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Articles 1 - 8 of 8
Full-Text Articles in Psychology
A Computational Psychiatry Approach Identifies How Alpha-2a Noradrenergic Agonist Guanfacine Affects Feature-Based Reinforcement Learning In The Macaque, S. A. Hassani, M. Oemisch, M. Balcarras, S. Westendorff, S Ardid, M. A. Van Der Meer, P. Tiesinga, T. Womelsdorf
A Computational Psychiatry Approach Identifies How Alpha-2a Noradrenergic Agonist Guanfacine Affects Feature-Based Reinforcement Learning In The Macaque, S. A. Hassani, M. Oemisch, M. Balcarras, S. Westendorff, S Ardid, M. A. Van Der Meer, P. Tiesinga, T. Womelsdorf
Dartmouth Scholarship
Noradrenaline is believed to support cognitive flexibility through the alpha 2A noradrenergic receptor (a2A-NAR) acting in prefrontal cortex. Enhanced flexibility has been inferred from improved working memory with the a2A-NA agonist Guanfacine. But it has been unclear whether Guanfacine improves specific attention and learning mechanisms beyond working memory, and whether the drug effects can be formalized computationally to allow single subject predictions. We tested and confirmed these suggestions in a case study with a healthy nonhuman primate performing a feature-based reversal learning task evaluating performance using Bayesian and Reinforcement learning models. In an initial dose-testing phase we found a Guanfacine …
Variations In Crowding, Saccadic Precision, And Spatial Localization Reveal The Shared Topology Of Spatial Vision, John A. Greenwood, Martin Szinte, Bilge Sayim, Patrick Cavanagh
Variations In Crowding, Saccadic Precision, And Spatial Localization Reveal The Shared Topology Of Spatial Vision, John A. Greenwood, Martin Szinte, Bilge Sayim, Patrick Cavanagh
Dartmouth Scholarship
Visual sensitivity varies across the visual field in several characteristic ways. For example, sensitivity declines sharply in peripheral (vs. foveal) vision and is typically worse in the upper (vs. lower) visual field. These variations can affect processes ranging from acuity and crowding (the deleterious effect of clutter on object recognition) to the precision of saccadic eye movements. Here we examine whether these variations can be attributed to a common source within the visual system. We first compared the size of crowding zones with the precision of saccades using an oriented clock target and two adjacent flanker elements. We report that …
Reconstructing Representations Of Dynamic Visual Objects In Early Visual Cortex, Edmund Chong, Ariana M. Familiar, Won Mok Shim
Reconstructing Representations Of Dynamic Visual Objects In Early Visual Cortex, Edmund Chong, Ariana M. Familiar, Won Mok Shim
Dartmouth Scholarship
As raw sensory data are partial, our visual system extensively fills in missing details, creating enriched percepts based on incomplete bottom-up information. Despite evidence for internally generated representations at early stages of cortical processing, it is not known whether these representations include missing information of dynamically transforming objects. Long-range apparent motion (AM) provides a unique test case because objects in AM can undergo changes both in position and in features. Using fMRI and encoding methods, we found that the “intermediate” orientation of an apparently rotating grating, never presented in the retinal input but interpolated during AM, is reconstructed in population-level, …
Belief About Nicotine Selectively Modulates Value And Reward Prediction Error Signals In Smokers, Xiaosi Gu, Terry Lohrenz, Ramiro Salas, Philip R. Baldwin, Alireza Soltani
Belief About Nicotine Selectively Modulates Value And Reward Prediction Error Signals In Smokers, Xiaosi Gu, Terry Lohrenz, Ramiro Salas, Philip R. Baldwin, Alireza Soltani
Dartmouth Scholarship
Little is known about how prior beliefs impact biophysically described processes in the presence of neuroactive drugs, which presents a profound challenge to the understanding of the mechanisms and treatments of addiction. We engineered smokers' prior beliefs about the presence of nicotine in a cigarette smoked before a functional magnetic resonance imaging session where subjects carried out a sequential choice task. Using a model-based approach, we show that smokers' beliefs about nicotine specifically modulated learning signals (value and reward prediction error) defined by a computational model of mesolimbic dopamine systems. Belief of "no nicotine in cigarette" (compared with "nicotine in …
