The neurology of syntax: Language use without Broca's area

A new view of the functional role of the left anterior cortex in language u se is proposed. The experimental record indicates that most human linguisti c abilities are not localized in this region. In particular, most of syntax (long thought to be there) is not located in Broca's area and its vicinity (operculum, insula, and subjacent white matter). This cerebral region, imp licated in Broca's aphasia, does have a role in syntactic processing, but a highly specific one: It is the neural home to receptive mechanisms involve d in the computation of the relation between transformationally moved phras al constituents and their extraction sites (in line with the Trace-Deletion Hypothesis). It is also involved in the construction of higher parts of th e syntactic tree in speech production. By contrast, basic combinatorial cap acities necessary for language processing - for example, structure-building operations, lexical insertion - are not supported by the neural tissue of this cerebral region, nor is lexical or combinatorial semantics. The dense body of empirical evidence supporting this restrictive view comes mainly from several angles on lesion studies of syntax in agrammatic Broca 's aphasia. Five empirical arguments are presented: experiments in sentence comprehension, cross-linguistic considerations (where aphasia findings fro m several language types are pooled and scrutinized comparatively), grammat icality and plausibility judgments, real-time processing of complex sentenc es, and rehabilitation, Also discussed are recent results from functional n euroimaging and from structured observations on speech production of Broca' s aphasics. Syntactic abilities are nonetheless distinct from other cognitive skills an d are represented entirely and exclusively in the left cerebral hemisphere. Although mole widespread in the left hemisphere than previously thought, t hey are clearly distinct from other human combinatorial and intellectual ab ilities. The neurological record (based on functional imaging, split-brain and light hemisphere-damaged patients, as well as patients suffering from a breakdown of mathematical skills) indicates that language is a distinct, m odularly organized neurological entity. Combinatorial aspects of the langua ge faculty reside in the human left cerebral hemisphere, but only the trans formational component (or algorithms that implement it in use) is located i n and around Broca's area.