Figure 6.

Characteristics of thermally defined subgroups of marginal zone neurons. A, At room temperature (23°C), COOL-type neurons had a greater level of spontaneous activity (10.8 ± 1.8 Hz) than the polymodal neurons (POLY) (0.6 ± 0.4 Hz) or the nociceptive-specific neurons (NS) (0.1 ± 0.1 Hz; p < 0.01). B, Double-logarithmic plot describing the stimulus–response functions of thermally tested subgroups within their temperature coding range. The abscissa represents the change in stimulus temperature from the holding temperature, and the ordinate represents the neural discharge frequency. The threshold for a response (≥1.5 spikes/s) is illustrated with a horizontal dotted line, and the threshold temperatures are indicated for each subgroup (arrows). The slope, x, of the regression line is equal to the exponent in Stevens' power law. A regression analysis was not completed for COOL and NS cells in the heating range because these subgroups responded to only two test temperatures.