The neurology of syntax: language use without Broca's area.

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.

Comprehension regularity in Broca's aphasia? There's more of it than you ever imagined.

We analyze the comprehension data in Broca's aphasia, pooled together by Berndt, Mitchum, and Haendinges (1996). We show that once analyzed properly, these data have statistical structure that is very similar to that revealed by the analysis in Grodzinsky, Pinango, Zurif, and Drai (1999). The suggestion that the latter authors doctored the data to obtain a desired outcome is as false as the claim that the data in Berndt et al. show no regularity. Comprehension scores in Broca's aphasia do have statistical structure, which correlates with syntactic structure. Thus, the role of Broca's area and its vicinity in language processing can be made more precise.

The critical role of group studies in neuropsychology: comprehension regularities in Broca's aphasia.

We reexamine the empirical record of the comprehension abilities of Broca's aphasic patients. We establish clear, commonly accepted, selection criteria and obtain a pool of results. We then subject these results to a detailed statistical analysis and show that these patients comprehend certain canonical sentences (actives, subject relatives, and clefts with agentive predicates) at above-chance levels, whereas comprehension of sentences that contain deviations from canonicity (passives, object-gap relatives, and clefts) is distinct and is at chance. That the latter is the case, and patients indeed guess at such structures, we show by comparing the distribution of individual results in passive comprehension to that of a model for such guessing-an analogous series of tosses of an unbiased coin. The two distributions are virtually identical. We conclude that the group's performance is stable, and well-delineated, despite intersubject variation whose source is now identified. This means that certain comprehension tests may not always be used for the diagnosis of individual patients, but they do characterize the group. It also means that group studies are not just a valid option in neuropsychology; they are a must, since demonstrations like ours indiciate very clearly that single-case studies may be misleading. As we show, the findings from any one patient, without the context of a group, may give a distorted picture of the pathological reality. Our conclusions thus promote studies of groups of brain-damaged patients as a central tool for the investigation of brain/behavior relations.

The neurology of empty categories aphasics' failure to detect ungrammaticality.

A direct investigation into the grammatical abilities of Broca's and Wernicke's aphasics sought to obtain critical evidence for a revised model of the functional neuroanatomy of language. We examined aphasics' ability to make grammaticality judgments on a set of theoretically selected, highly complex syntactic structures that involve, most prominently, fine violations of constraints on syntactic movement. Although both groups have been thought to possess intact abilities in this domain, we discovered severe deficits; Broca's and Wernicke's aphasics (whose performances differed) exhibited clear, delineated, and grammatically characterizable deficits - they follow from the Trace-Deletion Hypothesis, which is motivated by independent comprehension results. These conclusions have both linguistic and neurological implications; Linguistically, they show that the aphasic deficit interacts with more than one module of the grammar. Namely, it manifests not only when the thematic module is called for in interpretive tasks but also when constraints on syntactic movement are tapped in a study of judgment. Neurologically, the results support a view of receptive grammatical mechanisms in the left cortex, which is functionally more restrictive than currently assumed; neuroanatomically, however, it is more distributed.

Tense and agreement in agrammatic production: pruning the syntactic tree.

This paper discusses the description of agrammatic production focusing on the verbal inflectional morphology. Agrammatism in Hebrew is investigated through an experiment with a patient who displays a highly selective impairment: agreement inflection is completely intact, but tense inflection, use of copula, and embedded structures are severely impaired. A retrospective examination of the literature shows that our findings are corroborated by others. A selective account of the agrammatic production deficiency is proposed, according to which only a subclass of the functional syntactic categories is impaired in this syndrome. The consequence of this deficit is the pruning of the syntactic phrase marker of agrammatic patients, which impairs performance from the impaired node and higher. These findings also bear upon central issues in linguistic theories, particularly that of Pollock (1989), regarding split inflection.

Trace deletion, theta-roles, and cognitive strategies.

This paper reports a rather striking distinction found in the performance of agrammatic patients: Their comprehension deficit distinguishes not only different syntactic constructions, but also verbs with different thematic structure. Thus, the coupling of a variety of sentence types with different verb types yields surprising performance patterns, demonstrating once again that the deficit these patients suffer from is highly selective from a grammatical viewpoint. This pattern of selectivity has important implications for linguistic theory, for it describes an error pattern that can be accounted for only by a theory that assumes a (normal) lexicon that encodes thematic labels and refers to a thematic hierarchy. In addition, the results argue for the necessity of a cognitive strategy (first NP = Agent) as part of the structural account of agrammatic comprehension (the Trace-Deletion Hypothesis). It is shown that, contrary to some recent claims, an account lacking such a strategy cannot derive agrammatic performance patterns properly. New data are presented, from an experiment that used an anagram task to test agrammatic comprehension of active and passive sentences containing verbs of three different thematic types. Verbs varied in that their external argument was Agent, Instrument, or Experiencer. The finding was that on all active sentences, performance was above chance, whereas on the passives, performance split: on verbs with Agent or Instrument external arguments, performance was at chance, corroborating previous findings. On Experiencer verbs, though, performance was below chance. These data argue decisively for the TDH as originally presented, namely, for an account that assumes trace deletion, coupled with a strategy. The implications of these results to the theory of brain/language relations are discussed, in the context of the theory of lexical representation.

A restrictive theory of agrammatic comprehension.

