Discovering the Brain's Flexibility
The brain is a mysterious organ. It fits snugly inside our skulls, and at first glance, it is not clear what it is doing. To the naked eye, it looks like nothing more than a soft, white, tofu-like mass. However, Santiago Ramón y Cajal and Camillo Golgi, neuroanatomists active in the 19th century, discovered that within this mass, cells called neurons, only a few microns in size, form a network. Branch-like protrusions extending in all directions from the neurons connect to other surrounding neurons, and various information is processed through the instantaneous flow of electrical currents and chemical substances within them. The brain is a network, a computer.
The brain has another mysterious characteristic. This is its ability to reconfigure the neural network by rewiring the branches that connect neurons or by changing the strength of these connections. This property is called "plasticity." Because the brain possesses this property of plasticity, the neural network can be reorganized to bypass damage caused by stroke or head trauma, allowing for the recovery from relatively minor functional impairments.
Thus, the brain's plasticity is an essential element for healing functional impairments caused by accidents or diseases, but unfortunately, we still do not fully understand its mechanisms or how to manipulate it. Moreover, the adult brain is quite stubborn, and the large-scale plasticity seen in the brains of children, or animals like mice and monkeys, does not occur so easily. This is why complete recovery from stroke or head trauma is often difficult.
Nevertheless, our laboratory continues to take on the challenge of unraveling the mechanisms of this "plasticity in the adult brain." We conduct high-precision analysis of electrical brain activity by placing 128-channel EEG electrodes on the head (Fig. 1; Hasegawa et al., *J Neuroeng Rehabil* 2017), and in collaboration with hospitals, we use MRI to analyze the structure and function of brain tissue with a resolution of 2 mm, including deep areas (Fig. 2; Kodama et al., *Front Hum Neurosci* 2018). Furthermore, in our research using a "brain-machine interface" (Fig. 3) that drives a wearable robot in response to brain activity detected in real time, we are beginning to see results, such as successfully inducing recovery from severe hemiplegia after stroke, which was previously considered difficult to treat (Takasaki et al., The Annual BCI Award 2017 Top 12 Nominees; Nishimoto et al., *J Rehabil Med* 2018; Mukaino et al., *J Rehabil Med* 2014; Shindo et al., *J Rehabil Med* 2011).
We are tackling brain science by fully mobilizing our knowledge of science and technology to uncover the secrets of plasticity. Through this, we aim to transform severe neurological disorders, once considered untreatable by conventional medicine, into "curable disabilities." In the very things that everyone thinks are impossible, there are dreams, surprises, and technological innovations. We are the ones who will create the future. We welcome all of you who believe in the power of science and are determined to move forward without hesitation. We invite you to step into this field, which is full of exciting possibilities.