Signal detection and threshold measures to loud tones and radiant heat in chronic low back pain patients and cohort controls.

Eleven chronic low back pain (CLBP) and 11 age- and sex-matched control subjects were tested during two separate sessions for the perception of radiant heat and uncomfortably loud tones. Following the determination of a subject's pain threshold (PT) for radiant heat, a standard signal detection methodology was used to present 26 trials each of 4 stimulus levels. The stimuli were rated on a 9-point scale ranging from 'nothing' to 'very strong pain.' A similar procedure was used for the tone stimuli with the 9-point scale ranging from 'nothing' to 'very strongly uncomfortable.' It was found that the CLBP group had both higher heat pain and tone discomfort thresholds than the control group. For radiant heat only, the CLBP group had poorer discrimination as determined by P(I). The results are discussed within the framework of the hypervigilance and adaptation theories of pain perception.