Introduction to Amnesia

Amnesia - any loss of memory

Psychological vs Physiological factors: 

• Organic amnesia
• Infantile Amnesia
• Repressive amnesia

Temporal factors:

• Retrograde amnesia
• Anterograde amnesia

Causes of Amnesia

• Stroke
• Closed head injury
• Herpes simplex encephalitis
• Anoxia
• Korsokoffs syndrome, due to chronic alcohol abuse

Major brain structures involved

• Diencephalon (subcortical region) - Korsakoffs
• Medial temporal lone (cortical region) - due to anoxia

 

Summary

• STM appears relatively normal in many cases of amnesia, but exceptions exist
• LTM can be divided into implicit vs explicit memory
• Amnesic patients appear to show normal performance on implicit tests
• Amnesic patients are impaired on explicit tests

Aggleton and Brown (1999)

2 distinct memory systems originating within the medial temporal lobe

- Hippocampal system - subserves process of recollection (remember)

- Perirhinal system - subserves process of familiarity (know)

Recognition memory based either on:

- Remembering - contextual recollection

- Knowing - familiarity, no contextual detail

Key hypotheses: 

damage to both systems - Impaired R + F

Damage to hippocampus only - impaired R only