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.
Kaderali, S., Kim, Y.J., Reynaud, A. and Mullen, K.T. The role of human brain area hMT+ in the perception of global motion investigated with repetitive transcranial magnetic stimulation (rTMS). Corrected proofs available on line: Brain Stimulation, 8(2), 200-207, 2015. PMID: 25440579.
Mullen, K.T., Kim, Y.J. & Gheiratmand, M. Contrast normalization in colour vision: the effect of luminance contrast on colour contrast detection. Scientific Reports, 4, 7350, pp1-8. DOI:10.1038/srep07350 (2014). PMID: 25491564.
Gheiratmand, M. & Mullen, K.T. Orientation tuning in human color vision at detection threshold. Scientific Reports, 4, Article number 4285, pp1-10, 2014. PMID: 24594749.
Ivanov, I.V., Kramer, D.J. & Mullen, K.T. The role of the foreshortening cue in the perception of 3D object slant. Vision Research, 94, 41-50, 2014. PMID: 24216007.
Al-Hashmi, A.M., Kramer, D.J. & Mullen, K.T. Human vision with a lesion of the parvocellular pathway: an optic neuritis model for selective contrast sensitivity deficits with severe loss of midget ganglion cell function. Experimental Brain Research, 215, pp293-305, 2011. PMID: 22006271.