Connectivity

Connectivity is a technique that uses functional MRI (fMRI) to explore global brain function in healthy and diseased states. Connectivity is now being studied as a part of global brain function in major national and international studies. It is, therefore, timely to review its relevance to anaesthesia.

Dynamic connectivity in the brain, which transcends anatomical boundaries, links functionally related regions. Clinical manifestations in neuropsychiatric diseases such has Alzheimer's disease and schizophrenia can be explained on the basis of altered connectivity patterns in the brain. Anaesthetic agents primarily disrupt long-range networks and affect the higher order networks linked to cognition causing cognitive unbinding in the brain. Lower-order, basic sensorimotor networks are less sensitive. Normal ageing causes alterations in connectivity that affects the default mode network (DMN) and certain other networks, which in turn impair fluidic measures of brain function such as reaction time, dual task performance and executive function in elderly.

Higher mental function related networks such as the DMN, the executive control network and salience are more sensitive to anaesthesia. In geriatric patients, the DMN is impaired, which affects cognition. Hence, the combined effect of age and anaesthesia in elderly on mental function can cause significant postoperative cognitive impairment.