Bilingualism: Language and Cognition, Jun 30, 2023
Structural and functional brain adaptations in bilingual speakers are well documented in the neur... more Structural and functional brain adaptations in bilingual speakers are well documented in the neurolinguistic literature. However, far less is known about neural changes evidenced in multilingual speakers. This study investigates brain plasticity in a group of highly proficient multilinguals, fluent in four or more languages, compared to a group of monolinguals. An ROI analysis used to evaluate differences in core linguistic regions and regions associated with language control revealed robust decreases for multilinguals in grey matter thickness of two brain regions within the parietal lobe (i.e., precuneus and angular gyrus), involved in lexico-semantic processing, memory retrieval, and control maintenance. We discuss our findings in the context of emerging models characterizing trajectorial changes in brain structures associated with language experience. We consider how the demands of optimal functioning within multi-linguistic environments may foster cortical changes that manifest as decreased GM thickness in highly proficient multilingual compared to monolinguals.
The effort in the field of Linguistics to develop theories that aim to explain language-dependent... more The effort in the field of Linguistics to develop theories that aim to explain language-dependent effects on language processing is greatly facilitated by the availability of reliable resources representing different languages. This project presents a detailed description of the process of creating a large and representative corpus in Romaniana relatively under-resourced language with unique structural and typological characteristics, that can be used as a reliable language resource for linguistic studies. The decisions that have guided the construction of the corpus, including the type of corpus, its size and component resource files are discussed. Issues related to data collection, data organization and storage, as well as characteristics of the data included in the corpus are described. Currently, the corpus has approximately 5,500,000 tokens originating from written text and 100,000 tokens of spoken language. it includes language samples that represent a wide variety of registers (i.e. written language -16 registers and 5 registers of spoken language), as well as different authors and speakers
The study of deaf users of signed languages, who often experience delays in primary language acqu... more The study of deaf users of signed languages, who often experience delays in primary language acquisition, permits a unique opportunity to examine the effects of aging on the processing of a primary language (L1) acquired under delayed or protracted development. A cohort of 107 congenitally deaf adult signers aged 45-85 years, who were exposed to American Sign Language (ASL) either in infancy, in early childhood, or late childhood were tested using an ASL sentence repetition test. Participants repeated 20 sentences that gradually increased in length and complexity. Logistic mixed effects regression with the factors of Chronological Age and Age of Acquisition was used to assess sentence repetition accuracy. Results showed that Chronological Age was a significant predictor, with increased age being associated with decreased likelihood to reproduce a sentence correctly (OR = 0.56, p = .010). In addition, effects of Age of Acquisition were observed. Relative to native deaf signers, those who acquired ASL in early childhood were less likely to successfully reproduce a sentence (OR = 0.42, p = .003) as were subjects who learned ASL in late childhood (OR = 0.27, p < .001). These data show that aging affects verbatim recall in deaf users of ASL and that the age of sign language acquisition has a significant and lasting effect on repetition ability, even after decades of signed language use. These data show evidence for lifespan continuity of early life effects.
Numerous studies have shown evidence for a sparse lexicon in speech perception, often in the guis... more Numerous studies have shown evidence for a sparse lexicon in speech perception, often in the guise of underspecification, where certain information is omitted in the specification of phonological forms. While previous work has made a good case for underspecifying certain features of single speech sounds, the role of phonological context in underspecification has been overlooked. Contextually-mediated underspecification is particularly relevant to conceptualizations of the lexicon, as it is couched in item-specific (as opposed to phoneme-specific) patterning. In this study, we present behavioral and ERP evidence that surrounding phonological context may trigger underspecified lexical forms, using regular morphophonological alternations in English.
This study examines the relationship between patterns of variation and speech perception using tw... more This study examines the relationship between patterns of variation and speech perception using two English prefixes: 'in-'/'im-' and 'un-'. In natural speech, 'in-' varies due to an underlying process of phonological assimilation, while 'un-' shows a pattern of surface variation, assimilating before labial stems. In a go/no-go lexical decision experiment, subjects were presented a set of 'mispronounced' stimuli in which the prefix nasal was altered (replacing [n] with [m], or vice versa), in addition to real words with unaltered prefixes. No significant differences between prefixes were found in responses to unaltered words. In mispronounced items, responses to 'un-' forms were faster and more accurate than to 'in-' forms, although a significant interaction mitigated this effect in labial contexts. These results suggest the regularity of variation patterns has consequences for the lexical specification of words, and argues against radical underspecification accounts which argue for a maximally sparse lexicon.
