Correlation dimension of the human electroencephalogram corresponds with cognitive load

This study aimed at assessing the effects of cognitive activity and mental task load on the correlation dimension of the human electroencephalogram (EEG). Three experimental conditions were created: a baseline condition and two cognitive task conditions, a calculation task and a time estimation task. The calculation task was supposed to induce a higher mental load than the time estimation task, which is regarded as a less complex one. This was verified by a subjective rating scale. All conditions differed significantly in subjective estimated task load. The correlation dimension appeared to be higher in both task conditions compared to the baseline condition. A comparison of the two tasks indicated that the difference in correlation dimension between calculation and time estimation was also significant, with the highest value for calculation. It is concluded that cognitive and mental activity is associated with a higher correlation dimension in the EEG. This implies that the correlation dimension is a sensitive parameter in the analysis of electrical brain activity.