Context-dependent adaptation in the visual system

University of Minnesota Ph.D. dissertation. December 2017. Major: Psychology. Advisors: Stephen Engel, Sheng He. 1 computer file (PDF); vii, 131 pages.The visual system continuously adjusts its sensitivities to various visual features so as to optimize neural processing, a phenomenon known as adaptation. Although this rapid form of plasticity has been extensively studied across numerous sensory modalities, it remains unclear if its dynamics can change with experience. Specifically, the world we live in is composed of many different environments, or contexts, each of which contains its own statistical regularities. For example, forests contain more vertical energy and greenish hues than a desert landscape. Here we investigated the possibility that through experience, the visual system can learn statistical regularities in the visual input, and use this knowledge to adapt more quickly. In two sets of experiments, participants repeatedly adapted to previously unexperienced regularities in orientation statistics over the course of 3-4 sessions. They adapted either to rapidly presented sequences of oriented gratings containing orientation biases, or to natural visual input that was filtered to alter its orientation statistics. We found that experience did increase adaptation rate, but only in the experiments where participants adapted to a single set of altered statistics of natural input. We found no changes in adaptation rate in experiments where participants periodically switched between adapting to different statistical regularities. These results demonstrate that adaptation and experience can interact under some circumstances

FORUM:Remote testing for psychological and physiological acoustics

Acoustics research involving human participants typically takes place in specialized laboratory settings. Listening studies, for example, may present controlled sounds using calibrated transducers in sound-attenuating or anechoic chambers. In contrast, remote testing takes place outside of the laboratory in everyday settings (e.g., participants' homes). Remote testing could provide greater access to participants, larger sample sizes, and opportunities to characterize performance in typical listening environments at the cost of reduced control of environmental conditions, less precise calibration, and inconsistency in attentional state and/or response behaviors from relatively smaller sample sizes and unintuitive experimental tasks. The Acoustical Society of America Technical Committee on Psychological and Physiological Acoustics launched the Task Force on Remote Testing (https://tcppasa.org/remotetesting/) in May 2020 with goals of surveying approaches and platforms available to support remote testing and identifying challenges and considerations for prospective investigators. The results of this task force survey were made available online in the form of a set of Wiki pages and summarized in this report. This report outlines the state-of-the-art of remote testing in auditory-related research as of August 2021, which is based on the Wiki and a literature search of papers published in this area since 2020, and provides three case studies to demonstrate feasibility during practice

Spontaneous recovery of motion and face aftereffects

The ability of the visual system to rapidly adjust to changing environmental conditions is one of its key characteristics. Environmental changes can occur over a variety of timescales, however, and it remains unknown how the visual system adapts to these. Does a single mechanism control adaptation across all timescales, or is adaptation subserved by multiple mechanisms, each of which is tuned to its preferred duration? To address this question, we conducted three experiments in which subjects viewed motion (Exp. 1 and 2) or faces (Exp. 3) in a sequence designed to produce opposing aftereffects. A first adapter was presented for a relatively long duration, while a second one was presented only long enough to extinguish the effects of the initial adapter. Continued measurement of aftereffects revealed a spontaneous recovery of adaptation caused by the initial, longer-lasting adapter in all three experiments. This pattern of results suggests that adaptation in the visual system generally reflects a combination of multiple temporally-tuned mechanisms. (C) 2013 The Authors. Published by Elsevier Ltd. All rights reserved

High temporal resolution decoding of object position and category

We effortlessly and seemingly instantaneously recognize thousands of objects, although we rarely--if ever--see the same image of an object twice. The retinal image of an object can vary by context, size, viewpoint, illumination, and location. The present study examined how the visual system abstracts object category across variations in retinal location. In three experiments, participants viewed images of objects presented to different retinal locations while brain activity was recorded using magnetoencephalography (MEG). A pattern classifier was trained to recover the stimulus position (Experiments 1, 2, and 3) and category (Experiment 3) from the recordings. Using this decoding approach, we show that an object's location in the visual field can be recovered in high temporal resolution (5 ms) and with sufficient fidelity to capture topographic organization in visual areas. Experiment 3 showed that an object's category could be recovered from the recordings as early as 135 ms after the onset of the stimulus and that category decoding generalized across retinal location (i.e., position invariance). Our experiments thus show that the visual system rapidly constructs a category representation for objects that is invariant to position

