Everything is illuminated: Prismatic adaptation lowers visual detection threshold in normal subjects.

2018 ◽  
Vol 44 (10) ◽  
pp. 1619-1628 ◽  
Author(s):  
Irene Ronga ◽  
Pietro Sarasso ◽  
Carlotta Fossataro ◽  
Adriana Salatino ◽  
Francesca Garbarini ◽  
...  
Keyword(s):  
Visual Detection ◽  
Detection Threshold ◽  
Normal Subjects ◽  
Prismatic Adaptation

Effect of foveal tritanopia on reaction times to chromatic stimuli

2004 ◽  
Vol 21 (3) ◽  
pp. 237-242 ◽  
Author(s):  
N.R.A. PARRY ◽  
S. PLAINIS ◽  
I.J. MURRAY ◽  
D.J. McKEEFRY
Keyword(s):  
Detection Threshold ◽  
Color Space ◽  
Reaction Times ◽  
Normal Subjects ◽  
Gain Function ◽  
Contrast Function ◽  
Contrast Gain ◽  
Free Zone ◽  
Color Vector ◽  
Marked Drop

To investigate the effect of foveal inhomogeneities on sensitivity to chromatic stimuli, we measured simple reaction times (RTs) and detection thresholds to temporally and spatially blurred isoluminant stimuli at retinal eccentricities from 0 deg to 8 deg. Three color-normal subjects participated. Contrast gain was derived from the slope of the RT versus contrast function. With a Gaussian spatial distribution (S.D. = 0.5 deg) and modulation between white (CIE x,y,L = 0.31, 0.316, 12.5 cd.m−2) and blue (MBDKL 90 deg), gain was maximal at about 2-deg eccentricity and declined by approximately 1 log unit towards the center and the periphery. The red (0 deg) and green (180 deg) cardinal axes showed maximum gain in the center, whilst the yellow (270 deg) data were intermediate. Although the spatial extent of the Gaussian spot was much larger than the S-cone free zone, we wished to determine whether foveal tritanopia was responsible for the marked drop in sensitivity to the 90-deg stimulus. To align the color vector along a tritan line, we used a smaller disk (0.3 deg) with a blurred edge and measured detection threshold, rotating the vector until minimum central sensitivity was obtained. Other workers have used transient tritanopia or minimally distinct border to similar effect. By repeating this at different locations in color space, a group of vectors were obtained. These converged near to the S-cone co-punctal point, evidence that they lay along tritan confusion lines. These threshold findings were then confirmed using the RT-derived contrast gain function. The tritan vectors were less pronounced as stimulus size increased. With the vector optimized to produce foveal tritanopia, the RT gain versus eccentricity functions for the 90-deg and 270-deg stimuli both fell markedly in the center and periphery, and sensitivity peaked at about 3-deg eccentricity. There are some similarities between these findings and the underlying photoreceptor distributions. As a result, there is a greater difference in gain between red–green and blue–yellow systems in the center than in the near periphery. We conclude that the RT versus contrast function is a sensitive index of foveal opponency.

scholarly journals Visual detection threshold differences between psychiatric patients and normal controls

1980 ◽  
Vol 15 (2) ◽  
pp. 69-72 ◽  
Author(s):  
Salvatore Mannuzza ◽  
Bonnie J. Spring ◽  
Michael D. Gottlieb ◽  
Mitchell L. Kietzman
Keyword(s):  
Visual Detection ◽  
Psychiatric Patients ◽  
Detection Threshold ◽  
Normal Controls

scholarly journals Active sensing with light improves predator detection in a diurnal fish

2018 ◽  
Author(s):  
Matteo Santon ◽  
Pierre-Paul Bitton ◽  
Jasha Dehm ◽  
Roland Fritsch ◽  
Ulrike K. Harant ◽  
...  
Keyword(s):  
Field Experiment ◽  
Visual Detection ◽  
Average Distance ◽  
Detection Threshold ◽  
Active Sensing ◽  
Predator Detection ◽  
Light Organs ◽  
Anatomical Arrangement ◽  
Favorable Conditions

