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Nicole Calakos - One of the best experts on this subject based on the ideXlab platform.
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Striatal fast-spiking interneurons selectively modulate circuit output and are required for Habitual Behavior.
eLife, 2017Co-Authors: Justin K. O’hare, Kristen K. Ade, Henry H. Yin, Namsoo Kim, Erin Gaidis, Jeffrey M. Beck, Nicole CalakosAbstract:From biting fingernails to the daily commute, habits are sets of actions that can be completed almost without thinking and that are difficult to change or stop. Behavioral neuroscientists refer to habits as “stimulus-response” Behaviors, and know that forming a new habit requires a region deep within the brain called the dorsolateral striatum. Indeed, in this region, the outgoing neurons – which make up 95% of the cells - respond differently to incoming signals in mice that have learned habits compared to non-Habitual mice. However a question remained: what exactly was producing these differences? O’Hare et al. have now found, unexpectedly, that the answer resides not in the 95% of outgoing neurons, but rather in a rare type of cell known as the fast-spiking interneuron. This cell is connected to many others and it appears to act like a conductor, orchestrating the previously identified changes in the output neurons. These findings were made using mice that had been trained to press a lever for a sugar pellet reward. Habit was measured by how long mice kept pressing even if they had just been allowed to eat their fill of pellets and the test lever was no longer dispensing pellets. Habitual mice continue to press the lever in this circumstance, while other mice do not. O’Hare et al. found that inactivating the “conductor” cell made the output neurons respond in the opposite way to how they normally respond in Habitual mice. Further experiments showed that fast-spiking interneurons were also more easily activated in Habitual mice. To test whether this putative “conductor” cell was necessary for Habitual Behaviors, a technique known as chemogenetics was used to turn down its activity in Habitual mice. Indeed, reducing activity in the conductor cell blocked the Habitual Behavior. While some habits are a helpful and economical way to get through daily life, habits are also thought to be corrupted in a number of diseases such as neurodegenerative diseases, addictions and compulsions. Identifying this specific, yet rare, cell as a critical part of maintaining habits points out a new target to consider for therapies. Further work is needed before such treatments might become available to treat habit-related disorders; though O'Hare et al. are now taking steps in this direction by trying to work out how the fast-spiking interneuron changes its own activity when a habit is formed.
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Striatal fast-spiking interneurons drive Habitual Behavior
2017Co-Authors: Justin K. O’hare, Kristen K. Ade, Henry H. Yin, Namsoo Kim, Erin Gaidis, Jeffrey M. Beck, Nicole CalakosAbstract:Habit formation is a Behavioral adaptation that automates routine actions. Habitual Behavior correlates with broad reconfigurations of dorsolateral striatal (DLS) circuit properties that increase gain and shift pathway timing. The mechanism(s) for these circuit adaptations are unknown and could be responsible for Habitual Behavior. Here we find that a single class of interneuron, fast-spiking interneurons (FSIs), modulates all of these habit-predictive properties. Consistent with a role in habits, FSIs are more excitable in Habitual mice compared to goal-directed and acute chemogenetic inhibition of FSIs in DLS prevents the expression of Habitual lever pressing. In vivo recordings further reveal a previously unappreciated selective modulation of SPNs based on their firing patterns; FSIs inhibit most SPNs but paradoxically promote the activity of a subset displaying high fractions of gamma-frequency spiking. These results establish a microcircuit mechanism for habits and provide a new example of how interneurons mediate experience-dependent Behavior.
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Pathway-Specific Striatal Substrates for Habitual Behavior.
