Enhancing the dark side: Asymmetric gain of cone photoreceptors underpins their discrimination of visual scenes based on their skewness

Enhancing the darkside: Asymmetric gain of cone photoreceptors underpins discrimination of visual scenes based on their skewness

10.1101/2021.04.29.441966 ◽

2021 ◽

Author(s):

Matthew Yedutenko ◽

Marcus H.C. Howlett ◽

Maarten Kamermans

Keyword(s):

Impulse Response ◽

Integration Time ◽

Voltage Response ◽

Impulse Response Functions ◽

Response Functions ◽

Cone Photoreceptors ◽

Subtle Change ◽

Light Stimuli ◽

Visual Scenes ◽

Phototransduction Cascade

Psychophysical data indicates humans can discriminate visual scenes based on their skewness - the ratio of dark and bright patches within a visual scene. It was also shown that on a phenomenological level this skew discrimination is described by the so-called Blackshot mechanism, which accentuates strong negative contrasts within a scene. Here we demonstrate that the neuronal correlate of the Blackshot mechanism is the asymmetric gain of the cone phototransduction cascade, which is higher for strong negative contrasts than for strong positive contrasts. We recorded from goldfish cone photoreceptors and found that the asymmetry in the phototransduction gain leads to higher amplitude of the responses to negatively than to positively skewed light stimuli. This asymmetry in the amplitude was present in the photocurrent, voltage response and cone synaptic output. Additionally, we found that stimulus skewness leads to a subtle change in photoreceptor kinetics. For negatively skewed stimuli, the cone's impulse response functions peak later than for positively skewed stimulus. However, stimulus skewness does not affect the cone's overall integration time.

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Fungi from the Rhynie chert: a view from the dark side

Transactions of the Royal Society of Edinburgh Earth Sciences ◽

10.1017/s0263593303000324 ◽

2003 ◽

Vol 94 (04) ◽

pp. 457 ◽

Cited By ~ 4

Keyword(s):

Dark Side ◽

Rhynie Chert

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Analysis of 2D and 3D defects associated with precipitation of Cu in silicon

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010008866x ◽

1991 ◽

Vol 49 ◽

pp. 870-871

Author(s):

P.M. Rice ◽

MJ. Kim ◽

R.W. Carpenter

Keyword(s):

Colony Growth ◽

Dark Field ◽

Dark Side ◽

Silicide Phase ◽

Strain Fields ◽

Near Surface ◽

Unknown Composition ◽

Secondary Precipitates ◽

20 Nm ◽

2D And 3D

Extrinsic gettering of Cu on near-surface dislocations in Si has been the topic of recent investigation. It was shown that the Cu precipitated hetergeneously on dislocations as Cu silicide along with voids, and also with a secondary planar precipitate of unknown composition. Here we report the results of investigations of the sense of the strain fields about the large (~100 nm) silicide precipitates, and further analysis of the small (~10-20 nm) planar precipitates.Numerous dark field images were analyzed in accordance with Ashby and Brown's criteria for determining the sense of the strain fields about precipitates. While the situation is complicated by the presence of dislocations and secondary precipitates, micrographs like those shown in Fig. 1(a) and 1(b) tend to show anomalously wide strain fields with the dark side on the side of negative g, indicating the strain fields about the silicide precipitates are vacancy in nature. This is in conflict with information reported on the η'' phase (the Cu silicide phase presumed to precipitate within the bulk) whose interstitial strain field is considered responsible for the interstitial Si atoms which cause the bounding dislocation to expand during star colony growth.

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