Papers by Sharlene D. Newman
Brain research, Jan 16, 2015
The present study investigates whether the inferior frontal gyrus is activated for phonetic segme... more The present study investigates whether the inferior frontal gyrus is activated for phonetic segmentation of both speech and sign. Early adult second language learners of Spanish and American Sign Language at the very beginning of instruction were tested on their ability to classify lexical items in each language based on their phonetic categories (i.e., initial segments or location parameter, respectively). Conjunction analyses indicated that left-lateralized inferior frontal gyrus (IFG), superior parietal lobule (SPL), and precuneus were activated for both languages. Common activation in the left IFG suggests a modality-independent mechanism for phonetic segmentation. Additionally, common activation in parietal regions suggests spatial preprocessing of audiovisual and manuovisual information for subsequent frontal recoding and mapping. Taken together, we propose that this frontoparietal network is involved in domain-general segmentation of either acoustic or visual signal that is i...
Bilingualism: Language and Cognition, 2015
This study investigated the structure of the bimodal bilingual lexicon. In the cross-modal primin... more This study investigated the structure of the bimodal bilingual lexicon. In the cross-modal priming task nonnative sign language learners heard an English word (e.g.,keys) and responded to the lexicality of a signed target: an underlying rhyme (e.g.,cheese) or a sign neighbor of that word (e.g.,paper). The results indicated that rhyme words were retrieved more quickly and the L2 neighbors were faster for beginner learners. An item analysis also indicated that semantics did not facilitate neighbor retrieval and high frequency signs were retrieved more quickly. The AX discrimination task showed that learners focus on handshape and movement parameters and discriminate equally. The interlanguage dynamics play an important role in which phonological parameters are used and the spread of activation over time. A nonselective, integrated model of the bimodal bilingual lexicon is proposed such that lateral connections are weakened over time and handshape parameter feeds most of the activation...
Morphological brain changes as a consequence of new learning have been widely established. Learni... more Morphological brain changes as a consequence of new learning have been widely established. Learning a second language (L2) is one such experience that can lead to rapid structural neural changes. However, still relatively little is known about how levels of proficiency in the L2 and the age at which the L2 is learned influence brain neuroplasticity. The goal of this study is to provide novel evidence for the effect of bilingualism on white matter structure in relatively proficient but late L2 learners who acquired the second language after early childhood. Overall, the results demonstrate a significant effect on white matter fractional anisotropy (FA) as a function of L2 learning. Higher FA values were found in a broad white matter network including the anterior thalamic radiation (ATR), the inferior fronto-occipital fasciculus (IFOF), the Uncinate Fasciculus (UF), and the inferior longitudinal fasciculus (ILF). Moreover, FA values were correlated with age of L2 acquisition, suggesting that learning an L2, even past childhood, induces neural changes. Finally, these results provide some initial evidence that variability in the age of L2 acquisition has important consequences for neural plasticity. Learning a second language (L2) after a putative critical period for language learning (Long, 1990; Birdsong, 1999) is notably difficult, especially when the native language (L1) and the L2 are linguistically different. Past research on late L2 attainment suggesting mixed outcomes has been interpreted in different ways. One perspective proposes that late L2 representation and processing is hard-wired by maturational constraints and is fundamentally different than native language processing, especially when the grammatical structures of the two languages differ (e.
Psychiatry Research: Neuroimaging, 2008
Although accumulating evidence suggests that cerebellar abnormalities may be linked to the sympto... more Although accumulating evidence suggests that cerebellar abnormalities may be linked to the symptoms and course of schizophrenia, few studies have related structural and functional indices of cerebellar integrity. The present study examined the relationship between the volume of specific subregions of the cerebellum and cerebellar function, as measured by eyeblink conditioning. Nine individuals with schizophrenia and six healthy comparison participants completed structural magnetic resonance imaging of the brain and a delay eyeblink conditioning procedure. Volumetric measurements were taken for the whole brain, whole cerebellum, cerebellar anterior lobules I-V and posterior lobules VI-VII. The schizophrenia group had smaller cerebellar anterior lobes and exhibited impaired eyeblink conditioning compared to the comparison group. In the comparison group, larger anterior volume correlated with earlier conditioned response onset latencies and increased amplitudes of the unconditioned blink response during paired trials (i.e., when the conditioned and unconditioned stimuli co-occurred). The findings that smaller anterior cerebellar volumes and EBC impairments were associated with schizophrenia are consistent with non-human studies showing that anterior cerebellar abnormalities are associated with associative deficits in delay eyeblink conditioning. The lack of a significant correlation between indices of eyeblink conditioning and cerebellar volume within the schizophrenic group suggests an aberrant relationship between cerebellar structure and function.
