Automated visual cognitive tasks for recording neural activity using a floor projection maze.

Neuropsychological tasks used in primates to investigate mechanisms of learning and memory are typically visually guided cognitive tasks. We have developed visual cognitive tasks for rats using the Floor Projection Maze(1,2) that are optimized for visual abilities of rats permitting stronger comparisons of experimental findings with other species. In order to investigate neural correlates of learning and memory, we have integrated electrophysiological recordings into fully automated cognitive tasks on the Floor Projection Maze(1,2). Behavioral software interfaced with an animal tracking system allows monitoring of the animal's behavior with precise control of image presentation and reward contingencies for better trained animals. Integration with an in vivo electrophysiological recording system enables examination of behavioral correlates of neural activity at selected epochs of a given cognitive task. We describe protocols for a model system that combines automated visual presentation of information to rodents and intracranial reward with electrophysiological approaches. Our model system offers a sophisticated set of tools as a framework for other cognitive tasks to better isolate and identify specific mechanisms contributing to particular cognitive processes.

Deficient visual sensitivity in schizotypal personality disorder.

Schizotypal personality disorder is a personality disorder in the schizophrenia spectrum, sharing genetic and neurobiologic characteristics with schizophrenia. Visual contrast detection, found to be abnormal in chronic schizophrenia, was investigated in schizotypal personality disorder (SPD). Since dopamine in the retina enhances visual contrast detection and SPD patients have relatively reduced dopaminergic activity in the brain compared to schizophrenia patients, it was hypothesized that SPD patients would have decreased to normal contrast sensitivity. Twenty-one subjects with DSM-IV diagnosed SPD, 18 healthy controls, and 12 subjects with a personality disorder unrelated to schizophrenia (OPD) were evaluated for contrast detection using a sinusoidal grating presented at varying temporal frequencies. Subjects also were evaluated neuropsychologically using several standardized neurocognitive tests. A significant effect of subject group was found on the contrast detection threshold (p<0.01) with a significant difference between the SPD group and the healthy control group but not between the OPD group and the healthy control group. The SPD group had higher contrast detection thresholds at all temporal frequencies tested. Correlations were found between contrast detection and performance on the Trail-Making, N-Back, and CPT tasks in SPD patients. These results, based upon a paradigm reflecting dopamine activity in the early visual system, highlight the differences as well as similarities between SPD and schizophrenia with regard to the dopamine system in schizophrenia spectrum (Siever and Davis, 2004).