The PhD in Medical Sciences:
The University of Nicosia Medical School offers the degree PhD in Medical Sciences. The degree is awarded to students who successfully complete an independent research programme that breaks new ground in the chosen field of study. The PhD programme aspires to empower students to become independent researchers, thus advancing innovation and development.
The Research Project:
We are currently inviting application through a competitive process for high calibre candidates to apply for the below PhD Project in the field of Neuroscience. The successful candidate will enrol on the PhD programme in Medical Sciences and will work under the Supervision of Dr Avgis Hadjipapas, Professor of Neuroscience and Research Methods at the University of Nicosia Medical School. The project is based on an international collaboration between the University of Nicosia Medical School, and Maastricht University (MU).
Title of research project: Laminar interactions and information flow in primary visual cortex.
Understanding how neuronal networks in the brain communicate in order to perform various computations is a major goal of systems neuroscience today. Networks in the cortex are exquisitely organized in layers and form well defined and repeating microcircuits (Gilbert and Wiesel, 1983). The anatomical connectivity between layers and the single cell behaviour in these layers have been studied in the past leading to important insights into the workings of the cortical circuit (reviewed in (Bastos et al., 2012)). At the same time, it has become clear that neurons engage in synchronous oscillations in the gamma band (20-90Hz). These have been observed in all laminar compartments of the cortex (Maier et al., 2010; Roberts et al., 2013; Xing et al., 2012).
How are these oscillations to be reconciled with the laminar structure of the cortical microcircuits? Does the presence of oscillations constrain the way that layers communicate with each other? What is the means of communication between layers in the presence of these oscillations? These are important open questions that this project will help address. The main aim of the project will be to characterize interactions between different laminar compartments, and the observed frequencies of the oscillations expressed in these compartments. This search for interactions is theoretically- motivated; the main argument is that laminar compartments can be viewed as weakly coupled oscillators and therefore powerful concepts of synchronization theory apply. Depending on the relationship between the expressed oscillation frequencies in each compartment and their anatomical coupling, synchronization can be employed to derive theoretical predictions(Hadjipapas et al., 2009; Lowet et al., 2017, 2015). Among other possibilities, it is possible that directed interactions between laminar compartments may ensue, resulting in a directed flow of information across the cortical circuit (Ferro et al., 2021; van Kerkoerle et al., 2014). In directed interactions, frequency differences between laminar compartments are important because these, shape the ensuing synchronization process (Hadjipapas et al., 2009; Lowet et al., 2017, 2015). Directed interactions may be important to prioritize feedforward (bottom-up) influences from feedback influences (top down) when these are required by the stimulus or task at hand.
In this project interactions across laminar compartments will be characterized and the information flow between compartments will be examined as a function of stimulus luminance contrast (bottom up input) and attention (top down input). This will be pursued in already existing data acquired by laminar probes in the awake behaving monkey, provided by the Maastricht collaboration. This data allows for the characterization of oscillations across laminar compartments. A computational neuronal model for communication between the layers will also be produced , which will be constrained by the data similar to the approach taken in (Zachariou et al., 2021). This model will aid data interpretations and produce further testable predictions.
In sum, this project aims to help reconcile oscillatory activity with appropriate/adaptive information flow in the cortical circuit by producing a framework for studying the interactions within the fundamental cortical circuit including a computational model. Successful candidates will further benefit from interacting with an international consortium of neuroscientists throughout the duration of the project.
Bastos, A.M., Usrey, W.M., Adams, R.A., Mangun, G.R., Fries, P., Friston, K.J., 2012. Canonical Microcircuits for Predictive Coding. Neuron 76, 695–711. https://doi.org/10.1016/j.neuron.2012.10.038
Ferro, D., Kempen, J. van, Boyd, M., Panzeri, S., Thiele, A., 2021. Directed information exchange between cortical layers in macaque V1 and V4 and its modulation by selective attention. Proc. Natl. Acad. Sci. 118. https://doi.org/10.1073/PNAS.2022097118
Gilbert, C.D., Wiesel, T.N., 1983. Functional Organization of the Visual Cortex. Prog. Brain Res. 58, 209–218. https://doi.org/10.1016/S0079-6123 (08)60022-9
Hadjipapas, A, Casagrande, E., Nevado, A., Barnes, G.R., Green, G., Holliday, I.E., 2009. Can we observe collective neuronal activity from macroscopic aggregate signals? Neuroimage 44, 1290–1303.
Lowet, E., Roberts, M., Hadjipapas, A., Peter, A., van der Eerden, J., De Weerd, P., 2015. Input-Dependent Frequency Modulation of Cortical Gamma Oscillations Shapes Spatial Synchronization and Enables Phase Coding. PLOS Comput. Biol. 11, e1004072. https://doi.org/10.1371/journal.pcbi.1004072
Lowet, E., Roberts, M.J., Peter, A., Gips, B., Weerd, P. De, 2017. A quantitative theory of gamma synchronization in macaque V1 1–44.
Maier, A., Adams, G.K., Aura, C., Leopold, D. a, 2010. Distinct superficial and deep laminar domains of activity in the visual cortex during rest and stimulation. Front. Syst. Neurosci. 4, 1–11. https://doi.org/10.3389/fnsys.2010.00031
Roberts, M.J., Lowet, E., Brunet, N.M., Ter Wal, M., Tiesinga, P., Fries, P., De Weerd, P., 2013. Robust gamma coherence between macaque V1 and V2 by dynamic frequency matching. Neuron 78, 523–36. https://doi.org/10.1016/j.neuron.2013.03.003
van Kerkoerle, T., Self, M.W., Dagnino, B., Gariel-Mathis, M.A., Poort, J., van der Togt, C., Roelfsema, P.R., 2014. Alpha and gamma oscillations characterize feedback and feedforward processing in monkey visual cortex. Proc Natl Acad Sci U S A 111, 14332–14341. https://doi.org/10.1073/pnas.1402773111
Xing, D., Yeh, C.-I., Burns, S., Shapley, R.M., 2012. Laminar analysis of visually evoked activity in the primary visual cortex. Proc. Natl. Acad. Sci. U. S. A. 109, 13871–6. https://doi.org/10.1073/pnas.1201478109
Zachariou, M., Roberts, M., Lowet, E., De Weerd, P., Hadjipapas, A., 2021. Empirically constrained network models for contrast-dependent modulation of gamma rhythm in V1. Neuroimage 229, 117748. https://doi.org/10.1016/j.neuroimage.2021.117748
The tuition fees are €13,500 in total for the first 3 years. For each additional academic year, tuition is €1,500 per year.
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