Impulsivity is a profound source of poor decision making, often bringing suffering to both person... more Impulsivity is a profound source of poor decision making, often bringing suffering to both person and polity. Although impulsivity attends psychiatric disorders such as addiction, pathological gambling, attention deficit hyperactivity disorder, and obsessive-compulsive disorder, almost everyone makes impulsive decisions that disregard the long-term consequences of our actions in favor of the near-term allure of immediate temptations. Deliberating between long-term benefits and short-term rewards is also a hallmark of foraging decisions, probably the most fundamental of all challenges confronted by mobile organisms. Behavioral studies confirm theoretical predictions that foragers compute the value of current offers, track background reward rates over different temporal and spatial scales, and update strategies in response to changes in the environment. These observations suggest that the execution of foraging computations is fundamental for understanding the organization of the nervous system. Here we describe a process model for making foraging choices that integrates the value of short-term options and compares that value to a decision threshold determined by long-term reward rates. In addition, the role of interrupts and optimization routines are here incorporated for the first time into a foraging framework, by adapting decision thresholds to changes in the environment. A core network of brain areas, including the ventromedial prefrontal cortex, the anterior cingulate cortex, and the posterior cingulate cortex, under the modulatory influence of dopamine and norepinephrine, executes these computations and implements these processes. Our model provocatively implies that maladaptive impulsive choices can result from dysregulated foraging neurocircuitry.
Psychophysical techniques typically assume straightforward relationships between manipulations of... more Psychophysical techniques typically assume straightforward relationships between manipulations of real-world events, their effects on the brain, and behavioral reports of those effects. However, these relationships can be influenced by many complex, strategic factors that contribute to task performance. Here we discuss several of these factors that share two key features. First, they involve subjects making flexible use of time to process information. Second, this flexibility can reflect the rational regulation of information-processing trade-offs that can play prominent roles in particular temporal epochs: sensitivity to stability versus change for past information, speed versus accuracy for current information, and exploitation versus exploration for future goals. Understanding how subjects manage these trade-offs can be used to help design and interpret psychophysical studies.
Executive dysfunctions, psychopathologies arising from problems in the control and regulation of ... more Executive dysfunctions, psychopathologies arising from problems in the control and regulation of behavior, can occur as a result of the faulty execution of formal information processing models or as a result of malfunctioning neural mechanisms. The models correspond to the formal descriptions of how signals in the environment must be transformed in order to behave adaptively, and the mechanisms correspond to the signal transformations that nervous systems implement in order to execute those cognitive functions. Mechanisms in the form of repeated patterns of neural dynamics execute information processing models. Two distinct modes of malfunction can occur when neural dynamics execute models of information processing. The processing models describing behavior may fail to be executed correctly by neural mechanisms. Or, the neural mechanisms may malfunction, failing to implement the right computation. As an example of malfunctioning models in executive cognition, purported failures of rule following can be understood as failures to appropriately execute a suite of processing models. As an example of malfunctioning mechanisms of executive cognition, maladaptive behavior resulting from dysfunction in the medial prefrontal cortex (mPFC) can be understood as failures in the signal transformations carried out therein. The purpose of these examples is to illustrate the potential benefits of considering models and mechanisms in the diagnosis and etiology of neuropsychological illness and dysfunction, especially disorders of executive cognition.
Many psychiatric conditions present complex behavioral symptoms, and the type and magnitude of un... more Many psychiatric conditions present complex behavioral symptoms, and the type and magnitude of underlying neural dysfunction may vary drastically. This review introduces a classification scheme for psychiatric symptoms, describing them in terms of the state of a dysfunctional neural circuit. We provide examples of two kinds of functional deficits: variance-shifted functionality, in which a damaged circuit continues to function albeit suboptimally, and state-shifted functionality, resulting in an absent or qualitatively different functional state. We discuss, from the perspective of neuroeconomics and related areas of behavioral investigation, three broad classes of commonly occurring symptoms in psychopathology based on selected studies of decision making in animals: temporal discounting, social preferences, and decision making under environmental volatility. We conclude that the proposed mechanistic categorization scheme offers promise for understanding neural circuit dysfunctions underlying psychopathology.
When has the world changed enough to warrant a new approach? The answer depends on current needs,... more When has the world changed enough to warrant a new approach? The answer depends on current needs, behavioral flexibility and prior knowledge about the environment. Formal approaches solve the problem by integrating the recent history of rewards, errors, uncertainty and context via Bayesian inference to detect changes in the world and alter behavioral policy. Neuronal activity in posterior cingulate cortexa key node in the default networkis known to vary with learning, memory, reward and task engagement. We propose that these modulations reflect the underlying process of change detection and motivate subsequent shifts in behavior.
