Chen (Roger) Zhao PhD

Chen (Roger) Zhao


Publications:
2016
  Validating human stem cell derived neural cultures as a flexible model system in which to investigate neurodegenerative mechanisms
Alibhai, JD, Krejciova, Z, Zhao, C, Rzechorzek, NM, Manson, JC, Ironside, JW, Chandran, S & Head, MW 2016, 'Validating human stem cell derived neural cultures as a flexible model system in which to investigate neurodegenerative mechanisms' Prion, vol 10, no. Suppt. 1, P-028, pp. S51-S52. DOI: 10.1080/19336896.2016.1162644
General Information
Organisations: Edinburgh Imaging Facilities.
Authors: Alibhai, James D., Krejciova, Zuzana, Zhao, Chen, Rzechorzek, Nina M., Manson, Jean C., Ironside, James W., Chandran, Siddharthan & Head, Mark W..
Number of pages: 2
Pages: S51-S52
Publication Date: 18 Apr 2016
Publication Information
Category: Meeting abstract
Journal: Prion
Volume: 10
Issue number: Suppt. 1
ISSN: 1933-6896
Original Language: English
DOIs: 10.1080/19336896.2016.1162644
2011
  Similar neural adaptation mechanisms underlying face gender and tilt aftereffects
Zhao, CR, Series, P, Hancock, PJB & Bednar, JA 2011, 'Similar neural adaptation mechanisms underlying face gender and tilt aftereffects' Vision Research, vol 51, no. 18, pp. 2021-2030. DOI: 10.1016/j.visres.2011.07.014
Visual aftereffects have been found for a wide variety of stimuli, ranging from oriented lines to human faces, but previous results suggested that face aftereffects were qualitatively different from orientation (tilt) aftereffects. Using computational models, we predicted that these differences were due to the limited range of faces used in previous studies. Here we report psychophysical results verifying this prediction. We used the same paradigm to test tilt aftereffects (TAE) and face gender aftereffects (FAE) and found that they exhibited qualitatively similar aftereffect curves, when a sufficiently large range of test faces was used. Overall, the results suggest that similar adaptation mechanisms may underlie both high-level and low-level visual processing.
General Information
Organisations: Institute for Adaptive and Neural Computation .
Authors: Zhao, Chen (Roger), Series, Peggy, Hancock, Peter J. B. & Bednar, James A..
Keywords: (Aftereffects, Visual cortex, Face recognition, Computational modeling, Ophthalmology, Sensory Systems, , , . )
Number of pages: 10
Pages: 2021-2030
Publication Date: Sep 2011
Publication Information
Category: Article
Journal: Vision Research
Volume: 51
Issue number: 18
Original Language: English
DOIs: 10.1016/j.visres.2011.07.014
2010
  Modelling curve adaptation effects on high-level facial-expression judgments
Zhao, CR & Bednar, JA 2010, 'Modelling curve adaptation effects on high-level facial-expression judgments' 33rd European Conference on Visual Perception, Lausanne, Switzerland, 22/08/10 - 26/08/10, .
Hong Xu et al. (2008 J. Neuroscience 28:3374-83) recently showed that adaptation to curved lines can affect high-level perception of emotional affect in faces, presumably by modifying the perception of mouth curvature. For the patterns tested so far, the effect increases as the adaptation pattern curvature increases. However, standard low-level aftereffects like tilt and motion aftereffects (TAE MAE) typically show an S-shaped curve, with a decline in aftereffect strength for test patterns sufficiently different from the adaptation stimulus. In computational models of the TAE, the S-shape reflects adaptation in neurons that prefer a particular orientation, with neurons preferring very different orientations having little adaptation and thus showing weaker aftereffects. To see whether a similar explanation might apply to curvature/emotion aftereffects, we adapted an existing model of the TAE for use with curved lines and added processing for emotion judgments. We found that the model replicated the existing data on high-level effects of low-level adaptation, but strongly predicted an S-shape, ie that sufficiently large curvature values would lead to a lower effect. This prediction can be tested in humans, potentially helping to constrain the properties of the neurons underlying the effect.
General Information
Organisations: Institute for Adaptive and Neural Computation .
Authors: Zhao, Chen (Roger) & Bednar, James A..
Publication Date: 2010
Publication Information
Category: Poster
Original Language: English
  Curve adaptation effects on high-level facial-expression judgments are predicted to have the same form as low-level aftereffects
Zhao, CR & Bednar, JA 2010, 'Curve adaptation effects on high-level facial-expression judgments are predicted to have the same form as low-level aftereffects' Perception, vol 39, no. EVCP Abstract Supplement, pp. 91-91.
