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The past decades have seen tremendous progress in fundamental studies on economic choice in humans. However, elucidation of the underlying neuronal processes requires invasive neurophysiological studies that are met with difficulties in humans. Monkeys as evolutionary closest relatives offer a solution. The animals display sophisticated and well-co...
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... options using a cursor driven by a left-right joystick. The two gamble options were presented 116 on a computer monitor 50 cm in front of the animal. In each option, reward magnitude (varying 117 between 0 and 0.5 ml water) and probability (varying between 0 and 1) were represented by the 118 height and width of a horizontal bar, respectively (Fig. 1A). At the beginning of each trial, a white 119 fixation cross appeared at the center of the monitor, and the cursor was displayed to facilitate 120 centering the left-right joystick. After two gamble stimuli were shown, the animal chose using the 121 joystick. Further details of the experiment can be found in our previous studies using ...
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... 126 human participants. Each participant performed 138 34.254 ± 7.2354 tests for each of the 4 lambdas (mean ± Standard Deviation). These tests were 139 selected from a previous study (Jain & Nielsen, 2020) and had similar probability distributions as 140 used for monkeys, including option A having only one reward amount delivered with p = 1.0 ( Fig. 141 1B). Specifically, the monkeys were tested with reward magnitudes of 0 ml, 0.25 ml and 0.5 ml, and 142 the human participants were tested with reward magnitudes of $0, $10 and $20. All tests were ...
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... GLMs (fitglm with normal distribution and linear link function) with human 164 data to predict monkey behavior. The GLMs predicted the probability y of choosing option B or D 165 based on three regressors, namely lambda (λ in Eq. 1), the probability p of obtaining the highest 166 outcome, and the probability p of obtaining the lowest outcome) ( fig. 1C): 167 contributed to the GLM, we also assessed the beta coefficients (slope) for the regressors of the 176 models. In order to fit the single-shot human choices, we calculated the GLM using the binomial ...
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... monkeys, we showed two stimuli on a computer monitor at 0.5 -1.0 s after appearance of a 210 central fixation cross. Subsequently, the animal chose between the two options using a joystick and 211 received the reward 1s later. As shown in Fig. 1A, each of the option stimuli contained one, two or 212 three horizontal bars whose width and height represented reward probability (p = 0 -1) and 213 magnitude (m = 0 -0.5 ml), respectively. For example, a full-width horizontal bar in the middle would 214 represent a safe option (p = 1) of a middle reward (m = 0.25 ml) (Fig. 1A right). ...
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... later. As shown in Fig. 1A, each of the option stimuli contained one, two or 212 three horizontal bars whose width and height represented reward probability (p = 0 -1) and 213 magnitude (m = 0 -0.5 ml), respectively. For example, a full-width horizontal bar in the middle would 214 represent a safe option (p = 1) of a middle reward (m = 0.25 ml) (Fig. 1A right). For humans, we 215 . CC-BY 4.0 International license perpetuity. It is made available under a preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint ...
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... test of the independence axiom (IA) employed two option sets. As shown in the example 233 stimuli (Fig. 1C) and Marschak-Machina triangle (Fig. 1D), one option set (options C and D) was 234 derived from the original option set (options A and B) according to the definition of the IA (Eq. 1). To 235 comply with the IA, the participant's preference should not change (e.g. if option A is preferred to ...
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... test of the independence axiom (IA) employed two option sets. As shown in the example 233 stimuli (Fig. 1C) and Marschak-Machina triangle (Fig. 1D), one option set (options C and D) was 234 derived from the original option set (options A and B) according to the definition of the IA (Eq. 1). To 235 comply with the IA, the participant's preference should not change (e.g. if option A is preferred to ...
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... outcome) = 1.0; red circles in Fig. 2A) and option B (three outcomes; black dots) in each 257 monkey in one daily session. The three lambda values tested (λ = 0.25, λ = 0.5, λ = 0.75) allowed 258 three comparisons against λ = 1.0 (option set AB in Fig. 1C). Then we applied the three lambda 259 values (0.25, 0.5 or 0.75) to options A and B to obtain option C (p (middle outcome) = 0.25, 0.5 or 260 0.75; p (low outcome) = 1 -p (middle outcome)) and option D (three outcomes) (Fig. 1C, D) and 261 estimated choice indifference points between option C (red circles in Fig. 2B) and option D in ...
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... three lambda values tested (λ = 0.25, λ = 0.5, λ = 0.75) allowed 258 three comparisons against λ = 1.0 (option set AB in Fig. 1C). Then we applied the three lambda 259 values (0.25, 0.5 or 0.75) to options A and B to obtain option C (p (middle outcome) = 0.25, 0.5 or 260 0.75; p (low outcome) = 1 -p (middle outcome)) and option D (three outcomes) (Fig. 1C, D) and 261 estimated choice indifference points between option C (red circles in Fig. 2B) and option D in each 262 monkey. All indifference points are shown as small red dots in Figs. 2 and S1. ...
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... 0.75) to options A and B to obtain option C (p (middle outcome) = 0.25, 0.5 or 260 0.75; p (low outcome) = 1 -p (middle outcome)) and option D (three outcomes) (Fig. 1C, D) and 261 estimated choice indifference points between option C (red circles in Fig. 2B) and option D in each 262 monkey. All indifference points are shown as small red dots in Figs. 2 and S1. ...
Citations
... The way RS was measured in the present study was unique in several ways making it useful as a novel approach, but also difficult to match with previous work on RS. The paradigm differs from typical work on preference using intertemporal choice (Bujold et al., 2022;Seak et al., 2023) by evaluating preference from 'imperative' or forced choice trials. Relative reward functioning is a part of all choice paradigms, but only behavioral tasks that provide a clear reference and compare relative and absolute reward contexts can directly gauge reward updating (Flaherty, 1996). ...
Addiction involves key impairments in reward sensitivity (RS). The current study explored impaired RS to
natural reward as a predisposing factor to addictive-like behavior. Alcohol preferring (P) rats are selectively bred
based on significantly greater ethanol consumption and preference and offer the ability to inspect differences in
subjects with a positive family history of addictive-like behavior. P rat’s RS was compared to RS in the well-used
Sprague-Dawley (SD) strain. To assess RS in a novel manner, instrumental incentive contrast, discrimination and
consumption of sucrose solution were examined. Animals performed in a free operant situation for different
sucrose concentration solutions using a block of ‘mixed’ trials with alternating outcome concentrations (e.g., 5
and 10 % sucrose) to change outcome value in a predictable manner. Animals also performed for reward in
blocks of single outcome trials (5 or 10 or 20 or 40 % sucrose daily exposure) surrounding the mixed block. RS (e.
g., reward discrimination and contrast effects between and within-sessions) was measured by changes in trials
completed, instrumental response latency and consumption. P rats expressed an altered profile of RS with a
greater tendency toward equivalent responding to different outcomes within the same session and an absence of
incentive contrast from diverse reward comparisons. In contrast, SD animals expressed within-session reward
discrimination and a subset of incentive contrast effects. These effects were moderated by food deprivation more
consistently in SD compared to P rats. P rat alterations in processing natural rewards could predispose them to
addictive-like behaviors including greater alcohol consumption and preference.