The interaction between the ERG responses to sinusoidal modulation and flashes in mice

To study the interaction between responses to a sinusoidal modulation and a flash in the mouse ERG.

We recorded responses to pulses on a 1 Hz sinewave background (Pulse on Sine Stimuli: PoS) in mice. Flashes were presented at 8 different temporal phases relative to the sinewave background. Recordings were performed for three different luminance levels with equal ratio between flash intensity and sinewave mean luminance. Control recordings with flashes on steady background, 1 Hz sinewave without flashes, and noise without modulation were recorded with the same mean luminances.

The flash responses to the PoS stimuli depended strongly on the phase of the flash relative to the sinewave background. The flash response was small, when the instantaneous luminance of the sinewave was large. The flash response was large, when the sinewave luminance was small. The effect decreased with increasing mean luminance. The response to the sinewave background also depended on the phase of flash presentation. The sinewave response was small when the flash response was large for all luminances. The responses to the PoS stimuli could be described with a linear model that assumes that the responses to the combined stimuli are a scaled addition of the flash responses on a steady background and of the responses to the sinewave without a flash. The obtained scaling factors for both flash and sinewave responses depended on their relative phase.

The responses to flashes and modulating background influence each other in a complex manner. This is in contrast to responses in human observers, where only the flash response is influenced by the flash phase relative to the sinewave background. We propose that mouse responses are more sluggish and are integrated over extended periods, resulting in complex mutual interactions between responses to flashes and backgrounds.