null Kathleen Mullen, PhD
vision • colour vision • functional brain imaging (fMRI) • brain stimulation (TMS) • visual cortex
My research focuses on understanding how the brain enables us to see. I am especially interested in how the colour content of the visual scene is encoded and analyzed within the human brain. Initially, experimental approaches to colour vision were primarily concerned with the very first stage of vision, namely with identifying the visual pigments in the eye that absorb light. Although these first receptoral stages are a prerequisite for vision, they don't tell us about how colour is encoded, because the sensation of colour is created by the responses of the color opponent neurons found in the retina, visual pathways and the different areas of the visual cortex. In my experiments, I explore how the visual system encodes colour by the behavioral testing of human vision (psychophysics), the use of functional brain imaging, and brain stimulation. I also investigate the origins of colour vision deficits in different disease processes such as optic neuritis or glaucoma, and developmental visual dysfunction such as amblyopia.
Goddard, E., Chang, D.H.F., Hess, R.F. & Mullen, K.T. Color contrast adaptation: fMRI fails to predict behavioral adaptation. NeuroImage, 201, pp1-13, 2019. https://doi.org/10.1016/j.neuroimage.2019.116032. PMID: 31326574.
Mullen, K.T. The response to colour in the human visual cortex: the fMRI approach. Current Opinion in Behavioral Sciences, 30, pp 141-148, 2019. https://doi.org/10.1016/j.cobeha.2019.08.001.
Cohen, D., Goddard, E. & Mullen, K.T. Re-evaluating hMT+ and hV4 functional specialization for motion and static contrast using fMRI-guided repetitive transcranial magnetic stimulation (rTMS). Journal of Vision 19(3):11, 1–20, 2019. doi:10.1167/19.3.11. PMID: 30916726.
McIlhagga, W.H. & Mullen, K.T. Evidence for chromatic edge detectors in human vision using classification images. Journal of Vision, 18(9):8, 1–17, 2018. PMID: 30208428.
Goddard, E. & Mullen, K.T. fMRI Representational Similarity Analysis reveals graded preferences for chromatic and achromatic stimulus contrast across human visual cortex. J. NeuroImage, 215, 116780, April 2020. Doi:10.1016/j.neuroimage.2020.116780. PMID: 32276074.