Pupil response components: studies in patients with Parinaud's syndrome

Abstract

In addition to light flux changes, it is well established that other stimulus attributes such as colour, spatial structure or movement can also cause a transient constriction of the pupil, even when the onset of the stimulus causes a net decrease in light flux level on the retina. Although experimental findings in human subjects with postgeniculate lesions show that the generation of such responses must involve the processing of stimulus attributes in extrastriate areas of the cortex, little is known about the site of integration of cortical signals into the pupillomotor pathway. We have investigated how visual performance and the various components of the pupil response have been affected in subjects with damage to the dorsal midbrain (Parinaud's syndrome). The results show that the probable destruction of the olivary pretectal nucleus and the nucleus of the optic tract has little or no effect on pupil grating or pupil colour responses. The light reflex response, on the other hand, is virtually abolished, with only a small residual component that is similar to the pupil grating response and may not require an afferent projection to the midbrain. These new findings suggest that the site of integration of cortical signals in relation to pupil colour and grating responses and the generation of sleepiness-induced oscillations of the pupil do not rely on the normal functioning of pretectal nuclei that are involved in the light reflex response.

Quantitative Assessment of the Canine Pupillary Light Reflex

“…Some disorders can affect the neural pathways involved in regulating pupil size without altering the image-forming and -processing functions of the retina and visual system. [10][11][12][13][14][15] In these cases, when retinal function is normal as determined by ERG recordings, PLR abnormalities can be attributed to ipRCG dysfunction or neurological pathology outside of the retina. Alternatively, some diseases may affect the image-forming functions of the retina while the components of the PLR mediated by the ipRGCs are preserved.…”

“…9 However, pupillography is not limited to detecting retinal deficits but has also proved an indicator of autonomic dysfunction. [10][11][12][13][14][15] Canine homologues have the potential to serve as important models of human hereditary retinal and neurological diseases. Canine and human retinas are very similar with respect to both anatomy and physiology.…”

Pupil dynamics during bistable motion perception

“…Well-studied examples of pupil dilations in response to non-sensory processing comprise cognitive load (Beatty & Wagoner, 1978;Kahneman & Beatty, 1966), attention (Beatty, 1977), stimulus probability (Reinhard & Lachnit, 2002), and emotional factors (Partala & Surakka, 2003). In addition, changes of pupil size have been observed for specific visual computations supposed to involve the visual cortex, like the transition from incoherent to coherent motion (Sahraie & Barbur, 1997), color perception (Barbur, Weiskrantz, & Harlow, 1999;Wilhelm, Wilhelm, Moro, & Barbur, 2002), or the processing of faces (Conway, Jones, DeBruine, Little, & Sahraie, 2008), raising the possibility that pupil dynamics reflects some aspects of cortical processing.…”

Cortical hyperexcitability and sensitivity to discomfort glare

“…In agreement with this hypothesis, it has been found that discomfort ratings of different colored gratings correlate positively with the cortical haemodynamic response, as measured with near infrared spectroscopy (Haigh et al, 2013). High contrast, achromatic or colored gratings also cause a constriction of the pupil which has been linked to the level of cortical activity generated since these pupil response components remain even in the absence of damaged subcortical projections that abolish the light reflex response (Barbur, 2004;Wilhelm et al, 2002). In the case of discomfort glare where high luminance sources are often used, hyperexcitability or saturation of a set of neurons is likely to occur; and as suggested by Wilkins and others (Haigh et al, 2013;Wilkins et al, 1984), the discomfort may be a homeostatic response, the purpose of which is to decrease the metabolic load.…”