Human Brain - Cognition

Cognition

Understanding the relationship between the brain and the mind is a great challenge. It is very difficult to imagine how mental entities such as thoughts and emotions could be implemented by physical entities such as neurons and synapses, or by any other type of mechanism. The difficulty was expressed by Gottfried Leibniz in an analogy known as Leibniz's Mill:

One is obliged to admit that perception and what depends upon it is inexplicable on mechanical principles, that is, by figures and motions. In imagining that there is a machine whose construction would enable it to think, to sense, and to have perception, one could conceive it enlarged while retaining the same proportions, so that one could enter into it, just like into a windmill. Supposing this, one should, when visiting within it, find only parts pushing one another, and never anything by which to explain a perception.

— Leibniz, Monadology

Incredulity about the possibility of a mechanistic explanation of thought drove René Descartes, and most of humankind along with him, to dualism: the belief that the mind exists independently of the brain. There has always, however been a strong argument in the opposite direction. There is overwhelming evidence that physical manipulations of, or damage to, the brain (for example by drugs or diseases, respectively) can affect the mind in potent and intimate ways. For example, a person suffering from Alzheimer's disease—a condition that causes physical damage to the brain—also experiences a compromised "mind". In this line of thinking, a large body of empirical evidence for a close relationship between brain activity and mind activity has led the great majority of neuroscientists to be materialists. Materialists believe that mental phenomena are ultimately reducible to physical phenomena.