Dissociable patterns of brain activity during comprehension of rapid and syntactically complex speech: Evidence from fMRI Jonathan E. Peelle, a Corey McMillan, b Peachie Moore, b Murray Grossman, b and Arthur Wingfield a, * a Volen National Center for Complex Systems, Brandeis University, Waltham, MA, USA b Department of Neurology, University of Pennsylvania, Philadelphia, PA, USA Accepted 11 May 2004 Available online 24 June 2004 Abstract Sentence comprehension is a complex task that involves both language-specific processing components and general cognitive resources. Comprehension can be made more difficult by increasing the syntactic complexity or the presentation rate of a sentence, but it is unclear whether the same neural mechanism underlies both of these effects. In the current study, we used event-related functional magnetic resonance imaging (fMRI) to monitor neural activity while participants heard sentences containing a subject- relative or object-relative center-embedded clause presented at three different speech rates. Syntactically complex object-relative sentences activated left inferior frontal cortex across presentation rates, whereas sentences presented at a rapid rate recruited frontal brain regions such as anterior cingulate and premotor cortex, regardless of syntactic complexity. These results suggest that disso- ciable components of a large-scale neural network support the processing of syntactic complexity and speech presented at a rapid rate during auditory sentence processing. Ó 2004 Elsevier Inc. All rights reserved. Keywords: Sentence comprehension; Syntax; Speech rate; Language; Time-compressed speech; Brain imaging; Processing speed; fMRI 1. Introduction Unlike reading, in which input rate can be controlled with eye movements, speech comprehension is based on a transient acoustic signal whose rate is largely con- trolled by the talker, not the listener. For effective comprehension auditory input must be analyzed, seg- mented, and processed for structure and meaning, all while new information continues to arrive. The speed at which these processes must occur is necessarily rapid, as average speaking rates can exceed 200 words per minute (wpm) even in everyday conversation (Miller, Grosjean, & Lomanto, 1984). A number of studies have used time-compressed speech to examine the effects of presentation rate on auditory sentence comprehension. These studies typi- cally use a computer algorithm that periodically deletes small segments of the speech signal and then abuts the remaining segments in time. The discarded intervals are always kept to the same small size, with the rate of speech controlled by the frequency with which these segments are deleted. The resulting speech retains its normal pitch and relative prosodic features but is re- produced in less than its original speaking time (Foulke, 1971). Studies using time-compressed speech have shown that, depending on the original speaking rate and the nature of the speech materials, speech can still be understood fairly well when reduced by as much as 50%, although comprehension accuracy generally declines incrementally as speech rate is increased (Chodorow, 1979; Foulke, 1971; Wingfield, 1975; Wingfield, Tun, Koh, & Rosen, 1999). In a previous study we showed that the added work imposed by complex syntactic structure is compounded by the processing challenge of rapid speech, producing a differentially greater effect of syntactic complexity on sentence comprehension at faster speech rates * Corresponding author. Fax: 1-781-736-3275. E-mail address: wingfield@brandeis.edu (A. Wingfield). 0093-934X/$ - see front matter Ó 2004 Elsevier Inc. All rights reserved. doi:10.1016/j.bandl.2004.05.007 Brain and Language 91 (2004) 315–325 www.elsevier.com/locate/b&l