PUBLICATIONS

Sergei Gepshtein, Ph.D.

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1. with Midya R, Pawar AS, Pattnaik D, Mooshagian E, Borisov P, Albright TD, Snyder LH, Williams RS, Yang JJ, Balanov AG, Savel'ev S (under revision). Artificial transneurons emulate neuronal activity in different areas of brain cortex. [+]

   Rapid development of memristive elements emulating biological neurons creates new opportunities for brain-like computation at low energy consumption. A first step toward mimicking complex neural computations is the analysis of single neurons and their characteristics. Here we measure and model spiking activity in artificial neurons built using diffusive memristors. We compare activity of these artificial neurons with the spiking activity of biological neurons in sensory, pre-motor, and motor cortical areas of the monkey brain. We find that artificial neurons can operate in diverse self-sustained and noise-induced spiking regimes that correspond to the activity of different types of cortical neurons with distinct functions. We demonstrate that artificial neurons can function as trans-functional devices (transneurons) that reconfigure their behaviour to attain instantaneous computational needs, each capable of replacing several biological neurons.
   
   Corresponding authors: Yang, Gepshtein, Balanov, Savel’ev.
   
   

2. with Snider J (under revision). Multistep rationality and visual computation. [+]

   Every day we make countless decisions: from reaching for a glass of water to planning your next week. Consequences of such decisions consist of multiple steps, each of which leads to further prospects that add up to a sweeping network of interlinked possibilities. To study how humans select actions in view of this prospective complexity, we asked participants to choose sequences of tokens on a diverging triangular lattice. The lattice moved continuously, revealing new tokens and allowing participants to reconsider previous plans. Participants’ overt choices by provided information about their covert choice strategies. We studied how far into the future participants planned actions, how often they reconsidered previous choices, and what heuristics they used in this process.
   
   We compared participants’ performance in two conditions. In one, rewards were represented by token size so the task could be solved by specialized visual mechanisms. In the other, rewards were represented numerically so the task required a cognitive effort. In the former case of specialized computation, performance was efficient and free of heuristics. But when the task required cognitive effort, participants turned to simplifying heuristics. Thus a single procedure entailed two patterns of decision-making: irrational behavior, previously reported in cognitive tasks, and optimal behavior, previously reported in sensorimotor tasks.

3. with Proietti T (under review). Perception of architectural proportion in three dimensions. [+]

   Architectural proportion has been primarily studied in two dimensions. Similarly, scientific studies of the perception of proportion have been limited to two-dimensional shapes projected on flat surfaces and viewed from fixed distances. Still, the perception of architectural proportion occurs in the three-dimensional space. Here we addressed this discrepancy by means of sensory psychophysics. We asked participants to compare proportions of solid objects presented inside a variant of camera obscura. We systematically varied the angles of these objects and their distances from the observer. Participants’ ability to judge proportions correctly strongly depended on the angle of observation. Also, perception was biased such that objects rotated away from the person appeared to have a larger proportion. These results allow one to begin analyzing the structure of architectonic space in terms of how perception of architectural proportion depends on the observer’s location in the environment. This method of analysis of perception is readily generalizable to studies of objects at larger scales and studies of perception by the moving observer.

4. with Jurica P, Albright TD, Ladziak D, Preis A (under review). Improving eyewitness performance by machine learning of face similarity. [+]

   Eyewitness identification has long played a valued role in criminal investigation and prosecution. But eyewitnesses sometimes fail, with tragic personal and societal consequences. At the same time, scientific study of human perception and memory reveals natural limits on the veracity of eyewitness reports in the conditions of lineup testing. An eyewitness lineup is composed of one suspect and a set of fillers: innocent participants selected to challenge recognition memory. The choice of fillers markedly affects the probability that an eyewitness correctly identifies the perpetrator. Lineups composed of fillers of roughly the same similarity to the witness’ description of the perpetrator are termed “fair.” Conversely, lineups composed of fillers that possess differing degrees of similarity to the perpetrator are termed “unfair” or “biased.” Here we propose a solution to the problem of selecting fair lineups by modeling human judgments of face similarity. We collect face similarity judgments from human observers based on a small set of faces. Results of these measurements are then used to train a Model Witness that generates similarity predictions, validated by iteration with additional human subjects and faces, until we reach a point where behavior of the Model Witness is sufficiently similar to that of a population of human observers. This approach allows one to rapidly evaluate perceptual similarity for all pairs of faces in a large face library, thus providing a quantitative basis for lineup filler selection.

5. with Malpas J (under review). Horizons and thresholds: boundary and representation in architecture and science. [+]

   Starting with a simple example, we develop conceptual distinctions that relate to boundaries in human experience and forms of representation. We show the importance of the notion of boundary whether it is manifested as geometrical limit, sensory threshold, or phenomenal horizon. We delineate some important features of the way boundaries work in architecture and science: in the analysis of perception and, more generally, in the analysis of experience. This inquiry prompts a reevaluation, first, of how we should study the perception of the built environment and, second, of the relationship between architecture and science, including the possibility of genuine dialogue between them.

