The EEG and intelligence: An appraisal of methods and theories

In pursuit of knowledge

This article is based on the proposition that to understand the nature of knowledge, and how best to acquire it, one must look first at how the brain abstracts knowledge from the information provided by sensory receptors. The nature of this biological process of knowledge acquisition is suggested by the necessary conditions for the occurrence of learning, and from consideration of these necessary conditions in terms of what is currently known about the properties and limitations of neural systems. This entails discussion of an important distinction that must be made between "perceptual" and "associative" learning and between the neural systems required to mediate these two kinds of learning. There is also discussion of the manner in which language can overcome the limitations of neurological systems to greatly extend the scope of associative learning. This leads on to discussion of the role of active efferent language systems and temporary memory in the mediation of thinking. Consideration of the main features of the biological process of knowledge acquisition confirms, and extends to perception, Hume's famous conclusion that knowledge derives from the similarity or temporal contiguity of recurring events. New insights are also obtained concerning the biological causes of bias in the knowledge acquisition process, concerning the intellectual process of theory generation, and concerning the role of theory in the conduct of empirical research. Finally, and most importantly, it can be concluded that all knowledge is theory and hence that the ultimate goal of science is the development of better theories.

Genetics of human prefrontal function

Evolution of the prefrontal cortex was an essential precursor to civilization. During the past decade, it became increasingly obvious that human prefrontal function is under substantial genetic control. In particular, heritability studies of frontal lobe-related neuropsychological function, electrophysiology and neuroimaging have greatly improved our insight. Moreover, the first genes that are relevant for prefrontal function such as catechol-O-methyltransferase (COMT) are currently discovered. In this review, we summarize the present knowledge on the genetics of human prefrontal function. For historical reasons, we discuss the genetics of prefrontal function within the broader concept of general cognitive ability (intelligence). Special emphasis is also given to methodological concerns that need to be addressed when conducting research on the genetics of prefrontal function in humans.

Correlations between ERP parameters and intelligence: a reconsideration

The present study investigated differences in ERP parameters related to intelligence. For that purpose 74 individuals (Intelligence: M=107; S.D.=12; range 73-135), of average creativity passively listened to two tones and performed two auditory, and two visual oddball tasks while their EEG was recorded. The approximate entropy parameters, peak latencies and amplitudes were determined. The correlation coefficients indicated that in the attended conditions, the more intelligent individuals showed more regular ERP waveforms than less intelligent individuals. It was further found that less intelligent individuals showed increased P300 latencies and reduced amplitudes. The differences were explained with a more specific engagement of neural networks in more intelligent individuals.

The technical, neurological and psychological significance of 'alpha', 'delta' and 'theta' waves confounded in EEG evoked potentials: a study of peak latencies

It is suggested that lack of progress in understanding the neurological and psychological significance of EEG averaged evoked potentials (AEPs) and event related potentials (ERPs) may be due to the confounding of, 'delta', 'theta' and 'alpha' frequency responses generated by the 'brain-stem' 'limbic' and 'thalamic' cortical activating systems, respectively. This hypothesis was tested in a sample of 93 adults by recording EEG responses to auditory tones and using narrow-band filters to distinguish '4 Hz', '7 Hz', and '10 Hz' component waves in the unfiltered AEP. Bivariate and multivariate statistical analyses of peak latencies provided evidence of the distinct and unitary nature of these component waves and demonstrated their relative influence on the P1, N1 and P2 peaks of the unfiltered AEP. The results also reveal a predicted negative relationship between the 10 and 4 Hz latencies which is attributed to inhibition of the delta frequency brain-stem ascending reticular activating system (BSARAS) by the alpha frequency diffuse thalamic projection system (DTPS). Correlations of the 4 Hz latencies, with age, sex, and behavioural arousal variables confirm that the 4 Hz latencies are associated with the maintenance of behavioural arousal, an important function of the BSARAS.

The string measure of the ERP: what does it measure?

The event-related brain potential (ERP) has been investigated extensively inan effort to understand the neurophysiological bases of intelligence. Measures derived from the ERP have been used as indices of intelligence, particularly the string measure of the complexity of the ERP. However, the string measure has been criticised for being non-specific and for being dependent on ERP amplitude. These criticisms were tested by investigating relationships between ERP string measure, ERP amplitude measures, and the ERP power spectrum. It was found that the string measure was non-specific in that it indexes both low and high frequency event-related activity; the string measure is also dependent on ERP amplitude. The string measure is therefore not a valid measure of the ERP. It was concluded that the string measure should be abandoned; human intelligence cannot map in a simple way onto gross measures of scalp-recorded electrocortical activity.