In a small study, memory recall was better in people with more severe damage to a brain region involved with memory, compared with those with milder damage. With severe damage, other parts of the brain may take on the damaged region's function.
Memory problems that occur with a type of amnesia paradoxically seem to be worse in people with less severe brain damage, compared with those with more damage. Severely injuring a key part of the brain that is involved in memory recall may force the organ to reorganise itself so other areas take on that function.
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| The hippocampus (orange) is a structure in the brain that plays a key role in memory. Less extensive damage to the hippocampus has been linked to worse amnesia than more severe injuries SEBASTIAN KAULITZKI/SCIENCE PHOTO LIBRARY |
Developmental amnesia most often occurs as a result of a baby receiving too little oxygen while being born. This affects a person’s episodic memory, which involves recollecting an experience, including when and where it occurred. However, their other cognitive skills, such as language and intelligence, are typically unaffected, says Faraneh Vargha-Khadem at University College London.
This may be because the region of the brain that is key for episodic memory, the hippocampus, is particularly vulnerable to a lack of oxygen, she says.
Vargha-Khadem and her colleagues wanted to determine how the hippocampus receiving too little oxygen at birth is linked with amnesia severity. They asked 23 people who had been diagnosed with developmental amnesia and 32 people without the condition to complete a series of tests to assess their various cognitive abilities.
One assessment, called the Doors and People test, involves participants being shown images of different coloured doors and the names of people to memorise and then being tested on that information.
The participants with developmental amnesia had worse memory recall than those without the condition. A statistical analysis suggests this wasn’t a chance finding.
However, among the participants with amnesia, those with more extensive damage to their hippocampus had better memory recall than those with less extensive damage. Hippocampus damage was assessed via an MRI scan.
This was particularly true for those with a reduced volume to their uncus, which is located at the front of the hippocampus and is thought to play a key role in memory recall.
The brains of people with more extensive damage to their uncus may undergo reorganisation so that other parts of the brain take over some of its function, says Vargha-Khadem.
Among people whose uncus is less damaged, however, their brain may still rely on this structure to process memory, which could lead to worse recall than if the damage were more severe, she says.
The findings point to both the brain’s plasticity and its limits, as the participants with developmental amnesia still had worse recall than those without the condition, says Vargha-Khadem.
“I believe these findings are incredibly exciting as they begin to shed much needed light on the full potential of brain plasticity while outlining its unavoidable limitations,” says Antonina Pereira at the University of Chichester, UK.