6. with Zharikova A & van Leeuwen C (under revision). Phenomenal identity of visual objects from the perspective of early vision. [+]

   Perceptual grouping allows items separate in space or time to be seen as parts of the same object. Perceptual grouping is typically associated with mid-level vision. We propose that perceptual grouping shares important characteristics with early vision, in particular with spatiotemporal contrast sensitivity. We show that in bistable moving stimuli, individual preferences for seeing moving objects follow predictions from individual contrast sensitivity.
   
   In two experiments, we used displays made of spatially discrete elements (dots), which were systematically displaced across subsequent frames. The displays give rise to the perception of different moving configurations depending on the spatiotemporal distances between the dots. We found the points of perceptual equilibrium, at which alternative configurations were equally likely, as a function of the spatiotemporal distances between the dots. The equilibrium points were consistent with points of equal contrast sensitivity, measured using drifting luminance gratings. These results suggest that models of motion perception developed to account for large-scale characteristics of early visual processes could be generalized to also account for mid-level visual processes, thus supplanting previously descriptive concepts of mid-level vision, such as the principle of proximity, by mechanistic and computational concepts, such as economy of resources and efficiency of encoding.

7. with Savel'ev S (forthcoming). Visual computation by neural wave interference. [+]

   To gain insight into the neural events responsible for visual perception of static and dynamic optical patterns, we study how neural activation spreads in arrays of inhibition-stabilized neural networks with nearest-neighbor coupling. The activation generated by local stimuli in such networks propagates between locations, forming spatiotemporal waves that affect the dynamics of activation generated by stimuli separated spatially and temporally, and by stimuli with complex spatiotemporal structure. These interactions form characteristic interference patterns that make the network intrinsically selective for certain stimuli, such as modulations of luminance at specific spatial and temporal frequencies and specific velocities of visual motion. Due to the inherent nonlinearity of the network, its intrinsic tuning depends on stimulus intensity and contrast. The interference patterns have multiple features of "lateral" interactions between stimuli, well known in physiological and behavioral studies of visual systems. These diverse phenomena, here arising from a single mechanism, have been previously attributed to distinct mechanisms responsible for frequency tuning on neural circuits, their direction selectivity and contrast normalization, and center-surround interactions.

8. with Maloney LT & Singh M (forthcoming). Oxford Handbook of Computational Perceptual Organization. [+]

   Until very recently, research on perceptual organization has been primarily descriptive. The result was a taxonomy of phenomena with little attempt to identify underlying mechanisms or develop predictive models. The situation has changed in recent years. New experimental methods have been introduced to measure the organizational processes in vision and other sensory modalities, and new predictive computational theories have been developed.
   
   This Handbook is an organized survey of the many new approaches to the study of perceptual (mainly visual) organization with an emphasis on computational and mathematical approaches. With chapters written by leading authorities, the Handbook describes modern experimental and computational methods that not only contribute to deciphering the mechanisms of the classical phenomena of perceptual organization but also open new perspectives in what is sometimes called the neo-Gestalt approach to perception. The intended audience includes researchers in psychology, neural science, computer science, and philosophy as well as graduate and advanced undergraduate students in these fields.

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9. Proietti T & Gepshtein S (to appear on October 16, 2024). Proportioned, intelligible, and smart architecture. In Routledge Companion to Smart Design Thinking in Architecture & Urbanism for a Sustainable Living Planet. Kanaani M (Ed.) Routledge. ISBN: 9781032469904 [publisher link] [+]

   The humanistic tradition in architectural design places human flourishing above the artistic expression of the designer. This tradition draws inspiration from visions of harmony and balance that are akin to proportions of the human body: a product of nature and a traditional symbol of perfection. With such ideas in mind, humanistic architects of the fifteenth and sixteenth centuries sought to create a connection between the person and the universe. This tradition had continued to influence architects over the centuries: from the Renaissance of Cesariano, di Giorgio, and da Vinci to the Modernism of Le Corbusier, Neufert, and Blomstedt.
   
   In recent decades, the increasing emphasis on technology and science in architectural design has been often perceived as a challenge to the humanistic tradition. One reason is that the sciences pertinent to understanding human experience (such as neuroscience and cognitive science) provide descriptions of experience that often are fragmented and abstract. Concerned with parts of the human body and segments of behavior, the scientific stance is feared to divert the architect from unity of experience. There is also the worry that integrating scientific principles into architectural design may overshadow the humanistic ideals of harmony and beauty and thus hinder artistic creativity of the designer.
   
   Careful review of these concerns suggests that the suspicion of the scientific attitude in architectural design has been fueled by early and premature applications of this attitude. There is the hope that the rapidly evolving interface of science and architecture will facilitate designs that are "smart" in the sense of being adaptable to human needs. This new-found adaptability of design can be achieved differently at different stages of design: using tools informed by empirical study of human perception and behavior during conception of design, and by means of flexible real-time interaction between individuals and their environment during use. In both cases, the advancement of smart design requires systematic empirical investigation of how individuals interact with and respond to the environment, using a full spectrum of pertinent scientific methods that include physiological, behavioral, and computational.
   
   To illustrate this approach, we turn our attention to the hatching transformation of a traditional theme of research in humanistic architecture: the theme of architectural proportion and its role in design and experience of the built environment.
   
