Abstract
The neural mechanisms that determine the capacity limits of working memory (WM) are not well understood, with traditional views identifying prefrontal circuitry as the source. Sensory encoding, however, remains an underexplored explanation for WM limits even though noise in sensory processing necessarily constrains brain functions that relay sensory inputs and mechanisms. Here we show that individual differences in internal sensory noise during visual processing predict visual WM capacity. Next, we show that the well-established WM deficits in schizophrenia can be linked to atypically high levels of visual sensory noise, providing a new explanatory framework for these deficits. Finally, we manipulated sensory noise levels in patients through transcranial direct current stimulation to the visual cortex, resulting in corresponding changes in visual WM precision. These findings show that sensory encoding fidelity may explain a significant amount of variance in WM function in both neurotypical adults and patients with schizophrenia.