Normal Acquisition Of Expertise With Greebles In Two Cases Of Acquired Prosopagnosia, Constantin Rezlescu, Jason J. S. Barton, David Pitcher, Bradley Duchaine
Normal Acquisition Of Expertise With Greebles In Two Cases Of Acquired Prosopagnosia, Constantin Rezlescu, Jason J. S. Barton, David Pitcher, Bradley Duchaine
Dartmouth Scholarship
Face recognition is generally thought to rely on different neurocognitive mechanisms than most types of objects, but the specificity of these mechanisms is debated. One account suggests the mechanisms are specific to upright faces, whereas the expertise view proposes the mechanisms operate on objects of high within-class similarity with which an observer has become proficient at rapid individuation. Much of the evidence cited in support of the expertise view comes from laboratory-based training experiments involving computer-generated objects called greebles that are designed to place face-like demands on recognition mechanisms. A fundamental prediction of the expertise hypothesis is that recognition deficits …
Exploring Emotions Using Invasive Methods: Review Of 60 Years Of Human Intracranial Electrophysiology, Sean A. Guillory, Krzysztof A. Bujarski
Exploring Emotions Using Invasive Methods: Review Of 60 Years Of Human Intracranial Electrophysiology, Sean A. Guillory, Krzysztof A. Bujarski
Dartmouth Scholarship
Over the past 60 years, human intracranial electrophysiology (HIE) has been used to characterize seizures in patients with epilepsy. Secondary to the clinical objectives, electrodes implanted intracranially have been used to investigate mechanisms of human cognition. In addition to studies of memory and language, HIE methods have been used to investigate emotions. The aim of this review is to outline the contribution of HIE (electrocorticography, single-unit recording and electrical brain stimulation) to our understanding of the neural representations of emotions. We identified 64 papers dating back to the mid-1950s which used HIE techniques to study emotional states. Evidence from HIE …
Investigating Habits: Strategies,Technologies And Models, Kyle S. Smith, Ann M. Graybiel
Investigating Habits: Strategies,Technologies And Models, Kyle S. Smith, Ann M. Graybiel
Dartmouth Scholarship
Understanding habits at a biological level requires a combination of behavioral observations and measures of ongoing neural activity. Theoretical frameworks as well as definitions of habitual behaviors emerging from classic behavioral research have been enriched by new approaches taking account of the identification of brain regions and circuits related to habitual behavior. Together, this combination of experimental and theoretical work has provided key insights into how brain circuits underlying action-learning and action-selection are organized, and how a balance between behavioral flexibility and fixity is achieved. New methods to monitor and manipulate neural activity in real time are allowing us to …
Microsaccade Rate Varies With Subjective Visibility During Motion-Induced Blindness, Po-Jang Hsieh, Peter U. Tse
Microsaccade Rate Varies With Subjective Visibility During Motion-Induced Blindness, Po-Jang Hsieh, Peter U. Tse
Dartmouth Scholarship
Motion-induced blindness (MIB) occurs when a dot embedded in a motion field subjectively vanishes. Here we report the first psychophysical data concerning effects of microsaccade/eyeblink rate upon perceptual switches during MIB. We find that the rate of microsaccades/eyeblink rises before and after perceptual transitions from not seeing to seeing the dot, and decreases before perceptual transitions from seeing it to not seeing it. In addition, event-related fMRI data reveal that, when a dot subjectively reappears during MIB, the blood oxygen-level dependent (BOLD) signal increases in V1v and V2v and decreases in contralateral hMT+. These BOLD signal changes observed upon perceptual …