Components Of Visual Stimuli Research Articles

Parallel visual circuitry in a basal chordate.

A common CNS architecture is observed in all chordates, from vertebrates to basal chordates like the ascidian Ciona. Ciona stands apart among chordates in having a complete larval connectome. Starting with visuomotor circuits predicted by the Ciona connectome, we used expression maps of neurotransmitter use with behavioral assays to identify two parallel visuomotor circuits that are responsive to different components of visual stimuli. The first circuit is characterized by glutamatergic photoreceptors and responds to the direction of light. These photoreceptors project to cholinergic motor neurons, via two tiers of cholinergic interneurons. The second circuit responds to changes in ambient light and mediates an escape response. This circuit uses GABAergic photoreceptors which project to GABAergic interneurons, and then to cholinergic interneurons. Our observations on the behavior of larvae either treated with a GABA receptor antagonist or carrying a mutation that eliminates photoreceptors indicate the second circuit is disinhibitory.

Toward A Location Based Service for Assessing and Recommending Landscape Views

GIScience 2016 Short Paper Proceedings Toward A Location Based Service for Assessing and Recommending Landscape Views S. Soleimani 1 , M. R. Malek 1 , G. Sinha 2 Geodesy & Geomatics Department, K.N.Toosi University of Technology, Tehran, Iran Email: {ssoleimani; mrmalek}@kntu.ac.ir Department of Geography, Ohio University, Athens, Ohio, 45701, USA Email: sinhag@ohio.edu Abstract The rationale and initial design considerations are presented for a location based service (LBS) that will offer people personalized recommendations for aesthetically desirable places. This will be based on people’s personal characteristics and environmental factors known to affect landscape perception. A prototype user-interface has been designed for eliciting users’ perceptions of landscape elements and colors they perceive from photographs of landscape views. In the long-term, a VGI repository database will be maintained to make personalized location specific recommendations about suitable landscape views for user-specified locations. A prototype fuzzy logic recommendation system comprising 72 rules has also been designed to model how personal factors (gender, age, health status) and perceived colors likely determine the aesthetic suitability of landscape views. An initial trial revealed some limitations and stressed the need for further testing of the feasibility of fuzzy logic as the reasoning framework for this LBS for recommending suitable landscape views. 1. Introduction As urbanity imposes psychological demands that become excessive, people seek stress- reducing (especially natural) environments where they can recreate and relax. The investigation of the ecological and visual aspects of physical landscapes is critical for understanding and addressing many of the psychosomatic disorders of urban dwellers. In this paper, we focus on visual perception of people’s everyday environments. Human-beings engage in a wide variety of important decisions in their everyday lives, based on visual properties of the geographic environment and their geographical knowledge. Examples include coping with environmental visual pollution, finding one’s way in spatially extended areas, and finding a landscape view appropriate to one’s emotional status. Color, shape, composition, and configuration of objects are important components of visual stimuli that should be studied to understand our perceptions of and reactions to physical landscapes in urban environments. In this short paper, we present the rationale and initial design considerations for a prototype Location Based Service (LBS) for landscape view assessment. This LBS will ultimately offer people personalized recommendations for places (near their chosen location(s)) that are most likely to appeal to them aesthetically. The LBS is designed to make such personalized recommendations based on available knowledge of how people’s personal characteristics affects landscape perception. A prototype user-interface has been designed for eliciting users’ perceptions about the types of landscape elements and the colors they perceive in images showing landscape views. An important goal of this project is to maintain a large database of people’s perception of landscape views, based on volunteered geographic information (VGI) generated from people tagging images uploaded by them and/or others.

Psychophysical aspects of contrast sensitivity

This paper reviews the psychophysical aspects of contrast sensitivity which concerns components of visual stimuli and the behavioural responses and methods used in contrast sensitivity testing. Some discussion is included of the different types of contrast sensitivity charts available as well as a brief background on the different types of graphical representations of contrast sensitivity and contrast visual acuities. Two illustrations alsodemonstrate stereo-pair representation of contrast visual acuities in the context of diabetic eyes. The doctoral research of the first author (AYS) that applies similar idea to understanding both inter- and intra-ocular variation of contrast visual acuities.

Priority of processing components of visual stimuli by 6-month-old infants

The present experiment was designed to investigate the priority with which 6-month-olds attend to stimuli containing both contextual and target information. The procedure involved a familiarization phase to a stimulus that contained a central target cue and a surrounding context followed by paired comparison novelty tests. Results indicate that when infants monitor the environment, background context cues receive attentional priority over target cues.

Assessing the primary moments in infant encoding of compound visual stimuli

In order to assess whether the chromatic and spatial components of visual stimuli are initially encoded in a compound way, a backward-masking procedure was used in a series of five experiments involving 60 infants ( M age = 23 weeks, SD = 3.9). The duration of encoding intervals was varied across the experiments, but in all cases, infants were familiarized to a bicolored stimulus followed after each exposure by a masking stimulus. Encoding of the target stimulus was subsequently assessed on tests pairing this stimulus either with its chromatic reversal or with an identical pattern in new colors. The pattern of test performance across the five experiments indicated that infants were able to encode the colors of the target stimulus in correct spatial locations but may not necessarily do so from the earliest phases of response.

Molecular differences among neurons reveal an organization of human visual cortex.

Monoclonal antibody Cat-301 recognizes a cell-surface proteoglycan on subsets of neurons in several areas of the cat and macaque monkey central nervous system. In striate and extrastriate visual cortex of the macaque, the distribution of Cat-301-positive neurons demonstrates features of cellular organization that correlate with previously described functional subdivisions. Here we show that Cat-301 recognizes an antigen in human cortex that is closely related, if not identical, to the antigen in laboratory animals. Further, we use Cat-301 to demonstrate an organization of molecularly defined neurons in primary and secondary visual cortex (cortical areas V1 and V2) of the human. The organization demonstrated with Cat-301 in human area V1 correlates with the organization of ocular dominance columns demonstrated by cytochrome oxidase histochemistry. The organization demonstrated with Cat-301 in human area V2 correlates with the thick stripes of the cytochrome oxidase pattern. The present observations provide evidence for a visual pathway in human cortex homologous to the magnocellular pathway in macaque, a pathway involved in processing the low-contrast, achromatic, and moving components of visual stimuli.

Preattentive deficit in temporal processing by chronic schizophrenics

Preattentive visual filtering by two types of neural cells (transient and sustained) constitutes the basic neural correlates underlying visual perception. Transient cells respond abruptly to temporal modulation and to the low spatial frequency components of visual stimuli. Their function is localization of objects and global perception (i.e., detection). Sustained cells respond slowly and selectively to high spatial frequencies and are believed to be responsible for the “oblique effect” (i.e., reduced responsiveness to obliquely oriented high spatial frequencies), which likely occurs at the striate cortex. Their function is to discern the details of an object (i.e., identification). The present study evaluated early visual processing in normal controls and schizophrenics by presenting vertical and oblique (45°) spatial frequency gratings of 0.9 and 12 c/deg that were presented for 50, 100, 175, and 250-msec pulses. Threshold, in milliseconds, to detect an interstimulus interval (ISI) between two grating pulses was the dependent measure. Schizophrenics required longer ISIs for each grating duration, except for 250 msec, and longer ISIs for the 15 c/deg oblique grating. The results indicate that schizophrenics have a preattentive processing deficit that is further elaborated at the cortical level.