Biology subjects

Florian Pieper

Publications and source records attributed to Florian Pieper.

3 recordsLinked to original sources

bioRxiv2016

Intrinsic functional connectivity resembles cortical architecture at various levels of isoflurane anesthesia

Cortical activity patterns change in different depths of general anesthesia. Here we investigate the associated network level changes of functional connectivity. We recorded ongoing electrocorticographic (ECoG) activity from the ferret temporo-parieto-occipital cortex under various levels of isoflurane and determined the functional connectivity by computing amplitude envelope correlations. Through hierarchical clustering, we derived typical connectivity patterns corresponding to light, intermediate and deep anesthesia. Generally, amplitude correlation strength increased strongly with depth of anesthesia across all cortical areas and frequency bands. This was accompanied by the emergence of burstsuppression activity in the ECoG signal and a change of the spectrum of the amplitude envelope. Normalizing the functional connectivity patterns showed that the topographical structure remained similar across depths of anesthesia, resembling the functional association of the underlying cortical areas. Thus, while strength and temporal properties of amplitude co-modulation vary depending on the activity of local neural circuits, their network-level interaction pattern is presumably most strongly determined by the underlying structural connectivity.

Neuroscience↗

bioRxiv2015

Intrinsic coupling modes reveal the functional architecture of cortico-tectal networks

In the absence of sensory stimulation or motor output, the brain exhibits complex spatiotemporal patterns of intrinsically generated neural activity. However, little is known about how such patterns of activity are correlated between cortical and subcortical brain areas. Here, we investigate the large-scale correlation structure of ongoing cortical and superior colliculus (SC) activity across multiple spatial and temporal scales. Cortico-tectal interaction was characterized by correlated fluctuations in the amplitude of delta, spindle, low gamma and high frequency oscillations (> 100 Hz). Of these identified coupling modes, topographical patterns of high frequency coupling were the most consistent with anatomical connectivity, and reflected synchronized spiking in cortico-tectal networks. Ongoing high frequency cortico-tectal coupling was temporally governed by the phase of slow cortical oscillations. Collectively, our findings show that cortico-tectal networks can be resolved through the correlation structure of ongoing neural activity, and demonstrate the rich information conveyed by high frequency electrocorticographic signals.

Neuroscience↗

bioRxiv2015

Crossmodal integration improves sensory detection thresholds in the ferret

During the last two decades ferrets (Mustela putorius) have been established as a highly efficient animal model in different fields in neuroscience. Here we asked whether ferrets integrate sensory information according to the same principles established for other species. Since only few methods and protocols are available for behaving ferrets we developed a head-free, body-restrained approach allowing a standardized stimulation position and the utilization of the ferrets natural response behavior. We established a behavioral paradigm to test audiovisual integration in the ferret. Animals had to detect a brief auditory and/or visual stimulus presented either left or right from their midline. We first determined detection thresholds for auditory amplitude and visual contrast. In a second step, we combined both modalities and compared psychometric fits and the reaction times between all conditions. We employed Maximum Likelihood Estimation (MLE) to model bimodal psychometric curves and to investigate whether ferrets integrate modalities in an optimal manner. Furthermore, to test for a redundant signal effect we pooled the reaction times of all animals to calculate a race model. We observed that bimodal detection thresholds were reduced and reaction times were faster in the bimodal compared to unimodal conditions. The race model and MLE modeling showed that ferrets integrate modalities in a statistically optimal fashion. Taken together, the data indicate that principles of multisensory integration previously demonstrated in other species also apply to crossmodal processing in the ferret.

Neuroscience↗