SOME THALAMIC AND CORTICAL MECHANISMS OF TASTE 317 



only one dot per sweep and each dot, therefore, measures a single interval. 



At the beginning of the stimulus this unit fires fairly regularly with a short 

 interspike interval averaging about 50 msec in length which corresponds to 

 a frequency of about 20 impulses/sec. As the stimulus continues the 

 average interval between spikes increases and also becomes more variable 

 as shown by the increased scattering of the dots. 



At the right is an example of a unit which is inhibited by stimulation. 

 It has a fairly regular spontaneous discharge which is completely inhibited 

 during the first few seconds of stimulation. After about 10 or 15 sec of 

 continuous stimulation, the average interval returns to normal but the 

 regularity of firing is affected to the end of the stimulation period. 



Clearly, these interspike interval dot patterns have at least two important 

 advantages. First, they present all the data in a perceptually convenient 

 and meaningful form and secondly, they construct themselves automatically 

 without tedious human labor. 



After this lengthy introduction, examples of the two types of temperature 

 units are finally presented in Fig. 7. At the top is a dot representation of 



62-325-9 TEMP. & MECH 



46''C I 43 

 37. $"0 



lO'C 



62-330-7 TEMP. 



■t^'-tu^s \: ■ ^^ym^'::^ ^^:t^: 



47°C 1 43 /4a 

 37.5°C ^.tc. 



r^:,.-,;.. V.:,.:; >>^i<^^/^ i^::^.' 



"iS 22 20 16 13 11° r 



Fig. 7. Interspike interval dot patterns of the responses of two different kinds 



of thalamic neurons to solutions of various temperatures flowed onto the tongue 



of the squirrel monkey. 



the response of a bimodal unit. The record is continuous, representing 

 about nine minutes of stimulation allotted as follows : water at body tem- 

 perature (37. 5X) flowed onto the tongue for 15 sec, followed a test 



