S2E6 SPOILERS - Chip Location: Continuity Error, or Clue
TL;DR at the end
I’m a neuroscientist and for whatever reason, I never paid much attention to any of the “science” behind severance because I assumed it basically boiled down to “unobtainium”, but after this episode where we got a really clear transverse view of Mark’s brain, and his chip location, I searched in the sub to see if it had been discussed before. I’m glad to see it has (in Helena’s case), but a lot of the speculation was, I believe, incomplete. But more to the point, things don’t add up in a way that might just be a screw up/artistic license, or it could point to a deeper coming reveal.First, I want to point out three general errors and unrelated continuity errors that might throw a wrench into this speculation, because maybe I’m looking too deeply into this.
First, when we get the two best views of Helena’s severance surgery, we get a glaring continuity error. After overlaying the images, you can clearly see that the location of the delivery syringe is not only coming in at a different angle, but entering the skull at a different place. Obviously, stirring around a long, thick, rigid needle in brain matter isn’t great for any future brain function, so we can chalk this up to unintentional continuity error. However, it does appear that the location the chip is eventually deposited is the same in both images.
Next, a general error. During Mark’s reintegration where Reghabi “drowns” the chip, we get a perfect transverse view of Marks brain, starting at the brainstem, and moving perfectly up to basically just superior to the lateral ventricles, all while using a handheld ultrasound device that she’s just holding to the back of his head.
Next, general error. When Reghabi does Mark’s reintegration surgery, she free hands a deep brain injection of a rather large chip with one hand, while navigating with the other hand with the ultrasound device, while she is having a panic attack and Mark’s head is free to move around. I perform surgeries basically identical to this all the time (not on humans) and whether on a human or animal, it requires a stereotactic injection surgery device that head-fixes the subject so they cannot move at all, and the syringe is guided by micromanipulators. Contrary to intuition, the types of stereotactic injection surgery devices used on humans need to be much more precise than the kind used on much smaller animals in research. As I mentioned in last night’s post episode thread, there's no hand steady enough to not completely make localized scrambled eggs out of the surrounding flan that is unfixed brain tissue without a stereotactic surgery device.
Now, I’m pretty sure I have a definitive answer for the location of Helena’s chip. The severance procedure creates several distinct, but related phenotypic effects.
Episodic Amnesia (lack of personal memories, but preservation of factual knowledge)
Contextual memory impairment (remembering a fact, but not remembering how you know it)
Spatial disorientation (says what it is, this isn’t explicitly states, but I have always noted that despite the floor plan not being insanely convoluted, everyone always needs explicit directions)
Affective dissonance (feeling emotions without a known cause)
These are all phenotypic effects that are associated with multiple brain structures (the amygdala assigning emotional valence to various stimuli, the parahippocampal cortex, entorhinal cortex, and hippocampus for spatial navigation, prefrontal cortex, entorhinal cortex for contextual memory, hippocampus as a whole for memory formation and recall)But, on top of that, there are several main integration hubs that connect and integrate information from these areas. However, Helena’s severance surgery is pretty cut and try. The chip is pretty clearly in the medial temporal lobe, exactly where the hippocampus is located. But where, exactly, in the hippocampus? It’s not a single homogenous structure; there are various regions and subregions where disruption would cause different effects. Luckily, I’m extremely confident that they took great care to show this shot of the chip in the exact right place. After overlaying a sagittal view map of major regions of the hippocampus onto her combined x-ray from earlier, the chip lies directly in the fimbria
Helena's unobstructed chip location with u/VanillaIsAFlavor's helpful red circle
Color coded image of hippocampall substructures, viewed sagittally. (Khan et al. 2015)
The fimbria is one major white matter highway leading out of the subiculum, the last outpost station out of the hippocampus before reaching subcortical regions (like the amygdala and prefrontal cortex) where that information is integrated with other information from those regions, and eventually fed back into the entorhinal cortex, to the dentate gyrus, and back through the rest of the hippocampus. Part of this feedback loop is what causes memory consolidation. The other major white matter tract is actually a separate layer of the entorhinal cortex, which goes up to various areas of the neocortex, where consolidated memory is stored long term, and sensory information is fed back down into the hippocampus.
Selective damage to the fimbria can cause all the things we see severance do (with a little Lumen magic)
So! It appears (in Helena’s case at least), the chip is disrupting the outflow of information from the hippocampus via the fimbria. Now comes the part that’s really interesting. Mark’s severance chip is not in the fimbria. It’s nowhere near the fimbria at all. It also appears to possibly be much larger, or at least in a different spatial orientation.
