Working Memory Coding of Analog Stimulus Properties in the Human Prefrontal Cortex

Building on evidence for working memory (WM) coding of vibro-tactile frequency information in monkey prefrontal cortex, recent electroencephalography studies found frequency processing in human WM to be reflected by quantitative modulations of prefrontal upper beta activity (20–30 Hz) as a function of the to-be-maintained stimulus attribute. This kind of stimulus-dependent activity has been observed across different sensory modalities, suggesting a generalized role of prefrontal beta during abstract WM processing of quantitative magnitude information. However, until now the avail-able empirical evidence for such quantitative WM representation remains critically limited to the retention of periodic stimulus fre-quencies. In the present experiment, we used retrospective cueing to examine the quantitative WM processing of stationary (intensity) and temporal (duration) attributes of a previously presented tactile stimulus. We found parametric modulations of prefrontal beta activity during cued WM processing of each type of quantitative information, in a very similar manner as had before been observed only for periodic frequency information. In particular, delayed pre-frontal beta modulations systematically reflected the magnitude of the retrospectively selected stimulus attribute and were functionally linked to successful behavioral task performance. Together, these findings converge on a generalized role of stimulus-dependent pre-frontal beta-band oscillations during abstract scaling of analog quantity information in human WM