Publications by authors named "Aaron J Newman"

30 Publications

  • Page 1 of 1

Neural correlates of the production effect: An fMRI study.

Brain Cogn 2021 Jun 12;152:105757. Epub 2021 Jun 12.

Memorial University of Newfoundland, Department of Psychology, St. John's, NL A1B 3X9, Canada. Electronic address:

Recognition memory is improved for items produced at study (e.g., by reading them aloud) relative to a non-produced control condition (e.g., silent reading). This production effect is typically attributed to the extra elements in the production task (e.g., motor activation, auditory perception) enhancing item distinctiveness. To evaluate this claim, the present study examined the neural mechanisms underlying the production effect. Prior to a recognition memory test, different words within a study list were read either aloud, silently, or while saying "check" (as a sensorimotor control condition). Production improved recognition, and aloud words yielded higher rates of both recollection and familiarity judgments than either silent or control words. During encoding, fMRI revealed stronger activation in regions associated with motor, somatosensory, and auditory processing for aloud items than for either silent or control items. These activations were predictive of recollective success for aloud items at test. Together, our findings are compatible with a distinctiveness-based account of the production effect, while also pointing to the possible role of other processing differences during the aloud trials as compared to silent and control.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.bandc.2021.105757DOI Listing
June 2021

Enhancement of visual biological motion recognition in early-deaf adults: Functional and behavioral correlates.

PLoS One 2020 10;15(8):e0236800. Epub 2020 Aug 10.

Département de Psychologie, Centre de recherche en neuropsychologie et cognition, Université de Montréal, Québec, Canada.

Deafness leads to brain modifications that are generally associated with a cross-modal activity of the auditory cortex, particularly for visual stimulations. In the present study, we explore the cortical processing of biological motion that conveyed either non-communicative (pantomimes) or communicative (emblems) information, in early-deaf and hearing individuals, using fMRI analyses. Behaviorally, deaf individuals showed an advantage in detecting communicative gestures relative to hearing individuals. Deaf individuals also showed significantly greater activation in the superior temporal cortex (including the planum temporale and primary auditory cortex) than hearing individuals. The activation levels in this region were correlated with deaf individuals' response times. This study provides neural and behavioral evidence that cross-modal plasticity leads to functional advantages in the processing of biological motion following lifelong auditory deprivation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0236800PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7416928PMC
October 2020

The impacts of actual and perceived nicotine administration on insula functional connectivity with the anterior cingulate cortex and nucleus accumbens.

J Psychopharmacol 2019 12 23;33(12):1600-1609. Epub 2019 Sep 23.

Department of Psychology and Neuroscience, Dalhousie University, Halifax, NS, Canada.

Background: Changes in resting state functional connectivity between the insula and dorsal anterior cingulate cortex as well as between the insula and nucleus accumbens have been linked to nicotine withdrawal and/or administration. However, because many of nicotine's effects in humans appear to depend, at least in part, on the belief that nicotine has been administered, the relative contribution of nicotine's pharmacological actions to such effects requires clarification.

Aims: The purpose of this study was to examine the impacts of perceived and actual nicotine administration on neural responses.

Methods: Twenty-six smokers were randomly assigned to receive either a nicotine inhaler (4 mg deliverable) or a nicotine-free inhaler across two sessions. Inhaler content instructions (told nicotine vs told nicotine-free) differed across sessions. Resting state functional connectivity between sub-regions of the insula and the dorsal anterior cingulate cortex and nucleus accumbens was measured using magnetic resonance imaging before and after inhaler administration.

Results: Both actual and perceived nicotine administration independently altered resting state functional connectivity between the anterior insula and the dorsal anterior cingulate cortex, with actual administration being associated with decreased resting state functional connectivity, and perceived administration with increased resting state functional connectivity. Actual nicotine administration also contralaterally reduced resting state functional connectivity between the anterior insula and nucleus accumbens, while reductions in resting state functional connectivity between the mid-insula and right nucleus accumbens were observed when nicotine was administered unexpectedly. Changes in resting state functional connectivity associated with actual or perceived nicotine administration were unrelated to changes in subjective withdrawal and craving. Changes in withdrawal and craving were however independently associated with resting state functional connectivity between the nucleus accumbens and insula.

Conclusions: Our findings highlight the importance of considering non-pharmacological factors when examining drug mechanisms of action.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1177/0269881119872205DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6854612PMC
December 2019

A sinister subject: Quantifying handedness-based recruitment biases in current neuroimaging research.

Eur J Neurosci 2020 04 28;51(7):1642-1656. Epub 2019 Aug 28.

Department of Psychology and Neuroscience, Dalhousie University, Halifax, NS, Canada.

