Abstract
It is generally accepted that the basal ganglia play an important role in interval timing that requires the measurement of temporal durations. By contrast, it remains controversial whether the basal ganglia play an essential role in temporal order judgment (TOJ) of successive stimuli, a behavior that does not necessarily require the measurement of durations in time. To address this issue, we compared the effects of idiopathic Parkinson’s disease (PD) on the TOJ of two successive taps delivered to each hand, with the arms uncrossed in one condition and crossed in another. In addition to age-matched elderly participants without PD (non-PD), we examined young healthy participants so that the effect of aging could serve as a control for evaluating the effects of PD. There was no significant difference between PD and non-PD participants in any parameter of TOJ under either arm posture, although reaction time was significantly longer in PD compared with non-PD participants. By contrast, the effect of aging was apparent in both conditions. With their arms uncrossed, the temporal resolution (the interstimulus interval that yielded 84% correct responses) in elderly participants was significantly worse compared with young participants. With their arms crossed, elderly participants made more errors at longer intervals (~1 s) than young participants, although both age groups showed similar judgment reversal at moderately short intervals (~200 ms). These results indicate that the basal ganglia and dopaminergic systems do not play essential roles in tactile TOJ involving both hands and that the effect of aging on TOJ is mostly independent of the dopaminergic systems.
Highlights
Patients with Parkinson’s disease (PD), a neurodegenerative disease strongly associated with basal ganglia dysfunction, show deficits in temporal processing when performing temporal reproduction tasks [1,2,3], perceptual timing tasks [4, 5], simultaneity judgments, and temporal discriminationPLOS ONE | DOI:10.1371/journal.pone.0118331 March 11, 2015Effects of Parkinson’s Disease on Tactile Temporal Order Judgment between two stimuli [6,7,8]
When participants were required to judge the temporal order of two successive tactile stimuli, delivered to different fingers on the same hand, Fiorio, Valente, Gambarin, Bentivoglio, Ialongo, Albanese, Barone, Pellecchia, Brancati, Moretto, Fiaschi and Tinazzi [7] reported that the threshold interval to judge the order of the two stimuli was significantly larger in participants with familial PD due to a PINK1 mutation compared with age-matched healthy participants
Because the information processing required for temporal order judgment (TOJ) is proposed to be different from that required for simultaneity judgment (SJ) [13,14,15], and the two processes have been modeled to work in parallel [16], task performance in TOJ should have been disturbed by the concurrent SJ task in the study by Fiorio, Valente, Gambarin, Bentivoglio, Ialongo, Albanese, Barone, Pellecchia, Brancati, Moretto, Fiaschi and Tinazzi [7]
Summary
Patients with Parkinson’s disease (PD), a neurodegenerative disease strongly associated with basal ganglia dysfunction, show deficits in temporal processing when performing temporal reproduction tasks [1,2,3], perceptual timing tasks [4, 5], simultaneity judgments, and temporal discriminationPLOS ONE | DOI:10.1371/journal.pone.0118331 March 11, 2015Effects of Parkinson’s Disease on Tactile Temporal Order Judgment between two stimuli [6,7,8]. Nelson, Premji, Rai, Hoque, Tommerdahl and Chen [12] reported that the threshold interval in patients with idiopathic PD was similar to age-matched controls, even during periods without medication This discrepancy may be due to differences in the genetic backgrounds of the two patient groups, but it is worth noting that Fiorio, Valente, Gambarin, Bentivoglio, Ialongo, Albanese, Barone, Pellecchia, Brancati, Moretto, Fiaschi and Tinazzi [7] required the participants to judge both simultaneity and temporal order, whereas Nelson, Premji, Rai, Hoque, Tommerdahl and Chen [12] required the participants to only judge temporal order. Assuming that PD patients showed impaired performance in the SJ task, the TOJ task must have been more disturbed by the concurrent SJ task in PD patients than in age-matched controls
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