   

10. Gepshtein S (2022). Perceptual space as a well of possibilities. In Affordances in Everyday Life: A Multidisciplinary Collection of Essays. Djebbara Z (Ed.) Springer/Nature. doi 10.1007/978-3-031-08629-8 [publisher link] [+]

    Everyone seems to know what space is. But the meaning of “space” varies from person to person and from one occasion to another. It varies among the academic disciplines concerned with spatiality, such as physics, psychology and phenomenology, and among practical professions, such as architecture and filmmaking, stage design and creative writing. How can we reconcile this polyphony? Is there an underlying root concept of space? In other words, do these multiple and disparate concepts have a “focal meaning”? One manner of answering these questions is offered here, by considering a moving person who is sequentially exposed to specific possibilities of experience at different spatial locations. Reminiscent of the concept of affordance, the present account is concerned with possibilities of experience, rather than with actual experience, and it is trained on distributed patterns of perception and behavior, rather than on their piecewise characterization.
    
    

11. Gepshtein S, Pawar AS, Kwon S, Savel'ev S & Albright TD (2022). Spatially distributed computation in cortical circuits. Science Advances 8 (16), 1-19. doi: 10.1126/sciadv.abl5865 [journal link] [+]

    The traditional view of neural computation in the cerebral cortex holds that sensory neurons are specialized, i.e., selective for certain dimensions of sensory stimuli. This view was challenged by evidence of contextual interactions between stimulus dimensions in which a neuron’s response to one dimension strongly depends on other dimensions. Here we use methods of mathematical modeling, psychophysics, and electrophysiology to address shortcomings of the traditional view. Using a model of a generic cortical circuit, we begin with the simple demonstration that cortical responses are always distributed among neurons, forming characteristic waveforms which we call "neural waves." When stimulated by patterned stimuli, circuit responses arise by interference of neural waves. Results of this process depend on interaction between stimulus dimensions. Comparison of modeled responses with responses of biological vision makes it clear that the framework of neural wave interference provides a useful alternative to the standard concept of neural computation.
    
    Tagline: Investigating interference of neural waves helps to overcome limitations of the traditional view of cortical computation.
    
    

12. Proietti T & Gepshtein S (2022). Locating architectural atmosphere. In Generators of Architectural Atmosphere. Canepa E & Condia B (Eds.) New Prairie Press. ISBN: 978-0-9915482-6-2 [publisher link] [+]

    Architectural atmospheres are often described in spatial terms, but the nature of their spatial organization remains elusive. Here we consider how spatial characteristics of architectural atmosphere can be investigated from a new perspective emerging in the interface between the disciplines of architectural design and empirical science. We observe that qualities of architectural atmospheres must vary across location and are necessarily divided to spatial regions because different sensory information is available in different regions of the environment. We investigate how the boundaries of these regions and their sensory content can be identified using principles of geometrical optics, physiological optics, perceptual organization, and orienting behavior.
    
    

13. Nikolaev AR, Esposito A, Chiarella AG, Raffone A, Gepshtein S, & van Leeuwen C (2022). Orientation bias in ambiguous dot lattices: contextual influences and electrophysiological correlates. Fechner Day 2022 – Proceedings of the 38th Annual Meeting of the International Society for Psychophysics, Lund, Sweden, 75-81. [journal link] [+]

    Perceptual bias reveals itself when generic representations of the world override effects of immediate stimulation. Perceptual bias may be elicited by prior contextual factors, such as visual working memory, and its signature brain activity could be detected by EEG. A perceptual bias for the vertical orientation from time to time overrides perceptual grouping by proximity in ambiguous dot lattices. We present an overview of our research on factors eliciting this orientation bias. We demonstrate how biased perception correlates with spontaneous EEG activity. We then show how temporal context elicits perceptual bias through top-down and bottom-up influences. We conclude that intrinsic preferences and the way they are elicited by the visual environment jointly shape our perception of the world. The ability to shift between the biased and unbiased modes provides flexibility to the visual system.
    
    

14. Proietti T & Gepshtein S (2021). Architectural proportion from an empirical standpoint. Journal of Interior Design, 47 (1), 11-29. doi: 10.1111/joid.12210 [journal link] [+]

    Proportion has long been central to theories of design and architecture before its role was questioned in the mid-twentieth century. In spite of this scrutiny, no definitive conclusion has been reached on the question of how proportion affects experience of the built environment. Here, an architect and a scientist attack this question from an empirical standpoint. They argue that, as a starting point, it is important to understand under which conditions proportions are perceptible by the flesh-and-blood person who moves freely through the built environment and observes it under various distances and angles. The authors begin by surveying the work of two forerunners of empirical study of proportion: The Russian architect and educator Nikolai Ladovsky, whose “psychotechnical” approach was inspired by scientific psychology, and the Dutch architect Hans van der Laan, who developed the theory of plastic number concerned with proportions of three-dimensional objects, and whose approach was strikingly similar to scientific approaches. Following an analysis of informal studies by Ladovsky and Van der Laan, the authors examine implications of such studies for education in architecture and interior design, and then describe two approaches to investigating architectural proportion formally, by methods of sensory psychophysics.
    
