How do drugs affect the brain?

Dissociatives cause feelings of detachment from reality

Question: How do drugs affect the brain?
Position1 of 3›: Hallucinogens alter perception and cause hallucinations
Argument1 of 2›: Dissociatives cause feelings of detachment from reality

Dissociatives such as ketamine distort perceptions and cause a sense of dissociation from the self.

The argument

Dissociative drugs affect the brain in much the same way as the related class of hallucinogens categorized as psychedelics. Both dissociatives and psychedelics interact with specific receptor molecules, causing short-term changes to consciousness and perception by virtue of their impact on neurochemistry. Whereas most major psychedelics accomplish these effects through action on serotonin receptors in the brain, dissociatives may act on other receptors such as NMDA receptors, thus causing different mental and perceptual states than psychedelics. In particular, dissociatives are associated with creating feelings of depersonalization, during which the person feels detached from their environment and self. This perceptual change is known as dissociation, which gives the dissociative drug category its name.

Premises

[P1]Dissociatives, like psychedelic hallucinogens, alter consciousness and perception by acting on the brain's receptor molecules. [P2] Unlike psychedelics that act on serotonin receptors, dissociatives act on others like NMDA receptors, producing different states. [P3] These produce depersonalization, in which a person feels detached from their environment and self. [C] Therefore, because dissociatives cause feelings of detachment from reality, hallucinogens alter perception.

Counter-arguments

A rebuttal on classificatory grounds is that many pharmacologists treat dissociatives as a category distinct from the classic (psychedelic) hallucinogens, precisely because their mechanism — NMDA-receptor antagonism rather than serotonergic action — and their characteristic effects differ. Citing dissociatives to support the claim that "hallucinogens alter perception" therefore leans on a grouping that is itself contested. Critics add that the signature dissociative effect, depersonalisation or detachment from self, is arguably a different phenomenon from the altered perception and hallucination the position names. Detachment from reality is not the same as seeing what is not there, so the example fits the heading only loosely.

Rejecting the premises

[Rejecting P1] Many pharmacologists classify dissociatives as a separate category from classic hallucinogens because their NMDA mechanism differs, so grouping them under "hallucinogens" is itself contested. [Rejecting P3] Depersonalisation (detachment from self) is arguably distinct from the altered perception and hallucination the position names, so dissociative effects do not straightforwardly evidence that claim.