Hippocampal neural disinhibition

neurosciencestuff Too much activity in one of the brain’s key memory regions is bad for your memory and attention 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 Dr Tobias Bast in the School of Psychology at The University of Nottingham have found that faulty inhibitory neurotransmission and abnormally increased activity in the hippocampus impairs our memory and attention. Their latest research — “Hippocampal neural disinhibition causes attentional and memory deficits” — published in the academic journal Cerebral Cortex, 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. 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. This 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. Increased activity can be more detrimental than reduced activity Dr Bast, said: “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. This is an important finding because traditionally, memory impairments have mainly been associated with reduced activity or lesions of the hippocampus. “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. This probably reflects that there are very strong neuronal connections between hippocampus and prefrontal cortex. Our finding suggests that aberrant hippocampal activity has a knock-on effect on the prefrontal cortex, thereby disrupting attention. “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. 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.”