Page No 211-219
Dhaka, S. & Kashyap, N.
The Maharaja Sayajirao University of Baroda, Vadodara
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In intertemporal choice (ITC), people discount future rewards in proportion to the time
delay until reward is received. Imaging studies showed frontal cortex activation during
delay discounting task (Ballard & Knutson, 2009). A repetitive low frequency TMS in
the left DLPFC showed increased choices of immediate rewards over larger delayed
gains, compared to the sham stimulation (Figner et. al., 2010). Given the extensive
involvement of prefrontal region in intertemporal choices, this study aimed to investigate
whether modulating prefrontal activity with tDCS has any effect on reward choice in
delay discounting tasks. 30 healthy participants (mean age: 22.5 years) participated
in this study. On each experimental day active tDCS and sham tDCS (separated by at
least one week) was applied on each participant when performing delay discounting
task to identify indifference point (Mazur, 1987; Green & Myerson, 2004). The results
show that independent-samples t-test was conducted to compare delay discounting
rate (K) for tDCS and sham conditions. There was a significant difference in the scores
for tDCS (M= .026, SD= .01) and sham (M= .073, SD= .06) conditions; t (29) = 2.137,
p= 0.04 which indicate that the anodal stimulation over left DLPFC decrease temporal
delay discounting. Participants preferred more choices of larger delay reward, instead of
smaller immediate option, when the left DLPFC was stimulated compared to the sham
stimulation. These observations indicate the significant role of the left prefrontal cortex
in intertemporal choice and demonstrate that increased left DLPFC activation can alter
decision making by intensifying a tendency to choose delayed gains.
t.