First of all, sorry for the immense length of this suggestion. I had so much ideas, and I needed them to be as developed and as clear as possible.

I saw this suggestion #53 about adding chips to your brain to upgrade it and possibly replace it. The idea is interesting, but you can’t just replace something as complex as your brain with a conventional computer, and I really dislike the idea of copying yourself on a computer. Sure, it’s still you, but the organic you (the original you) dies after the copying, so it’s a copy of you that’s still you, but not you since it’s another separate being. It’s really weird.

So instead of just replacing your brain, I had the idea of a whole new tech level based on upgrading, modifying and butchering your brain to enhance some of its processes, which would have interesting or dangerous repercussions on your behavior and capabilities.

A new, specialized Robosurgeon:

Brain modification can’t be done right at the start of the game. A normal Surgery Chamber can do wonders, but it has its limits; it can replace limbs and organs with artificial counterparts, but it lacks the finesse to manipulate the fragile tissue of our brains. For that, a new chamber is needed: the Neurosurgery Chamber, powered by a -deep breath- Roboneurosurgeon. This upgrade of the standard Robosurgeon can’t simply be crafted, and is obtained via a blueprint found either in dungeon chests or in a special structure, like some kind of ruined laboratory. Inside, we could find damaged Roboneurosurgeons, that we could scan to get a blueprint.

The Neurosurgery Chamber is made by placing a Roboneurosurgeon on top of a regular Surgery Chamber. Accessing it reveals the head of the player, whose skin, then skull disappear to reveal the brain and its different regions and structures.

Specific brain structures:

These structures are similar to normal organ items in that they have a function, and have unique consequences if removed. I've provided a list of them below, with a description of their purpose and the effects of their removal.

List of brain structures:

1. Occipital Lobes: Responsible for vision and object recognition. Removal will cause complete blindness (independent of the presence of eyes or Cybereyes);

2. Temporal Lobes: Responsible for hearing, memory storage, thought and language. Removal will cause deafness and loss of higher thought (fancy words for death, more info after this list);

3. Parietal Lobes: Process sensory inputs such as touch, pain, temperature, as well as spatial sense and navigation. Removal will cause inability to feel pain (hides health bar), to feel temperature (If Tough as Nails is installed, hides temperature meter, and negative effects caused by hypothermia/hyperthermia will not be applied, meaning you won’t get slowed down from being too cold, but you can still die from extreme temperatures), and inability to interact with anything correctly (when moving your mouse, it will move in a random direction). Removal may also cause loss of higher thought (around 50% chance of dying);

4. Frontal Lobes: host all higher thoughts and processes, such as reasoning, planning, movement, complex emotions and speech, but also creativity, judgment and problem-solving. Removal will cause complete paralysis (inability to move and interact) and loss of higher thought (death again);

5. Cerebellum: controls your balance, coordination, posture and fine movement. Removal will cause loss of most motor control (extreme slowness, difficulty moving the mouse, and left/right click will only rarely work);

6. Hypothalamus: Controls body temperature, hunger, thirst, digestion and sleep. Removal will cause death;

7. Thalamus: Connects most parts of the cerebral cortex together, allowing hub-like transfer of sensory and motor information. It also plays a role in regulating consciousness, sleep, and alertness. Removal will cause death;

8. Hippocampi: Responsible for the formation, storage and access of memory. Removal will cause loss of all memory (loss of exp levels and inability to gain more, as well as the inability to read (all text will be changed to an incomprehensible font, similarly to the Abyssalcraft mod));

9. Amygdala: Controls basic emotions, such as joy, anger, fear, and indirectly motivation. Removal will cause loss of emotions and of all motivation (trying to interact with anything will just bring a small text saying you don’t feel like, or don't see a purpose in doing said action. You can still move, but barely);

10. Brain stem: Maintains vital body functions, such as breathing, heartbeat, and digestion, controls basic reflexes, and acts as a bridge between the rest of the brain and the spinal cord. Removal will cause death.