AbstractActive sensing by means of light is rare. In vertebrates, it is known only from chemiluminescent fish with light organs below their pupils, an anatomical arrangement that is ideal to generate eyeshine in the pupils of nearby organisms. Here, we test whether diurnal fish can achieve the same by redirecting sunlight through reflection instead. We recently showed that small (< 5 cm), benthic, marine triplefin fish actively redirect downwelling light using their iris. We hypothesized that this mechanism allows triplefins to improve detection of a cryptic organism by generating eyeshine in its pupil. Here, we tested this by attaching small dark hats to triplefins to shade their iris from downwelling light. Two controls consisted of triplefins with a clear or no hat. These treatments test the prediction that light redirection increases the visual detection ability of triplefins. To this end, we placed treated fish in a tank with a display compartment containing either a stone as the control stimulus, or a scorpionfish, i.e. a cryptic, motionless triplefin predator with retroreflective eyes. After overnight acclimatization, we determined the average distance triplefins kept from the display compartment over two days. Both in the laboratory (n = 15 replicates per treatment) and in a similar field experiment at 15 m depth (n = 43 replicates per treatment) fish kept longer distances from the scorpionfish than from the stone. This response varied between hat treatments: shaded triplefins stayed significantly closer to the scorpionfish in the laboratory and in one of two orientations tested in the field. A follow-up field experiment at 10 m depth revealed the immediate response of triplefins to a scorpionfish. At first, many individuals (n = 80) moved towards it, with shaded triplefins getting significantly closer. All individuals then gradually moved to a safer distance at the opposite half of the tank. Visual modelling supported the experimental results by showing that triplefins can redirect enough light with their iris to increase a scorpionfish’s pupil brightness above detection threshold at a distance of 7 cm under average field conditions and at more than 12 cm under favorable conditions. We conclude that triplefins are generally good in the visual detection of a cryptic predator, but can significantly improve this ability when able to redirect downwelling light with their iris and induce eyeshine in the predator’s pupil. We discuss the consequences of “diurnal active photolocation” for visual detection and camouflage among fish species.

scholarly journals The neural correlates of the visual consciousness in schizophrenia: an fMRI study

2020 ◽  
Author(s):  
S. Lefebvre ◽  
E. Very ◽  
R. Jardri ◽  
M. Horn ◽  
A. Yrondi ◽  
...  
Keyword(s):  
Anterior Cingulate Cortex ◽  
Visual Detection ◽  
Detection Threshold ◽  
Cingulate Cortex ◽  
Anterior Cingulate ◽  
Large Network ◽  
Unconscious Processing ◽  
Consciousness Disorders ◽  
Visual Inputs ◽  
Visual Consciousness

Abstract In the current literature, two distinct and opposite models are suggested to explain the consciousness disorders in schizophrenia. The first one suggests that consciousness disorders rely on a low-level processing deficit, when the second model suggests that consciousness disorders rely on disruption in the ability to consciously access information, with preserved unconscious processing. The current study aims to understand the mechanisms associated with visual consciousness disorder in order to pave the road that will settle the debate regarding these hypotheses. During a functional magnetic resonance imaging session, 19 healthy participants (HC) and 15 patients with schizophrenia (SCZ) performed a visual detection task to compare the neural substrates associated with the conscious access to the visual inputs. The visual detection threshold was significantly higher in SCZ than in HC [t(32) = 3.37, p = 0.002]. Whole-brain ANOVA demonstrated that around the visual detection threshold patients with SCZ failed to activate a large network of brain areas compared to HC. (1) During conscious vision, HC engaged more the left cuneus and the right occipital cortex than patients with SCZ, (2) during unconscious vision, HC engaged a large network that patients with SCZ failed to activate, and finally, (3) during the access to consciousness process, patients with SCZ failed to activate the anterior cingulate cortex. These results suggest that the consciousness disorders in schizophrenia rely on specific dysfunctions depending on the consciousness stage. The disorders of the conscious vision are associated with dysfunction of occipital areas while the ones associated with unconscious vision rely on a large widespread network. Finally, the conscious access to the visual inputs is impaired by a dysfunction of the anterior cingulate cortex. The current study suggests that none of the two suggested models can explain consciousness disorders in schizophrenia. We suggest that there is an alternative model supporting that the conscious access to visual inputs is due to a disengagement of the supragenual anterior cingulate during the unconscious processing of the visual inputs associated with a sensory deficit.

