Power spectrum analysis of risk and non-risk choices during a decision-making task
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1
University of Milan, Italy
The rapid evaluation of response outcomes and the anticipation of future events are important for enabling humans to guide subsequent choices and to avoid negative events. The ability to make correct decisions in a complex environment needs careful weighing of risks and benefits associated with a choice. The patterns of neural correlates of positive or negative choices have been object of several studies, but further data are needed to better understand this process. In particular, the dynamics of neural activity may be proficiently captured by methodologies with a high temporal resolution such as the power spectrum analysis of the EEG. Recent researches showed the event-related theta band power responds specifically to outcome evaluation (Cohen et al., 2007). In our study, we used the same paradigm performed in previous researches able to address risk taking behavior (Knoch et al., 2006). In particular, we performed the Risk Task (Rogers et al., 1999), a gambling paradigm that provides a measure of decision-making under risk with little requirements on working memory. In each of the 100 trials, subjects were presented with six horizontally arranged boxes that could be pink or blue. The ratio of pink and blue boxes varied from trial to trial. Subjects had to pick the color of the box that hid the winning token. They were told that the token was equally likely to be hidden in any of the boxes. Therefore, for each trial, the level of risk was given by the probability of finding the winning token. Subjects were rewarded with points for picking the color of the box hiding the winning token and punished by loosing points for picking the incorrect color. The larger reward (and penalty) was always associated with choice of the high-risk prospect. Fourteen healthy volunteers took part in the study (seven women, age 18-26, mean = 23.67, SD = 2.78) after giving informed consent. They were all right-handed and with normal or corrected-to-normal visual acuity. The EEG was recorded with a 32-channel DC amplifier. An ElectroCap with Ag/AgCl electrodes were used to record EEG from active scalp sites referred to earlobe (10/20 system of electrode placement). Changes in band power were defined as the percentage of a decrease (ERD) in band power during a test interval (here 500 ms post-choice) as compared to a reference interval. Theta oscillation appears to vary in concomitance with choice outcome that is it synchronizes mainly for negative feedback with respect to positive ones. Theta was most pronounced in the right hemisphere than the left, and this effect revealed for theta could be involved in the modulation of the outcome valence. Interestingly, theta showed to be differently modulated after a risk or a non-risk choice. Risk choices evoke a higher synchronization when the choice is associated to a negative outcome. The effect was significantly higher in frontal electrodes. Enhanced synchronization of theta might draw selective attention for important stimuli and a concomitant increased motivational significance of the information to be processed (Holroyd & Coles, 2002). More generally the theta frequency band seems to be related to the function of a frontal cortical network dedicated to feedback evaluation and actions monitoring (Luu and Tucker, 2001). This network probably implies different structures such as the prefrontal cortex (both lateral and medial) and cinculate cortex (Ruchsow et al., 2002). In conclusion, our data, in line with some prior findings (Cohen et al., 2007; Shutter and Van Honk, 2005), showed that the theta modulation is involved in the activation of a complex control systems that guide behavior to avoid dangerous choices. Further data are needed to better explicate this functional network.
Conference:
10th International Conference on Cognitive Neuroscience, Bodrum, Türkiye, 1 Sep - 5 Sep, 2008.
Presentation Type:
Poster Presentation
Topic:
Decision Making and Response Selection
Citation:
Lucchiari
C and
Pravettoni
G
(2008). Power spectrum analysis of risk and non-risk choices during a decision-making task.
Conference Abstract:
10th International Conference on Cognitive Neuroscience.
doi: 10.3389/conf.neuro.09.2009.01.200
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Received:
08 Dec 2008;
Published Online:
08 Dec 2008.
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Correspondence:
Claudio Lucchiari, University of Milan, Milan, Italy, claudio.lucchiari@unimi.it