Too much brain activity may impair memory, attention

Abnormally increased activity in the brain's hippocampus impairs our memory and attention, and can be more detrimental to cognitive function than reduced activity or a lesion, a new study suggests.
The study has implications for understanding cognitive deficits in a variety of brain disorders, including schizophrenia, age-related cognitive decline and Alzheimer's, and for the treatment of cognitive deficits, researchers said.
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.

Researchers led by Tobias Bast at The University of Nottingham in the UK have found that faulty inhibitory neurotransmission and abnormally increased activity in the hippocampus impairs 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.

The research has shown that a lack of restraint in the neural firing within the hippocampus disrupts hippocampus-dependent memory.
In addition, such aberrant neuron firing within the hippocampus also disrupted attention - a cognitive function that does not normally require the hippocampus.

"Our research carried out in rats highlights the importance of GABAergic inhibition within the hippocampus for memory performance and for attention," said Bast.
"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," he said.
"This is an important finding because traditionally, memory impairments have mainly been associated with reduced activity or lesions of the hippocampus," said Bast.
"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," he said.

"This probably reflects that there are very strong neuronal connections between hippocampus and prefrontal cortex," Bast said.
"Our finding suggests that aberrant hippocampal activity has a knock-on effect on the prefrontal cortex, thereby disrupting attention," he said.
"Overall, our new findings show that increased activity of a brain region, due to faulty inhibitory neurotransmission, can be more detrimental to cognitive function than reduced activity or a lesion," he added.
The research was published in the journal Cerebral Cortex.