The principal reason for measuring mental workload is to quantify the
cognitive cost of performing tasks to predict human performance. Unfortunately,
a method for assessing mental workload that has general applicability does not
exist yet. This research presents a novel self-supervised method for mental
workload modelling from EEG data employing Deep Learning and a continuous brain
rate, an index of cognitive activation, without requiring human declarative
knowledge. This method is a convolutional recurrent neural network trainable
with spatially preserving spectral topographic head-maps from EEG data to fit
the brain rate variable. Findings demonstrate the capacity of the convolutional
layers to learn meaningful high-level representations from EEG data since
within-subject models had a test Mean Absolute Percentage Error average of 11%.
The addition of a Long-Short Term Memory layer for handling sequences of
high-level representations was not significant, although it did improve their
accuracy. Findings point to the existence of quasi-stable blocks of learnt
high-level representations of cognitive activation because they can be induced
through convolution and seem not to be dependent on each other over time,
intuitively matching the non-stationary nature of brain responses.
Across-subject models, induced with data from an increasing number of
participants, thus containing more variability, obtained a similar accuracy to
the within-subject models. This highlights the potential generalisability of
the induced high-level representations across people, suggesting the existence
of subject-independent cognitive activation patterns. This research contributes
to the body of knowledge by providing scholars with a novel computational
method for mental workload modelling that aims to be generally applicable, does
not rely on ad-hoc human-crafted models supporting replicability and
falsifiability.

本研究提出了一种新的自我监督的深度学习方法，通过使用连续脑率指数和空间谱拓扑头图从 EEG 数据中进行神经负荷建模，该方法表现出在通常适用性方面的能力，这证明了卷积层学习有意义的高级表示的能力。