Learning and switching between stimulus-saccade associations in Parkinson’s disease

Abstract

Making flexible associations between what we see and what we do is important for many everyday tasks. Previous work in patients with focal lesions has shown that the control of saccadic eye movements in such contexts relies on a network of areas in the frontal cerebral cortex. These regions are reciprocally connected with structures in the basal ganglia although the contribution of these sub-cortical structures to oculomotor control in complex tasks is not well understood. We report the performance of patients with idiopathic Parkinsons disease (PDs) in a test which required learning and switching between arbitrary cue-saccade rules. In Experiment 1 feedback was given following each response which reliably indicated which of the two possible rules was correct. PDs were slower to learn the first cue-saccade association presented, but did not show increased error or reaction time switch costs when switching between two rules within blocks. In a follow up experiment the feedback given by the computer was adjusted to be probabilistic such that executing a response based upon the “correct” rule only resulted in positive feedback on 80% of trials. Under these conditions patients were impaired in terms of response latencies and number of errors. In all conditions PDs showed multi-stepping/hypometria of saccades consistent with a motoric deficit in executing actions based on cognitive cues. The findings are consistent with a role for the nigrostriatal dopamine system in the reinforcement of saccade-response-outcome associations. Intact performance of PDs when associations are not stochastically reinforced suggests that striatal learning systems are complemented by cognitive representations of task rules which are unaffected in the early stages of PD.

Motor‐symptom laterality affects acquisition in Parkinson's disease: A cognitive and functional magnetic resonance imaging study

“…Feedback‐based associative learning, which involves learning through corrective feedback provided on each trial, has been correlated with striatal dopamine release and function of the basal ganglia . Previous studies have reported that feedback‐based associative learning was impaired in PD patients . However, the impairment in feedback‐based learning in PD is not a universal finding, and many factors could contribute to this variability.…”

“…10,11 Previous studies have reported that feedback-based associative learning was impaired in PD patients. 12,13 However, the impairment in feedback-based learning in PD is not a universal finding, and many factors could contribute to this variability. Wilkinson and colleagues did not find a selective impairment in PD in probabilistic feedback-based learning, but reported that there was a significant correlation between disease severity and the impairment in feedback-based learning.…”

Freezing of gait in Parkinson's disease is related to impaired motor switching during stepping

“…In fact, a wealth of evidence indicates that PD patients lack the ability to flexibly switch between cognitive sets as well. 10,[15][16][17][18][19][20][21][22] For example, PD patients are impaired when switching attention between extradimensional stimulus features (eg, from color to shape) of multidimensional stimuli (as in the Wisconsin card sorting test) 15,18,19 as well as between welllearned cognitive task-sets. 10,16,17,23 Thus, PD patients exhibit robust set switching deficits.…”

How Saccade Intrusions Affect Subsequent Motor and Oculomotor Actions

“…Interestingly, the left ventral premotor cortex, which is thought to play an important role in the shared initiation process, is almost identical to the area that forms part of a wider frontal network mediating inhibitory control over stimulus-elicited eye movements, i.e., saccades to cue and saccades to target in the present study (Hodgson et al, 2007), whereas the homologous area in the right ventral premotor cortex is involved in rule task switching (Hodgson et al, 2007, 2013, 2015). …”

“…It is known that behavior slows down when switching between controlled and automatic behavior (Cherkasova et al, 2002; Vernet et al, 2009; Weiler and Heath, 2012, 2014; Hodgson et al, 2013, 2015). The effect of saccade intrusions on subsequent voluntary saccades may reflect a similar switching cost: saccades to cue can be considered to represent visually guided saccades to the cue, whereas the ensuing MGS can be considered voluntarily controlled saccades.…”