Spontaneous recovery of motion and face aftereffects

The ability of the visual system to rapidly adjust to changing environmental conditions is one of its key characteristics. Environmental changes can occur over a variety of timescales, however, and it remains unknown how the visual system adapts to these. Does a single mechanism control adaptation across all timescales, or is adaptation subserved by multiple mechanisms, each of which is tuned to its preferred duration? To address this question, we conducted three experiments in which subjects viewed motion (Exp. 1 and 2) or faces (Exp. 3) in a sequence designed to produce opposing aftereffects. A first adapter was presented for a relatively long duration, while a second one was presented only long enough to extinguish the effects of the initial adapter. Continued measurement of aftereffects revealed a spontaneous recovery of adaptation caused by the initial, longer-lasting adapter in all three experiments. This pattern of results suggests that adaptation in the visual system generally reflects a combination of multiple temporally-tuned mechanisms. (C) 2013 The Authors. Published by Elsevier Ltd. All rights reserved

Distinct mechanisms control contrast adaptation over different timescales

Changes to the visual environment can happen at many timescales, from very transient to semi-permanent. To adapt optimally, the visual system also adjusts at different timescales, with longer-lasting environmental changes producing longer-lasting effects, but how the visual system adapts in this way remains unknown. Here, we show that contrast adaptation-the most-studied form of visual adaptation-has multiple controllers, each operating over a different time scale. In a series of experiments, subjects completed either a contrast matching, contrast detection, or tilt adjustment task, while adapting to contrast at one orientation. Following a relatively longer period (5 min) of adaptation to high contrast, subjects were "deadapted" for a shorter period (e. g., 40 s) to a lower contrast. Deadaptation eliminated perceptual aftereffects of adaptation, but continued testing in a neutral environment revealed their striking recovery. These results suggest the following account: Adaptation was controlled by at least two mechanisms, with initial adaptation affecting a longer-term one and deadaptation affecting a shorter-term one in the opposite direction. Immediately following deadaptation, the effects of the two mechanisms cancelled each other, but the short-term effects rapidly decayed, revealing ongoing longer-term adaptation. A single controlling mechanism cannot account for the observed recovery of effects, since once deadaptation cancels the initial longer-term adaptation, no trace of it remains. Combined with previous results at very long adaptation durations, the present results suggest that contrast adaptation is possibly controlled by a continuum of mechanisms acting over a large range of timescales

Beneficial Effects of Spatial Remapping for Reading With Simulated Central Field Loss

International audiencePURPOSE. People with central field loss (CFL) lose information in the scotomatous region. Remapping is a method to modify images to present the missing information outside the scotoma. This study tested the hypothesis that remapping improves reading performance for subjects with simulated CFL. METHODS. Circular central scotomas, with diameters ranging from 48 to 168, were simulated in normally sighted subjects using an eye tracker on either a head-mounted display (HMD) (experiments 1, 2) or a traditional monitor (experiment 3). In the three experiments, reading speed was measured for groups of 7, 11, and 13 subjects with and without remapping of text. RESULTS. Remapping increased reading speed in all three experiments. On the traditional monitor, it increased reading speed by 34% (88), 38% (128), and 35% (168). In the two HMD experiments, remapping increased reading speed only for the largest scotoma size, possibly due to latency of updating of the simulated scotoma. CONCLUSIONS. Remapping significantly increased reading speed in simulated CFL subjects. Additional testing should examine the efficacy of remapping for reading and other visual tasks for patients with advanced CFL