Decision – Making in C. Elegans
There are several ways to learn more about the processes that underlie decision-making processes in humans. One of the approaches is to study simpler organisms and gradually extend this knowledge to more complex ones. C. Elegans is one of such model organisms. It has a well-mapped connectome and genome. In this study we focus on the processes that may lie behind decision-making in C. Elegans. We look specifically at lateral inhibition and synchronisation, changes that happen in the neural network after experience and speculate how these mechanisms contribute towards simple forms of decision-making. Decision – making is an example of a complex psychological process which can be researched on an elementary level. Decision – making has been researched from different angles, be it a normative, descriptive or prescriptive one. It is tightly bound with other cognitive processes like memory, planning, problem solving and social cognition (Plous, 1993). Patients suffering from alexithymia (Bechara et al., 2000) show tight interconnection between decision making and emotional centres of brain. All this makes the research of decision - making processes a complex one. Ethical aspects of decision - making are also present here. It is impossible to do such neuro-psychological studies on humans as is possible on animals or in computer models. So far, research in the area of neural and neurochemical basis of decision-making concentrated at the study of behavioural choice. Faumont, Lindsay and Lockery (2012) identified mechanisms that allow C. Elegans to make a behavioural decision based on previous experience. First, changes in synaptic strengths are observed after an animal is conditioned to avoid stimuli that were neutral or attractive before. Neural circuits are reconfigured in such a way that a signal from a stimulus does not travel to motor neurons responsible for forward locomotion but is redirected toward neurons responsible for avoidance motor response. Second mechanism is based on changes in the basal activity of interneuron and coupled sensory neuron. Whether an animal responds to increases in pheromone concentrations is responsible for its behavioural choices regarding being attracted or repelled from other animals and thus influencing its social behaviour. Sensory neuron receptive to pheromones is coupled with a hub neuron by an electrical synapse. The behaviour of this synapse is influenced by the inflow of neuropeptides caused by changes in the environment of the worm. The state of the synapse then either allows or blocks sensory neuron from activating interneuron further down the neural network and thus enhancing or blocking the movement towards the source of the pheromone. In both mechanisms peptide signalling seems to play a role. It may be the case that concentrations of various neuropeptides cause variations in behavioural choice of the animal.
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