Deaf children who receive a cochlear implant early in life and engage in intensive oral/aural the... more Deaf children who receive a cochlear implant early in life and engage in intensive oral/aural therapy often make great strides in spoken language acquisition. However, despite clinicians' best efforts, there is a great deal of variability in language outcomes. One concern is that cortical regions which normally support auditory processing may become reorganized for visual function, leaving fewer available resources for auditory language acquisition. The conditions under which these changes occur are not well understood, but we may begin investigating this phenomenon by looking for interactions between auditory and visual evoked cortical potentials in deaf children. If children with abnormal auditory responses show increased sensitivity to visual stimuli, this may indicate the presence of maladaptive cortical plasticity. We recorded evoked potentials, using both auditory and visual paradigms, from 25 typical hearing children and 26 deaf children (ages 2-8 years) with cochlear implants. An auditory oddball paradigm was used (85% /ba/ syllables vs. 15% frequency modulated tone sweeps) to elicit an auditory P1 component. Visual evoked potentials (VEPs) were recorded during presentation of an intermittent peripheral radial checkerboard while children watched a silent cartoon, eliciting a P1-N1 response. We observed reduced auditory P1 amplitudes and a lack of latency shift associated with normative aging in our deaf sample. We also observed shorter latencies in N1 VEPs to visual stimulus offset in deaf participants. While these data demonstrate cortical changes associated with auditory deprivation, we did not find evidence for a relationship between cortical auditory evoked potentials and the VEPs. This is consistent with descriptions of intra-modal plasticity within visual systems of deaf children, but do not provide evidence for cross-modal plasticity. In addition, we note that sign language experience had no effect on deaf children's early auditory and visual ERP responses.
The Working Memory model of human memory, first introduced by Baddeley and Hitch (1974) , has bee... more The Working Memory model of human memory, first introduced by Baddeley and Hitch (1974) , has been one of the most influential psychological constructs in cognitive psychology and human neuroscience. However the neuronal correlates of core components of this model have yet to be fully elucidated. Here we present data from two studies where human temporal cortical single neuron activity was recorded during tasks differentially affecting the maintenance component of verbal working memory. In Study One we vary the presence or absence of distracting items for the entire period of memory storage. In Study Two we vary the duration of storage so that distractors filled all, or only one-third of the time the memory was stored. Extracellular single neuron recordings were obtained from 36 subjects undergoing awake temporal lobe resections for epilepsy, 25 in Study one, 11 in Study two. Recordings were obtained from a total of 166 lateral temporal cortex neurons during performance of one of these two tasks, 86 study one, 80 study two. Significant changes in activity with distractor manipulation were present in 74 of these neurons (45%), 38 Study one, 36 Study two. In 48 (65%) of those there was increased activity during the period when distracting items were absent, 26 Study One, 22 Study Two. The magnitude of this increase was greater for Study One, 47.6%, than Study Two, 8.1%, paralleling the reduction in memory errors in the absence of distracters, for Study One of 70.3%, Study Two 26.3% These findings establish that human lateral temporal cortex is part of the neural system for working memory, with activity during maintenance of that memory that parallels performance, suggesting it represents active rehearsal. In 31 of these neurons (65%) this activity was an extension of that during working memory encoding that differed significantly from the neural processes recorded during overt and silent language tasks without a recent memory component, 17 Study one, 14 Study two. Contrary to the Baddeley model, that activity during verbal working memory maintenance often represented activity specific to working memory rather than speech or language.
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2005
Cortical mapping (CSM) studies have shown cortical locations for language function are highly var... more Cortical mapping (CSM) studies have shown cortical locations for language function are highly variable from one subject to the next. If individual variation can be normalized, patterns of language organization may emerge that were heretofore hidden. In order to uncover these patterns, computer-aided spatial normalization to a common atlas is required. Our goal was to determine a methodology by which spatial normalization methods could be evaluated and compared. We developed key metrics to measure accuracy of a surface-based (Caret) and volume-based (SPM2) method. We specified that the optimal method would i) minimize variation as measured by spread reduction between CSM language sites across subjects while also ii) preserving anatomical localization of all CSM sites. Eleven subject's structural MR image sets and corresponding CSM site coordinates were registered to the colin27 human brain atlas using each method. Local analysis showed that mapping error rates were highest in mor...
Objective assessment of the sensory pathways is crucial for understanding their development acros... more Objective assessment of the sensory pathways is crucial for understanding their development across the life span and how they may be affected by neurodevelopmental disorders (e.g., autism spectrum) and neurological pathologies (e.g., stroke, multiple sclerosis, etc.). Quick and passive measurements, for example, using electroencephalography (EEG), are especially important when working with infants and young children and with patient populations having communication deficits (e.g., aphasia). However, many EEG paradigms are limited to measuring activity from one sensory domain at a time, may be time consuming, and target only a subset of possible responses from that particular sensory domain (e.g., only auditory brainstem responses or only auditory P1-N1-P2 evoked potentials). Thus we developed a new multisensory paradigm that enables simultaneous, robust, and rapid (6–12 min) measurements of both auditory and visual EEG activity, including auditory brainstem responses, auditory and v...
