Biology subjects

van Geen, C.

Publications and source records attributed to van Geen, C..

3 recordsLinked to original sources

bioRxiv2024

Neural correlates of age-related changes in social decisions from episodic memory

Older adults are frequent victims of financial scams. Previous behavioral research suggests that this may be due to systematic biases in how they make decisions about whom to trust: for instance, Lempert et al. (2022) found that relative to younger adults, older adults were more likely to base decisions about whether to re-engage with someone on how generous that person looked, rather than on their memory for how they had previously behaved. Here, we aimed to identify the neural correlates of these age-dependent changes in social decision-making in order to clarify the mechanism by which they emerge. Using functional Magnetic Resonance Imaging (fMRI), we measured neural activity while a total of 86 participants - 45 younger and 41 older adults - learned about how much of a $10 endowment an individual, represented by a picture of their face, was willing to share with them in a dictator game. After this encoding phase, participants then made decisions about whom they wanted to play another round of the dictator game with. In line with previous findings, we found that older adults did not reliably prefer to re-engage with people who had proven themselves to be generous. This bias was the result of several factors: (1) older adults had worse associative memory for how much each person had shared, possibly due to an age-dependent decrease in neural activity in the medial temporal lobe (MTL) during encoding, (2) older adults had a stronger tendency to re-engage with familiar over novel faces regardless of their past behavior, and (3) while activity in value-responsive brain regions tracked with how generous a face looked across the age range, older adults were less able to inhibit the influence of these irrelevant perceptual features when it was necessary to do so. In line with this behavioral effect, younger adults showed greater activation in the inferior frontal gyrus (IFG) during choices that required suppressing irrelevant perceptual features in favor of associative memory. Taken together, our findings highlight age-dependent changes in both the ability to encode relevant information and to adaptively deploy it in service of social decisions.

neuroscience↗

bioRxiv2023

Lesions to different regions of frontal cortex have dissociable effects on voluntary persistence

Deciding how long to keep waiting for uncertain future rewards is a complex problem. Previous research has shown that choosing to stop waiting results from an evaluative process that weighs the subjective value of the awaited reward against the opportunity cost of waiting. In functional neuroimaging data, activity in ventromedial prefrontal cortex (vmPFC) tracks the dynamics of this evaluation, while activation in the dorsomedial prefrontal cortex (dmPFC) and anterior insula (AI) ramps up before a decision to quit is made. Here, we provide causal evidence of the necessity of these brain regions for successful performance in a willingness-to-wait task. 28 participants with frontal lobe lesions were tested on their ability to adaptively calibrate how long they waited for monetary rewards. We grouped the participants based on the location of their lesions, which were primarily in ventromedial, dorsomedial, or lateral parts of their prefrontal cortex (vmPFC, dmPFC, and lPFC, respectively), or in the anterior insula. We compared the performance of each subset of lesion participants to behavior in a control group without lesions (n=18). Finally, we fit a newly developed computational model to the data to glean a more mechanistic understanding of how lesions affect the cognitive processes underlying choice. We found that participants with lesions to the vmPFC waited less overall, while participants with lesions to the dmPFC and anterior insula were specifically impaired at calibrating their level of persistence to the environment. These behavioral effects were accounted for by systematic differences in parameter estimates from a computational model of task performance: while the vmPFC group showed reduced initial willingness to wait, lesions to the dmPFC/anterior insula were associated with slower learning from negative feedback. These findings corroborate the notion that failures of persistence can be driven by sophisticated cost-benefit analyses rather than lapses in self-control. They also support the functional specialization of different parts of the prefrontal cortex in service of voluntary persistence.

neuroscience↗

bioRxiv2020

Hierarchical Bayesian Models of Reinforcement Learning: Introduction and comparison to alternative methods

Reinforcement learning models have been used extensively to capture learning and decision-making processes in humans and other organisms. One essential goal of these computational models is the generalization to new sets of observations. Extracting parameters that can reliably predict out-of-sample data can be difficult, however. The use of prior distributions to regularize parameter estimates has been shown to help remedy this issue. While previous research has suggested that empirical priors estimated from a separate dataset improve predictive accuracy, this paper outlines an alternate method for the derivation of empirical priors: hierarchical Bayesian modeling. We provide a detailed introduction to this method, and show that using hierarchical models to simultaneously extract and impose empirical priors leads to better out-of-sample prediction while being more data efficient.

neuroscience↗