Neuron, 2016Co-Authors: Justin K. O’hare, Kristen K. Ade, Tatyana Sukharnikova, Stephen D. Van Hooser, Mark L. Palmeri, Henry H. Yin, Nicole CalakosAbstract:The dorsolateral striatum (DLS) is implicated in habit formation. However, the DLS circuit mechanisms underlying habit remain unclear. A key role for DLS is to transform sensorimotor cortical input into firing of output neurons that project to the mutually antagonistic direct and indirect basal ganglia pathways. Here we examine whether habit alters this input-output function. By imaging cortically evoked firing in large populations of pathway-defined striatal projection neurons (SPNs), we identify features that strongly correlate with Habitual Behavior on a subject-by-subject basis. Habitual Behavior correlated with strengthened DLS output to both pathways as well as a tendency for action-promoting direct pathway SPNs to fire before indirect pathway SPNs. In contrast, habit suppression correlated solely with a weakened direct pathway output. Surprisingly, all effects were broadly distributed in space. Together, these findings indicate that the striatum imposes broad, pathway-specific modulations of incoming activity to render learned motor Behaviors Habitual.
Ann M. Graybiel - One of the best experts on this subject based on the ideXlab platform.
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Good habits, bad habits.
Scientific American, 2014Co-Authors: Ann M. Graybiel, Kyle S. SmithAbstract:The article discusses research by the authors and others into the neurophysiological basis of habit formation, focusing on the role of brain circuits in the striatum and neocortex. Topics include the positive and negative aspects of Habitual Behavior, details of research into neurons' role in habits, and the potential development of drugs and Behavioral methods to control habits.
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A Dual Operator View of Habitual Behavior Reflecting Cortical and Striatal Dynamics
Neuron, 2013Co-Authors: Kyle S. Smith, Ann M. GraybielAbstract:SUMMARY Habitsarenotoriouslydifficulttobreakand,ifbroken, are usually replaced by new routines. To examine the neural basis of these characteristics, we recorded spike activity in cortical and striatal habit sites as rats learned maze tasks. Overtraining induced a shift from purposeful to Habitual Behavior. This shift coincided with the activation of neuronal ensembles in the infralimbic neocortex and the sensorimotor striatum, which became engaged simultaneously but developed changes in spike activity with distinct time courses and stability. The striatum rapidly acquired an action-bracketing activity pattern insensitive to reward devaluation but sensitive to running automaticity.Asimilarpatterndevelopedintheupper layers of the infralimbic cortex, but it formed only late during overtraining and closely tracked habit states. Selective optogenetic disruption of infralimbic activity during overtraining prevented habit formation. We suggest that learning-related spiking dynamics of both striatum and neocortex are necessary, as dual operators, for habit crystallization.
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Using optogenetics to study habits
Brain research, 2013Co-Authors: Kyle S. Smith, Ann M. GraybielAbstract:It is now well documented that optogenetics brings to neuroscience a long sought-after foothold to study the causal role of millisecond-scale activity of genetically or anatomically defined populations of neurons. Progress is rapid, and, as evidenced by the work collected in this Special Issue, the possibilities of what can now be done are almost dizzying. Even for those concerned with complex phenomena, such as Behavioral habits and flexibility, signs are that we could be on the threshold of a leap in scientific understanding. Here. we note this special time in neuroscience by the example of our use of optogenetics to study Habitual Behavior. We present a basic sketch of the neural circuitry of Habitual Behavior built mainly on findings from experiments in which lesion and drug microinjection techniques were employed in combination with sophisticated Behavioral analysis. We then outline the types of questions that now can be approached through the use of optogenetic approaches, and, as an example, we summarize the results of a recent study of ours in which we took this approach to probe the neural basis of habit formation. With optogenetic methods, we were able to demonstrate that a small site in the medial prefrontal cortex can control habits online during their execution, and we were able to control new habits when they competed with prior ones. The nearly immediate effect of disabling this site optogenetically suggests the existence of a mechanism for moment-to-moment monitoring of Behaviors that long have been thought to be almost automatic and reflexive. This example highlights the kind of new knowledge that can be gained by the carefully timed use of optogenetic tools. This article is part of a Special Issue entitled Optogenetics (7th BRES). This article is part of a Special Issue entitled Optogenetics (7th BRES).