Approximately ten per cent of humans are left-handed or ambidextrous (adextral). It has been suggested that, despite their sizable representation at the whole-population level, this demographic is largely avoided by researchers within the neuroimaging community. To date, however, no formal effort has been made to quantify the extent to which adextrals are excluded from neuroimaging-based research. Here, we aimed to address this question in a review of over 1,000 recent articles published in high-impact, peer-reviewed, neuroimaging-focused journals. Specifically, we sought to ascertain whether, and the extent to which adextrals are underrepresented in neuroimaging study samples, and to delineate potential trends in this bias. Handedness data were available for over 30,000 research subjects; only around 3%-4% of these individuals were adextral-considerably less than the 10% benchmark one would expect if neuroimaging samples were truly representative of the general population. This observation was generally consistent across different areas of research, but was modulated by the demographic characteristics of neuroimaging participants. The epistemological and ethical implications of these findings are discussed.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/ejn.14542DOI Listing
April 2020

Microstructural Findings in White Matter Associated with Cannabis and Alcohol Use in Early-Phase Psychosis: A Diffusion Tensor Imaging and Relaxometry Study.

Brain Connect 2018 11;8(9):567-576

1 Department of Psychiatry, Dalhousie University , Halifax, Canada .

Accumulating evidence suggests that brain white matter (WM) abnormalities may be central to the pathophysiology of psychotic disorders. In addition, there is evidence that cannabis use and alcohol use each is associated with WM abnormalities. However, there are very limited data on the effects of these substances on WM microstructure in patients with psychosis, especially for those at the early phase of illness. This project aimed to examine the impact of cannabis use and alcohol use on WM tissue in early-phase psychosis (EPP). WM was investigated in 21 patients with EPP using diffusion tensor imaging (DTI) and transverse relaxation time of tissue water (T2), with the primary outcomes being mean fractional anisotropy (FA) and T2. DTI analyses were performed at the full-brain level using tract-based spatial statistics with both DTI and T2 analysis done within a WM volume of interest (VOI) implicated in psychosis (containing the left superior longitudinal fasciculus). Our findings revealed that younger age of onset of regular alcohol use (more than one drink per week) was associated with lower FA values in the left thalamic radiation and left parahippocampal and left amygdalar WM. More frequent lifetime cannabis use was correlated with increased mean full-brain FA. There was no significant relationship found between FA and alcohol or cannabis use within the VOI. Relaxometry analysis revealed trend-level evidence of shortened T2 with later onset of regular alcohol use and with more frequent cannabis use. This study provides novel data demonstrating cortical and subcortical WM findings related to alcohol use in EPP and is the first to combine DTI and relaxometry, relating to this patient population.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1089/brain.2018.0611DOI Listing
November 2018

Do emotion-induced blindness and the attentional blink share underlying mechanisms? An event-related potential study of emotionally-arousing words.

Cogn Affect Behav Neurosci 2017 06;17(3):592-611

Department of Psychology, Brock University, 500 Glenridge Avenue, St. Catharines, ON, L2S 3A1, Canada.

When two targets are presented within approximately 500 ms of each other in the context of rapid serial visual presentation (RSVP), participants' ability to report the second target is reduced compared to when the targets are presented further apart in time. This phenomenon is known as the attentional blink (AB). The AB is increased in magnitude when the first target is emotionally arousing. Emotionally arousing stimuli can also capture attention and create an AB-like effect even when these stimuli are presented as to-be-ignored distractor items in a single-target RSVP task. This phenomenon is known as emotion-induced blindness (EIB). The phenomenological similarity in the behavioral results associated with the AB with an emotional T1 and EIB suggest that these effects may result from similar underlying mechanisms - a hypothesis that we tested using event-related electrical brain potentials (ERPs). Behavioral results replicated those reported previously, demonstrating an enhanced AB following an emotionally arousing target and a clear EIB effect. In both paradigms highly arousing taboo/sexual words resulted in an increased early posterior negativity (EPN) component that has been suggested to represent early semantic activation and selection for further processing in working memory. In both paradigms taboo/sexual words also produced an increased late positive potential (LPP) component that has been suggested to represent consolidation of a stimulus in working memory. Therefore, ERP results provide evidence that the EIB and emotion-enhanced AB effects share a common underlying mechanism.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3758/s13415-017-0499-7DOI Listing
June 2017

Preliminary Investigation of the Passively Evoked N400 as a Tool for Estimating Speech-in-Noise Thresholds.

Am J Audiol 2016 Dec;25(4):344-358

School of Human Communication Disorders, Dalhousie University, Halifax, Nova Scotia, CanadaSchool of Psychology, Dalhousie University, Halifax, Nova Scotia, CanadaDivision of Otolaryngology, Queen Elizabeth II Health Sciences Centre, Halifax, Nova Scotia, CanadaBiomedical Translational Imaging Centre, IWK Health Centre, Halifax, Nova Scotia, Canada.

Purpose: Speech-in-noise testing relies on a number of factors beyond the auditory system, such as cognitive function, compliance, and motor function. It may be possible to avoid these limitations by using electroencephalography. The present study explored this possibility using the N400.

Method: Eleven adults with typical hearing heard high-constraint sentences with congruent and incongruent terminal words in the presence of speech-shaped noise. Participants ignored all auditory stimulation and watched a video. The signal-to-noise ratio (SNR) was varied around each participant's behavioral threshold during electroencephalography recording. Speech was also heard in quiet.

Results: The amplitude of the N400 effect exhibited a nonlinear relationship with SNR. In the presence of background noise, amplitude decreased from high (+4 dB) to low (+1 dB) SNR but increased dramatically at threshold before decreasing again at subthreshold SNR (-2 dB).

