The researchers found mice bred to lack the ghrelin gene had 25% fewer 'synaptic' connections between nerve cells in this area.

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But if you have a long-term memory, you alter the expression of genes in the brain and you grow new synaptic connections.

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One of the things that Dr Kandel's previous work has shown is that long-term memory is the result of new proteins being made at the synaptic connections between nerve cells.

ECONOMIST: Prion proteins

Different colors represent different synaptic types.

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