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reversible online control of Habitual Behavior by optogenetic perturbation of medial prefrontal cortex
Proceedings of the National Academy of Sciences of the United States of America, 2012Co-Authors: Kyle S. Smith, Arti Virkud, Karl Deisseroth, Ann M. GraybielAbstract:Habits tend to form slowly but, once formed, can have great stability. We probed these temporal characteristics of Habitual Behaviors by intervening optogenetically in forebrain habit circuits as rats performed well-ingrained Habitual runs in a T-maze. We trained rats to perform a maze habit, confirmed the Habitual Behavior by devaluation tests, and then, during the maze runs (ca. 3 s), we disrupted population activity in a small region in the medial prefrontal cortex, the infralimbic cortex. In accordance with evidence that this region is necessary for the expression of habits, we found that this cortical disruption blocked Habitual Behavior. Notably, however, this blockade of Habitual performance occurred on line, within an average of three trials (ca. 9 s of inhibition), and as soon as during the first trial (<3 s). During subsequent weeks of training, the rats acquired a new Behavioral pattern. When we again imposed the same cortical perturbation, the rats regained the suppressed maze-running that typified the original habit, and, simultaneously, the more recently acquired habit was blocked. These online changes occurred within an average of two trials (ca. 6 s of infralimbic inhibition). Measured changes in generalized performance ability and motivation to consume reward were unaffected. This immediate toggling between breaking old habits and returning to them demonstrates that even semiautomatic Behaviors are under cortical control and that this control occurs online, second by second. These temporal characteristics define a framework for uncovering cellular transitions between fixed and flexible Behaviors, and corresponding disturbances in pathologies.
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Reversible online control of Habitual Behavior by optogenetic perturbation of medial prefrontal cortex
Proceedings of the National Academy of Sciences of the United States of America, 2012Co-Authors: Kyle S. Smith, Arti Virkud, Karl Deisseroth, Ann M. GraybielAbstract:Habits tend to form slowly but, once formed, can have great stability. We probed these temporal characteristics of Habitual Behaviors by intervening optogenetically in forebrain habit circuits as rats performed well-ingrained Habitual runs in a T-maze. We trained rats to perform a maze habit, confirmed the Habitual Behavior by devaluation tests, and then, during the maze runs (ca. 3 s), we disrupted population activity in a small region in the medial prefrontal cortex, the infralimbic cortex. In accordance with evidence that this region is necessary for the expression of habits, we found that this cortical disruption blocked Habitual Behavior. Notably, however, this blockade of Habitual performance occurred on line, within an average of three trials (ca. 9 s of inhibition), and as soon as during the first trial (
Henry H. Yin - One of the best experts on this subject based on the ideXlab platform.
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Striatal fast-spiking interneurons selectively modulate circuit output and are required for Habitual Behavior.
