Harvard University researchers successfully map more than 70,000 synaptic connections using 2,000 rat neurons

Researchers at Harvard University have found that by placing an array of 4,096 micro-hole electrodes on a CMOS chip, they were able to plot the neurons of 2,000 rats and map more than 70,000 synaptic connections.

Synaptic connectivity mapping among thousands of neurons via parallelized intracellular recording with a microhole electrode array | Nature Biomedical Engineering

Harvard team built a CMOS chip to map 70,000 synaptic connections between 2,000 rat neurons | Tom's Hardware

The research was conducted by Professor Ham Dong-hee and his team.

Although synaptic connections can be visualized using an electron microscope, they cannot be measured or recorded. On the other hand, patch clamp electrodes can accurately record weak neural signals, but they can only measure a handful of cells, limiting the study of a large number of neurons.

The microhole electrode array used in the study is similar to a patch clamp electrode, but by arranging more than 4,000 arrays on a single chip, it is possible to effectively monitor thousands of neurons. In addition, one of the features of the study is that it has better access to nerve cells than nanoneedle electrodes and is easier to create.

Although mapping of synaptic connections has been done before, the previous record was only 300. This latest attempt to successfully map more than 70,000 synaptic connections is more than 200 times greater than the previous record.

The amount of information obtained from 2,000 neurons is enormous, and one of the research team's biggest challenges was 'how to analyze the overwhelming amount of data.' In the future, if it is possible to map how each neural connection works in a living brain, it is expected that it will be applied to, for example, training AI and manufacturing more efficient AI chips, which could obtain huge computing power without huge electricity.

It is also anticipated that understanding the firing and misfiring of synaptic junctions will enable researchers to observe how they affect our perception of the mind and be useful in mental health research.

In addition, the human brain has an average of 86 billion neurons, and if we consider that each neuron has an average of 35 synaptic connections, the total number of synaptic connections is 30 trillion. Therefore, this research is just one step on the journey towards mapping the human brain.