Divided visual field paradigm

The Divided Visual Field Paradigm is an experimental technique that involves measuring task performance when visual stimuli are presented on the left or right visual hemifields. If a visual stimulus appears in the left visual field (LVF), the visual information is initially projected to the right cerebral hemisphere (RH), and conversely, if a visual stimulus appears in the right visual field (RVF), the visual information is initially received by the left cerebral hemisphere (LH). In this way, if a cerebral hemisphere has functional advantages with some aspect of a particular task, an experimenter might observe improvements in task performance when the visual information is presented on the contralateral visual field. These methods have their limitations. A critical assumption has been that differences in performance with lateralized stimuli nearly always reflect functional differences between the two hemispheres. This is an extremely strong assumption. Researchers have tended to ignore or downplay the fact that asymmetries in brain function cannot be directly observed with these methods. It would require a leap of faith to assume that there is a straightforward mapping between lateralizing a stimulus and producing disproportionate activation throughout the contralateral hemisphere. Normal subjects have an intact corpus callosum, which provides for the rapid transfer of information from one hemisphere to the other. The Divided Visual Field Paradigm is an experimental technique that involves measuring task performance when visual stimuli are presented on the left or right visual hemifields. If a visual stimulus appears in the left visual field (LVF), the visual information is initially projected to the right cerebral hemisphere (RH), and conversely, if a visual stimulus appears in the right visual field (RVF), the visual information is initially received by the left cerebral hemisphere (LH). In this way, if a cerebral hemisphere has functional advantages with some aspect of a particular task, an experimenter might observe improvements in task performance when the visual information is presented on the contralateral visual field. The divided visual field paradigm capitalizes on the lateralization of the visual system. Each cerebral hemisphere only receives information from one half of the visual field—specifically, from the contralateral hemifield. For example, retinal projections from ganglion cells in the left eye that receive information from the left visual field cross to the right hemisphere at the optic chiasm; while information from the right visual field received by the left eye will not cross at the optic chiasm, and will remain on the left hemisphere. Stimuli presented on the right visual field (RVF) will ultimately be processed first by the left hemisphere's (LH) occipital cortex, while stimuli presented of the left visual field (LVF) will be processed first by the right hemisphere's (RH) occipital cortex.Because lateralized visual information is initially segregated between the two cerebral hemispheres, any differences in task performance (e.g., improved response time) between LVF/RVF conditions might be interpreted as differences in the RH or LH's ability to perform the task.