In this paper I propose a new, restrictive theory of Trace-Deletion in agrammatism. This theory subsumes the Trace-Deletion Hypothesis (TDH; Grodzinsky, 1984a,b, 1986, 1990), which maintains that traces are deleted from agrammatic representations and that a cognitive strategy augments the patients' performance. This claim accounts for the pattern of loss and sparing observed in these patients' comprehension of a wide variety of syntactic constructions and is thus important for our understanding of the neural representation of syntax. Yet there are reasons for revising the account and making it more precise, stemming from both recent empirical findings and new developments in the theory of syntax. The original TDH was based on observations of agrammatic comprehension of structures containing traces resulting from either NP- or Wh-movement. Nevertheless, heads (as opposed to phrasal projections) also move and leave traces behind. Head movement (of verbs, for instance) has come to play a central role in linguistic theory (which currently postulates a wider variety of empty categories than any previous theoretical framework). Recent findings suggest that verb movement is retained in agrammatism, indicating that a sweeping claim regarding the deletion of all empty categories is too strong. This motivates the first restrictive move, resulting in a theory that picks out a restricted set of traces--only those for which deficient performance is indeed observed. All other empty categories are left intact. Trace-Deletion is tied to theta-positions. The second restrictive move is motivated by two types of surprising asymmetries that have recently been discovered for agrammatic comprehenders: First, agrammatic comprehension on passives of psychological predicates provides an error pattern that distinguishes this construction from agentive passive, indicating that the deficit is tied to the thematic properties of the predicate: Second, asymmetries have been observed in agrammatic comprehension of questions and quantifiers. These findings motivate a modification of the augmentative strategy, whose domain of application is restricted to referential NPs. Thus, the new account amounts to the claim that only traces in theta-positions are deleted, and that the strategy applies to referential NPs alone. This, I argue, not only derives all the data precisely but is also conceptually superior to any previous account of agrammatism. Finally, I discuss the consequences of this account to linguistic theory, and to theories of brain/language relations.

There is an entity called agrammatic aphasia.

Agrammatism as a phenomenon of neuropsychological relevance has been recently attacked--from conceptual and empirical angles. This article examines the facts, as they emerge from three recent experimental studies that have concluded that agrammatism does not exist (Miceli et al., 1989; Martin et al., 1989, Badecker et al., in press), and draws the opposite conclusion: that agrammatism is of interest to students of language and that patients belonging in this clinical category also reveal uniform patterns of aberrant behavior that are of great linguistic and psycholinguistic relevance.

Agrammatic comprehension of relative clauses.

Four hypotheses that attempt to account for the comprehension deficit in agrammatism are put to an empirical test. The interest in them is in that they all view the deficit as highly selective. The first, proposed by D. Caplan and C. Futter (1986, Brain and Language, 27, 117-134), argues that agrammatic patients cannot carry out normal syntactic analysis beyond the category label of each incoming lexical item and are reduced to the use of a cognitive strategy that commends assignment of thematic roles to noun phrases merely by their linear position in the string. A second, less radical hypothesis (Y. Grodzinsky, 1986a, Brain and Language, 27, 135-159), accounts for the deficit differently, by deleting a particular kind of syntactic object (trace) from the otherwise normal representation, and augmenting the resulting, underspecified representation by a strategy, whose use is quite restricted. A third account that is tested contends that agrammatic aphasics fail to comprehend perceptually complex constructions, where the metric for complexity is determined by results obtained from comprehension tests of normal listeners. The fourth account (M. F. Schwartz, M. C. Linebarger, E. M. Saffran, and D. S. Pate, 1987, Language and Cognitive Processes, 2, 85-113) argues that the thematic transparency of a construction (whether or not thematic roles are assigned directly to positions) is the best predictor of the manner by which agrammatics can handle it. An empirical test is thus constructed, both to extend the evidential basis concerning the comprehension skills of these patients and to distinguish between the accounts. Four types of relative clauses are presented to the patients, where embedding type (center vs. right) is one variable, and location of gap (subject vs. object position) is the other. The patients are tested in a sentence-picture matching paradigm. The finding, that is rather robust, is that gap location is the best predictor of agrammatic performance: the patients perform well above chance on both types of subject gap relatives, and at chance levels on object gaps. It is then shown that the Trace-Deletion Hypothesis (Grodzinsky, 1986a) is the only one among the accounts considered that is compatible with these data.

Syntactic representations in agrammatic aphasia: the case of prepositions.

The focus of this paper is the syntactic deficit in agrammatic aphasia. The specific issue is the extent to which prepositions are impaired in this syndrome. This category is of particular interest because of the unique role its members play in the grammar. This is the organization of the paper: First, several descriptive generalizations are examined critically, and arguments against them are advanced. Then, a new hypothesis is formulated, stated in terms of current linguistic theory. This hypothesis views the deficit as being partial from a syntactic point of view. The relevant notion to account for the data (i.e., partitioning the impaired from preserved prepositions) is Government, a structural relation that must hold between the preposition at issue and the verb. The consequences of this hypothesis are derived, and an experiment that was conducted to test them is reported. The findings of this experiment not only support the hypothesis, but also suggest that the impairment is unique to agrammatic aphasic patients, since the performance of a control group of fluent aphasics was different. Finally, several theoretical issues are discussed in light of the findings and of the proposed description of the agrammatic deficit.

Language deficits and the theory of syntax.

A new structural account of agrammatism is proposed, which analyzes the deficit in terms of one current theory of syntax. First, the motivation for accounts of this kind is given. Then, a variety of experimental findings from sentence comprehension in agrammatism are examined and accounted for in a unified way. It is shown that a minimal change in the syntactic model (achieved by imposing a special condition on a construct called trace), results in a model which accounts for all the data at hand. A number of possible objections to this proposal is then examined, and reasons are given to dismiss these objections. Also, it is shown that this proposal is preferable to other structural accounts which have been recently proposed. Finally, the empirical consequences of this account are discussed, with a special emphasis on the implications for models of language processing.