Hypotheses of intelligence and the mental rotation task: correlations between parietal and frontal cortex activation and intelligence scores
Keywords: Visuospatial ability. Mental rotation. Electroencephalography.
The hypothesis of neural efficiency suggests a more efficient use of the cortex in intelligent subjects performing cognitive tasks. This hypothesis is supported by electroencephalographic data, which shows higher event-related spectral perturbation of alpha band (alpha ERSP) in individuals with higher intelligence scores, reflecting alpha synchronization and lower cortical activation. However, the inhibition-timing hypothesis suggests that high or low amplitudes of ERSP could occur simultaneously in different or in the same cortical areas, in accordance with the task demand and complexity. The main objective of the present study was to identify correlations between alpha ERSP, intelligence quotient scores and behavioral data from adolescents with high intellectual abilities and with average intelligence during the mental rotation task. All procedures were approved by the Research Ethics Committee of UFRN. Volunteers recruited into the high abilities group (N = 15) were adolescents (13-21 years) with a total intelligence quotient (IQ) score equal to or above 129. The control group (N = 15) was age-matched and had a total IQ score between 80 and 128. Participants in both groups performed the classic Shepard-Metzler’s mental rotation task, while having their electroencephalogram recorded. A multiple linear regression was performed to analyze whether the alpha ERSP recorded by the parietal and frontal electrodes was predicted by the total IQ scores, its subscores and the behavioral data. Our results show that response accuracy has an inverse correlation with alpha ERSP, and that there is also an inverse correlation between alpha ERSP with total IQ and working memory scores. We observed that the lesser the alpha ERSP value over the parietal cortex, the greater the total IQ, working memory score and accuracy. Working memory scores also predict alpha ERSP values over parietal cortex. These correlations are not observed during the pretest interval before stimuli presentation. Considering that accuracy and Wechsler’s intelligence scale scores are negatively correlated with alpha ERSP during the mental rotation task, reflecting lesser synchronization and greater cortical activation in individuals presenting higher intelligence scores, our data support the timing-inhibition hypothesis.