1. Can tACS Modulate Taste Thresholds for the
bitter compound Phenylthiocarbamide?
Robert Milling
Supervisors: Dr. Alice Witney & Dr. Noreen Boyle
Date 29/05/15

2. Trinity College Dublin, The University of Dublin
Introduction
Aims
– To gain a greater understanding of how non-invasive
neurostimulation of the M1 can modulate sensory thresholds
– To discover if taste can be effected by non-invasive neurostimulation
Hypothesis
– Application of 20Hz tACS will influence brain oscillations in a
frequency dependant manner to modulate sensory thresholds
– Stimulation of the M1 will effect the VPMpc of the Thalamus which is
responsible for taste processing

3. Trinity College Dublin, The University of Dublin
PTC Taste Threshold
– Bitter tasting compound – approx. 75% of population
can taste it to varying degrees
– Solution 1 contained 0.0198g of PTC dissolved in 50ml
of ethanol. Solution 2 consisted of 25ml of solution 1
and 25ml of water. Solution 1 was 0.13mM and solution
10 0.25 x 10-6 M
– Solutions presented in order until a taste was
experienced & Forced choice test to confirm threshold
Transcranial Alternating Current Stimulation
– Delivered through two saline soaked electrodes
– C3 and F8 montage
– Stimulation of the primary motor cortex which extends to the
VPMpc of the thalamus
– 15 minutes of 20hz beta range stimulation at 1mA with a
current density of 0.04mA/cm2
– Active and Sham paradigms

4. Trinity College Dublin, The University of Dublin
Quantification of Fungiform Papillae
– “the second centimetre band had the highest
correlation with the total number of papillae”
(Shahbake et al., 2005).
– Image analysis and manipulation with
Photoshop CS5
– Polymerase Chain Reaction & Gel
electrophoresis
– 3 distinct genotypes:
• Heterozygous Taster +/-
• Homozygous Non-taster -/-
• Homozygous Taster +/+ (supertaster)
TAS2R38 Genotyping

5. Trinity College Dublin, The University of Dublin
Results
Changes in Taste Thresholds. Mean PTC
solution thresholds across both conditions, the
control (Sham) and active tACS (Active).
Table of Baseline Taste Threshold and Fungiform
Papillae Density for each participant. Our results
show a strong correlation between density and
threshold (r=0.510).
Gel image of participant DNA samples.
All are heterozygote tasters.