The neural mechanisms of visual short-term memory capacity

Abstract

The amount of information that we can extract from a visual scene and maintain in visual short-term memory (VSTM) over a short period of time is severely limited. VSTM is capacity limited in terms of the rate of consolidating information into VSTM, as well as the total amount of information that can be maintained over time, but the neural correlates of these capacity-limited processes have not been determined. Using fMRI, this dissertation first isolates brain regions in parietal cortex that are sensitive to the amount of information maintained in VSTM. I then discuss the behavioral and neural implications of taxing VSTM maintenance. In the second half of this dissertation, I demonstrate how taxing VSTM consolidation can restrict our awareness of temporally proximate events. This is followed by a series of neuroimaging experiments that isolate a single brain region in occipital cortex whose activation amplitude tracks consolidation load, but which does not participate in maintenance. Finally, I present a study that isolates regions of parietal and frontal cortex sensitive to consolidation duration, and which provides neurobiological support for the role of consolidation in limiting how much information can be processed over a brief period of time. Together, the work presented herein provides insight into the neural mechanisms that may be largely responsible in limiting our conscious experience of events due to capacity limitations in VSTM.