General intelligence, the "g" factor, is a major issue in psychology and neuroscience. However, the neural mechanism of the "g" factor is still not clear. It is suggested that the "g" factor should be non-modular (a property across the brain) and show good colinearity with various cognitive tests. This study examines…

Proton magnetic resonance spectroscopy ([to the first power]H-MRS) is a technique for the assay of brain neurochemistry "in vivo." N-acetylaspartate (NAA), the most prominent metabolite visible within the [to the first power]H-MRS spectrum, is found primarily within neurons. The current study was designed to further elucidate NAA-cognition…

The neural efficiency hypothesis of intelligence suggests a more efficient use of the cortex (or even the brain) in brighter as compared to less intelligent individuals. This has been shown in a series of studies employing different neurophysiological measurement methods and a broad range of different cognitive task demands. However, most of the…

Whether patients with tuberous sclerosis complex (TSC) have brain normal-appearing white matter (NAWM) damage and whether such damage contributes to their intellectual disability were examined in 15 TSC patients and 15 gender- and age-matched healthy controls using diffusion tensor imaging (DTI). Histogram and region of interest (ROI) analyses of…

With the advancement of image acquisition and analysis methods in recent decades, unique opportunities have emerged to study the neuroanatomical correlates of intelligence. Traditional approaches examining global measures have been complemented by insights from more regional analyses based on pre-defined areas. Newer state-of-the-art approaches…

Recent neuroimaging research has shown sex-related differences in the relationship between brain structure and cognitive function. Anatomical studies have shown a greater reliance for cognitive function on white matter structure in adult females, and a greater reliance on gray matter structure in adult males. Functional neuroimaging studies have…

An enduring enterprise of experimental psychology has been to account for individual differences in human performance. Recent advances in neuroimaging have permitted testing of hypotheses regarding the neural bases of individual differences but this burgeoning literature has been characterized by inconsistent results. We argue that careful design…

We suggest that an over-arching "fitness factor" (an index of general genetic quality that predicts survival and reproductive success) partially explains the observed associations between health outcomes and intelligence. As a proof of concept, we tested this idea in a sample of 3654 US Vietnam veterans aged 31-49 who completed five cognitive…

The relation between general intelligence (psychometric "g") and temporal resolution capacity of the central nervous system was examined by assessing performance on eight different temporal tasks in a sample of 100 participants. Correlational and principal component analyses suggested a unitary timing mechanism, referred to as temporal "g".…

Tested whether tonic EEG power is related to memory performance by analyzing ongoing EEG for 60 subjects in 5 experimental conditions. Subjects with good memory performance had significantly larger upper alpha power, but less theta and lower alpha power. Also discusses findings for subjects good at calculation. (SLD)

Tested whether alpha power in different sub-bands is selectively related to intelligence. For 74 Austrian subjects, the EEG was recorded during a resting session and 2 different intelligence tests were performed. Findings show a strong positive correlation between intelligence and alpha power. (SLD)

The dendritic structure of layer II-III pyramidal neurons of the parietal cortex in 41 Long-Evans rats was compared to behavioral assessments of attention to novelty, response flexibility, and reasoning. A significant correlation between dendritic arborization and behavioral performance was not demonstrated. (SLD)

Nerve conduction velocity (NCV) and efficiency of synaptic transmission are two possible biological mechanisms that may underpin intelligence. Direct assessments of NCV, without synaptic transmission, show few substantial or reliable correlations with cognitive abilities ["Intelligence" 16 (1992) 273]. We therefore assessed the latencies…

Using a simple neural model comprising between two and four neurons, it is concluded that speed of neuron conduction is not the probable basis of the intelligence quotient (IQ)-reaction time (RT) correlation. This result illustrates that neural modeling can be applied to biological theories of individual differences in intelligence. (SLD)

The relationship between mental retardation and brain size is discussed. Research suggests that a common path for many otherwise idiopathic mild retardation cases (genetic or environmental) could be small brain size, indicating reduced information processing capacity. Suggestions are made for further research on neuron number. (SLD)