A new view of the functional role of the left anterior cortex in language use is proposed. The experimental record indicates that most human linguistic 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, implicated in Broca's aphasia, does have a role in syntactic processing, but a highly specific one: It is the neural home to receptive mechanisms involved in the computation of the relation between transformationally moved phrasal constituents and their extraction sites (in line with the Trace-Deletion Hypothesis). It is also involved in the construction of higher parts of the syntactic tree in speech production. By contrast, basic combinatorial capacities 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 from several language types are pooled and scrutinized comparatively), grammaticality and plausibility judgments, real-time processing of complex sentences, and rehabilitation. Also discussed are recent results from functional neuroimaging and from structured observations on speech production of Broca's aphasics. Syntactic abilities are nonetheless distinct from other cognitive skills and are represented entirely and exclusively in the left cerebral hemisphere. Although more widespread in the left hemisphere than previously thought, they are clearly distinct from other human combinatorial and intellectual abilities. The neurological record (based on functional imaging, split-brain and right-hemisphere-damaged patients, as well as patients suffering from a breakdown of mathematical skills) indicates that language is a distinct, modularly organized neurological entity. Combinatorial aspects of the language faculty reside in the human left cerebral hemisphere, but only the transformational component (or algorithms that implement it in use) is located in and around Broca's area.

Grodzinsky's hypotheses need different theories of grammar for comprehension and for production. These predictions are undesirable. Hungarian data are incompatible with the Trace Deletion Hypothesis.

An important part of Grodzinsky's claim regarding the neurology of syntax depends on agrammatic data partitioned by the Trace Deletion Hypothesis (TDH), which is a combination of trace-deletion and default strategy. However, there is convincing evidence that the default strategy is consistently avoided by agrammatics. The TDH, therefore, is in no position to support claims about agrammatic data or the neurology of syntax.

This commentary discusses the relation between Grodzinsky's target article and Friederici's (1995) model of syntactic processing. The two models can be made more compatible if it is assumed that people with Broca's aphasia have a problem in trace construction rather than trace deletion, and that the process of trace construction takes place during the second early syntactic substage of Friederici's model.

The argument that Broca's area is preferentially involved in specific syntactic operations is based on a strong assertion regarding patterns of sentence comprehension found among patients with Broca's aphasia. This assertion is shown to be largely inconsistent with the available evidence from published studies, which indicates that only a subgroup of Broca patients demonstrate the target pattern.

Despite problems with statistical significance, ancillary hypotheses, and integration into an overall view of cognition, Grodzinsky's demotion of Broca's area to a mechanism for tracking moved constituents is intrinsically plausible and fits a realistic picture of how syntax works.

Data from published case and group studies bear on the trace deletion hypothesis. The deficit-lesion correlational literature does not support Grodzinsky's claim that lesions in and around Broca's area inevitably lead to comprehension deficits specifically related to coindexation of traces or his claim that other lesions spare this function.

Three types of problems are raised in this commentary: On the linguistic side, we emphasize the importance of an appropriate definition of the different domains of linguistics. This is needed to define the domains (lexicon-syntax-semantics) to which transformational relations apply. We then question the concept of Broca's aphasia as a “functional” syndrome, associated with a specific lesion. Finally, we discuss evidence from functional brain imaging. The breadth and potential impact of such evidence has grown considerably in the last few years, expanding our knowledge of the multiple contributions of the “Broca's region” to phonological, lexical-semantic, and syntactic processing. “Lumping” under diagnostic labels, such as Broca's aphasia, should be replaced by more detailed linguistic and neurological descriptions of the clinical cases.

Grodzinsky associates Broca's area with three kinds of deficit, relating to articulation, comprehension (involving trace deletion), and production (involving “tree pruning”). Could these be special cases of one deficit? Evidence from research on language evolution suggests that they may all involve syllable structure or those aspects of syntax that evolved through exploiting the neural mechanisms underlying syllable structure.

Deficits observed in Broca's aphasia are much more general than Grodzinsky acknowledges. Broca's aphasics have a broad range of problems in lexical and morphological comprehension; furthermore, the classic “agrammatic” syntactic profile is observed over many populations. Finally, Broca's area is implicated in the performance of many linguistic and nonlinguistic tasks.

Grodzinsky's characterization of the syntactic function of Broca's area is convincing, but his argument that this transformation processing capability is specific to language is less so. Based on predictions from simulation studies of sequence learning, we report a correlation between agrammatic patients' impairments in (a) syntactic comprehension, and (b) nonlinguistic sequence transformation processing, indicating the existence of a nonlinguistic correlate of agrammatic aphasia.

Many authors assume that Broca's area subserves the functions that are lost in patients with Broca's aphasia. This commentary attempts to clarify the relationship between Broca's area and Broca's aphasia and suggests that statements about the neurology of patients' specific language functions might be better supported by their individual structural neuroimaging data.

Grodzinsky examines Broca's aphasia in terms of some specific grammatical deficits. However, his grammatical models offer no way to characterize the distinctions he observes. Rather than grammatical deficits, his patients seem to have intact grammars but defective modules of parsing and production.

We criticize the lack of neuroanatomical precision in the Grodzinsky target article. We propose a more precise neuroanatomical characterization of syntactic processing and suggest that syntactic procedures are supported by the left frontal operculum in addition to the anterior part of the superior temporal gyrus, which appears to be associated with syntactic knowledge representation.

This commentary brings further support for the Trace Deletion Hypothesis (TDH) from a new study of OVS (Object-Verb-Subject) and OSV (Object-Subject-Verb) sentences in Hebrew, which are active constructions that involve object movement but no change in morphology. The comprehension of these constructions in Broca's aphasia is impaired, and the performance is at chance level, as predicted by the TDH.

Both linguistic and empirical evidence fail to support Grodzinsky's account of Broca's aphasics' comprehension problems. We address concerns regarding Grodzinsky's referring to the internal subject hypothesis, the importance of case information in thematic role assignment, the processing of passives, and the adequacy of Grodzinsky's linear strategy.

Grodzinsky's localization claim can be questioned on empirical grounds. The Trace Deletion Hypothesis fails to account for a number of comprehension facts in Broca's aphasia and conduction aphasics show similar comprehension patterns. Frontoparietal systems are recruited during sentence comprehension only under conditions of increased processing load and/or attentional demands.

There are reasons for reservations with respect to the postulated function of Broca's area. Evidence for the psychological reality of the relevant traces does not exist. In addition, because the syntax of non- (or partly) configurational languages is not described in terms of empty categories, no receptive agrammatism should be observed in these languages. Aphasia should not be examined in isolation from its cognitive components.

The data provided by Grodzinsky demonstrating a syntactic comprehension deficit in Broca's patients provide no evidence for the theoretical concepts of movement, trace or “trace deletion.” The comprehension deficit data can be more economically accounted for with traditional grammatical concepts that are less theory-internal and more empirically based.

Grodzinsky interprets linguistic differences between agrammatic comprehension and production symptoms as supporting the hypothesis that the mechanisms underlying grammatical encoding (sentence formulation) and grammatical decoding (syntactic parsing) are at least partially distinct. This inference is shown to be premature. A range of experimentally established similarities between the encoding and decoding processes is highlighted, testifying to the viability of the hypothesis that receptive and productive syntactic tasks are performed by the same syntactic processor.