Stephen J Swithenby

The Open University (UK), Milton Keynes, England, United Kingdom

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Publications (15)40.7 Total impact

  • Source
    Fiona McNab, Arjan Hillebrand, Stephen J Swithenby, Gina Rippon
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    ABSTRACT: Early, lesion-based models of language processing suggested that semantic and phonological processes are associated with distinct temporal and parietal regions respectively, with frontal areas more indirectly involved. Contemporary spatial brain mapping techniques have not supported such clear-cut segregation, with strong evidence of activation in left temporal areas by both processes and disputed evidence of involvement of frontal areas in both processes. We suggest that combining spatial information with temporal and spectral data may allow a closer scrutiny of the differential involvement of closely overlapping cortical areas in language processing. Using beamforming techniques to analyze magnetoencephalography data, we localized the neuronal substrates underlying primed responses to nouns requiring either phonological or semantic processing, and examined the associated measures of time and frequency in those areas where activation was common to both tasks. Power changes in the beta (14-30 Hz) and gamma (30-50 Hz) frequency bands were analyzed in pre-selected time windows of 350-550 and 500-700 ms In left temporal regions, both tasks elicited power changes in the same time window (350-550 ms), but with different spectral characteristics, low beta (14-20 Hz) for the phonological task and high beta (20-30 Hz) for the semantic task. In frontal areas (BA10), both tasks elicited power changes in the gamma band (30-50 Hz), but in different time windows, 500-700 ms for the phonological task and 350-550 ms for the semantic task. In the left inferior parietal area (BA40), both tasks elicited changes in the 20-30 Hz beta frequency band but in different time windows, 350-550 ms for the phonological task and 500-700 ms for the semantic task. Our findings suggest that, where spatial measures may indicate overlapping areas of involvement, additional beamforming techniques can demonstrate differential activation in time and frequency domains.
    Frontiers in Psychology 01/2012; 3:273. · 2.80 Impact Factor
  • Sven Braeutigam, Stephen J Swithenby, Anthony J Bailey
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    ABSTRACT: Autism is a neurodevelopmental disorder associated with deficits in language and social communication. Behavioural studies indicate abnormal semantic organization in individuals with autism, but little is known about the neural mechanism underlying the processing of language in context. Magnetoencephalography was used to record neural responses in 11 able adults with autism spectrum disorders reading meaningful sentences and sentences ending with a semantically incongruous word (e.g. 'He sent a photo to the trumpet'). Spatially extended evoked signals at 400 ms (N4) and 750 ms (LPC), as well as synchronized gamma-oscillations, provided clear evidence for specific neuronal processes sensitive to sentence context that differed in individuals with autism compared with typically developing individuals (11 healthy volunteers). Amongst other differences, N4 responses following incongruous words were weaker over left temporal cortices, whereas LPC responses to incongruous words and long-latency gamma-oscillations following congruous words were stronger over central and prefrontal regions in individuals with autism compared with the control group. Also, incongruous words elicited long-lasting gamma-oscillations above 40 Hz in the clinical group, but not in typically developing subjects. These findings may indicate unusual strategies for resolving semantic ambiguity in autism. Moreover, the observed gamma-band responses provide evidence for sustained cortical synchronization across segregated areas in individuals with autism, contrary to claims that a general deficit in either temporal binding or long-range connectivity may explain autism.
    European Journal of Neuroscience 03/2008; 27(4):1026-36. · 3.75 Impact Factor
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    ABSTRACT: Face and gaze processing were studied using magnetoencephalography in 10 children with autism and 10 normally developing children, aged between 7 and 12 years. The children performed two tasks in which they had to discriminate whether images of faces presented sequentially in pairs were identical. The images showed four different categories of gaze: direct gaze, eyes averted (left or right) and closed eyes but there was no instruction to focus on the direction of gaze. Images of motorbikes were used as control stimuli. Faces evoked strong activity over posterior brain regions at about 100 ms in both groups of children. A response at 140 ms to faces observed over extrastriate cortices, thought to be homologous to the N170 in adults, was weak