Careful measurements of the dynamics of speech production have provided important insights into p... more Careful measurements of the dynamics of speech production have provided important insights into phonetic properties of spoken languages. By contrast, analytic quantification of the visual properties of signed languages remains largely unexplored. The purpose of this study was to characterize the spatial and temporal visual properties of American Sign Language (ASL). Novel measurement techniques were used to analyze the spatial frequency of signs and the speed of the hands as they move through space. In Study 1, the amount of energy (or "contrast") as a function of spatial frequency was determined for various sign categories by applying a Fourier transform to static photographs of twoASL signers. In order to determine whether signing produces unique spatial frequency information, amplitude spectra of a person signing were compared to those of a "neutral" image of a person at rest (not signing). The results of this study reveal only small differences in the amplitu...
Repetition priming has been successfully employed to examine stages of processing in a wide varie... more Repetition priming has been successfully employed to examine stages of processing in a wide variety of cognitive domains including language, object recognition and memory. This study uses a novel repetition priming paradigm in the context of a categorization task to explore early stages in the processing of American Sign Language signs and self-grooming gestures. Specifically, we investigated the degree to which deaf signers' and hearing non-signers' perception of these linguistic or non-linguistic actions might be differentially robust to changes in perceptual viewpoint. We conjectured that to the extent that signers were accessing language-specific representations in their performance of the task, they might show more similar priming effects under different viewing conditions than hearing subjects. In essence, this would provide evidence for a visually-based " lack of invariance " phenomenon. However, if the early stages of visual action processing are similar fo...
... involving 37 deaf adult signers and 1 hearing adult signer with a predominantly mesial superi... more ... involving 37 deaf adult signers and 1 hearing adult signer with a predominantly mesial superior occipital-parietal lesion] that investigate: (1) the neural underpinnings of topographic and referential spatial functions, (2) on-line processing of these different uses of space, and (3 ...
We compared normally hearing individuals and congenitally deaf individuals as they monitored movi... more We compared normally hearing individuals and congenitally deaf individuals as they monitored moving stimuli either in the periphery or in the center of the visual field. When participants monitored the peripheral visual field, greater recruitment (as measured by functional magnetic resonance imaging) of the motion-selective area MT/MST was observed in deaf than in hearing individuals, whereas the two groups were comparable when attending to the central visual field. This finding indicates an enhancement of visual attention to peripheral visual space in deaf individuals. Structural equation modeling was used to further characterize the nature of this plastic change in the deaf. The effective connectivity between MT/MST and the posterior parietal cortex was stronger in deaf than in hearing individuals during peripheral but not central attention. Thus, enhanced peripheral attention to moving stimuli in the deaf may be mediated by alterations of the connectivity between MT/MST and the parietal cortex, one of the primary centers for spatial representation and attention.
When children interpret spoken language in real time, linguistic information drives rapid shifts ... more When children interpret spoken language in real time, linguistic information drives rapid shifts in visual attention to objects in the visual world. This language-vision interaction can provide insights into children's developing efficiency in language comprehension. But how does language influence visual attention when the linguistic signal and the visual world are both processed via the visual channel? Here, we measured eye movements during real-time comprehension of a visual-manual language, American Sign Language (ASL), by 29 native ASL-learning children (16-53 mos, 16 deaf, 13 hearing) and 16 fluent deaf adult signers. All signers showed evidence of rapid, incremental language comprehension, tending to initiate an eye movement before sign offset. Deaf and hearing ASL-learners showed similar gaze patterns, suggesting that the in-the-moment dynamics of eye movements during ASL processing are shaped by the constraints of processing a visual language in real time and not by dif...
tures has been hard to unroot. In fact, just as there are and Computational Sciences many spoken ... more tures has been hard to unroot. In fact, just as there are and Computational Sciences many spoken languages, there are many unique and Georgetown University different signed languages. Recent advances in linguis-Washington, DC 20007 tics have revealed that sign languages such as ASL † Psychology Department encompass the same abstract capabilities as spoken Washington University languages and contain all the different levels of linguistic Seattle, Washington 20007 representations found in spoken language, including ‡ Psychology Department phonology, morphology, syntax, semantics, and prag-University of Oregon matics . Eugene, Oregon 97403 Thus, similar linguistic structures are found in spoken and signed languages. A number of authors have pro-One of the most enduring and significant findings from posed that the left hemisphere recruitment for language results from a specialization of these areas for the analy-neuropsychology is the left hemisphere dominance for sis of linguistic structures. By this view, the structural language processing. Studies both past and present similarity between signed and spoken languages preconverge to establish a widespread language network dicts that left hemisphere language areas should also in the left peri-sylvian cortex which encompasses at be recruited during ASL processing. least four main regions: Broca's area, within the inferior On the surface, however, ASL differs markedly from prefrontal cortex; Wernicke's area, within the posterior spoken languages. For example, in ASL, phonological two-thirds of the superior temporal lobe; the anterior distinctions are created by the positions and shape of portion of the superior temporal lobe; and the middle the hands relative to the body rather than by acoustic prefrontal cortex (Neville and Bavelier, 1998). While the features such