- Poster presentation
- Open Access
Neuronal nonlinearity explains greater visual spatial resolution for dark than for light stimuli
© Kremkow et al; licensee BioMed Central Ltd. 2013
- Published: 8 July 2013
- Receptive Field
- Local Field Potential
- Gray Background
- Neuronal Mechanism
- Background Luminance
We hypothesized that a nonlinear encoding of luminance increments and decrements could explain these differences. We found that OFF cells in LGN increase their responses roughly linearly (Figure 1B, right) with luminance decrements, independent of the background luminance (luminance half-saturation = L50; LGN OFF L50 light/gray = 0.99, p = 0.9; V1 OFF L50 light/gray = 1.03, p = 0.2). In marked contrast, ON-center cells saturate their responses with small increases in luminance (Figure 1A, top-left) and require bright backgrounds to approach the linearity of the OFF-center cells (Figure 1A, bottom-left; LGN ON L50 dark/gray = 0.28, p < 0.001; V1 ON L50 dark/gray = 0.3, p < 0.001). Although the integration of lights becomes more linear as the luminance of the background increases, ON responses still saturate more than OFF responses on gray backgrounds (V1 L50 darks/lights = 1.25, p < 0.001). Similar differences in response linearity could be demonstrated in recordings from local field potentials in awake primates.
Consistent with our hypothesis, we show that a simple computational model based on the ON-channel nonlinearity can explain the larger receptive fields and lower spatial resolution of ON cells, the differences in human spatial resolution between darks than lights, the differences in the size of ON and OFF dendritic fields from retinal ganglion cells and the recently demonstrated OFF dominance in visual cortex (larger number of OFF- than ON-dominated cortical neurons). These results demonstrate a fundamental difference in processing between ON and OFF channels, which could have major implications in visual perception and cortical development.
This work was supported by: NIH Grant EY02067901, EY05253 and DFG Research Fellowship to Jens Kremkow
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