Information Storage in Nerve Cells 



219 



2-4, 





7-M 



Fig. 22. Failure of epileptiform after-discharge to invade non-epileptic neuronally 

 isolated region. Unanesthetized rabbit. Implanted electrodes at sites indicated 

 on diagram. Channel designations refer to the correspondingly numbered elec- 

 trodes and denote grid 1 and grid 2 respectively. Electrical stimulus had been 

 applied to cortical surface at site of electrode 4. The electrode wiUiin the isolated 

 region (7) is connected to a reference (M) sewed into the cervical muscles. 

 Calibration: 50 microvolts and one second. 



Normol corlex (1-21 



Normol cortex (2-3) ^ 



Isolated cortex (4-M) 







Normol cortex 





Microelectrode 



Fig. 23. Propagation of epileptiform discharge into an isolated epileptic region. 

 Two examples with both surface and simultaneous microelectrode recording. 

 A pledget of filter-paper soaked in Metrazol was placed on normal cortex out- 

 side the isolated slab at 2 cm. distance. The electrographic discharge so induced 

 spread slowly across the cortex and after some delay invaded the isolated zone. 

 Single units within the slab were recorded through tungsten microwires having 

 a tip resistance of 10-40 megohms. Calibration: 50 microvolts and one second 

 for the ink-writer tracings and one second for the cathode ray oscilloscope (39). 



