Introduction

The brain controls the body through a complex network of neurons that send, receive, and process sensory signals. These signals are responsible for controlling every limb, muscle, appendage, and bodily function. To better understand these signals, neurotechnology combines the fields of neuroscience and engineering to investigate the structure and working principles of the nervous system and to develop tools to interact with it.

The inception of neurotechnology can be traced back to the late 19th century when neurological structures were mapped by scientists like Santiago Ramon Y. Cajal using various staining methods.^[1] In the 1920s, German neurologist Hans Berger developed electroencephalography (EEG), enabling the measurement of the brain’s electrical activity. Then, in 1971, physician Raymond Damadian developed the first magnetic resonance image (MRI) of a human finger. With the onset of the 21st century, innovations such as deep brain stimulation (DBS), brain-computer interface (BCI), and neural prosthetic devices have advanced neurotechnology. Today, neurotechnology plays an important role in the diagnosis and treatment of neurological and psychological illnesses while also contributing to the improvement of cognitive and sensory capabilities.^[2] Neurotechnology also has applications in education; for instance, EEG can be used to measure the brain waves of a learner and provide feedback regarding the level of attentiveness, engagement, and memory.

Understanding the Core of Neurotechnology

Neurotechnologies fall into four categories: neural interfaces, neuromodulation technologies, neuroprostheses, and BCIs. These techniques have myriad applications in vastly diverse fields, such as medicine, neuroscience, psychology, education, and entertainment. From pharmaceuticals that improve quality of life to brain imaging that revolutionizes our conception of human consciousness, neurotechnologies stand to change our understanding of ourselves and harness the power of the brain and nervous system’s myriad functions to promote human thriving.

Neural Interfaces

One of the main applications of neurotechnology is the development of neural interfaces. These devices can record and stimulate neural activity. Depending on how they are placed on or in the body, neural interfaces can be classified into three types: 

• Invasive, examples of which include implanted stimulators for the treatment of Parkinson's disease and cochlear implants for hearing restoration. 

• Non-invasive, comprising EEG electrodes outside the body that can control digital objects or interface with the computer. 

• Partially invasive, which are placed under the skin but do not enter the brain (for example, electrical foot stimulators).^[3]

Neural interfaces are effective for restoring motor functions, improving cognitive abilities, and monitoring health conditions, and enabling novel forms of human-machine interaction.^[4]

Brain-Computer Interfaces

BCIs are systems where a computer communicates with an individual's brain to control outside objects or applications via invasive or non-invasive electrodes implanted in the brain or on the attachment to the scalp. Subsequently, algorithms such as machine learning and deep learning are capable of analyzing brain waves to generate commands, linking the outside world directly to the brain.^[5] Potential applications of BCIs include restoring function for patients with neuromuscular disorders^[6], enhancing rehabilitation from strokes or traumatic injuries, and creating virtual reality experiences.

Neuroprosthetics

Neuroprosthetics is an amalgamation of neuroscience and bioengineering aimed at developing medical apparatuses that act as substitutes for or upgrade normal functions of nerve systems. Neuroprosthetics are mainly used to restore functions such as sensory, motor, and cognitive abilities impaired by trauma and diseases. Illustratively, cochlear implants assist people who are deaf or hard of hearing in understanding speech. In contrast, paralyzed individuals manipulate artificial limbs^[7] or a computer using thoughts through BCIs.

Neuroprosthetics is based on two key ideas. Firstly, electrical signals generated within the brain can be picked up and deciphered by external equipment. Secondly, these devices may also give feedback to the brain using electrical stimulation.^[8] Neuroprosthetics is growing rapidly using new technology like artificial intelligence (AI), brain imaging, or nanomaterials that provide novel opportunities in terms of health and well-being.^[9]

Prosthetic hand using advanced BMI (brain/machine interfaces) technology to deliver capability and usability. Image credit: Brain Robotics

Neural Modulation by Stimulation

Neural modulation by stimulation involves manipulating nervous system activity through external stimuli such as electric current, magnetic field, or chemical substances. These stimuli may change the excitability, firing patterns, connectivity, and plasticity of neurons, which in turn influences the functions and behavior of neurons.^[10]

DBS is one of the many methods used in neural modulation by stimulation. It is a process whereby electrodes are placed on selected areas of the brain, sending electrical signals into them to alter their output. It is used for treating movement disorders like Parkinson's disease, essential tremors, dystonia, and psychiatric conditions such as obsessive-compulsive disorder (OCD) and depression.^[11]

Another method, transcranial magnetic stimulation (TMS), has the same principle as EEG but includes placing a coil on the scalp and generating a magnetic field, causing an electric current below brain tissue.^[12] The main uses of TMS have been for treating different neurological and psychiatric illnesses like stroke, migraine, and schizophrenia.

