Action Control Deficits in Patients With Essential Tremor

Abstract

Objective: Essential Tremor (ET) is a movement disorder characterized by action tremor which impacts motor execution. Given the disrupted cerebellar-thalamo-cortical networks in ET, we hypothesized that ET could interfere with the control mechanisms involved in regulating motor performance. The ability to inhibit or stop actions is critical for navigating many daily life situations like driving or social interactions. The current study investigated the speed of action initiation and two forms of action control, response stopping and proactive slowing in ET. Method: Thirty-three ET patients and 25 healthy controls (HCs) completed a choice reaction task and a stop signal task, and measures of going speed, proactive slowing and stop latencies were assessed. Results: Going speed was significantly slower in ET patients (649 ms) compared to HCs (526 ms, F(1, 56) = 42.37, p<.001, η2=.43), whereas proactive slowing did not differ between groups. ET patients exhibited slower stop signal reaction times (320 ms) compared to HCs (258 ms, F (1, 56)=15.3, p<.00, η2=.22) and more severe motor symptoms of ET were associated with longer stopping latencies in a subset of patients (Spearman rho = .48, p<.05). Conclusions: In line with previous studies, ET patients showed slower action initiation. Additionally, inhibitory control was impaired whereas proactive slowing remained intact relatively to HCs. More severe motor symptoms of ET were associated with slower stopping speed, and may reflect more progressive changes to the cerebellar-thalamo-cortical network. Future imaging studies should specify which structural and functional changes in ET can explain changes in inhibitory action control.

Cortico-subcortical β burst dynamics underlying movement cancellation in humans

“…Go accuracy was the only behavioral metric which significantly differed between the STN and VIM DBS groups (T(19) = 5.22, p < .0001, d = 2.27), with VIM patients responding more accurately on go-trials. On average, the VIM implant group also responded faster during correct go and failed stop trials and cancelled movements more quickly than STN DBS patients, as indicated by SSRT (which was in the typical elongated range for movement disorder patients: Gauggel et al, 2004;Obeso et al, 2011;Hughes et al, 2019). However, none of these results were significant, indicating comparable task performance between both groups.…”

Cortico-subcortical β burst dynamics underlying movement cancellation in humans

“…Go accuracy was the only behavioral metric which significantly differed between the STN and thalamic groups, with thalamic patients responding more accurately on go-trials (94% vs 83% accuracy, T(19) = 5.22, p < .0001, d = 2.27). Numerically, the thalamic implant group also responded faster during correct go and failed stop trials and cancelled movements more quickly than STN DBS patients, as indicated by SSRT (which was in the typical elongated range for movement disorder patients: Gauggel et al, 2004;Obeso et al, 2011;Hughes et al, 2019). However, none of these results 8 were significant, indicating comparable task performance between both groups.…”

Essential tremor impairs the ability to suppress involuntary action impulses

“…These results add to a growing body of evidence that ET has an effect on action control beyond tremor. Previous investigations on inhibitory stopping control in ET patients have found slowed action initiation and a reduced ability to stop actions intentionally (Brunamonti et al 2014;Hughes et al 2019). Experimental studies of other cognitive control measures like the Attentional Network Task have also observed differences in performance in ET populations.…”

“…Given the unique motor control deficits in ET, recent studies have focused on how disruption to cerebello-thalamocortical circuitries in ET alter the proficiency of executive cognitive systems involved specifically in the control of actions (action control) (Brunamonti et al 2014;Hughes et al 2019). Using the stop-signal task (SST), a well-established paradigm that allows quantification of the latency to initiate and inhibit reactions, ET patients showed both slower reactions to stimulus events as well as slower stopping when presented with a sudden change in stimulus events.…”