    

15. Gepshtein S & Albright TD (2021). Thinking outside the lineup box: Eyewitness identification by perceptual scaling. Journal of Applied Research in Memory and Cognition, 10 (2), 221-224. doi: 10.1016/j.jarmac.2021.05.001 [journal link] [+]

    Eyewitness identification of a criminal suspect commonly takes the form of a police lineup, which is a behavioral task intended to tap into the witness’ memory for the crime. Eyewitnesses engaged in this task sometimes identify innocent people. In the following we consider how solving this problem of misidentification may benefit from modern scientific understanding of the processes of visual sensation, perception, and memory. We argue that viewing the problem from the perspective of these sciences reveals a number of weaknesses associated with the traditional lineup approach and suggests specific strategies for improvement.
    
    

16. Proietti T & Gepshtein S (2021). Psychophysics of architectural proportion in three dimensions. Proceedings of Nexus 2021: Relationships between Architecture and Mathematics – International Conference in Kaiserslautern, Germany, July 26-29, 2021, pp. 1-8 [journal link] [+]

    The theory of proportion in architecture has a long and convoluted history, in which the definition of proportion emerged as elusive and controversial. One source of difficulty is the multiple notions of the role proportion plays in experiencing architecture, in mathematical, perceptual and aesthetic discourses. As Scruton (1979) put it, “Precisely because proportion is so aesthetically fundamental that we should beware of tying it down to an explicit definition.” In effect, architectural proportion has become one of the “words with lost meaning” (Scholfield 1958). Attempts to clarify the role and significance of proportion have been made from three perspectives: symbolic (e.g., March 1998), aesthetic (e.g., Wittkower 1949), and perceptual-cognitive (e.g., Padovan 1991). The last two perspectives have often been conflated. These are only some illustrations of the controversial nature of architectural proportion.
    
    We confront this ambiguity by pursuing an interdisciplinary program of research that has three points of focus. First, conceptions of proportion useful for architectural design should be defined for three-dimensional objects, rather than two-dimensional projections of objects. Second, differences between mathematically distinct proportions should be considered only after we have ascertained that the proportions in question are perceptually discriminable from one another. Third, perception of proportion should be studied from the point of view of a mobile person, which is the generic situation of experiencing architecture, in contrast to the artifice of static observer presumed by adherents of perspectival representation in architecture. Here we present first steps in pursuing these questions, concentrating on discrimination of proportions of three-dimensional objects.
    
    

17. Mallgrave HF & Gepshtein S (2021). The interface of two cultures. Intertwining, 3, 46-73 [journal link] [+]

    An architectural historian and a neuroscientist engage in a wide-ranging dialogue about the problem of two cultures at the interface of architecture and natural sciences of the human being. The conversation revolves around the question of how such disciplines as systems neuroscience, cognitive science, and sensory psychophysics can breathe new life into creative endeavors of students and practitioners of design. The authors explore how designers could become more fully aware of biological complexity of the human being and how design education could be reformed for that purpose.

18. Gepshtein S (2020). Species of space. Architectural Design, 90 (6), 36-41. doi: 10.1002/ad.2629 [journal link] [+]

    Multiple concepts of space have originated in different arts and sciences, related to one another but also distinct because they are viewed through radically different lenses. In physics and physiology, space is an aspect of the objective reality, couched in terms of metrics and distances. In psychology and phenomenology, space is conceived from the first-person perspective, structured by one’s plans, intentions and affordances. Different yet are the concepts of space entertained by artists and designers: in painting and photography, cinema and architecture, literary criticism and philosophy of art. Here space is “constructed” to support praxis: representing a solid object on a surface, facilitating navigation or analyzing a narrative. In the emerging arena of Neuroscience for Architecture it is important to appreciate differences between these concepts of space, learn about them in their context and then understand how they mix in practice. The author shows how the space of experience is articulated by boundaries that arise from the human body. Although intangible and fluid, these boundaries are nevertheless real and systematic, which is why they readily yield to the methods of science.
    
    Tagline: Architects spend their time creating walls, facades, doors and roofs – containers of space. But are they missing a key ingredient?
    
    

19. Albright TD, Gepshtein S & Macagno E (2020). Visual neuroscience for architecture: seeking a new evidence-based approach to design. Architectural Design, 90 (6), 110-117 [journal link] [+]

    Visual neuroscience is a critical portal for understanding how humans capture and analyse information about the built environment. Reviewed here are several complementary experimental approaches from visual neuroscience that can support evidence-based architectural and urban design. The data generated by these approaches enable predictions about human responses to the built environment, and research methods are useful for studying these human responses. The research agenda for engaging these approaches in the context of design should be defined not by scientists but by designers, whose contributions will be facilitated by understanding of the strengths and limitations of such methods in formulating research goals and interpreting discoveries. Albright, Gepshtein, and Macagno review several complementary experimental approaches developed in different branches of visual neuroscience, helping to understand how humans capture and analyse information about the built environment. The authors propose how these approaches can be used in support of evidence‐based architectural and urban design.
    
    

20. Gepshtein S, Wang Y, He F, Diep D & Albright TD (2020). A perceptual scaling approach to eyewitness identification. Nature Communications, 11, Article 3380 [pdf] [+]

    Eyewitness misidentification accounts for 70% of verified erroneous convictions. To address this alarming phenomenon, research has focused on factors that influence likelihood of correct identification, such as the manner in which a lineup is conducted. Traditional lineups rely on overt eyewitness responses that confound two covert factors: strength of recognition memory and the criterion for deciding what memory strength is sufficient for identification.
    
