Hervé Emile Louis Thevenon disputerer for ph.d.-graden i helsevitenskap og vil offentlig forsvare avhandlingen:
“What are the necessary characteristics of the nervous system to exhibit habituation?”
Kort sammendrag av avhandlingen:
This dissertation formalises an ecology driven algorithmic model of the nervous system in order to investigate the bare minimum mechanisms required for a nervous system to exhibit habituation and sensitisation.
With reference to the informal body of principles known as the neuron doctrine, the model (i) shifts the demarcation points from the synapses to the soma, (ii) removes synaptic plasticity, and (iii) emphasises on the duration of the transit of the signals between consecutive demarcation points.
The model is descriptive of observations made in comparative physiology, electrophysiology, and histology.
The model is generative of connectomes that exhibit several innate behaviours when embodied in an environment providing ambiguous stimuli. Accordingly to the principle of survival value, some of the observed innate behaviours are shown to habituate and sensitise when ecological conditions are varied from normal. The model also satisfies the animal-to-animal variability principle, and the multiple observations that abnormal neurogenesis incurs ataxia. Effectively this work demonstrates that the interactions of the triumvirate Environment, Connectome, Behaviours can be addressed as a whole instead of in pairs.
In terms of predictions, the model vindicates the state system hypothesis for sensitisation, and rejects the hypothesis that threshold and peak values are variables for the connectomes’ state or the expression of behaviours, as well as the synaptic theory for sensitisation and habituation.
From a general perspective the model shows that flexible behaviours, habituation, and sensitisation can be expressed by a non trivial structure of invariant nodes.
The model is intrinsically simple and can be expressed as a dynamical system. Continued experimentation with the model in various environmental settings should yield additional postulates that may assist with the mathematical analysis of the system and provide further explanations as to the workings of nervous systems and nerve nets.
Finally, the model’s passive design of the neuron is ground to abandon the adage “the neuron is the computational unit of the brain”.
(Avhandlingen er tilgjengelig for utlån hos Seksjon for forskningstjenester frem til disputasdato)
Veiledere
Hovedveileder førsteamanuensis Gerit Pfuhl, associate professor at UiT Norges arktiske universitet
Biveileder førsteamanuensis Ian Welch, associate professor at Victoria University of Wellington, New Zealand
Bedømmelseskomiteen
Professor Bertrand Jouve, The National Center for Scientific Research, Frankrike – 1. opponent
Førsteamanuensis Anca Doloc-Mihu, Emory University, USA – 2. opponent
Førsteamanuensis Eelke Snoeren, UiT Norges arktiske universitet – leder av komité
Disputasleder
Professor Tove Irene Dahl, Institutt for psykologi, Det helsevitenskapelige fakultet, UiT Norges arktiske universitet
Prøveforelesning over oppgitt emne holdes kl. 10.15, samme sted: “Computational modeling in neuroscience: how to represent complexity”