Abstract
A growing body of evidence implies psychological disturbances in amyotrophic lateral sclerosis (ALS). Specifically, executive dysfunctions occur in up to 50% of ALS patients. The recently shown presence of cytoplasmic aggregates (TDP-43) in ALS patients and in patients with behavioral variants of frontotemporal dementia suggests that these two disease entities form the extremes of a spectrum. The present study aimed at investigating behavioral and electrophysiological indices of conflict processing in patients with ALS. A non-verbal variant of the flanker task demanded two-choice responses to target stimuli that were surrounded by flanker stimuli which either primed the correct response or the alternative response (the latter case representing the conflict situation). Behavioral performance, event-related potentials (ERP), and lateralized readiness potentials (LRP) were analyzed in 21 ALS patients and 20 controls. In addition, relations between these measures and executive dysfunctions were examined. ALS patients performed the flanker task normally, indicating preserved conflict processing. In similar vein, ERP and LRP indices of conflict processing did not differ between groups. However, ALS patients showed enhanced posterior negative ERP waveform deflections, possibly indicating increased modulation of visual processing by frontoparietal networks in ALS. We also found that the presence of executive dysfunctions was associated with more error-prone behavior and enhanced LRP amplitudes in ALS patients, pointing to a prefrontal pathogenesis of executive dysfunctions and to a potential link between prefrontal and motor cortical functional dysregulation in ALS, respectively.
Highlights
Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease characterized by combined degeneration of upper and lower motor neurons
This study brought into focus whether flanker congruency (i.e., congruency effect (CE)) and/or congruency sequence (i.e., congruency sequence effect (CSE)) exerted differential effects on behavioral, event-related potentials (ERP) and lateralized readiness potentials (LRP) responses in ALS patients and HC
This article demonstrates the utility of ERP and LRP measures that provide the means for decomposing psychological disturbances associated with ALS into constituent parts (Figure 8)
Summary
Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease characterized by combined degeneration of upper and lower motor neurons. While ALS has traditionally been thought to be restricted to the motor nervous system, it is increasingly acknowledged as a multiple system disease, affecting non-motor areas of the cortex (Kew et al, 1993a; Abrahams et al, 1996; Geser et al, 2008; Wijesekera and Leigh, 2009; Kiernan et al, 2011; Sarro et al, 2011; Tsermentseli et al, 2012; Agosta et al, 2013; Pettit et al, 2013; Turner et al, 2013; Swinnen and Robberecht, 2014; Turner and Swash, 2015). Comorbid FTD (Olney et al, 2005; Elamin et al, 2011) and executive dysfunction in non-demented ALS patients has been found to be associated with shorter survival times (Elamin et al, 2011)
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