    Here we describe a lineup that permits estimation of memory strength independent of decision criterion. Our procedure employs powerful techniques developed in studies of perception and memory: perceptual scaling and signal detection analysis. Using these tools, we scale memory strengths elicited by lineup faces, and quantify performance of a binary classifier tasked with distinguishing perpetrator from innocent suspect. This approach reveals structure of memory inaccessible using traditional lineups and renders accurate identifications uninfluenced by decision bias. The approach furthermore yields a quantitative index of individual eyewitness performance.
    
    

21. Gepshtein S & Berger T (2020). Dynamics of architectural experience in the perceptual field. In: AMPS Proceedings Series 18.1. Experiential Design – Rethinking relations between people, objects and environments. pp. 83-94. ISSN 2398-9467 [publisher link] [+]

    How is the built environment experienced by human beings in real time? Here an architect and a scientist join forces to answer this question from a new perspective that emerges in the rapidly evolving collaboration between architecture and the “human sciences” that include neuroscience, cognitive science, psychophysics, and experimental phenomenology. We focus in particular on the organization of spatial experience in and around buildings. Our starting point is the basic notion that adjacent locations offer the person different experiences and sensorimotor affordances, thus creating a continuous perceptual field. Scientific methods help to reveal the detailed structure of experience for different senses. For example, we study how the person traversing space acquires sensory access to some features of the environment and loses access to other features. These concepts can help the architect to develop methods for analysis and design of the experience of built environment.

22. Gepshtein S & Snider J (2019). Neuroscience for architecture: The evolving science of perceptual meaning. Proceedings of the National Academy of Sciences, USA, 116 (29), 14404-14406, doi/10.1073/pnas.1908868116 [journal link] [+]

    "Besides its traditional reliance on the tacit knowledge of timeless practices of construction, architecture relies largely on theories and findings of other areas of research and knowledge, instead of possessing an independent theoretical foundation of its own. During the past decades, architecture has been viewed from various theoretical perspectives, provided by, for instance, psychology, psychoanalysis, structural linguistics and anthropology as well as deconstructionist and phenomenological philosophies, just to name a few." -Juhani Pallasmaa
    
    Today this sweeping array of theories and perspectives is being expanded again by the disciplines allied under the loosely defined umbrella of neuroscience. Several families of concepts, paradigms, and methods from the neurosciences appear to be perfectly suitable for investigating what the architect would call the "human response to the built environment." These overlapping families include systems neuroscience and affective neuroscience, sensorimotor psychophysics and experimental phenomenology, to mention only some of the contenders. It is far from clear, however, which ideas will stick and what shape they will take in the new context. Just as it has happened to many prior imports to architecture, hard-won scientific knowledge may remain a foreign entity within the living body of architecture, supplying occasional metaphor and inspiring freewheeling speculation. Or the sciences may retain their natal rigor and invigorate architectural theory and practice by helping architects to test some old ideas and possibly rid their discipline of unbuttoned preconceptions, some of which had already been subjected to incisive analytical scrutiny...

23. Pawar AS, Gepshtein S, Savel'ev S & Albright TD (2019). Mechanisms of spatiotemporal selectivity in cortical area MT. Neuron, 101 (3), 514-527 [journal link] [Science Direct link] [+]

    Cortical sensory neurons are characterized by selectivity to stimulation. This selectivity was originally viewed as a part of the fundamental "receptive field" characteristic of neurons. This view was later challenged by evidence that receptive fields are modulated by stimuli outside of the classical receptive field.
         Here we show that even this modified view of selectivity needs revision. We measured spatial frequency selectivity of neurons in cortical area MT of alert monkeys and found that their selectivity strongly depends on luminance contrast, shifting to higher spatial frequencies as contrast increases. The changes of preferred spatial frequency are large at low temporal frequency and they decrease monotonically as temporal frequency increases. That is, even interactions among basic stimulus dimensions of luminance contrast, spatial frequency and temporal frequency strongly influence neuronal selectivity.
         This dynamic nature of neuronal selectivity is inconsistent with the notion of stimulus preference as a stable characteristic of cortical neurons.

24. Gepshtein S (2019). On some paradoxes of current perceptual theories. In Bianchi I & Davies R (Eds.) Paolo Bozzi's Experimental Phenomenology, pp. 56-63. pdf [+]

    Let us recall that the philosophical discipline of phenomenology and the scientific discipline of experimental phenomenology have a common origin. This origin is the descriptive psychology introduced by Franz Brentano and promulgated by the "Brentano circle" to the threshold of a new approach in the philosophy of mind and a new approach in empirical psychology. The aspiration of descriptive psychology was to develop a "science of mental phenomena." This aspiration became figurative in philosophical phenomenology and literal in experimental phenomenology, but the common origin left its mark on both disciplines. From the outset, their common goal was to investigate the human mind from an adamantly first-person perspective.
    
    Let us also recall that the scientific study of the mind was the goal of another discipline that made no commitment to the first-person perspective. This discipline is sensory psychophysics, conceived just before Brentano's descriptive psychology and dedicated to investigating mental phenomena from the third-person perspective of natural science...

