Memory

Amnesia

Amnesia is a partial or total inability to recall past experiences and events. It can arise from a psychological (psychogenic) process, such as extreme trauma, or from a physical (organic) disturbance of the brain, and the pattern of what is and isn't remembered often gives useful clues as to which is more likely.

Before concluding that a memory gap is pathological, it is worth remembering that normal forgetting is itself expected: unrehearsed memories fade over time, and 'interference' between memories is a normal process too — older memories can make new learning harder (proactive interference), and newly learned material can make older memories harder to retrieve (retroactive interference).

Recognition features

• A partial or total gap in the ability to recall past experiences or events
• May affect a discrete period of time, a specific category of memory, or be more pervasive
• The pattern of loss (sudden versus gradual, circumscribed versus diffuse, personal identity affected or spared) is itself diagnostically informative
• Can arise from psychological causes, physical brain disturbance, or ordinary processes such as decay or interference, which should always be considered first

Eliciting it at interview

• Establish the exact boundaries of the gap: what is the last thing clearly remembered, and what is the first thing remembered afterwards
• Ask specifically whether personal identity (name, address, basic biography) is affected, since this points strongly toward a psychogenic rather than organic process
• Take a careful history of onset, since a sudden onset in the context of severe stress points one way, while a gradual, progressive pattern points another

Distinguishing features

• Differs from paramnesia, in which memory is not simply lost but actively distorted or falsified
• A psychogenic (dissociative) amnesia typically spares complex learned skills and social competence despite affecting personal identity, whereas organic amnesias more often spare identity while affecting the ability to learn or retrieve specific facts and events
• Normal forgetting, decay, and interference should always be considered and excluded before concluding a memory gap is pathological

Common misconceptions

• That memory works like a video recording that either plays back accurately or is simply missing; even intact memory is reconstructive and imperfect, which matters most in contexts like legal testimony
• That any reported memory gap indicates significant pathology; ordinary forgetting and interference between memories are expected and common

Related phenomena

Dissociative Amnesia · Catathymic Amnesia · Organic Amnesia · Anxiety Amnesia · Paramnesia (Distortion of Memory)

Practice this

Following a head injury, a patient is simply unable to recall anything from the several hours immediately surrounding the accident. She does not offer any account, false or otherwise, of that period — she is straightforwardly aware that the memory is missing. What is this? · A patient with dementia cannot recall attending her granddaughter's wedding last month, but when asked about it, she confidently and in detail describes a different wedding — one that, on checking, never took place — with no apparent awareness that anything is wrong. Before revealing the answer: is this simply amnesia? · A patient has a disturbance affecting a period of personal memory. Before revealing the answer, decide what distinguishes amnesia from paramnesia. · A patient's account of the past seems unreliable. Before revealing the answer, decide what distinguishes a paramnesia from amnesia. · A patient reports difficulty remembering a period of her life. Before revealing the answer, decide how you would explore this. · Explain why the pattern of an amnesic gap — its onset, extent, and whether personal identity is affected or spared — matters clinically, beyond simply confirming that memory loss has occurred.

Illustration

A 40-year-old man cannot recall the ten minutes immediately before a road traffic accident, though he clearly remembers the drive beforehand and everything from waking in the ambulance onward, a clean, circumscribed gap that his doctor explains is a common and expected pattern after this kind of head injury.

References

• Casey, P. & Kelly, B. (2019). Fish's Clinical Psychopathology, 4th ed. Ch. 5, 'Disorders of Memory'.