All it takes is a face-to-face conversation in a noisy environment to realize that viewing a speaker's lip movements contributes to speech comprehension. What are the processes underlying the perception and interpretation of visual speech? Brain areas that control speech production are also recruited during lipreading. This finding raises the possibility that lipreading may be supported, at least to some extent, by a covert unconscious imitation of the observed speech movements in the observer's own speech motor system—a motor simulation. However, whether, and if so to what extent, motor simulation contributes to visual speech interpretation remains unclear. In two experiments, we found that several participants with congenital facial paralysis were as good at lipreading as the control population and performed these tasks in a way that is qualitatively similar to the controls despite severely reduced or even completely absent lip motor representations. Although it remains an open question whether this conclusion generalizes to other experimental conditions and to typically developed participants, these findings considerably narrow the space of hypothesis for a role of motor simulation in lipreading. Beyond its theoretical significance in the field of speech perception, this finding also calls for a re-examination of the more general hypothesis that motor simulation underlies action perception and interpretation developed in the frameworks of motor simulation and mirror neuron hypotheses.

This research studies the neural systems underlying two integration processes that take place during natural discourse comprehension: consistency evaluation and passive comprehension. Evaluation was operationalized with a consistency judgment task and passive comprehension with a passive listening task. Using fMRI, the experiment examined the integration of incoming sentences with more recent, local context and with more distal, global context in these two tasks. The stimuli were stories in which we manipulated the consistency of the endings with the local context and the relevance of the global context for the integration of the endings. A whole-brain analysis revealed several differences between the two tasks. Two networks previously associated with semantic processing and attention orienting showed more activation during the judgment than the passive listening task. A network previously associated with episodic memory retrieval and construction of mental scenes showed greater activity when global context was relevant, but only during the judgment task. This suggests that evaluation, more than passive listening, triggers the reinstantiation of global context and the construction of a rich mental model for the story. Finally, a network previously linked to fluent updating of a knowledge base showed greater activity for locally consistent endings than inconsistent ones, but only during passive listening, suggesting a mode of comprehension that relies on a local scope approach to language processing. Taken together, these results show that consistency evaluation and passive comprehension weigh differently on distal and local information and are implemented, in part, by different brain networks.

Reading an action verb elicits the retrieval of its associated body movements as well as its typical goal—the outcome to which it is directed. Two fMRI experiments are reported in which retrieval of goal attributes was isolated from retrieval of motoric ones by contrasting actions that are either done intentionally (e.g., drink) and thus have associated goal information or by accident (e.g., hiccup). Orthogonally, the actions also varied in their motoricity (e.g., drink vs. imagine). Across both levels of motoricity, goal-directedness influenced the activity of a portion of left posterior inferior parietal lobe (pIPL). These effects were not explicable by the grammatical properties, imageability, or amount of body movement associated with these different types of verbs. In contrast, motoricity (across levels of goal-directedness) activated primarily the left middle temporal gyrus. Furthermore, pIPL was found to be distinct from the portion of left parietal lobe implicated in theory of mind, as localized in the same participants. This is consistent with the observation that pIPL contains many functionally distinct subregions and that some of these support conceptual knowledge. The present findings illustrate that, in particular, the pIPL is involved in representing attributes of intentional actions, likely their typical goals, but not their associated body movements. This result serves to describe an attribute-selective semantic subsystem for at least one type of nonmotor aspect of action knowledge.

Verbs and nouns are fundamental units of language, but their neural instantiation remains poorly understood. Neuropsychological research has shown that nouns and verbs can be damaged independently of each other, and neuroimaging research has found that several brain regions respond differentially to the two word classes. However, the semantic–lexical properties of verbs and nouns that drive these effects remain unknown. Here we show that the most likely candidate is predication: a core lexical feature involved in binding constituent arguments ( boy , candies ) into a unified syntactic–semantic structure expressing a proposition ( the boy likes the candies ). We used functional neuroimaging to test whether the intrinsic “predication-building” function of verbs is what drives the verb–noun distinction in the brain. We first identified verb-preferring regions with a localizer experiment including verbs and nouns. Then, we examined whether these regions are sensitive to transitivity—an index measuring its tendency to select for a direct object. Transitivity is a verb-specific property lying at the core of its predication function. Neural activity in the left posterior middle temporal and inferior frontal gyri correlates with transitivity, indicating sensitivity to predication. This represents the first evidence that grammatical class preference in the brain is driven by a word's function to build predication structures.