as nasality and voicing found in spoken language processing abilities of the left hemisphere are languages. The fact that signed and spoken languages uncontroversial, little is known about the determinants rely on different input and output modalities carries imof this left hemisphere specialization for language. Are portant consequences for theories on the origin of the these areas genetically determined to process linguistic left hemisphere dominance for language. It is often arinformation? To what extent is this organization influgued that the left hemisphere specialization for lanenced by the language experience of each individual? guage originates from a left hemisphere advantage to What role does the acoustic structure of languages play execute fine temporal discrimination, such as the fast in this pattern of organization? acoustic processing required during speech perception To date, most of our understanding of the neural bases . By this view, the standard left hemiof language is derived from the studies of spoken lansphere language areas may not be recruited during the guages. Unfortunately, this spoken language bias limits processing of visuo-spatial languages such as ASL. our ability to infer the determinants of left hemisphere Signed and spoken languages also differ by the way specialization for human language. For example, we are they convey linguistic information. While most aspects unable to assess whether left hemisphere dominance of spoken languages rely on fast acoustic transitions arises from the analysis of the sequential/hierarchical (e.g., consonant contrast) and temporal ordering of constructures that are the building blocks of natural lanstituents (e.g., suffixation, prefixation, word order, etc.), guages or rather is attributable to processing of the sign languages make significant use of visuo-spatial acoustic signal of spoken language. devices. For example, the use of signing space as a American Sign Language (ASL), which makes use of staging ground for the depiction of grammatical relaspatial location and motion of the hands in encoding tions is a prominent feature of ASL syntax. As shown in linguistic information, enables us to investigate this is-Figure , in ASL, nominals introduced into the discourse sue. The comparison of the neural representations of are assigned arbitrary reference points in a horizontal spoken and signed languages permits the separation of plane of signing space. Signs with pronominal function those brain structures that are common to all natural are directed toward these points, and verb signs obligahuman languages from those that are determined by torily move between such points in specifying grammatical relations (subject of, object of). Thus, grammatical the modality in which a language develops, providing functions served in many spoken languages by case new insight into the specificity of left hemisphere spemarking or by linear ordering of words are fulfilled in cialization for language. ASL by spatial mechanisms; this is often referred to as In this paper, we will first review some properties of "spatialized syntax" (Lillo-Martin, 1991; Poizner et al., ASL and then discuss the contribution of the left hemi-1987; but see Liddell, 1998, for an alternative view). sphere and that of the right hemisphere to ASL pro-Another example of ASL processing that makes special cessing. use of visuo-spatial information is the classifier system.
The human auditory system distinguishes speech-like information from general auditory signals in ... more The human auditory system distinguishes speech-like information from general auditory signals in a remarkably fast and efficient way. Combining psychophysics and neurophysiology (MEG), we demonstrate a similar result for the processing of visual information used for language communication in users of sign languages. We demonstrate that the earliest visual cortical responses in deaf signers viewing American Sign Language (ASL) signs show specific modulations to violations of anatomic constraints that would make the sign either possible or impossible to articulate. These neural data are accompanied with a significantly increased perceptual sensitivity to the anatomical incongruity. The differential effects in the early visual evoked potentials arguably reflect an expectation-driven assessment of somatic representational integrity, suggesting that language experience and/or auditory deprivation may shape the neuronal mechanisms underlying the analysis of complex human form. The data de...
The Working Memory model of human memory, first introduced by , has been one of the most influent... more The Working Memory model of human memory, first introduced by , has been one of the most influential psychological constructs in cognitive psychology and human neuroscience. However the neuronal correlates of core components of this model have yet to be fully elucidated. Here we present data from two studies where human temporal cortical single neuron activity was recorded during tasks differentially affecting the maintenance component of verbal working memory. In Study One we vary the presence or absence of distracting items for the entire period of memory storage. In Study Two we vary the duration of storage so that distractors filled all, or only one-third of the time the memory was stored. Extracellular single neuron recordings were obtained from 36 subjects undergoing awake temporal lobe resections for epilepsy, 25 in Study one, 11 in Study two. Recordings were obtained from a total of 166 lateral temporal cortex neurons during performance of one of these two tasks, 86 study one, 80 study two. Significant changes in activity with distractor manipulation were present in 74 of these neurons (45%), 38 Study one, 36 Study two. In 48 (65%) of those there was increased activity during the period when distracting items were absent, 26 Study One, 22 Study Two. The magnitude of this increase was greater for Study One, 47.6%, than Study Two, 8.1%, paralleling the reduction in memory errors in the absence of distracters, for Study One of 70.3%, Study Two 26.3% These findings establish that human lateral temporal cortex is part of the neural system for working memory, with activity during maintenance of that memory that parallels performance, suggesting it represents active rehearsal. In 31 of these neurons (65%) this activity was an extension of that during working memory encoding that differed significantly from the neural processes recorded during overt and silent language tasks without a recent memory component, 17 Study one, 14 Study two. Contrary to the Baddeley model, that activity during verbal working memory maintenance often represented activity specific to working memory rather than speech or language.
