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Dive into the research topics where D Birtles is active.

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Featured researches published by D Birtles.


Journal of Vision | 2010

Brain responses to global perceptual coherence

Oliver Braddick; D Birtles; Susanna Mills; Julien Warshafsky; John Wattam-Bell; Janette Atkinson

Coherence thresholds for concentric patterns of contour segments or dot trajectories have revealed differential development and vulnerability of extrastriate form and motion pathways respectively (Braddick et al, Neuropsychologia, 2003). Here we explore the properties of visual evoked potentials (VEPs) specific to form and motion coherence. Coherent contour or motion arrays alternate with incoherent arrays at 0.5-4 Hz. A 2nd harmonic VEP signal (F2) may arise from local changes occuring at each transition, but a first harmonic (F1) must reflect differential responses to coherence and incoherence, indicating global processing. F1 amplitude is approximately linear with coherence for both form and motion, confirming that F1 measures global processing. F2 is independent of coherence for form, and nearly so for motion, implying that it reflects local changes. Occipital F1 amplitudes for motion: form coherence are approximately 2:1. However, this does not reflect underlying sensitivity: psychophysical form and motion coherence thresholds are similar, and extrapolation of the linear region of F1 amplitude vs coherence reaches zero close to threshold coherence in each case. F1 amplitude for both displays increases gradually from 0.5-4 Hz. However, this is opposite to psychophysical coherence sensitivity, which falls over the same range. We conclude: (a) coherence-dependent VEPs provide measures of global form and motion processing, practical for infants and non-verbal (e.g. autistic) children; (b) this response is elicited efficiently at relatively high presentation rates; (c) the level tapped by the VEP does not provide the limiting factor on temporal integration in global perceptual processing.


Current Biology | 2010

Reorganization of Global Form and Motion Processing during Human Visual Development

John Wattam-Bell; D Birtles; Pär Nyström; Claes von Hofsten; Kerstin Rosander; S Anker; Janette Atkinson; Oliver Braddick


Investigative Ophthalmology & Visual Science | 2003

Role of connective tissue growth factor in the pathogenesis of conjunctival scarring in ocular cicatricial pemphigoid

Janette Atkinson; Oliver Braddick; S Anker; D Birtles; A Barnett; David Edwards; Frances Cowan; Mary A. Rutherford; Eugenio Mercuri; A Mason


Journal of Vision | 2004

Form vs motion coherence sensitivity in infants: the dorsal/ventral developmental debate continues

Janette Atkinson; John Wattam-Bell; Oliver Braddick; D Birtles; Anna Barnett; Dorothy Cowie


Perception | 2007

High-density VERPs to global form and motion in adults and infants

John Wattam-Bell; Pär Nyström; Oliver Braddick; D Birtles; Janette Atkinson; Kerstin Rosander; C von Hofsten


In: PERCEPTION. (pp. 3 - 3). PION LTD (2006) | 2006

Evoked potentials specific to global visual coherence in adults and infants

J Braddick; D Birtles; J Warshafsky; F Akthar; John Wattam-Bell; Janette Atkinson


Journal of Vision | 2011

Locating ‘dorsal stream vulnerability': high-density global motion and form coherence VEPs related to MRI in infants born very preterm

Janette Atkinson; D Birtles; S Anker; John Wattam-Bell; Mary A. Rutherford; Frances Cowan; David Edwards; Michela Groppo; Oliver Braddick


Investigative Ophthalmology & Visual Science | 2011

Development Of Pattern- And Orientation-reversal Latencies In Healthy Infants And Those At Risk Of Cerebral Palsy

Jin Lee; Morag Andrew; D Birtles; John Wattam-Bell; Janette Atkinson; Oliver Braddick


Perception | 2014

Immature ERP topography, MRI and global motion responses in preterm-born infants

D Birtles; Janette Atkinson; S Anker; John Wattam-Bell; Mary A. Rutherford; Frances Cowan; D Edwards; M Groppo; Oliver Braddick


Journal of Vision | 2011

Development of visual motion processing: Latency of direction-specific VEP in infants compared to adults

Jin Lee; D Birtles; John Wattam-Bell; Janette Atkinson; Oliver Braddick

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S Anker

University College London

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Jin Lee

University of Oxford

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