Auditory Selective Attention in Cerebral-Palsied Individuals

1985 ◽  
Vol 16 (4) ◽  
pp. 260-266 ◽  
Author(s):  
Lee Ann Laraway
Keyword(s):  
Selective Attention ◽  
White Noise ◽  
Normal Subjects ◽  
Auditory Selective Attention ◽  
Normal Individuals ◽  
Significant Difference

The purpose of this study was to determine whether there is a statistically significant difference between the auditory selective attention abilities of normal and cerebral-palsied individuals. Twenty-three cerebral-palsied and 23 normal subjects between the ages of 5 and 21 were asked to repeat a series of 30 items consisting of from 2 to 4 digits in the presence of intermittent white noise. Results of the study indicate that cerebral-palsied individuals perform significantly poorer than normal individuals when the stimulus is accompanied by noise. Noise was not a significant factor in the performance of the normal subjects regardless of age.

The Effect of Stapedectomy on the Loudness of One’s Own Voice

1965 ◽  
Vol 8 (3) ◽  
pp. 223-234 ◽  
Author(s):  
William Melnick
Keyword(s):  
Middle Ear ◽  
Normal Subjects ◽  
Sound Energy ◽  
Loudness Function ◽  
Before And After ◽  
Increased Sensitivity

Five subjects with normal middle ear mechanisms, and otosclerotic patients, before and after stapedectomy, matched the loudness of their voices to the loudness of a 125-cps-sawtooth noise. The results showed loudness matching functions with gradual slopes, less than 1.00, for the normal subjects and the patients prior to stapedectomy. Post-surgically, the loudness function for the patients increased in steepness to considerably more than 1.00. These results are explained, most logically, in terms of increased sensitivity of the altered middle ear to sound energy generated by the listener’s own voice.

Delayed Auditory Feedback with Different Delay Times at Each Ear

1964 ◽  
Vol 7 (4) ◽  
pp. 369-371
Author(s):  
Samuel Fillenbaum
Keyword(s):  
Delay Interval ◽  
Auditory Feedback ◽  
Normal Subjects ◽  
Delayed Auditory Feedback ◽  
Delay Times

Binaurally asynchronous delayed auditory feedback (DAF) was compared with synchronous DAF in 80 normal subjects. Asynchronous DAF (0.10 sec difference) did not yield results different from those obtained under synchronous DAF with a 0.20 sec delay interval, an interval characteristically resulting in maximum disruptions in speech.

Object Transformations in the Play of Language-Impaired Children

1988 ◽  
Vol 53 (4) ◽  
pp. 459-466 ◽  
Author(s):  
Brenda Y. Terrell ◽  
Richard G. Schwartz
Keyword(s):  
Normal Subjects ◽  
Play Behavior ◽  
Chronological Age ◽  
Standard Group ◽  
Language Impaired ◽  
Normal Language ◽  
Mean Length Of Utterance ◽  
Impaired Children

The play behavior of 10 language-impaired children was observed. Their performances in play were compared to those of 10 normal-language children matched for chronological age as well as to those of 10 normal-language children matched for mean length of utterance. The children were observed as they played spontaneously with a standard group of toys and as they played with objects that required object transformations for successful play. The chronological age-matched normal subjects showed a trend toward performance of more object transformations in play than either the language-impaired or younger normal-language children. Additionally, although object transformations were observed in both segments, all children performed more object transformations with objects than with toys.

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