Bilingualism: Language and Cognition, Jun 30, 2023
Structural and functional brain adaptations in bilingual speakers are well documented in the neur... more Structural and functional brain adaptations in bilingual speakers are well documented in the neurolinguistic literature. However, far less is known about neural changes evidenced in multilingual speakers. This study investigates brain plasticity in a group of highly proficient multilinguals, fluent in four or more languages, compared to a group of monolinguals. An ROI analysis used to evaluate differences in core linguistic regions and regions associated with language control revealed robust decreases for multilinguals in grey matter thickness of two brain regions within the parietal lobe (i.e., precuneus and angular gyrus), involved in lexico-semantic processing, memory retrieval, and control maintenance. We discuss our findings in the context of emerging models characterizing trajectorial changes in brain structures associated with language experience. We consider how the demands of optimal functioning within multi-linguistic environments may foster cortical changes that manifest as decreased GM thickness in highly proficient multilingual compared to monolinguals.
The effort in the field of Linguistics to develop theories that aim to explain language-dependent... more The effort in the field of Linguistics to develop theories that aim to explain language-dependent effects on language processing is greatly facilitated by the availability of reliable resources representing different languages. This project presents a detailed description of the process of creating a large and representative corpus in Romaniana relatively under-resourced language with unique structural and typological characteristics, that can be used as a reliable language resource for linguistic studies. The decisions that have guided the construction of the corpus, including the type of corpus, its size and component resource files are discussed. Issues related to data collection, data organization and storage, as well as characteristics of the data included in the corpus are described. Currently, the corpus has approximately 5,500,000 tokens originating from written text and 100,000 tokens of spoken language. it includes language samples that represent a wide variety of registers (i.e. written language -16 registers and 5 registers of spoken language), as well as different authors and speakers
The study of deaf users of signed languages, who often experience delays in primary language acqu... more The study of deaf users of signed languages, who often experience delays in primary language acquisition, permits a unique opportunity to examine the effects of aging on the processing of a primary language (L1) acquired under delayed or protracted development. A cohort of 107 congenitally deaf adult signers aged 45-85 years, who were exposed to American Sign Language (ASL) either in infancy, in early childhood, or late childhood were tested using an ASL sentence repetition test. Participants repeated 20 sentences that gradually increased in length and complexity. Logistic mixed effects regression with the factors of Chronological Age and Age of Acquisition was used to assess sentence repetition accuracy. Results showed that Chronological Age was a significant predictor, with increased age being associated with decreased likelihood to reproduce a sentence correctly (OR = 0.56, p = .010). In addition, effects of Age of Acquisition were observed. Relative to native deaf signers, those who acquired ASL in early childhood were less likely to successfully reproduce a sentence (OR = 0.42, p = .003) as were subjects who learned ASL in late childhood (OR = 0.27, p < .001). These data show that aging affects verbatim recall in deaf users of ASL and that the age of sign language acquisition has a significant and lasting effect on repetition ability, even after decades of signed language use. These data show evidence for lifespan continuity of early life effects.
Numerous studies have shown evidence for a sparse lexicon in speech perception, often in the guis... more Numerous studies have shown evidence for a sparse lexicon in speech perception, often in the guise of underspecification, where certain information is omitted in the specification of phonological forms. While previous work has made a good case for underspecifying certain features of single speech sounds, the role of phonological context in underspecification has been overlooked. Contextually-mediated underspecification is particularly relevant to conceptualizations of the lexicon, as it is couched in item-specific (as opposed to phoneme-specific) patterning. In this study, we present behavioral and ERP evidence that surrounding phonological context may trigger underspecified lexical forms, using regular morphophonological alternations in English.
This study examines the relationship between patterns of variation and speech perception using tw... more This study examines the relationship between patterns of variation and speech perception using two English prefixes: 'in-'/'im-' and 'un-'. In natural speech, 'in-' varies due to an underlying process of phonological assimilation, while 'un-' shows a pattern of surface variation, assimilating before labial stems. In a go/no-go lexical decision experiment, subjects were presented a set of 'mispronounced' stimuli in which the prefix nasal was altered (replacing [n] with [m], or vice versa), in addition to real words with unaltered prefixes. No significant differences between prefixes were found in responses to unaltered words. In mispronounced items, responses to 'un-' forms were faster and more accurate than to 'in-' forms, although a significant interaction mitigated this effect in labial contexts. These results suggest the regularity of variation patterns has consequences for the lexical specification of words, and argues against radical underspecification accounts which argue for a maximally sparse lexicon.
