Visual coherence of moving and stationary image changes

AbstractDetection thresholds were compared for moving and stationary oscillations with equivalent contrast changes. Motion was more detectable than stationary oscillation, and the difference increased with size of the feature (a Gaussian blob). Phase discriminations between a center and two flanking features were much better for motion than for stationary oscillation. Motion phase discriminations were similar to motion detection and were robust over increases in spatial separation and temporal frequency, but not so for stationary oscillations. Separate visual motion signals were positively correlated, but visual signals for stationary oscillation were negatively correlated. Evidently, motion produces visually coherent changes in image structure, but stationary contrast oscillation does not

Spatial and temporal limits of motion perception across variations in speed, eccentricity, and low vision

We evaluated spatial displacement and temporal duration thresholds for discriminating the motion direction of gratings for a broad range of speeds (0.06-/s to 30-/s) in fovea and at T30-eccentricity. In general, increased speed yielded lower duration thresholds but higher displacement thresholds. In most conditions, these effects of speed were comparable in fovea and periphery, yielding relatively similar thresholds not correlated with decreased peripheral acuity. The noteworthy exceptions were interactive effects at slow speeds: (1) Displacement thresholds for peripheral motion were affected by acuity limits for speeds below 0.5-/s. (2) Low-vision observers with congenital nystagmus had elevated thresholds for peripheral motion and slow foveal motion but resembled typically sighted observers for foveal motions at speeds above 1-/s. (3) Suppressive center-surround interactions were absent below 0.5-/s and their strength increased with speed. Overall, these results indicate qualitatively different sensitivities to slow and fast motions. Thresholds for very slow motion are limited by spatial resolution, while thresholds for fast motion are probably limited by temporal resolution

On the interplay of temporal resolution power and spatial suppression in their prediction of psychometric intelligence.

As a measure of the brain's temporal fine-tuning capacity, temporal resolution power (TRP) explained repeatedly a substantial amount of variance in psychometric intelligence. Recently, spatial suppression, referred to as the increasing difficulty in quickly perceiving motion direction as the size of the moving stimulus increases, has attracted particular attention, when it was found to be positively related to psychometric intelligence. Due to the conceptual similarities of TRP and spatial suppression, the present study investigated their mutual interplay in the relation to psychometric intelligence in 273 young adults to better understand the reasons for these relationships. As in previous studies, psychometric intelligence was positively related to a latent variable representing TRP but, in contrast to previous reports, negatively to latent and manifest measures of spatial suppression. In a combined structural equation model, TRP still explained a substantial amount of variance in psychometric intelligence while the negative relation between spatial suppression and intelligence was completely explained by TRP. Thus, our findings confirmed TRP to be a robust predictor of psychometric intelligence but challenged the assumption of spatial suppression as a representation of general information processing efficiency as reflected in psychometric intelligence. Possible reasons for the contradictory findings on the relation between spatial suppression and psychometric intelligence are discussed

S4: Summary

Motion perception is arguably the best understood visual sub-modality, largely because of longstanding research focus using a range of converging methodological approaches. This symposium will present recent advances in this active field of research. Talks will report results from psychophysics, neurophysiology, computational modeling, and neuroimaging

S4-5: Perceptual and Neural Consequences of Rapid Motion Adaptation

Nervous systems adapt to the prevailing sensory environment, and the consequences of this adaptation can be observed both in the responses of single neurons and in perception. Given the variety of time-scales underlying events in the natural world, determining the temporal characteristics of adaptation is important to understanding how perception adjusts to its sensory environment. Previous work has shown that neural adaptation can occur on a timescale of milliseconds, but perceptual adaptation has typically been studied over relatively long timescales, typically on the order of seconds. This disparity raises important questions: Can perceptual adaptation be observed at brief, functionally relevant timescales? And if so, how do its properties relate to the rapid adaptation seen in cortical neurons? We address these questions in the context of visual motion processing, a perceptual modality characterized by rapid temporal dynamics. We demonstrate objectively that 25 ms of motion adaptation is sufficient to generate a motion-after-effect (MAE), an illusory sensation of movement experienced when a moving stimulus is replaced by a stationary pattern. This rapid adaptation occurs regardless of whether or not the adapting motion is perceived. In neurophysiological recordings from cortical area MT, we find that brief motion adaptation evokes direction-selective responses to subsequently presented stationary stimuli. A simple model shows that these neural responses can explain consequences of rapid perceptual adaptation. Overall we show that the MAE is not merely an intriguing perceptual illusion, but rather a reflection of rapid neural and perceptual processes that can occur essentially every time we experience motion

Illusory Centrifugal Motion Direction Observed in Brief Stimuli: Psychophysics and Energy Model

All stationary stimuli of fixed duration have motion energy and the amount of motion energy increases with decreasing duration. Consequently, perception of motion direction could be biased if the readout mechanisms are unbalanced. Previous physiological study showed prefered direction of MT neurons in peripheral tend to be oriented away from fovea(Albright, 1989). Given the broadening of motion energy in brief stimuli, such effect should increase as the stimulus duration decreases. Here, we tested this hypothesis by presenting vertical gratings (0.5c/deg, raised cosine spatial envelope, radius = 5deg, 98% contrast) with different speeds(2,4,8 16deg/sec) and direction(moving towards fovea or moving away from fovea). And Stimuli were presented in a temporal Gaussian envelope with durations ranging between 5 and 500ms. Observers' task was to identify perceived motion direction (guessing when unsure). Results showed that as predicted, the observers were biased to perceive these stimuli as moving away from fovea. In summary, briefly presented stationary stimuli are perceived as moving in centrifugal direction when presented in visual periphery. One possible explanation for this illusion is that these stimuli, by virtue of their broad temporal frequency spectrum, stimulate centrifugally biased motion mechanisms in area MT

