Recurrent depression shrinks an area of the brain that forms new memories, says a new study
Philip Mitchell, Scientia professor and head of the School of Psychiatry at UNSW, said the use of the consortium’s ongoing sample collection was “becoming a very powerful way of looking at what’s happening in brain function”.
“This study confirms – in a very large sample – a finding that’s been reported on quite a few occasions. It’s interesting that none of the other subcortical areas of the brain have come up as consistently, so it also confirms that the hippocampus is particularly vulnerable to depression.”
The hippocampus is part of the brain’s limbic system, or what’s otherwise known as its emotional centre. The system also contains the amygdala, another part of the brain shown to be affected by depression.
While the hippocampus plays an important role in consolidating and forming new memories, Hickie explained that “memories” weren’t just about remembering passwords.
“Your whole sense of self depends on continuously understanding who you are in the world – your state of memory is not about just knowing how to do Sudoku or remembering your password – it’s the whole concept we hold of ourselves,” he said.
“We’ve seen in a lot of other animal experiments that when you shrink the hippocampus, you don’t just change memory, you change all sorts of other behaviours associated with that – so shrinkage is associated with a loss of function.”
Professor of psychiatry at Monash University Paul Fitzgerald said while the findings of the study were important, they were unlikely to immediately affect clinical treatment.
“I don’t think there’s anything that’s really fundamentally going to change overnight, but it’s an important part of the jigsaw puzzle to put together a better understanding of what’s going on in depression, and that obviously has implications for developing better treatments down the track,” he said.
He added that researchers should next measure the volumes of individual regions within the hippocampus that are each responsible for different cognitive functions.
“Having a better understanding of what the regional volume differences are will provide greater capacity to draw conclusions,” he said.
“Hopefully having the involvement of the hippocampus in depression confirmed in such a substantive study will stimulate attempts to better understand what this means.”
It’s important to note, however, that the effects of depression on the brain are reversible with the right treatment for the individual.
“The hippocampus is one of the most important regenerative areas of the brain,” said Hickie.