Evidence against age-related enlargements of ganglion cell receptive field centers under scotopic conditions

Abstract

Age-related changes in the neural organization of spatial information are required to account for much of the senescent loss in human scotopic spatial vision, specifically declines in the high spatial frequency cut-off of the contrast sensitivity function and enlargements of the area over which there is complete spatial summation (Ricco's area). These results are consistent with hypothesized enlargements of ganglion cell receptive field centers during adulthood. This hypothesis was tested with 50 subjects (19-88 years) by measuring contrast thresholds for two low spatial frequency gratings (0.3 and 1.2 cycles per degree) at a series of scotopic mean illuminance levels. Contrast sensitivity increased with retinal illuminance and then reached a plateau, corresponding to the onset of Weber-like behavior. No age-related change in the light level associated with the onset of Weber-like behavior was found at either spatial frequency. This result is inconsistent with proposed age-related enlargements of ganglion cell receptive field centers under scotopic conditions.

Age-related changes in contrast gain related to the M and P pathways

“…The change in contrast gain may reflect a reorganization of retinal inputs to the ganglion cell layer or a reorganization of LGN and/or cortical cells to compensate for the loss in ganglion cell number. A reorganization of cortical cells has been proposed as an explanation for the increase in scotopic spatial summation (Schefrin et al, 1998) that cannot be accounted for by an age-related enlargement in the ganglion cell receptive field size (Schefrin, Hauser, & Werner, 2004). This functional change is analogous to the physiological enlargements of cortical cell receptive fields following the loss of the afferent inputs from a retinal laser burn (Chino, Kass, Smith, Langston, & Cheng, 1992; Gilbert & Wiesel, 1992).…”

Aging and vision

“…However psychophysical data have not supported this purported mechanism. Schefrin, Hauser, & Werner (2004) reasoned that if the retinal ganglion cell receptive field centers that receive rod input are increased in size in the older adult, then Weber-like behavior (e.g., contrast sensitivity increases monotonically with mean luminance level for a spatial target) should theoretically occur at a lower luminance level for older adults as compared to young adults. Yet younger and older adults displayed similar mean luminance levels corresponding to Weber-like behavior onset (Schefrin, Hauser & Werner, 2004), implying that ganglion cell receptive field centers do not get larger during aging.…”

Night vision in the elderly: consequences for seeing through a "blue filtering" intraocular lens

“…Figure 4 illustrates mean illuminance dependent changes in scotopic sensitivity for nine observers having a mean age of 75 years. 32 These data are from a larger study of 50 observers tested at 0.3 and 1.2 cpd after 30 minutes of dark adaptation. The stimuli were essentially the same as those used to obtain the data shown in figure 3, but the illuminance level was varied from absolute threshold to the Weber line where contrast sensitivity does not change with increases in retinal illuminance.…”