David P. Corina

Sentence reading: A functional mri study at 4 tesla

In this study, changes in blood oxygenation and volume were monitored while monolingual right-handed subjects read English sentences. Our results confirm the role of the left peri-sylvian cortex in language processing. Interestingly, individual subject analyses reveal a pattern of activation characterized by several small, limited patches rather than a few large, anatomically well-circumscribed centers. Between-subject analyses confirm a lateralized pattern of activation and reveal active classical language areas including Brocas area, Wernickes area, and the angular gyms. In addition they point to areas only more recently considered as language-relevant including the anterior portion of the superior temporal sulcus. This area has not been reliably observed in imaging studies of isolated word processing. This raises the hypothesis that activation in this area is dependent on processes specific to sentence reading.

Lexical Recognition in Sign Language: Effects of Phonetic Structure and Morphology

Two experiments are reported which investigate lexical recognition in American Sign Language (ASL). Exp. 1 examined identification of monomorphemic signs and investigated how the manipulation of phonological parameters affected sign identification. Over-all sign identification was much faster than what has been found for spoken language The phonetic structure of sign (the simultaneous availability of Handshape and Location information) and the phonotactics of the ASL lexicon are argued to account for this difference. Exp. 2 compared the time course of recognition for monomorphemic and morphologically complex signs. ASL morphology is largelv nonconcatenative which raises particularly interesting questions for word recognition We found that morphologically complex signs had longer identification times than matched monomorphemic signs. Also, although roots and affixes are often articulated simultaneously in ASL, they were not identified simultaneously. Base forms of morphologically complex signs were identified initially followed by recognition of the morphological inflection. Finally, subjects with deaf parents (Native signers) were able to isolate signs faster than subjects with hearing parents (Late signers). This result suggests that early language experience can influence the initial stages of lexical access and sign identification.

Dissociation between linguistic and nonlinguistic gestural systems: A case for compositionality ☆

This paper addresses the issue of the separability of disorders of sign language from disorders of gesture and pantomime. The study of a left-lesioned deaf signer presents one of the most striking examples to date of the cleavage between linguistic signs and manual pantomime. The left-hemisphere lesion produced a marked sign language aphasia disrupting both the production and the comprehension of sign language. However, in sharp contrast to the breakdown of sign language, the ability to communicate in nonlinguistic gesture was remarkably spared. This case has important implications for our understanding of the neural mediation of language and gesture. We argue that the differences observed in the fractionation of linguistic versus nonlinguistic gesture reflect differing degrees of compositionality of systems underlying language and gesture. The compositionality hypothesis receives support for the existence of phonemic paraphasias in sign language production, illustrating structural dissolution which is absent in the production of pantomimic gesture. Understanding the neural encoding of compositional motoric systems may lead to a principled anatomical account of the neural separability of language and gesture. This case provides a powerful indication of the left hemispheres specialization for language-specific functions.

fMRI auditory language differences between dyslexic and able reading children

During fMRI, dyslexic and control boys completed auditory language tasks (judging whether pairs of real and/or pseudo words rhymed or were real words) in 30 s ‘on’ conditions alternating with a 30 s ‘off’ condition (judging whether tone pairs were same). During phonological judgment, dyslexics had more activity than controls in right than left inferior temporal gyrus and in left precentral gyrus. During lexical judgment, dyslexics were less active than controls in bilateral middle frontal gyrus and more active than controls in left orbital frontal cortex. Individual dyslexics were reliably less active than controls in left insula and left inferior temporal gyrus. Dyslexic and control children differ in brain activation during auditory language processing skills that do not require reading.

Dissociation of action and object naming: Evidence from cortical stimulation mapping

This cortical stimulation mapping study investigates the neural representation of action and object naming. Data from 13 neurosurgical subjects undergoing awake cortical mapping is presented. Our findings indicate clear evidence of differential disruption of noun and verb naming in the context of this naming task. At the individual level, evidence was found for punctuate regions of perisylvian cortex subserving noun and verb function. Across subjects, however, the location of these sites varied. This finding may help explain discrepancies between lesion and functional imaging studies of noun and verb naming. In addition, an alternative coding of these data served to highlight the grammatical class vulnerability of the target response. The use of this coding scheme implicates a role for the supramarginal gyrus in verb‐naming behavior. These data are discussed with respect to a functional–anatomical pathway underlying verb naming. Hum. Brain Mapping 24:1–10, 2005.

