PROFILE

Profile of Peter H. Schiller

n a windowless laboratory on the sixth program in psychology at Clark University floor of the Brain and Cognitive Sci- in Worcester, Massachusetts. Under the Iences Institute of Massachusetts tutelage of psychologist Morton Weiner, Institute of Technology (MIT), neu- Schiller studied the phenomenon of sub- roscientist Peter Schiller lines up visual liminal perception, helping to debunk the stimuli on a computer screen. The stimuli then-rife myth of extrasensory perception are pairs of cues flashed side-by-side, such by demonstrating that subliminal cues as horizontal and vertical lines, upright could trigger neurobiological processes and inverted triangles, and the words “car” underlying certain behaviors, such as and “his.” As Schiller flashes the stimuli people making a bee line to buy soda in on his monitor, a volunteer observes them movie halls when the message “Drink through a stereoscope, which presents one Coca Cola” was briefly flashed between cue in a pair to one eye and the other cue movie frames (1). to the other eye. The volunteer identifies While at Clark University, Schiller the stimuli in order: a cross, the Star of spent his summers at the Austen Riggs David, and the word “chairs.” Then, the Center, an institution for psychotherapy, stereoscope displays groups of dots, some in Stockbridge, Massachusetts, where of which are shifted in position. To the he met George Klein, a professor of volunteer, the shifting dots appear deeper psychology at New York University. At than the rest. Through such experiments the center, Schiller and Klein conducted aimed at identifying people’s ability to experiments on the development of combine visual cues and perceive depth, visual interference in children. Working Schiller, who was elected to the National with more than 200 grade-school and Academy of Sciences in 2007, hopes to Peter H. Schiller uses random-dot stereograms (on college children, Schiller found that visual determine the brain regions involved in wall) to study depth perception. interference, which thwarts people’s binocular integration and depth percep- ability to identify a color when its name tion. The findings from those studies could institute then located in Florida. At the is printed in a different color, wanes help pinpoint the precise time frame Yerkes Laboratory, where he joined his with age (2). when corrective interventions can best father months later, the adolescent Schil- Back at Clark University, Schiller help stereoblind people perceive depth. ler helped his father carry out experi- studied the basis of optical illusions. Beyond uncovering the neurobiological ments in animal behavior. Those early “Illusions are far more complicated than basis of vision, Schiller’s goal is to help forays into brain science research sowed people think, largely because they could restore sight to the blind someday. the seeds of Schiller’s future scientific be generated in the retina or in various Born in Berlin shortly before World War accomplishments. brain regions,” Schiller says. To deter- II, Schiller moved to Budapest, Hungary in Two years later, following the death of mine where in the visual system illusions 1934, when his father, a research psychol- his father, Schiller went to Charleston, occur, Schiller had to present visual ogist, returned to his homeland after a South Carolina to live with his father’s stimuli to experimental subjects in two postdoctoral stint at the University of physician-friend James Anliker. With ways: to each eye separately and to both Berlin. A German-speaking transplant in Anliker’s help, Schiller got a job in the eyes at once. To accomplish this, Schiller Budapest, Schiller at first struggled to anatomy department at Charleston Medi- fashioned an optical tool called a five- memorize Hungarian poems in grammar cal School, where his chores ranged from field tachistoscope. The instrument school but soon mastered his mother feeding monkeys in the animal facility helped reveal that many illusions, such tongue, devouring Hungarian translations to cleaning up after medical students dis- as the Ebbinghaus illusion, in which of Jules Verne’s science-fiction books. secting cadavers. A meeting with Schiller’s identical circles appear different when Schiller’s boyhood years bear testimony to color-blind high-school English teacher surrounded by circles of different sizes, his budding scientific temperament. At piqued Schiller’s early interest in vision. occur in the brain’s visual cortex rather the age of 12, he found a ball lost during “When Mr. Gibbs told me he was pulled than in the retina. play by using an identical one to retrace the over by a cop for running a red light that Extending his findings on illusions, path to where the lost ball lay hidden. As he had presumed was green, I became Schiller trained his new tool on a phe- a