Neural Connectivity in Syntactic Movement Processing

Abstract

Linguistic theory suggests non-canonical sentences subvert the dominant agent-verb-theme order in English via displacement of sentence constituents to argument (NP-movement) or non-argument positions (wh-movement). Both processes have been associated with the left inferior frontal gyrus and posterior superior temporal gyrus, but differences in neural activity and connectivity between movement types have not been investigated. In the current study, functional magnetic resonance imaging data were acquired from 21 adult participants during an auditory sentence-picture verification task using passive and active sentences contrasted to isolate NP-movement, and object- and subject-cleft sentences contrasted to isolate wh-movement. Then, functional magnetic resonance imaging data from regions common to both movement types were entered into a dynamic causal modeling analysis to examine effective connectivity for wh-movement and NP-movement. Results showed greater left inferior frontal gyrus activation for Wh > NP-movement, but no activation for NP > Wh-movement. Both types of movement elicited activity in the opercular part of the left inferior frontal gyrus, left posterior superior temporal gyrus, and left medial superior frontal gyrus. The dynamic causal modeling analyses indicated that neither movement type significantly modulated the connection from the left inferior frontal gyrus to the left posterior superior temporal gyrus, nor vice-versa, suggesting no connectivity differences between wh- and NP-movement. These findings support the idea that increased complexity of wh-structures, compared to sentences with NP-movement, requires greater engagement of cognitive resources via increased neural activity in the left inferior frontal gyrus, but both movement types engage similar neural networks.

Keywords: dynamic causal modeling; functional magnetic resonance imaging; non-canonical sentences; sentence comprehension; syntactic movement.

Figure 1

Example trial from the auditory sentence-picture verification task.

Figure 2

Base dynamic causal model of network of regions involved in non-canonical sentence processing for sentence-picture verification task. LSFGm, Left superior frontal gyrus, medial part. LIFGop, left inferior frontal gyrus, opercular part. LSTGp, Left superior temporal gyrus, posterior part.

Figure 3

Significant fMRI activation (uncorrected voxelwise p < 0.001) of the contrasts Sentences > Baseline and vice-versa (corrected cluster-defining threshold k > 61), Non-canonical > Canonical (k > 43.4), and Wh > NP-movement (k > 42.1) from healthy adult participants.

Figure 4

Significant fMRI activation (uncorrected voxelwise p < 0.001) of Non-canonical > Canonical (corrected cluster-defining threshold k > 61) masked by Sentences > Baseline (k > 61) from healthy adult participants.

Figure 5

Results for wh-movement models (^**p < 0.05, FDR-corrected; ^*p < 0.05, uncorrected; ^∧p < 0.08, uncorrected).

Figure 6

Results for NP-movement models (^**p < 0.05, FDR-corrected; ^*p < 0.05, uncorrected; ^∧p < 0.08, uncorrected).