Phenomenology is the study of what happens between your outer skin and your inner brain. We don't directly sense objects in the world, but we only get neuro-electric stimuli from our sense organs.

Consider a sensory nerve ending such as a retina cell in your eye. When light strikes it, the retina cell responds by sending a neural impulse into your brain. What information does that neural impulse carry? In other words, what can you (or your brain) know based on this neural impulse? I think there are only three pieces of information:

  1. Whether or not the sensory nerve fired off its impulse

    A computer circuit can either have voltage or not, and this is an on-or-off kind of thing. It's digital and binary, like 0 or 1. In the same way, an individual retina cell can fire off its stimulus or not. It's true that biological neurons fire in different ways - fast or slow, continuously or intermittently etc. - but this complexity is not an essential part of what makes people intelligent or sentient. We can build a fully functional computer model of the brain using simple on-or-off neurons. Perhaps we'll just need more neurons than a biological brain needs.

  2. Where in your body that sensory nerve is

    Each sensory nerve ending can send a stimulus along a particular nerve pathway that arrives in a particular part of the brain. That's the only way your brain knows where the stimulus came from. It's the only way you can tell the difference between a light shining in your eye and something hot burning your foot. You know the difference because the stimulus arrives at a different part of your brain.

  3. When the sensory nerve fired

    The brain must have some means of knowing about the passage of time. A biological brain probably can't measure time systematically, but the important thing is just to know whether one stimulus arrived before or after another one. The memory must be organized in some kind of temporal sequence, at least the short-term memory.