The Technological Innovations Driving Neurotechnology

Neurotechnology has experienced tremendous growth in areas like sensing, stimulus deliveries, neural signal captures, and manipulation. For instance, many technical advancements in microelectrode arrays, machine learning and artificial intelligence, advanced imaging techniques, biomaterials, and nanotechnology drive these achievements.

Microelectrode Arrays

Microelectrode arrays (MEAs) are versatile devices with multiple microelectrodes that facilitate the extraction and delivery of neural signals. MEAs act as vital connections between neurons and electronic circuitry, functioning as neural interfaces. Their primary purpose is to record and stimulate neural activity in various settings, in vitro or in vivo, based on the specific type and design of the MEA.^[13]

To capture neural activity, the electrodes within an MEA convert the ionic currents resulting from neuronal depolarization into measurable electronic currents. Conversely, to induce neural activity, these same electrodes transform electronic currents into ionic currents that activate voltage-gated ion channels present on neuronal membranes. They can help restore both sensory and motor functions, as well as provide treatment for neurological disorders.^[14]

Machine Learning and AI

The intersection of machine learning, AI, and neurotechnology is a fascinating field of research that plays a crucial role in advancing neurotechnological research by providing powerful tools for analyzing complex datasets like brain imaging, neural recordings, and behavioral data.^[15] These tools aid in uncovering patterns and principles that govern brain function while identifying the neural correlates of cognitive processes, emotions, and mental disorders.

Additionally, machine learning and AI facilitate the development of innovative neurotechnologies that can interact with the brain in real-time, including BCIs, neurofeedback systems, and neural prosthetics. This synergy between disciplines holds immense potential for unlocking new insights into our most complex organ.

Advanced Imaging Techniques

Neurotechnology researchers can access advanced imaging techniques such as functional magnetic resonance imaging (fMRI) and positron emission tomography (PET). Using these powerful tools, they can measure brain activity in living subjects when exposed to different stimuli or performing various tasks. By doing so, they can uncover the neural correlates of cognition, emotion, perception, and behavior to help identify specific brain regions and networks involved in mental processes like memory, attention, language, and decision-making.^[16]

PET scan machine uses radiotracers to evaluate tissue functions. Image credit: Health Jade

Biomaterials and Nanotechnology

The design of neurotech devices must take into consideration the biocompatibility with the brain and other neural tissues in order to avoid any harmful effects on biological systems. One approach to achieving biocompatibility is by utilizing biomaterial substances that can be applied to various components of neurotech devices, including coatings, electrodes, scaffolds, or implants.^[17] However, the challenges faced by neurotech devices can be fully addressed with the complimentary use of nanotechnology.

Nanotechnology focuses on exploiting matter at the nanoscale, between 1 and 100 nanometers in scale, where matter displays unique and improved properties that can be utilized for applications in neurotechnology.^[18] Combining biomaterials with nanotechnology enhances the biocompatibility and biodegradability of nanotech devices while improving their electrical, optical, and magnetic characteristics.^[19] 

Ethical Implications and Future Prospects

Despite the revolutionary aspects of neurotechnology, it brings forth essential ethical considerations that must be addressed before its widespread adoption. How can we guarantee the privacy and autonomy of neurotechnology users when it involves accessing or manipulating their brain data or functions? This crucial question demands thoughtful exploration and robust solutions. The misuse of neurotechnology by malicious individuals or authoritarian governments poses a significant threat to the rights and security of individuals. Therefore, it is crucial to establish effective regulations and monitoring mechanisms for developing and implementing such technologies.^[20]

Despite the ethical concerns, the future of neurotechnology is filled with excitement and challenges alike. It necessitates collaboration among scientists, engineers, ethicists, policymakers, and stakeholders from various disciplines. Each application must be thoroughly assessed to weigh its benefits and potential risks for individuals and society as a whole. To ensure the responsible and beneficial use of neurotechnology for humanity, ethical principles, and guidelines need to be developed.^[21]

Conclusion

The field of neurotechnology is advancing rapidly, offering exciting possibilities for enhancing human capabilities and improving health outcomes. However, along with these promises come essential ethical, social, and legal challenges that demand attention from researchers, policymakers, and stakeholders. This article explores current and emerging applications of neurotechnology, such as brain-computer interfaces, neurostimulation, neuroimaging, and neurofeedback. We also overview the potential benefits and risks associated with these technologies while examining the ethical principles and frameworks that can guide their development and use. In conclusion, we recognize the transformative potential of neurotechnology for society but emphasize the need for thoughtful governance to ensure safety, efficacy, and respect for human dignity.

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