Abstract
As we go up the visual hierarchy, receptive field size becomes larger, tuning characteristics become more complex, and the lifetime of neural responses increases. As a logical consequence, one would predict increasingly strict capacity limits, loss of visual detail, and longer representational lifetime for representations that depend on higher visual brain regions. Thus, the neural system acts as a low-pass filter limiting capacity, yet increasing lifetime at the same. In this talk, we will provide evidence that the characteristics of visual sensory memory cohere to this principle: our brief and super-capacity iconic memory depends on neural excitability in primary and secondary visual cortex, while our seconds-lasting and high-capacity fragile memory depends on neural activation in higher visual areas. In that sense, iconic memory and fragile memory are just like low-order and high-order forms of visual sensory memory. In addition, we will show that when information from sensory memory is made available for report, it replaces virtually all information that is currently stored in visual working memory, except for one item that remains untouched. Based on the fact that replaced working memory content can be pulled back for report, we argue that there are at least three fundamentally discernable levels in visual short-term memory; 1) foreground processes that form the center of mind, 2) background processes that are readily available for report, but can easily be swapped with 3) fragile, sensory memory representation that passively decay when there is no top-down amplification available.