E. GRASTYAN 257 



type dcsitrncci by Hubcl (1957) with a tip diameter ot 1-5 [X were used. For sub- 

 cortical recordings these electrodes were encased in a glass micro-pipette in order 

 to avoid damage to the needle tip. The electrodes were connected to capacity- 

 coupled amplifiers having a moderatcK' long time-constant (0.04 seconds) so that 

 some slow" components could be visualized. Attempts were made to use DC 

 recording for simultaneous observation ot steady potential states but we were 



STAGE II 



Vis. Corte.x ' #^^^^4^*^*^^ 



ucs 



cs 



Vent. Ant. -^./yiA/y ■^,' 



UCS 



cs 



Mes. Rot. • ^-^^-^.j,y.A 4^^-A,A^ - 



UCS 



cs 



Hippocampus ^ t<>>Jw *4 ii n ii i ii i i » >ii i<j wi»il>i#*ik ^ j ^ «i || i jk| ii<i< | 1 i i -l^**^ ^ 



^ UCS 



cs 



Fig. 6 

 Pattern of response during Stage II of the conditioning procedure. (See te.\t for further 



explanation.) 



usuallv unsuccesstid in resolving single units with that method. Indeed, even 

 capacity-coupled amplification did not always provide discrete resolution. 

 Nevertheless, the recording system was adequate to determine the presence or 

 absence or change in frequencv ot unit discharge at the sites sampled and, in 

 many cases, individual units were clearly identified. Most ot you are aware of the 

 tremendous technical diiliculties one faces in attempting to record simultaneously 



