Is action-perception coupling improved with delay in patients with focal cerebellar lesions?

Editor's Note: These short, critical reviews of recent papers in the Journal, written exclusively by graduate students or postdoctoral fellows, are intended to summarize the important findings of the paper and provide additional insight and commentary. For more information on the format and purpose of the Journal Club, please see It has been proposed that the cerebellum uses internal forward models to predict sensory consequences of particular actions (Wolpert and Flanagan, 2001). This allows movements to be corrected when necessary. In addition to its paramount role in the control of movements, the cer-ebellum is also involved in sensory processing and perception, but there is no straightforward evidence for the cerebe-llum's involvement in the integration of action and perception. Therefore, a recent study in The Journal of Neuroscience set out to investigate the role of the cerebel-lum in action–perception coupling. Specifically , Christensen et al. (2014) studied patients with focal cerebellar lesions and healthy controls in a paradigm that measures the effect of motor execution on visual action perception. Participants performed waving motions with the right arm using a setup that allowed participants' own arm movements to be visually presented on a screen in front of them (as five black dots). These stimuli were accompanied by varying numbers of noise dots, which moved based on the waving movements of the participants, but were spatiotemporally scrambled. The patients were asked to indicate whether they recognized a waving arm movement. Two-thirds of the trials contained the arm and noise dots, and in half of these trials the participants' own movements were presented in real-time (" synchronous " test condition; delay ϳ38 ms), while in the other half the partici-pants' movements were presented with a time delay of 700 ms (" asynchronous " test condition). In the remainder of the trials, only noise dots were presented. In addition, the participants performed the waving arm detection task without performing the waving movements (baseline condition). Detection performance was assessed using the noise tolerance value (NTV; i.e., the maximum number of noise dots that would lead to 75% of the optimal detection sensitivity). The influence of motor execution on detection performance was quantified (for the synchronous and asyn-chronous conditions separately) as the logarithm of the NTV of the test condition divided by the NTV of the baseline. This measure was called the interaction-index. An interaction-index value Ͼ0 indicates a facilitatory effect of motor execution on perception, whereas …