Inhibition of the supplementary motor area affects distribution of effort over time

Aviv Emanuel, Jasmine Herszage, Haggai Sharon, Nira Liberman, Nitzan Censor*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


In tasks that extend over time, people tend to exert much effort at the beginning and the end, but not in the middle, exhibiting the stuck-in-the-middle pattern (STIM). To date, little is known about the neural mechanisms underlying this effect. As the supplementary motor area (SMA) was previously implicated in coding prospective task-demands, we tested its role in producing the STIM pattern. Participants first underwent an SMA-localization session in which they tapped their fingers repeatedly while fMRI-scanned. In the next two sessions, before playing a 10-min computer game that measured effort-engagement, participants underwent inhibitory 1-Hz repetitive transcranial magnetic stimulation over the SMA, or over a control precuneus location. Three control experiments and a pretest confirmed that this task yields a STIM, which can be eliminated when the task lacks a salient end-point, or is too short. The results of the main experiment showed a more pronounced STIM following inhibitory SMA stimulation compared to control. A control analysis showed that overall level of effort was similar in both conditions, rendering alternative accounts in terms of motor inhibition unlikely. These findings are consistent with the possibility that the SMA may play a role in moment-to-moment coding of effort value, or in related sub-processes, which can cause effort to be distributed more equally over the course of a task.

Original languageEnglish
Pages (from-to)134-144
Number of pages11
StatePublished - Jan 2021


FundersFunder number
Israel Science Foundation51/11, 526/17
Planning and Budgeting Committee of the Council for Higher Education of Israel


    • Effort allocation
    • Goal gradient
    • SMA
    • TMS


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