Oscillatory networks

Apart from intrinsic properties of neurons, network properties are also an important source of neural oscillation. Neurons are locally connected, forming small clusters that are called neural ensembles. Certain network structures promote oscillatory activity at specific frequencies. This is determined by the type of neurons, i.e. excitatory or inhibitory neurons, time delays and the coupling function. Central pattern generators are a well-known example of neural networks that can endogenously produce rhythmic patterned outputs. Neural synchronization is the process by which the activity of two or more neurons or neural ensembles tend to oscillate with a repeating sequence of relative phase angles. Mathematically, neural ensembles can be considered weakly coupled oscillators, a type of system that readily allows for synchronized oscillatory activity.

Synchronized activity of a large number of neurons results in electromagnetic fields that can be measured outside the scalp with electroencephalography and magnetoencephalography. Using these techniques, synchronized neural activity have been observed throughout the central nervous system and during various tasks. Neural synchronization can be modulated by task constraints, such as attention, and is thought to play a role in feature binding, neuronal communication, and motor coordination.

Large-scale connections
Connections between different brain structures, for instance the thalamus and the cortex, can form loops that support oscillatory activity. Oscillations recorded from multiple cortical areas can become synchronized and form a large-scale network, whose dynamics and functional connectivity can be studied by means of spectral analysis and Granger causality measures. Coherent activity of large-scale brain activity might form dynamic links between brain areas required for the integration of distributed information.