Abrupt darkening under high dynamic range (HDR) luminance invokes facilitation for high-contrast targets and grouping by luminance similarity.

When scanning across a scene, luminance can vary by up to 100,000-to-1 (high dynamic range, HDR), requiring multiple normalizing mechanisms spanning from the retina to the cortex to support visual acuity and recognition. Vision models based on standard dynamic range (SDR) luminance contrast ratios below 100-to-1 have limited ability to generalize to real-world scenes with HDR luminance. To characterize how orientation and luminance are linked in brain mechanisms for luminance normalization, we measured orientation discrimination of Gabor targets under HDR luminance dynamics. We report a novel phenomenon, that abrupt 10- to 100-fold darkening engages contextual facilitation, distorting the apparent orientation of a high-contrast central target. Surprisingly, facilitation was influenced by grouping by luminance similarity, as well as by the degree of luminance variability in the surround. These results challenge vision models based solely on activity normalization and raise new questions that will lead to models that perform better in real-world scenes.

A 100,000-to-1 high dynamic range (HDR) luminance display for investigating visual perception under real-world luminance dynamics.

BACKGROUND: Real-world illumination challenges both autonomous sensing and displays, because scene luminance can vary by up to 109-to-1, whereas vision models have limited ability to generalize beyond 100-to-1 luminance contrast. Brain mechanisms automatically normalize the visual input based on feature context, but they remain poorly understood because of the limitations of commercially available displays. NEW METHOD: Here, we describe procedures for setup, calibration, and precision check of an HDR display system, based on a JVC DLA-RS600U reference projector, with over 100,000-to-1 luminance dynamic range (636-0.006055 cd/m2), pseudo 11 bit grayscale precision, and 3 ms temporal precision in the MATLAB/Psychtoolbox software environment. The setup is synchronized with electroencephalography (EEG) and infrared eye-tracking measurements. RESULTS: We show display metrics including light scatter versus average display luminance (ADL), spatial uniformity, and spatial uniformity at high spatial frequency. We also show a luminance normalization phenomenon, contextual facilitation of a high contrast target, whose discovery required HDR display. COMPARISON WITH EXISTING METHODS: This system provides 100-fold greater dynamic range than standard 1000-to-1 contrast displays and increases the number of gray levels from 256 or 1024 (8 or 10 bits) to 2048 (pseudo 11 bits), enabling the study of mesopic-to-photopic vision, at the expense of spatial non-uniformities. CONCLUSIONS: This HDR research capability opens new questions of how visual perception is resilient to real-world luminance dynamics and will lead to improved visual modeling of dense urban and forest environments and of mixed indoor-outdoor environments such as cockpits and augmented reality. Our display metrics code can be found at https://github.com/USArmyResearchLab/ARL-Display-Metrics-and-Average-Display-Luminance.

The effects of simulated hearing loss on speech recognition and walking navigation.

OBJECTIVE: The objective was to assess whether a concurrent but independent navigation task exacerbates the effects of hearing loss on speech recognition and whether hearing loss degrades performance of the navigation task during the concurrent but independent listening task. BACKGROUND: Navigation performance and speech comprehension both decrease when a driver follows hard-to-hear concurrent verbal instructions. It remains unknown how much both tasks would be affected when performed concurrently, if tasks were independent. METHOD: Participants performed a listening task by responding to Callsign Acquisition Test (CAT) stimuli at three simulated hearing levels. For each hearing level, one trial was performed with the participant standing still and another trial was performed while navigating a path in a virtual environment using a handheld map. In one more trial, participants navigated a path with no CAT. The proportion of call signs correctly repeated and the total time required to walk the path were measured. RESULTS: CAT scores showed an expected negative effect of hearing loss. Concurrent navigation produced an even larger decrease in CAT score. Hearing loss caused a slight but not significant decrease in navigation task performance. CONCLUSION: A person with hearing loss may communicate less effectively while walking than predicted on the basis of hearing loss alone. The hearing loss, however, does not significantly decrease walking performance in a simple navigation task. APPLICATION: Obtained results may guide soldier performance modeling and requirements for communication systems used during physical activity when a soldier's hearing becomes compromised during dismounted combat operations.