**Core Concept**
Rivastigmine is a cholinesterase inhibitor used in the management of cognitive symptoms associated with Alzheimer's disease and Parkinson's disease. It works by increasing the concentration of acetylcholine in the brain, thereby improving memory and cognitive functions.

**Why the Correct Answer is Right**
Rivastigmine acts as a reversible cholinesterase inhibitor, meaning it temporarily blocks the action of acetylcholinesterase, the enzyme responsible for breaking down acetylcholine. By doing so, it increases the levels of acetylcholine in the synaptic cleft, which enhances cholinergic transmission and improves cognitive function. This mechanism is particularly beneficial in the treatment of Alzheimer's disease, where there is a reduction in cholinergic neurotransmission.

**Why Each Wrong Option is Incorrect**
**Option A:** Rivastigmine is not primarily used for the treatment of schizophrenia. While antipsychotics can cause cognitive impairment, rivastigmine is not indicated for this condition.
**Option B:** Rivastigmine is not a dopamine agonist, and its primary action is not on the dopaminergic system. It is used to enhance cholinergic function, not to stimulate dopaminergic receptors.
**Option C:** Rivastigmine is not a selective serotonin reuptake inhibitor (SSRI). SSRIs are used to treat depression and anxiety disorders, whereas rivastigmine is used to manage cognitive symptoms associated with neurodegenerative diseases.

**Clinical Pearl / High-Yield Fact**
Rivastigmine's efficacy in Alzheimer's disease is most pronounced in patients with moderate cognitive impairment. This is because the drug's mechanism of action is most beneficial when there is a significant reduction in cholinergic neurotransmission, which is typically observed in moderate stages of the disease.

**Correct Answer:** C. Parkinson's disease