Final answer:
In someone with depression, decreased levels of dopamine, norepinephrine, and serotonin are expected, but acetylcholine levels are not typically associated with depression. Antidepressants aim to correct these imbalances.
Step-by-step explanation:
In the brain of someone with depression, one typically finds decreased levels of certain neurotransmitters that are associated with mood regulation. Among the neurotransmitters often implicated in depression are dopamine, norepinephrine (also known as noradrenaline), and serotonin. Acetylcholine, although a critical neurotransmitter in many functions, is not commonly associated with depression in the same way as the aforementioned neurotransmitters. Therefore, while decreased levels of dopamine, norepinephrine, and serotonin are expected in cases of depression, acetylcholine does not follow this pattern.
Research suggests that serotonin plays a significant role in depression, and medications such as selective serotonin reuptake inhibitors (SSRIs) aim to increase serotonin levels in the brain. Similarly, other classes of antidepressants like MAO inhibitors and norepinephrine-dopamine reuptake inhibitors also work to correct imbalances in these neurotransmitters. The complex interplay of these chemicals is a key area of study for developing effective treatments for depressive disorders.