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Zusammenfassung:
Short-term memory entails the encoding, maintenance and subsequent retrieval of sensory information and requires the communication between multiple brain regions mediating these processes. However, whether and how distant cortical areas cooperate during memory tasks is still an open question. In this study we investigate the neural interaction between visual area V4 and the lateral prefrontal cortex (lPF) using paired recordings of local field potentials (LFP) and single unit activity (SUA) in monkeys performing a visual short-term memory task (delayed - match to sample). During the memory period of the task we observed enhanced oscillatory phase - locking of LFPs between both areas that predominantly occurred in the theta frequency band (3-9Hz). In addition, we found that increased theta phase locking at the mesoscopic level of LFPs was associated with stronger phase locking of SUA to theta oscillations of the respective other region. We also assessed the functional significance of increased theta-phase locking by comparing oscillatory synchrony between V4 and lPF LFP-pairs and spike-LFP pairs for trials in which animals correctly identified the stimulus as opposed to when they failed to do so. We observed that the strength of the inter-cortical phase locking was higher for correct than incorrect trials and correlated well with session-to-session variations in monkeysí task performance. Our findings suggest that theta based oscillatory synchrony between V4 and lPF cortex likely provides a basis for the timely coordination of spiking output of V4 and prefrontal neurons during visual short-term memory. The observed correlation between inter-cortical phase locking and memory performance may reflect facilitated communication of visual information during visual memory.