Previous studies have provided evidence for a tool-selective region in left lateral occipitotemporal cortex (LOTC). This region responds selectively to pictures of tools and to characteristic visual tool motion. The present human fMRI study tested whether visual experience is required for the development of tool-selective responses in left LOTC. Words referring to tools, animals, and nonmanipulable objects were presented auditorily to 14 congenitally blind and 16 sighted participants. Sighted participants additionally viewed pictures of these objects. In whole-brain group analyses, sighted participants showed tool-selective activity in left LOTC in both visual and auditory tasks. Importantly, virtually identical tool-selective LOTC activity was found in the congenitally blind group performing the auditory task. Furthermore, both groups showed equally strong tool-selective activity for auditory stimuli in a tool-selective LOTC region defined by the picture-viewing task in the sighted group. Detailed analyses in individual participants showed significant tool-selective LOTC activity in 13 of 14 blind participants and 14 of 16 sighted participants. The strength and anatomical location of this activity were indistinguishable across groups. Finally, both blind and sighted groups showed significant resting state functional connectivity between left LOTC and a bilateral frontoparietal network. Together, these results indicate that tool-selective activity in left LOTC develops without ever having seen a tool or its motion. This finding puts constraints on the possible role that this region could have in tool processing and, more generally, provides new insights into the principles shaping the functional organization of OTC.

Exact computation of numerosity requires the selective individuation of the elements to be enumerated so that each element is counted once and only once. Such a mechanism should operate not only when the elements to be enumerated are presented in isolation but also when they are presented in cluttered scenes. To uncover the electrophysiological correlates of the level of object representation necessary for exact enumeration, we examined ERP measures during the execution of a target enumeration task. A variable number (1–4) of lateralized targets were presented with or without distracters on the target side. An early nonlateralized response (N1, 120–180 msec) was modulated by target numerosity only when presented without distracters. By contrast, the amplitudes of a lateralized and later response (N2pc, 180–300 msec) increased as a function of target numerosity both with and without distracters, reaching a plateau at three targets. We propose that the stage of processing reflected in the N2pc corresponds to the component of individuation that binds specific indexes to properties and locations and that this provides the representation type necessary for exact enumeration.

Verbs and nouns differ not only on formal linguistic grounds but also in what they typically refer to: Verbs typically refer to actions, whereas nouns typically refer to objects. Prior neuroimaging studies have revealed that regions in the left lateral temporal cortex (LTC), including the left posterior middle temporal gyrus (pMTG), respond selectively to action verbs relative to object nouns. Other studies have implicated the left pMTG in action knowledge, raising the possibility that verb selectivity in LTC may primarily reflect action-specific semantic features. Here, using functional neuroimaging, we test this hypothesis. Participants performed a simple memory task on visually presented verbs and nouns that described either events (e.g., “he eats” and “the conversation”) or states (e.g., “he exists” and “the value”). Verb-selective regions in the left pMTG and the left STS were defined in individual participants by an independent localizer contrast between action verbs and object nouns. Both regions showed equally strong selectivity for event and state verbs relative to semantically matched nouns. The left STS responded more to states than events, whereas there was no difference between states and events in the left pMTG. Finally, whole-brain group analysis revealed that action verbs, relative to state verbs, activated a cluster in pMTG that was located posterior to the verb-selective pMTG clusters. Together, these results indicate that verb selectivity in LTC is independent of action representations. We consider other differences between verbs and nouns that may underlie verb selectivity in LTC, including the verb property of predication.

Neuropsychological evidence has highlighted the role of the anterior temporal lobes in the processing of conceptual knowledge. That putative role is only beginning to be investigated with fMRI as methodological advances are able to compensate for well-known susceptibility artifacts that affect the quality of the BOLD signal. In this article, we described differential BOLD activation for pictures of animals and manipulable objects in the anterior temporal lobes, consistent with previous neuropsychological findings. Furthermore, we found that the pattern of BOLD signal in the anterior temporal lobes is qualitatively different from that in the fusiform gyri. The latter regions are activated to different extents but always above baseline by images of the preferred and of the nonpreferred categories, whereas the anterior temporal lobes tend to be activated by images of the preferred category and deactivated (BOLD below baseline) by images of the nonpreferred category. In our experimental design, we also manipulated the decision that participants made over stimuli from the different semantic categories. We found that in the right temporal pole, the BOLD signal shows some evidence of being modulated by the task that participants were asked to perform, whereas BOLD activity in more posterior regions (e.g., the fusiform gyri) is not modulated by the task. These results reconcile the fMRI literature with the neuropsychological findings of deficits for animals after damage to the right temporal pole and suggest that anterior and posterior regions within the temporal lobes involved in object processing perform qualitatively different computations.

