It's a bit of a mystery why sometimes we're able to remember certain things and sometimes we're not. Scientists may have just figured out how to tell whether or not a memory is likely to be good, based on a little tiny part of your brain that calms down when it's ready to learn.
The blinky light in question is what shows up in a functional MRI (fMRI) scan when a specific part of your brain is active. The specific part of your brain in question (shown in the picture above) is called the parahippocampal cortex, since it's vital to your recognition of parachuting hippos.
What the parahippocampal cortex seems to do instead is somehow control whether your brain is prepared for an input of knowledge. Experiments conducted at MIT have shown that a person with an active parahippocampal cortex is significantly less likely to remember a visual scene. When the same area calms down, on the other hand, your brain gets much better at remembering things.
This is especially interesting because it suggests that whether you remember something depends on not just your brain's storage system, but also on how well your brain is prepared to access that system in the first place. In the short term, researchers think that they may be able to rig up an EEG headset to notify you (or your teacher) whether or not you're prepared to learn, and at some point in the future, it may be possible to selectively de-activate the parahippocampal cortex to make learning absolutely anything much easier.