teenager, he cobbled together a Morse intrigued—even more so when I learned nomenon called masking, which reduces code-based communication system to ex- that color blindness is more common the visibility of an object shown to people change surreptitious messages with his among males than females,” Schiller says. milliseconds before a second object, cousin, whom he was sometimes forbidden known as a “masking” object, is shown. to see. When he was not devising science- Eye on Vision Vision researchers knew that masking based ploys for play, Schiller spent starlit Schiller struggles to pinpoint the precise could arise from differences in brightness, nights in his uncle’s hilltop backyard with point when he embarked on his decades- pattern, and contrast related to the two a map of the sky, gazing at constellations. long career in vision research, but his objects, but where in the visual system Growing up in war-torn Hungary, undergraduate studies in psychology at masking originates was a mystery. Schil- Schiller witnessed the ravages wrought by Duke University are a good starting point. ler’s tachistoscope helped answer that the Russian invasion of Budapest. Facing As an undergraduate, Schiller studied the question (3). “We found that brightness bleak prospects for a scientific career in ability of fish to see colors, his first formal a harsh political climate, Schiller’s father attempt to study vision scientifically. fled the country in 1947 for the United After graduating from Duke University, This is a Profile of a recently elected member of the Na- States, where he worked as a researcher at Schiller spent a year in Germany on mil- tional Academy of Sciences to accompany the member’s the Yerkes Laboratory, a primate research itary duty before enrolling in a graduate Inaugural Article on page 17087 in issue 40 of volume 107.

www.pnas.org/cgi/doi/10.1073/pnas.1101955108 PNAS Early Edition | 1of3 Downloaded by guest on October 2, 2021 masking occurred only when both visual ments by virtue of high-frequency bursts responding to rises and drops in the stimuli were presented to the same eye, that rapidly contract the muscle; the amount of light. Objects absorb and re- suggesting that it occurred in the retina, duration of the burst defines the ampli- flect different wavelengths of light, alter- whereas pattern masking and metacon- tude of the saccade,” Schiller says. “That ing the number of photons of light enter- trast masking occurred even when dif- work led to a basic understanding of how ing eyes trained on them. The ON/OFF ferent stimuli were presented to the two the brain’s oculomotor complex drives the system, Schiller found, helps the eyes eyes, suggesting that it occurred in the eyes,” he adds. perceive changes in light intensity (8). brain,” Schiller says. Schiller parlayed Soon thereafter, another brain structure “We did experiments that selectively these wide-ranging studies into a PhD driving the eyes became the focus of blocked one channel and found that the ’ “ degree in psychology from Clark Univer- Schiller s interest. Dubbed the superior ON channel responds to light increment, ” sity in 1962. colliculus, this many-layered nub of whereas the OFF channel responds to brain tissue serves as a source of saccades ” MIT-Bound light decrement, Schiller says. Those in primates. Schiller found that macaques seemingly mundane findings underlie After a brief interlude of clinical work without a superior colliculus were slow to revelatory “Aha!” moments when applied with mentally ill patients at Worcester execute saccades, whereas macaques to real-world scenarios. Thanks to the State Hospital, Schiller began angling for with lesions in the frontal eye field had OFF channel, people can read print, postdoctoral research opportunities. trouble selecting targets in a visual scene. which usually contains dark characters Hans-Lukas Teuber, then recently ap- Removing both regions scotched all sac- on a light background; reading dark pointed chair of the psychology depart- cades (5). These findings helped lay the ment at MIT, invited Schiller to perform foundation for an overarching scheme for characters in succession signals light “ decrement to the retina. Thanks to the postdoctoral research on the mechanism the neural control of saccades (6): There fi of visual masking in the brain. There, are two brain systems involved in gener- ON channel, a sh in the ocean can spot Schiller mastered a method for recording ating saccades. One helps select targets its predator in murky waters through the ’ electrical activity from individual brain in the visual scene to which the eyes light bouncing off the predator s body; fl cells in cats and monkeys by using varnish- must be directed, and the other gener- the re ection signals light increment to “ coated tungsten microelectrodes that ates saccades to sudden visual cues,” the