Loss of higher thought and Lobotomites:

Loss of higher thought means the player will lose most of its higher cognitive abilities, and will revert to an animalistic behavior. This will kill the player, and spawn a Lobotomite, a new entity that has the skin, inventory, equipment and implants (and brain damage) of the player that died, and behaves like a zombie (except it doesn’t burn in the daylight).

New brain regions and categories:

Here’s a weird visualization of how I would see the organization of the different categories that appear when using a Roboneurosurgeon:

While this organization tries to keep similar or neighboring brain structures together, I feel like it should be reworked a bit since it leaves the limbic system with only 4 free slots, which isn’t ideal.

New brain implants:

Now that I’ve introduced the new structures that compose the brain, we come to the actual brain implants. Damaged brain implants can rarely be found in chests in laboratories, or on feral Lobotomites that spawn in them. I’ve provided a list of brain implants I’ve come up with that could be useful. Please note that most already existing brain implants (Threat Matrix Calculator, Neural Contextualizer, etc) would have to be modified so they can only be applied by a Neurosurgery Chamber. Cranium implants (Cranial Broadcaster and Ender Jammer) should remain installable with a normal Surgery Chamber, since they don’t interfere with the brain itself.

Cerebral Cortex implants:

1. Neural Contextualizer (Frontal Lobes required);

2. Task Allocator (Frontal Lobes required): Allows for multitasking: automates food consumption and neuropozyne injection, and eating, drinking and shooting with a bow will not slow you down anymore;

3. Temperature Inhibitor (Parietal Lobes required): Reduces effects from environmental temperatures: if Tough as Nails is installed, negative effects caused by hypothermia/hyperthermia will not be applied, meaning you won’t get slowed down from being too cold. The effects are purely psychological though, and you can still die from extreme temperatures;

4. Advanced Graphics Processor (Occipital Lobes required): Enhances the capabilities of the Targeting Overlay, allowing it to highlight targets from further away, as well as chests and items;

5. Audio-visual Mapper (Temporal Lobes and Occipital Lobes required): Greatly enhances auditory processing, allowing you to detect and visualize the location of entities from the sounds they make (moving entities and invisible moving entities will be highlighted when less than 5 blocks away. Adding this feature would mean removing the Targeting Overlay’s ability to highlight invisible entities);

6. Artificial Photographic Memory (Frontal Lobes and Hippocampi required): Greatly increases chances of getting a blueprint from deconstructing any implant;

7. Movement Fine-Tuner (Frontal Lobes required): Tunes interactions between artificial limbs and the brain so they’re as effective as possible. Increases speed with Cyberlegs, increases attack strength and mining speed with Cyberarms, and slightly increases the first two with Myomer Muscles;

8. Hudmind (Occipital Lobes required): An alternative to the Hudlens and Hudjack that transmits the info directly to your conscience;

9. Arcane Decryptor (Temporal Lobes required): automatically translates the Minecraft enchantment table language (just for fun);

Limbic System implants:

1. Threat Matrix Calculator (Thalamus required);

2. Cortical stack (Hippocampi required);

3. Consciousness Transmitter (Hippocampi and Thalamus required);

4. Fear Inhibitor (Amygdala required): Inhibits fear when threatened, granting an immunity to weakness. Acts as an upgrade/alternative to the Cardiomechanic Pump, which prevents the installation of other heart implants;

5. Centralized Controller (Thalamus required): Reduces Interference (the brain equivalent for tolerance, more info after this list) by monitoring and optimizing the activity of all brain implants;

6. Emergency Hunger Override (Hypothalamus required): Allows you to run while starved. When running with an empty food bar, heath will deplete more quickly;

7. Melatonin Distributor (Hypothalamus and Thalamus required): Makes sleep more restful. After sleeping, gives a bonus to attack damage and mining speed for 10 minutes. In 1.13 and above (if the mod gets updated to a higher version), this implant makes phantoms passive towards you, and disables phantom spawning;

Hindbrain implants:

1. Wired Reflexes (Brain Stem required): Since reflexes that make you face your opponent and draw your sword are too complex to be stretch reflexes, it would make more sense for Wired Reflexes to be implanted in the brain stem, where other complex reflexes are processed;
   Turns out I misunderstood something when doing my “research”, which resulted in some major confusion about what kind of reflexes occur in the brain stem (only the most vital ones, like swallowing and vomiting). So yeah, Wired Reflexes should remain in the muscles.

