This prospective interventional study aims at recording contact heat evoked potentials (CHEPs) and cold evoked potentials (CEPs) in a healthy population sample in an aim to derive normative values which could be used to evaluate evoked potentials (EPs) of patients.

Population sample of 80 healthy volunteers between 26 and 75 years old will be recruited and will be categorized into 5 age subgroups (26-35, 36-45, 46-55, 56-65, 66-75 years old).

Upon arrival, participants will be reminded of the aims and of the content of the experiment. After informed consent (recorded in writing), healthy subjects will be screened with a baseline examination:

1. brief neurological examination
2. sensory nerve conduction study-related
3. quantitative sensory testing

If the baseline examination screening is considered normal, CEPs and CHEPs will be performed. To avoid bias, the side and order of the tests will be randomized.

All thermal stimuli for CEPs and CHEPs will be delivered delivered using a contact thermal stimulator (TCS model II.1, QST.Lab, Strasbourg, France).

Only stimuli that are safe and acceptable for the subject will be used in the study, and all experimental procedures can be interrupted at any time by the participant, with no detrimental effect.

Inclusion Criteria:

• Healthy volunteers between 26 and 75 years old having a normal baseline testing.

Exclusion Criteria:

• Age<26 and >75 years old
• Known neurological condition.
• Acute or chronic pain condition.
• Currently taking drugs that may influence the recording of evoked potentials (analgesics, psychotropic substances, antiepileptics…).
• History of neurological, or metabolic disorder.
• Inability to complete study task.
• History of chemotherapy.
• Habitual substance abuse(alcoholic beverages intake >21 units/week for males, >14 units/week for females.)
• Being a volley ball player (due to risk of modified sensibility of the volar forearm skin)
• Abnormal baseline neurological, SNC or QST testing