The Nature of Conscious Experience


Meaning as Arrival

There seem to be two different ways of thinking about the way messages passing between cells in a brain might relate to consciousness of their meaning. One idea seems to be that the meaning lies in the pattern of message passing. This would be analogous to a picture or sentence being encoded in the pattern of sending of emails between cities. For example, sending of nine emails at 9 am from London to Glasgow and six at 10 am from Cardiff to Edinburgh might mean 'green apple'. This seems to be the approach of the 'strong artificial intelligence' brigade. Intuition suggests that this is not right. We usually think of meaning as being inside the message: the words in the email. These mean something to the recipient but not to anything else. The pattern of passing of emails has some different meaning, and only to email market researchers.

However, since each message in the brain is much the same - a brief electrical discharge - it may be true to say that the pattern of passing of messages must be what distinguishes one meaning from another. Otherwise each message would seem to have the same meaning. Meaning must arise from relationships between messages.

Thus, the email analogy may still be important, but in a slightly different way. If I am proposing a lunch party and email eight people and get identical 'great idea' emails back from only three then the pattern of messages received has a meaning over and above that of each one alone - a meaning relating to the potential success of the party. Part of the meaning lies in the fact that I know where each email came from. So there remains a distinction between the meaning of the pattern of emails being sent, as viewed by a market researcher who has never met my friends and the meaning of the pattern of emails received by me.

These two types of meaning differ in that the in the former the meaning is to something outside the brain, which is not directly relevant to brain function (or experience), and in the latter the meaning is to something within the brain which receives lots of messages in a particular pattern. The only thing in the brain that does that is a neuron.

The upshot seems to be that meaning to some subject in a brain has to be determined by the way the message arrives – which effectively means where it arrives. Ramachandran describes a thought experiment in which a neuron in the brain of a sighted person seeing red is connected to the brain of a blind person in such a way that they sense red. Regardless of where in the second brain the connection is made the incoming signal will mean that the first person saw red but to mean red to the second person it will have to be connected to that input site that has the job of meaning red to the second person. The subjective experience it induces must be entirely dependent on arriving at that site.

The need for ‘meaning to’ to be determined by site of arrival is relevant to the difficulties raised by trying to explain experience on the basis of a pattern of cells firing. Meanings to are not encoded in firings, but in arrivals of signals at places where they can have complex significance by dint of relating to other incoming signals.