148 Inside the Living Cell 



aware of, is thus a subjective phenomena which cannot be measured 

 by scientific instruments in the same way as a nerve impulse. For 

 this reason many scientists think that the subjective aspect of sensa- 

 tions should not be considered in attempting a scientific account of 

 the brain. 



I think, however, that such subjective feelings and 'sensations' 

 are a legitimate study of science. While it is true that we are only 

 directly aware of our own sensations, yet we do not doubt that other 

 people have similar ones, as their behaviour only makes sense if we 

 assume, for example, that they see and hear and feel substantially 

 what we see and hear and feel ourselves. So it will be necessary to 

 bring sensations into the scientific picture somehow, although at 

 present we have practically no idea as to how it can be done. There 

 is very little doubt that the 'sensation' is connected with what goes on 

 in the nerve fibres because, as Dr Penfield has shown, the electrical 

 stimulation of exposed parts of the brain causes sensations, e.g. 

 coloured lights and feelings, like a tingling in the extremities and so 

 on. In fact it is to some extent possible to locate the cells which are 

 concerned with vision or feeling by experiments of this kind; but the 

 fact that stimulating a particular group of cells with electric currents 

 produces a sensation of green does not prove that the sensation 

 actually arises there. It may well be that the pattern of excitation 

 which is started in these cells spreads to other parts of the brain. 



In recent years some remarkable discoveries about this memory 

 record have also been made by Dr Penfield. In the course of operations 

 on the exposed brain, which are performed on epileptic patients with 

 the object of discovering and eradicating the region in which the 

 epileptic seizure originates, the cortex is stimulated electrically by 

 means of electrodes placed at different points. The operation is per- 

 formed without anaesthesia and the patient is able to describe his 

 experiences. In some cases the effect of stimulation was to cause 

 memories of long-forgotten events to return into the consciousness. 

 For example, Dr Penfield states^ that M.M. heard *a mother calling 

 her little boy' when point 1 1 on the first temporal convolution was 

 stimulated. When it was repeated at once, she heard the same thing. 

 When repeated twice at the same point, she heard it each time, and 

 she recognized she was near her childhood home. 



At point 12 nearby, on the same convolution, stimulation caused 

 her to hear a man's voice and a woman's voice 'down the river some- 

 where' and she saw the river. It was at a place 'I was visiting', she said, 

 'when I was a child'. 



Three minutes later, while the electrode was held in place 13, she 



1 Proc. Nat. Acad. Sciences (U.S.), 44, 59 (1958). 