eLife, 2017Co-Authors: Justin K. O’hare, Kristen K. Ade, Henry H. Yin, Namsoo Kim, Erin Gaidis, Jeffrey M. Beck, Nicole CalakosAbstract:From biting fingernails to the daily commute, habits are sets of actions that can be completed almost without thinking and that are difficult to change or stop. Behavioral neuroscientists refer to habits as “stimulus-response” Behaviors, and know that forming a new habit requires a region deep within the brain called the dorsolateral striatum. Indeed, in this region, the outgoing neurons – which make up 95% of the cells - respond differently to incoming signals in mice that have learned habits compared to non-Habitual mice. However a question remained: what exactly was producing these differences? O’Hare et al. have now found, unexpectedly, that the answer resides not in the 95% of outgoing neurons, but rather in a rare type of cell known as the fast-spiking interneuron. This cell is connected to many others and it appears to act like a conductor, orchestrating the previously identified changes in the output neurons. These findings were made using mice that had been trained to press a lever for a sugar pellet reward. Habit was measured by how long mice kept pressing even if they had just been allowed to eat their fill of pellets and the test lever was no longer dispensing pellets. Habitual mice continue to press the lever in this circumstance, while other mice do not. O’Hare et al. found that inactivating the “conductor” cell made the output neurons respond in the opposite way to how they normally respond in Habitual mice. Further experiments showed that fast-spiking interneurons were also more easily activated in Habitual mice. To test whether this putative “conductor” cell was necessary for Habitual Behaviors, a technique known as chemogenetics was used to turn down its activity in Habitual mice. Indeed, reducing activity in the conductor cell blocked the Habitual Behavior. While some habits are a helpful and economical way to get through daily life, habits are also thought to be corrupted in a number of diseases such as neurodegenerative diseases, addictions and compulsions. Identifying this specific, yet rare, cell as a critical part of maintaining habits points out a new target to consider for therapies. Further work is needed before such treatments might become available to treat habit-related disorders; though O'Hare et al. are now taking steps in this direction by trying to work out how the fast-spiking interneuron changes its own activity when a habit is formed.
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Striatal fast-spiking interneurons drive Habitual Behavior
2017Co-Authors: Justin K. O’hare, Kristen K. Ade, Henry H. Yin, Namsoo Kim, Erin Gaidis, Jeffrey M. Beck, Nicole CalakosAbstract:Habit formation is a Behavioral adaptation that automates routine actions. Habitual Behavior correlates with broad reconfigurations of dorsolateral striatal (DLS) circuit properties that increase gain and shift pathway timing. The mechanism(s) for these circuit adaptations are unknown and could be responsible for Habitual Behavior. Here we find that a single class of interneuron, fast-spiking interneurons (FSIs), modulates all of these habit-predictive properties. Consistent with a role in habits, FSIs are more excitable in Habitual mice compared to goal-directed and acute chemogenetic inhibition of FSIs in DLS prevents the expression of Habitual lever pressing. In vivo recordings further reveal a previously unappreciated selective modulation of SPNs based on their firing patterns; FSIs inhibit most SPNs but paradoxically promote the activity of a subset displaying high fractions of gamma-frequency spiking. These results establish a microcircuit mechanism for habits and provide a new example of how interneurons mediate experience-dependent Behavior.
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Pathway-Specific Striatal Substrates for Habitual Behavior.
Neuron, 2016Co-Authors: Justin K. O’hare, Kristen K. Ade, Tatyana Sukharnikova, Stephen D. Van Hooser, Mark L. Palmeri, Henry H. Yin, Nicole CalakosAbstract:The dorsolateral striatum (DLS) is implicated in habit formation. However, the DLS circuit mechanisms underlying habit remain unclear. A key role for DLS is to transform sensorimotor cortical input into firing of output neurons that project to the mutually antagonistic direct and indirect basal ganglia pathways. Here we examine whether habit alters this input-output function. By imaging cortically evoked firing in large populations of pathway-defined striatal projection neurons (SPNs), we identify features that strongly correlate with Habitual Behavior on a subject-by-subject basis. Habitual Behavior correlated with strengthened DLS output to both pathways as well as a tendency for action-promoting direct pathway SPNs to fire before indirect pathway SPNs. In contrast, habit suppression correlated solely with a weakened direct pathway output. Surprisingly, all effects were broadly distributed in space. Together, these findings indicate that the striatum imposes broad, pathway-specific modulations of incoming activity to render learned motor Behaviors Habitual.
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methods for studying Habitual Behavior in mice
Current protocols in protein science, 2012Co-Authors: Mark A Rossi, Henry H. YinAbstract:Habit formation refers to the process by which goal-directed Behavior becomes automatized and less sensitive to changes in the value of the goal. It has clear relevance for our understanding of skill learning and addiction. Recent studies have begun to reveal the neural substrates underlying this process. This article summarizes what is known about the experimental methods used, and provides a protocol for generating and assessing habit formation in mice.
