Biology subjects

Fortune, E. S.

Publications and source records attributed to Fortune, E. S..

3 recordsLinked to original sources

bioRxiv2023

Organisms employ a mode-switching strategy for solving the explore-vs-exploit problem

The inescapable link between sensing and movement generates a conflict between producing costly movements for gathering information ("explore") versus using previously acquired information to achieve a goal ("exploit"). Determining the optimal balance between explore and exploit is a computationally intractable problem, necessitating the use of heuristics. We looked to nature to measure and model the solutions used by organisms. Here we show that the electric fish Eigenmannia virescens uses a salience-dependent mode-switching strategy to solve the explore-exploit conflict during a refuge tracking task. The fish produced distinctive non-Gaussian (i.e., non-normal) distributions of movement velocities characterized by sharp peaks for slower, task-oriented "exploit" movements and broad shoulders for faster, "explore" movements. The measures of non-normality increased in relation to increased sensory salience. Data from ten phylogenetically diverse organisms, from amoebae to humans, revealed the same distinctive distribution of movement velocities that were also modulated in relation to sensory salience. We propose a state-uncertainty based mode-switching heuristic that (1) reproduces the distinctive velocity distribution, (2) rationalizes modulation by sensory salience, and (3) outperforms the classic persistent excitation approach while using less energy. This mode-switching heuristic provides insights to purposeful exploratory behaviors in organisms as well as a framework for more efficient state estimation and control of robots.

animal behavior and cognition↗

bioRxiv2019

Variability in locomotor dynamics reveals the critical role of feedback in task control

Animals vary considerably in size, shape, and physiological features across individuals, but yet achieve behavioral performances that are virtually indistinguishable between conspecifics. We examined how animals compensate for morphophysiological variation by measuring the system dynamics of individual knifefish (Eigenmannia virescens) in a refuge tracking task. Kinematic measurements of Eigenmannia were used to generate individualized estimates of each fishs locomotor plant and controller revealing substantial variability between fish. To test the impact of this variability on behavioral performance, these models were used to perform simulated brain transplants--computationally swapping controllers and plants between individuals. We found that simulated closed-loop performance was robust to mismatch between plant and controller. This suggests that animals rely on feedback rather than precisely tuned neural controllers to compensate for morphophysiological variability.

neuroscience↗

bioRxiv2018

Closed-Loop Control of Active Sensing Movements Regulates Sensory Slip.

Active sensing involves the production of motor signals for the purpose of acquiring sensory information [1-3]. The most common form of active sensing, found across animal taxa and behaviors, involves the generation of movements--e.g. whisking [4-6], touching [7,8], sniffing [9,10], and eye movements [11]. Active-sensing movements profoundly affect the information carried by sensory feedback pathways [12-15] and are modulated by both top-down goals (e.g. measuring weight vs. texture [1,16]) and bottom-up stimuli (e.g. lights on/off [12]) but it remains unclear if and how these movements are controlled in relation to the ongoing feedback they generate. To investigate the control of movements for active sensing, we created an experimental apparatus for freely swimming weakly electric fish, Eigenmannia virescens, that modulates the gain of reafferent feedback by adjusting the position of a refuge based on real time videographic measurements of fish position. We discovered that fish robustly regulate sensory slip via closed-loop control of active-sensing movements. Specifically, as fish performed the task of maintaining position inside the refuge [17-22], they dramatically up- or down-regulated fore-aft active-sensing movements in relation to a 4-fold change of experimentally modulated reafferent gain. These changes in swimming movements served to maintain a constant magnitude of sensory slip. The magnitude of sensory slip depended on the presence or absence of visual cues. These results indicate that fish use two controllers: one that controls the acquisition of information by regulating feedback from active sensing movements, and another that maintains position in the refuge, a control structure that may be ubiquitous in animals [23,24].

animal behavior and cognition↗