Adaptive behaviour and learning in slime moulds: the role of oscillations

Abstract

The slime mould Physarum polycephalum, an aneural organism, uses information from previous experiences to adjust its behaviour, but the mechanisms by which this is accomplished remain unknown. This article examines the possible role of oscillations in learning and memory in slime moulds. Slime moulds share surprising similarities with the network of synaptic connections in animal brains. First, their topology derives from a network of interconnected, vein-like tubes in which signalling molecules are transported. Second, network motility, which generates slime mould behaviour, is driven by distinct oscillations that organize into spatio-temporal wave patterns. Likewise, neural activity in the brain is organized in a variety of oscillations characterized by different frequencies. Interestingly, the oscillating networks of slime moulds are not precursors of nervous systems but, rather, an alternative architecture. Here, we argue that comparable information-processing operations can be realized on different architectures sharing similar oscillatory properties. After describing learning abilities and oscillatory activities of P. polycephalum, we explore the relation between network oscillations and learning, and evaluate the organism's global architecture with respect to information-processing potential. We hypothesize that, as in the brain, modulation of spontaneous oscillations may sustain learning in slime mould. This article is part of the theme issue 'Basal cognition: conceptual tools and the view from the single cell'.

Keywords: Physarum polycephalum; cognition; learning; oscillations; slime mould; synchronization.

Figure 1.

These pictures illustrate (a) a macroplasmodium, the vegetative phase of P. polycephalum, (b) a sclerotium, the dormant stage, (c) a slime mould making a decision between different food sources varying in quality, (d) a vein network, (e) a magnified vein and (f) nuclei stained with DAPI within the plasmodium.

Figure 2.

Oscillations, coupling and synchronization: (a) the (instantaneous) phase indicates the state of an oscillator, (b) the change of phase is driven by the natural frequency and coupling, (c) coupling can be global or local, mediated by a network topology, (d–f) states of a random planar network of Kuramoto oscillators (see electronic supplementary material, movies S3 and S4), (d) desynchronization, (e) dynamical wave synchronization (local coupling) and (f) full synchronization (global coupling).