Differences in the sensations of cold on the anterior torso of control and spinal-cord-transected individuals.

Application of cold stimuli to the sentient portion of the anterior torso of 12 spinal-cord-transected individuals (patients) and to comparable sites of 11 control participants showed that thresholds are lower for women than for men and that the difference between the sexes is maintained following spinal-cord transection. Patients of both sexes were more sensitive to cold stimuli than were controls. Estimates of stimulus intensity showed that participants reliably distinguished the 3 cool stimuli but that control women offered significantly larger estimates than control men. Spinal-cord transection produced an increase in the intensity of the sensations in women and a reduction in men. The changes in sensory perception that follow spinal-cord injury extend throughout the somatosensory system and involve all modalities. These changes cannot be explained as a simple release from inhibition.

Differences in the sensations of warmth on the anterior torso of normal and spinal-cord transected individuals.

The threshold to warming was measured at 10 sites on the anterior torso between the umbilicus and the clavicle of normal and spinal-cord transected individuals. In normal individuals, thresholds were higher on the thorax than on the abdomen. Men had higher and more variable thresholds than women. Magnitude estimations of supra-threshold stimuli showed that men offer verbal estimates of warmth that are about half of the size of the estimates given by women to the same stimuli. The psychometric function shows that in women, the sensation of warmth grows more rapidly than in men after starting from a higher initial value. After spinal-cord injury, thresholds for detection of warming were elevated. This effect was most noticeable within 8 cm of the anesthetic zone, but farther away, thresholds were still elevated but uniform as a function of distance, being about 30% higher than in normal individuals. After spinal-cord injury, the psychometric functions show that small stimuli elicit relatively large sensations and that these sensations grow more slowly with increasing skin temperatures than for normal individuals. Thus, for small warm stimuli spinal-cord-injured patients (both men and women) have a response similar to normal women but the slope of the psychometric function is flat, being similar to the slope observed for normal men.