and bilateral in both groups and somewhat weaker (approaching significance) in the children with autism than in the control children. The response to motorbikes differed between the groups at 100 and 140 ms. Averted eyes evoked a strong right lateralized component at 240 ms in the normally developing children that was weak in the clinical group. By contrast, direct gaze evoked a left lateralized component at 240 ms only in children with autism. The findings suggest that face and gaze processing in children with autism follows a trajectory somewhat similar to that seen in normal development but with subtle differences. There is also a possibility that other categories of object may be processed in an unusual way. The inter-relationships between these findings remain to be elucidated.
    European Journal of Neuroscience 12/2006; 24(9):2679-90. · 3.75 Impact Factor
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    ABSTRACT: Magnetoencephalography (MEG) was used to study the neural mechanisms underlying face and gaze processing in ten normally developing boys aged between 8 and 11 years and 12 adult males. The participants performed two tasks in which they had to decide whether images presented sequentially in pairs, depicted the same person or the same motorbike. In the first task, the participants saw pictures of faces in which the eyes were either open or shut and pictures of motorbikes. In the second task, participants saw pairs of faces with gaze averted to the left or right. In children there was no evidence of the face sensitive, low amplitude short latency (30-60 ms) activity seen previously in adults. A strong, midline posterior response at approximately 100 ms was observed in children, which was earlier and somewhat stronger to faces than to motorbikes; in adults the signal at this latency was weak. A clear face sensitive response was seen in adults at 135 ms, predominantly over the right inferior occipito-temporal regions. Although activity was observed in the children at the same latency, it was less prominent, not lateralized and was evoked similarly by faces and motorbikes. Averted gaze conditions evoked strong right-lateralized activity at approximately 245 ms in children only. These findings indicate that even in middle childhood the neural mechanisms underlying face processing are less specialized than in adults, with greater early activation of posterior occipital cortices and less specific activation of ventral occipito-temporal cortex.
    European Journal of Neuroscience 03/2006; 23(3):801-10. · 3.75 Impact Factor
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    ABSTRACT: The neurological basis of developmental psychopathology in autism is a matter of intense debate. Magnetoencephalography (MEG) was used to study the neuronal responses associated with the processing of faces in 12 able adults with autism spectrum disorders (ASD), performing image categorization and image identification tasks. The neuromagnetic data were analysed using nonparametric time-series analysis and equivalent current dipole estimation. Comparison data were obtained from 22 normally developing adults. In individuals with ASD, the neural responses to images of faces, observed in right extrastriate cortices at approximately 145 ms after stimulus onset, were significantly weaker, less lateralized and less affected by stimulus repetition than in control subjects. Early latency (30-60 ms) responses to face images, over right anterior temporal regions, differed significantly between the two subject groups in the image identification task. No such difference was observed for images of mugs or meaningless geometrical patterns. These findings suggest that, during the course of development in individuals with ASD, the cortical activity associated with the processing of human faces assumes a different-from-normal localization in extrastriate brain regions. This abnormal localization may be associated with unusual, but nevertheless face-specific, fast processing pathways.
    European Journal of Neuroscience 06/2005; 21(9):2575-85. · 3.75 Impact Factor
  • Sven Braeutigam, Steven P R Rose, Stephen J Swithenby, Tim Ambler
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    ABSTRACT: In this work, magnetoencephalography was used to study the temporal dynamics of neural responses in 16 subjects (eight women, eight men) choosing among different day-to-day consumer items. At short latencies (< 150 ms), the evoked responses showed striate and extrastriate cortical activation common to the processing of general objects. At about 300 ms, women activated preferentially left posterior cortices, whereas men activated preferentially right temporal cortices. This may reflect sex/gender differences in cognitive strategies, emphasizing category-specific knowledge in women and spatial memories in men. At latencies greater than 500 ms, right parietal cortices were preferentially activated when previously bought or used items were chosen. In contrast, left inferior