Project Summary:
The interactions between touch and temperature perception are essential for the human
experience & behavior, object recognition, thermoregulation, and avoidance of harmful stimuli.
Despite their importance, these modalities are mostly studied in isolation. Previous studies have
shown that innocuous and noxious skin temperature alters the perception of tactile stimulation,
and evidence suggests that thermo-tactile modulation may occur both peripherally and centrally.
However, it remains unclear whether innocuous and noxious thermo-tactile interactions occur
centrally or solely in the periphery. Additionally, the neural substrates that reflect thermo-tactile
interactions remain unknown in humans and non-human primates and it remains unknown
whether Primary Somatosensory (S1) neurons encode cutaneous thermal information during
these interactions. I hypothesize that innocuous and noxious thermo-tactile interactions
have a central locus of interaction and further hypothesize that S1 neurons may reflect
warm or cool temperatures via modulation of their neural firing rates to vibratory stimuli.
To address these gaps, I propose three specific aims. First, Aim 1 will determine if illusory thermal
cues modulate vibrotactile perception, where the vibration detection thresholds of human subjects
under veridical and illusory thermal cues (thermal referral illusion) will be compared. Second, Aim
2 will determine if illusory thermal pain modulates vibrotactile perception, where the vibration
detection thresholds of human subjects under veridical and illusory thermal pain (thermal grill
illusion) conditions will be compared. Third, Aim 3 will determine if S1 neural responses to
vibrations are modulated by skin temperature, where the neural firing rates of well-isolated single-
or populations of S1 neurons in NHPs will be recorded while vibration cues are delivered to the
finger pads under different thermal conditions. The findings of this study will provide the first
evidence of a central locus of innocuous and noxious thermo-tactile modulation in humans and
improve our understanding of the neural substrates that reflect thermo-tactile interactions.
Ultimately, this study has the potential to inform the development of therapies for patients with
impaired thermo-tactile perception.