Abstract
BackgroundThe olivary pretectal nucleus (OPN) is a small midbrain structure responsible for pupil constriction in response to eye illumination. Previous electrophysiological studies have shown that OPN neurons code light intensity levels and therefore are called luminance detectors. Recently, we described an additional population of OPN neurons, characterized by a slow rhythmic pattern of action potentials in light-on conditions. Rhythmic patterns generated by these cells last for a period of approximately 2 minutes.MethodologyTo answer whether oscillatory OPN cells are light responsive and whether oscillatory activity depends on retinal afferents, we performed in vivo electrophysiology experiments on urethane anaesthetized Wistar rats. Extracellular recordings were combined with changes in light conditions (light-dark-light transitions), brief light stimulations of the contralateral eye (diverse illuminances) or intraocular injections of tetrodotoxin (TTX).ConclusionsWe found that oscillatory neurons were able to fire rhythmically in darkness and were responsive to eye illumination in a manner resembling that of luminance detectors. Their firing rate increased together with the strength of the light stimulation. In addition, during the train of light pulses, we observed two profiles of responses: oscillation-preserving and oscillation-disrupting, which occurred during low- and high-illuminance stimuli presentation respectively. Moreover, we have shown that contralateral retina inactivation eliminated oscillation and significantly reduced the firing rate of oscillatory cells. These results suggest that contralateral retinal innervation is crucial for the generation of an oscillatory pattern in addition to its role in driving responses to visual stimuli.
Highlights
The pretectal complex is part of the subcortical visual system located in the midbrain
We found that oscillatory neurons were able to fire rhythmically in darkness and were responsive to eye illumination in a manner resembling that of luminance detectors
The unifying electrophysiological feature of the recorded cells was their propensity to generate rhythmic firing with a period of approximately two minutes (Fig. 1B and 1D). This was reported in our previous study [19], and is referred to later in the text as slow oscillatory activity (SOA)
Summary
The pretectal complex is part of the subcortical visual system located in the midbrain It is divided into five nuclei [1], among which is the olivary pretectal nucleus (OPN). The OPN receives dense retinal innervation [2,3] and is the first nucleus in the arch of the pupillary light reflex [4]. Neurons within this nucleus can be characterized by low a firing rate in darkness and a tonic ON response following eye illumination. The light-induced response lasts for the duration of the stimulus, and its amplitude is positively correlated with light intensity. Rhythmic patterns generated by these cells last for a period of approximately 2 minutes
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.