Public defence in Biomedical Engineering, M.Sc. Timo Nurmi

Processing of the position and movement sense in the brain was studied using neuroimaging and evoked movements of the limbs.

Public defence from the School of Science, Department of Neuroscience and Biomedical Engineering.
Brain prented from the above. The picture also contains two activation clusters in the somatosensory cortex.
Copyright Paula Ikonen

Title of the thesis: Neuroimaging cortical proprioceptive processing with evoked movements

Doctoral student: Timo Nurmi
Opponent: Doctor Peter Bandettini, National Institute of Mental Health, USA
Custos: Professor Lauri Parkkonen, Aalto University School of Science, Department of Neuroscience and Biomedical Engineering

Human movement is based on electrochemical signaling from the brain via the spinal cord and peripheral nervous system to the muscles. These signals, known as motor efference cause muscles to contract and relax in a coordinated manner in order to execute desired movement patterns appropriately. The brain basis of motor control is still unclear and therefore it is crucial to study it. Often overlooked aspect of motor control, however, is feedback signaling from the body (its muscles, tendons and joints) via the spinal cord back to the brain, called proprioceptive afference. The proprioceptive sense informs the brain about the internal state of the body such as body position, movement and forces produced or acting on it. Thus, proprioception is the basis of motor control and enables motor learning and adaptation.

Proprioception is always active enabling the brain to plan, control and correct movements. Several motor disorders, such as cerebral palsy (CP), are often associated with proprioceptive deficits that are suggested to contribute to the behavioral motor symptoms in these disorders. However, the brain basis of the motor impairments and the effect of the impaired proprioception on motor control has remained largely unknown

In this thesis, cortical proprioceptive processing in the cortex was examined using neuroimaging in conjunction with proprioceptive stimulation (i.e. movements) of the index fingers and ankles using computer-controlled devices. The neuroimaging methods consisted of functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG). Neuroimaging data were compared to the results of behavioral sensorimotor performance tests. The effect of proprioceptive stimulation parameters, such as movement frequency and range, on the brain responses were studied. The brain responses to the proprioceptive stimuli were also compared between adolescents with and without CP, and it was clarified, how these responses were associated with behavioral sensorimotor performance.

The studies in the thesis resolved the optimal stimulation parameters maximizing strength of the brain responses. Moreover, the cortical proprioceptive processing differed between the adolescents with and without CP, and these differences were associated with behavioral sensorimotor performance. Our studies demonstrated that using proprioceptive stimulator evoking precise joint movements is a feasible way to study and quantify the proprioceptive processing in the brain.

Key words: evoked movements, somatosensory cortex, sensorimotor cortex, cerebral palsy

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