25. Gepshtein S, Pawar AS, Savel'ev S & Albright TD (2018). Neural wave interference and intrinsic tuning in distributed excitatory-inhibitory networks. arXiv, arXiv:1810.08725 [link] [+]

    We developed a model of cortical computation that implements key features of cortical circuitry and is capable of describing propagation of neural signals between cortical locations in response to spatially distributed stimuli. The model is based on the canonical neural circuit that consists of excitatory and inhibitory cells interacting through reciprocal connections, with recurrent feedback. The canonical circuit is used as a node in a distributed network with nearest neighbor coupling between the nodes. We find that this system is characterized by intrinsic preference for spatial frequency. The value of preferred frequency depends on the relative weights of excitatory and inhibitory connections between cells. This balance of excitation and inhibition changes as stimulus contrast increases, which is why intrinsic spatial frequency is predicted to change with contrast in a manner determined by stimulus temporal frequency. The dynamics of network preference is consistent with properties of the cortical area MT in alert macaque monkeys.

26. Gepshtein S & Albright TD (2017). Adaptive optimization of visual sensitivity. Journal of the Indian Institute of Science, 97 (4), 423-434. pdf [+]

    Sensory systems adapt to environmental change. It has been argued that adaptation should have the effect of optimizing sensitivity to the new environment. Here we consider a framework in which this premise is made concrete using an economic normative theory of visual motion perception. In this framework, visual systems adapt to the environment by reallocating their limited neural resources. The allocation is optimal when uncertainties about different aspects of stimulation are balanced. This theory makes predictions about visual sensitivity as a function of environmental statistics. Adaptive optimization of the visual system should be manifested as a change in sensitivity for an observer and for the underlying motion-sensitive neurons. We review evidence supporting these predictions and examine effects of adaptation on the neuronal representation of visual motion.

27. Zharikova A, Gepshtein S & van Leeuwen C (2017). Paradoxical perception of object identity in visual motion. Vision Research, 136, 1-14. [link] [+]

    In the course of perceptual organization, incomplete optical stimulation can evoke the experience of complete objects with distinct perceptual identities. According to a well-known principle of perceptual organization, stimulus parts separated by shorter spatial distances are more likely to appear as parts of the same perceptual identity. Whereas this principle of proximity has been confirmed in many studies of perceptual grouping in static displays, we show that it does not generalize to perception of object identity in dynamic displays, where the parts are separated by spatial and temporal distances. We use ambiguous displays which contain multiple moving parts and which can be perceived two ways: as two large objects that gradually change their size or as multiple smaller objects that rotate independent of one another. Grouping over long and short distances corresponds to the perception of the respectively large and small objects. We find that grouping over long distances is often preferred to grouping over short distances, against predictions of the proximity principle. Even though these effects are observed at high luminance contrast, we show that they are consistent with results obtained at the threshold of luminance contrast, in agreement with predictions of a theory of efficient motion measurement. This is evidence that the perception of object identity can be explained by a principle of neural economy rather than by the empirical principle of proximity.

28. Nikolaev A, Gepshtein S & van Leeuwen C (2016). Intermittent regime of brain activity at the early, bias-guided stage of perceptual learning. Journal of Vision, 16(14), 11. pdf [+]

    Perceptual learning improves visual performance. Among the plausible mechanisms of learning, reduction of perceptual bias has been studied the least. Perceptual bias may compensate for lack of stimulus information, but excessive reliance on bias diminishes visual discriminability. We investigated the time course of bias in a perceptual grouping task and studied the associated cortical dynamics in spontaneous and evoked EEG. Participants reported the perceived orientation of dot groupings in ambiguous dot lattices. Performance improved over a 1-hr period as indicated by the proportion of trials in which participants preferred dot groupings favored by dot proximity. The proximity-based responses were compromised by perceptual bias: Vertical groupings were sometimes preferred to horizontal ones, independent of dot proximity. In the evoked EEG activity, greater amplitude of the N1 component for horizontal than vertical responses indicated that the bias was most prominent in conditions of reduced visual discriminability. The prominence of bias decreased in the course of the experiment. Although the bias was still prominent, prestimulus activity was characterized by an intermittent regime of alternating modes of low and high alpha power. Responses were more biased in the former mode, indicating that perceptual bias was deployed actively to compensate for stimulus uncertainty. Thus, early stages of perceptual learning were characterized by episodes of greater reliance on prior visual preferences, alternating with episodes of receptivity to stimulus information. In the course of learning, the former episodes disappeared, and biases reappeared only infrequently.
    

29. Gepshtein S (2016). Walking through structured light. Proceedings of the Fifth International Light Symposium: Future of Healthy Light and Lighting in Daily Life. Wismar, Germany, October 12-14, 2016. [+]

    Moving through any complex environment presents the sighted individual with a sequence of visual experiences. Visual objects move in and out of the observer's awareness because of the changes in occlusion, but also because vision is not equally sensitive to the objects that appear in plain sight. To capture this dynamics we introduce the concept of "solid field of visibility" and the attendant quantitative model of spatial organization of experience. The model describes visibility of every part of the environment as a continuous function of observer location. Having the model built into drafting software will allow designers to predict which parts of an environment can be experienced at every location and where multiple parts can be experienced concurrently. The designer will be able to discover how the experience would change under different intensities and directions of lighting, static or dynamic.
    