2. Cerebrospinal Fluid Filter (Brain Stem required): Slightly reduces Interference by improving the filtering of toxins that accumulate in the brain;

3. Internal Gyroscope (Cerebellum required): Allows for better balance and control over your posture. You won’t slip on ice anymore, and knockback from attacks is reduced;

4. Enhanced Fine Motor Control (Cerebellum required): Increases yield from deconstructing any implant (Fine Manipulators should have the same ability, which stacks with this one).

Interference:

Of course, there needs to be something that limits the use of these brain implants, just like with other implants, else they would be overpowered. No tolerance here, but a new value called Interference, which represents the amount of interference the implants cause on your brain activity. The bar starts empty, and the more implants you add the more it fills. Too high of an Interference can cause negative effects, like debuffs on some brain and body implants and on your general movement and actions (eating, attacking, even sleeping and opening your inventory), and at higher levels can cause epilepsy (inability to control your character for a few seconds, followed by temporary debuffs like those cited before), strokes (deletion of a random brain structure, and the effects that come with its removal), and ultimately, death.

And that’s pretty much it. Sorry again for the unreasonable length of this idea, and I hope you find it interesting. Of course, feel free to express your own thoughts on this, and please point out any problems or inconsistencies I might have missed.

Your describing a new mod at this point. Seeing how existing code base is a bit messy, that would be no easy feat to add such large design changes.

Now regarding your proposal, here is a few things to consider:
1- Keep It Simple Stupid: you've too many limbic organs, just regroup them to only 2 instead of 4. The Cerebral cortex level seems superfluous, consider flattening the structure.

2- Look from further away on what you describe:

• Temperature inhibitor is misnamed: its functionality is more of adrenaline boost than actual temperature shielding. A better name will help adjust its functionality to something more interesting (remove or reduce slowness effect is easier to grasp and more generic than just TaN).
• On similar thought, the Audio-visual Mapper should see all sounds not just entities. There's something similar in OpenBlocks with an helmet that visualize sound sources.
• Also, Emergency hunger override is more an acceleration of what your body does naturally (eating your own muscles when lacking food). By extension, it would give you slowness or something after you eat again while you rebuild your muscle, or something alike?

3- The range of targeting overlay (25 m) is there to reduce the CPU load. It also relates to vanilla rendering limitations and (de)spawn ranges.

4- Increasing blueprint chance is a interesting addon. It would need more work here. Notably, neurosurgeon is late game here, it might be too late for blueprint chances since at this point you've already a bunch of Cyberware scanner.

5- Wired reflexes is about prerecorded motions, it's not about sensing and reaction. What you're describing is a different version or extension of it. Also, you're not describing something "wired" anymore, so it would need a better name.

6- Stay consistent: essence is something positive that you loose/consume from adding implants. Interference is something negative that increase from adding implants. Both should be positive to be consistent (and also more positive, pun intended). That being said, this proposal breaks the balance of other non-neural implants which has more room to use essence. Instead, the neural implants should still consume essence (your brain is still part of your body), but maybe add another parameter or some sub-section of essence dedicated for brain stuff. Long story short, that part needs more thoughts (yes, another pun).

You've too many limbic organs, just regroup them to only 2 instead of 4

I see. Personally, I would keep the hippocampi and amygdala, because they have interesting effects when removed: the first erases your memory, making you lose your exp levels, preventing you from gaining more, and becoming illiterate, and the second turns you into a hollow shell, devoid of all emotion and motivation. Two dangerous situations that you really don’t want to happen, but that could happen if you modify your brain too much and suffer from a stroke (deletion of a random brain part, and the effects that come with its removal).

The Cerebral cortex level seems superfluous, consider flattening the structure

I separated the cerebral cortex into its four areas because together they have quite a lot of corresponding implants, and regrouping them in one category would not leave enough room (only 4 slots) to really do much. Maybe we could keep each area in its own category, but remove the cerebral cortex level?

