430 



DOMINICK P. PURPURA 



m m 

 1.0 



0.1 



Fig. 3. Characteristics of s.c.r.'s at different distances from stimulating electrodes 

 on suprasylvian gyrus in an 8-hr-old kitten. Upper ciiannel recordings made 

 with large electrode (0-5 mm), the center of which was placed 1 mm from 

 stimulating electrodes. Lower channel responses recorded with wire electrode 

 at sites indicated at left. Note similar characteristics of responses in (3) and 

 fall-off of early component at 4 mm in (4). Further explanation in text. Cal. 



100c/s;0-l mV. 



sylvian gyrus is 0-3 m/sec in perinatal preparations, and 0-45 m/sec in 2-3- 

 week-old kittens. In the neonatal period, distant s.c.r.'s, i.e. those recorded 

 3 mm or more from the site of stimulation (cf. Fan and Feng, 1957), are never 

 of greater magnitude than "near" responses recorded 2-3 mm away from the 

 stimulating electrodes (Fig. 4). During the second postnatal week, distant 



34 5 7 mm 



Fig. 4. Relationship between near (upper channel), and distant (lower channel) 

 responses in near-term fetal kittens. (1) Graded responses at near (1 -5 mm) and 

 distant (4 mm) sites from stimulating electrodes. Stimulus evoking small near 

 s.c.r. produces detectable distant response after 15 msec latency (propagation 

 velocity, 0-27 m/sec). (2) Characteristics of distant s.c.r.'s to strong stimuli 

 evoking maximal near s.c.r.'s. Note progressively increasing latency of distant 

 responses (mean propagation velocity, 25 m/sec). Cal. 100 c/s; 01 mV. 