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Methods for studying Habitual Behavior in mice.
Current protocols in neuroscience, 2012Co-Authors: Mark A Rossi, Henry H. YinAbstract:Habit formation refers to the process by which goal-directed Behavior becomes automatized and less sensitive to changes in the value of the goal. It has clear relevance for our understanding of skill learning and addiction. Recent studies have begun to reveal the neural substrates underlying this process. This unit summarizes what is known about the experimental methods used, and provides a protocol for generating and assessing habit formation in mice.
Justin K. O’hare - One of the best experts on this subject based on the ideXlab platform.
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Striatal fast-spiking interneurons selectively modulate circuit output and are required for Habitual Behavior.
eLife, 2017Co-Authors: Justin K. O’hare, Kristen K. Ade, Henry H. Yin, Namsoo Kim, Erin Gaidis, Jeffrey M. Beck, Nicole CalakosAbstract:From biting fingernails to the daily commute, habits are sets of actions that can be completed almost without thinking and that are difficult to change or stop. Behavioral neuroscientists refer to habits as “stimulus-response” Behaviors, and know that forming a new habit requires a region deep within the brain called the dorsolateral striatum. Indeed, in this region, the outgoing neurons – which make up 95% of the cells - respond differently to incoming signals in mice that have learned habits compared to non-Habitual mice. However a question remained: what exactly was producing these differences? O’Hare et al. have now found, unexpectedly, that the answer resides not in the 95% of outgoing neurons, but rather in a rare type of cell known as the fast-spiking interneuron. This cell is connected to many others and it appears to act like a conductor, orchestrating the previously identified changes in the output neurons. These findings were made using mice that had been trained to press a lever for a sugar pellet reward. Habit was measured by how long mice kept pressing even if they had just been allowed to eat their fill of pellets and the test lever was no longer dispensing pellets. Habitual mice continue to press the lever in this circumstance, while other mice do not. O’Hare et al. found that inactivating the “conductor” cell made the output neurons respond in the opposite way to how they normally respond in Habitual mice. Further experiments showed that fast-spiking interneurons were also more easily activated in Habitual mice. To test whether this putative “conductor” cell was necessary for Habitual Behaviors, a technique known as chemogenetics was used to turn down its activity in Habitual mice. Indeed, reducing activity in the conductor cell blocked the Habitual Behavior. While some habits are a helpful and economical way to get through daily life, habits are also thought to be corrupted in a number of diseases such as neurodegenerative diseases, addictions and compulsions. Identifying this specific, yet rare, cell as a critical part of maintaining habits points out a new target to consider for therapies. Further work is needed before such treatments might become available to treat habit-related disorders; though O'Hare et al. are now taking steps in this direction by trying to work out how the fast-spiking interneuron changes its own activity when a habit is formed.
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Striatal fast-spiking interneurons drive Habitual Behavior
2017Co-Authors: Justin K. O’hare, Kristen K. Ade, Henry H. Yin, Namsoo Kim, Erin Gaidis, Jeffrey M. Beck, Nicole CalakosAbstract:Habit formation is a Behavioral adaptation that automates routine actions. Habitual Behavior correlates with broad reconfigurations of dorsolateral striatal (DLS) circuit properties that increase gain and shift pathway timing. The mechanism(s) for these circuit adaptations are unknown and could be responsible for Habitual Behavior. Here we find that a single class of interneuron, fast-spiking interneurons (FSIs), modulates all of these habit-predictive properties. Consistent with a role in habits, FSIs are more excitable in Habitual mice compared to goal-directed and acute chemogenetic inhibition of FSIs in DLS prevents the expression of Habitual lever pressing. In vivo recordings further reveal a previously unappreciated selective modulation of SPNs based on their firing patterns; FSIs inhibit most SPNs but paradoxically promote the activity of a subset displaying high fractions of gamma-frequency spiking. These results establish a microcircuit mechanism for habits and provide a new example of how interneurons mediate experience-dependent Behavior.
