Single-trial familiarity memories for objects and scenes
Our ability to remember whether we have encountered a particular object or scene before is remarkable - we can make these determinations after viewing tens of thousands of images, each only once, and we store these memories with exceptional visual detail. The neural processes that support single-exposure visual familiarity memory may be implemented in the same brain areas that support high-level visual processing, but the means by which the brain stores and signals single-exposure familiarity are poorly understood. To investigate these mechanisms, we record neural population responses in high-level visual brain areas as subjects perform single-exposure visual familiarity tasks. I will present the results of two experiments designed to evaluate the proposal that familiarity is signaled in inferotemporal cortex (IT) via response decrements with stimulus repetition, reminiscent of stimulus adaptation. In the first, we evaluated whether these putative familiarity signals could account for familiarity judgments via a systematic comparison of behavioral and neural sensitivity. In the second, we evaluated whether another modulator of IT firing rate responses, stimulus contrast, induces similar confusions in IT familiarity signals and familiarity judgments. The results of both experiments support the proposal that behaviorally-relevant familiarity signals are reflected as response reductions in IT, and they provide insights into how the brain supports this remarkable form of highly specific, single-exposure visual memory.