30. Snider J, Lee D, Poizner H & Gepshtein S (2015). Prospective optimization with limited resources. PLoS Computational Biology, 11 (9): e1004501. doi:10.1371/journal.pcbi.1004501. [+]

    The future is uncertain because some forthcoming events are unpredictable and also because our ability to foresee the myriad consequences of our own actions is limited. Here we studied how humans select actions under such extrinsic and intrinsic uncertainty, in view of an exponentially expanding number of prospects on a branching multivalued visual stimulus.
    
    A triangular grid of disks of different sizes scrolled down a touchscreen at a variable speed. The larger disks represented larger rewards. The task was to maximize the cumulative reward by touching one disk at a time in a rapid sequence, forming an upward path across the grid, while every step along the path constrained the part of the grid accessible in the future. This task captured some of the complexity of natural behavior in the risky and dynamic world, where ongoing decisions alter the landscape of future rewards. By comparing human behavior with behavior of ideal actors, we identified the strategies used by humans in terms of how far into the future they looked (their "depth of computation") and how often they attempted to incorporate new information about the future rewards (their "recalculation period").
    
    We found that, for a given task difficulty, humans traded off their depth of computation for the recalculation period. The form of this tradeoff was consistent with a complete, brute-force exploration of all possible paths up to a resource-limited finite depth. A step-by-step analysis of the human behavior revealed that participants took into account very fine distinctions between the future rewards and that they abstained from some simple heuristics in assessment of the alternative paths, such as seeking only the largest disks or avoiding the smaller disks. The participants preferred to reduce their depth of computation or increase the recalculation period rather than sacrifice the precision of computation.
    
    

31. Gepshtein S, Li X, Snider J, Plank M, Lee D & Poizner H (2014). Dopamine function and the efficiency of human movement. Journal of Cognitive Neuroscience, 26 (3), 645-657, doi: 10.1162/jocn_a_00503. pdf

32. Savel'ev S & Gepshtein S (2014). Neural wave interference in inhibition-stabilized networks. Proceedings of the First International Electronic Conference on Entropy and its Applications, doi: 10.3390/ecea-1-c002. link | arXiv

33. Sejnowski TJ, Poizner H, Lynch G, Gepshtein S & Greenspan RJ (2014). Prospective optimization. Proceedings of the IEEE, 102 (5), 799-811. 10.1109/JPROC.2014.2314297. pdf

34. Park C, Plank M, Snider J, Kim S, He H, Gepshtein S, Coleman T, Poizner H (2014). EEG gamma band oscillations differentiate the planning of spatially directed movements of the arm versus eye: multivariate empirical mode decomposition analysis. IEEE Transactions on Neural Systems and Rehabilitation Engineering, 22 (5), 1083-1096, doi: 10.1109/TNSRE.2014.2332450. pdf

35. Gepshtein S & Tyukin I (2014). Optimal measurement of visual motion across spatial and temporal scales. In Favorskaya MN and Jain LC (Eds), Computer Vision in Advanced Control Systems using Conventional and Intelligent Paradigms, Intelligent Systems Reference Library, Springer-Verlag, Berlin, 211-238. preprint

36. Jurica P, Gepshtein S, Tyukin I & van Leeuwen C (2013). Optimal visual sensitivity from stochastic tuning. Psychological Review, 120 (4), 798-816, doi: 10.1037/a0034192. preprint

37. Gepshtein S, Lesmes LA & Albright TD (2013). Sensory adaptation as optimal resource allocation. Proceedings of the National Academy of Sciences, USA, 110 (11), 4368-4373, doi: 10.1073/pnas.1204109110. pdf

38. Kubovy M, Epstein W & Gepshtein S (2013). Visual perception: Theoretical and methodological foundations. In Healy AF & Proctor RW (Eds), Experimental Psychology, Second edition, 85-119, Volume 4 in Weiner IB (Editor-in-Chief) Handbook of Psychology. John Wiley & Sons, New York, USA. preview

39. Nikolaev AR, Gepshtein S & van Leeuwen C (2013). Spontaneous EEG activity and biases in perception of supra-threshold stimuli. In Yamaguchi Y (Ed) Advances in Cognitive Neurodynamics (III), Springer Science & Business Media, Dordrecht, pp 289-295, doi: 10.1007/978-94-007-4792-0_39. pdf

40. Alexander DM, Jurica P, Trengove C, Nikolaev AR, Gepshtein S et al (2013). Traveling waves and trial averaging: The nature of single-trial and averaged brain responses in large-scale cortical signals. NeuroImage, 73, p. 95-112, doi: 10.1016/j.neuroimage.2013.01.016. pdf

41. Plomp G, van Leeuwen C & Gepshtein S (2012). Perception of time in articulated visual events. Frontiers in Psychology, 3:564, 1-8, doi: 10.3389/fpsyg.2012.00564. pdf

42. Vidal-Naquet M & Gepshtein S (2012). Spatially invariant computations in stereoscopic vision. Frontiers of Computational Neuroscience, 6:47, 1-13, doi: 10.3389/fncom.2012.00047. pdf

