What happens in your brain when you get Alzheimer's disease?

Updated

Alzheimer's disease starts in the entorhinal cortex and hippocampus, destroying memory formation, then spreads to temporal, parietal, and prefrontal cortices, causing language problems, spatial disorientation, and executive dysfunction.

Entorhinal Cortex, Hippocampus, Temporal Cortex, Parietal Cortex, Prefrontal Cortex lit up on the Brain Atlas 3D brain: what happens in your brain when you get Alzheimer's disease
Figure. The brain regions that light up when you get Alzheimer's disease, in order: Entorhinal Cortex (first hit), then Hippocampus (memory fails), then Temporal Cortex (word-finding trouble), then Parietal Cortex (getting lost), then Prefrontal Cortex (executive decline).

Watch it light up on the 3D brain

Brain regions that light up

OrderRegionWhat it does here
1Entorhinal CortexTau tangles and neuronal loss begin in the entorhinal cortex, the gateway to the hippocampus.
2HippocampusThe hippocampus degenerates, impairing the formation of new memories.
3Temporal CortexSpread to the temporal cortex disrupts semantic memory and language.
4Parietal CortexParietal involvement causes visuospatial deficits and apraxia.
5Prefrontal CortexPrefrontal cortex damage impairs judgment, planning, and personality.

1. Entorhinal Cortex: first hit

Step 1 of what happens in your brain when you get Alzheimer's disease: Entorhinal Cortex lit on the Brain Atlas 3D brain
Figure 1. Entorhinal Cortex, first hit: Tau tangles and neuronal loss begin in the entorhinal cortex, the gateway to the hippocampus.

The entorhinal cortex provides the main input to the hippocampus and is critical for spatial navigation and memory consolidation. In Alzheimer's, it is one of the earliest sites of neurofibrillary tangle formation, disrupting the flow of information into the memory system and causing subtle spatial disorientation before obvious memory loss.

2. Hippocampus: memory fails

Step 2 of what happens in your brain when you get Alzheimer's disease: Entorhinal Cortex, Hippocampus lit on the Brain Atlas 3D brain
Figure 2. Hippocampus, memory fails: The hippocampus degenerates, impairing the formation of new memories.

The hippocampus is essential for converting short-term memories into long-term storage. As neurons die and synapses are lost, patients struggle to remember recent events while older memories may remain relatively intact initially. This is the hallmark amnesia of early Alzheimer's.

3. Temporal Cortex: word-finding trouble

Step 3 of what happens in your brain when you get Alzheimer's disease: Entorhinal Cortex, Hippocampus, Temporal Cortex lit on the Brain Atlas 3D brain
Figure 3. Temporal Cortex, word-finding trouble: Spread to the temporal cortex disrupts semantic memory and language.

The temporal cortex houses semantic knowledge and object recognition. As pathology spreads here, patients develop anomia (difficulty naming objects) and impaired comprehension. This reflects the breakdown of the stored knowledge about words and concepts.

4. Parietal Cortex: getting lost

Step 4 of what happens in your brain when you get Alzheimer's disease: Entorhinal Cortex, Hippocampus, Temporal Cortex, Parietal Cortex lit on the Brain Atlas 3D brain
Figure 4. Parietal Cortex, getting lost: Parietal involvement causes visuospatial deficits and apraxia.

The parietal cortex integrates sensory information for spatial awareness and coordinated movement. Degeneration here leads to getting lost in familiar places, difficulty with tasks like dressing (apraxia), and problems with calculations, contributing to the disorientation seen in moderate Alzheimer's.

5. Prefrontal Cortex: executive decline

Step 5 of what happens in your brain when you get Alzheimer's disease: Entorhinal Cortex, Hippocampus, Temporal Cortex, Parietal Cortex, Prefrontal Cortex lit on the Brain Atlas 3D brain
Figure 5. Prefrontal Cortex, executive decline: Prefrontal cortex damage impairs judgment, planning, and personality.

The prefrontal cortex manages executive functions such as decision-making, working memory, and social behavior. Late-stage Alzheimer's involvement causes poor judgment, apathy, and personality changes, reducing the ability to live independently.

Good to know

  • Alzheimer's disease is defined by the accumulation of amyloid-beta plaques outside neurons and tau tangles inside neurons.
  • The hippocampus shows marked atrophy on MRI, correl with memory impairment.
  • Alzheimer's disease is the most common cause of dementia.

Alzheimer's vs. normal aging

In normal aging, occasional forgetfulness and slower recall are common, but the hippocampus and entorhinal cortex remain relatively intact. In Alzheimer's, progressive neurodegeneration in these regions causes severe memory loss and functional decline that interferes with daily life.

Test yourself

  1. Which brain region is typically the first to show tau pathology in Alzheimer's disease?

  2. Damage to the hippocampus in Alzheimer's primarily causes which symptom?

  3. How does Alzheimer's differ from normal age-related memory decline?

0 of 3 answered · 0 correct

Simplified: many regions work together at once, and this shows the main players in the order they act. For learning only, not medical advice.