Publications by authors named "William H Alexander"

Signals related to uncertainty are frequently observed in regions of the cognitive control network, including anterior cingulate/medial prefrontal cortex (ACC/mPFC), dorsolateral prefrontal cortex (dlPFC), and anterior insular cortex. Uncertainty generally refers to conditions in which decision variables may assume multiple possible values and can arise at multiple points in the perception-action cycle, including sensory input, inferred states of the environment, and the consequences of actions. These sources of uncertainty are frequently correlated: noisy input can lead to unreliable estimates of the state of the environment, with consequential influences on action selection.

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Although multisensory integration (MSI) has been extensively studied, the underlying mechanisms remain a topic of ongoing debate. Here we investigate these mechanisms by comparing MSI in healthy controls to a clinical population with spinal cord injury (SCI). Deafferentation following SCI induces sensorimotor impairment, which may alter the ability to synthesize cross-modal information.

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Article Synopsis
  • The study explores the role of the prefrontal cortex (PFC) in processing both value and information during decision-making, backed by neuroeconomic and decision neuroscience evidence.
  • The research uses advanced techniques like computational modeling and functional MRI to investigate whether the PFC has distinct systems for valuing information separately from rewards.
  • Findings reveal two separate regions in the PFC that independently represent reward and information, suggesting that the PFC optimizes both signals, which may influence our understanding of its function in different populations, such as those with mental health issues.
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Background: Degeneracy-the ability of structurally different elements to perform similar functions-is a property of many biological systems. Highly degenerate systems show resilience to perturbations and damage because the system can compensate for compromised function due to reconfiguration of the underlying network dynamics. Degeneracy thus suggests how biological systems can thrive despite changes to internal and external demands.

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  • Cognitive control and decision-making involve a collaboration between the medial prefrontal cortex (mPFC) and lateral prefrontal cortex (lPFC), essential for combining and selecting multiple related pieces of information.
  • Various theories suggest these brain regions have different roles, including signaling the need for control, selecting behavioral strategies, and forming task-related plans, but none explain their continuous interaction during behavior.
  • The Hierarchical Error Representation (HER) model extends this understanding by incorporating real-time dynamics and shows how mPFC and lPFC work together before and after important events, supporting the idea of predictive coding as a key framework for studying their functions.
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Activity in the dorsal anterior cingulate cortex (dACC) is observed across a variety of contexts, and its function remains intensely debated in the field of cognitive neuroscience. While traditional views emphasize its role in inhibitory control (suppressing prepotent, incorrect actions), recent proposals suggest a more active role in motivated control (invigorating actions to obtain rewards). Lagging behind empirical findings, formal models of dACC function primarily focus on inhibitory control, highlighting surprise, choice difficulty and value of control as key computations.

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Efficient integration of environmental information is critical in goal-directed behavior. Motivational information regarding potential rewards and costs (such as required effort) affects performance and decisions whether to engage in a task. While it is generally acknowledged that costs and benefits are integrated to determine the level of effort to be exerted, how this integration occurs remains an open question.

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Multi-voxel pattern analysis often necessitates feature selection due to the high dimensional nature of neuroimaging data. In this context, feature selection techniques serve the dual purpose of potentially increasing classification accuracy and revealing sets of features that best discriminate between classes. However, feature selection techniques in current, widespread use in the literature suffer from a number of deficits, including the need for extended computational time, lack of consistency in selecting features relevant to classification, and only marginal increases in classifier accuracy.

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Article Synopsis
  • The frontal lobes are crucial for voluntary actions and pursuing goals, but their exact roles are still not fully understood.
  • Researchers propose a new model called the Hierarchical Error Representation (HER), which uses predictive coding to explain how complex behaviors can be learned and performed.
  • This model integrates various research findings and offers a fresh perspective on the functions of the prefrontal cortex, linking neural activity to broader behavioral outcomes.
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In the past two decades, reinforcement learning (RL) has become a popular framework for understanding brain function. A key component of RL models, prediction error, has been associated with neural signals throughout the brain, including subcortical nuclei, primary sensory cortices, and prefrontal cortex. Depending on the location in which activity is observed, the functional interpretation of prediction error may change: Prediction errors may reflect a discrepancy in the anticipated and actual value of reward, a signal indicating the salience or novelty of a stimulus, and many other interpretations.

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Human behavior is strongly driven by the pursuit of rewards. In daily life, however, benefits mostly come at a cost, often requiring that effort be exerted to obtain potential benefits. Medial PFC (MPFC) and dorsolateral PFC (DLPFC) are frequently implicated in the expectation of effortful control, showing increased activity as a function of predicted task difficulty.

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Article Synopsis
  • The anterior cingulate cortex (ACC) has become a key focus of brain research over the last 20 years, showing its involvement in various functions like conflict resolution, social interactions, pain perception, and self-control.
  • Many computational models have emerged to explain the ACC's functions, starting with early models that contextualized EEG and fMRI data, to newer ones emphasizing effortful control.
  • There’s an ongoing need to integrate these diverse findings into a single, comprehensive framework that can encompass the multitude of roles the ACC plays in cognitive processes.
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Sometime in the past two decades, neuroimaging and behavioral research converged on pFC as an important locus of cognitive control and decision-making, and that seems to be the last thing anyone has agreed on since. Every year sees an increase in the number of roles and functions attributed to distinct subregions within pFC, roles that may explain behavior and neural activity in one context but might fail to generalize across the many behaviors in which each region is implicated. Emblematic of this ongoing proliferation of functions is dorsal ACC (dACC).

