Signal coding in cockroach photoreceptors is tuned to dim environments

• Published in: Journal of neurophysiology 2012-11, Vol.108 (10), p.2641-2652
• Main Authors: Heimonen, K, Immonen, E-V, Frolov, R V, Salmela, I, Juusola, M, Vähäsöyrinki, M, Weckström, M
• Format: Article
• Language: English
• Subjects: Action Potentials; Animals; Contrast Sensitivity; Dark Adaptation - physiology; Darkness; Periplaneta; Photons; Photoreceptor Cells, Invertebrate - physiology
• ISSN: 0022-3077; 1522-1598
• DOI: 10.1152/jn.00588.2012

In dim light, scarcity of photons typically leads to poor vision. Nonetheless, many animals show visually guided behavior with dim environments. We investigated the signaling properties of photoreceptors of the dark active cockroach (Periplaneta americana) using intracellular and whole-cell patch-clamp recordings to determine whether they show selective functional adaptations to dark. Expectedly, dark-adapted photoreceptors generated large and slow responses to single photons. However, when light adapted, responses of both phototransduction and the nontransductive membrane to white noise (WN)-modulated stimuli remained slow with corner frequencies ~20 Hz. This promotes temporal integration of light inputs and maintains high sensitivity of vision. Adaptive changes in dynamics were limited to dim conditions. Characteristically, both step and frequency responses stayed effectively unchanged for intensities >1,000 photons/s/photoreceptor. A signal-to-noise ratio (SNR) of the light responses was transiently higher at frequencies