Study reveals new functions of the hippocampus

31 October 2017

Hong Kong scientists have made a breakthrough in their four-year research on the connectivity of brain functions and how this may help in the early diagnosis and treatment of brain diseases.

The human brain only accounts for 2% of the total body weight, yet it consumes about 20% of the total body’s energy demand. Despite its importance, it is one of the least understood organs of the body.

A research team led by Professor Ed X Wu (Croucher Senior Research Fellowship 2012) of the Department of Electrical and Electronic Engineering at the University of Hong Kong found that the hippocampus, a horseshoe-shaped structure in the middle of the brain that helps process long-term memory, was one of the drivers behind how different brain parts communicate with each other. The team’s findings have advanced our fundamental understanding of the origins and roles of brain-wide functional connectivity.

Different parts of the brain are always talking to each other and they are massively interconnected, but there is very limited knowledge about the brain circuit, its network and how it actually works

During the research, the team conducted experiments on rodents, which have a similar brain structural connectivity to humans.

The technique adopted by the team consists of optogenetics, pharmacological neuromodulation and functional magnetic resonance imaging (fMRI). Optogenetics is a neuromodulation method that uses a combination of techniques from optics and genetics to control the activities of individual neurons in living tissues. Pharmacological neuromodulation uses drugs to manipulate the activities of neurons. fMRI is a large-view non-invasive imaging technique for detecting brain-wide activations. 

Researchers can make use of fMRI to visualize whole brain activity in response to different optogenetic stimulation and pharmacological manipulations. 

With the synergistic combination of the three technologies, the team was able to prove that introducing low frequencies to the hippocampus could increase its connectivity with other parts of the cerebral cortex, the outermost layer of the brain known as a high-powered processor responsible for memory, consciousness and five senses. The research also showed that low frequency stimulation can enhance visual processing by 20 percent in rats.

The breakthrough could potentially help earlier diagnosis and treatment of brain disorders such as Alzheimer’s disease, depression and autism. Patients with Alzheimer’s have reduced functional connectivity between the left and right parts of the hippocampus, but more research is needed to prove further correlations.

Research has already shown that electrical stimulation of the brain can reduce hand tremors of patients with Parkinson’s disease, a degenerative brain disorder that impairs movements.

According to the team, clinical trials were being conducted with optogenetics and it could be a targeted method to treat brain disorders soon.

The research was published in international academic journal Proceedings of the National Academy of Sciences of the United States of America in August. 


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