214 Information Storage and Neural Control 



1-2 



3-4 

 4-5 



6-7 

 7-8 



Fig. 18. Electrographic characteristics of the independent mirror focus. Electro- 

 encephalogram of an unanesthetized rabbit taken three weeks after production 

 of an ethyl chloride lesion in the area designated by crosshatching. Discharges 

 originating in the primary lesion (electrode 2) and in the secondary region 

 (electrode 7) are unrelated in time of occurrence. Note also that there is some 

 depression of activity in electrodes just posterior to the primary lesion while 

 this is not true in electrodes posterior to the mirror focus. Calibration: 50 micro- 

 volts and one second (39). 



was subsequently ablated. We have demonstrated that the func- 

 tional characteristics of the cell network within the mirror focus 

 are more or less permanently altered and that the alteration is 

 manifested both by the spontaneous behavior of these cells and 

 by their response to stimulation (38, 39, 43). 



The sequence just described may be prevented by section of 

 the corpus callosum either before production of the primary lesion 

 or within twenty-four hours afterward. In addition, the develop- 

 ment of independent secondary discharge may also be prevented 

 if the callosal connections remain intact, but a sub-pial partial 

 isolation of the contralateral cortex is carried out within the same 

 time interval. Figure 19 illustrates such a preparation. The 

 isolation deprives the cortex of all of its subcortical connections 

 as well as those relating it to other cortical areas in the same 