Conclusions: The SNR of speech in noise modulates the amplitude of the N400 effect to semantic anomalies in a nonlinear fashion. These results are the first to demonstrate modulation of the passively evoked N400 by SNR in speech-shaped noise and represent a first step toward the end goal of developing an N400-based physiological metric for speech-in-noise testing.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1044/2016_AJA-15-0080DOI Listing
December 2016

Using CForest to Analyze Diffusion Tensor Imaging Data: A Study of White Matter Integrity in Healthy Aging.

Brain Connect 2016 12 28;6(10):747-758. Epub 2016 Nov 28.

1 Department of Psychology & Neuroscience, Dalhousie University , Halifax, Canada .

Healthy aging has been associated with a global reduction in white matter integrity, which is thought to reflect cognitive decline. The present study aimed to investigate this reduction over a broad range of the life span, using diffusion tensor imaging analyzed with conditional inference random forest modeling (CForest). This approach is sensitive to subtle and potentially nonlinear effects over the age continuum and was used to characterize the progression of decline in greater detail than has been possible in the past. Data were collected from 45 healthy individuals ranging in age from 19 to 67 years. Fractional anisotropy (FA) was estimated using probabilistic tractography for a number of major tracts across the brain. Age coincided with a nonlinear decrease in FA, with onset beginning at ∼30 years of age and the steepest declines occurring later in life. However, several tracts showed a transient increase before this decline. The progression of decline varied by tract, with steeper but later decline occurring in more anterior tracts. Finally, strongly right-handed individuals demonstrated relatively preserved FA until more than a decade following the onset of decline of others. These results demonstrate that using a novel, nonparametric analysis approach, previously reported reductions in FA with healthy aging were confirmed, while at the same time, new insight was provided into the onset and progression of decline, with evidence suggesting increases in integrity continuing into adulthood.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1089/brain.2016.0451DOI Listing
December 2016

Asymmetric Weighting to Optimize Regional Sensitivity in Combined fMRI-MEG Maps.

Brain Topogr 2016 Jan;29(1):1-12

Functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG) are neuroimaging techniques that measure inherently different physiological processes, resulting in complementary estimates of brain activity in different regions. Combining the maps generated by each technique could thus provide a richer understanding of brain activation. However, present approaches to integration rely on a priori assumptions, such as expected patterns of brain activation in a task, or use fMRI to bias localization of MEG sources, diminishing fMRI-invisible sources. We aimed to optimize sensitivity to neural activity by developing a novel method of integrating data from the two imaging techniques. We present a data-driven method of integration that weights fMRI and MEG imaging data by estimates of data quality for each technique and region. This method was applied to a verbal object recognition task. As predicted, the two imaging techniques demonstrated sensitivity to activation in different regions. Activity was seen using fMRI, but not MEG, throughout the medial temporal lobes. Conversely, activation was seen using MEG, but not fMRI, in more lateral and anterior temporal lobe regions. Both imaging techniques were sensitive to activation in the inferior frontal gyrus. Importantly, integration maps retained activation from individual activation maps, and showed an increase in the extent of activation, owing to greater sensitivity of the integration map than either fMRI or MEG alone.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s10548-015-0457-zDOI Listing
January 2016

Neural systems supporting linguistic structure, linguistic experience, and symbolic communication in sign language and gesture.

Proc Natl Acad Sci U S A 2015 Sep 17;112(37):11684-9. Epub 2015 Aug 17.

Department of Brain and Cognitive Sciences, University of Rochester, Rochester, NY 14620; Faculty of Psychology and Educational Sciences, University of Geneva, CH-1205 Geneva, Switzerland.

Sign languages used by deaf communities around the world possess the same structural and organizational properties as spoken languages: In particular, they are richly expressive and also tightly grammatically constrained. They therefore offer the opportunity to investigate the extent to which the neural organization for language is modality independent, as well as to identify ways in which modality influences this organization. The fact that sign languages share the visual-manual modality with a nonlinguistic symbolic communicative system-gesture-further allows us to investigate where the boundaries lie between language and symbolic communication more generally. In the present study, we had three goals: to investigate the neural processing of linguistic structure in American Sign Language (using verbs of motion classifier constructions, which may lie at the boundary between language and gesture); to determine whether we could dissociate the brain systems involved in deriving meaning from symbolic communication (including both language and gesture) from those specifically engaged by linguistically structured content (sign language); and to assess whether sign language experience influences the neural systems used for understanding nonlinguistic gesture. The results demonstrated that even sign language constructions that appear on the surface to be similar to gesture are processed within the left-lateralized frontal-temporal network used for spoken languages-supporting claims that these constructions are linguistically structured. Moreover, although nonsigners engage regions involved in human action perception to process communicative, symbolic gestures, signers instead engage parts of the language-processing network-demonstrating an influence of experience on the perception of nonlinguistic stimuli.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1073/pnas.1510527112DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4577150PMC
September 2015

Modeling nonlinear relationships in ERP data using mixed-effects regression with R examples.

Psychophysiology 2015 Jan 17;52(1):124-39. Epub 2014 Aug 17.

NeuroCognitive Imaging Laboratory, Dalhousie University, Halifax, Nova Scotia, Canada.

