A research team led by Professor Ed Wu, Chair Professor of Biomedical Engineering at the University of Hong Kong (HKU), has made major breakthrough in unveiling the mysteries of the brain to reveal functions of an important region, hippocampus, not known to scientists before.

The breakthrough is said to offer insights into causes and treatments of various brain diseases, as the hippocampus, located underneath the cortex, plays important roles in memory and navigation.

For instance, Alzheimer's disease and other forms of dementia have been proven to have affected and damaged this area of the brain, resulting in early symptoms including short-term memory loss and disorientation. People with hippocampal damage may lose the ability to form and retain new memories. The hippocampus is also closely related to other diseases such as epilepsy, schizophrenia, transient global amnesia and posttraumatic stress disorder.

Findings of the study have recently been published in Proceedings of the National Academy of Sciences of the United States of America (PNAS) in August 2017.

Findings may aid treatment of Alzheimer's disease

Despite being considered as an important component in our brain, the role of hippocampus in complex brain networks, particularly its influence on brain-wide functional connectivity, was not well understood by scientists.

To investigate its impact on the functional integration between spatially separated brain regions, Prof Wu led Dr Russell W. Chan, Dr Alex T. L. Leong and others to conduct rodent experiments.

Based on current knowledge, one expects the hippocampus to predominantly generate high-frequency activities and these activities are largely confined within the hippocampus. However, in this study, results reveal that low-frequency activities in the hippocampus can drive brain-wide functional connectivity in the cerebral cortex and enhance sensory responses.

Hippocampus. Photo credit: HKU
Hippocampus. Photo credit: HKU

Since the cerebral cortex is the largest region of the mammalian brain and plays a key role in memory, attention, perception, cognition, awareness, thought, language, and consciousness, the results thus imply low-frequency activities of the hippocampus can drive the functional integration between different regions of the cerebral cortex and enhance the responsiveness of vision, hearing and touch. These results further indicate that hippocampus can be considered as the heart of the brain, a breakthrough in our knowledge of how the brain works.

In addition, the findings also suggest that low-frequency activities in the hippocampus can enhance learning and memory since low-frequency activities usually occur during slow-wave sleep which has been associated with learning and memory.

Slow-wave sleep, often referred as deep sleep, is a state that we usually enter several times each night and is necessary for survival. Alzheimer's disease is a chronic neurodegenerative disease that usually starts slowly and worsens over time, and the most common early symptom is memory loss. Hence, these results may also have potential therapeutic implications of hippocampal neuromodulation in Alzheimer's disease.

The research team said their findings are a major step in furthering our fundamental understanding of the origins and roles of brain-wide functional connectivity. These findings also signify the potentials of rsfMRI and neuromodulation for early diagnosis and enhanced treatment of brain diseases including Alzheimer's disease, dementia, epilepsy, schizophrenia, transient global amnesia, and posttraumatic stress disorder.

Challenge for neuroscience in the 21st century

The human brain is the source of our thoughts, emotions, perceptions, actions, and memories. While the human brain only accounts for 2% of the total body weight, 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. How it actually works remains largely unknown.

One grand challenge for neuroscience in the 21st century is to achieve an integrated understanding of the large-scale brain-wide interactions, particularly the patterns of neural activities that give rise to functions and behaviour.

In 2010, the National Institute of Health (NIH) in the US launched the Human Connectome Project which aims to “provide an unparalleled compilation of neural data, an interface to graphically navigate this data and the opportunity to achieve never before realised conclusions about the living human brain”.

In 2013, the Obama administration in the US launched the BRAIN Initiative to “accelerate the development and application of new technologies that will enable researchers to produce dynamic pictures of the brain that show how individual brain cells and complex neural circuits interact at the speed of thought.”

In November 2016, China launched its own initiative “China Brain Project”, which aims to advance basic research on the neural circuit mechanisms underlying cognition in hopes to improve brain disease diagnosis/intervention and inspire development of brain-machine intelligence technology. MIMS

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