I’ve taken 9 frames from the ultrasound which depicts almost Mark’s entire brain, from the brainstem basically starting at the base of the cerebellum, all the way up to the superior-most point of the scan. Mark’s chip extends from basically the top half of the lateral ventricles (subcortical region), up beyond them into the neocortex. It’s also very clearly in a large white matter tract, adjacent to the cingulate gyrus, called the cingulum bundle.
Again, Mark’s chip extends from the subcortical inferior cingulum bundle all the way up to the posterior cingulum bundle. This is an insanely integrated superhighway. It connects the hippocampus, the entorhinal cortex, the amygdala, the prefrontal cortex, the anterior cingulate cortex, and the parietal cortex, together with the post cingulate cortex, in a hyperconnected circuit. It’s disruption can cause, you guessed it:
Episodic amnesia, contextual memory deficits, affective dissonance, loss of self referential memories, impairment in ability to be confident in recalled memories, and also, interestingly enough, apathy and blunted affect (maybe that hasn’t all been created by the loss of his wife 2 years ago)
So, this could definitely be a continuity error, or an artistic choice (like it looks way cooler to look at the brain from bottom to top in transverse slices, than showing the same sagittal view we saw with Helena), or it could be hinting that Mark is important for more than just his relationship to Gemma. Could Mark have been severed in a different, possibly more dangerous way? A way that maybe only worked on him, or was only suitable for him for some reason?
I think there are two main reasons to accept that this is intentional. First being, they are both locations where selective alteration to signaling could lead to similar outcomes. Second, the fact that they are both white matter tracts.
(Digression)
In a “spherical” archetypal neuron, they have three parts: the cell body where the genetic material is and where the metabolism happens, the axon that the outgoing action potential leaves through, and the dendrites where axons from other neurons synapse onto to communicate with other neurons. The grey matter of the brain is where neuron’s cell bodies are, usually in layers of the cortex or unified brain regions like the thalamus, amygdala, what have you. It’s where the processing part happens because neurons are relatively densely packed and their axons only reach fairly proximally to neighboring neurons. Because the axons are so short, and so thin, they don’t need any myelin to “insulate” the wires. White matter, for all intents and purposes, has no cell bodies in it at all. All it is, is basically thick cables of myelinated axons that send long range signals between distal brain regions.
(End digression)
The fact that both severance chips are in white matter tracts that transmit data to different regions of the brain so it can be integrated and utilized, AND both of those white matter tract regions can be targeted for severance effects, not only lends credence to the fact that it’s intentional, but it informs us about how exactly the chips work, and it weirdly makes sense. A single, small chip, placed in a single brain structure, will have very limited fine-tuned control over creating the type of exact alteration of experience that we see happening. Even if it’s in a nucleus or subregion considered a “hub” of integrating information, the connections to, from, and between different brain regions are so recursive and convoluted, that altering neuronal firing patterns in that grey matter region so data is processed in that region differently, would likely not create something as cohesive and “flawless” as the effect we see in severance. However, in white matter tracts, there are many many many thousands of axons projecting from and to an entire circuit's worth of larger brain regions and nuclei within those regions, and they are incredibly compact for how many axons there are. By placing the severance chip into the white matter tract, and then selectively altering the action potentials coming through (either by blocking them, increasing their amplitude, or altering their frequency) all the chip has to do is modify the signals being passed to each brain region in the larger circuit, and then let those regions process the incoming signal the way they would naturally do if they organically had received that signal. That way, the experience of severance can be tightly controlled, while still letting the larger unified experience of selfhood in the moment persist.
I’ll end with this. After this last episode, I’m pretty firmly on the “Rehgabi works for Lumen still” train. I don’t think she was scared because she was worried Mark would die, I think she was scared because she was worried Mark would die, and she’d get in crazy trouble from her bosses for it. Listen to the way she tantalizes Mark with how Gemma is her old self. It’s the Gemma he knows. And they can be together. Either she’s an actual bad actress IRL, or she’s playing a character that’s a bad actress, really well. Gemma’s not coming back, but Lumen needs him to think she can. And I think Reghabi sent Helena to the chinese food restaurant to intentionally antagonize Mark into accepting the accelerated reintegration.
TL;DR
Maybe its a continuity error, but Helena and Mark have their severance chips in completely different brain regions, that BOTH cause similar but distinct severance effects, and in both cases the chips basically achieve the effect the same way.