Frontiers in Psychology, 2015
Developmental dyslexia is a complex and heterogeneous disorder characterized by unexpected diffic... more Developmental dyslexia is a complex and heterogeneous disorder characterized by unexpected difficulty in learning to read. Although it is considered to be biologically based, the degree of variation has made the nature and locus of dyslexia difficult to ascertain. Hypotheses regarding the cause have ranged from low-level perceptual deficits to higher order cognitive deficits, such as phonological processing and visual-spatial attention. We applied the capacity coefficient, a measure obtained from a mathematical cognitive model of response times to measure how efficiently participants processed different classes of stimuli. The capacity coefficient was used to test the extent to which individuals with dyslexia can be distinguished from normal reading individuals based on their ability to take advantage of word, pronounceable non-word, consonant sequence or unfamiliar context when categorizing character strings. Within subject variability of the capacity coefficient across character string types was fairly regular across normal reading adults and consistent with a previous study of word perception with the capacity coefficient-words and pseudowords were processed at super-capacity and unfamiliar characters strings at limited-capacity. Two distinct patterns were observed in individuals with dyslexia. One group had a profile similar to the normal reading adults while the other group showed very little variation in capacity across string-type. It is possible that these individuals used a similar strategy for all four string-types and were able to generalize this strategy when processing unfamiliar characters. This difference across dyslexia groups may be used to identify sub-types of the disorder and suggest significant differences in word level processing among these subtypes. Therefore, this approach may be useful in further delineating among types of dyslexia, which in turn may lead to better understanding of the etiologies of dyslexia.
Schizophrenia research, Jan 20, 2015
A disturbance in the integration of information during mental processing has been implicated in s... more A disturbance in the integration of information during mental processing has been implicated in schizophrenia, possibly due to faulty communication within and between brain regions. Graph theoretic measures allow quantification of functional brain networks. Functional networks are derived from correlations between time courses of brain regions. Group differences between SZ and control groups have been reported for functional network properties, but the potential of such measures to classify individual cases has been little explored. We tested whether the network measure of betweenness centrality could classify persons with schizophrenia and normal controls. Functional networks were constructed for 19 schizophrenic patients and 29 non-psychiatric controls based on resting state functional MRI scans. The betweenness centrality of each node, or fraction of shortest-paths that pass through it, was calculated in order to characterize the centrality of the different regions. The nodes wit...
The open neuroimaging journal, 2007
The current study examined the hemodynamic timecourse of activation within a network of regions t... more The current study examined the hemodynamic timecourse of activation within a network of regions that is thought to be associated with visual imagery. Two experimental conditions were examined that were designed to place differential demands on specific nodes within the visual imagery network. The two tasks were an object inspection task and a mental rotation task. The two conditions recruited overlapping cortical regions; however several regions revealed a differential response to object inspection and mental rotation. The mental rotation condition elicited greater activation in parietal cortex, lateral occipital/temporal regions, and bilateral prefrontal cortex. Conversely, the object inspection condition elicited greater activation in inferior extrastriate cortex, the inferior frontal gyrus, and the right cerebellum. When examining the timecourse of activation three different timecourse patterns were observed across cortical regions and conditions. The shape of the hemodynamic tim...
Cortex; a journal devoted to the study of the nervous system and behavior, 2014
Previous studies have reported anticipatory effects during sentence processing. However, the sour... more Previous studies have reported anticipatory effects during sentence processing. However, the source of these effects has not been clearly characterized. This study investigated the hypothesis that one source of anticipatory effects, particularly during verb processing, is the automatic triggering of argument structure processes. If argument structure processes are automatically triggered it was hypothesized that the task need not require the initiation of the process, as such a primed lexical decision task was used that examined the neural priming of cross-grammatical class prime pairs (e.g., verb-noun priming). While previous studies, as does the current study, have revealed behavioral priming for cross-grammatical class and within-class (noun-noun and verb-verb) prime/target pairs, the current results revealed significant activation differences. Enhancement effects were observed for cross-grammatical class priming in the language network, particularly the inferior frontal gyrus (B...