Neuropsychological and neurophysiological studies suggest that the production of verbs in speech depends on cortical regions in the left frontal lobe. However, the precise topography of these regions, and their functional roles in verb production, remains matters of debate. In an earlier study with repetitive transcranial magnetic stimulation (rTMS), we showed that stimulation to the left anterior midfrontal gyrus disrupted verb production, but not noun production, in a task that required subjects to perform simple morphological alternations. This result raises a number of questions: for example, is the effect of stimulation focal and specific to that brain region? Is the behavioral effect limited to rule-based, regular transformations, or can it be generalized over the grammatical category? In the present study, we used rTMS to suppress the excitability of distinct parts of the left prefrontal cortex to assess their role in producing regular and irregular verbs compared to nouns. We compared rTMS to sham stimulation and to stimulation of homologous areas in the right hemisphere. Response latencies increased for verbs, but were unaffected for nouns, following stimulation to the left anterior midfrontal gyrus. No significant interference specific for verbs resulted after stimulation to two other areas in the left frontal lobe, the posterior midfrontal gyrus and Broca's area. These results therefore reinforce the idea that the left anterior midfrontal cortex is critical for processing verbs. Moreover, none of the regions stimulated was preferentially engaged in the production of regular or irregular inflection, raising questions about the role of the frontal lobes in processing inflectional morphology.

A number of researchers have proposed that the premotor and motor areas are critical for the representation of words that refer to actions, but not objects. Recent evidence against this hypothesis indicates that the left premotor cortex is more sensitive to grammatical differences than to conceptual differences between words. However, it may still be the case that other anterior motor regions are engaged in processing a word's sensorimotor features. In the present study, we used singleand paired-pulse transcranial magnetic stimulation to test the hypothesis that left primary motor cortex is activated during the retrieval of words (nouns and verbs) associated with specific actions. We found that activation in the motor cortex increased for action words compared with non-action words, but was not sensitive to the grammatical category of the word being produced. These results complement previous findings and support the notion that producing a word activates some brain regions relevant to the sensorimotor properties associated with that word regardless of its grammatical category.

A longitudinal study of oral and written naming and comprehension of nouns and verbs in an individual (M. M. L.) with nonfluent primary progressive aphasia (PPA) is reported. M. M. L. showed progressive deterioration of oral naming of verbs well before deterioration of written naming of verbs and before deterioration of oral or written naming of nouns. Her comprehension of both nouns and verbs remained intact, at least relative to oral naming of verbs. Her performance is compared to that of two other individuals with nonfluent PPA, who were tested at two time points. These patients showed similar patterns with respect to grammatical word class (verbs more impaired than nouns) and modality (spoken production more impaired than written production), but somewhat different courses of deterioration. The modality-specific nature of the observed verb production deficits rules out a semantic locus for the grammatical class effects. The results provide a new source of evidence for the hypothesis that there are distinct neural mechanisms for accessing lexical representations of nouns and verbs in language production.

In an fMRI experiment, subjects saw a written noun and made three distinct decisions in separate sessions: Is its grammatical gender masculine or feminine (grammatical feature task)? Is it an animal or an artifact (semantic task)? Does it contain a /tch/ or a /k/ sound (phonological task)? Relative to the other experimental conditions, the grammatical feature task activated areas of the left middle and inferior frontal gyrus and of the left middle and inferior temporal gyrus. These activations fit in well with neuropsychological studies that document the correlation between left frontal lesions and damage to morphological processes in agrammatism, and the correlation between left temporal lesions and failure to access lexical representations in anomia. Taken together, these data suggest that grammatical gender is processed in a left fronto-temporal network. In addition, the observation that the grammatical feature task and the phonology task activated neighboring but distinct regions of the left frontal lobe provides a plausible neuroanatomical basis for the systematic occurrence of phonological errors in aphasic subjects with morphological deficits.

Selective deficits in producing verbs relative to nouns in speech are well documented in neuropsychology and have been associated with left hemisphere frontal cortical lesions resulting from stroke and other neurological disorders. The basis for these impairments is unresolved: Do they arise because of differences in the way grammatical categories of words are organized in the brain, or because of differences in the neural representation of actions and objects? We used repetitive transcranial magnetic stimulation (rTMS) to suppress the excitability of a portion of left prefrontal cortex and to assess its role in producing nouns and verbs. In one experiment subjects generated real words; in a second, they produced pseudowords as nouns or verbs. In both experiments, response latencies increased for verbs but were unaffected for nouns following rTMS. These results demonstrate that grammatical categories have a neuroanatomical basis and that the left prefrontal cortex is selectively engaged in processing verbs as grammatical objects.

We claim that the animate and inanimate conceptual categories represent evolutionarily adapted domain-specific knowledge systems that are subserved by distinct neural mechanisms, thereby allowing for their selective impairment in conditions of brain damage. On this view, (some of) the category-specific deficits that have recently been reported in the cognitive neuropsychological literature—for example, the selective damage or sparing of knowledge about animals—are truly categorical effects. Here, we articulate and defend this thesis against the dominant, reductionist theory of category-specific deficits, which holds that the categorical nature of the deficits is the result of selective damage to noncategorically organized visual or functional semantic subsystems. On the latter view, the sensory/functional dimension provides the fundamental organizing principle of the semantic system. Since, according to the latter theory, sensory and functional properties are differentially important in determining the meaning of the members of different semantic categories, selective damage to the visual or the functional semantic subsystem will result in a category-like deficit. A review of the literature and the results of a new case of category-specific deficit will show that the domain-specific knowledge framework provides a better account of category-specific deficits than the sensory/functional dichotomy theory.