In the analysis of psychological and psychophysiological data, the relationship between two variables is often assumed to be a straight line. This may be due to the prevalence of the general linear model in data analysis in these fields, which makes this assumption implicitly. However, there are many problems for which this assumption does not hold. In this paper, we show that, in the analysis of event-related potential (ERP) data, the assumption of linearity comes at a cost and may significantly affect the inferences drawn from the data. We demonstrate why the assumption of linearity should be relaxed and how to model nonlinear relationships between ERP amplitudes and predictor variables within the familiar framework of generalized linear models, using regression splines and mixed-effects modeling.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/psyp.12299DOI Listing
January 2015

Handles of manipulable objects attract covert visual attention: ERP evidence.

Brain Cogn 2014 Apr 18;86:17-23. Epub 2014 Feb 18.

Department of Psychology, Dalhousie University, Life Sciences Center, Halifax, Nova Scotia B3H 4J1, Canada.

Previous research has demonstrated that people are faster at making a manual response with the hand that is aligned with the handle of a manipulable object compared to its functional end. According to theories of embodied cognition (ETC), the presentation of a manipulable object automatically elicits sensorimotor simulations of the respective hand and these simulations facilitate the response. However, an alternative interpretation of these data is that handles preferentially attract visual attention, since attended stimuli and locations typically elicit faster responses. We investigated attentional biases elicited by manipulable and non-manipulable objects using event-related-potentials (ERPs). On each trial, a picture of a manipulable object was followed by a target dot that participants had to make a button-press to. The dot was located at either the handle or functional end of the object. Consistent with previous attentional cuing paradigms, we showed that the P1 ERP component was greater in response to targets cued by handles than by functional ends. These results suggest that object handles automatically bias covert attentional processes. These attentional biases may account for earlier behavioural findings, without any recourse to ETC.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.bandc.2014.01.013DOI Listing
April 2014

Multimodal neuroimaging of frontal white matter microstructure in early phase schizophrenia: the impact of early adolescent cannabis use.

BMC Psychiatry 2013 Oct 17;13:264. Epub 2013 Oct 17.

Department of Psychiatry, Dalhousie University, 5909 Veterans' Memorial Lane, Abbie J, Lane Building, Room 3030, Halifax B3H 2E2, Nova Scotia, Canada.

Background: A disturbance in connectivity between different brain regions, rather than abnormalities within the separate regions themselves, could be responsible for the clinical symptoms and cognitive dysfunctions observed in schizophrenia. White matter, which comprises axons and their myelin sheaths, provides the physical foundation for functional connectivity in the brain. Myelin sheaths are located around the axons and provide insulation through the lipid membranes of oligodendrocytes. Empirical data suggests oligodendroglial dysfunction in schizophrenia, based on findings of abnormal myelin maintenance and repair in regions of deep white matter. The aim of this in vivo neuroimaging project is to assess the impact of early adolescent onset of regular cannabis use on brain white matter tissue integrity, and to differentiate this impact from the white matter abnormalities associated with schizophrenia. The ultimate goal is to determine the liability of early adolescent use of cannabis on brain white matter, in a vulnerable brain.

Methods/design: Young adults with schizophrenia at the early stage of the illness (less than 5 years since diagnosis) will be the focus of this project. Four magnetic resonance imaging measurements will be used to assess different cellular aspects of white matter: a) diffusion tensor imaging, b) localized proton magnetic resonance spectroscopy with a focus on the neurochemical N-acetylaspartate, c) the transverse relaxation time constants of regional tissue water, d) and of N-acetylaspartate. These four neuroimaging indices will be assessed within the same brain region of interest, that is, a large white matter fibre bundle located in the frontal region, the left superior longitudinal fasciculus.

Discussion: We will expand our knowledge regarding current theoretical models of schizophrenia with a more comprehensive multimodal neuroimaging approach to studying the underlying cellular abnormalities of white matter, while taking into consideration the important confounding variable of early adolescent onset of regular cannabis use.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/1471-244X-13-264DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3852698PMC
October 2013

Electrophysiological markers of biological motion and human form recognition.

Neuroimage 2014 Jan 21;84:854-67. Epub 2013 Sep 21.

Department of Psychology and Neuroscience, Life Sciences Centre, Dalhousie University, Halifax, NS B3H 4R2, Canada.

Current models suggest that human form and motion information are initially processed through separate pathways, then integrated in action perception. Testing such a sequential model requires techniques with high temporal resolution. Prior work demonstrated sensitivity of a posterior temporal event-related potential (ERP) effect - the N2 - to biological motion, but did not test whether the N2 indexes biological motion perception specifically, or human form/action perception more generally. We recorded ERPs while participants viewed stimuli across 3 blocks: (1) static (non-moving) point-light displays of humans performing actions; (2) static stick figures with clear forms; and (3) point-light biological motion. A similar sequence of ERP components was elicited by human forms in all blocks (stationary and moving), and reliably discriminated between human and scrambled forms. The N2 showed similar scalp distribution and sensitivity to stimulus manipulations for both stick figures and biological motion, suggesting that it indexes integration of form and motion information, rather than biological motion perception exclusively - and that form and motion information are therefore integrated by approximately 200ms. We identified a component subsequent to the N2, which we label the medial parietal positivity/ventral-anterior negativity (MPP/VAN), that was also sensitive to both human form and motion information. We propose that the MPP/VAN reflects higher-order human action recognition that occurs subsequent to the integration of form and motion information reflected by the N2.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.neuroimage.2013.09.026DOI Listing
January 2014

Sensitivity to white matter FMRI activation increases with field strength.

