Consciousness: A Neuroscience Perspective

Plato said we are trapped inside a cave and know the world only through the shadows it casts on the wall … The skull is our cave and mental representations the shadows (Pinker, 1997, p. 84).

The majority of consciousness research is steeped in an evolutionary perspective and a fundamental assumption of ‘mind-brain unity’. Single-cell organisms do not need brains, because they interface directly with their environment through chemo-tactic receptors. The brain evolved as an information processor, to bring the ‘outside inside’ so that the whole organism is privy to environmental stimuli. Primitive brains react reflexively. The higher vertebrate brain emerged because natural selection favours brains that respond rapidly, yet are flexible enough to adapt to changing environments.

For neuroscientists, ‘mind-brain unity’ refers to the way in which the brain encodes information as configurations of electrically activated neural networks. Network patterns function as a kind of Morse code that can represent the world. Networks are built up from individual neurons or groups of neurons (neuronal groups) by the intrinsic properties of nerve tissue. All nerve cells intrinsically generate electrical oscillations, independent of external and internal sensory input, and signal their excitement to neighbouring cells through synaptic connections (Hobson, 1994; Llinas, 1990). Because neurons have so many synaptic connections to other neurons, even small variations of firing in local neuronal groups lead to significant variations of firing within the widely distributed neural networks that underlie complex brain functions.

Because the concept of consciousness is complex, it is studied much like the fabled elephant, in which one wise man touches the ear, another the trunk and another the leg. In parallel fashion, this article breaks the subject down into the ‘what, how, where, when, why and whence’ of consciousness. Followi