Your Actions in My Cerebellum: Subclinical Deficits in Action Observation in Patients with Unilateral Chronic Cerebellar Stroke

Abstract

Empirical evidence indicates that cognitive consequences of cerebellar lesions tend to be mild and less important than the symptoms due to lesions to cerebral areas. By contrast, imaging studies consistently report strong cerebellar activity during tasks of action observation and action understanding. This has been interpreted as part of the automatic motor simulation process that takes place in the context of action observation. The function of the cerebellum as a sequencer during executed movements makes it a good candidate, within the framework of embodied cognition, for a pivotal role in understanding the timing of action sequences. Here, we investigated a cohort of eight patients with chronic, first-ever, isolated, ischemic lesions of the cerebellum. The experimental task consisted in identifying a plausible sequence of pictures from a randomly ordered group of still frames extracted from (a) a complex action performed by a human actor ("biological action" test) or (b) a complex physical event occurring to an inanimate object ("folk physics" test). A group of 16 healthy participants was used as control. The main result showed that cerebellar patients performed significantly worse than controls in both sequencing tasks, but performed much worse in the "biological action" test than in the "folk physics" test. The dissociation described here suggests that observed sequences of simple motor acts seem to be represented differentially from other sequences in the cerebellum.

Cerebellar Intermittent Theta-Burst Stimulation and Motor Control Training in Individuals with Cervical Dystonia

“…There were three other main points of difference between the studies apart from the pattern of TBS stimulation. First, we used the self-reported CDQ-24 [49], a CD-specific quality of life measure, to determine immediate and longer term effects of cerebellar iTBS. There was a significant improvement in quality of life after the intervention period in the real cerebellar iTBS group, which continued across the 12 week follow up.…”

“…The second video began with active exercises, followed by a ‘cueing task’, where participants were asked to move out of their dystonic posture in response to a sound cue. The motor control training was selected to encourage ‘motor sequencing’, a deficit known to rely on intact cerebellar function [49,50]. Participants were instructed to ‘just do the best they could’ and could stop or rest at any time in order to keep the exercise within their tolerance level.…”

Parkinson’s disease as a system-level disorder

“…The circuit, shown on Figure 5, is mainly based on data supporting the contribution of pre-SMA, SMA, Cer and BG in managing action sequences. 17,33,36,37 Different types of neurons in pre-SMA and SMA help to encode not only where in a sequence the action is but also the conditional links between the previous response and the upcoming response, often in a highly specific manner. 38 In this respect, it has been shown that pre-SMA and SMA neurons respond before some sequences (e.g., turn-pull-push a lever) but not others (e.g., turn-push-pull), 34 that some neurons of pre-SMA and SMA respond only to the rank order of a movement in the sequence (e.g., only before the second movement regardless of what the movement is), 86 and that pre-SMA and SMA cells also encode the number of movements that remain to be made to complete a sequence to obtain a reward.…”

“…In particular, we provide support for three hypotheses: (i) tremor depends on the abnormal interaction between BG and the Cer–Ctx loops: this hypothesis builds on key data on the involvement of these loops in tremor 20,21,29 and on the recently discovered STN–Cer disynaptic connection; 13 (ii) freezing is linked to abnormal interactions between the BG pathways, the presupplementary motor area (pre-SMA) and Cer–Str disynaptic link: 12 this hypothesis builds on evidence showing the influence of pre-SMA 30,31 and Cer 31,32 on freezing; (iii) dysfunctions in the circuit linking Cer to SMA, and in the hyperdirect pathway linking SMA with STN, may have a role in action sequencing impairments: this hypothesis is based on data showing the contribution of pre-SMA/SMA, 33,34 Cer 17,35 and BG 36,37 in action sequences and on recent evidence on pre-SMA/SMA role in PD. 38,39 We also furnish some more general indications on how the view proposed here might contribute to advance our understanding of other motor and non-motor features of PD.…”

“…13 Similar data have recently been found in humans, using diffusion tensor imaging (DTI). 14,15 These data have stimulated new research directed at investigating the role of Cer and BG in functions typically associated with cortical areas (e.g., action understanding 7,16,17 ), and the role of cerebellar and cortical areas in impairments typically associated with BG, such as Tourette’s syndrome, 18 dystonia, 19 and PD. 8,20–23 …”