Effective Connectivity Analyses of the Plasticity of Brain Networks in Schizophrenia During Learning

Kalyyanee G. Nanaaware, Asadur Chowdury, Shahira Baajour, Dr. Jeffrey A. Stanley, Dr. Vaibhav A. Diwadkar, Department of Psychiatry and Behavioral Neurosciences, Wayne State University School of Medicine, Tolan Park Medical Building, 3901 Chrysler Service Drive, Detroit MI 48201

Learning is a process characterized by neural circuit plasticity and schizophrenia is suggested to be a disorder of network plasticity. Understanding impaired learning and network plasticity in schizophrenia patients has rarely been attempted at the macroscopic scale. We implemented a learning paradigm which induced negatively accelerated associative learning and utilized Dynamic Causal Modeling (DCM) to analyze the fMRI data. DCM estimates effective connectivity of pathways and changes in degree of modulation (indicates network plasticity) induced by the condition. We investigated the plasticity of ascending/descending pathways in the brain networks in schizophrenia. Control (HC) group was free of neurological/psychological evaluation (n=38; nine females). Patient (SCZ) group was stable (n=52; ten females). Subject ages: 18-50. The object-location association paradigm induced negatively accelerated learning through encoding, rest, and retrieval conditions. During encoding, subjects associated objects displayed on a 9x9 grid with the object’s grid location. Locations were randomly cued during retrieval; subjects recalled associated objects. We repeated eight cycles of the paradigm; observed a roughly linear rate of learning during cycles 1-4 which plateaued during cycles 5-8. Cycles 1-4 were denoted as “early” stages of each condition, cycles 5-8 as “late” stages. Two model structures were hypothesized, four conditions of early/late encoding and retrieval modulated relevant pathways. Structures included ventral/dorsal visual pathways, hippocampus, frontal regions; differing in whether descending pathways were modulated. Winning model didn’t have descending pathways modulated by the task. Results suggest network plasticity in SCZ/HC groups since encoding induced similar increases in degree of modulation of network pathways. Retrieval induced differing results, specifically in frontal-hippocampal pathways. A time by group interaction (significance 0.009) was induced by retrieval in the ascending pathway from the inferior temporal gyrus to the hippocampus, suggesting altered plasticity in patients. Retrieval induced a main effect of group in frontal pathways, indicating lower modulation of patient networks.

Additional Abstract Information

Presenter: Kalyyanee Nanaaware

Institution: Wayne State University

Type: Poster

Subject: Biology

Status: Approved

Time and Location

Session: Poster 2
Date/Time: Mon 3:00pm-4:00pm
Session Number: 2573