An investigation into the effect of skin stimulation on smell function
An investigation for the modulation of Olfactory (Smell) function using Non-Invasive Transcutaneous Electrical Nerve Stimulation in healthy adult male volunteers
Yusuf Ozgur Cakmak
48 participants
Feb 7, 2017
Interventional
Conditions
Summary
It has been shown that at the olfactory bulb, where smell is processed, neurons show pathological changes at (smell) olfaction-related neuronal system. Alzheimer disease(AD) and Parkinson's disease(PD) patients show a significant loss of olfactory performance. In sum, the functional regression of the smell function contributes to numerous neurological diseases and therefore, regaining the olfactory function is crucially important for a potential treatment for AD, PD, Dementia and appetite disorders. Hypothesis: Vagal nerve fibers convey the visceral information to the olfactory bulb. Invasive Vagal Nerve Stimulation (VNS), using surgery, has been shown to decrease thresholds of the olfactory bulb neurons. This is directly associated with a lower detection threshold for the smell. It is also reported that invasive VNS increases the glucose uptake in the olfactory bulb. In a human study using invasive VNS, devices were implanted at vagal nerve sites in the neck region. Olfactory information processing was influenced and modulated with neck-implanted VNS devices. Results affirm the postulation that there is a strong correlation between VNS and olfactory bulb activity. To date, Olfactory bulb activity modulation with VNS stimulation has only been achieved using invasive VNS techniques. If VNS stimulation could be achieved using a non-invasive technique, this has the potential to be a safe and effective treatment to improve olfactory bulb function for AD, PD Dementia and Appetite disorder patients. To date, there has been no study on the non-invasive VNS effects on olfactory function. In the present trial, we will investigate the efficacy of the non-invasive VNS (pain-free, electrical stimulation of the skin) on altering the olfactory function in healthy humans. Data collection and subsequent assessment will (i) achieve clarification of the efficacy of non-invasive direct and indirect VNS to modulate olfactory function, and (ii) distinguish the two distinct frequency effects on modulation of the olfactory threshold, olfactory discrimination and olfactory memory functions in humans.
Eligibility
Inclusion Criteria4
- -39 years old male
- NZ European
- In good health, and not on any regular medication
- A non-smoker
Exclusion Criteria1
- Have a history of allergies, any neurological disorder, cardiac disease or are on regular medication
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Interventions
Transcutaneous Electrical Nerve Stimulation (TENS) will be applied under the pain threshold with CE approved home use TENS device by a researcher who is a medical doctor. Different dilutions of smell sticks (scientifically validated and medically approved) will be used to determine the smell function of the participants before and after the TENS interventions by an odour researcher. The number of the smell sticks that will be used may differ 4 to 10 because of the interindividual smell threshold differences. In all sessions, frontal cortex activation will be monitored for olfactory function responses with FDA approved near infrared monitoring device (NIRS). In each arm, there will be two streams: low(10Hz) and high frequency(80Hz) stimulation. 24 participants of each Arm will be allocated into two streams: 12 participants for low frequency stimulation stream and the other 12 participants for high frequency stimulation stream. Each stream will also have their own placebo group in which the same 12 participants will be enrolled. There is no evidence that 10 minutes of a single stimulation have prolonged effects. In addition, each session will be performed on a different day(active or placebo) so that the participants will be participating in different days for each session to eliminate the possible overlapping effects of the previous session. Each session duration will take 1 hour (baseline tests+stimulation+after stimulation tests) and each participant will be participating for a total of 2 hours in two different days(one day for active and one day for placebo session). All sessions will take place in the live human research/ultrasound room in Otago University, Department of Anatomy, Dunedin. Arm1 : TENS will be applied to ear skin(direct vagus nerve stimulation) with ear specific TENS electrode under pain threshold to 24 healthy volunteers for 10 minutes. This is a within designed study, therefore each participant will be participating both to an active and a placebo. 12 of the participants will be allocated to low frequency active stimulation stream and the other 12 of the participants will be allocated to high frequency active stimulation stream.Each stream will also have their own placebo group in which the same 12 participants will be enrolled. Arm2: TENS will be applied to wrist skin(indirect vagus nerve stimulation) with body specific TENS electrode under pain threshold to 24 healthy volunteers for 10 minutes. This is a within designed study, therefore each participant will be participating both to active and placebo groups. 12 of the participants will be allocated to low frequency active stimulation stream and the other 12 of the participants will be allocated to high frequency active stimulation stream. Each stream will also have their own placebo group in which the same 12 participants will be enrolled.
Locations(1)
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ACTRN12617000034336