While traditionally, memory impairments have mainly been associated with reduced brain activity in certain areas, new research has found that abnormally increased activity in the hippocampus can also impair our memory and attention.
The hippocampus — a part of the brain that sits within our temporal lobes — plays a major role in our everyday memory of events and of where and when they happen: for example, remembering where we parked our car before going shopping.
"Increased activity within a brain region can disrupt not only the function of the region itself — in this case hippocampus-dependent memory — but also the function of other regions to which it is connected, in this case prefrontal cortex-dependent attention," said lead researcher Tobias Bast at The University of Nottingham in England.
Neurons in the brain interact by sending each other chemical messages, so-called neurotransmitters. Gamma-aminobutyric acid (GABA) is the most common inhibitory neurotransmitter, which is important to restrain neural activity, preventing neurons from getting too trigger-happy and from firing too much or responding to irrelevant stimuli.
"Our research carried out in rats highlights the importance of GABAergic inhibition within the hippocampus for memory performance and for attention. The finding that faulty inhibition disrupts memory suggests that memory depends on well-balanced neural activity within the hippocampus, with both too much and too little causing impairments," Bast noted.
"Our second important finding is that faulty inhibition leading to increased neural activity within the hippocampus disrupts attention, a cognitive function that does not normally require the hippocampus, but depends on the prefrontal cortex," Bast pointed out.
The findings of the study have appeared in the journal Cerebral Cortex.