The Pupillary Response to Color and Luminance Variant Multifocal Stimuli

Abstract

PURPOSE. We are developing multifocal pupillographic objective perimetry (mfPOP) to assess localized changes in function within visual pathways. In this study, we investigate novel mfPOP stimuli designed to target neural components from either or both the sub-cortical pupillary luminance response and the cortically driven color response.METHODS. Pupillary responses of 12 subjects were recorded to eight mfPOP stimulus variants (protocols). Forty-eight visual field test-regions (24/eye) were stimulated concurrently with uncorrelated sequences of either high or low luminancecontrast, luminance-plus color-contrast, or equiluminant colorexchange stimuli. Stimulus pulses were of 50 ms duration and were presented at mean intervals of 4 seconds/region. Test durations were 4 or 8 minutes; therefore, estimated responses were derived from 60 or 120 stimulus presentations to each test region.RESULTS. Pupillary response amplitudes were more influenced by luminance-contrast than the color-contrast of stimuli; response delays, however, were more closely linked to the proportion of color-versus luminance-contrast in each protocol. Significant differences (P < 0.05) in amplitudes but not delays were present between all three high luminancecontrast protocols and a low luminance-contrast luminance protocol, regardless of color content. The reverse pattern was observed between the equiluminant color exchange protocol and this same low luminance-contrast luminance protocol. Only the low luminance-contrast plus color exchange protocol differed significantly from the low luminance-contrast luminance protocol in both measures.CONCLUSIONS. Two protocols, utilizing low and high luminancecontrast plus color exchange, were identified as likely to incorporate both cortical and subcortical response components, and were deemed potential candidates for further investigation in clinical studies. (Invest Ophthalmol Vis Sci.

Comparing multifocal pupillographic objective perimetry (mfPOP) and multifocal visual evoked potentials (mfVEP) in retinal diseases

“…Previous reports of mfVEP responses from occipital electrodes in patients with T2D showed only significant implicit time delays in the absence of retinopathy; however those delays correlated poorly with regions of loss on mfERG27. Using mfPOP stimuli we have recently confirmed earlier literature2128 showing that the pupillary system can be substantially driven by the visual cortex29, especially when using the transient stimuli of mfPOP24. Given those findings, and the brain lesion studies indicting substantial involvement of the extra-striate cortex in pupillary responses of primates and humans2230, we here compare the mfVEP responses from electrodes covering the occipital cortex, and surrounding electrodes that are more biased to extra-striate cortex, for any sign of the hypersensitivities in the subjects from those two studies.…”

“…1B,C,D). Anatomically the pupillary system receives significant input from the extra-striate cortex21, and we have demonstrated cortical input to the responses obtained from the types of transient mfPOP stimuli used here2429. Thus it seems plausible that observed hypersensitivities in mfPOP derive from extra-striate input.…”

Pupil Response and the Subliminal Mere Exposure Effect

“…Pupil response is modulated by patterned stimuli that do not change overall ambient light levels [8], [26], [27]. During pupil measurement, we presented different types of visual stimuli during a single exposure: a fixation mark, a visual pattern (Bengali characters or line drawings), and a masking pattern (Figure 2).…”

Pupillary behavior in relation to wavelength and age

“…Thus, an imbalance between them can result in a pupillary light reflex defect which, in turn, may be used as an indicator of certain diseases (Fotiou et al, 2007b; Jain et al, 2011) and drug consumption (Monticelli et al, 2009; Lobato-Rincón et al, 2013). Additionally, pupil pathways are wired up to respond specifically to different features of a visual stimulus, such as coherent motion (Sahraie and Barbur, 1997), color (Young et al, 1993; Tsujimura et al, 2006), variations in the levels of contrast, as well as frequency and luminance of a light stimulus (Link et al, 2006; Carle et al, 2013). …”