Abstract
Some of the anatomical and functional basis of cognitive impairment in multiple sclerosis (MS) currently remains unknown. In particular, there is scarce knowledge about modulations in induced EEG (nonphase activity) for diverse frequency bands related to attentional deficits in this pathology. The present study analyzes phase and nonphase alpha and gamma modulations in 26 remitting-relapsing multiple sclerosis patients during their participation in the attention network test compared with twenty-six healthy controls (HCs) matched in sociodemographic variables. Behavioral results showed that the MS group exhibited general slowing, suggesting impairment in alerting and orienting networks, as has been previously described in other studies. Time–frequency analysis of EEG revealed that the gamma band was related to the spatial translation of the attentional focus, and the alpha band seemed to be related to the expectancy mechanisms and cognitive processing of the target. Moreover, phase and nonphase modulations differed in their psychophysiological roles and were affected differently in the MS and HC groups. In summary, nonphase modulations can unveil hidden cognitive mechanisms for phase analysis and complete our knowledge of the neural basis of cognitive impairment in multiple sclerosis pathology.
Highlights
Multiple sclerosis (MS) is a chronic degenerative neurological disease of unknown etiology that causes mainly neurological damage including demyelination and inflammation of the central nervous system (CNS)[1]
The cue factor revealed differences between cues, with the no cue (NC) condition showing larger reaction times followed by the central cue (CC) condition and the spatial cue (SC) condition, which was the fastest [F (2,100) = 287.04; p < 0.001; η2 = 0.930] (Table 1and supplementary Table 1 for statistical results)
After applying the correction of Fernández-Duque and B lack[53], differences in the NC condition were observed between groups [t = 2.186; p = 0.03], and patients were faster than healthy controls (HCs)
Summary
Multiple sclerosis (MS) is a chronic degenerative neurological disease of unknown etiology that causes mainly neurological damage including demyelination and inflammation of the central nervous system (CNS)[1]. The ANT was developed to assess three attentional networks (alerting, orienting and executive systems) and has been performed with different versions and for diverse pathologies[11,12,13,14]. The ANT was developed in 2 00115, it did not begin to be applied in patients with multiple sclerosis until 201016 These authors found an alteration in patients’ alerting network with respect to healthy controls (HCs). Through TSE and other time–frequency techniques, numerous studies have related frequency bands of EEG to specific cognitive mechanisms. Some authors have argued that it may not exclusively reflect an idling status but can play an active role in inhibitory control and timing of sensory p rocessing[25]. For attentional visual processing, some studies have observed higher alpha activity in those regions of the occipital cortex where unattended locations are retinotopically represented[27,28,29]
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