BOOK 4 // CHAPTER 30

The Hijack (Addiction)

Slaves to the molecule.
The Puppet
Fig 30.1: The Strings. Agency is surrendered to the impulse.

The Hijack Circuit

Addiction is a disease of the Mesolimbic Pathway (The Reward Circuit).

It begins in the VTA (Ventral Tegmental Area), which pumps dopamine to the Nucleus Accumbens (NAc).

  • Normal Function: "This berry is sweet. Remember where we found it. Do it again."
Addicted Function: The drug floods the system with 100x the normal dopamine signal. The brain interprets this as: "This is more important than food. This is more important than mating. This is the new survival priority."*

The Tolerance Trap (D2 Downregulation)

The brain seeks homeostasis. When flooded with dopamine, it protects itself by removing dopamine receptors (D2).

This is Tolerance.

You now need more of the substance just to feel normal.

Simultaneously, the Anti-Reward System (mediated by Dynorphin) activates. The "high" gets shorter (A-Process), and the "crash" gets deeper and longer (B-Process). This is the Opponent-Process Theory.

The Ghost in the DNA: DeltaFosB

Chronic use accumulates a unique protein called DeltaFosB in the Medium Spiny Neurons of the Nucleus Accumbens.

Unlike short-term proteins, DeltaFosB is stable. It builds up like plaque.

It acts as a genetic switch, rewriting neural sensitivity. Even years after sobriety, high DeltaFosB levels leave the brain primed for relapse.

Glutamate and the Relapse Trigger

Dopamine drives the seeking, but Glutamate drives the memory.

Addiction changes how the brain learns. Cues (a lighter, a street corner, a smell) trigger a massive flood of Glutamate from the PFC to the Nucleus Accumbens.

This helps explain Relapse: It is an excitotoxic storm of "craving memory" that overrides conscious control.

The Inheritance of Perspective

We evolved to tirelessly pursue scarce resources (sugar, fat). We now live in a world of infinite abundance. We are not bad people; we are Stone Age machines engaging with super-stimuli we were never designed to process.

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[!NOTE]
Clinical Context: The Path of Recovery
Because addiction involves structural brain changes (D2 downregulation, DeltaFosB accumulation), "willpower" is often insufficient.

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1. Harm Reduction: Safety is the priority. Keeping the patient alive until the brain can heal.
2. MAT (Medication-Assisted Treatment): Uses agonists/antagonists (e.g., Buprenorphine, Naltrexone) to stabilize the receptor systems so therapy can begin.
3. Glutamate Modulation: Emerging therapies (N-acetylcysteine) target the glutamate system to reduce cue-induced craving.