scholarly journals A computational-observer model of spatial contrast sensitivity: Effects of wave-front-based optics, cone-mosaic structure, and inference engine

2019 ◽  
Vol 19 (4) ◽  
pp. 8 ◽  
Author(s):  
Nicolas P. Cottaris ◽  
Haomiao Jiang ◽  
Xiaomao Ding ◽  
Brian A. Wandell ◽  
David H. Brainard
Keyword(s):  
Wave Front ◽  
Contrast Sensitivity ◽  
Inference Engine ◽  
Mosaic Structure ◽  
Cone Mosaic ◽  
Spatial Contrast Sensitivity ◽  
Observer Model

scholarly journals A computational observer model of spatial contrast sensitivity: Effects of wavefront-based optics, cone mosaic structure, and inference engine

2018 ◽  
Author(s):  
Nicolas P. Cottaris ◽  
Haomiao Jiang ◽  
Xiaomao Ding ◽  
Brian A. Wandell ◽  
David H. Brainard
Keyword(s):  
Contrast Sensitivity ◽  
Human Performance ◽  
Inference Engine ◽  
Substantial Effect ◽  
Upper Bounds ◽  
Ideal Observer ◽  
Absolute Level ◽  
Spatial Frequencies ◽  
Spatial Contrast Sensitivity ◽  
Observer Model

We present a computational observer model of the human spatial contrast sensitivity (CSF) function based on the Image Systems EngineeringTools for Biology (ISETBio) simulation framework. We demonstrate that ISETBio-derived CSFs agree well with CSFs derived using traditional ideal observer approaches, when the mosaic, optics, and inference engine are matched. Further simulations extend earlier work by considering more realistic cone mosaics, more recent measurements of human physiological optics, and the effect of varying the inference engine used to link visual representations to psy-chohysical performance. Relative to earlier calculations, our simulations show that the spatial structure of realistic cone mosaics reduces upper bounds on performance at low spatial frequencies, whereas realistic optics derived from modern wavefront measurements lead to increased upper bounds high spatial frequencies. Finally, we demonstrate that the type of inference engine used has a substantial effect on the absolute level of predicted performance. Indeed, the performance gap between an ideal observer with exact knowledge of the relevant signals and human observers is greatly reduced when the inference engine has to learn aspects of the visual task. ISETBio-derived estimates of stimulus representations at different stages along the visual pathway provide a powerful tool for computing the limits of human performance.

scholarly journals A computational observer model of spatial contrast sensitivity: Effects of photocurrent encoding, fixational eye movements and inference engine

2019 ◽  
Author(s):  
Nicolas P. Cottaris ◽  
Brian A. Wandell ◽  
Fred Rieke ◽  
David H. Brainard
Keyword(s):  
Eye Movements ◽  
Contrast Sensitivity ◽  
Cortical Neurons ◽  
Neural Population ◽  
Linear Filter ◽  
Response Dynamics ◽  
Translation Invariant ◽  
Fixational Eye Movements ◽  
Spatial Contrast Sensitivity ◽  
Observer Model

AbstractWe have recently shown that using the information carried by the mosaic of cone excitations of a stationary retina, the relative spatial contrast sensitivity function (CSF) of a computational observer has the same shape as a typical human subject. Absolute human sensitivity, however, is lower than the computational observer by a factor of 5 to 10. Here we model how additional known features of early vision affect spatial contrast sensitivity: fixational eye movements and the conversion of cone photopigment excitations to cone photocurrent responses. For a computational observer that uses a linear classifier applied to the responses of a stimulus-matched linear filter, fixational eye movements substantially change the shape of the spatial CSF, primarily by reducing sensitivity at spatial frequencies above 10 c/deg. For a computational observer that uses a translation-invariant calculation, in which decisions are based on the squared response of a quadrature-pair of linear filters, the CSF shape is little changed by eye movements, but there is a two-fold reduction in sensitivity. The noise and response dynamics of conversion of cone excitations into photocurrent introduce an additional two-fold sensitivity decrease. Hence, the combined effects of fixational eye movements and phototransduction bring the absolute sensitivity of the translation-invariant computational observer CSF to within a factor of 1 to 2 of the human CSF. We note that the human CSF depends on processing of the initial representation by many thalamic and cortical neurons, which are individually quite noisy. Our computational modeling suggests that the net effect of this noise on contrast-detection performance, when considered at the neural population level and behavioral level, is quite small: the inference mechanisms that determine the CSF, presumably in cortex, make efficient use of the information available from the cone photocurrents of the fixating eye.

Mechanistic modeling of vertebrate spatial contrast sensitivity and acuity at low luminance

2012 ◽  
Vol 29 (3) ◽  
pp. 169-181 ◽  
Author(s):  
JOHN R. JARVIS ◽  
CHRISTOPHER M. WATHES
Keyword(s):  
Contrast Sensitivity ◽  
Mechanistic Modeling ◽  
Spatial Integration ◽  
Modulation Transfer ◽  
Neural Noise ◽  
Light Levels ◽  
Low Luminance ◽  
Spatial Contrast Sensitivity ◽  
Neural Factors ◽  
Experimental Values

AbstractThe validity of the Barten theoretical model for describing the vertebrate spatial contrast sensitivity function (CSF) and acuity at scotopic light levels has been examined. Although this model (which has its basis in signal modulation transfer theory) can successfully describe vertebrate CSF, and its relation to underlying visual neurophysiology at photopic light levels, significant discrepancies between theory and experimental data have been found at scotopic levels. It is shown that in order to describe scotopic CSF, the theory must be modified to account for important mechanistic changes, which occur as cone vision switches to rod vision. These changes are divided into photon management factors [changes in optical performance (for a dilated pupil), quantum efficiency, receptor sampling] and neural factors (changes in spatial integration area, neural noise, and lateral inhibition in the retina). Predictions of both scotopic CSF and acuity obtained from the modified theory were found to be in good agreement with experimental values obtained from the human, macaque, cat, and owl monkey. The last two species have rod densities particularly suited for scotopic conditions.

Spatial Contrast Sensitivity of Migraine Patients Without Aura

Cephalalgia ◽  
2002 ◽  
Vol 22 (2) ◽  
pp. 142-145 ◽  
Author(s):  
K Benedek ◽  
J Tajti ◽  
M Janáky ◽  
L Vécsei ◽  
G Benedek
Keyword(s):  
Healthy Volunteers ◽  
Contrast Sensitivity ◽  
Migraine Without Aura ◽  
Marked Decrease ◽  
Primary Headache ◽  
Visual Pathway ◽  
Control Subjects ◽  
Spatial Frequencies ◽  
Spatial Contrast Sensitivity ◽  
Visual Disturbances

Visual disturbances are frequent symptoms in migraine. Since there is a possibility of separate damage in the magno- or parvo-cellular visual pathway in migraine patients, we performed a study including the measurement of static and dynamic spatial contrast sensitivity on 15 patients suffering from migraine without aura under photopic and scotopic conditions. Fifteen healthy volunteers without primary headache served as controls. The results revealed a marked decrease in contrast sensitivity at low spatial frequencies in the migraine patients. Spatial contrast sensitivity demonstrated some lateralization, as the sensitivity to low spatial frequencies obtained through separate eyes showed significantly larger side-differences in migraine patients than in control subjects. These findings suggest that the mechanisms responsible for vision at low spatial frequencies are impaired in migraine patients. This might indicate impaired function of the magnocellular pathways in this condition.

Sign in / Sign up

Export Citation Format

Share Document