´Neural Efficiency´ of the brain as physiological basis of human intelligence?

The project "Intelligence and Neural Efficiency" aims at a comprehensive inquiry into the physiological bases of human intelligence. Recent studies measuring the spatial distribution of cortical activation during performance of cognitive tasks (by means of positron emission tomography and topographical EEG mapping methods) have suggested that more intelligent (vs. less intelligent) participants use their brain in a more efficient way, by displaying a more strongly localised or focused activation and, consequently, less overall cortical activation when performing the same cognitive tasks. In some of these studies so-called elementary cognitive tasks (ECTs) have been used. These were designed to assess the basic speed of information processing, which has been found to be systematically correlated with intelligence (a high speed of processing is associated with high psychometric intelligence). Apart from the general findings on neural efficiency, however, many questions regarding this brain- intelligence relationship are unanswered. In a series of five experiments we plan to study the influence of five factors that possibly determine the relations between intellectual ability and the spatial patterns of cortical activation during cognitive performance: 1. The effects of the ECT complexity; 2. The influence of ECT-specificity or content (verbal vs. numerical vs. figural); 3. The spatial distribution of cortical activation during working memory tasks known to correlate substantially with psychometric intelligence test performance; 4. The relation of learning ability (known to be related to psychometric intelligence) to cortical activation; 5. The effects of age on cortical activation patterns (which might inform about the physiological basis of the intellectual development with age). In all five experiments we plan to compare several EEG measures between participant groups of different intellectual ability (as determined by an IQ test): The main focus is on the "Event Related Desynchronisation mapping", i.e. the spatial distribution of the event- related decrease in EEG alpha power. In addition, the individual alpha-peak frequency (IAF), EEG coherence measures and Evoked Potentials (EP) shall be analysed. The final goal of the project is the development of a theory of how human individuals of lower vs. higher cognitive ability use their brains when confronted with tasks of different processing requirements that might vary quantitatively or qualitatively.

Human intelligence and especially the IQ (intelligence quotient) is among the most widely but also controversially discussed topics of modern psychology. More than a century of scientific inquiry into this topic has produced a quite substantial body of empirical findings regarding the structure of human cognitive abilities, its development with age, as well as its measurement and implications for real-world behavior like success in education and profession but also in general "life success". Comparatively little, however, is known about the underlying neurophysiological basis of individual differences in cognitive ability. It was in the last 15 years that studies using electrophysiological measurements of the brain during thinking and problem solving gave rise to the so-called neural efficiency concept of human intelligence. Employing various physiological methods like Positron Emission Tomography (PET), functional Magnetic Resonance Imaging (fMRI) as well as special EEG-methods it was demonstrated that brighter individuals need less resources of brain activation during problem solving as compared to less bright individuals, a finding interpreted as brighter individuals displaying a higher neural efficiency. Based on these findings the project more deeply investigated this issue by studying the effects of the type (e.g. verbal, numerical, visuo-spatial) and complexity of the task, effects of learning and the meaning of knowledge and expertise. Cognitive "subcomponents" of intelligence like aspects of working memory were related to brain activation by means of topographical EEG mapping (event-related Desynchronization, ERD) during cognitive problem solving; in most of these aspects also sex differences were studied. To highlight only a few main findings from these studies: Almost all studies displayed considerable sex differences in the relationship between intelligence and cortical activation. Repeatedly it could be shown that the neural efficiency phenomenon seems to be a "male" one: While brighter males usually displayed less cortical activation than less bright ones, for females the differences in brain activation are much less clear-cut and emerge only under certain conditions like verbal tasks. This does not mean that males are more neurally efficient or more intelligent, rather it seems that the physiological mechanism of intelligence seems to be different in females. It has yet to be determined which mechanisms in female brains are responsible for individual differences in intelligence. Other important findings have been obtained on neural mechanisms of learning and intelligence: Confronted with a novel cognitive task brighter individuals develop more efficient brain activation patterns with learning this task, i.e. they more strongly decrease their brain resources required for problem solving. Finally it could be demonstrated that the neural efficiency phenomenon applies only to rather novel tasks; when experts in a certain field are tested on a task drawing upon their expertise domain then brain efficiency does not distinguish between more or less bright individuals: Both groups display similar cortical activation indicating that during the development of expertise in a certain field neural efficiency in expertise-related tasks might have been established. Future research will show if neural efficiency (and possibly intelligence) could be trained.