In humans, the Alzheimer disease is linked with the deficiency of

The correct option is acetylcholine.

Alzheimer's disease is a progressive neurodegenerative disorder characterized by cognitive decline, memory loss, and a decrease in functional abilities. One of the primary pathophysiological hallmarks of this disease is the degeneration of cholinergic neurons, particularly in the basal forebrain region of the brain.

These cholinergic neurons are responsible for producing and releasing the neurotransmitter acetylcholine. Acetylcholine plays a critical role in the central nervous system, specifically in processes related to learning, memory formation, attention, and general cognitive function.

The loss of these neurons leads to a significant deficiency in acetylcholine levels in the cerebral cortex and hippocampus. This deficiency impairs synaptic transmission and is directly linked to the cognitive deficits and memory impairment observed in individuals with Alzheimer's disease.

For comparison:
- Dopamine deficiency is primarily associated with Parkinson's disease.
- Glutamic acid (glutamate) is the primary excitatory neurotransmitter; while its regulation is altered in Alzheimer's (leading to excitotoxicity), the disease is classically defined by the primary deficiency of acetylcholine.
- Gamma Amino Butyric Acid (GABA) is the main inhibitory neurotransmitter, and its deficiency is linked to conditions like anxiety disorders and epilepsy, rather than being the primary marker for Alzheimer's disease.