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  Computational Neurosciences Group R & D Activities

The goal of the CN group is to employ applied mathematics in an effort to understand how the brain works. It concentrates on the neural control of purposeful movements such as orienting the eyes and the head towards objects, reaching for them with an arm and grasping them with an appropriately configured hand. We collect experimental evidence concerning the movement related activation of brain areas, the behavioral relevance of the discharge patterns of the neurons they contain, the connections they establish with other neurons and the psychophysics of movements evoked when units of the relevant neural networks are activated or lesioned to constrain computational models of the brain and to test the consistency of the model and the epistemic adequacy of the data.

The CN group also participates in educational activities. In 1996-1998, the CN group helped organize the first three annual European Summer Schools in Computational Neuroscience addressing graduate, post-doctoral and junior faculty level scientists of various disciplines. The monthly stay in Crete of students and faculty of international renown from several European countries, the United States and Japan was supported through programs of the European Union, Japan and UNESCO. Also, researchers of the CN group supervise several MSc and PhD theses in the context of the Graduate Program in the Brain and Mind Sciences of the Universities of Crete and Athens.

Neurophysiology

Spike-trains are recorded from single units of animals trained to execute movements with effectors such as the eye, the head or the arm and analyzed to gain insight into the movement variables coded by single neurons or populations of neurons. Particular emphasis is placed on: 1) the discharge pattern of neurons responsible for the control of the line of sight in the cat. 2) motor and visuomotor properties of the neurons in the ventral premotor area (area F5) of the macaque monkey. 3) functional organization and neuronal properties of the dorsal premotor cortex (area F2) of the macaque monkey. 4) characterization of the synaptic interactions between neurons with the help of electrophysiological and pharmacological methods.

IACM contributions/interests
  • Discharge properties of neurons of the Interstitial Nucleus of Cajal
  • Discharge pattern of grasping related cortical neurons
  • Properties of eye movements evoked in response to microstimulation of the brain
Selected Publications
  1. Raos V, Umilta MA, Gallese V, Fogassi L. Functional properties of grasping-related neurons in the dorsal premotor area F2 of the macaque monkey. J Neurophysiol. 92(4):1990-2002, 2004.
  2. Raos V, Franchi G, Gallese V, Fogassi L. Somatotopic organization of the lateral part of area F2 (dorsal premotor cortex) of the macaque monkey. J Neurophysiol. 89(3):1503-18, 2003.
  3. Y. Dalezios, C.A. Scudder, S.M. Highstein and A.K. Moschovakis. Anatomy and physiology of the primate interstitial nucleus of Cajal. II. Discharge pattern of single efferent fibers. J. Neurophysiol. 80: 3100-3111, 1998.
  4. Raos V, Umilta MA, Murata A, Fogassi L, Gallese V. Functional properties of grasping-related neurons in the ventral premotor area F5 of the macaque monkey. J Neurophysiol. 95(2):709-29, 2006.
  5. Hadjidimitrakis K, Moschovakis AK, Dalezios Y, Grantyn A. (2007) Eye position modulates the electromyographic responses of neck muscles to electrical stimulation of the superior colliculus in the alert cat. Exp Brain Res 179, 1-16.

Brain Imaging

The quantitative, autoradiographic 14C-deoxyglucose technique, image analysis, and two-dimensional reconstruction of the local cerebral glucose utilization is used to investigate: 1) cortical cerebral pathways associated with voluntary arm-reaching movements of monkeys executing learned visuo-skeletomotor tasks and the visual or somatosensory guidance of the arm, 2) cortical and subcortical regions, related to saccadic eye-movements in the monkey brain and how they encode parameters of saccades (direction, amplitude, eye-position and trajectory), 3) cortical areas involved in execution of grasping movements either guided by sensory stimuli or memorized and the observation of actions performed by others.


