Cerebellar and Cortical Correlates of Internal and External Speech Error Monitoring

Abstract

An event-related functional magnetic resonance imaging study examined how speakers inspect their own speech for errors. Concretely, we sought to assess 1) the role of the temporal cortex in monitoring speech errors, linked with comprehension-based monitoring; 2) the involvement of the cerebellum in internal and external monitoring, linked with forward modeling; and 3) the role of the medial frontal cortex for internal monitoring, linked with conflict-based monitoring. In a word production task priming speech errors, we observed enhanced involvement of the right posterior cerebellum for trials that were correct, but on which participants were more likely to make a word as compared with a nonword error (contrast of internal monitoring). Furthermore, comparing errors to correct utterances (contrast of external monitoring), we observed increased activation of the same cerebellar region, of the superior medial cerebellum, and of regions in temporal and medial frontal cortex. The presence of the cerebellum for both internal and external monitoring indicates the use of forward modeling across the planning and articulation of speech. Dissociations across internal and external monitoring in temporal and medial frontal cortex indicate that monitoring of overt errors is more reliant on vocal feedback control.

Keywords: cerebellum; error monitoring; fMRI; forward modeling; speech production.

Figure 1

Depiction of the experimental design and procedure.

Figure 2

Percent signal change in the 11 predefined ROI (location in the brain in top central panel) for (A) the internal monitoring contrast and (B) the external monitoring contrast. ROIs in medial frontal cortex are represented with blue tones, ROIs in the cerebellum in green tones and ROIs in temporal cortex in red tones. The asterisks indicate significant effects <0.05 (^*) or <0.005 (^**) after correcting for multiple comparisons using FDR.

Figure 3

RFX results on the BOLD response of internal monitoring (lexical vs. nonlexical error priming; panel A) and external monitoring (errors vs. correct trials; panel B). Statistical t-maps are overlaid on MNI cortex slices (5 axial slices and 1 sagittal slice per line) using a voxelwise threshold of P < .001 and an extent threshold of 25 voxels.