Deaf children who receive a cochlear implant early in life and engage in intensive oral/aural the... more Deaf children who receive a cochlear implant early in life and engage in intensive oral/aural therapy often make great strides in spoken language acquisition. However, despite clinicians' best efforts, there is a great deal of variability in language outcomes. One concern is that cortical regions which normally support auditory processing may become reorganized for visual function, leaving fewer available resources for auditory language acquisition. The conditions under which these changes occur are not well understood, but we may begin investigating this phenomenon by looking for interactions between auditory and visual evoked cortical potentials in deaf children. If children with abnormal auditory responses show increased sensitivity to visual stimuli, this may indicate the presence of maladaptive cortical plasticity. We recorded evoked potentials, using both auditory and visual paradigms, from 25 typical hearing children and 26 deaf children (ages 2-8 years) with cochlear implants. An auditory oddball paradigm was used (85% /ba/ syllables vs. 15% frequency modulated tone sweeps) to elicit an auditory P1 component. Visual evoked potentials (VEPs) were recorded during presentation of an intermittent peripheral radial checkerboard while children watched a silent cartoon, eliciting a P1-N1 response. We observed reduced auditory P1 amplitudes and a lack of latency shift associated with normative aging in our deaf sample. We also observed shorter latencies in N1 VEPs to visual stimulus offset in deaf participants. While these data demonstrate cortical changes associated with auditory deprivation, we did not find evidence for a relationship between cortical auditory evoked potentials and the VEPs. This is consistent with descriptions of intra-modal plasticity within visual systems of deaf children, but do not provide evidence for cross-modal plasticity. In addition, we note that sign language experience had no effect on deaf children's early auditory and visual ERP responses.
The Working Memory model of human memory, first introduced by Baddeley and Hitch (1974) , has bee... more The Working Memory model of human memory, first introduced by Baddeley and Hitch (1974) , has been one of the most influential psychological constructs in cognitive psychology and human neuroscience. However the neuronal correlates of core components of this model have yet to be fully elucidated. Here we present data from two studies where human temporal cortical single neuron activity was recorded during tasks differentially affecting the maintenance component of verbal working memory. In Study One we vary the presence or absence of distracting items for the entire period of memory storage. In Study Two we vary the duration of storage so that distractors filled all, or only one-third of the time the memory was stored. Extracellular single neuron recordings were obtained from 36 subjects undergoing awake temporal lobe resections for epilepsy, 25 in Study one, 11 in Study two. Recordings were obtained from a total of 166 lateral temporal cortex neurons during performance of one of these two tasks, 86 study one, 80 study two. Significant changes in activity with distractor manipulation were present in 74 of these neurons (45%), 38 Study one, 36 Study two. In 48 (65%) of those there was increased activity during the period when distracting items were absent, 26 Study One, 22 Study Two. The magnitude of this increase was greater for Study One, 47.6%, than Study Two, 8.1%, paralleling the reduction in memory errors in the absence of distracters, for Study One of 70.3%, Study Two 26.3% These findings establish that human lateral temporal cortex is part of the neural system for working memory, with activity during maintenance of that memory that parallels performance, suggesting it represents active rehearsal. In 31 of these neurons (65%) this activity was an extension of that during working memory encoding that differed significantly from the neural processes recorded during overt and silent language tasks without a recent memory component, 17 Study one, 14 Study two. Contrary to the Baddeley model, that activity during verbal working memory maintenance often represented activity specific to working memory rather than speech or language.
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2005
Cortical mapping (CSM) studies have shown cortical locations for language function are highly var... more Cortical mapping (CSM) studies have shown cortical locations for language function are highly variable from one subject to the next. If individual variation can be normalized, patterns of language organization may emerge that were heretofore hidden. In order to uncover these patterns, computer-aided spatial normalization to a common atlas is required. Our goal was to determine a methodology by which spatial normalization methods could be evaluated and compared. We developed key metrics to measure accuracy of a surface-based (Caret) and volume-based (SPM2) method. We specified that the optimal method would i) minimize variation as measured by spread reduction between CSM language sites across subjects while also ii) preserving anatomical localization of all CSM sites. Eleven subject's structural MR image sets and corresponding CSM site coordinates were registered to the colin27 human brain atlas using each method. Local analysis showed that mapping error rates were highest in mor...
Objective assessment of the sensory pathways is crucial for understanding their development acros... more Objective assessment of the sensory pathways is crucial for understanding their development across the life span and how they may be affected by neurodevelopmental disorders (e.g., autism spectrum) and neurological pathologies (e.g., stroke, multiple sclerosis, etc.). Quick and passive measurements, for example, using electroencephalography (EEG), are especially important when working with infants and young children and with patient populations having communication deficits (e.g., aphasia). However, many EEG paradigms are limited to measuring activity from one sensory domain at a time, may be time consuming, and target only a subset of possible responses from that particular sensory domain (e.g., only auditory brainstem responses or only auditory P1-N1-P2 evoked potentials). Thus we developed a new multisensory paradigm that enables simultaneous, robust, and rapid (6–12 min) measurements of both auditory and visual EEG activity, including auditory brainstem responses, auditory and v...
