reading my thoughts

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Offline Tann San

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reading my thoughts
« on: 29/07/2004 22:49:30 »
Hi, this might sound like a really strange question but I'm being quite serious!  ok so here goes.  you know when people speak that they are using their speech centers within the brain.  well what I was wondering was that when you think about something, you know like "I'd better turn the tap off", well does that use the speech center as well?  I then went on to wonder whether it was possible to associate real speech with brain activity i.e. when you say "peaches" a certain combination of cells fire there a way to map that and so to blend that with my first question does that mean you can then read minds?  I should point out that I have absolutely no medical knowledge, this just seemed like an excellent question to ask.


Offline chris

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Re: reading my thoughts
« Reply #1 on: 30/07/2004 07:42:32 »
Hi Tann San

the answer to your question comes from various studies, mostly functional imaging (e.g. fMRI) in which subjects are given various tasks designed to probe which parts of the brain do what. So, for instance, when volunteers were shown pictures and asked to name them, the parts of the brain concerned with vision and with "expressive" speech lit up. When subjects were asked to imagine the pictures again, the same parts of the visual system became active, albeit at a slightly lower level.

This is also true when we dream.

So when you imagine saying things in your head you are still constructing the sentences using the speech area and its associated brain regions concerned with the subject of your speech.

Unfortunately, whilst we can now see which parts of the brain play a role in different cognitive functions, we cannot pinpoint precisely which cells, or groups of cells, are responsible. The problem was looked at with respect to the visual system by David Hubel and Torsten Wiesel, who got the Nobel prize for their work, about 30 years ago. Working with cats they identified a hierarchy of cells in the visual system which respond to progressively more complex visual stimuli e.g. lines at a specific orientation, lines with a sharply defined end etc. These cells were termed 'simple cells', 'complex cells' and 'hyper-complex cells' according to their selectivity for different types of stimulus.

This led to the elaboration of the "grandmother" cell theory whereby progressively more 'fussy' cells analyse the visual scene responding to more and more precise stimuli until you reach the level of a cell which responds specifically and only to you seeing your grandmother.

Obviously this is a massive over-simplification, but highlights how visual information is broken down and analysed in a parallel and modular fashion. For instance the colour aspects of the visual scene are analysed in a totally different part of the visual system to the part that processes moving objects. The results of all this parallel processing are combined and presented to our consciousness as one entity, without you ever realising that they were analysed separately. We know this happens because there have been some fairly celebrated cases of individuals who suffered brain injuries just to one part of the visual system leaving them unable to process that part of the visual world that the damaged piece of brain would have analysed. One woman was unable to see moving things. Her life existed as a series of snapshots like flipping through a photo album. In another example a man lost his colour perception. Some people lose the ability to recognise faces, but are otherwise normal.

So, yes, on the one hand we can see brains in action, but we certainly cannot read thoughts yet.

A recent article by Barry Gibb was devoted to the subject of functional imaging :


"I never forget a face, but in your case I'll make an exception"
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I never forget a face, but in your case I'll make an exception - Groucho Marx