Russell D. Hamer

Affiliate Research Professor
Department of Psychology
Florida Atlantic University
777 Glades Road
Boca Raton, FL 33431 USA


Office: 561.297.1276
Email:rhamer@fau.edu
russhamer2@gmail.com


Office is in Behavioral Sciences Bldg BS-12, Room 212

Professor Visitante Especial
Departamento de Psicologia Experimental
Instituto de Psicologia
Universidade de São Paulo
Av. Prof. Mello Moraes, 1721
Cidade Universitaria 05508 030
Sao Paulo, SP, BRASIL

Affiliate Scientist
Smith-Kettlewell Eye Research Institute
2318 Fillmore Street
San Francisco, CA, 94115 USA

   
Photo by Peter Menzel, NY Times Magazine, March 5, 1989

Dr. Hamer is an Affiliate Research Professor in the Psychology Department at Florida Atlantic University at Boca Raton.  His current research focus is on the neuroscientific bases of rhythm.  Specifically, he is developing a program to study rhythm production and perception, using synchronization and syncopation and continuation paradigms to evaluate the temporal precision, variability and adaptability of internal timing mechanisms.  Highly skilled professional percussionists will generate polyrhythms (non-isochronous) in a naturalistic musical environment using their percussive skills and musical training while playing Afro-Cuban rhythms on various hand-drums.  The experimental setting is designed to evoke optimal, musically engaging performance from the participants under the expectation that this will evoke the strongest internal rhythmical responses (“In the pocket!  In the groove!”).  Dr. Hamer’s interest in this topic derives from a long-abiding love of Afro-Cuban music and dance. He has, in fact, taught Cuban Salsa dance for over 22 years.

Prior to the current project, his long career in Sensory-Perceptual neuroscience has spanned a diverse range of topics:

Human Mechanoreception
His Ph.D. at the Institute for Sensory Research at Syracuse University focused on vibrotactile psychophysics and modeling of mechanoreceptor channels in humans obtained. His dissertation work introduced a model to account for human vibration sensitivity that was tied to the underlying physiology of the mechanoreceptors in human skin.  The model predicted his new finding of so-called negative masking, when a masking stimulus that itself was sub-threshold could nevertheless enhance the detectability of an incremental stimulus by as much as 15 decibels.

Behavioral Measures of Human Visual Development
Dr. Hamer next applied his expertise in psychophysical methods to behavioral measures of visual development of human infants, starting with an invaluable Postdoctoral Fellowship with Prof. Davida Y. Teller in the Psychology Department at the University of Washington, Seattle, WA.  There he focused on development of color vision over the first postnatal months, and on the development of scotopic (night) vision and spatial integration.  His work was among the first objective demonstrations of color vision in infants as young as 4 weeks of age.

Electrophysiological Measures of Human Visual Development
Over the next decade and a half, Dr. Hamer continued research on visual development, but now utilizing the efficient and sensitive methods of steady-state electrophysiology (brain wave measures of visual responses using the visual evoked potential, VEP). This work was done in the laboratory of Dr. Anthony M. Norcia at the Smith-Kettlewell Eye Research Institute in San Francisco, CA.  The research examined development of monocular and binocular grating acuity, contrast sensitivity and motion sensitivity.

In addition, Norcia, Hamer and colleagues showed that infants who had experienced interruption of normal binocular development (due to strabismus, for example) maintained strong monocular motion asymmetries in their steady-state motion-evoked responses even into adulthood. The nature of the asymmetry was a substantial difference in mVEP amplitude when periodically oscillating vertical sinewave gratings moved leftward vs when they moved rightward.  In contrast, normal infants’ (monoc) motion VEPs  mature quickly over the first 1-2 years and become symmetrical.  The research thus introduced a monocular index of binocular maturation that was adopted in a number of other labs.

Adult Spatiotemporal Vision
In parallel with this work, Dr. Hamer worked with Dr. Christopher W. Tyler on adult spatiotemporal vision, analyzing human sensitivity to flicker as a function of light level.  They were able to show flicker detection at very high frequencies (up to 100 Hz) in the periphery of vision, and showed that the peripheral visual field was substantially faster than the fovea, which had a maximum flicker frequency of only 50 Hz.  In addition, they established optimal stimulus parameters to use in measures of temporal processing that took into account retinal inhomogeneities of temporal sensitivity.