PLoS One 2013 4;8(3):e58130. Epub 2013 Mar 4.

Institute for Biodiagnostics (Atlantic), National Research Council, Halifax, Nova Scotia, Canada.

Functional magnetic resonance imaging (fMRI) activation in white matter is controversial. Given that many of the studies that report fMRI activation in white matter used high field MRI systems, we investigated the field strength dependence of sensitivity to white matter fMRI activation. In addition, we evaluated the temporal signal to noise ratio (tSNR) of the different tissue types as a function of field strength. Data were acquired during a motor task (finger tapping) at 1.5 T and 4 T. Group and individual level activation results were considered in both the sensorimotor cortex and the posterior limb of the internal capsule. We found that sensitivity increases associated with field strength were greater for white matter than gray matter. The analysis of tSNR suggested that white matter might be less susceptible to increases in physiological noise related to increased field strength. We therefore conclude that high field MRI may be particularly advantageous for fMRI studies aimed at investigating activation in both gray and white matter.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0058130PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3587428PMC
September 2013

Can skilled readers perform a second task in parallel? A functional connectivity MRI study.

Brain Lang 2013 Jan 3;124(1):84-95. Epub 2013 Jan 3.

Departments of Psychology & Neuroscience, Psychiatry, Surgery, and Pediatrics (Division of Neurology), Dalhousie University, Halifax, Nova Scotia, Canada.

When asked to search for a target letter while reading, the patterns with which people miss the target letter reveal information about the process of reading itself. Questions remain as to whether this paradigm reflects normal reading processes however. We used a novel continuous-performance neuroimaging paradigm to address this question. In separate scanning runs, subjects either read alone, read while searching for a target letter, or searched non-words continuously. Functional connectivity analysis recovered the full extent of brain areas identified for reading in a localizer scan, with no differences between reading alone and the dual task condition. Differences were found, however, between both reading conditions and the nonword search condition. These results demonstrate that in skilled readers brain activation associated with reading is unaffected by a concurrent letter-search task. They further demonstrate the utility of a naturalistic, continuous-performance paradigm for studying the neural basis of language processing.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.bandl.2012.11.009DOI Listing
January 2013

Refractory effects of the N1 event-related potential in experienced cochlear implant patients.

Int J Audiol 2013 Feb 3;52(2):104-12. Epub 2013 Jan 3.

Department of Psychology and Neuroscience, Dalhousie University, Halifax, Nova Scotia, Canada.

Objective: To determine if cochlear implant (CI) patients exhibit a temporal processing deficit for auditory stimuli, by examining refractory effects of the N1 event-related potential (ERP) component.

Design: CI patients and normally-hearing controls were tested in an auditory refractory period paradigm while ERP recordings were collected across the scalp. Participants were presented with brief 500-Hz tones that were separated by inter-stimulus intervals (ISIs) of 500, 1000, or 3000 ms. The amplitude of the N1 was examined as a function of ISI within each group.

Study Sample: Ten adult CI patients and 13 age-matched normally-hearing controls were tested. Patients had long-lasting severe or profound sensorineural hearing loss prior to implantation, and a minimum of two years experience with CI activation.

Results: Unlike normally-hearing controls, CI users showed no refractory effect for tones at 500 ms ISIs compared to 1000 ms. However, similar to controls, recovery from refractoriness was observed in anterior locations at 3000 ms.

Conclusion: The refractory period threshold, defined as the minimum ISI where different N1 amplitudes are elicited, is greater than 1000 ms in CI patients; at least double that of normally-hearing controls.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3109/14992027.2012.743044DOI Listing
February 2013

Communicative and noncommunicative point-light actions featuring high-resolution representation of the hands and fingers.

Behav Res Methods 2013 Jun;45(2):319-28

Department of Psychology & Neuroscience, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada.

We describe the creation of a set of point-light movies depicting 43 communicative gestures and 43 noncommunicative, pantomimed actions. These actions were recorded using a motion capture system that is worn on the body and provides accurate capture of the positions and movements of individual fingers. The movies created thus include point-lights on the fingers, allowing for representation of actions and gestures that would not be possible with a conventional, line-of-sight-based motion capture system. These videos would be suitable for use in cognitive and cognitive neuroscientific studies of biological motion and gesture perception. Each video is described, along with an H statistic indicating the consistency of the descriptive labels that 20 observers gave to the actions. We also produced a scrambled version of each movie, in which the starting position of each point was randomized but its local motion vector was preserved. These scrambled movies would be suitable for use as control stimuli in experimental studies. As supplementary materials, we provide QuickTime movie files of each action, along with text files specifying the three-dimensional coordinates of each point-light in each frame of each movie.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3758/s13428-012-0273-2DOI Listing
June 2013

Changes in N400 topography following intensive speech language therapy for individuals with aphasia.