Brain connectivity, 2011
Endocannabinoid receptors modulate synaptic plasticity in the brain and may therefore impact cort... more Endocannabinoid receptors modulate synaptic plasticity in the brain and may therefore impact cortical connectivity not only during development but also in response to substance abuse in later life. Such alterations may not be evident in volumetric measures utilized in brain imaging, but could affect the local and global organization of brain networks. To test this hypothesis, we used a novel computational approach to estimate network measures of structural brain connectivity derived from diffusion tensor imaging (DTI) and white matter tractography. Twelve adult cannabis (CB) users and 13 healthy subjects were evaluated using a graph theoretic analysis of both global and local brain network properties. Structural brain networks in both CB subjects and controls exhibited robust small-world network attributes in both groups. However, CB subjects showed significantly decreased global network efficiency and significantly increased clustering coefficients (degree to which nodes tend to cl...
Cognitive Brain Research, 2003
This study attempts to specify the contribution of two subregions of Broca&am... more This study attempts to specify the contribution of two subregions of Broca's area during syntactic and semantic processing of sentences by examining brain activation in a grammaticality judgment task. The processing of two types of ungrammatical sentences was examined. One type leaves the thematic interpretation generally unaffected, by violating the noun-verb agreement in number, while the other type introduces an extraneous verb, which cannot be incorporated into the developing thematic structure. Pars triangularis was more sensitive to the extra verb violation, whereas pars opercularis was more sensitive to the noun-verb agreement violation. The current study adds to the growing literature that suggests there are separable functional subregions of Broca's area, with pars triangularis more involved in thematic processing and pars opercularis more involved in syntactic processing. The posterior left temporal area was also involved in both types of processing.
Two experiments are reported that used fMRI to compare the brain activation during the imagery of... more Two experiments are reported that used fMRI to compare the brain activation during the imagery of material and geometric object features. In the first experiment, participants were to mentally evaluate objects along either a material dimension (roughness, hardness and temperature; e.g., Which is harder, a potato or a mushroom?) or a geometric dimension (size and shape; e.g., Which is larger, a pumpkin or a cucumber?). In the second experiment, when given the name of an object and either a material (roughness and hardness) or geometric (size and shape) property participants rated the object on a scale from 1 to 4. Both experiments were designed to examine the underlying neural substrate that supports the processing of material object properties with respect to geometric properties. Considering the relative amount of activation across the two types of object properties, we found that (1) the interrogation of geometric features differentially evokes visual imagery which involves the re...
Schizophrenia Bulletin, 2014
Recent studies of schizophrenia have revealed cognitive and memory deficits that are accompanied ... more Recent studies of schizophrenia have revealed cognitive and memory deficits that are accompanied by disruptions of neuronal connectivity in cortical and subcortical brain regions. More recently, alterations of topological organization of structural networks in schizophrenia are also being identified using graph theoretical analysis. However, the role of the cerebellum in this network structure remains largely unknown. In this study, global network measures obtained from diffusion tensor imaging were computed in the cerebella of 25 patients with schizophrenia and 36 healthy volunteers. While cerebellar global network characteristics were slightly altered in schizophrenia patients compared with healthy controls, the patients showed a retained small-world network organization. The modular architecture, however, was changed mainly in crus II. Furthermore, schizophrenia patients had reduced correlations between modularity and microstructural integrity, as measured by fractional anisotropy (FA) in lobules I-IV and X. Finally, FA alterations were significantly correlated with the Positive and Negative Syndrome Scale symptom scores in schizophrenia patients. Taken together, our data suggest that schizophrenia patients have altered network architecture in the cerebellum with reduced local microstructural connectivity and that cerebellar structural abnormalities are associated symptoms of the disorder.
