Responses to spatial contrast in the mouse suprachiasmatic nuclei (SCN)

Josh Mouland, Adam R Stinchcombe, Daniel B. Forger, Timothy Brown, Robert Lucas

Research output: Contribution to journalArticlepeer-review

Abstract

A direct retinal projection targets the suprachiasmatic nucleus (SCN) (an important hypothalamic control center). The accepted function of this projection is to convey information about ambient light (irradiance) to synchronize the SCN’s endogenous circadian clock with local time and drive the diurnal variations in physiology and behavior [1; 2; 3 ; 4]. Here, we report that it also renders the SCN responsive to visual images. We map spatial receptive fields (RFs) for SCN neurons and find that only a minority are excited (or inhibited) by light from across the scene as expected for irradiance detectors. The most commonly encountered units have RFs with small excitatory centers, combined with very extensive inhibitory surrounds that reduce their sensitivity to global changes in light in favor of responses to spatial patterns. Other units have larger excitatory RF centers, but these always cover a coherent region of visual space, implying visuotopic order at the single-unit level. Approximately 75% of light-responsive SCN units modulate their firing according to simple spatial patterns (drifting or inverting gratings) without changes in irradiance. The time-averaged firing rate of the SCN is modestly increased under these conditions, but including spatial contrast did not significantly alter the circadian phase resetting efficiency of light. Our data indicate that the SCN contains information about irradiance and spatial patterns. This newly appreciated sensory capacity provides a mechanism by which behavioral and physiological systems downstream of the SCN could respond to visual images
Original languageEnglish
Pages (from-to)1633-1640
JournalCurrent Biology
Volume27
Issue number11
Early online date18 May 2017
DOIs
Publication statusPublished - 18 May 2017

Keywords

  • Suprachiasmatic nucleus
  • Electrophysiology
  • Circadian
  • spatial patterns
  • Receptive fields
  • Locomotor activity
  • clock resetting
  • spatiotemporal tuning

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