University of Nebraska Medical Center

Research Interests

Hubs in Brain Networks:
Most networks are configured hierarchically: hub regions have greater importance in organizing or facilitating network activity than other regions. This principle of hub-centered construction has been applied to the resting-state networks of the brain, but there is little consensus in the literature about what regions are true hubs due to the variety of methods and measures used in their identification. In a collaborative investigation with Dr. Steve Petersen's lab at Wash U, we tested a novel theory of brain network structure by using neuropsychological methodology to evaluate potential hubs in the brain. Brain-injured patients with damage to two types of potential hub locations were evaluated with the hypothesis that damage to brain hubs should greatly impair cognition. Critically, patients with damage to hubs that were connected to many distinct brain systems showed gross cognitive impairment that was disproportionate to lesion size or location, while patients with damage to other potential hubs showed little cognitive change.

Relational Memory and the Hippocampus:
Relational memory describes the ability to bind together arbitrarily related bits of information rapidly and automatically, and we believe that this ability underlies our rich episodic memories among others. Studies of patients with severe amnesia have shown that injury to a relatively small brain structure, the hippocampus, is sufficient to severely impair relational memory while leaving other types of memory relatively intact. We continue to investigate the implications of hippocampal damage and dysfunction in new tests of memory and cognition.