Factors contributing to the delay in the perception of the oculogravic illusion

Horizontal perception change delay of man after counter rotation - effects of pre-exposure conditions on visual discrimination recover

Impaired perceptual learning in a mouse model of Fragile X syndrome is mediated by parvalbumin neuron dysfunction and is reversible.

To uncover the circuit-level alterations that underlie atypical sensory processing associated with autism, we adopted a symptom-to-circuit approach in the Fmr1-knockout (Fmr1-/-) mouse model of Fragile X syndrome. Using a go/no-go task and in vivo two-photon calcium imaging, we find that impaired visual discrimination in Fmr1-/- mice correlates with marked deficits in orientation tuning of principal neurons and with a decrease in the activity of parvalbumin interneurons in primary visual cortex. Restoring visually evoked activity in parvalbumin cells in Fmr1-/- mice with a chemogenetic strategy using designer receptors exclusively activated by designer drugs was sufficient to rescue their behavioral performance. Strikingly, human subjects with Fragile X syndrome exhibit impairments in visual discrimination similar to those in Fmr1-/- mice. These results suggest that manipulating inhibition may help sensory processing in Fragile X syndrome

Graded exercises in visual discrimination

Thesis (M.A.)--Boston University, 1949. This item was digitized by the Internet Archive

The role of the perirhinal cortex in visual learning in the rat

The aim of this thesis was to investigate the role of the perirhinal cortex in visual discrimination learning in the rat. Experiment one measured postoperative reacquisition of two sets of concurrent visual discriminations acquired at different time intervals prior to surgery. Perirhinal ablation did not result in a temporally graded retention deficit, but a deficit limited to immediate postoperative performance. Experiment two measured postoperative acquisition of a new set of concurrent visual discriminations, with a stimuli set of 15 pairs, thereby increasing demands on stimuli identification. It was found that perirhinal ablation did not affect postoperative acquisition. Experiment 3a measured postoperative acquisition of a two choice visual discrimination and generalisations to it. Perirhinal ablation led to an impairment in performing the visual discrimination when presented in the generalisation task. Experiment 3b measured the effects of perirhinal ablation on postoperative performance in generalisation to a visual discrimination learnt prior to surgery. It was found that perirhinal ablation led to a deficit in generalising to transformations in stimuli form, but not to transformations in stimuli size. Experiment four measured acquisition of a titrating visual generalization task that increased demands on stimuli identification. Perirhinal ablation impaired acquisition of this task. Experiment five was designed to measure the effects of perirhinal ablation on acquisition of a generalization task with complex visual stimuli. However, neither the sham or perirhinal animals succeeded in learning the task. The final experiment measured postoperative acquisition of a simple visual discrimination and its partial reversal and acquisition of a biconditional visual discrimination task. Perirhinal ablation impaired acquisition of the biconditional discrimination, whereas acquisition of the simple discrimination and its reversal remained intact. Therefore, perirhinal ablation in the rat leads to selective impairments in the acquisition and retention of visual discrimination learning. These findings suggest that the perirhinal cortex may contribute to discrimination learning tasks that require the identification of complex visual stimuli

Single-trial analysis of EEG during rapid visual discrimination: enabling cortically-coupled computer vision

We describe our work using linear discrimination of multi-channel electroencephalography for single-trial detection of neural signatures of visual recognition events. We demonstrate the approach as a methodology for relating neural variability to response variability, describing studies for response accuracy and response latency during visual target detection. We then show how the approach can be utilized to construct a novel type of brain-computer interface, which we term cortically-coupled computer vision. In this application, a large database of images is triaged using the detected neural signatures. We show how ‘corticaltriaging’ improves image search over a strictly behavioral response

Limited-capacity mechanisms of visual discrimination

Discrimination thresholds of spatial frequency and choice reaction times (RT) were measured in three subjects who performed a dual-judgment delayed discrimination task. Two reference gratings were presented side-by-side with a 0-800 msec stimulus onset asynchrony (SOA), which were followed after a 5-sec retention interval by two test gratings. Subjects judged which component changed and which interval had the higher spatial frequency (SF). Thresholds in the dual-judgment task were four to six times higher than thresholds in single-judgment tasks. The SOA had only a moderate effect on discrimination thresholds, whereas the difference between the spatial frequencies of the two components had a highly significant effect. The discrimination thresholds increase with increasing spatial frequency difference for the lower SF component, while they decrease for the higher SF component. An analysis of the distribution of possible error types indicated that all subjects tended to respond more frequently that the higher SF component changed. This tendency led to more errors on trials where the low SF component changed. A post- hoc analysis revealed, in two of the three subjects, a significant correlation between Af/f and RT such that higher Af/f values were associated with lower RTs and vice versa

School aged children: Visual perception and reversal recognition of letters and numbers separately and in context

Visual discrimination, spatial orientation, and recognition of letters and numbers in context are important issues in helping young students achieve good literacy and numeracy standards. Thus, measures of Visual Discrimination of Upper Case Letters (VDUCL), Visual Discrimination of Lower Case Letters (VDLCL), and Visual Discrimination of Numbers (VDN) as well as Spatial Orientation of Letter and Number Pairs (SOLNP), Form Constancy of Letters and Numbers (FCLNP), Letter and Number Sequencing (LNS), Figure Ground of Letters in Words FGLW) and Figure Ground Numbers in Calculations (FGNC) must be linear and uni-dimensional so that student weaknesses can be identified objectively. The Simple Logistic Model of Rasch Measurement was used to order the items on a scale from easy to difficult and the student measures were calibrated on the same scale from low to high. In each scale, items were scored zero (for incorrect) and one (for correct). The student sample N=324 used in this study included pre-primary and primary students in Perth, Western Australia. The initial data were adjusted so that items which displayed misfit statistics were removed from each scale prior to final analysis. The final VDUCL scale (18 items), VDLCL scale (31 items), and VDN scale (14 items) each had a good fit to the measurement model, and were internally reliable. In each scale, there was good agreement about the item difficulties from easy to hard along the scale. Item discrimination and targeting was good. The scales allow teachers to objectively identify the letters and numbers that students find difficult to discriminate and those students who have poor visual discrimination skills of alphabet letters and numbers so that tailored teaching can be applied to those in need