Vision loss after peripheral optic nerve lesions is related to permanent alteration of long-range cortical functional connectivity: an EEG resting state analysis
| Type of publication: | Misc |
| Citation: | bola_vision_2013 |
| Year: | 2013 |
| Month: | March~13--16 |
| Howpublished: | Abstract |
| Note: | Presented at the 10th G\"ottingen Meeting of the German Neuroscience Society |
| URL: | http://www.nwg-goettingen.de/2... |
| Abstract: | Introduction: Our understanding of how the visual system of the brain works has evolved from rather static feature detection specialization of certain brain areas to a complex and dynamic network of interacting elements. We are now witnessing a paradigm shift in our understanding of neurological dysfunctions: not only local tissue loss is responsible for functional loss but also downstream alterations of connectivity networks that reach far beyond the lesion locus. Yet, in the field of vision field defects following CNS lesions this issue has not been studied. We now wished to address the role of cortical functional connectivity changes in functional vision loss in patients with optic nerve lesions. The rationale for studying peripheral lesions was to avoid any central cortical insult so we could determine functional connectivity changes under functional deprivation conditions, without confounding the results with central degenerative influences. Methods: Resting state EEG signal was recorded from 15 patients with pre-chiasmatic visual system damage and 13 age-matched normal controls at eyes closed condition. Following standard preprocessing, the signal was divided into 1s-epochs and power density, coherence, and Granger Causality (Seth, 2010) were calculated. Coherence results were analyzed either (i) as absolute values indicating coupling within and between chosen regions of interest or (ii) as individually thresholded binary graphs, consisting of the same number of edges. Small-world parameters and degree distribution were then calculated (Rubinov and Sporns, 2010). Results: Between group differences were found only in the high alpha band (11-13Hz) but not in any other frequency band analyzed (delta, theta, low alpha, or beta). Firstly, occipital regions (O1, O2) high alpha band exhibited lower power in patients compared to controls in (rmANOVA, interaction: p=0.005). Secondly, in patients short-range functional connectivity (coherence) was weaker at both occipital (O1, O2) and frontal (Fz, FC1, FC2) regions (rmANOVA, group: p=0.015). Thirdly, decreased long-range coherence was noted in patients between occipital and frontal regions (t-test, p=0.033). These results were confirmed with Granger causality analysis which revealed that the strength of both, bottom-up (occ. to frontal) and top-down coupling (frontal to occ.) was impaired in patients (rmANOVA, group: p=0.032). Finally, coherence network topology (Fig. 1) revealed that the clustering coefficient was lower in patients high-alpha coherence networks than in control subjects (t-test: p=0.025). Conclusions: The connectivity changes in the resting state EEG of patients with peripheral visual system damage are indications of permanent alterations in cortical network activities in blindness. All changes were specific to the high-alpha band suggesting a special role of this narrow frequency band in proper visual functioning. We interpret the decreased power, loss of connectivity strength, and reduction of the clustering coefficient as a loss of synchronization among widely distributed brain regions. We found no signs of compensatory plasticity, e.g. increased connectivity strength in any regions. |
| Keywords: | functional connectivity, peripheral optic nerve, resting-state EEG, visual damage |
| Authors | |
| Added by: | [CM] |
| Total mark: | 0 |
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