Psychological Research, 2012
Functional magnetic resonance imaging was used to investigate the role of phonology in visual wor... more Functional magnetic resonance imaging was used to investigate the role of phonology in visual word recognition (VWR). A group of children between the ages of 7 and 13 participated in a lexical decision task in which lexical frequency and homophony were manipulated. A significant homophone effect was observed for the highfrequency condition, indicating that phonology does indeed play a significant role in VWR. The brain activation patterns also support this idea in that regions that have been linked to phonological processing, the inferior frontal gyrus and the inferior parietal lobe, also revealed a homophone effect. Additionally, the posterior superior temporal cortex showed a homophone effect; however, this activation is argued to be related to lexical competition generated by the high-frequency homophone via the activation of multiple semantic representations.
Psychiatry Research: Neuroimaging, 2008
Although accumulating evidence suggests that cerebellar abnormalities may be linked to the sympto... more Although accumulating evidence suggests that cerebellar abnormalities may be linked to the symptoms and course of schizophrenia, few studies have related structural and functional indices of cerebellar integrity. The present study examined the relationship between the volume of specific subregions of the cerebellum and cerebellar function, as measured by eyeblink conditioning. Nine individuals with schizophrenia and six healthy comparison participants completed structural magnetic resonance imaging of the brain and a delay eyeblink conditioning procedure. Volumetric measurements were taken for the whole brain, whole cerebellum, cerebellar anterior lobules I-V and posterior lobules VI-VII. The schizophrenia group had smaller cerebellar anterior lobes and exhibited impaired eyeblink conditioning compared to the comparison group. In the comparison group, larger anterior volume correlated with earlier conditioned response onset latencies and increased amplitudes of the unconditioned blink response during paired trials (i.e., when the conditioned and unconditioned stimuli co-occurred). The findings that smaller anterior cerebellar volumes and EBC impairments were associated with schizophrenia are consistent with non-human studies showing that anterior cerebellar abnormalities are associated with associative deficits in delay eyeblink conditioning. The lack of a significant correlation between indices of eyeblink conditioning and cerebellar volume within the schizophrenic group suggests an aberrant relationship between cerebellar structure and function.
Neuropsychologia, 2003
This study triangulates executive planning and visuo-spatial reasoning in the context of the Towe... more This study triangulates executive planning and visuo-spatial reasoning in the context of the Tower of London (TOL) task by using a variety of methodological approaches. These approaches include functional magnetic resonance imaging (fMRI), functional connectivity analysis, individual difference analysis, and computational modeling. A graded fMRI paradigm compared the brain activation during the solution of problems with varying path lengths: easy
NeuroImage, 2002
A verbal reasoning problem at the intersection of verbal working memory, problem-solving, and lan... more A verbal reasoning problem at the intersection of verbal working memory, problem-solving, and language comprehension was examined using event-related fMRI to distinguish differences in the differential timing of the response of the various cortical regions that compose the working memory network. Problems were developed such that the process demand as well as the timing of the manipulation of the contents of working memory (i.e., a demanding computation) was varied. Activation was observed in several regions including the dorsolateral prefrontal cortex, the inferior frontal gyrus, and the parietal lobe. Examination of the MR amplitude response revealed that the regions do not all activate simultaneously; instead, their activation time courses reveal differential responses that correspond to their theoretical processing role in the problem-solving task. The coordination of cortical area responses reveals how the various cortical regions synchronize and collaborate in order to accomplish a given cognitive function.
Journal of Clinical and Experimental Neuropsychology, 2007
Only recently has there been any consideration of the influence of the problem structure on Tower... more Only recently has there been any consideration of the influence of the problem structure on Tower of London task (TOL) performance. Not surprisingly, these few studies that have investigated this issue have found significant differences in the cognitive demands of individual TOL problems. Based on these previous findings, the aim of the current study was to further explore the effects of two problem characteristics on the planning process - namely, goal hierarchy and the number of optimal solution paths. A number of performance measures when solving six-move problems were examined, including preplanning time, movement time, and accuracy. Analysis of the preplanning time revealed that it was significantly affected by goal hierarchy but not the number of solution paths. The individual movement times, however, revealed effects for both goal hierarchy and the number of optimal solution paths. The number of paths only affected movement times at specific moves: those corresponding to the initiation of a subgoal chunk. The results are discussed in terms of the influence of preplanning on subsequent performance. The present study also suggests that greater care be taken in the selection of TOL problems.
Ilha do Desterro A Journal of English Language, Literatures in English and Cultural Studies, 2012
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Papers by Sharlene D. Newman