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A DYNAMIC APPROACH TO BRAIN CONNECTIVITY


Giorgio M Innocenti1 and Roberto Caminiti2

1 Department of Neuroscience Karolinska Institutet, Stockholm, Sweden.
2 Department of Physiology and Pharmacology, University of Rome SAPIENZA. Rome, Italy.

Giorgio M. Innocenti1*
  • 1 Karolinska Institutet, Neuroscience, Sweden

Over the last 40 years histological methods based on axonal transport of tracers, have generated an impressive amount of connectivity data in experimental animals, revolutionizing concepts of brain organization. Impressive as they are those studies provide an essentially static image of brain connectivity. A more dynamic view of connectivity is encouraged by the revived realization, that neural connections are implemented by axons of different diameter, hence conducting impulses at different speeds. Speed and length of axons generate conduction delays, which together with parameters of postsynaptic integration provide the time frame for brain dynamics. This new approach is generating new images on brain connectivity based on graph theory but which significantly upgrade what has been thus far available (Fig.1).

The results are obtained by injecting an axonally transported anterograde tracer (BDA) into several cortical areas of the macaque and then measuring the diameter of axons to the various targets, and the length of the axonal trajectories using the Neurolucida and the Neurolucida Explorer software (MBF Biosciences, Williston, VT, USA). From these parameters the conduction velocity of axons and the delays they generate from the site of origin to the termination are computed. The histological data on pathway lengths have been confirmed by DTI approaches in monkey and human. Computed delays are compatible with the available electrophysiological data, but experiments in progress are meant to extend the available electrophysiological data.

The results thus far emphasizes the complexity of neural networks when examined from this new point of view.
Comparison of monkey data with human data indicates that human brain has become comparatively slower than the monkey brain and that this may have expanded the dynamic range generated by the connections. Both the monkey and the human work suggest that cortical areas may be arranged in a hierarchy of processing speeds, with motor and somatosensory connections being the fastest.

Figure 1
Image

References

References
1. Caminiti, R. Ghaziri,H., Galuske,R., Hof,P.R. and Innocenti, G.M. (2009) Evolution amplified processing with temporally dispersed,slow neuronal connectivity in primates. PNAS, 106, 19551-19556
2. Tomasi, S., Caminiti, R and Innocenti, G.M. (2012) Areal differences in diameter and length of corticofugal projections. Cerebral Cortex, 22: 1463-1472
3. Innocenti, GM, Vercelli A and Caminiti R (2013) The diameter of cortical axons depends both on area of origin and termination Cerebral Cortex, in press

Keywords: cortical connections, Dynamic networks, axonal properties, Computational Neuroanatomy, evolution of cerebral cortex

Conference: Neuroinformatics 2013, Stockholm, Sweden, 27 Aug - 29 Aug, 2013.

Presentation Type: Oral presentation

Topic: Computational neuroscience

Citation: Innocenti GM (2013). A DYNAMIC APPROACH TO BRAIN CONNECTIVITY


Giorgio M Innocenti1 and Roberto Caminiti2

1 Department of Neuroscience Karolinska Institutet, Stockholm, Sweden.
2 Department of Physiology and Pharmacology, University of Rome SAPIENZA. Rome, Italy.. Front. Neuroinform. Conference Abstract: Neuroinformatics 2013. doi: 10.3389/conf.fninf.2013.09.00059

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Received: 23 Apr 2013; Published Online: 11 Jul 2013.

* Correspondence: Prof. Giorgio M Innocenti, Karolinska Institutet, Neuroscience, Stockholm, S 17177, Sweden, Giorgio.Innocenti@ki.se