and right orbital cortices were preferentially activated when selecting less-known items. This may be interpreted as representing the neural correlates of decisions where the outcome is consistent with previous experience, and of choices which are 'difficult' in some sense. Analysis of coherent gamma-oscillations (20-45 Hz) revealed neural activity over left anterior and right dorsolateral cortices at long latency (> 1500 ms) when brand knowledge is low. This is consistent with the late binding of (brand) memories and evaluation of multiple sources of information when a choice is not obvious. gamma-Activity showed that women may activate larger neural networks when preference is high, suggesting that men and women exhibit different patterns of neural activity even though their overt performances are similar.
    European Journal of Neuroscience 08/2004; 20(1):293-302. · 3.75 Impact Factor
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    ABSTRACT: Noninvasive brain imaging was used to observe 18 subjects, each making 90 choices of three brands on a virtual (video) supermarket visit. Package height provided a control for the main experiment. Brain activations in brand choice differed from those for height discrimination, and choice times were faster when one brand was more familiar. Brand choice appeared to involve silent vocalization. Decision processes took approximately 1 s and can be seen as two halves. The first period seems to involve problem recognition and here male brain patterns differed from female. The second half concerned the choice itself. No male/female differences were observed but a different pattern was evoked where one brand was familiar and the other two were not. The right parietal cortex was strongly activated in this case. This research pioneers new techniques using relatively few subjects and against a limited theoretical background. As such it must be classified as exploratory.
    Psychology and Marketing 01/2004; · 1.13 Impact Factor
  • Sven Braeutigam, Stephen J Swithenby
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    ABSTRACT: The human ability to quickly recognise faces and objects is an important skill. This skill may be facilitated by the prior existence of context-setting functional brain states. MEG was used to test the hypothesis that such states may be defined neurophysiologically. One type of state was identified by evaluating deterministic features in the dynamics of pre-stimulus brain activity in 10 individuals engaging in an object categorisation task. These states followed a statistical gamma-distribution similar to that seen in models of percept duration of competing stimuli. Both an early (42 ms) and a late (440 ms) response were only seen for face stimuli that were presented during states in which the MEG data displayed low determinism. A second type of state was identified by evaluating amplitudes of pre-stimulus brain activity. Between 140 and 150 ms, activity was highest for face as well as non-face stimuli presented during a low amplitude state. These findings suggest that detectable states may provide an endogenous context for object processing, independently of experimental parameters.
    Neuroreport 08/2003; 14(10):1385-9. · 1.40 Impact Factor
  • Source
    Sven C.A. Braeutigam, Anthony J Bailey, Stephen J Swithenby
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    ABSTRACT: Electrophysiological responses to previously seen faces reportedly differ from those to novel faces at shorter latencies than generally associated with complex visual analysis. It is unclear, however, whether such observations are unique to faces, and which stages of visual processing they reflect. MEG was used in 21 normal adults to record neural responses to images of faces, other objects and abstract patterns presented individually as part of a classification task and in sequential pairs as part of an image comparison task. The amplitudes of the short latency responses (30-60 ms) to the first image in pairs of faces were significantly greater than the responses to both the second faces and the individual face images. These early responses were recorded over predominantly right hemisphere parietal and occipito-temporal cortical regions including areas that, at longer latencies, have been associated with face specific activity. The differences in the responses within pairs were less for non-face objects and absent for abstract geometrical patterns. No early neuronal activity was observed in the classification task. The results indicate the existence of early latency neural networks that are sensitive to both stimulus type and task and are strongly activated by faces.
    Neuroreport 06/2001; · 1.40 Impact Factor
  • Sven Braeutigam, Anthony J. Bailey, Stephen J. Swithenby
