A Model of Predictive Postural Control Against Floor Tilting in Rats

Humans and animals learn the internal model of bodies and environments from their experience and stabilize posture against disturbances based on the predicted future states according to the internal model. We evaluated the mechanism of predictive control during standing, by using rats to construct a novel experimental system and comparing their behaviors with a mathematical model. In the experiments, rats (n = 6) that were standing upright using their hindlimbs were given a sensory input of light, after a certain period, the floor under them tilted backward. Initially, this disturbance induced a large postural response, including backward rotation of the center-of-mass angle and hindlimb segments. However, the rats gradually adjusted to the disturbance after experiencing 70 sequential trials, and a reduction in the amplitude of postural response was noted. We simulated the postural control of the rats under disturbance using an inverted pendulum model and model predictive control (MPC). MPC is a control method for predicting the future state using an internal model of the control target. It provides control inputs that optimize the predicted future states. Identification of the predictive and physiological parameters so that the simulation corresponds to the experiment, resulted in a value of predictive horizon (0.96 s) close to the interval time in the experiment (0.9–1.15 s). These results suggest that the rats predict posture dynamics under disturbance based on the timing of the sensory input and that the central nervous system provides plasticity mechanisms to acquire the internal model for MPC.

Mate Preference Plasticity in a Critically Endangered Frog: Implications for Conservation Breeding

Variation in female mate preferences for male traits remains poorly understood (both among and within females), despite having important evolutionary and conservation implications, particularly for captive breeding. Here, we investigate female mate preferences for male advertisement call frequency, and determine whether preferences vary over repeated trials, in the critically endangered southern corroboree frog, Pseudophryne corroboree. We conducted a series of phonotaxis trials in a six-speaker arena where naïve, captive-bred, virgin females were offered a choice between low, average and high frequency male advertisement calls, with a subset of females tested repeatedly. In the first trial, we found no evidence for a population-level preference for call frequency, but females spent less time in the low call zone than expected by chance. However, our results showed that female mate preferences changed over sequential trials. Females spent significantly more time in the low frequency call zone in the third trial compared to the first trial, and, in the last trial, females exhibited a significant population-level preference for low frequency calls. Subsequently, repeatability estimates of female preferences were low and did not significantly deviate from zero. Our results indicate that female P. corroboree mate preferences can exhibit temporal variation, and suggest that females are more attracted to low call frequencies after repeated exposure. These findings imply that female P. corroboree may become choosier over time, and highlight the potential for mate preferences to exhibit phenotypic plasticity within a single reproductive cycle. Overall, these findings provide the first information on mate preferences in P. corroboree, and emphasize the importance of considering individual variation in mate choice studies. From a conservation perspective, knowledge of individual variation in female mate preferences may be used to conduct behavioral manipulations in captivity that facilitate the breeding of genetically valuable individuals, and improve the success of conservation breeding programs.

A management-scale investigation of consistent individual differences in behaviour and trapping bias in Sea Lamprey (Petromyzon marinus)

The Sea Lamprey (Petromyzon marinus) is invasive in the Laurentian Great Lakes. Trapping in large rivers could suppress Sea Lamprey recruitment by removing migrating adults prior to spawning. Currently, the proportion of Sea Lamprey trapped (efficiency) is too low for control purposes, possibly because trapping is biased toward certain behavioural types. We tested if individual differences in time to enter a novel environment (risk-taking) and proportion of time moving (activity) under standardized laboratory conditions were correlated with time to encounter and enter a trap in the field. 638 Sea Lamprey were tagged, assessed for risk-taking and activity in sequential trials, and released in the river to be trapped. In the laboratory, individuals differed consistently in risk-taking and activity behaviours, and more active individuals entered a simulated trap sooner than less active individuals. In the field, however, the times to first trap encounter, and capture in a trap, were not correlated with risk-taking or activity. Our study provides a novel demonstration of how patterns from small-scale behavioural studies may not extend to management-scale applications.

