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Dr. Ralph Mitchell Siegel, a member of the Editorial Board of Brain Structure and Function and a researcher who studied the neurological underpinnings of vision, died September 2 at his home following a long illness. He had been a professor of neuroscience at Rutgers University, Newark, in the Center for Molecular and Behavioral Neuroscience.

As a trained neurophysiologist, Ralph was interested in basic mechanisms underlying visual motion and spatial perception, with the ultimate goal of developing applications to assist people who have visual processing disorders and neurological injuries. He performed pioneering work on parietal neurons and the influence of eye position and attention on perception. His laboratory became the first to perform optical imaging of parietal cortex in behaving non-human primates.

Siegel earned his B.S. in physics and his Ph.D. in physiology from McGill University in Montreal. After completing his graduate studies at McGill on the theoretical neuroscience of spike propagation in branched dendrites, Ralph moved to the Salk Institute in La Jolla, CA, where he began to focus on in vivo, behavioral neurophysiology of monkeys in the lab of then assistant professor Richard Andersen. Recalls Dr. Jim Gnadt, now at NIH, “Ralph was a vibrant and energetic member of a lab at the forefront of experimental studies to understand the neurophysiology of cognitive processes in primates in the early 1980s. He was an early contributor to the gain-field mechanisms of neuronal population encoding, and employed precise psychophysical methods to understand visual motion perception at the level of neuronal activity. From beginning to end, Ralph employed quantitative methods in his studies and conversed fluently in a range of topics from physics to psychophysics, to metaphysics. It was also during his time at the Salk that Ralph first made acquaintance with his mentor Francis Crick and his wife Jasmine, whom he married in 1988.”

In 1987 Ralph began a postdoctoral position in the laboratory of Nobel Prize winner Torsten Wiesel at Rockefeller University. While at Rockefeller, Ralph nurtured a latent interest in theoretical studies of cortical visual processing. He also got his feet wet in the rapidly emerging field of optical imaging of cortex, through collaboration with a pioneering group led by Amiram Grinvald.

After being hired by Rutgers, but while waiting for his new laboratory at Rutgers, Newark, to be completed, Ralph took a position as a visiting scientist at IBM’s Watson Laboratories in Yorktown Heights, where he happily cavorted with leading physicists and mathematicians of his day, such as Benoit Mandelbrot, and fully indulged his penchant for theoretical neuroscience. The impact of this early internship at IBM—particularly the insight Ralph gained concerning neuronal circuits as non-linear dynamical systems—was prominent throughout his career.

In 1991, Ralph moved into his laboratory at the newly established Rutgers Center for Molecular and Behavioral Neuroscience (CMBN), in Newark, New Jersey, where he was on the faculty for the remainder of his career. Ralph Siegel was one of the first faculty members to be recruited to the new CMBN. As Ralph’s research spanned broadly from system neurophysiology to psychophysics to computational models of complex visual processing, he was an ideal faculty member for an integrative neuroscience center envisaged by the Co-directors, Paula Tallal and Ian Creese, when they moved from UCSD to Rutgers in the late 1980s. In his early years at Rutgers, Ralph continued his pioneering neurophysiological and behavioral work on the organization and functions of visual cortex in the parietal lobe. At the same time, he and Jasmine raised beautiful twins, Zoe and Dashiel. During this period, Ralph also maintained his scientific collaborations with his former colleagues at the Salk Institute, making annual summer visits to La Jolla over the next decade. A major feature of these collaborations, and of Ralph’s evolving research program over the last decade of his career at Rutgers, was the use of optical microscopic techniques to monitor neuronal activity in the cerebral cortex. In collaboration with Ed Callaway (Salk) and Ehud Isacoff (Berkeley) Ralph began to develop tools that enabled optical monitoring of activity from neurons in behaving animals—tools that have since set the stage for a revolution in functional neurobiology.

Professor Tom Albright, a long-time friend and colleague at the Salk Institute, remembers Ralph this way, “From the earliest days of his scientific career, Ralph was an iconoclast—ever thinking outside the box, courageously questioning the perceived wisdom and pushing the boundaries of his field. At the same time, Ralph became known and loved far and wide for his extraordinarily passionate approach to science, family and friendship, his hearty joie de vivre and his generous spirit. Ralph thrived on his ability to excite, to provoke and to inspire those around him. He danced without pause through his short life.”

Next year Siegel’s first book and memoir, Another Day in the Monkey’s Brain, will be published, by Oxford University Press, with the help of his life-long friend and colleague, Dr. Oliver Sacks. In memory, we will always picture Ralph with a sly grin, raised eyebrow, shock of red hair and a twinkle in his eye. He will be dearly missed.