retina. The ON/OFF system is helped shed light on the mechanism of Schiller says. crucial for survival for virtually every brightness masking. Later, in partnership species, except maybe for largely noctur- with MIT psychologist Steven Chorover, Midgets, Parasols, and Toggle Switches nal animals,” Schiller says. Schiller studied short-term amnesia, a Schiller next unraveled how the eyes These days, Schiller’s mind is pre- condition triggered by traumatic experi- communicate with the brain. Central to occupied with how people perceive depth. ences. Their finding that electrical shock this communication are retinal ganglion Thanks to their ability to reconstitute triggered a short bout of amnesia in rats cells, which carpet the inner surface of the 3D visual scenes from the 2D images helped other researchers study how brain retina and transmit visual information falling on the retina, most people can cells consolidate memories (4). Schiller’s from photoreceptors to the brain. Schil- perform with ease a range of tasks that diverse research pursuits led to an assis- ler’s quest to study retinal ganglion cells rely on depth perception, from threading tant professorship at MIT in 1964. led him and his postdoctoral fellow, needles to driving cars. However, at least Schiller has since delved deeper into the Joseph Malpeli, to a brain region called 5% of the population in the United States dark recesses of the human visual system, the lateral geniculate nucleus, which re- is stereoblind, unable to estimate depth illuminating its workings along the way. ceives visual input from the retina. First, with reasonable accuracy. Schiller has Notable among his contributions are Schiller and Malpeli found that two kinds sought to pinpoint brain regions where studies on how the brain controls rapid eye of retinal ganglion cells—midget and depth cues are processed. Researchers — movements, or saccades. Coined in the parasol send connections to different have long known that depth perception “ ” 1800s, the term saccade refers to a layers of the lateral geniculate nucleus. partly depends on phenomena called quick shift in gaze, guided by visual cues Then, by blocking either the midget or stereopsis and motion parallax. Stereopsis and controlled by the nervous system. parasol cells with lesions in the corre- refers to a natural disparity that occurs People make nearly 3 saccades every sponding layers of the lateral geniculate when observing an object in a scene; second, or 170,000 saccades a day; each nucleus, they found that the midget cells fi converging neuronal signals from each shift in gaze commands a concomitant process color and ne patterns, whereas eye arise from slightly different locations movement of the eyes toward a target the parasol cells process motion and in the scene, causing the brain to compute amid a welter of visual cues. “Animals depth perception (7). a depth cue from the disparity. Motion move around, so to analyze the visual Schiller continued to probe the retina parallax stems from differences in the scene, they must fix the eyes periodically in still finer detail, revealing surprising with reference to the environment,” insights on the evolutionary origin of velocities of moving objects in a scene; Schiller says. For example, when people a system of toggle switches in the eyes. the difference provides a depth cue. recognize a face in a crowd, they use In the early 1960s, neuroscientist Haldan Schiller found that blocking the midget saccades to fix vision, directing the visual Keffler Hartline discovered that the cells of the retina affects stereopsis, information to the fovea, a region of the retina houses cells that constitute an whereas blocking the parasol cells “ retina that helps people see detail. To ON/OFF toggle switch: cells that fire affects motion parallax (9). We are fix vision, the brain must decide how to when light comes on, cells that fire when now combining behavioral studies and direct the eye muscles with each saccade. light is turned off, and cells that fire in functional magnetic resonance imaging Because the fibers of each eye muscle both situations. The discovery, which to determine how the brains of stereo- course uninterrupted through the length earned Hartline a Nobel prize, left in its blind individuals are different from those of the muscle, Schiller could use his wake the mystery of the evolutionary or- of people with normal depth perception,” recording technique to trace the firing igin of the toggle switch. Contrary to Schiller says. Those efforts, he says, of single neurons as the electrical signal then-popular theories about why the could lead to corrective measures that rippled from the brain into the muscle. ON/OFF system evolved, Schiller proved would restore depth perception to “These cells produce saccadic eye move- that the system plays a role in rapidly stereoblind people.