A novel conceptual framework for cognitive reserve : using a multidimensional psychosomatic approach

Thesis (Ph. D.)--University of Rochester. Department of Brain and Cognitive Sciences, 2024.Older adults aged 85 years and older are at highest risk for Alzheimer's disease (AD), a progressive neurodegenerative disease characterized by abnormal accumulation of amyloid beta and tau proteins, neurodegeneration, and cognitive impairment. However, not all older adults with AD neuropathology ultimately develop AD, suggesting that there are unaccounted for factors that contribute to the nonlinear relationship between brain aging and cognition. This observation motivated the concept of cognitive reserve (CR) to explain why some individuals are better able to cope with brain pathology than others. However, existing operationalizations fail to capture the fundamental conceptual components of CR, particularly cognitive change (i.e., plasticity). As a result, there is little to no mechanistic evidence for CR. This dissertation presents a novel conceptual framework for CR that uses multidimensional (i.e., trait, state, level, and stability) psychosomatic factors to explain individual variability in the relationship between brain aging and cognition, encompassing both cognitive level and cognitive change. First, we establish a relationship between a psychosomatic factor, trait fatigue, and brain topology, and second, we identify a potential brain mechanism associated with brain aging and fatigue (Chapter 2). Next, we assess the relationship between fatigue and CR and examine how different dimensions of fatigue affect this relationship in older adults with and without mild cognitive impairment (MCI; Chapter 3). Finally, we test the moderating role of a second psychosomatic factor, positive affective experience, on the relationship between neurodegeneration and cognitive change in MCI, and whether preserved resting-state network functional connectivity attenuates the adverse effects of neurodegeneration on older adults' capacity for plasticity (Chapter 4). By using psychosomatic dimensions as different "operational" definitions of timescale, we show that psychosomatic factors differentially moderate the adverse effects of neurodegeneration on cognition, which in turn promote cognitive resilience or exacerbate vulnerability to brain aging. The inclusion of timescale captures an individual's capacity for plasticity, a component that has been theoretically implied in the existing literature but not operationally implemented. To our knowledge, these findings provide the first empirically viable evidence for CR and establish a foundation for future confirmatory research

Influences of selective attention during binocular rivalry

Thesis (Ph. D.)--University of Rochester. Department of Brain & Cognitive Sciences, 2014.Binocular rivalry is a unique perceptual phenomenon in which sensation and perception are dissociated. Despite the presentation of unchanging sensory stimulation (disparate images in each of the two eyes), an observer's perceptual experience fluctuates between the two equally plausible interpretations of the input. Perhaps surprisingly, one consistent finding is that this process is largely inaccessible to selective attentional control - in other words, observers cannot willfully cause greater predominance of one or the other image, except under certain special circumstances. Because this paradigm so starkly illustrates the limits of voluntary attention, it represents a unique opportunity for studying the factors that promote attentional control. The series of studies comprising this thesis are designed to investigate ways of overcoming the limitations of attentional control during binocular rivalry. To begin, the complex pattern of results in the attention and rivalry literature are explained within the framework of the biased competition theory of attention, a theory that is found to synthesize seemingly diverse results from previous studies. This framework is then tested in a number of studies, with results supporting several predictions arising from this novel understanding. First, we find that direct practice at a demanding perceptual task during binocular rivalry can give rise to profound selective control. We next investigate whether this increase in attentional control of binocular rivalry might also be achieved through less direct training. Specifically, we compared attentional control of binocular rivalry in video game players and experienced psychophysical observers to control in non-gamers, and found some support for the idea that extensive visual training may be necessary for observers to attentionally control binocular rivalry. Finally, we tested how the effects of attention over binocular rivalry change throughout its timecourse and found that attentional control emerges near the end of each percept, as competition between stimuli becomes less resolved. Taken together, these experiments reveal ways of overcoming limitations in attentional control of visual perception, and demonstrate a key role of visual competition in the activity of attentional mechanisms

A mechanistic understanding of atypical visual processing in Autism Spectrum Disorder

Thesis (Ph. D.)--University of Rochester. Department of Brain and Cognitive Sciences, 2017.A growing number of studies suggest atypical visual processing in autism spectrum disorder (ASD). Given that human behavior heavily relies on visual information, impairments in visual processing may have cascading effects on many other brain functions. Recent proposals in ASD, both domain-specific and -general, hypothesize different mechanisms that may impact visual abilities in this population. However, empirical support for such accounts has been lacking, and it is unclear whether and how these mechanisms can influence visual perception in ASD. The series of studies in this dissertation examine atypical visual processing mechanisms in ASD under three frameworks: larger receptive field size, elevated internal noise, and impaired prediction abilities. We examine each of these hypotheses in children and adolescents with ASD, using a combination of psychophysics, computational modeling, and eye-tracking. In Chapter 2, we tested the integrity of receptive field size using a visual motion discrimination task. The results showed that individuals with ASD have impaired motion sensitivity at smaller stimulus size, which was best explained by the larger receptive field size account. In Chapter 3, we investigated whether internal noise is elevated in ASD, and found evidence that supports this account. Importantly, we found that higher internal noise was associated with more severe behavioral symptoms of ASD. Lastly, in Chapter 4, we examined the prediction abilities in ASD in the context of visual motion extrapolation. The results demonstrate impaired motion prediction in ASD, which was also accompanied by their atypical eye-movement patterns during the task. Taken together, these studies reveal deficits in visual processing in ASD across a wide range of processing stages. The findings not only provide empirical support for existing proposals of ASD, but also shed lights on the specific mechanisms associated with atypical visual abilities in this population