Modeling Phototransduciton
Dr. Hamer investigated the detail of phototransduction, how rods and cones convert light energy into a bio-electric signal. He received funding for this project from the National Eye Institute of NIH. With colleagues from New York University, University of Pennsylvania, Australian National University and Smith-Kettlewell, he developed a computational model of phototransduction that accounted for a wide range of physiological data. 

Measures of Abnormal Vision in Infants and Adults
He left Smith-Kettlewell in 2006 (maintaining an Affiliate status to the present day) and joined a lab in the Instituto de Psicologia at the Universidade de Sao Paulo (USP), in Sao Paulo, Brasil where he was a Visiting Professor teaching graduate students Sensation & Perception, Retinal Physiology and Phototransduction  and Visual Development.  His developmental research at USP overlapped his work at Smith-Kettlewell in that he continued with studies of visual development using the steady-state VEP approach.  The work focused on examining infants born small for gestational age who had experienced inadequate nutrition during gestation.  In this project, one graduate student received her Ph.D. under Dr. Hamer. 

Dr. Hamer also studied psychophysically contrast processing in adults who were carriers of a devastating retinal disease, Leber’s Hereditary Optic Neuropathy.

VEP Measures of Vernier and Contrast Processing Channels in Adults
Projects at USP also included studying Vernier processing in normal adults using the VEP as a function of contrast and spatial frequency.  Two graduate students received their Ph.D.s under Dr. Hamer while working on these projects.

In collaboration with scientists from the Universidade Federal do Para in Belem, Brasil, Dr. Hamer developed an approach to  reveal contrast processing channels from VEP data.

Editorships
While in Brasil. Dr. Hamer was invited to be an editor on the boards of Psychology & Neuroscience and Psicologia USP.

Selected Publications
Hamer RD (2016). The visual world of infants. American Scientist 104: 96-101.
Hamer RD, Carvalho, FA & Ventura DF. (2013). Effect of contrast and gaps on sweep VEP measurement of human cortical vernier responses. Psychology & Neuroscience.6(2): 199-212. PDF
Gualtieri M, Bandeira M, Hamer RD, Damico FM, Moura ALA, Ventura DF. (2011) Contrast sensitivity mediated by inferred magno- and parvocellular pathways in type 2 diabetics with and without non-proliferative retinopathy. Invest Ophthalmol. Vis Sci. 52: 1151-1155. PubMed
Hamer, RD & Norcia, AM (2009) The Jitter Spatial Frequency Sweep VEP: a new paradigm to study spatiotemporal development of pattern- and motion-processing mechanisms in human infants. Psychology & Neuroscience 2: 163-177. PDF
Hamer, RD, Nicholas, SC, Tranchina, D, Lamb, TD & Jarvinen, JLP. (2005) Towards a unified model of vertebrate rod phototransduction. Visual Neuroscience, 22: 417-436. PubMed
Hamer, R.D., Nicholas, S.C., Tranchina, D., Liebman, P.A. & Lamb, T.D. (2003). Multiple steps of phosphorylation of activated rhodopsin can account for the reproducibility of vertebrate rod single-photon responses. Journal of General Physiology, 122: 377-402. PDF
Hamer, R.D. (2000b). Analysis of Ca++-dependent gain changes in PDE-activation in vertebrate rod phototransduction . Molecular Vision 6, 265-286. PDF
Hamer RD, Norcia AM (1994) The development of motion sensitivity during the first year of life. Vis. Res. 34, 2387-2402.
Hamer, R.D. and Mayer, D.L. (1994) The development of spatial vision. In: Principles and Practice of Ophthalmology, Chapter 42, Albert DM, Jakobiec FA (Eds.), W.B. Saunders Co., Philadelphia, PA., pp. 578-608.
Hamer RD, Tyler CW (1992) Analysis of visual modulation sensitivity. V. Faster visual response for G- than for R-Cone pathway? J. Opt. Soc. Am.A , 9, 1889-1904.
Norcia AM, Tyler CW, Hamer RD. (1990) Development of contrast sensitivity in the human infant. Vision Res.; 30(10): 1475-86.
Hamer RD, Verrillo RT, Zwislocki JJ. (1983) Vibrotacile masking of Pacinian and non-Pacinian channels. J Acoust Soc Am.; 73(4): 1293-303.
Hamer RD, Alexander KR, Teller DY. (1982) Rayleigh discriminations in young human infants. Vision Res.; 22(5): 575-577.