Research Group for Cerebral Cortical Modularity
- László Négyessy, PhD (personal web page: http://cneuro.rmki.kfki.hu/people/negyessy) – tel. ext.: 53657
- Orsolya Kántor, MD, PhD – tel. ext.: 53657
- Mária Ashaber (biologist) tel. ext.: 53712
- Emese Pálfi (biologist) tel. ext.: 53712
- Róbert Tóth
- Alexandra Varga
- Györgyné Vidra – tel. ext.: 53656
The continuous sheet of the cerebral cortex, the so called neocortex or isocortex, is in fact a complex network of structurally and functionally heterogeneous areas. The unique characteristic of this network is that it is formed by populations of closely spaced neurons with convergent or overlapping afferents. Thereby connections appear as modular or patch-like pattern both within and between the areas. Similarly, cortical activations are spatiotemporally delineated forming a distributed modular architecture in the functioning brain. As such, modular organization represents the transition from the micro circuits to the large scale network. In some areas the modular connectional architecture corresponds to the known columnar cortical organization, such that certain kinds of columns are selectively connected to each other. However, in most of the cases connectional preferences of the neuronal populations are not known. A major obstacle in understanding the functioning of the cerebral cortex is that the modular connectional architecture is largely unexplored.
• We study the neuronal connectivity of functionally identified modules of the primate sensorimotor cortex. In this project we use neuroanatomical tracing aided by optical imaging and electrophysiological mapping. The function of such somatosensory and motor cortical modular circuitry is studied by examining the synaptic organization of inhibitory and excitatory connections by way of confocal, and electron microscopy in addition to electrophysiology. This project also aimed at understanding the neural mechanisms of tactile functions and fine finger movements, which, in the future, can help developing bionic devices including prosthetics to disabled persons.
• We also apply graph theory to model the modular cortical connectivity at a mesoscopic level organization. At the long term we also aim to understand the dynamics of such model network by including the results of our ongoing studies on the analysis of neuronal behavior in alert, behaving monkeys. We approach neuronal behavior by analyzing inter spike interval (ISI) distributions using probability theory. The goal of these analyses is to find generative mechanisms, which can reproduce the behavior of neurons embedded into the neuronal network of the cerebral cortex.
• We also study how tissue non-specific alkaline phosphatese (TNAP) modulates cortical functioning. TNAP is a ubiquitous ectoenzyme with wide substrate specificity, which exhibits highly specific laminar localization in the cerebral cortex with a unique pattern in the human. Cleaving phosphate groups this enzyme can potentially regulate different neurotransmitter systems depended on the so called B6-enzymes in addition to purinergic transmission. Given the localization and enzymatic functions we assume that TNAP is a key player in balancing cortical excitation and inhibition. However, the neural role of TNAP is largely unexplored. Patients of hypophosphatasia, resulted by mutation of the gene encoding TNAP, develop severe epileptic seizures. We combine enzymhistochemitry, immunohistochemistry both at light and electron microscopic levels, confocal microscopy, molecular biology and electrophysiology to understand the role of this enzyme in regulating the function of circuitries of the cerebral cortex under normal and diseased conditions. In this project, we also use the retina as a well explored and relatively simple model system of neural circuitries.