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    ABSTRACT: This paper addresses the role of γ-band activity in semantic networks associated with the processing of words and sentences in humans. Magnetoencephalography (MEG) was used to compare the responses of eleven normal volunteers to semantically congruous and incongruous words at the end of syntactically correct sentences. The averaged low frequency responses evoked by the two word classes were clearly different within the latency range associated with N400 components. The oscillatory characteristics of the evoked responses were analysed using Gabor transform techniques in conjunction with statistical re-sampling. This revealed transient γ-oscillations (∼35 Hz) that were significantly phase-locked to both types of stimuli but preferentially present at intermediate (∼300 ms) and long (>500 ms) latencies for incongruous words. This stimulus dependent phase locked γ-activity occurred at latencies that were distinct from the short latency and evoked N400 components. The findings suggest that synchronised oscillations provide independent information about brain dynamics and that some semantic processes may dissociate into distinct functional stages.
    Cognitive Brain Research 01/2001; 10(3):365–377. · 3.77 Impact Factor
  • Sven Braeutigam, Anthony J. Bailey, Stephen J. Swithenby
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    ABSTRACT: This paper addresses the role of γ-band activity in semantic networks associated with the processing of words and sentences in humans. Magnetoencephalography (MEG) was used to compare the responses of eleven normal volunteers to semantically congruous and incongruous words at the end of syntactically correct sentences. The averaged low frequency responses evoked by the two word classes were clearly different within the latency range associated with N400 components. The oscillatory characteristics of the evoked responses were analysed using Gabor transform techniques in conjunction with statistical re-sampling. This revealed transient γ-oscillations (∼35 Hz) that were significantly phase-locked to both types of stimuli but preferentially present at intermediate (∼300 ms) and long (>500 ms) latencies for incongruous words. This stimulus dependent phase locked γ-activity occurred at latencies that were distinct from the short latency and evoked N400 components. The findings suggest that synchronised oscillations provide independent information about brain dynamics and that some semantic processes may dissociate into distinct functional stages.
    Cognitive Brain Research 01/2001; 10(3):365-377. · 3.77 Impact Factor
  • NeuroImage 01/2001; 13(6):510-510. · 6.25 Impact Factor
  • Sven Braeutigam, Anthony J. Bailey, Stephen J. Swithenby
    Neuroreport 01/2001; 12(7):1531-1536. · 1.40 Impact Factor
  • Sven Braeutigam, Stephen Swithenby, Anthony Bailey
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    ABSTRACT: This chapter introduces a modern functional neuroimaging method, magnetoencephalography (MEG), and addresses how this technique is being applied to study dynamic brain actvity and neural processing in autism.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Face and gaze processing were studied using magnetoencephalography in 10 children with autism and 10 normally developing children, aged between 7 and 12 years. The children performed two tasks in which they had to discriminate whether images of faces presented sequentially in pairs were identical. The images showed four different categories of gaze: direct gaze, eyes averted (left or right) and closed eyes but there was no instruction to focus on the direction of gaze. Images of motorbikes were used as control stimuli. Faces evoked strong activity over posterior brain regions at about 100 ms in both groups of children. A response at 140 ms to faces observed over extrastriate cortices, thought to be homologous to the N170 in adults, was weak and bilateral in both groups and somewhat weaker (approaching significance) in the children with autism than in the control children. The response to motorbikes differed between the groups at 100 and 140 ms. Averted eyes evoked a strong right lateralized component at 240 ms in the normally developing children that was weak in the clinical group. By contrast, direct gaze evoked a left lateralized component at 240 ms only in children with autism. The findings suggest that face and gaze processing in children with autism follows a trajectory somewhat similar to that seen in normal development but with subtle differences. There is also a possibility that other categories of object may be processed in an unusual way. The inter-relationships between these findings remain to be elucidated.

Publication Stats

293 Citations
40.70 Total Impact Points

Institutions

  • 2006–2012
    • The Open University (UK)
      • Faculty of Science
      Milton Keynes, England, United Kingdom
    • University of Tampere
      • Department of Psychology
      Tampere, Western Finland, Finland
  • 2005–2008
    • University of Oxford
      • Department of Psychiatry
      Oxford, ENG, United Kingdom
  • 2001–2008
    • Milton Keynes College
      Milton Keynes, England, United Kingdom