Brain correlates of resting, alert, and meditation states.

Posner and colleagues do a nice review of neural correlates of establishing, maintaining, and switching brain states.  I thought I would pass on a few chunks from their article describing the alert state and the meditation state:

The three brain states are compared in Table 1.

The meditation state differs from the alert state induced by a warning signal in several crucial ways. First, the alert state can be induced by the simple instruction to expect a target, without requiring any practice, whereas the meditation state requires specific instruction and practice. Second, the alert state requires an external target, whereas the meditation state may not involve a target event. Third, the alert state involves primarily the neuromodulator NE, whereas dopamine (DA) has often been shown to be important to the meditation state. Finally, the alert state involves a reduction in ACC activity, likely in order to keep the mind clear to perceive and respond quickly to the target. The meditation state, however, shows increased ACC activity that serves to regulate mind wandering. As mentioned previously, Five days of integrative mind-body training (IBMT) increases brain activity in the ACC, insula, and striatum. One month of IBMT improves white matter connectivity between the ACC, striatum, and other regions. Based on these results and related work, we propose the insula, ACC, and stiatum (IAS) as key neural correlates of changing brain states (Figure 2).

Because of its role in attention and self-regulation, we hypothesize that the ACC is involved in maintaining a state by reducing conflict with other states; the insula serves a primary role in switching between states, and the striatum is linked to the reward experience and formation of habits needed to make maintenance easier. The insula and ACC work together to support the role of the autonomic nervous system in maintaining the meditation state.