Hierarchical control over effortful behavior by rodent medial frontal cortex : a computational model

The anterior cingulate cortex (ACC) has been the focus of intense research interest in recent years. Although separate theories relate ACC function variously to conflict monitoring, reward processing, action selection, decision making, and more, damage to the ACC mostly spares performance on tasks that exercise these functions, indicating that they are not in fact unique to the ACC. Further, most theories do not address the most salient consequence of ACC damage: impoverished action generation in the presence of normal motor ability. In this study we develop a computational model of the rodent medial prefrontal cortex that accounts for the behavioral sequelae of ACC damage, unifies many of the cognitive functions attributed to it, and provides a solution to an outstanding question in cognitive control research-how the control system determines and motivates what tasks to perform. The theory derives from recent developments in the formal study of hierarchical control and learning that highlight computational efficiencies afforded when collections of actions are represented based on their conjoint goals. According to this position, the ACC utilizes reward information to select tasks that are then accomplished through top-down control over action selection by the striatum. Computational simulations capture animal lesion data that implicate the medial prefrontal cortex in regulating physical and cognitive effort. Overall, this theory provides a unifying theoretical framework for understanding the ACC in terms of the pivotal role it plays in the hierarchical organization of effortful behavior

Animation visual effects demo reel

My Senior Thesis Project is a visual effects demo reel that showcases my abilities to create realistic visual effects. The demo reel is two and half minutes of the best work I completed this semester compiled in one video. I completed seven visual effect projects over the course of this semester. I used various computer programs to complete these projects including Adobe After Effects, Adobe Photoshop, Autodesk Maya, Autodesk Softlmage, PFTrackerX, Cameratracker, and Trapcode Particular. The intent of my demo reel is to show professional level visual effects to prospective employers and to show an audience. The seven projects I have completed at the end of the semester are a few 3D set extensions, screen replacement, artificial heads up display, arm tracking and fire simulation, and a short replacement videos.Thesis (B.?.)Honors Colleg

The Neuroscience of Preferences

The expression of preference reflects the influence of two broad modes of judgment—intuition and deliberation (Kahneman and Frederick 2002). The intuitive mode includes emotional reactions (e.g. Loewenstein 1996), but it also includes heuristic process which are largely perceptual or cognitive in nature. Intuitive processes occur early in a judgment process; they are fast and largely automatic. This is in contrast with deliberative processes which tend to occur later in a judgement process, are slower, and are more controlled. Intuitive and deliberative processes interact with each other, although they are often in conflict, and there is some evidence that they are anatomically separated in the brain

Role of electronic thermal transport in amorphous metal recrystallization: a molecular dynamics study

Recrystallization of glasses is important in a wide range of applications including electronics and reactive materials. Molecular dynamics (MD) has been used to provide an atomic picture of this process, but prior work has neglected the thermal transport role of electrons, the dominant thermal carrier in metallic systems. We characterize the role of electronic thermal conductivity on the velocity of recrystallization in Ni using MD coupled to a continuum description of electronic thermal transport via a two-temperature model. Our simulations show that for strong enough coupling between electrons and ions, the increased thermal conductivity removes the heat from the exothermic recrystallization process more efficiently, leading to a lower effective temperature at the recrystallization front and, consequently, lower propagation velocity. We characterize how electron-phonon coupling strength and system size affects front propagation velocity. Interestingly, we find that initial recrystallization velocity increases with decreasing in system size due to higher overall temperatures. Overall, we show that a more accurate description of thermal transport due to the incorporation of electrons results in better agreement with experiments

Temporal Prediction Errors in a Passive Learning Task Activate Human Striatum

AbstractFunctional MRI experiments in human subjects strongly suggest that the striatum participates in processing information about the predictability of rewarding stimuli. However, stimuli can be unpredictable in character (what stimulus arrives next), unpredictable in time (when the stimulus arrives), and unpredictable in amount (how much arrives). These variables have not been dissociated in previous imaging work in humans, thus conflating possible interpretations of the kinds of expectation errors driving the measured brain responses. Using a passive conditioning task and fMRI in human subjects, we show that positive and negative prediction errors in reward delivery time correlate with BOLD changes in human striatum, with the strongest activation lateralized to the left putamen. For the negative prediction error, the brain response was elicited by expectations only and not by stimuli presented directly; that is, we measured the brain response to nothing delivered (juice expected but not delivered) contrasted with nothing delivered (nothing expected)

Probing the Dust and Gas in the Transitional Disk of CS Cha with Spitzer

Here we present the Spitzer IRS spectrum of CS Cha, a member of the ~2 Myr old Chamaeleon star-forming region, which reveals an optically thick circumstellar disk truncated at ~43 AU, the largest hole modeled in a transitional disk to date. Within this inner hole, ~5x10^-5 lunar masses of dust are located in a small optically thin inner region which extends from 0.1 to 1 AU. In addition, the disk of CS Cha has bigger grain sizes and more settling than the previously modeled transitional disks DM Tau, GM Aur, and CoKu Tau/4, suggesting that CS Cha is in a more advanced state of dust evolution. The Spitzer IRS spectrum also shows [Ne II] 12.81 micron fine-structure emission with a luminosity of 1.3x10^29 ergs s^-1, indicating that optically thin gas is present in this ~43 AU hole, in agreement with H_alpha measurements and a UV excess which indicate that CS Cha is still accreting 1.2x10^-8 M_sun yr^-1. We do not find a correlation of the [Ne II] flux with L_X, however, there is a possible correlation with mass accretion rate, which if confirmed would suggest that EUV fluxes due to accretion are the main agent for formation of the [Ne II] line.Comment: accepted to ApJ Letter

Management of failed spinal anaesthesia for caesarean section

Background. Failed spinal anaesthesia for caesarean section (CS) may be partial or complete and the subsequent discomfort is the most commonly cited cause of litigation in obstetric anaesthesia.Objectives. To determine if there is a standardised approach to: (i) testing the level of block of spinal anaesthesia; and (ii) the management of failed spinal anaesthesia for CS.Methods. A structured questionnaire to ascertain the current practice of testing the level of block and management of three different scenarios of failed spinal anaesthesia was distributed to 51 government hospitals in KwaZulu-Natal, South Africa (SA). All obstetric anaes­thetic service providers, ranging from interns to specialist anaesthetists, were invited to complete the questionnaire.Results. A total of 375 responses were received from 42 of the 51 hospitals surveyed. Specialist anaesthetists managed failure of spinal anaesthesia significantly differently than other anaesthetic service providers. Specialists were more likely to convert to a general anaesthetic (GA), while others were more likely to repeat spinal anaesthesia or administer intravenous ketamine, midazolam and opioids. Only 212 respondents (56%) tested the level of block and there was no difference between the groups with regard to the method of assessment of height (p=0.15). Non-specialists, however, accepted a significantly lower level of block, using pinprick, than specialists (p=0.027), which could lead to a higher failure rate. More than one-third of non-specialists did not consider themselves competent to perform a GA and >90% of respondents agreed that a ‘failed’ spinal algorithm would be useful.Conclusion. There is a need for standardised assessment of the adequacy of spinal anaesthesia for CS in SA, as well as a failed spinal algorithm.