Event-Related Potentials During Decision-Making in a Mixed-Strategy Game

The decisions we make are sometimes influenced by interactions with other agents. Previous studies have suggested that the prefrontal cortex plays an important role in decision-making and that the dopamine system underlies processes of motivation, motor preparation, and reinforcement learning. However, the physiological mechanisms underlying how the prefrontal cortex and the dopaminergic system are involved in decision-making remain largely unclear. The present study aimed to determine how decision strategies influence event-related potentials (ERPs). We also tested the effect of levodopa, a dopamine precursor, on decision-making and ERPs in a randomized double-blind placebo-controlled investigation. The subjects performed a matching-pennies task against an opposing virtual computer player by choosing between right and left targets while their ERPs were recorded. According to the rules of the matching-pennies task, the subject won the trial when they chose the same side as the opponent, and lost otherwise. We set three different task rules: (1) with the alternation (ALT) rule, the computer opponent made alternating choices of right and left in sequential trials; (2) with the random (RAND) rule, the opponent randomly chose between right and left; and (3) with the GAME rule, the opponent analyzed the subject’s past choices to predict the subject’s next choice, and then chose the opposite side. A sustained medial ERP became more negative toward the time of the subject’s target choice. A biphasic potential appeared when the opponent’s choice was revealed after the subject’s response. The ERPs around the subject’s choice were greater in RAND and GAME than in ALT, and the negative peak was enhanced by levodopa. In addition to these medial ERPs, we observed lateral frontal ERPs tuned to the choice direction. The signals emerged around the choice period selectively in RAND and GAME when levodopa was administered. These results suggest that decision processes are modulated by the dopamine system when a complex and strategic decision is required, which may reflect decision updating with dopaminergic prediction error signals.

Organizational Policy Learning and Evaluation Using Monte Carlo Methods

Organizations need to constantly learn, develop, and evaluate new strategies and policies for their effective operation. Unsupervised reinforcement learning is becoming a highly useful tool, since rewards and punishments in different forms are pervasive and present in a wide variety of decision-making scenarios. By observing the outcome of a sufficient number of repeated trials, one would gradually learn the value and usefulness of a particular policy or strategy. However, in a given environment, the outcomes resulting from different trials are subject to external chance influence and variations. In learning about the usefulness of a given policy, significant costs are involved in systematically undertaking the sequential trials; therefore, in most learning episodes, one would wish to keep the cost within bounds by adopting learning efficient stopping rules. In this Chapter, we explain the deployment of different learning strategies in given environments for reinforcement learning policy evaluation and review, and we present suggestions for their practical use and applications.

LGG-21. MR-GUIDED LASER INTERSTITIAL THERMAL THERAPY FOR UNRESECTABLE AND SYMPTOMATIC PEDIATRIC LOW GRADE GLIOMA

BACKGROUND Pediatric low-grade gliomas (LGG) not amenable to resection, while often indolent, represent a significant source of cancer-related morbidity and an unmet therapeutic need. Standardly, these patients are treated with sequential lines of chemotherapy, while delaying as long as possible radiation. Magnetic resonance-guided laser interstitial therapy (LITT) is a minimally invasive procedure that utilizes real-time MR thermography to ablate brain lesions. METHODS A 15-year-old girl was diagnosed with a suprasellar, hypothalamic LGG, BRAF V600E mutation positive. The tumor was unresectable, and due to progressive vision loss and headaches, the patient underwent treatment. Despite sequential trials of thioguanine/procarbazine/lomustine/vincristine, carboplatin/vincristine, dabrafenib, and combination dabrafenib/trametinib, the patient continued to experience debilitating headaches, malnutrition, school absenteeism, and overall poor quality-of-life. Using real-time, sequential MRI-thermometry and the Neuroblate cooled directional laser catheter, the bulk of the enhancing tumor was heated to a killing temperature. RESULTS At 1-year post LITT, the patient’s symptoms were dramatically improved, including greatly improved headaches, malnutrition, school absenteeism, and overall quality of life. LITT was generally well tolerated, though the patient had slight progressive left homonymous hemianopia, thought secondary to LITT impact on the optic tracts. The tumor progressively shrank over the year post-LITT to a peak of 42% volume reduction. CONCLUSION We report a case of a pediatric patient with an unresectable low grade glioma who underwent LITT with excellent clinical and radiographic effects. LITT should be considered for children with unresectable and morbid LGGs that fail to respond to more conventional therapies.