Assessing Cognitive Workload Between Different Tasks - Using EEG to develop and examine a method to measure variation of cognitive workload between different levels of difficulty

Abstract

Assessing cognitive workload is an important tool, for example when evaluating different techniques for improving prostheses. Here, we have developed a method to compare how the cognitive workload differs if a prosthesis has sensory feedback or not. We have used electroencephalogram (EEG) and performed a pilot study on ten intact limb subjects. An easy and hard level were constructed by changing the weight of a force sensitive cube that were to be lifted back and forth over a barrier while counting sounds in an auditory oddball task. A third level consisted of only the oddball task. The difference in difficulty between the different levels were verified by measuring performance, and perceived effort. On a group level, these measurements all indicated that the no task condition was easiest, and the hard task condition was most demanding. Measurements of the number of lifts for different repetitions of the easy and hard conditions also showed signs of a learning effect during the performance of the easy task. The cognitive workload was measured by using the event-related potentials (ERP) technique and frequency bands. The results showed that the ERP component P3 was the only one that could indicate a significant difference between all three levels. A comprised measurement (consisting of the sum of ERP components N1, P2, P3, and LPP) and the alpha frequency bands (low-, high-, and broadband alpha) also showed a significant effect between some of the conditions.