-
Pathway-Specific Striatal Substrates for Habitual Behavior.
Neuron, 2016Co-Authors: Justin K. O’hare, Kristen K. Ade, Tatyana Sukharnikova, Stephen D. Van Hooser, Mark L. Palmeri, Henry H. Yin, Nicole CalakosAbstract:The dorsolateral striatum (DLS) is implicated in habit formation. However, the DLS circuit mechanisms underlying habit remain unclear. A key role for DLS is to transform sensorimotor cortical input into firing of output neurons that project to the mutually antagonistic direct and indirect basal ganglia pathways. Here we examine whether habit alters this input-output function. By imaging cortically evoked firing in large populations of pathway-defined striatal projection neurons (SPNs), we identify features that strongly correlate with Habitual Behavior on a subject-by-subject basis. Habitual Behavior correlated with strengthened DLS output to both pathways as well as a tendency for action-promoting direct pathway SPNs to fire before indirect pathway SPNs. In contrast, habit suppression correlated solely with a weakened direct pathway output. Surprisingly, all effects were broadly distributed in space. Together, these findings indicate that the striatum imposes broad, pathway-specific modulations of incoming activity to render learned motor Behaviors Habitual.
Kyle S. Smith - One of the best experts on this subject based on the ideXlab platform.
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Sign-tracking Behavior is sensitive to outcome devaluation in a devaluation context-dependent manner: implications for analyzing Habitual Behavior.
Learning & memory (Cold Spring Harbor N.Y.), 2020Co-Authors: Kenneth A. Amaya, Jeffrey J. Stott, Kyle S. SmithAbstract:Motivationally attractive cues can draw in Behavior in a phenomenon termed incentive salience. Incentive cue attraction is an important model for animal models of drug seeking and relapse. One question of interest is the extent to which the pursuit of motivationally attractive cues is related to the value of the paired outcome or can become unrelated and Habitual. We studied this question using a sign-tracking (ST) paradigm in rats, in which a lever stimulus preceding food reward comes to elicit conditioned lever-interaction Behavior. We asked whether reinforcer devaluation by means of conditioned taste aversion, a classic test of Habitual Behavior, can modify ST to incentive cues, and whether this depends upon the manner in which reinforcer devaluation takes place. In contrast to several recent reports, we conclude that ST is indeed sensitive to reinforcer devaluation. However, this effect depends critically upon the congruence between the context in which taste aversion is learned and the context in which it is tested. When the taste aversion successfully transfers to the testing context, outcome value strongly influences ST Behavior, both when the outcome is withheld (in extinction) and when animals can learn from outcome feedback (reacquisition). When taste aversion does not transfer to the testing context, ST remains high. In total, the extent to which ST persists after outcome devaluation is closely related to the extent to which that outcome is truly devalued in the task context. We believe this effect of context on devaluation can reconcile contradictory findings about the flexibility/inflexibility of ST. We discuss this literature and relate our findings to the study of habits generally.
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Good habits, bad habits.
Scientific American, 2014Co-Authors: Ann M. Graybiel, Kyle S. SmithAbstract:The article discusses research by the authors and others into the neurophysiological basis of habit formation, focusing on the role of brain circuits in the striatum and neocortex. Topics include the positive and negative aspects of Habitual Behavior, details of research into neurons' role in habits, and the potential development of drugs and Behavioral methods to control habits.