Hong Xu et al. [Hong Xu et al, 2008 Journal of Neuroscience 28(13) 3374-3383] recently showed that adaptation to curved lines can affect high-level perception of emotional affect in faces, presumably by modifying the perception of mouth curvature. For the patterns tested so far, the effect increases as the adaptation pattern curvature increases. However, standard low-level aftereffects like tilt and motion aftereffects (TAE & MAE) typically show an S-shaped curve, with a decline in aftereffect strength for test patterns sufficiently different from the adaptation stimulus. In computational models of the TAE, the S-shape reflects adaptation in neurons that prefer a particular orientation, with neurons preferring very different orientations having little adaptation and thus showing weaker aftereffects. To see whether a similar explanation might apply to curvature/emotion aftereffects, we adapted an existing model of the TAE for use with curved lines and added processing for emotion judgments. We found that the model replicated the existing data on high-level effects of low-level adaptation, but strongly predicted an S-shape, ie that sufficiently large curvature values would lead to a lower effect. This prediction can be tested in humans, potentially helping to constrain the properties of the neurons underlying the effect.
General Information
Organisations: Institute for Adaptive and Neural Computation .
Authors: Zhao, Chen (Roger) & Bednar, J. A..
Number of pages: 1
Pages: 91-91
Publication Date: 2010
Publication Information
Category: Meeting abstract
Journal: Perception
Volume: 39
Issue number: EVCP Abstract Supplement
ISSN: 0301-0066
Original Language: English
2008
  Modelling face adaptation aftereffects
Zhao, CR, Hancock, P & Bednar, JA 2008, 'Modelling face adaptation aftereffects' 31st European Conference on Visual Perception, Utrecht, Netherlands, 24/08/08 - 28/08/08, .
Human perception of faces shows systematic aftereffects as a result of adaptation to specific faces (Leopold et al, 2001 Nature Neuroscience 4 89 - 94), but it is not clear what mechanisms underlie these effects. We show that face aftereffects can arise from Hebbian learning of connections in a LISSOM self-organising map model of visual cortex (Miikkulainen et al, 2005 Computational Maps in the Visual Cortex (New York: Springer)). The model is trained and tested on faces from a generative model of a multi-dimensional face space (Hancock, 2000 Behavior Research Methods, Instruments and Computers 32 327 - 333). Adaptation in the model shifts perception along a trajectory passing through the mean face. The perception of a target face on this trajectory is facilitated after adaptation to the target face's anti-face, but impaired after adaptation to other anti-faces. The model results suggest that high-level aftereffects can be explained through the same mechanisms previously used for low-level effects like tilt aftereffects (Miikkulainen et al, 2005 Computational Maps in the Visual Cortex (New York: Springer), but in circuits selective for faces.
General Information
Organisations: Institute for Adaptive and Neural Computation .
Authors: Zhao, Chen (Roger), Hancock, Peter & Bednar, James A..
Publication Date: 2008
Publication Information
Category: Poster
Original Language: English
2007
  Face Aftereffects Improve Discriminability for Similar Faces
Zhao, CR & Hancock, P 2007, 'Face Aftereffects Improve Discriminability for Similar Faces' 30th European Conference on Visual Perception, Arezzo, Italy, 27/08/07 - 31/08/07, .
Previous studies have demonstrated a face-identity aftereffect that facilitates face-identification performance (Leopold et al, 2001 Nature Neuroscience 4 89 - 94). Adaptation should improve discrimination between faces in the region of the adapting stimulus, but this has not previously been demonstrated. We report an investigation on face discrimination, using faces distorted with Photoshop spherize function making them either expanded or compressed. We did psychophysical experiments on thirteen participants using an adaptive Bayesian method in order to present stimuli efficiently and effectively. The participants were adapted to systematically distorted faces (-160% or +160 and then tested on discrimination sensitivity around both +160% and -160 The results show that discrimination is facilitated at -160% after repetitive adaptation to -160% faces, but not significantly facilitated at +160% following adaptation to +160 Overall, there is a significant shift in discriminability with adaptation condition. We conclude that face discrimination can be facilitated at the point of adaptation but that demonstrating such an improvement will require a more tightly controlled stimulus presentation protocol.
General Information
Organisations: Neuroinformatics DTC.
Authors: Zhao, Chen (Roger) & Hancock, Peter.
Publication Date: 2007
Publication Information
Category: Poster
Original Language: English
2006
  An investigation of the face discrimination function facilitated by face adaptation aftereffect using Bayesian adaptive estimation of stimuli
Zhao, CR 2006, 'An investigation of the face discrimination function facilitated by face adaptation aftereffect using Bayesian adaptive estimation of stimuli'.
General Information
Organisations: Neuroinformatics DTC.
Authors: Zhao, Chen (Roger).
Publication Date: 2006
Publication Information
Category: Poster
Original Language: English

Projects:
Modelling and psychophysical tests on face adaptation aftereffects (PhD)