IACM contributions/interests
  • Refutation of the moving wave hypothesis
  • Activation of saccade, grasping and reaching related cortical areas
  • Representation of spatial coordinates in neuronal manifolds
Selected Publications
  1. A.K. Moschovakis, G.G. Gregoriou, G. Ugolini, M. Doldan, W. Graf, W. Guldin, K. Hadzidimitrakis and H.E. Savaki. Oculomotor areas of the primate frontal lobes: A transneuronal transfer of rabies virus and [14C]-2-deoxyglucose functional imaging study. J. Neurosci. 24: 5726-5740, 2004.
  2. Raos V, Evangeliou MN, Savaki HE. Observation of action: grasping with the mind's hand. Neuroimage. 23(1):193-201, 2004.
  3. Gregoriou GG, Savaki HE. When vision guides movement: a functional imaging study of the monkey brain. Neuroimage. 19(3):959-67, 2003.
  4. A.K. Moschovakis, G.G. Gregoriou, and H.E. Savaki. Functional imaging of the primate superior colliculus during saccades to visual targets. Nature Neurosci. 4: 1026-1031, 2001.
  5. Gregoriou GG, Savaki HE. The intraparietal cortex: subregions involved in fixation, saccades, and in the visual and somatosensory guidance of reaching. J Cereb Blood Flow Metab. 21(6):671-82, 2001.
  6. Dalezios Y, Gregoriou GG, Savaki HE Metabolic activity patterns in the monkey visual cortex as revealed by spectral analysis. J Cereb Blood Flow Metab 19, 401-416, 1999.
  7. Evangeliou MN, Raos V, Galletti C, Savaki HE. Functional imaging of the parietal cortex during action execution and observation. Cereb. Cortex in press, 2008.
  8. Raos V, Evangeliou MN, Savaki HE. Mental simulation of action in the service of action perception. J Neurosci. 27(46):12675-83, 2007.
  9. Bakola S, Gregoriou GG, Moschovakis AK, Raos V, Savaki HE. Saccade-related information in the superior temporal motion complex: quantitative functional mapping in the monkey. J Neurosci. 27(9):2224-9, 2007.
  10. Bakola S, Gregoriou GG, Moschovakis AK, Savaki HE. Functional imaging of the intraparietal cortex during saccades to visual and memorized targets. Neuroimage 31(4):1637-49, 2006.
  11. Gregoriou GG, Luppino G, Matelli M, Savaki HE. Frontal cortical areas of the monkey brain engaged in reaching behavior: a (14)C-deoxyglucose imaging study. Neuroimage 27(2):442-64, 2005.

Neuroanatomy

Immunohistochemistry, light/electron microscopy and extracellular tracer injections are used to study the synaptic organization of neural systems in the mammalian brain including cortical and subcortical oculomotor areas/nuclei, the neocortex and hippocampus.

IACM contributions/interests
  • Connections of saccade related cortical areas
  • Anatomy of the Interstitial Nucleus of Cajal
  • Anatomical substrate of the spatio-temporal transformation
  • Structure of the saccadic system
  • Study of cortical interneurons
Selected Publications
  1. A.K. Moschovakis, G.G. Gregoriou, G. Ugolini, M. Doldan, W. Graf, W. Guldin, K. Hadzidimitrakis and H.E. Savaki. Oculomotor areas of the primate frontal lobes: A transneuronal transfer of rabies virus and [14C]-2-deoxyglucose functional imaging study. J. Neurosci. 24: 5726-5740, 2004.
  2. A. Grantyn, A. Brandi, D. Dubayle, W. Graf, G. Ugolini K. Hadjidimitrakis and A.K. Moschovakis. Density gradients of trans-synaptically labeled collicular neurons after injections of rabies virus in the lateral rectus muscle of the rhesus monkey. J. Comp. Neurol. 451: 346-361, 2002.
  3. A.K. Moschovakis, T. Kitama, Y. Dalezios, Petit, J., A. M. Brandi and A.A. Grantyn. An anatomical substrate for the spatiotemporal transformation. J. Neurosci. 18: 10219-10229, 1998.
  4. Moschovakis, A. K., Scudder, C. A., and Highstein, S. M. The microscopic anatomy and physiology of the mammalian saccadic system. Progr. Neurobiol. 50: 133-254, 1996.
  5. Kato R, Grantyn A, Dalezios Y, Moschovakis AK. (2006) The local loop of the saccadic system closes downstream of the superior colliculus. Neuroscience 143, 319-337.
  6. Jinno S, Klausberger T, Marton LF, Dalezios Y, Roberts JD, Fuentealba P, Bushong EA, Henze D, Buzsaki G, Somogyi P (2007) Neuronal diversity in GABAergic long-range projections from the hippocampus. J Neurosci 27, 8790-8804.
  7. Baude A, Bleasdale C, Dalezios Y, Somogyi P, Klausberger T (2007) Immunoreactivity for the GABAA receptor α1 subunit, somatostatin and connexin36 distinguishes axo-axonic, basket and bistratified interneurons of the rat hippocampus. Cereb. Cortex 17, 2094-2107.