Careful measurements of the dynamics of speech production have provided important insights into p... more Careful measurements of the dynamics of speech production have provided important insights into phonetic properties of spoken languages. By contrast, analytic quantification of the visual properties of signed languages remains largely unexplored. The purpose of this study was to characterize the spatial and temporal visual properties of American Sign Language (ASL). Novel measurement techniques were used to analyze the spatial frequency of signs and the speed of the hands as they move through space. In Study 1, the amount of energy (or "contrast") as a function of spatial frequency was determined for various sign categories by applying a Fourier transform to static photographs of twoASL signers. In order to determine whether signing produces unique spatial frequency information, amplitude spectra of a person signing were compared to those of a "neutral" image of a person at rest (not signing). The results of this study reveal only small differences in the amplitu...
Repetition priming has been successfully employed to examine stages of processing in a wide varie... more Repetition priming has been successfully employed to examine stages of processing in a wide variety of cognitive domains including language, object recognition and memory. This study uses a novel repetition priming paradigm in the context of a categorization task to explore early stages in the processing of American Sign Language signs and self-grooming gestures. Specifically, we investigated the degree to which deaf signers' and hearing non-signers' perception of these linguistic or non-linguistic actions might be differentially robust to changes in perceptual viewpoint. We conjectured that to the extent that signers were accessing language-specific representations in their performance of the task, they might show more similar priming effects under different viewing conditions than hearing subjects. In essence, this would provide evidence for a visually-based " lack of invariance " phenomenon. However, if the early stages of visual action processing are similar fo...
... involving 37 deaf adult signers and 1 hearing adult signer with a predominantly mesial superi... more ... involving 37 deaf adult signers and 1 hearing adult signer with a predominantly mesial superior occipital-parietal lesion] that investigate: (1) the neural underpinnings of topographic and referential spatial functions, (2) on-line processing of these different uses of space, and (3 ...
We compared normally hearing individuals and congenitally deaf individuals as they monitored movi... more We compared normally hearing individuals and congenitally deaf individuals as they monitored moving stimuli either in the periphery or in the center of the visual field. When participants monitored the peripheral visual field, greater recruitment (as measured by functional magnetic resonance imaging) of the motion-selective area MT/MST was observed in deaf than in hearing individuals, whereas the two groups were comparable when attending to the central visual field. This finding indicates an enhancement of visual attention to peripheral visual space in deaf individuals. Structural equation modeling was used to further characterize the nature of this plastic change in the deaf. The effective connectivity between MT/MST and the posterior parietal cortex was stronger in deaf than in hearing individuals during peripheral but not central attention. Thus, enhanced peripheral attention to moving stimuli in the deaf may be mediated by alterations of the connectivity between MT/MST and the parietal cortex, one of the primary centers for spatial representation and attention.
When children interpret spoken language in real time, linguistic information drives rapid shifts ... more When children interpret spoken language in real time, linguistic information drives rapid shifts in visual attention to objects in the visual world. This language-vision interaction can provide insights into children's developing efficiency in language comprehension. But how does language influence visual attention when the linguistic signal and the visual world are both processed via the visual channel? Here, we measured eye movements during real-time comprehension of a visual-manual language, American Sign Language (ASL), by 29 native ASL-learning children (16-53 mos, 16 deaf, 13 hearing) and 16 fluent deaf adult signers. All signers showed evidence of rapid, incremental language comprehension, tending to initiate an eye movement before sign offset. Deaf and hearing ASL-learners showed similar gaze patterns, suggesting that the in-the-moment dynamics of eye movements during ASL processing are shaped by the constraints of processing a visual language in real time and not by dif...
tures has been hard to unroot. In fact, just as there are and Computational Sciences many spoken ... more tures has been hard to unroot. In fact, just as there are and Computational Sciences many spoken languages, there are many unique and Georgetown University different signed languages. Recent advances in linguis-Washington, DC 20007 tics have revealed that sign languages such as ASL † Psychology Department encompass the same abstract capabilities as spoken Washington University languages and contain all the different levels of linguistic Seattle, Washington 20007 representations found in spoken language, including ‡ Psychology Department phonology, morphology, syntax, semantics, and prag-University of Oregon matics . Eugene, Oregon 97403 Thus, similar linguistic structures are found in spoken and signed languages. A number of authors have pro-One of the most enduring and significant findings from posed that the left hemisphere recruitment for language results from a specialization of these areas for the analy-neuropsychology is the left hemisphere dominance for sis of linguistic structures. By this view, the structural language processing. Studies both past and present similarity between signed and spoken languages preconverge to establish a widespread language network dicts that left hemisphere language areas should also in the left peri-sylvian cortex which encompasses at be recruited during ASL processing. least four main regions: Broca's area, within the inferior On the surface, however, ASL differs markedly from prefrontal cortex; Wernicke's area, within the posterior spoken languages. For example, in ASL, phonological two-thirds of the superior temporal lobe; the anterior distinctions are created by the positions and shape of portion of the superior temporal lobe; and the middle the hands relative to the body rather than by acoustic prefrontal cortex (Neville and Bavelier, 1998). While the features such as nasality and voicing