Behavioral/Systems/Cognitive Impaired Efficiency of Functional Networks Underlying Episodic Memory-for-Context in Schizophrenia

Memory for context and episodicmemory have been identified as primary contributors to cognitive impairments in schizophrenia. This study examined neural networks involved in episodic memory-for-context in schizophrenia using a multimodal strategy including a graph theoretical approach, combinedwith an assessment of the contribution of structural impairments to disruption in the efficiency of functional brainnetworks.Twenty-threepatientswith schizophrenia and33healthy controlsperformedanepisodicmemory-for-context task while undergoing functionalmagnetic resonance imaging scanning. Graph theory was used to characterize the small-world proper-ties of functional connections between activated regions, and a morphometric analysis was used to investigate schizophrenia-related structural deficits. Similar functional activations were identified in the two groups; however, although small-world properties were present in the topological organizationof the functional networks inboth groups, significant reductions in local, but not global, efficiency were observed in the schizophrenia group. Several key network “hub ” regions related to recollection, such as the bilateral dorsal anterior cingulate gyrus, showed reduced gray matter volume in schizophrenia patients. These findings suggest that loss of gray matter volume may contribute to local inefficiencies in the architecture of the network underlying memory-for-context in schizophrenia