Cortico-Cerebellar Monitoring of Speech Sequence Production

Abstract

In a functional magnetic resonance imaging study, we examined speech error monitoring in a cortico-cerebellar network for two contrasts: (a) correct trials with high versus low articulatory error probability and (b) overtly committed errors versus correct trials. Engagement of the cognitive cerebellar region Crus I in both contrasts suggests that this region is involved in overarching performance monitoring. The activation of cerebellar motor regions (superior medial cerebellum, lobules VI and VIII) indicates the additional presence of a sensorimotor driven implementation of control. The combined pattern of pre-supplementary motor area (active across contrasts) and anterior cingulate cortex (only active in the contrast involving overt errors) activations suggests sensorimotor driven feedback monitoring in the medial frontal cortex, making use of proprioception and auditory feedback through overt errors. Differential temporal and parietal cortex activation across contrasts indicates involvement beyond sensorimotor driven feedback in line with speech production models that link these regions to auditory target processing and internal modeling-like mechanisms. These results highlight the presence of multiple, possibly hierarchically interdependent, mechanisms that support the optimizing of speech production.

Keywords: cerebellum; fMRI; internal modeling; monitoring; speech production.

Figure 1.

Illustrations of the cerebellum obtained from the SUIT online atlas tool (Diedrichsen et al., 2009). The crosshair in each of the three panels is located at different functional subcompartments (from left to right): the cognitive or transmodal region Crus I, the motor region lobule VIII, and the motor region SMC (superior medial cerebellum).

Figure 2.

Depiction of an experimental trial.

Figure 3.

Average production accuracy over the five experimental runs in each monitoring load condition. Error bars represent standard errors of the mean.

Figure 4.

Mean beta value differences in the predefined region of interest (ROI). Top panel represents the locations of the seven predefined regions of interest (ROIs): Crus I, SMC, L-VIII, pre-SMA, ACC, pSTG, and SPT. Middle panel and bottom panel represent the internal monitoring contrast and the external monitoring contrast, respectively. ROIs in medial frontal cortex are represented with blue tones, ROIs in the cerebellum with green tones, and ROIs in temporo-parietal cortex with red tones. The asterisks indicate significant effects <0.05 (*) or <0.005 (**) after applying Bonferroni correction for multiple comparisons. SMC = superior medial cerebellum, L-VIII = lobule VIII, pre-SMA = pre-supplementary motor area, ACC = anterior cingulate cortex, pSTG = posterior superior temporal gyrus, and SPT = Sylvian fissure at the temporoparietal boundary.

Figure 5.

Results of the whole brain analysis. BOLD response of internal monitoring (high vs. low monitoring load for correct trials, yellow) and external monitoring (errors vs. correct trials, blue) contrasts. Overlap across contrasts is visible as green. Statistical t maps are overlaid on an MNI template using a voxelwise threshold of p < 0.001 and an extent threshold of 25 voxels. Numbers in brackets represent Brodmann areas. IFG = inferior frontal gyrus, IPG = inferior parietal gyrus, SMA = supplementary motor area, SPG = superior parietal gyrus, STG = superior temporal gyrus.