FBS Colloquia No.376Dynamic Brain Network Laboratory

Neural mechanism of flexible working memory

Working memory is central to cognition, allowing one to hold items 'in mind'. However, despite its importance, working memory encoded stimuli imperfectly and degrade over time. Previous psychophysical studies suggest the accuracy of memories depends on the context. Memories are inaccurate when there is a large range of stimuli that could be remembered on any given trial. However, when the range of stimuli is smaller, memories are more accurate. This suggests working memory representations are adaptable, changing to efficiently store information in working memory for the current context. To understand the neural mechanisms that support this adaptability, we trained two monkeys to perform a working memory task that required them to remember two colored squares and, then, after a memory delay, report the color of the ‘selected’ memory. Initially, the color of each stimulus was randomly selected from the full color wheel. After a few hundred trials, the stimuli colors were drawn from one half color space (arbitrarily chosen). We simultaneously recorded from prefrontal and parietal cortex as the monkeys performed the task.Consistent with previous work, the monkeys were more accurate when colors were drawn from a smaller range of possible values (the half color space). By selecting this behavioral change, neural information in the prefrontal cortices became larger when the color range was restricted. Furthermore, the distance in neural space of the representation of selected colors was greater in restricted condition. Our results provide insight into how neural representations adapt to the context in order to improve working memory accuracy.