Stochastic Signal Processing

We use mathematical/computer modelling, develop techniques to analyse neural signals and systems and carry out electrophysiological experiments to study the activity of populations of neurons with particular emphasis on rhythms and population synchrony underlying neural mechanisms responsible for the generation of movement and respiration.

IACM contributions/interests
  • Neural control of muscle contractions in posture and movement.
  • Generation of physiological and pathological muscle tremors in steady and time-varying contractions
  • High-frequency oscillations characteristic of the neural networks of the respiratory rhythm generator
Selected Publications
  1. Christakos CN, Erimaki S, and Moschovakis AK. Complicating factors in the analysis of neural population synchrony and in understanding the formation of aggregate rhythms. Applications to tremor genesis. New Orleans, LA: Society for Neuroscience, 2003.
  2. Erimaki S and Christakos CN. Occurrence of widespread motor-unit firing correlations in muscle contractions: their role in the generation of tremor and time-varying voluntary force. J Neurophysiol 82: 2839-2846, 1999.
  3. Christakos CN. On the detection and measurement of synchrony in large neural populations by coherence analysis. J Neurophysiol 78: 3453-3459, 1997.
  4. Erimaki S, Christakos CN. Coherent motor unit rhythms in the 6-10 Hz range during time-varying voluntary muscle contractions: neural mechanism and relation to rhythmical motor control. J Neurophysiol 99: 473, 2008.
  5. Erimaki S, Anagnostou E, Anastasopoulos D, Christakos CN. Motor unit firing properties and rhythmical correlations in parkinsonian postural tremor. J. Neurol. 254(s3): 64, 2007.
  6. Christakos CN, Papadimitriou NA, Erimaki S. Parallel neuronal mechanisms underlying physiological force tremor in steady muscle contractions of humans. J Neurophysiol. 95: 53, 2006.
  7. Cohen MI, See W, Yu Q, Huang W, Marchenko V, Granada A, Christakos CN. Integer-ratio synchronization between different neural rhythms in respiratory and sympathetic networks. Society for Neuroscience (Washington DC), 2005.

Brain Modeling

Computer simulations consistent with known anatomy, physiology, neurology and psychophysics are developed to understand the neural control of purposeful action.

IACM contributions/interests
  • Neural Integrator
  • Burst Generator
  • Superior colliculus
Selected Publications
  1. S. Sklavos and A.K. Moschovakis. Neural network simulations of the primate oculomotor system. IV. A distributed bilateral stochastic model of the neural integrator of the vertical saccadic system. Biol. Cybern. 86: 97-109, 2002.
  2. A. Bozis and A.K. Moschovakis. Neural network simulations of the primate oculomotor system. III. A one-dimensional one-directional model of the superior colliculus. Biol. Cybern. 79: 215-230, 1998.
  3. A.K. Moschovakis, Y. Dalezios, J. Petit and A.A. Grantyn. New mechanism that accounts for position sensitivity of saccades evoked in response to electrical stimulation of superior colliculus. J. Neurophysiol. 80: 3373-3379, 1998.
  4. A.K. Moschovakis. Superior colliculus and eye movement control. Curr. Opin, Neurobiol. 6: 811-816, 1996.
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