and topographically more differentiated brain activation than less intelligent individuals, presumably reflecting a more specialized recruitment of task-related areas. The findings of several studies analyzing the event-related desynchronization (ERD) in the (upper) alpha frequency band have corroborated and elaborated the original neural efficiency hypothesis. In this chapter, we review classical and recent findings and argue in favor of a more differentiated picture of this phenomenon, emphasizing the role of participants' sex, task complexity, and material specificity, as well as the importance to select an adequate external criterion (intelligence measure). Also, recent ERD findings related to emotional intelligence and creativity as well as recent studies focusing on practice, learning ability, and expertise are presented, which point to the need of a broader neurophysiological ability concept. The reviewed findings point at the high suitability of the ERD method to uncover consistent and stable individual differences in people's brain activation patterns when engaged in performing cognitively demanding tasks.

Individual differences in brain activity during visuo-spatial processing assessed by slow cortical potentials and LORETA

Using slow-cortical potentials (SCPs), Vitouch et al. demonstrated that subjects with low ability to solve a complex visuo-spatial imagery task show higher activity in occipital, parietal and frontal cortex during task processing than subjects with high ability. This finding has been interpreted in the sense of the so-called "neural efficiency" hypothesis, which assumes that the central nervous system of individuals with higher intellectual abilities is functioning in a more efficient way than the one of individuals with lower abilities. Using a higher spatial resolution of SCP recordings, and by employing the source localization method of LORETA (low-resolution electromagnetic tomography), we investigated this hypothesis by performing an extended replication of Vitouch et al.'s study. SCPs during processing of a visuo-spatial imagery task were recorded in pre-selected subjects with either high or low abilities in solving the imagery task. Topographic and LORETA analyses of SCPs revealed that a distributed network of extrastriate occipital, superior parietal, temporal, medial frontal and prefrontal areas was active during task solving. This network is well in line with former studies of the functional neuroanatomy of visuo-spatial imagery. Contrary to our expectations, however, the results of Vitouch et al. as well as of other studies supporting the neural efficiency hypothesis could not be confirmed since no difference in brain activity between groups was observed. This inconsistency between studies might be due to differing task processing strategies. While subjects with high abilities in the Vitouch et al. study seemed to use a visuo-perceptual task solving approach, all other subjects relied upon a visuo-motor task processing strategy.

Event-related desynchronization in the EEG during emotional and cognitive information processing: differential effects of extraversion

The aim of the present study was to analyze the influence of the personality dimension extraversion/introversion (E) on the level and topographical distribution of event-related desynchronization (ERD) in the EEG whilst participants were engaged in emotional face and cognitive information processing. In this context we build up on former studies dealing with the role of E as a possible moderator variable in cortical activation patterns during performance of mental speed, reasoning and working memory tasks (i.e., cognitive information processing). In a sample of 33 introverts and 33 extraverts (31 were male, 35 female) we found extraverted individuals displaying a lower (left-hemispheric) cortical activation than introverts when their task was to judge the identity of two simultaneously presented facial emotions. This effect was only observed in the upper alpha frequency band ( approximately 9.6-11.6 Hz). In analyzing E differences during cognitive information processing (i.e., performance of a verbal and a figural-spatial task) E effects - which were moderated by participants' sex - were restricted to lower EEG (alpha) frequency ranges ( approximately 5.6-9.6 Hz). The results generally suggest that E is differently involved when different kinds of information are processed.

Personality traits and its association with resting regional brain activity

The association between personality and resting brain activity was investigated. Personality was assessed using the NEO-Five-factor Inventory (NEO-FFI) and resting brain activity was indexed by eyes closed EEG spectral magnitude from four frequency bands over the entire cortex. Results suggest that there are differences between males and females in the NEO-FFI personality traits. The NEO FFI traits were associated with lower frequency brain activity in both males and females. Mild significant and consistent associations were found between delta and theta activity across all cortical regions with Extraversion and Conscientiousness. There were few associations between personality traits and alpha and beta activity, this was shown in males only. Fewer associations between personality and faster frequency bands such as alpha may be due to the methodological problem of using fixed alpha bands. Multiple regression analyses showed that individual alpha frequencies had a greater contribution to personality traits than fixed band alpha waves.

Extraversion and cortical activation during memory performance

In this study we analyzed the influence of the personality dimension extraversion-introversion (E) on the level and topographical distribution of cortical activation. In 62 participants (32 introverts and 30 extraverts), we measured the extent of Event-Related Desynchronization (ERD) in the EEG during performance of a short-term memory (i.e., temporary maintenance of information) and a more complex working memory task (i.e., temporary maintenance and active manipulation of information). The results indicate that during performance of both tasks, introverts display a larger amount of ERD than extraverted individuals. Moreover, the present E effects largely match previous studies as to the restriction of these effects to lower EEG frequency ranges (approx. 4-8 Hz). Topographical analyses show that the E effects are primarily present over (right-hemispheric) frontal and parietal regions of the cerebral cortex.

EEG alpha band dissociation with increasing task demands

In assuming functional differences between different EEG alpha frequency bands, recent studies emphasize the importance of using narrow (8-10 Hz or 10-12 Hz) instead of broad alpha frequency ranges (8-12 Hz). Due to individual differences in alpha activity, it has also been suggested to adjust alpha frequency bands individually for each participant. The present paper highlights the dissociating role of different task demands on the extent of event-related desynchronization (ERD) in different alpha frequency bands. In analyzing the data of four large-scale EEG studies (with sample sizes of 51, 58, 55, and 66, respectively) employing a wide range of cognitive tasks, we found evidence that the correlations between lower and upper alpha band ERD systematically decline as task demands increase.

When intelligence loses its impact: neural efficiency during reasoning in a familiar area

Several studies have revealed that persons with a lower IQ show more cortical activity when solving intelligence-related tasks than more intelligent persons do. Such results are interpreted in terms of neural efficiency: the more intelligent a person is, the fewer mental resources have to be activated. In an experiment with 31 experienced taxi drivers of varying IQs (measured by Raven's advanced progressive matrices test), we investigated cortical activation by measuring the amount of event-related desynchronization in the electroencephalogram during a familiar task (thinking about routes to take in their city) and a novel task (memorizing routes of an artificial map). A comparison of participants with lower and higher IQs (median split) revealed higher cortical activation in the less intelligent group for the novel task, but not for the familiar task. These results suggest that long-term experience can compensate for lower intellectual ability, even at the level of cortical activation.