Activation of parallel fiber feedback by spatially diffuse stimuli reduces signal and noise correlations via independent mechanisms in a cerebellum-like structure

Correlations between the activities of neighboring neurons are observed ubiquitously across systems and species and aredynamically regulated by several factors such as the stimulus’ spatiotemporal extent as well as by the brain’s internal state.Using the electrosensory system of gymnotiform weakly electric fish, we recorded the activities of pyramidal cell pairs withinthe electrosensory lateral line lobe (ELL) under spatially localized and diffuse stimulation. We found that both signal andnoise correlations were markedly reduced (.40%) under the latter stimulation. Through a network model incorporating keyanatomical features of the ELL, we reveal how activation of diffuse parallel fiber feedback from granule cells by spatiallydiffuse stimulation can explain both the reduction in signal as well as the reduction in noise correlations seenexperimentally through independent mechanisms. [...