Temperature inhibitor is misnamed: its functionality is more of adrenaline boost than actual temperature shielding

Yeah, I thought this one was a bit weird too. How about I rename it to Torpor Compensator? It would negate feelings of numbness from cold and certain potions effects, thus granting an immunity to slowness. A bit less realistic than my first idea, but a lot more useful.

the Audio-visual Mapper should see all sounds not just entities. There's something similar in OpenBlocks with an helmet that visualize sound sources

Oh yeah, that idea is so much better than what I proposed, I love it.

Also, Emergency hunger override is more an acceleration of what your body does naturally. By extension, it would give you slowness or something after you eat again while you rebuild your muscle, or something alike?

Slowness (would not be affected by the Torpor Compensator) is a good idea, but I would see it only trigger after you start taking damage from starvation, and the duration would be proportional to the amount of health lost that way. I would also rename this implant to something like Emergency Autophagy Override, because using hunger here sounds a bit weird.

The range of targeting overlay (25 m) is there to reduce the CPU load. It also relates to vanilla rendering limitations and (de)spawn ranges.

Oh, I didn’t know that. Maybe, instead of increasing the range, it could make it so we completely see entities through walls, with their textures and everything (not true x-ray vision, but more like augmented reality: the implant guesses what mobs are highlighted and superposes textures on them before the info is sent to your conscience). And what about chests and items? I’m not a modder, so I don’t know if highlighting them or making entities visible through blocks is possible.

Notably, neurosurgeon is late game here, it might be too late for blueprint chances since at this point you've already a bunch of Cyberware scanner

Not necessarily. Sure, you would be quite advanced by the time you got to brain implants, but you could get lucky and have an artificial photographic memory as your first one, which would accelerate the obtention of all other brain implants. And you know you can directly install salvaged implants, so you could temporarily do the same with the salvaged artificial photographic memory you got to more easily obtain the other brain implants. So yeah, it may not be the most useful, but it’s not useless either.

Wired reflexes is about prerecorded motions, it's not about sensing and reaction

Turns out I misunderstood something when doing my “research”, which resulted in some major confusion about what kind of reflexes occur in the brain stem (only the most vital ones, like swallowing and vomiting). So yeah, Wired Reflexes should remain in the muscles, sorry about that.

this proposal breaks the balance of other non-neural implants which has more room to use essence. Instead, the neural implants should still consume essence, but maybe add another parameter or some sub-section of essence dedicated for brain stuff

My idea was to make brain implants independent from the essence used by other body implants, so you can modify your brain without reducing the number of body implants you can have. I guess also making them use essence would make sense too, but they would use a lot less of it than body implants (1 to 3 points max) since they're smaller and higher-tech.

essence is something positive that you loose/consume from adding implants. Interference is something negative that increase from adding implants. Both should be positive to be consistent

Interference could be renamed to something like integrity to make it positive like essence, but that would make it less straightforward. Its effects would remain the same: debuffs that escalade to seizures, then strokes, then death.

Your describing a new mod at this point. Seeing how existing code base is a bit messy, that would be no easy feat to add such large design changes

Yeah, I had the same impression. And while I’m not a programmer myself, I know how much work one has to put into a mod to make it work. I won’t force you to add these ideas as features into the mod, and since I’m the only one who proposed them, it would be more logical for you to focus on other suggestions and mods that received more support from the community. I’ll still keep my ideas here, in case someone (you or anyone else) wants to use them as inspiration for the mod or an addon.

The Cerebral cortex level seems superfluous, consider flattening the structure

I separated the cerebral cortex into its four areas because together they have quite a lot of corresponding implants, and regrouping them in one category would not leave enough room (only 4 slots) to really do much. Maybe we could keep each area in its own category, but remove the cerebral cortex level?

Flattening doesn't mean regrouping into a single category. ;)

Flattening doesn't mean regrouping into a single category. ;)

Oh, right, my bad. So we just remove the cerebral cortex level, this way its constituent levels are at the same level as the limbic system and the hindbrain. Yeah, sounds better this way :)