Information transmission by stimulus-dependent modulation of noise correlation.

Cortical neurons that are near one another show correlated response variability (noise correlation), which can contribute to synergistic information transmission. In this study, we investigated the relationship between the level of external stimulation and noise correlation and its effect on population coding. Six levels of electrical stimulation were delivered to a rat's hind paw and responses of several neighboring neurons were simultaneously recorded in the primary somatosensory cortex. As the intensity of stimulation increased, noise correlation decreased down to near zero and then increased again to a relatively small value. The degree of synergistic information transmission depended on the amount by which noise correlation was modulated. Our results show that noise correlation among somatosensory cortical neurons is dynamically modulated by external stimulation, which allows transmission of additional information.