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pFC is generally regarded as a region critical for abstract reasoning and high-level cognitive behaviors. As such, it has become the focus of intense research involving a wide variety of subdisciplines of neuroscience and employing a diverse range of methods. However, even as the amount of data on pFC has increased exponentially, it appears that progress toward understanding the general function of the region across a broad array of contexts has not kept pace.

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Recent work on the role of the ACC in cognition has focused on choice difficulty, action value, risk avoidance, conflict resolution, and the value of exerting control among other factors. A main underlying question is what are the output signals of ACC, and relatedly, what is their effect on downstream cognitive processes? Here we propose a model of how ACC influences cognitive processing in other brain regions that choose actions. The model builds on the earlier Predicted Response Outcome model and suggests that ACC learns to represent specifically the states in which the potential costs or risks of an action are high, on both short and long timescales.

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Unlabelled: Neuroimaging studies of the medial prefrontal cortex (mPFC) suggest that the dorsal anterior cingulate cortex (dACC) region is responsive to a wide variety of stimuli and psychological states, such as pain, cognitive control, and prediction error (PE). In contrast, a recent meta-analysis argues that the dACC is selective for pain, whereas the supplementary motor area (SMA) and pre-SMA are specifically associated with higher-level cognitive processes (Lieberman and Eisenberger, 2015). To empirically test this claim, we manipulated effects of pain, conflict, and PE in a single experiment using human subjects.

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Anterior cingulate and dorsolateral prefrontal cortex (ACC and dlPFC, respectively) are core components of the cognitive control network. Activation of these regions is routinely observed in tasks that involve monitoring the external environment and maintaining information in order to generate appropriate responses. Despite the ubiquity of studies reporting coactivation of these two regions, a consensus on how they interact to support cognitive control has yet to emerge.

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Article Synopsis
  • The dorsal anterior cingulate cortex (ACC) is linked to cognitive control and error processing, but its role in substance dependence is not fully understood.
  • Evidence from neuroimaging studies is mixed, showing both decreased and increased ACC activity in substance-dependent individuals (SDs).
  • This study finds that SDs exhibit greater risk aversion and heightened attention to rewards compared to healthy individuals, suggesting that ACC contributes to less sensitivity to omitted rewards and greater valuation of rewards in substance dependence.
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  • A new computational model called the predicted response-outcome (PRO) model helps explain how the medial prefrontal cortex (mPFC) learns to predict outcomes from actions, based on existing data.
  • Recent research indicates that the mPFC can also signal predictions and errors regardless of whether the outcomes depend on previous actions.
  • The generalized PRO model demonstrates a broader understanding of mPFC functions, connecting it to concepts like reinforcement learning and cognitive control through various experimental data.
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A number of theories have been proposed to account for the role of anterior cingulate cortex (ACC) and the broader medial prefrontal cortex (mPFC) in cognition. The recent Prediction of Response Outcome (PRO) computational model casts the mPFC in part as performing two theoretically distinct functions: learning to predict the various possible outcomes of actions, and then evaluating those predictions against the actual outcomes. Simulations have shown that this new model can account for an unprecedented range of known mPFC effects, but the central theory of distinct prediction and evaluation mechanisms within ACC remains untested.

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Humans are known to discount future rewards hyperbolically in time. Nevertheless, a formal recursive model of hyperbolic discounting has been elusive until recently, with the introduction of the hyperbolically discounted temporal difference (HDTD) model. Prior to that, models of learning (especially reinforcement learning) have relied on exponential discounting, which generally provides poorer fits to behavioral data.

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Article Synopsis
  • The medial prefrontal cortex (mPFC) and anterior cingulate cortex play key roles in higher cognitive functions and various clinical disorders, but their exact functions are still debated.
  • Various theories surrounding mPFC have looked at factors like errors, conflicts, and rewards with no single explanation fitting all findings.
  • The authors present a new model based on learning principles that can simulate diverse effects seen in mPFC, suggesting it functions to learn and predict the outcomes of actions, framing cognitive control as evaluating possible and actual results of behaviors.
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The medial prefrontal cortex (mPFC) has been the subject of intense interest as a locus of cognitive control. Several computational models have been proposed to account for a range of effects, including error detection, conflict monitoring, error likelihood prediction, and numerous other effects observed with single-unit neurophysiology, fMRI, and lesion studies. Here, we review the state of computational models of cognitive control and offer a new theoretical synthesis of the mPFC as signaling response–outcome predictions.

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Objective: This study represents the first program evaluation of the impact of a Psychosocial Rehabilitation (PSR) fellowship program within the Veterans Health Administration (VHA). Specifically, it examines the recovery orientation of five mental health rehabilitation programs at the Edith Nourse Rogers Memorial VA Medical Center (ENRM VAMC) in Bedford, MA by comparing program stakeholder rating of the "recovery orientation" between the initial data and the four-year follow-up during which the PSR fellowship was in operation. The goal of this fellowship program is to increase the VHA's fidelity to recovery-oriented best practice recommendations.

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Hyperbolic discounting of future outcomes is widely observed to underlie choice behavior in animals. Additionally, recent studies (Kobayashi & Schultz, 2008) have reported that hyperbolic discounting is observed even in neural systems underlying choice. However, the most prevalent models of temporal discounting, such as temporal difference learning, assume that future outcomes are discounted exponentially.

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