Brain Lang 2012 Nov 1;123(2):94-103. Epub 2012 Sep 1.

Department of Psychology and Neuroscience, Dalhousie University, Halifax, NS B3H 4R2, Canada.

Our goal was to characterize the effects of intensive aphasia therapy on the N400, an electrophysiological index of lexical-semantic processing. Immediately before and after 4 weeks of intensive speech-language therapy, people with aphasia performed a task in which they had to determine whether spoken words were a 'match' or a 'mismatch' to pictures of objects. Pre-therapy, people with aphasia exhibited an N400 mismatch effect that started over right hemisphere electrodes. Post-therapy, gains were seen in clinical measures of language ability, and the onset of the N400 was left-lateralized. No changes in the scalp distribution of the N400 were observed in healthy controls tested twice over the same 4 week interval. Since the distribution of the N400 after aphasia therapy differed from that of healthy controls, we conclude that it reflects the engagement of compensatory neural mechanisms for language processing rather than a return to a "normal" pattern of brain activation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.bandl.2012.06.005DOI Listing
November 2012

Spatial MEG laterality maps for language: clinical applications in epilepsy.

Hum Brain Mapp 2013 Aug 15;34(8):1749-60. Epub 2012 Mar 15.

Institute for Biodiagnostics Atlantic, National Research Council, Halifax, Nova Scotia, Canada.

Functional imaging is increasingly being used to provide a noninvasive alternative to intracarotid sodium amobarbitol testing (i.e., the Wada test). Although magnetoencephalography (MEG) has shown significant potential in this regard, the resultant output is often reduced to a simplified estimate of laterality. Such estimates belie the richness of functional imaging data and consequently limit the potential value. We present a novel approach that utilizes MEG data to compute "complex laterality vectors" and consequently "laterality maps" for a given function. Language function was examined in healthy controls and in people with epilepsy. When compared with traditional laterality index (LI) approaches, the resultant maps provided critical information about the magnitude and spatial characteristics of lateralized function. Specifically, it was possible to more clearly define low LI scores resulting from strong bilateral activation, high LI scores resulting from weak unilateral activation, and most importantly, the spatial distribution of lateralized activation. We argue that the laterality concept is better presented with the inherent spatial sensitivity of activation maps, rather than being collapsed into a one-dimensional index.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/hbm.22024DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6870167PMC
August 2013

The influence of language proficiency on lexical semantic processing in native and late learners of English.

J Cogn Neurosci 2012 May 7;24(5):1205-23. Epub 2011 Oct 7.

Department of Psychology, Life Sciences Centre, Dalhousie University, Halifax, Nova Scotia, Canada.

We investigated the influence of English proficiency on ERPs elicited by lexical semantic violations in English sentences, in both native English speakers and native Spanish speakers who learned English in adulthood. All participants were administered a standardized test of English proficiency, and data were analyzed using linear mixed effects (LME) modeling. Relative to native learners, late learners showed reduced amplitude and delayed onset of the N400 component associated with reading semantic violations. As well, after the N400 late learners showed reduced anterior negative scalp potentials and increased posterior potentials. In both native and late learners, N400 amplitudes to semantically appropriate words were larger for people with lower English proficiency. N400 amplitudes to semantic violations, however, were not influenced by proficiency. Although both N400 onset latency and the late ERP effects differed between L1 and L2 learners, neither correlated with proficiency. Different approaches to dealing with the high degree of correlation between proficiency and native/late learner group status are discussed in the context of LME modeling. The results thus indicate that proficiency can modulate ERP effects in both L1 and L2 learners, and for some measures (in this case, N400 amplitude), L1-L2 differences may be entirely accounted for by proficiency. On the other hand, not all effects of L2 learning can be attributed to proficiency. Rather, the differences in N400 onset and the post-N400 violation effects appear to reflect fundamental differences in L1-L2 processing.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1162/jocn_a_00143DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4447492PMC
May 2012

Interplay between morphology and frequency in lexical access: the case of the base frequency effect.

Brain Res 2011 Feb 15;1373:144-59. Epub 2010 Dec 15.

Division of Neurology and Pediatric Neuroimaging Research Consortium, Cincinnati Children's Hospital Medical Center, OH 45229-3039, USA.

A major issue in lexical processing concerns storage and access of lexical items. Here we make use of the base frequency effect to examine this. Specifically, reaction time to morphologically complex words (words made up of base and suffix, e.g., agree+able) typically reflects frequency of the base element (i.e., total frequency of all words in which agree appears) rather than surface word frequency (i.e., frequency of agreeable itself). We term these complex words decomposable. However, a class of words termed whole-word do not show such sensitivity to base frequency (e.g., serenity). Using an event-related MRI design, we exploited the fact that processing low-frequency words increases BOLD activity relative to high frequency ones, and examined effects of base frequency on brain activity for decomposable and whole-word items. Morphologically complex words, half high and half low base frequency, were compared to match high and low frequency simple monomorphemic words using a lexical decision task. Morphologically complex words increased activation in the left inferior frontal and left superior temporal cortices versus simple words. The only area to mirror the behavioral distinction between the decomposable and the whole-word types was the thalamus. Surprisingly, most frequency-sensitive areas failed to show base frequency effects. This variety of responses to frequency and word type across brain areas supports an integrative view of multiple variables during lexical access, rather than a dichotomy between memory-based access and on-line computation. Lexical access appears best captured as interplay of several neural processes with different sensitivities to various linguistic factors including frequency and morphological complexity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.brainres.2010.12.022DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3038557PMC
February 2011

Sensitivity of the human binaural cortical steady state response to interaural level differences.