found in spoken language processing abilities of the left hemisphere are languages. The fact that signed and spoken languages uncontroversial, little is known about the determinants rely on different input and output modalities carries imof this left hemisphere specialization for language. Are portant consequences for theories on the origin of the these areas genetically determined to process linguistic left hemisphere dominance for language. It is often arinformation? To what extent is this organization influgued that the left hemisphere specialization for lanenced by the language experience of each individual? guage originates from a left hemisphere advantage to What role does the acoustic structure of languages play execute fine temporal discrimination, such as the fast in this pattern of organization? acoustic processing required during speech perception To date, most of our understanding of the neural bases . By this view, the standard left hemiof language is derived from the studies of spoken lansphere language areas may not be recruited during the guages. Unfortunately, this spoken language bias limits processing of visuo-spatial languages such as ASL. our ability to infer the determinants of left hemisphere Signed and spoken languages also differ by the way specialization for human language. For example, we are they convey linguistic information. While most aspects unable to assess whether left hemisphere dominance of spoken languages rely on fast acoustic transitions arises from the analysis of the sequential/hierarchical (e.g., consonant contrast) and temporal ordering of constructures that are the building blocks of natural lanstituents (e.g., suffixation, prefixation, word order, etc.), guages or rather is attributable to processing of the sign languages make significant use of visuo-spatial acoustic signal of spoken language. devices. For example, the use of signing space as a American Sign Language (ASL), which makes use of staging ground for the depiction of grammatical relaspatial location and motion of the hands in encoding tions is a prominent feature of ASL syntax. As shown in linguistic information, enables us to investigate this is-Figure , in ASL, nominals introduced into the discourse sue. The comparison of the neural representations of are assigned arbitrary reference points in a horizontal spoken and signed languages permits the separation of plane of signing space. Signs with pronominal function those brain structures that are common to all natural are directed toward these points, and verb signs obligahuman languages from those that are determined by torily move between such points in specifying grammatical relations (subject of, object of). Thus, grammatical the modality in which a language develops, providing functions served in many spoken languages by case new insight into the specificity of left hemisphere spemarking or by linear ordering of words are fulfilled in cialization for language. ASL by spatial mechanisms; this is often referred to as In this paper, we will first review some properties of "spatialized syntax" (Lillo-Martin, 1991; Poizner et al., ASL and then discuss the contribution of the left hemi-1987; but see Liddell, 1998, for an alternative view). sphere and that of the right hemisphere to ASL pro-Another example of ASL processing that makes special cessing. use of visuo-spatial information is the classifier system.
The human auditory system distinguishes speech-like information from general auditory signals in ... more The human auditory system distinguishes speech-like information from general auditory signals in a remarkably fast and efficient way. Combining psychophysics and neurophysiology (MEG), we demonstrate a similar result for the processing of visual information used for language communication in users of sign languages. We demonstrate that the earliest visual cortical responses in deaf signers viewing American Sign Language (ASL) signs show specific modulations to violations of anatomic constraints that would make the sign either possible or impossible to articulate. These neural data are accompanied with a significantly increased perceptual sensitivity to the anatomical incongruity. The differential effects in the early visual evoked potentials arguably reflect an expectation-driven assessment of somatic representational integrity, suggesting that language experience and/or auditory deprivation may shape the neuronal mechanisms underlying the analysis of complex human form. The data de...
The Working Memory model of human memory, first introduced by , has been one of the most influent... more The Working Memory model of human memory, first introduced by , has been one of the most influential psychological constructs in cognitive psychology and human neuroscience. However the neuronal correlates of core components of this model have yet to be fully elucidated. Here we present data from two studies where human temporal cortical single neuron activity was recorded during tasks differentially affecting the maintenance component of verbal working memory. In Study One we vary the presence or absence of distracting items for the entire period of memory storage. In Study Two we vary the duration of storage so that distractors filled all, or only one-third of the time the memory was stored. Extracellular single neuron recordings were obtained from 36 subjects undergoing awake temporal lobe resections for epilepsy, 25 in Study one, 11 in Study two. Recordings were obtained from a total of 166 lateral temporal cortex neurons during performance of one of these two tasks, 86 study one, 80 study two. Significant changes in activity with distractor manipulation were present in 74 of these neurons (45%), 38 Study one, 36 Study two. In 48 (65%) of those there was increased activity during the period when distracting items were absent, 26 Study One, 22 Study Two. The magnitude of this increase was greater for Study One, 47.6%, than Study Two, 8.1%, paralleling the reduction in memory errors in the absence of distracters, for Study One of 70.3%, Study Two 26.3% These findings establish that human lateral temporal cortex is part of the neural system for working memory, with activity during maintenance of that memory that parallels performance, suggesting it represents active rehearsal. In 31 of these neurons (65%) this activity was an extension of that during working memory encoding that differed significantly from the neural processes recorded during overt and silent language tasks without a recent memory component, 17 Study one, 14 Study two. Contrary to the Baddeley model, that activity during verbal working memory maintenance often represented activity specific to working memory rather than speech or language.
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