Rosa Lafer-Sousa ’09, PhD
A Colorful Research Journey
I graduated from Wellesley College in 2009 with a B.A in Neuroscience, after which I carried out research as a Lab Manager in Dr. Bevil Conway’s lab at Wellesley College and Harvard Medical School. Last spring I graduated from Massachusetts Institute of Technology (MIT) with a PhD in Brain and Cognitive Sciences, working in Dr. Nancy Kanwisher’s lab. The focus of my thesis work was the perceptual and functional organization of color vision. I am now a postdoctoral research fellow at the National Institute of Mental Health (NIMH), Laboratory of Neuropsychology (LN), in Dr. Arash Afraz’s Unit on Neurons, Circuits, and Behavior (UNCB). The main focus of the lab is uncovering the causal links between the neural activity in the ventral stream of the visual pathway and behavior.
My research aims to shed light on the neural architecture of the visual system and establish links between brain activity and perception, with a focus on Color as a model system. Color is a fundamental aspect of visual experience that confers a myriad of behavioral advantages: finding objects in cluttered scenes, recognizing familiar objects, and gleaning information about the material composition and state of objects (e.g. the edibility of fruit) and agents in the world (e.g. health or emotional status). As famously pointed out by Marr (1980), a full understanding of perception requires an analysis of the computations performed, the algorithms that carry out those computations, and the implementation of those algorithms in the physical hardware of the brain. My work to date has employed psychophysical methods and functional imaging to tackle questions about human color vision at all three levels: what it is used for, how we solve the classic problem of color constancy, and how our color processing machinery is functionally organized in the brain. I have carried out functional MRI studies in humans and macaques that found both segregation and convergence of the processing of color and shape in the brain, as well as evidence for the homology of the color system between humans and macaques. I have used psychophysics and a recently discovered ambiguous color stimulus (‘#theDress’) to investigate the cues and assumptions used by the human visual system to constrain the classic ill-posed problem of inferring the intrinsic reflectance of an object by discounting the spectral properties of the illuminant. Specifically, these studies found evidence that color constancy is mediated by sensory, perceptual, and cognitive factors (i.e., low-level features, inferences about 3D scene geometry, prior knowledge, and attention), and provide the first evidence that human skin is a sufficient cue to infer the illuminant and bring about color constant percepts. Most recently, I used psychophysics to evaluate the impact of memory on the color appearance of familiar objects and faces. The study found a novel perceptual illusion that reveals the role of memory for face color in perceptual experience and social communication, sheds light on the selective pressures for the evolution of trichromatic vision in primates, and demonstrates the powerful ability of cognition to influence perception. Taken together, these studies provide clues about the perceptual and neural mechanisms underlying our rich experience of a colorful world.
Producing this body of work and making my way from wide-eyed undergraduate huddled in the Wellesley College science center to full-blown research scientist has not been without its challenges. In this talk I will touch on key moments, both personal and academic, in my colorful research journey.