Ear Hear 2011 Feb;32(1):114-20

Department of Psychology, Dalhousie University, Halifax, Nova Scotia, Canada.

Objectives: Periodic alternations of the interaural correlation of a noise stimulus evoke an auditory steady state response that can be measured at the scalp, providing an objective measure of binaural integration. The purpose of this study was to examine the effect of interaural level differences on this steady state response.

Design: Auditory steady state responses at 4 and 8 Hz were recorded to 4 Hz cycles of interaural correlation change of a Gaussian noise in normal-hearing listeners. Responses were recorded with symmetric presentation levels of 80, 60, and 40 dB SPL and with interaural asymmetries ranging from 10 to 40 dB, varying in 10-dB steps.

Results: The 8 Hz response was sensitive to interaural level asymmetry and fell to 50% strength at an asymmetry of 18 dB, although the response was detectable to an asymmetry of 30 dB. A simultaneously present 4 Hz response showed no sensitivity to interaural level difference. Significant responses were recorded in all participants.

Conclusions: The 8 Hz auditory steady state response to a 4 Hz change in noise interaural correlation might be useful as an objective measure of binaural integration in asymmetric hearing loss. Response amplitude is more negatively affected by small amounts of interaural asymmetry than by large reductions in overall presentation level.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1097/AUD.0b013e3181ec5d7aDOI Listing
February 2011

Dissociating neural subsystems for grammar by contrasting word order and inflection.

Proc Natl Acad Sci U S A 2010 Apr 5;107(16):7539-44. Epub 2010 Apr 5.

Department of Psychology, Division of Neurology, Institute of Neuroscience, and Brain Repair Centre, Dalhousie University Life Sciences Centre, Halifax, NS, Canada.

An important question in understanding language processing is whether there are distinct neural mechanisms for processing specific types of grammatical structure, such as syntax versus morphology, and, if so, what the basis of the specialization might be. However, this question is difficult to study: A given language typically conveys its grammatical information in one way (e.g., English marks "who did what to whom" using word order, and German uses inflectional morphology). American Sign Language permits either device, enabling a direct within-language comparison. During functional (f)MRI, native signers viewed sentences that used only word order and sentences that included inflectional morphology. The two sentence types activated an overlapping network of brain regions, but with differential patterns. Word order sentences activated left-lateralized areas involved in working memory and lexical access, including the dorsolateral prefrontal cortex, the inferior frontal gyrus, the inferior parietal lobe, and the middle temporal gyrus. In contrast, inflectional morphology sentences activated areas involved in building and analyzing combinatorial structure, including bilateral inferior frontal and anterior temporal regions as well as the basal ganglia and medial temporal/limbic areas. These findings suggest that for a given linguistic function, neural recruitment may depend upon on the cognitive resources required to process specific types of linguistic cues.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1073/pnas.1003174107DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2867749PMC
April 2010

Prosodic and narrative processing in American Sign Language: an fMRI study.

Neuroimage 2010 Aug 27;52(2):669-76. Epub 2010 Mar 27.

Departments of Psychology, Psychiatry, & Surgery & Pediatrics (Division of Neurology), and Neuroscience Institute, Dalhousie University, Halifax, NS, Canada.

Signed languages such as American Sign Language (ASL) are natural human languages that share all of the core properties of spoken human languages but differ in the modality through which they are communicated. Neuroimaging and patient studies have suggested similar left hemisphere (LH)-dominant patterns of brain organization for signed and spoken languages, suggesting that the linguistic nature of the information, rather than modality, drives brain organization for language. However, the role of the right hemisphere (RH) in sign language has been less explored. In spoken languages, the RH supports the processing of numerous types of narrative-level information, including prosody, affect, facial expression, and discourse structure. In the present fMRI study, we contrasted the processing of ASL sentences that contained these types of narrative information with similar sentences without marked narrative cues. For all sentences, Deaf native signers showed robust bilateral activation of perisylvian language cortices as well as the basal ganglia, medial frontal, and medial temporal regions. However, RH activation in the inferior frontal gyrus and superior temporal sulcus was greater for sentences containing narrative devices, including areas involved in processing narrative content in spoken languages. These results provide additional support for the claim that all natural human languages rely on a core set of LH brain regions, and extend our knowledge to show that narrative linguistic functions typically associated with the RH in spoken languages are similarly organized in signed languages.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.neuroimage.2010.03.055DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2908987PMC
August 2010

Brain systems mediating semantic and syntactic processing in deaf native signers: biological invariance and modality specificity.

Proc Natl Acad Sci U S A 2009 May 11;106(21):8784-9. Epub 2009 May 11.

School of Psychological Sciences, University of Manchester, Zochonis Building, Manchester M13 9PL, United Kingdom.

