| The disorganized symptoms of schizophrenia, including severely disordered thought patterns, may be indicative of a problem with the construction and maintenance of cell assemblies during sensory processing and attention. The gamma and beta frequency bands (15 to 70 Hz) are believed relevant to such processing.; This thesis addresses the results of an experimental examination of the cortical response of 15 schizophrenia patients and 15 control subjects when presented with auditory click-train stimuli in the gamma/beta frequency band during measurement using magnetoencephalography (MEG). These data reveal that control subjects show an increased 40 Hz response to both 20 and 40Hz stimulation as compared to patients, while schizophrenic subjects show a preference for 20Hz response to the same driving frequencies.; In this work, a computational model of the auditory cortex is constructed based on post-mortem studies that indicate cortical interneurons in schizophrenic subjects have decreased GAT-1 (a GABA transporter) and GAD67 (a GABA precursor). The model transitions from control to schizophrenic frequency response when an extended inhibitory decay time is introduced; this change captures a possible effect of these GABA alterations.; Computational model behavior can be understood dynamically through consideration of a single cell experiencing periodic inhibition. The cases of a cell spiking due to its intrinsic parameters and a cell spiking due to periodic excitatory input are considered. For the latter case, existence or absence of a fixed point for a discrete map taken at the input frequency underlies the behavior of the full computational model. An additional one-parameter family of discontinuous discrete maps that captures the transition to the schizophrenic response to 40Hz drive as input frequency is varied is discussed.; Modeling gamma/beta range auditory entrainment in schizophrenia provides insight into how biophysical mechanisms can impact cognitive function. In addition, the study of dynamics that underlie auditory entrainment in schizophrenia may contribute to the understanding of how gamma and beta rhythms impact cognition in general. |