43. Wagemans J, Feldman J, Gepshtein S, Kimchi R, Pomerantz JR et al (2012). A century of Gestalt psychology in visual perception. Conceptual and theoretical foundations. Psychological Bulletin, 138 (6), 1218-1252. pdf

44. Gepshtein S, Tyukin I & Kubovy M (2011). A failure of the proximity principle in the perception of motion. Humana Mente, 17, 21-34. pdf

45. Gepshtein S (2010). Two psychologies of perception and the prospect of their synthesis. Philosophical Psychology, 23 (2), 217-281. pdf

46. Nikolaev AR, Gepshtein S, Gong P & van Leeuwen C (2009). Duration of coherence intervals in electrical brain activity in perceptual organization. Cerebral Cortex, 20 (2), 365-382. pdf

47. Gepshtein S (2009). Closing the gap between ideal and real behavior: Scientific vs. engineering approaches to normativity. Philosophical Psychology, 22 (1), 61-75. pdf

48. Nikolaev AR, Gepshtein S, Kubovy M & van Leeuwen C (2008). Dissociation of early evoked cortical activity in perceptual grouping. Experimental Brain Research, 186 (1), 107-122. pdf

49. Gepshtein S, Elder JH & Maloney LT (2008). Perceptual organization and neural computation. Journal of Vision, 8 (7), 1-4. pdf

50. Jurica P, Gepshtein S, Tyukin I, Prokhorov D & van Leeuwen C (2007). Unsupervised adaptive optimization of motion-sensitive systems guided by measurement uncertainty. Proceedings of the third international conference on intelligent sensors. Sensor networks and information processing (ISSNIP 2007), 179-184. pdf

51. Gepshtein S & Kubovy M (2007). The lawful perception of apparent motion. Journal of Vision, 7 (8):9, 1-15. pdf

52. Gepshtein S, Tyukin I & Kubovy M (2007). The economics of motion perception and invariants of visual sensitivity. Journal of Vision, 7 (8):8, 1-18. pdf

53. Nikolaev AR, Gepshtein S, Kubovy M & van Leeuwen C (2007). Temporal structure of perceptual grouping: EEG analysis. In Mori S, Miyaoka T & Wong W (Eds) Fechner Day 2007, pp 67-72. Proceedings of the 23rd Annual Meeting of the International Society for Psychophysics, Tokyo, Japan.

54. Gepshtein S, Tyukin I & Kubovy M (2007). Why does the proximity principle fail in perception of motion? In Mori S, Miyaoka T & Wong W (Eds) Fechner Day 2007, pp 57-62. Proceedings of the 23rd Annual Meeting of the International Society for Psychophysics, Tokyo, Japan.

55. Gepshtein S, Seydell A & Trommershäuser J (2007). Optimality of human movement under natural variations of visual-motor uncertainty. Journal of Vision, 7 (5):13, 1-18. pdf supplement

56. Trommershäuser J, Gepshtein S, Maloney LT, Landy MS & Banks MS (2005). Optimal compensation for changes in task relevant movement variability. Journal of Neuroscience, 25 (31), 7169-7178. pdf

57. Banks MS, Gepshtein S & Rose HF (2005). Local cross-correlation model of stereo correspondence. Proceedings of SPIE: Human Vision and Electronic Imaging, 5666, 53-61.

58. Gepshtein S & Kubovy M (2005). Stability and change in perception: Spatial organization in temporal context. Experimental Brain Research, 160 (4), 487-495. pdf reveiw

59. Gepshtein S, Burge J, Ernst M & Banks MS (2005). The combination of vision and touch depends on spatial proximity. Journal of Vision, 5 (11):7, 1013-1023. pdf

60. Banks MS, Gepshtein S & Landy MS (2004). Why is spatial stereoresolution so low? Journal of Neuroscience, 24 (9), 2077-2089. pdf

61. Kubovy M & Gepshtein S (2003). Perceptual grouping in space and in space-time: An exercise in phenomenological psychophysics. In Behrmann M, Kimchi R, and Olson CR (Eds) Perceptual Organization in Vision: Behavioral and Neural Perspectives, 45-85. Lawrence Erlbaum, Mahwah, NJ, USA. preprint

62. Gepshtein S & Banks MS (2003). Viewing geometry determines how vision and touch combine in size perception. Current Biology, 13 (6), 483-488. pdf

63. Kubovy M, Epstein W & Gepshtein S (2002). Foundations of visual perception. In Healy AF & Proctor RW (Eds), Experimental Psychology, 87-119, Volume 4 in Weiner IB (Editor-in-Chief) Handbook of Psychology. John Wiley & Sons, New York, USA.

64. Kubovy M & Gepshtein S (2000). Gestalt: From phenomena to laws. In Boyer KL and Sarkar A (Eds) Perceptual Organization for Artificial Vision Systems, 41-71. Kluwer Academic Publishers, Boston, MA, USA. pdf

65. Gepshtein S & Kubovy M (2000). The emergence of visual objects in space-time. Proceedings of the National Academy of Sciences, USA, 97 (14), 8186-8191. pdf

66. Gepshtein S & Cooperman A (1998). Stereoscopic transparency: a test for binocular vision's disambiguating power. Vision Research, 38, 2913-2932.