Studies of written and spoken language suggest that nonidentical brain networks support semantic and syntactic processing. Event-related brain potential (ERP) studies of spoken and written languages show that semantic anomalies elicit a posterior bilateral N400, whereas syntactic anomalies elicit a left anterior negativity, followed by a broadly distributed late positivity. The present study assessed whether these ERP indicators index the activity of language systems specific for the processing of aural-oral language or if they index neural systems underlying any natural language, including sign language. The syntax of a signed language is mediated through space. Thus the question arises of whether the comprehension of a signed language requires neural systems specific for this kind of code. Deaf native users of American Sign Language (ASL) were presented signed sentences that were either correct or that contained either a semantic or a syntactic error (1 of 2 types of verb agreement errors). ASL sentences were presented at the natural rate of signing, while the electroencephalogram was recorded. As predicted on the basis of earlier studies, an N400 was elicited by semantic violations. In addition, signed syntactic violations elicited an early frontal negativity and a later posterior positivity. Crucially, the distribution of the anterior negativity varied as a function of the type of syntactic violation, suggesting a unique involvement of spatial processing in signed syntax. Together, these findings suggest that biological constraints and experience shape the development of neural systems important for language.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1073/pnas.0809609106DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2689005PMC
May 2009

An ERP study of regular and irregular English past tense inflection.

Neuroimage 2007 Jan 27;34(1):435-45. Epub 2006 Oct 27.

Department of Psychology, Life Sciences Centre, Dalhousie University, Halifax, NS, Canada B3J 4J1.

Compositionality is a critical and universal characteristic of human language. It is found at numerous levels, including the combination of morphemes into words and of words into phrases and sentences. These compositional patterns can generally be characterized by rules. For example, the past tense of most English verbs ("regulars") is formed by adding an -ed suffix. However, many complex linguistic forms have rather idiosyncratic mappings. For example, "irregular" English verbs have past tense forms that cannot be derived from their stems in a consistent manner. Whether regular and irregular forms depend on fundamentally distinct neurocognitive processes (rule-governed combination vs. lexical memorization), or whether a single processing system is sufficient to explain the phenomena, has engendered considerable investigation and debate. We recorded event-related potentials while participants read English sentences that were either correct or had violations of regular past tense inflection, irregular past tense inflection, syntactic phrase structure, or lexical semantics. Violations of regular past tense and phrase structure, but not of irregular past tense or lexical semantics, elicited left-lateralized anterior negativities (LANs). These seem to reflect neurocognitive substrates that underlie compositional processes across linguistic domains, including morphology and syntax. Regular, irregular, and phrase structure violations all elicited later positivities that were maximal over midline parietal sites (P600s), and seem to index aspects of controlled syntactic processing of both phrase structure and morphosyntax. The results suggest distinct neurocognitive substrates for processing regular and irregular past tense forms: regulars depending on compositional processing, and irregulars stored in lexical memory.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.neuroimage.2006.09.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1988695PMC
January 2007

The cortical organization of audio-visual sentence comprehension: an fMRI study at 4 Tesla.

Brain Res Cogn Brain Res 2004 Jul;20(2):111-9

Department of Psychology, Brain Development Lab, 1227 University of Oregon, Eugene, OR 97403-1227, USA.

Neuroimaging studies of written and spoken sentence processing report greater left hemisphere than right hemisphere activation. However, a large majority of our experience with language is face-to-face interaction, which is much richer in information. The current study examines the neural organization of audio-visual (AV) sentence processing using functional magnetic resonance imaging (fMRI) at 4 Tesla. Participants viewed the face and upper body of a speaker via a video screen while listening to her produce, in alternating blocks, English sentences and sentences composed of pronounceable non-words. Audio-visual sentence processing was associated with activation in the left hemisphere in Broca's area, dorsolateral prefrontal cortex, the superior precentral sulcus, anterior and middle portions of the lateral sulcus, middle superior portions of the temporal sulcus, supramarginal gyrus and angular gyrus. Further, AV sentence processing elicited activation in the right anterior and middle lateral sulcus. Between-hemisphere analyses revealed a left hemisphere dominant pattern of activation. The findings support the hypothesis that the left hemisphere may be biased to process language independently of the modality through which it is perceived. These results are discussed in the context of previous neuroimaging results using American Sign Language (ASL).
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.cogbrainres.2003.10.014DOI Listing
July 2004

A critical period for right hemisphere recruitment in American Sign Language processing.

Nat Neurosci 2002 Jan;5(1):76-80

Department of Psychology, 1227 University of Oregon, Eugene, Oregon 97403-1227, USA.

Signed languages such as American Sign Language (ASL) are natural languages that are formally similar to spoken languages, and thus present an opportunity to examine the effects of language structure and modality on the neural organization for language. Native learners of spoken languages show predominantly left-lateralized patterns of neural activation for language processing, whereas native learners of ASL show extensive right hemisphere (RH) and LH activation. We demonstrate that the RH angular gyrus is active during ASL processing only in native signers (hearing, ASL-English bilinguals) but not in those who acquired ASL after puberty (hearing, native English speakers). This is the first demonstration of a 'sensitive' or 'critical' period for language in an RH structure. This has implications for language acquisition and for understanding age-related changes in neuroplasticity more generally.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/nn775DOI Listing
January 2002
-->