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Modern optical in vivo methods in neurophysiological research
Tomáška, Filip ; Novák, Ondřej (advisor) ; Elsnicová, Barbara (referee)
Accurate visualization of structures and events at subcellular level is one of the major challenges of current neuroscience. Optical methods based on fluorescence imaging were optimized to record and control neural activity, thus presenting a powerful approach complementary to historically dominant electrophysiological techniques. The employment of two-photon excitation enabled in vivo imaging of neurons up to 1 mm from the sample surface without causing significant photodamage. The application of methods of molecular biology has yielded protein-based genetically targetable indicators of neural activity, possessing performance comparable to the traditional organic dyes. Moreover, heterologous expression of microbial opsins proved capable of light-induced neural excitation or silencing in a single-component manner. The combination of these optogenetic tools offers two-way control over neuronal populations with single cell resolution. If coupled with calcium or voltage fluorescent indicators and transgenic animal models, such systems represent a non- invasive, all-optical tool for simultaneous control and imaging of specific neuronal subtypes. Its application supported by electrical recordings may finally provide the data necessary for the uncovering of fundamental principles of neural functioning.
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The role of inhibitory interneurons in encoding of complex sounds by the auditory cortex of mouse
Tomáška, Filip ; Tureček, Rostislav (advisor) ; Kelemen, Eduard (referee)
Recent findings suggest, that perception of acoustic stimuli in the mouse auditory cortex relies on categorization of object-based representations. Local neuronal populations in L2/3 of the mouse auditory cortex reportedly exhibit a limited number (1-3) of stable modes of response, each possibly evoked by multiple complex sounds of variable acoustic features. Stimulation using linear intensity mixing of sounds evoking different response modes revealed an attractor-like dynamic of the underlying representation. These modes of response were hypothesized to represent the neural correlate of perceptual categorization. We have developed an experimental protocol enabling chronic two-photon imaging of the previously described population coding under awake conditions. Using this protocol we acquired data suggesting that the pattern of population activity underlying a mode of response, is stable during a week-long timeframe. We have also recorded the neural activity of a local subpopulation of somatostatin-positive inhibitory interneurons (SST+ INs) during abrupt changes in cortical representation. Our preliminary results suggest that local SST+ INs exhibit maximal firing when the neural correlate of a mode of response is exhibited by the surrounding population of principal cells. In addition, we observed a...
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Modern optical in vivo methods in neurophysiological research
Tomáška, Filip ; Novák, Ondřej (advisor) ; Elsnicová, Barbara (referee)
Accurate visualization of structures and events at subcellular level is one of the major challenges of current neuroscience. Optical methods based on fluorescence imaging were optimized to record and control neural activity, thus presenting a powerful approach complementary to historically dominant electrophysiological techniques. The employment of two-photon excitation enabled in vivo imaging of neurons up to 1 mm from the sample surface without causing significant photodamage. The application of methods of molecular biology has yielded protein-based genetically targetable indicators of neural activity, possessing performance comparable to the traditional organic dyes. Moreover, heterologous expression of microbial opsins proved capable of light-induced neural excitation or silencing in a single-component manner. The combination of these optogenetic tools offers two-way control over neuronal populations with single cell resolution. If coupled with calcium or voltage fluorescent indicators and transgenic animal models, such systems represent a non- invasive, all-optical tool for simultaneous control and imaging of specific neuronal subtypes. Its application supported by electrical recordings may finally provide the data necessary for the uncovering of fundamental principles of neural functioning.
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