A system comprising: an implantable probe configured to apply a nerve modulating therapy to a target area of a subject to modulate conduction in one or more small diameter nerve axons to a greater degree than in one or more large diameter axons, wherein the target area includes the one or more small diameter nerve axons and the one or more large diameter nerve axons; a source, communicatively coupled to the implantable probe, configured to: configure the nerve modulating therapy to modulate conduction in the one or more small diameter nerve axons by: selecting a heat signal or an optogenetic modulation to provide the nerve modulating therapy, and selecting an intensity level of the heat signal or the optogenetic modulation provided by a given amount of radiant exposure to the target area that modulates conduction in ion channels on an outer surface of the one or more small diameter nerve axons while leaving ion channels on an outer surface of the one or more large diameter nerve axons unaffected, and provide the nerve modulating therapy to the implantable probe wherein the implantable probe is configured to apply the nerve modulating therapy to the target area of the subject for a time to modulate conduction in the one or more small diameter axons within the target area to a greater degree than large diameter axons within the target area, wherein the source is configured to receive an input based on a recording of a property associated with the one or more small diameter axons, and adjust the intensity level of the heat signal or the optogenetic modulation based on the input by adjusting the given radiant exposure of the target area. an implantable probe configured to apply a nerve modulating therapy to a target area of a subject to modulate conduction in one or more small diameter nerve axons to a greater degree than in one or more large diameter axons, wherein the target area includes the one or more small diameter nerve axons and the one or more large diameter nerve axons; a source, communicatively coupled to the implantable probe, configured to: configure the nerve modulating therapy to modulate conduction in the one or more small diameter nerve axons by: selecting a heat signal or an optogenetic modulation to provide the nerve modulating therapy, and selecting an intensity level of the heat signal or the optogenetic modulation provided by a given amount of radiant exposure to the target area that modulates conduction in ion channels on an outer surface of the one or more small diameter nerve axons while leaving ion channels on an outer surface of the one or more large diameter nerve axons unaffected, and provide the nerve modulating therapy to the implantable probe wherein the implantable probe is configured to apply the nerve modulating therapy to the target area of the subject for a time to modulate conduction in the one or more small diameter axons within the target area to a greater degree than large diameter axons within the target area, wherein the source is configured to receive an input based on a recording of a property associated with the one or more small diameter axons, and adjust the intensity level of the heat signal or the optogenetic modulation based on the input by adjusting the given radiant exposure of the target area. configure the nerve modulating therapy to modulate conduction in the one or more small diameter nerve axons by: selecting a heat signal or an optogenetic modulation to provide the nerve modulating therapy, and selecting an intensity level of the heat signal or the optogenetic modulation provided by a given amount of radiant exposure to the target area that modulates conduction in ion channels on an outer surface of the one or more small diameter nerve axons while leaving ion channels on an outer surface of the one or more large diameter nerve axons unaffected, and provide the nerve modulating therapy to the implantable probe wherein the implantable probe is configured to apply the nerve modulating therapy to the target area of the subject for a time to modulate conduction in the one or more small diameter axons within the target area to a greater degree than large diameter axons within the target area, wherein the source is configured to receive an input based on a recording of a property associated with the one or more small diameter axons, and adjust the intensity level of the heat signal or the optogenetic modulation based on the input by adjusting the given radiant exposure of the target area.