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What is Whole Brain Emulation

As humans, limitations are inherent to our existence. Our perceptions are narrow and our attention is constrained; we struggle with illness and injury. These hindrances often seem insurmountable, but we still strive to push the boundaries to their breaking points. Can you imagine what it would be like to live a life untethered, free from the physical constraints of a body? In the future, a technology called whole brain emulation (WBE) could make it possible to have unprecedented experiences such as seeing centuries of existence, developing heightened abilities of prediction, perceiving the world through new senses, or recalling details with the precision of a computer (1). An individual could potentially live indefinitely (2). WBE is the process of creating a replica of the brain so that it can operate in a digital form. Instead of acting as a model, this replica would function in an identical manner to the brain in the biological substrate (3). A simulation operates as an imitation of a structure, existing solely for observation, while an emulation reproduces behavior.

We have always been concerned with evolving as a species. We are full of ambition, anxious to go further and achieve more than the humans of the past. We have transformed ourselves and the whole world by building cities, connecting communities, and inventing technologies that were once inconceivable. Whole brain emulation may enable us to transcend boundaries in a way never seen before. By becoming substrate-independent, or autonomous from our physical bodies, we could overcome fundamental limitations that include constrained attention, unreliable memory, illness, fatigue, and the human lifespan.

WBE depends on a functionalist understanding of the mind, which says that the operations of the brain produce a cohesive, conscious human. The mind can be reproduced as long as neuronal function is emulated. Since the brain is constantly changing itself at the molecular level (4), the mind can be considered a dynamic process that does not necessarily arise from the specific physical matter of neurons. Consequently, it can be emulated in a non-biological substrate.

The first steps of WBE are scanning and modeling. Before we can emulate the individual details of a brain, it is necessary to build a connectome — a complete map of neural connections. This establishes a baseline model and helps us properly understand the relationships and functions of neurons. To facilitate modeling on an individual scale, the brain must be scanned. One essential technology of connectomics is electron microscopy, which utilizes radiation from electrons to obtain high-resolution images (5). By using the technology to photograph thin slices of tissue, researchers have mapped the connectome of the fruit fly Drosophila (6) and reconstructed a region of the human hippocampus in a computer model (7). As an alternative to imaging, large-scale dynamic recording could build a map of neural function. This is already possible in C. elegans (8). Recently, fluorescence microscopy has allowed for the mapping of an entire primate brain at a detailed, micrometer resolution (9); such a feat took only 100 hours. Although a macaque brain is less complex than a human brain, this opens the encouraging possibility of a future human connectome.

After an accurate simulation, the process of translation will convert a neural model to a working emulation, combining structure and function. The product could potentially resemble existing neural networks that possess the human-like ability to predict and learn based on input. Through digital software, equations could mimic action potentials (10). However, emulations would incorporate all the mechanisms and organic flexibility of biological organisms rather than being constrained to the comparative simplicity of current-day artificial intelligence (11). While the computers of today cannot use common sense, understand emotion, conceptualize identities, or reason through logical arguments, an emulated being would have all these capabilities. One technological development that may be a precursor to WBE is neural prosthesis, comprising devices that replace missing or deficient function, such as cochlear implants that transduce sound. Visual prosthetics restore sight (12), motor prosthetics enable conscious control of movement (13), and tactile prosthetics allow amputees to perceive touch and pain (14). Researchers have developed a hippocampal prosthetic that enables the formation of long-term memories (15). These devices show that it is possible for technology to successfully emulate the workings of biological neurons.

There are two procedural methods for WBE that are currently being discussed: gradual replacement and scan-and-copy. Gradual replacement would slowly install technological devices in place of neurons or neural circuits, whereas scan-and-copy would image the brain in order to emulate it in a digital substrate. The former is an inherently destructive process, but the latter may preserve the original brain depending on future advances in technology. The method of destructive scan-and-copy would likely come before gradual replacement as well as non-destructive scan-and-copy. There is a misconception that gradual replacement is superior to scan-and-copy, as it might better ensure personal survival through utilizing the same body; however, the two procedures are not so different from each other. Both would result in a transfer of functional activity. As the original brain is destroyed through gradual replacement, biological neurons yield their function to devices and can no longer operate. The same would be true for a destructive method of scan-and-copy, regardless of the distance traveled. The preservation of identity and survival are equally likely in both gradual replacement and scan-and-copy scenarios (16).

Moving away from the technological possibilities, WBE presents several philosophical questions. Would an emulated brain develop a personality or identity, and would it match that of the biological brain? Would our minds be transferred or would we stay in our bodies? How can a machine develop consciousness? What is consciousness, and how can identity be defined? As far as we know, neither identity nor consciousness is magical; instead, they are tangible and arise from brain activity (17). The concept of the self can be traced to a series of regions included in the default mode network, which is active upon rest and associated with mind-wandering (18). As described in the attention schema theory, consciousness is subjective awareness that is constructed in a model of attention similar to the body schema (19). In other words, the brain can focus on certain signals while dimming others; when this is built into a representation, consciousness emerges. Based on this theory, consciousness is able to be emulated like any other neural function, as are identity and personality.

The transfer of consciousness is a tricky idea. Most likely, there will be two entities with awareness (assuming the original brain is not destroyed), but there is no consensus on whether a procedure of WBE would result in personal survival. Addressing this concern, psychological branching identity says that continuity of consciousness will occur in the uploaded brain as well as the original brain (20). Both minds would have an equal claim to the original identity. A similar phenomenon occurs in split-brain patients, where the severing of the corpus callosum results in two conscious states (21). Each hemisphere is independently alert, but each is psychologically continuous. This is also comparable to the two cells created upon the division of a single-celled organism. Therefore, an emulation would not be a copy, but an individual with continuity of consciousness and identity.

Despite these potential answers, a discussion of mind uploading is still quite speculative. There is much uncertainty on the path forward. Instead of becoming discouraged, we should use our questions as motivation to spur the development of whole brain emulation.

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