What I understand after reading about it is that the consciousness of the person doing the channeling is put aside and the spirit overshadows the persons conciousness.
I'll copy paste some things from that website:
[FONT=Georgia, Times New Roman, Times, serif]Genuine trance is a strong sharing of mental and physical energies and consciousness between the medium and the spirit communicator. There is generally -- although not always -- manifested, within the medium, the following: [/FONT]
- [FONT=Georgia, Times New Roman, Times, serif]A slowing of the heart rate. [/FONT]
- [FONT=Georgia, Times New Roman, Times, serif]A slow, deep, and steady breathing pattern. [/FONT]
- [FONT=Georgia, Times New Roman, Times, serif]No rapid eye movement, or REM. [/FONT]
- [FONT=Georgia, Times New Roman, Times, serif]A lowering of body temperature. [/FONT]
- [FONT=Georgia, Times New Roman, Times, serif]A greatly reduced reaction to touch and pain. [/FONT]
- [FONT=Georgia, Times New Roman, Times, serif]Various degrees of unconsciousness. [/FONT]
[FONT=Georgia, Times New Roman, Times, serif]Furthermore, because in the trance condition the spirit communicator is speaking directly through the consciousness of the medium -- rather than the medium relating what is being mentally given to him or her -- the voice pattern, inflection, and general manner of speech differ from that normally exhibited by the medium. [/FONT]
[FONT=Georgia, Times New Roman, Times, serif]One final point needs to be mentioned: that of control. What does it mean to be controlled by spirit? First of all, it does
NOT mean that the medium is, in any way, possessed by a spirit personality. Possession -- or attachment (apparently a new and, in my opinion, disturbing buzz word) -- is extremely rare. Nor does it mean that the medium leaves his or her body and the spirit enters therein. [/FONT]
[FONT=Georgia, Times New Roman, Times, serif]Mediumistic control means a sharing of mental and physical energies between the medium and spirit communicator or operator. Control signifies a telepathic rapport between the two. How strongly
en rapport they are determines the degree of control. Control can range from inspired thought, to conscious control, to light trance, to deep trance, to very deep trance. It all depends upon the work at hand and the mental and physical energies available to the spirit communicator or operator. [/FONT]