Functional Roles of Broca's Area and SMG: Evidence from Cortical Stimulation Mapping in a Deaf Signer

The importance of the left hemisphere in language function has been firmly established and current work strives to understand regional specializations within the perisylvian language areas. This paper reports a case study of a deaf user of American Sign Language undergoing an awake cortical stimulation mapping procedure. Patterns of sign errors accompanying electrical stimulation of Brocas area and the supramarginal gyrus (SMG) are reported. Our findings show Brocas area to be involved in the motor execution of sign language. These data demonstrate that the linguistic specificity of Brocas area is not limited to speech behavior. In addition, unusual semantic-phonological errors were observed with stimulation to the SMG; these data may implicate the SMG in the binding of linguistic features in the service of language production. Taken together, these findings provide important insight into the linguistic specificity of Brocas area and the functional role of the supramarginal gyrus in language processing.

Hemispheric specialization for English and ASL: left invariance-right variability

FUNCTIONAL magnetic resonance imaging (fMRI) was used to compare the cerebral organization during sentence processing in English and in American sign language (ASL). Classical language areas within the left hemisphere were recruited by both English in native speakers and ASL in native signers. This suggests a bias of the left hemisphere to process natural languages independently of the modality through which language is perceived. Furthermore, in contrast to English, ASL strongly recruited right hemisphere structures. This was true irrespective of whether the native signers were deaf or hearing. Thus, the specific processing requirements of the language also in part determine the organization of the language systems of the brain.

Language Lateralization in a Bimanual Language

Unlike spoken languages, sign languages of the deaf make use of two primary articulators, the right and left hands, to produce signs. This situation has no obvious parallel in spoken languages, in which speech articulation is carried out by symmetrical unitary midline vocal structures. This arrangement affords a unique opportunity to examine the robustness of linguistic systems that underlie language production in the face of contrasting articulatory demands and to chart the differential effects of handedness for highly skilled movements. Positron emission tomography (PET) technique was used to examine brain activation in 16 deaf users of American Sign Language (ASL) while subjects generated verb signs independently with their right dominant and left nondominant hands (compared to the repetition of noun signs). Nearly identical patterns of left inferior frontal and right cerebellum activity were observed. This pattern of activation during signing is consistent with patterns that have been reported for spoken languages including evidence for specializations of inferior frontal regions related to lexical-semantic processing, search and retrieval, and phonological encoding. These results indicate that lexical-semantic processing in production relies upon left-hemisphere regions regardless of the modality in which a language is realized, and that this left-hemisphere activation is stable, even in the face of conflicting articulatory demands. In addition, these data provide evidence for the role of the right posterolateral cerebellum in linguistic-cognitive processing and evidence of a left ventral fusiform contribution to sign language processing.

On the nature of phonological structure in sign language

The study of phonological structure and patterns across languages is seen by contemporary phonologists as a way of gaining insight into language as a cognitive system. Traditionally, phonologists have focused on spoken languages. More recently, we have observed a growing interest in the grammatical system underlying signed languages of the deaf. This development in the field of phonology provides a natural laboratory for investigating language universals. As grammatical systems, in part, reflect the modality in which they are expressed, the comparison of spoken and signed languages permits us to separate those aspects of grammar which are modality-dependent from those which are shared by all human languages. On the other hand, modality-dependent characteristics must also be accounted for by a comprehensive theory of language. Comparing languages in two modalities is therefore of theoretical importance for both reasons: establishing modality-independent linguistic universals, and accounting for modality-dependent structure and organisation.

Anatomic subdivisions in human temporal cortical neuronal activity related to recent verbal memory

We identified functional anatomical subdivisions of human lateral and basal temporal cortex related to recent verbal memory for object names, text and auditory words. Extracellular neuronal activity was recorded during memory encoding compared to identification, during encoding, storage or recall retrieval stages of the memory task, during recognition memory, and during implicit memory as measured by repetition priming. Changes in frequency of activity during encoding were recorded from most neurons. In lateral temporal cortex, these encoding changes in the dominant hemisphere were more likely to be polymodal, whereas those in nondominant hemisphere were unimodal. There was substantial separation of neurons with changes in other aspects of memory, defining additional subdivisions. Inferior lateral and basal cortex were related to memory stages, and superior–posterior lateral cortex was related to implicit and recognition memory.