We report the case of an Italian anomic subject who was invariably able to provide the auxiliary of verbs he failed to produce in oral naming tasks. This pattern of performance contrasts with that of another Italian-speaking patient documented by Miceli and Caramazza (1988) who showed a selective impairment in accessing syntactic features of words, but not their phonological forms. This double dissociation suggests that syntactic and phonological information in the lexicon are accessed independently and represented in distinct neural structures.

We report detailed analyses of the performance of a patient, DHY, who as a consequence of strokes in the left occipital lobe and the periventricular white matter in the region of the spleniuni, showed severely impaired naming of visual stimuli despite spared recognition of visual stimuli and spared naming in other modalities. This pattern of performance—labeled “optic aphasia”—has been previously interpreted as support for the hypothesis that there are independent semantic systems, either a visual and a verbal semantic store (Beauvois, 1982; Lhermitte & Beauvois, 1973) or a right hemisphere and a left hemisphere semantic system (Coslett & Saffran, 1989, l092), which are “disconnected” in these patients. We provide evidence that DHY shows precisely the types of performance across a variety of verbal and visual tasks that have been used to support these claims of separate semantic systems: (1) good performance in naming to definition and naming objects presented for tactile exploration (which has been interpreted as evidence of spared verbal or left hemisphere semantic processing), and (2) good performance on various “semantic” tasks that do not require naming (which has been interpreted as access to spared visual or right hemisphere semantic processing). Nevertheless, when nonverbal semantic tasks were modified such that they required access to more detailed semantic information for accurate performance, DHY was Par less accurate, indicating that she did not access complete semantic information about objects in the visual modality. We argue that these data undermine the claim that cases of optic aphasia can be explained only by proposing multiple semantic systems. We propose an alternative account for this pattern of performance, within a model of visual object naming that specifies a single, modality-independent semantic system. We show that the performance of DHY and other “optic aphasic” patients can be explained by proposing a deficit in accessing a complete, modality-independent, lexical-semantic representation from an intact stored, structural description of the object. We discuss the implications of these conclusions for claims about the neuroanatomical correlates of semantic and visual object processing.

We report the performance of a patient who, as a consequence of left frontal and temporoparietal strokes, makes far more errors on nouns than on verbs in spoken output tasks, but makes far more errors on verbs than on nouns in written input tasks. This double dissociation within a single patient with respect to grammatical category provides evidence for the hypothesis that phonological and orthographic representations of nouns and verbs are processed by independent neural mechanisms. Furthermore, the opposite dissociation in the verbal output modality, an advantage for nouns over verbs in spoken tasks, by a different patient using the same stimuli has also been reported (Caramazza & Hillis, 1991). This double dissociation across patients on the same task indicates that results cannot be ascribed to "greater difficulty" with one type of stimulus, and provides further evidence for the view that grammatical category information is an important organizational principle of lexical knowledge in the brain.

Cognitive neuropsychology's domain of inquiry concerns the structure of normal perceptual, motor, and cognitive processes. As such, it constitutes a branch of cognitive science. Cognitive neuropsychology differs from other branches of cognitive science only by the type of observation that it uses in developing and evaluating theories of normal cognition. The data used in cognitive neuropsychology are the patterns of performance produced by brain-damged subjects . Because the basic data used in cognitive neuropsychology are the result of a biological manipulation—a brain lesion—these data will be relevant to claims about the functional organization of the brain. Hence, cognitive neuropsychology may also be considered to be a branch of cognitive neuroscience. However, in this paper I will be concerned with an assessment of research programs whose principal or only aim is to constrain theories of normal cognitive functioning through the analysis of acquired disorders of cognition. Following a brief discussion of the basic assumptions that motivate cognitive neuropsychological research, I consider Kosslyn and Van Kleeks (1990) claim that the study of brain-damaged subjects for the purpose of constraining theories of normal cognitive processing cannot lead to meaningful conclusions unless the theories are directly cast in terms of anatomical and physiological facts. I argue that these authors conflated criticisms that may apply to any empirical science with criticisms that may apply specifically to cognitive neuropsychology. Separate consideration of the criticisms specific to cognitive neuropsychology reveals that these are unfounded. The main point of this discussion is to emphasize the pragmatic character of the motivation for using impaired performance to constrain theories of normal cognition. The usefulness of cognitive neuropsychological research is illustrated through specific examples.