Most of life is brainless and the vast majority of organisms on Earth lack neurons altogether. These organisms include plants, fungi, and bacteria (both non-pathogenic and disease-causing types), who all must cope with the same problem as humans - make the best choices in an ever changing world or risk dying - but without the help of a brain or even a simple nervous system. This project will explore the decision-making abilities of one of these neuron-less organisms, the slime mold Physarum polycephalum. Of particular interest is (1) how P. polycephalum integrates noisy and sometimes contradictory information when selecting a food source; and (2) the role of its past experiences (e.g. the resources it has previously visited) on the outcome of its future choices. Because P. polycephalum is a macroscopic unicellular organism, it can be easily manipulated and observed, while retaining similar characteristics to other neuron-less, microscopic creatures. It is therefore a perfect model system to understand how most living beings integrate complex and dynamical information. The project will train 2 graduate students and at least 15 undergraduate and high school students in integrative research at one of the most diverse campuses in the US (Rutgers-Newark and NJIT, both located in Newark, NJ) and at a collaborating lab in Sydney, Australia. "Hands-on", open sourced demonstration kits for K-12 classes to experiment with slime mold locomotion and decision-making will be developed to encourage the study of cognitive processes in neuron-less organisms and other non-traditional model organisms.
The proposed project will set up a comprehensive experimental and theoretical framework that can be used beyond the scope of this project to study decision-making in other neuron-less organisms and to establish comparisons with brained animals, thereby advancing our comprehension of the emergence of cognitive processes in biological systems. Cell micromanipulation and calcium imaging combined with analytical tools from neurophysiology and statistical physics will be used to first investigate the role of contractile oscillations of P. polycephalum's cellular plasma membrane in its decision-making process. In particular, the transfer and integration of information from different stimuli will be examined. The efficiency of the slime mold decision-making mechanism when the available information is noisy or contradictory will also be tested. Finally, whether the slime mold's natural positive geotaxis (motion in the direction of gravity) can be conditioned (i.e., reversed here) if food is always present uphill will be determined. This would indicate that the slime mold is capable of spatial associative learning (a first in the slime mold), and that its decision-making process is capable of adapting to the characteristics of the environment through which it moves. All methods, results and software developed during this project will be made freely available on a repository hosted by the Open Science Framework.
