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Abstract:
Hagoort [1] suggested that the posterior temporal cortex
is involved in the retrieval of lexical frames that form
building blocks for syntactic unification, supported by
the inferior frontal gyrus (IFG). FMRI results support
the role of the IFG in the unification operations that are
performed at the structural/syntactic [2] and conceptual/
semantic levels [3]. While these studies tackle the
unification operations within linguistic components, in
the present event-related FMRI study we investigated
the interplay between sentence-level semantics and
syntax by adapting an EEG comprehension paradigm [4].
The ERP results showed typical P600 and N400 effects,
while their combined effect revealed an interaction
expressed in the N400 component ([CB-SE] - [SY-CR]
> 0). Although the N400 component was similar in the
correct and syntactic conditions (SY CR), the combined
effect was significantly larger than the effect of semantic
anomaly alone. In contrast, the size of the P600 effect
was not affected by an additional semantic violation,
suggesting an asymmetry between semantic and syntactic
processing. In the current FMRI study we characterize
this asymmetry by means of a 2x2 experimental design
included the conditions: correct (CR), syntactic (SY),
semantic (SE), and combined (CB) anomalies. Standard
SPM procedures were used for analysis and only clusters
significant at P <.05 family-wise error corrected are
reported. The main effect of semantic anomaly ([CB+SE]
> [SY+CR]) yielded activation in the anterior IFG (BA
45/47). The opposite contrast revealed the theory-ofmind
and default-mode network. The main effect of
syntactically correct sentences ([SE+CR] > [CB+SY]),
showed significant activation in the IFG (BA 44/45),
including the mid-anterior insula extending into the
superior temporal poles (BA 22/38). In addition,
significant effects were observed in medial prefrontal/
anterior cingulate cortex, posterior middle and superior
temporal regions (BA 21/22), and the basal ganglia. The
reverse contrast yielded activations in the MFG (BA
9/46), the inferior parietal region (BA 39/40), precuneus
and the posterior cingulate region. The only region
that showed a significant interaction ([CBSE]
[SYCR] > 0) was the left temporo-parietal region (BA
22/39/40). In summary, the results show that the IFG
is involved in unification during comprehension. The
effect of semantic anomaly and its implied unification
load engages the anterior IFG while the effect of syntactic
anomaly and its implied unification failure engages MFG.
Finally, the results suggest that the syntax of gender
agreement interacts with sentence-level semantics in the
left temporo-parietal region. [1] Hagoort, P. (2005). On
Broca, brain, and binding: A new framework. TICS, 9,
416-423. [2] Snijders, T. M., Vosse, T., Kempen, G., Van
Berkum, J. J. A., Petersson, K. M., Hagoort, P. (2009).
Retrieval and unification of syntactic structure in sentence
comprehension: An fMRI study using word-category
ambiguity. Cerebral Cortex, 19, 1493-1503. doi:10.1093/
cercor/bhn187. [3] Hagoort, P., Hald, L., Baastiansen, M.,
Petersson, K.M. (2004). Integration of word meaning and
world knowledge in language comprehension. Science
304, 438-441. [4] Hagoort, P. (2003). Interplay between
syntax and semantics during sentence comprehension:
ERP effects of combining syntactic and semantic
violations. Journal of Cognitive Neuroscience, 15, 883-
899.
