1. A method for treating a patient's pain, comprising: based at least in part on the value of a threshold frequency that corresponds to a refractory period for neurons of a target sensory neural population, selecting a target stimulation frequency that is above the threshold frequency; and producing a patient sensation of paresthesia by directing an electrical signal to multiple sensory neurons of the target sensory neural population at the target stimulation frequency, with individual neurons of the target sensory neural population completing corresponding individual refractory periods at different times, resulting in an asynchronous sensory neuron response to the electrical signal.