Publications of Ralph M. Siegel

Book

Another Day in the Monkey’s Brain. Oxford University Press. (in press)

Letter

Sacks O, Siegel RM (2006) Seeing is believing as brain reveals its adaptability. Nature. 441(7097):1048.

Refereed papers

  1. 1.

    Heider, B, Nathanson, J, Callaway, E, Isacoff, EY, Siegel, RM (2010) Two-photon imaging of calcium in virally transfected striate cortical neurons of behaving monkey. PLoS ONE 5(11):e13829.

  2. 2.

    Heider B, Karnik A, Ramalingam N, Siegel RM (2010) Neural representation of visually guided reaching in macaque posterior parietal cortex. J Neurophysiol 04:3494–3509.

  3. 3.

    Khaytin I, Chen X, Royal DW, Ruiz O, Jermakowicz WJ, Siegel RM, Casagrande VA (2007) Functional organization of temporal frequency selectivity in primate visual cortex. Cereb Cortex Adv Access. doi:10.1093/cercor/bhm210

  4. 4.

    Raffi M, Siegel RM (2007) A functional architecture of optic flow in the inferior parietal lobule of the behaving monkey. PLoS ONE 2(2):e200.

  5. 5.

    Quraishi S, Heider B, Siegel RM (2007) Attentional modulation of receptive field structure in area 7a. Cereb Cortex 17(8):1841–1857. (Epub 2006 Oct 31).

  6. 6.

    Siegel RM, Duann. J-R, JungTP, Sejnowski T (2007) Spatiotemporal dynamics of the functional architecture for gain fields in inferior parietal lobule of behaving monkey. Cereb Cortex 17(2):378–390. [Epub 2006).

  7. 7.

    Raffi M, Siegel RM (2005) Functional architecture of spatial attention in the parietal cortex of behaving monkey. J Neurosci 25(21):5171–5186.

  8. 8.

    Anderson KC, Siegel RM (2005) Three-dimensional structure-from-motion selectivity in the anterior superior temporal polysensory area, STPa, of the behaving monkey. Cereb Cortex 15(9):1299–1307. (Epub 2005 Jan 12).

  9. 9.

    Heider B, Siegel RM (2005) Functional architecture of retinotopy in visual association cortex of behaving monkey. Cereb Cortex 15(4):460–478.

  10. 10.

    Siegel RM, Raffi M, Phinney RE, Turner JA, Jando G (2003) Functional architecture of eye position gain fields in visual association cortex of behaving monkey. J Neurophysiol 90(2):1279–1294. (Epub 2003 Apr 02).

  11. 11.

    Turner JA, Anderson KC, Siegel RM (2003) Cell responsiveness in macaque superior temporal polysensory area measured by temporal discriminants. Neural Comput 15(9):2067–2090.

  12. 12.

    Siegel, R.M. and Read, H.L. Deterministic dynamics of a cortical functional architecture. Neural Networks, Jul-Sep;14(6–7):697–713 (2001).

  13. 13.

    Phinney RE, Siegel RM (2000) Speed selectivity for optic flow stimuli in macaque area 7a. Cereb Cortex 10:413–421.

  14. 14.

    Phinney RE, Siegel RM (1999) Stored representations of three-dimensional objects in the absence of two-dimensional cues. Perception 28:725–737.

  15. 15.

    Anderson KA, Siegel RM (1999) Optic flow selectivity in the area STPa of the behaving monkey. J Neurosci 19(7):2681–2692.

  16. 16.

    Anderson KA, Siegel RM (1998) Lack of selectivity for simple shapes defined by motion and luminance in STPa of the behaving macaque. Neuroreport 9:2063–2070.

  17. 17.

    Siegel RM (1998) Representation of visual space in area 7a neurons: a theoretical approach using the center of mass equation. J Comput Neurosci 5(4):365–381.

  18. 18.

    Siegel RM, Read HL (1997) Analysis of optic flow in the monkey parietal area 7a. Cereb Cortex 7:327–346.

  19. 19.

    Read HL, Siegel RM (1997) Modulation of responses to optic flow in area 7a by retinotopic and oculomotor cues in monkey. Cereb Cortex 7:647–661.

  20. 20.

    Read HL, Siegel RM (1997) The origins of aperiodicities in sensory neuron entrainment. Neuroscience 75:301–314.

  21. 21.

    Teich MC, Turcott RG, Siegel RM (1996) Temporal correlation in cat striate cortex: neural spike trains. IEEE Biomed Eng 15:79–87.

  22. 22.

    Jandó G, Siegel RM, Horváth Z, Buzsáki G (1993) Pattern recognition of the electroencephalogram by artificial neural networks. Electroenceph Clin Neurophysiol 86:100–109.

