442 DOMINICK P. PURPURA 



synapses rather than the development of inhibitory synaptic activity must also 

 be considered. 



It should be emphasized that the actions of a»-amino acids described here 

 are apart from those exerted on the background spontaneous electro-cortical 

 activity and the long-duration positive-negative potentials which follow in 

 the wake of the evoked superficial negativity. Indeed, the finding that slow 

 "convulsant-like" electrocortical activity may be observed in Ce- or Cg- 

 treated cortex of neonatal animals at a time when all components of the 

 s.c.r. are depressed, serves to focus on complexities of the functional organi- 

 zation of immature cortex that are not apparent from analyses of activity 

 confined to superficial elements. In this connection, it should be noted that 

 despite the relative absence of inhibitory p.s.p.'s in s.c.r. 's evoked in neonatal 

 cat cortex (as indicated by the inertness of Ce and Cg), inhibitory activities 

 may be generated in neocortex of the new-born cat by corticipetal pathways 

 distributing in a more complex fashion to different synaptic organizations. In 

 the example illustrated in Fig. 15, surface responses similar to those described 

 by Scherrer and Oeconomos (1955) were evoked by weak and strong stimu- 



li 





5 ^ 



15 16 



^A__ -y^-\ 



17 18 



Fig. 15. Effects of topical GABA and strychnine on '"primary" response evoked 

 in posterior sigmoid gyrus following lateral thalamic stimulation (stimulus 

 frequency 0-5/sec); 2-day-old kitten. (1) Weak and (2), strong stimulation; 

 (3) and (4) stimulus as in (1) and (2) after topical GABA; (5) and (6) superposed 

 tracing of control response as in (1) and (2) and responses after GABA as in (3) 

 and (4); (7) and (8) early stages of recovery from GABA-effect; (9) and (10) full 

 recovery; (11)-(14) genesis of changes induced by topical strychnine (0-1%) in 

 response to strong stimulation; (15) and (16) immediate effect of GABA applied 

 to strychninized cortex, weak and strong stimulation as in (3) and (4); (17) and 

 (18) recovery from GABA effects and reappearance of strychnine action. Further 

 explanation in text. Sweep duration 150 msec in all records. 



