Neurons are the fundamental building blocks of the brain and understanding the brain ultimately involves understanding the activity of individual neurons. In doing so, we face tremendous challenges because the brain is astronomically complex. The idea behind the spike-field approach is to exploit regularities, correlations, that exist in the activity of groups of neurons in order to tackle the enormous complexity of the brain
Understanding neuronal communication is a grand challenge in neuroscience and we have developed the spike-field approach to link activity across the brain. In brief, the approach is to use spike-field measurements as way to label neurons as participating in local and/or long-range circuits. We can then relate the firing of these neurons to the animal’s ongoing behavior to reveal inter-regional communication.
Neurons communicate with other areas by sending action potentials, or spikes, along axons that connect with other neurons across synapses. Electrodes placed in the brain pick up the action potential signals directly as spikes. The electrodes also pick up the activity of groups of neurons as the local field potential, or LFP. The LFP is predominantly generated by synaptic activity. Therefore the LFP picks up both the local activity in the vicinity of the electrode as well as the input activity on the projections from neurons in other areas. Our proposal is that communication can occur when spikes in one area are correlated with the LFP in another, so if we can identify how spikes are correlated with LFPs then we can measure the communication. LFP activity contains different signals at different frequencies. To measure communication, we process spike-field activity in different frequency bands using the spike-field coherence. We can then resolve which neurons are coordinating their activity and in which frequencies.