Explain "opponent processes" to me, please

I was reading the above link on Opponent Processes so I could understand habituation better. I was fine for the first two sentences but could not understand the two following it. I’ve bolded the confusing parts below.

“Opponent processes are observable in neuro impulses (Garbor wavelets), similar to qualia in philosophy. These include color illusions of seeing an opposite color after habituation, physiological homeostasis reactions for temperature, oxygen, food, and stimuluation control. Drug addiction is best understood as being due to the modulation of a homeostatis into a positive and negative phase. Any stimulus, drug, or behavior will lose its strength due to learned habituation, but the opponent reaction to the original drug remains strong. In terms of drugs this means that eventually, people who started to take heroin to experience pleasure will be taking it to feel neutral.”

I understand the gist of the last sentence but without fully understanding the prior two sentences before it, I can’t accept it.

Um, somebdy help me out by translating that?

I’m no expert on neuroscience, but the part about drugs is saying this :

Before you take drugs, you’re pretty much in balance (homeostasis[sup]*[/sup]). Things feel normal.

“modulation into positive and negative phase” - once you start taking drugs, you have periods of ‘highs’ followed by ‘lows’. This theory seems to suggest that taking drugs is like inducing bipolar disorder.

losing stimulus due to positive habituation - over time, the ‘high’ weakens while the low stays the same. Instead of riding a roller coaster up and down, you’ve only got the down parts. The ‘high’ becomes merely the same level as what ‘normal’ used to be.

What doesn’t follow from this (at least not logically) is whether the time after the low would not return to previous ‘neutral’. Unless the drug is now taken merely to shorten the duration of the low period, which I suppose is plausible.

With respect to the other parts, qualia are the ‘feelings’ we get due to perceptions. If, for instance, we both say, “this is red”, are we ‘experiencing’ the same thing? The qualia is the ‘internal’ experience that would cause us to say, “this is red”. Whether qualia even exist is, like most things in philosophy, a matter of debate.

The sort of thing they’re talking about in terms of stimulus is this type of experiment : Put one hand in ice water, and the other in hot water. Then put them both in tepid water. The water will feel hot to the one and cold to the other, even though the measured temperature is the same.

[sup]*[/sup]Homeostasis seems to usually refer to the balance that results from a dynamic equilibrium. Things may be changing but stay the same ‘holistically’. If, for instance, the number of Americans moving to Canada = Canadians moving to America, the populations of each country stay the same, despite all the moving around.