  23. 23.

    Siegel RM, Read HL (1993) Models of the temporal dynamics of visual processing. J Stat Phys 70:297–308.

  24. 24.

    Spitz RV, Stiles-Davis J, Siegel RM (1993) Infant use of relative motion as information for form: evidence for spatiotemporal integration of complex motion displays. Perception Psychophys 53:190–199.

  25. 25.

    Siegel RM, Tresser C, Zettler G (1992) A decoding problem in dynamics and number theory. Chaos 2:473–494.

  26. 26.

    Grinvald A, Frostig RD, Siegel R, Bartfield E (1991) High resolution optical imaging of functional architecture in striate cortex of behaving monkey. PNAS 88:11559–11563.

  27. 27.

    Rockmore D, Siegel R, Tongring N, Tresser T (1991) An approach to renormalization on the n–torus. Chaos 1:25–30.

  28. 28.

    Siegel RM, Andersen RA (1990) The perception of structure from visual motion in monkey and man. J Cogn Neurosci 2:306–319.

  29. 29.

    Siegel RM (1990) Non–linear dynamical system theory and primary visual cortical processing. Physica D 42:385–395.

  30. 30.

    Andersen RA, Asanuma C, Essick GK, Siegel RM (1990) Cortico-cortical connections of anatomically and physiologically defined subdivisions within the inferior parietal lobule. J Comput Neurol 296:65–113.

  31. 31.

    Ratzlaff G, Siegel RM (1990) A workstation interface for measuring interspike intervals. J Neurosci Methods 35:195–201.

  32. 32.

    Siegel RM, Andersen RA (1988) Perception of three-dimensional structure from two-dimensional motion in monkey and man. Nature 331:259–261.

  33. 33.

    Siegel RM, Birks RI (1988) A slow potassium conductance after action potential bursts in rabbit vagal C fibers. Am J Physiol 254:R443–R452.

  34. 34.

    Andersen RA, Essick GK, Siegel RM (1987) Neurons of area 7a activated by both visual stimuli and oculomotor behavior. Exp Br Res 67:316–322.

  35. 35.

    Andersen RA, Essick GK, Siegel RM (1985) Encoding of spatial location by posterior parietal neurons. Science 230:456–458.

Book chapters and reviews

  1. 1.

    Raffi M, Siegel RM (2004) Multiple cortical representations of optic flow processing. In: Vaina LM, Beardsley SA, Rushton S, Kluwer (eds) Optic flow and beyond. Academic Press–Synthese Library, Berlin

  2. 2.

    Siegel RM (1998) A review of Spikes: exploring the neural code by F. Rieke D. Warland R. de Ruyter, van Stevenick, W. Bialek. Bull Math Biol 60:409–415

  3. 3.

    Siegel RM (1999) Structure from visual information sources. In: The MIT encyclopedia of the cognitive sciences. Wilson RA, Keil FC (eds) MIT Press, Cambridge, pp 810–812

  4. 4.

    Siegel RM, Read HL (1997) Construction and representation of visual space in the inferior parietal lobule. In: Rockland KS, Kaas JH, Peters A (eds) Cerebral cortex, vol 12. Extrastriate cortex in primates. Plenum Press, NY, pp 499–525

  5. 5.

    Siegel RM, Read HL (1993) Temporal processing in the visual brain. In: von Euler C, Llinás RR, Galaburda AM, Tallal P (eds) Temporal information processing in the nervous system: special reference to dyslexia and dysphasia. Annals of the NY Academy of Sciences, vol 682, pp 171–178

  6. 6.

    Sacks OW, Siegel RM (1992) Migraine Aura and Hallucinatory Constants in Migraine. In: Sacks OW (ed) University of California Press, Berkeley, pp 273–298 (translated into Dutch, German, Italian, Japanese, French, Portuguese (Brazil), Greek and Spanish)

  7. 7.

    Sacks OW, Siegel RM (1990) Chaos and awakenings. In: Sacks OW (ed) Awakenings. Harper–Collins, NY, pp 351–365 (translated into Korean, Japanese, Italian, German, Dutch, French, Polish, Hungarian, Portuguese, Spanish)

  8. 8.

    Andersen RA, Siegel RM (1990) In: Edelman GM, Gall WE, Cowan WM (eds) Motion processing in the primate cortex in Signal and sense: local and global order in perceptual maps. Wiley-Liss, NY, pp 163–184

  9. 9.

    Siegel RM (1988) In: Anderson DZ (ed) Discovering structure from motion in monkey, man and machine in Neural Information Processing Systems. American Institute of Physics, New York