Spinocerebellar Ataxia Type 2 Neurodegeneration Differentially Affects Error-Based and Strategic-Based Visuomotor Learning

Abstract

There are different types of visuomotor learning. Among the most studied is motor error-based learning where the sign and magnitude of the error are used to update motor commands. However, there are other instances where individuals show visuomotor learning even if the sign or magnitude of the error is precluded. Studies with patients suggest that the former learning is impaired after cerebellar lesions, while basal ganglia lesions disrupt the latter. Nevertheless, the cerebellar role is not restricted only to error-based learning, but it also contributes to several cognitive processes. Therefore, here, we tested if cerebellar ataxia patients are affected in two tasks, one that depends on error-based learning and the other that prevents the use of error-based learning. Our results showed that cerebellar patients have deficits in both visuomotor tasks; however, while error-based learning tasks deficits correlated with the motor impairments, the motor error-dependent task did not correlate with any motor measure.

Strategy Use, Planning, and Rule Acquisition Deficits in Spinocerebellar Ataxia Type 2 Patients

“…implementing rules to solve classification tasks, attentional set-shifting, spatial working memory, and generation of strategies for remembering spatial locations, which is consistent with the deterioration in strategy learning independent of the motor deterioration in SCA2 previously reported by our group (Vaca-Palomares et al, 2013). The aforementioned evidence suggests that further studies should be designed to understand the nature of these cognitive and motor variations.…”

Effects of aging on strategic-based visuomotor learning

“…Such realignment would contribute to the reduction of the error produced by the prism perturbation, and it would also result in a negative aftereffect once the perturbation is removed (Redding and Wallace, 1990;Redding et al, 2005). However, it has recently been shown that participants do not update their learning rule when adapting to reversing prisms (Lillicrap et al, 2013;Vaca-Palomares et al, 2013) or mirror reversals (Gritsenko and Kalaska, 2010). Instead, they adopt strategies that allow them to reduce the error, but at the expense of performance accuracy (Lillicrap et al, 2013;Mazzoni and Krakauer, 2006).…”

“…For this purpose we used the following criteria: if the error magnitude of the last throw of condition PRI (PRI-26) was less than the error magnitude of the first throw of the PRI condition (PRI-1) minus the standard deviation of the baseline, we considered the participant as an "adapter", otherwise we considered the participant as a "nonadapter" (Lillicrap et al, 2013;Vaca-Palomares et al, 2013). To analyze the proportion of participants adapting to the prisms, the z-ratio for the significance of the difference between two independent proportions was calculated (Vaca-Palomares et al, 2013). Additionally, to analyze the adaptation rate across trials between the younger and older group a repeated-measures ANOVA on the PRI condition of both prisms was performed.…”

“…the spatial coordinates of the visual stimulus and the hand in their respective frames of reference (Fernandez-Ruiz & Díaz, 1999;Wolpert, Diedrichsen, & Flanagan, 2011). Two different types of prism perturbations have been studied, the displacement of the visual field produced with wedge prisms (Fernandez-Ruiz and Díaz, 1999;Martin et al, 1996aMartin et al, , 1996bRedding et al, 2005) and the reversing of the visual field produced with dove prisms (Lillicrap et al, 2013;Marotta et al, 2005;Vaca-Palomares et al, 2013). The critical difference between both perturbations is the role of visual feedback in the system.…”

“…In this case the participants must reduce their errors by correcting also in the leftward direction, but since the visual feedback is also reversed, the error feedback is incongruent, which would mistakenly suggest a rightward correction. Therefore, it has recently been proposed that to adapt to this perturbation participants should implement strategic processes (Abdelghani et al, 2008;Lillicrap et al, 2013;Taylor and Ivry, 2012;Vaca-Palomares et al, 2013).…”