2of3 | www.pnas.org/cgi/doi/10.1073/pnas.1101955108 Nair Downloaded by guest on October 2, 2021 Vision for the Future The electrodes would stimulate the area each eye to the brain. “Vision is a much Schiller’s forays into vision research have and yield information about shape, more complicated problem, which is fur- no doubt unearthed a wealth of basic in- motion, and depth. An algorithm would ther compounded by the need for depth sights into how people see, but his long- integrate the camera and the electrodes perception,” Schiller says. To prove useful, cherished goal is to restore sight to the (10). To test this idea, Schiller conducts electrode arrays implanted in the brain blind, possibly via an implantable visual noninvasive experiments on people with must last years, if not decades, placing prosthetic device. Some researchers have normal vision by mimicking electrical limits on the kinds of electrodes that can be stimulation with a camera that converts successfully constructed retinal implants used. That is partly why an implantable visual images into displays on a computer for people with retinitis pigmentosa, prosthetic based on electrical stimulation of age-related macular degeneration, and screen. Those findings, Schiller says, the brain is hardly around the corner. other defects of the retina. Other ap- could help reveal the feasibility of de- Whether or not such a visual prosthetic proaches, based on gene therapy, stem veloping a device based on actual elec- becomes a reality before the end of cells, and artificial retinas, are in various trical stimulation, inching closer to an Schiller’s scientific career, his contribu- stages of development. However, so far, implantable prosthetic. tions to vision research have already a device that would restore sight by direct However, that path is riddled with road- earned him recognition among his peers. electrical stimulation of the visual cortex blocks. Unlike cochlear implants, whose True to his scientific temperament, remains a distant dream. Schiller and his runaway success has restored hearing to Schiller says pursuing his research goals collaborators hope to lay the groundwork thousands of deaf people, visual prosthe- has proved to be almost as satisfying as for such a device by performing a feat tic devices face a formidable challenge. achieving them—an outlook that might of technological wizardry: developing Whereas the neuronal projections from the keep him busy at the laboratory bench for a camera that captures and transmits cochlea to the central nervous system many years. visual images to an array of electrodes number in the tens of thousands, more than implanted in area V1 of the visual cortex. a million nerve fibers wend their way from Prashant Nair, Science Writer

1. Wiener M, Schiller PH (1960) Subliminal perception or 5. Schiller PH, True SD, Conway JL (1979) Effects of 8. Schiller PH (2010) Parallel information processing perception of partial cues. J Abnorm Soc Psychol 61: frontal eye field and superior colliculus ablations on channels created in the retina. Proc Natl Acad Sci USA 124–137. eye movements. Science 206:590–592. 107:17087–17094. 2. Schiller PH (1966) A developmental study of color- 6. Schiller PH (1998) The neural control of visually 9. Schiller PH, Logothetis NK, Charles ER (1990) Role of word interference. J Exp Psychol 72:1–5. guided eye movements. Cognitive Neuroscience of the color-opponent and broad-band channels in vi- 3. Schiller PH (1969) Behavioral and electrophysiological Attention: A Developmental Perspective,edRichardsJ sion. Vis Neurosci 5:321–346. studies of visual masking. Symposium on Information (Lawrence Erlbaum Associates, Mahwah, NJ), pp 3– 10. Schiller PH, Tehovnik EJ (2008) Visual prosthesis. Per- Processing in the Nervous System, ed Leibovitz KN 50. ception 37:1529–1559. (Springer, New York), pp 141–165. 7. Schiller PH, Logothetis NK, Charles ER (1990) Func- 4. Chorover SL, Schiller PH (1965) Retrograde amnesia. tions of the color-opponent and broadband chan- Science 149:1521. nels of the visual system. Nature 343:68–70.

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