Decrease of Mutual Information in Brain Electrical Activity of Patients with Relapsing-Remitting Multiple Sclerosis

Abstract

The disturbance of cortical communication has been hypothesized as an important factor in the appearance of cognitive impairment in (MS). Cortical communication is quantified here in control subjects and patients with relapsing-remitting multiple sclerosis (RRMS) on the basis of mean coherence in the δ, θ, α, β and γ bands and using mutual information computed between pairs of bipolar EEG signals recorded during resting condition. Each patient received also a cognitive assessment using a battery of neuropsychological tests specific to cognitive deficits in MS.No difference was observed for the coherence indices whereas inter-hemispheric and right hemisphere mutual information is significantly lower in patients with MS than in control subjects. Moreover, inter-hemispheric mutual information decrease significantly with illness duration and right mutual information differentiate cognitively deficient and non-deficient patients.Mutual information allows to quantify the cortical communication in patients with RRMS and is related to clinical characteristics.Cortical communication quantified in a resting state might be a potential marker for the neurological damage induced by RRMS.

Fluctuations of spontaneous EEG topographies predict disease state in relapsing-remitting multiple sclerosis

“…The results of the other very few EEG and MEG resting state studies in patients with MS converge with this most frequently observed MS-related brain pathology of axonal loss and atrophy in the corpus callosum, with their finding of described decreased interhemispheric coherence (Cover et al, 2006, Hardmeier et al, 2012, Lenne et al, 2013, Leocani et al, 2000, Schoonheim et al, 2013b, Van Schependom et al, 2014). These studies showed focally higher synchronization likelihood in temporo-occipital and parieto-occipital connections and lower inter-temporal connectivity (Schoonheim et al, 2013b) in patients with RRMS, with a shift from temporal to less efficient parietal processing, correlating with a decrease in cognitive performance (Hardmeier et al, 2012).…”

“…Decreased interhemispheric connectivity is one of the most robust findings among fMRI studies on resting state in patients with MS (Bonavita et al, 2011, Hawellek et al, 2011, Leonardi et al, 2013, Richiardi et al, 2012). Whereas the above-mentioned coherence studies (Cover et al, 2006, Hardmeier et al, 2012, Lenne et al, 2013, Leocani et al, 2000, Schoonheim et al, 2013b, Van Schependom et al, 2014) concentrated on spatial variations of average correlations between regions of interest, they investigate average values across a time window and are primarily blind to the temporal variability of the dynamic connectivity (Allen et al, 2014, Leonardi et al, 2013), which was detected with the microstate approach described here. Note that the basic spectral analysis of the EEG signal in our patients did not reveal any difference between patients with RRMS and controls; in particular, there was no diffuse slowing in the signal as it had been described in patients with advanced MS (Beach et al, 2011, Striano et al, 2003).…”

“…Very few studies have looked at electrophysiological markers of the clinical course (Fuhr et al, 2001, Schlaeger et al, 2014), and only recently has interest grown in the functional connectivity and resting-state network analysis by EEG, with the aim to characterize altered neuronal conduction known to occur in MS pathology (Lenne et al, 2013, Leocani et al, 2000, Van Schependom et al, 2014). A few MEG studies investigated functional connectivity at rest in patients with MS and found altered connectivity patterns in specific frequency bands (Cover et al, 2006, Hardmeier et al, 2012, Schoonheim et al, 2013b, Tewarie et al, 2013, Van der Meer et al, 2013).…”

Cortical sources of resting state electroencephalographic rhythms differ in relapsing–remitting and secondary progressive multiple sclerosis

“…Specifically, there was a pathological increase of EEG power density at low frequencies (delta, 2-4 Hz) and a decrease of EEG power density at higher frequencies (alpha, 8-12 Hz), which is a spectral pattern typically related to cognitive dysfunctions in humans (Leocani and Comi, 2000). Compared to healthy subjects, MS patients pointed to an increase of EEG power density at slow frequency in frontotemporal-central scalp regions, as well as decreased coherence/mutual information of EEG rhythms between electrode pairs (Leocani et al, , 2010Lenne et al, 2013). A similar reduction of coherence between electrodes placed in the two hemispheres (i.e.…”

Unilateral olfactory sensitivity in multiple sclerosis

“…In the case of MS, an impaired cortical network has been found whose nexus is within the right hemisphere [30]. Moreover, greater right-side damage to the locus coeruleus has been noted in MS which could differentially influence right hemisphere attentional processes [31].…”