http://hdl.handle.net/2144/1897 Center for Adaptive Systems / Cognitive and Neural Systems technical reports series 2013-05-18T11:53:18Z http://hdl.handle.net/2144/2377 Logic and Phenomenology of Incompleteness in Illusory Figures: New Cases and Hypotheses Pinna, Baingio; Grossberg, Stephen Cognitive and gestalt visions theories consider incompleteness to be a necessmy and sufficient factor for inducing illusory figures. The role of incompleteness is studied herein by defining the inner logic subtended by use of the term "incompleteness", presenting new cases to clarify the phenomenology of incompleteness as a necessary and sufficient condition, and suggesting an alternative hypothesis to explain illusory figures after analyzing problems with the incompleteness hypothesis. It is demonstrated that incompleteness is not a sufficient condition, illusory figures do not necessarily complete incompletenesses, the shape of incompleteness does not predict the shape of illusory figures, and incompleteness is not a necessary condition. Finally, it is noted that the incompleteness hypothesis can be replaced by concepts concerning interacting boundary grouping and surface filling-in processes during figure-ground segregation. The suggested hypothesis is consistent with neurophysiological experiments and is described in terms of the FACADE neural model of boundary and surface formation during figure-ground segregation. 2005-03-01T00:00:00Z http://hdl.handle.net/2144/2378 ClasserScript v1.1 User's Guide Martens, Siegfried 2005-05-01T00:00:00Z http://hdl.handle.net/2144/2379 EyeRIS: A General-Purpose System for Eye Movement Contingent Display Control Santini, Fabrizio; Redner, Gabriel; Lovin, Ramon; Rucci, Michele In experimental studies of visual performance, the need often emerges to modify the stimulus according to the eye movements perfonncd by the subject. The methodology of Eye Movement-Contingent Display (EMCD) enables accurate control of the position and motion of the stimulus on the retina. EMCD procedures have been used successfully in many areas of vision science, including studies of visual attention, eye movements, and physiological characterization of neuronal response properties. Unfortunately, the difficulty of real-time programming and the unavailability of flexible and economical systems that can be easily adapted to the diversity of experimental needs and laboratory setups have prevented the widespread use of EMCD control. This paper describes EyeRIS, a general-purpose system for performing EMCD experiments on a Windows computer. Based on a digital signal processor with analog and digital interfaces, this integrated hardware and software system is responsible for sampling and processing oculomotor signals and subject responses and modifying the stimulus displayed on a CRT according to the gaze-contingent procedure specified by the experimenter. EyeRIS is designed to update the stimulus within a delay of 10 ms. To thoroughly evaluate EyeRIS' perforltlancc, this study (a) examines the response of the system in a number of EMCD procedures and computational benchmarking tests, (b) compares the accuracy of implementation of one particular EMCD procedure, retinal stabilization, to that produced by a standard tool used for this task, and (c) examines EyeRIS' performance in one of the many EMCD procedures that cannot be executed by means of any other currently available device. 2005-09-01T00:00:00Z http://hdl.handle.net/2144/2376 Physical Limits to Spatial Resolution of Optical Recording: Clarifying the Spatial Structure of Cortical Hypercolumns Polimeni, Jonathan; Granquist-Fraser, Domhnull; Wood, Richard; Schwartz, Eric Neurons in macaque primary visual cortex are spatially arranged by their global topographic position and in at least three overlapping local modular systems: ocular dominance columns, orientation pinwheels, and cytochrome oxidase (CO) blobs. Individual neurons in the blobs are not tuned to orientation, and populations of neurons in the pinwheel center regions show weak orientation tuning, suggesting a close relation between pinwheel centers and CO blobs. However, this hypothesis has been challenged by a series of optical recording experiments. In this report, we show that the statistical error associated with photon scatter and absorption in brain tissue combined with theblurring introduced by the optics of the imaging system has typically been in the range of 250 μm. These physical limitations cause a systematic error in the location of pinwheel centers because of the vectorial nature of these patterns, such that the apparent location of a pinwheel center measured by optical recording is never (on average) in the correct in vivo location. The systematic positional offset is about 116 μtm, which is large enough to account for the claimed mis-alignment of CO blobs and pinwheel centers. Thus, optical recording, as it has been used to date, has insufficient spatial resolution to accurately locate pinwheel centers. The earlier hypothesis that CO blobs and pinwheel centers are co-terminous remains the only one currently supported by reliable observation. 2005-01-01T00:00:00Z