CHEMICAL CODING IN T ASTE — TE MPOR AL PATTERNS 279 



The foregoing data illustrate five characteristics of chorda tympani 

 multiunit responses to relatively high concentrations of glycine and alanine: 

 (1) Relatively long latency. (2) Slow increase in response magnitude. 

 (3) Little if any large spike, high frequency initial burst. (4) Little adapta- 

 tion after reaching peak magnitude. (5) Stereoisomer specificity. 



HjO A' 



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,5 M Glycine C 



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0.1 M NaCi E 



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Fig. 4. Oscillograph records of electrical activity in the entire chorda tympani 

 nerve of one rat following chemical stimulation of the anterior portion of the 

 tongue. A flow system and closed tongue chamber were used. A stimulus 

 onset signal was not used. The records have been aligned with the beginning 

 of the response. In each case, flow duration was approximately 8 sec. 

 Water wash always occurred after the end of the records. (A) H.^O (no obvious 

 response), (B) 0.1m NaCl, (C) 1.5 m Glycine, (D) Continuation of C, with 

 4.6 sec gap, (E) 0.1 m NaCl, (F) Continuation of E, with 4.6 sec gap, (G) 1.2 m 

 DL-alanine, (H) Continuation of G, with 4.6 sec gap. (I) 0.01 m NaCl. The 

 output of the summator preamplifier, which passes only positive pulses, was 

 displayed on a Tektronix 502 oscilloscope and photographed with a Grass C4F 

 camera. Records read from right to left. 



Responses to 0.1 m NaCl have temporal characteristics directly opposite 

 to the above pattern (characteristics one through four). This contrast 

 between the time course of responses to NaCl vs. amino acids is somewhat 

 similar to the comparison drawn by Pfaffmann (1955) between responses to 



