Forebrain:

The largest part of  the brain that you  see in Fig. is the cerebrum. It consists of  two halves or hemispheres  joined  together by  a band of  nerve fibres. Interestingly the crossing over of nerve fibres here causes the right half  to control the actions.of  the left side of the body and vice versa. The outer surface of  the cerebrum is  the cerebral cortex.  It is often referred to as the  'grey matter' because of  its colour. It is profusely supplied with blood vessels. The cortex was explored in a very fascinating way, particularly by a Canadian neuro- surgeon, Wilder Penfield: Since 1900's it was known that the brain cpntained no pain :ceptors and.hence  it could be operated upon, without making the person unconscious: local anesthesia, the top of  the skull could be removed  like a cap to expose the cortex. Penfield did exactly this and he stimulated different parts of the cortex, one by one, by matching  them with an electric wire or probe. He was amazed to observe the reactions of the dtients. On touching one part of  the cortex with the probe, the patients could see, hear or nell or feel! Patients could revive old memories. Some reported hearing the sound of a articular song; one woman felt as if  her daughter was in  the room talking to her; another. erson could actually recollect the smell of  flowers! Stimulation of  other regions caused notor responses such as the movement of  an arm or leg.