Comparing effective and functional connectivity

Information processing in the brain is thought to result from the coordination of large-scale neuronal activity. However, this activity occurs within fine neural circuits. In this study, we investigate the relationship between neuronal wiring and coherent activity. First, we estimate monosynaptic connectivity by applying an advanced analysis method to spike trains recorded with high-density microelectrodes and confirm that the estimated effective connectivity is broadly in line with neuroanatomical and neurophysiological evidence. Second, we estimate functional connectivity or the temporal correlation of calcium imaging signal between the same set of neurons, and confirm that the estimated functional connectivity is susceptible to influence of shared inputs and population synchronization on slower timescales. Notably, even with unrealistically fast time scale, the functional connectivity defined as the synchronous correlation, is only partially consistent with the effective connectivity estimated using advanced analytical techniques that pursue monosynaptic connections. These findings suggest the complementary roles for effective and functional connectivity: the former provides circuit-level specificity, while the latter reflects emergent system-wide patterns of activity. We propose that an integrative approach combining both perspectives is essential for understanding circuit-level computation in the brain.