  Visual short-term memory binding tasks are a promising early marker for
Alzheimer's disease (AD). To uncover functional deficits of AD in these tasks
it is meaningful to first study unimpaired brain function. Electroencephalogram
recordings were obtained from encoding and maintenance periods of tasks
performed by healthy young volunteers. We probe the task's transient
physiological underpinnings by contrasting shape only (Shape) and shape-colour
binding (Bind) conditions, displayed in the left and right sides of the screen,
separately. Particularly, we introduce and implement a novel technique named
Modular Dirichlet Energy (MDE) which allows robust and flexible analysis of the
functional network with unprecedented temporal precision. We find that
connectivity in the Bind condition is less integrated with the global network
than in the Shape condition in occipital and frontal modules during the
encoding period of the right screen condition. Using MDE we are able to discern
driving effects in the occipital module between 100-140ms, coinciding with the
P100 visually evoked potential, followed by a driving effect in the frontal
module between 140-180ms, suggesting that the differences found constitute an
information processing difference between these modules. This provides
temporally precise information over a heterogeneous population in promising
tasks for the detection of AD.