-
A Dual Operator View of Habitual Behavior Reflecting Cortical and Striatal Dynamics
Neuron, 2013Co-Authors: Kyle S. Smith, Ann M. GraybielAbstract:SUMMARY Habitsarenotoriouslydifficulttobreakand,ifbroken, are usually replaced by new routines. To examine the neural basis of these characteristics, we recorded spike activity in cortical and striatal habit sites as rats learned maze tasks. Overtraining induced a shift from purposeful to Habitual Behavior. This shift coincided with the activation of neuronal ensembles in the infralimbic neocortex and the sensorimotor striatum, which became engaged simultaneously but developed changes in spike activity with distinct time courses and stability. The striatum rapidly acquired an action-bracketing activity pattern insensitive to reward devaluation but sensitive to running automaticity.Asimilarpatterndevelopedintheupper layers of the infralimbic cortex, but it formed only late during overtraining and closely tracked habit states. Selective optogenetic disruption of infralimbic activity during overtraining prevented habit formation. We suggest that learning-related spiking dynamics of both striatum and neocortex are necessary, as dual operators, for habit crystallization.
-
Using optogenetics to study habits
Brain research, 2013Co-Authors: Kyle S. Smith, Ann M. GraybielAbstract:It is now well documented that optogenetics brings to neuroscience a long sought-after foothold to study the causal role of millisecond-scale activity of genetically or anatomically defined populations of neurons. Progress is rapid, and, as evidenced by the work collected in this Special Issue, the possibilities of what can now be done are almost dizzying. Even for those concerned with complex phenomena, such as Behavioral habits and flexibility, signs are that we could be on the threshold of a leap in scientific understanding. Here. we note this special time in neuroscience by the example of our use of optogenetics to study Habitual Behavior. We present a basic sketch of the neural circuitry of Habitual Behavior built mainly on findings from experiments in which lesion and drug microinjection techniques were employed in combination with sophisticated Behavioral analysis. We then outline the types of questions that now can be approached through the use of optogenetic approaches, and, as an example, we summarize the results of a recent study of ours in which we took this approach to probe the neural basis of habit formation. With optogenetic methods, we were able to demonstrate that a small site in the medial prefrontal cortex can control habits online during their execution, and we were able to control new habits when they competed with prior ones. The nearly immediate effect of disabling this site optogenetically suggests the existence of a mechanism for moment-to-moment monitoring of Behaviors that long have been thought to be almost automatic and reflexive. This example highlights the kind of new knowledge that can be gained by the carefully timed use of optogenetic tools. This article is part of a Special Issue entitled Optogenetics (7th BRES). This article is part of a Special Issue entitled Optogenetics (7th BRES).
-
reversible online control of Habitual Behavior by optogenetic perturbation of medial prefrontal cortex
Proceedings of the National Academy of Sciences of the United States of America, 2012Co-Authors: Kyle S. Smith, Arti Virkud, Karl Deisseroth, Ann M. GraybielAbstract:Habits tend to form slowly but, once formed, can have great stability. We probed these temporal characteristics of Habitual Behaviors by intervening optogenetically in forebrain habit circuits as rats performed well-ingrained Habitual runs in a T-maze. We trained rats to perform a maze habit, confirmed the Habitual Behavior by devaluation tests, and then, during the maze runs (ca. 3 s), we disrupted population activity in a small region in the medial prefrontal cortex, the infralimbic cortex. In accordance with evidence that this region is necessary for the expression of habits, we found that this cortical disruption blocked Habitual Behavior. Notably, however, this blockade of Habitual performance occurred on line, within an average of three trials (ca. 9 s of inhibition), and as soon as during the first trial (<3 s). During subsequent weeks of training, the rats acquired a new Behavioral pattern. When we again imposed the same cortical perturbation, the rats regained the suppressed maze-running that typified the original habit, and, simultaneously, the more recently acquired habit was blocked. These online changes occurred within an average of two trials (ca. 6 s of infralimbic inhibition). Measured changes in generalized performance ability and motivation to consume reward were unaffected. This immediate toggling between breaking old habits and returning to them demonstrates that even semiautomatic Behaviors are under cortical control and that this control occurs online, second by second. These temporal characteristics define a framework for uncovering cellular transitions between fixed and flexible Behaviors, and corresponding disturbances in pathologies.
