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Browsing by Subject "default mode network"

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  • Partanen, Paula (2022)
    Research conducted on neural oscillations have paved the way to unravel the complexities of the brain dynamics underlying behavior and cognition. Neuronal oscillations characterize neuronal activity and processing at all spatial scales from neuronal microcircuits to large-scale brain dynamics and hence link cellular and molecular mechanisms to circuit dynamics underlying behavior. Large-scale oscillations and their inter-areal synchronization can be identified from in vivo electrophysiological data from animal models as well as from human magneto- and electroencephalography (M/EEG) data. Large-scale oscillation dynamics identified from human M/EEG data has been critical for resolving whole-brain oscillation dynamics view but is hindered by the indirectness of the measures. In contrast, rodent in vivo electrophysiology has been conventionally used to resolve oscillation dynamics locally in brain microcircuits. Although these measurements yield critical information of the mechanisms behind local oscillation dynamics, they are difficult to link with whole-brain dynamics view obtained from human M/EEG data. The newly established setup at the Neuroscience Center aims overcome these limitations and allows the measurements directly from the brain of awake head-fixed mice with over 1000 channel measuring simultaneously from both cortical and subcortical structures. This Master’s thesis project objective was to obtain proof-of-concept data to characterize oscillation dynamics during resting-state (RS) from awake behaving mice and to investigate whether these dynamics could be modulated by the manipulating E/I balance. More specifically, the current project aimed to investigate the oscillatory profile of the default-mode network (DMN) activity while manipulating the E/I balance with pharmacological mediums. Electrophysiological data was collected from RS activity from awake mice with two µECoG grids comprising together 512 channels and two laminar Neuropixel probes with each consisting 348 channels. The areas of interest were targeted to capture the DMN activity, covering anterior cingulate cortex (ACC), secondary motor cortex (M2), retrosplenial areas, visual cortical layers, pre- and infralimbic areas, hippocampal areas such as CA1 and dentate gyrus as well as lateral and posterior thalamic areas. The network activity was modulated with pharmacological mediums (sedative, stimulant, control) administered in low acute doses to see their effects on the oscillatory profile. Data from four mice were included into this Master’s thesis work and each mouse was recorded first for 30-minute daily baseline, following a 30-minute pharmacological measurement. This Master’s thesis included the data obtained from the µECoG data to the data analysis focusing on the large-scale cortical activity of the DMN. Power spectral density analysis showed a prominent alpha peak, also seen in humans, across condition with a mild decrease in volume in the stimulant condition. Synchronization was assessed with imaginary part of the phase locking value (iPLV), and the results showed increased synchronization in the stimulant condition and decreased in sedative condition in comparison to the control condition. The amplitude correlation coefficient showed also expected results in both pharmacological conditions, namely higher correlation in stimulant and lower in sedative. This project was able to obtain valuable information of the newly established in vivo electrophysiology setup and the results were in line with our expectations. This promising outcome solidifies the translational potential of the setup and its ability to serve as a translational counterpart in numerous research designs in health and disease.