Final answer:
Parvocellula-X ON cells are neurons that increase their firing rate when light is turned on, with this activity ceasing when the light is turned off. Experiments with light-activated devices in rat neurons have shown different protein expressions with varying light frequencies. Bioluminescence in organisms like Gonyaulax also showcases light-responsive biological processes.
Step-by-step explanation:
Parvocellula-X ON cells are a type of neuron that respond to light. When a light is turned on, there is an increase in firing rate in these cells. The neuron remains active/on until the light goes off, indicating a connection to light-responsive protein expression within the neuron. The use of varying light frequencies, such as 1 Hz or 100 Hz, can induce different types of protein expression, as evidenced by experiments with optically activated devices in rats. Furthermore, the phenomenon of bioluminescence in organisms like Gonyaulax demonstrates another aspect of light responsiveness in biology, with these organisms displaying a 24-hour periodicity in light emission and additional triggers such as agitation as seen in species whose luminescence is triggered by the motion of breaking waves.