THE PYRAMIDAL TRACT: ITS EXCITATION AND FUNCTIONS 



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FIG. 1 1. Bulbar responses to stimulating the contralateral and 

 ipsilateral radial nerve in cat (chloralose-decamethonium 

 anesthesia). A. Upper traces (S) recorded from the surface of the 

 bulbar pyramid at level shown in B. Subsequent traces show re- 

 sponses recorded at depths I millimeters) from surface indicated 

 by numbers at left. Recording sites are reproduced in C. D. 

 Surface response to ipsilateral forefoot stimulation in another 

 preparation showing notching of negative wave. 



FIG. i:^. Etiect of cortical injury and anesthesia on pyramidal 

 responses to afferent stimulation in chloralose-anesthetized 

 cats, .i Vpper trace, response recorded by electrode 0.5 mm 

 beneath surface of bulbar pyramid following stimulus to contra- 

 lateral ulnar nerve. Lower trace, response after undercutting of 

 somatosensory areas I and II. B. Upper trace, responses re- 

 corded by electrode 0.5 mm beneath surface of bulbar pyramid 

 after stimulus to contralateral forepaw. Lower trace, response 

 after intravenous injection of sodium pentobarbital (g.6 mg 

 per kg). 



FIG. 13. Spike responses of a Betz cell in arm somatosensory area I to antidromic and orthodro- 

 mic stimulation in a cat under chloralose-decamethonium anesthesia. .-1. Upper trace, response to 

 antidromic shock (o.oi msec.) to ipsilateral bulbar pyramid. Lower trace, superimposed responses 

 to a train of antidromic pyramidal shocks recurring at 1 00 per sec. B. Upper trace, surface cortical 

 response to shock to contralateral forepaw. Lower trace, simultaneously recorded spike discharge. 

 C. Upper trace, surface cortical response to shock to ipsilateral forepaw. Lower trace, simultaneously 

 recorded spike discharge. (From Patton & Towe, unpublished observations.) 