Impulsivity is a profound source of poor decision making, often bringing suffering to both person... more Impulsivity is a profound source of poor decision making, often bringing suffering to both person and polity. Although impulsivity attends psychiatric disorders such as addiction, pathological gambling, attention deficit hyperactivity disorder, and obsessive-compulsive disorder, almost everyone makes impulsive decisions that disregard the long-term consequences of our actions in favor of the near-term allure of immediate temptations. Deliberating between long-term benefits and short-term rewards is also a hallmark of foraging decisions, probably the most fundamental of all challenges confronted by mobile organisms. Behavioral studies confirm theoretical predictions that foragers compute the value of current offers, track background reward rates over different temporal and spatial scales, and update strategies in response to changes in the environment. These observations suggest that the execution of foraging computations is fundamental for understanding the organization of the nervous system. Here we describe a process model for making foraging choices that integrates the value of short-term options and compares that value to a decision threshold determined by long-term reward rates. In addition, the role of interrupts and optimization routines are here incorporated for the first time into a foraging framework, by adapting decision thresholds to changes in the environment. A core network of brain areas, including the ventromedial prefrontal cortex, the anterior cingulate cortex, and the posterior cingulate cortex, under the modulatory influence of dopamine and norepinephrine, executes these computations and implements these processes. Our model provocatively implies that maladaptive impulsive choices can result from dysregulated foraging neurocircuitry.
Psychophysical techniques typically assume straightforward relationships between manipulations of... more Psychophysical techniques typically assume straightforward relationships between manipulations of real-world events, their effects on the brain, and behavioral reports of those effects. However, these relationships can be influenced by many complex, strategic factors that contribute to task performance. Here we discuss several of these factors that share two key features. First, they involve subjects making flexible use of time to process information. Second, this flexibility can reflect the rational regulation of information-processing trade-offs that can play prominent roles in particular temporal epochs: sensitivity to stability versus change for past information, speed versus accuracy for current information, and exploitation versus exploration for future goals. Understanding how subjects manage these trade-offs can be used to help design and interpret psychophysical studies.
Executive dysfunctions, psychopathologies arising from problems in the control and regulation of ... more Executive dysfunctions, psychopathologies arising from problems in the control and regulation of behavior, can occur as a result of the faulty execution of formal information processing models or as a result of malfunctioning neural mechanisms. The models correspond to the formal descriptions of how signals in the environment must be transformed in order to behave adaptively, and the mechanisms correspond to the signal transformations that nervous systems implement in order to execute those cognitive functions. Mechanisms in the form of repeated patterns of neural dynamics execute information processing models. Two distinct modes of malfunction can occur when neural dynamics execute models of information processing. The processing models describing behavior may fail to be executed correctly by neural mechanisms. Or, the neural mechanisms may malfunction, failing to implement the right computation. As an example of malfunctioning models in executive cognition, purported failures of rule following can be understood as failures to appropriately execute a suite of processing models. As an example of malfunctioning mechanisms of executive cognition, maladaptive behavior resulting from dysfunction in the medial prefrontal cortex (mPFC) can be understood as failures in the signal transformations carried out therein. The purpose of these examples is to illustrate the potential benefits of considering models and mechanisms in the diagnosis and etiology of neuropsychological illness and dysfunction, especially disorders of executive cognition.
Many psychiatric conditions present complex behavioral symptoms, and the type and magnitude of un... more Many psychiatric conditions present complex behavioral symptoms, and the type and magnitude of underlying neural dysfunction may vary drastically. This review introduces a classification scheme for psychiatric symptoms, describing them in terms of the state of a dysfunctional neural circuit. We provide examples of two kinds of functional deficits: variance-shifted functionality, in which a damaged circuit continues to function albeit suboptimally, and state-shifted functionality, resulting in an absent or qualitatively different functional state. We discuss, from the perspective of neuroeconomics and related areas of behavioral investigation, three broad classes of commonly occurring symptoms in psychopathology based on selected studies of decision making in animals: temporal discounting, social preferences, and decision making under environmental volatility. We conclude that the proposed mechanistic categorization scheme offers promise for understanding neural circuit dysfunctions underlying psychopathology.
When has the world changed enough to warrant a new approach? The answer depends on current needs,... more When has the world changed enough to warrant a new approach? The answer depends on current needs, behavioral flexibility and prior knowledge about the environment. Formal approaches solve the problem by integrating the recent history of rewards, errors, uncertainty and context via Bayesian inference to detect changes in the world and alter behavioral policy. Neuronal activity in posterior cingulate cortexa key node in the default networkis known to vary with learning, memory, reward and task engagement. We propose that these modulations reflect the underlying process of change detection and motivate subsequent shifts in behavior.
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Papers by David Barack