It has long been established that the spinal cord is able to produce locomotor activity on its own. Despite extensive research identifying and describing the involvement of multiple spinal neuron populations that are part of the spinal locomotor circuit, the manner in which these different components act together to precisely control the rhythm and the pattern of activation of muscles during locomotion remains largely undetermined. We sought to shed light on how the components of spinal locomotor circuits interact to produce robust locomotion using a developmental approach in zebrafish larvae. We used electrophysiological techniques to observe how the rhythm generation mechanism developed while the fish was transitioning from an early form of swimming to a more mature swimming behaviour. In the process we were able to highlight fundamental changes in the organization of spinal locomotor circuits as its operation moves from a pacemaker-based architecture relying on intrinsic properties of neurons to a network oscillator-based architecture relying on synaptic connectivity to generate proper rhythm driving the fish tail beats. Additionally, we revealed that this transition occurred at different times along the spinal cord progressing in a caudorostral direction. By combining these experimental observations with already published insights we were able to propose models of spinal locomotor circuits reproducing the successive locomotor behaviours encountered through development. By incrementing supplementing the circuit model in a manner that reflected biological processes by which the nervous system maturates (neurogenesis, synaptic connectivity refinement and maturation of intrinsic properties) we mirrored the natural development of the spinal locomotor circuit. This series of successively constructed models permitted us to pinpoint possible roles of specific neural populations for swimming behaviour as well as eventual targets and mechanism of actions of neuromodulators (serotonin and dopamine). In the process, I further provided testable hypotheses for future inquiries. Overall, the experimental findings in combination with the modeling work are an important step forward in fully understanding how the spinal cord generates swimming movements in zebrafish.

Multiple taxonomies and typologies related to interactive music systems have been made, focusing on improvisation, music generation and software based music agents. These studies are comprehensive but general in their analysis of the generated output and music interaction, lacking an in-depth consideration of rhythm. Based on relevant literature on rhythm perception, principles of music performance and interactive music systems, this thesis conceptualizes rhythm according to seven rhythm dimensions, and surveys the state-of-theart of interactive music systems. It considers eighteen interactive music systems affording music input and rhythm generation. These systems are analyzed and categorized according to a rhythm taxonomy extending on a prior taxonomy related to interactive music systems. Analyzing the data reveals dimensions of rhythm that need deeper considerations, which, in comparison with the conclusions of the prior taxonomy, results in design considerations and evaluation methods for the design of rhythmic generation and rhythmic interaction of future interactive music systems. / Det existerar ett flertal taxonomier och typologier relaterade till interaktiva musiksystem, med fokus på improvisation, musikgenerering och mjukvarubaserade intelligenta musikagenter. Dessa studier är omfattande men allmänna i sin analys av musikinteraktionen och musiken som genereras av systemen och saknar en djupgående beaktande av rytm. Baserat på relevant litteratur om rytmuppfattning, principer för musikframförande och interaktiva musiksystem, konceptualiserar denna master uppsats rytm enligt sju rytmdimensioner och undersöker forskningsfältet för interaktiva musiksystem. Arton interaktiva musiksystem som möjliggör musikinmatning och rytmgenerering undersöks. Dessa system analyseras och kategoriseras enligt en rytm-taxonomi som bygger på en tidigare taxonomi relaterad till interaktiva musiksystem. Genom dataanalys framkommer det vilka rytmdimensioner som är i behov av ytterligare efterforskning, vilket i jämförelse med slutsatserna av den tidigare taxonomin resulterar i designöverväganden och utvärderingsmetoder för framtida utveckling av interaktiva musiksystem med fokus på rytm.