Electrodes to study how our brain recognises objects

It is the first time that scientists have succeeded to study the visual cortex i

It is the first time that scientists have succeeded to study the visual cortex in this level of detail.

For the first time ever, researchers from KU Leuven have carried out tests on human brains in the area that is responsible for our vision. This research method is unique. The results have been published in PLOS Biology.

To gain a better understanding of the human brain, researchers can rely on several methods. One option is to make scans of people’s brains and see which parts are active while study participants carry out a particular task. This method is time-consuming and the information it provides lacks sufficient detail. A second method involves inserting microelectrodes into the brains of laboratory animals, such as mice, rats, and monkeys. Scientists have already learned much from such studies, but animals and human beings obviously have different brains. Now, professors Tom Theys and Peter Janssen and their colleagues have found a solution: they were able to insert microelectrodes into the visual cortex, the brain area that is responsible for our vision.

Unprecedented detail

Professor Janssen’s lab teamed up with Professor Theys, an epilepsy specialist affiliated with University Hospitals Leuven. In patients with severe epilepsy, doctors sometimes insert electrodes into the brain for a fortnight to record what happens during an epileptic seizure. For the purpose of the current study, the researchers inserted additional microelectrodes in the visual cortex of patients undergoing such a procedure. This allowed them to map out their epilepsy and other brain functions in a higher resolution.

During the two weeks the patients spent in the hospital after the operation, they were regularly shown pictures of objects. Each time, the microelectrodes recorded how individual brain cells reacted to the stimuli, allowing the researchers to study brain cell activity in the visual cortex in this level of detail for the first time.

A few weeks after the electrodes were removed, the patients participated in a second phase of the study. During an MRI scan, the patients were shown the same images once again. This allowed the researchers to see which parts of the brain were active. They went on to compare these details with those recorded by the microelectrodes.

Slower than a monkey

The study produced some interesting discoveries. "We found that the brain cells in this particular area react to certain images of objects in a specific way. We had expected this, but had never been able to demonstrate it," says Professor Janssen. Even so, there were also some surprises: "Based on earlier research, we believed that the brain cells examined would only react if the patient was shown a picture of an object in a particular position on the screen,(for example, in the middle," explains Professor Janssen. "It now appears that these cells also react when the object is in other positions, such as on the left or the right."

Another remarkable finding was that human brain cells react several tenths of a millisecond more slowly than a monkey’s brain cells.

Professors Tom Theys and Peter Janssen will conduct more of these experiments in the future in order to gain a better understanding of the human brain. Once sufficient research has been carried out on humans, and the results obtained are supported by the scientific community, it may be possible to phase out the use of laboratory animals in this field for certain research topics.

The study "Single-cell selectivity and functional architecture of human lateral occipital complex" was published in ’PLOS Biology’.


  • Department of Neurosciences
  • University Hospitals Leuven

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