The Shape of What’s Happening

When a blind person uses a cane, something strange happens in their brain. The neural map of their body (the internal model that tracks where they end and the world begins) updates to include the cane. The tip of the cane, rather than the hand gripping it, becomes the point at which the body meets the world. This isn’t metaphor. It’s measurable. Neurons in the parietal cortex that encode the body’s reach literally expand their receptive fields to include the length of the tool. After enough use, the cane stops being an object the person holds and starts being part of the person. 

Neuroscientists call this the body schema, and its most interesting property is that it isn’t limited to physical extensions of the body. As David Eagleman describes in Livewired, the same mechanism extends the self into prosthetics, into instruments a musician plays for long enough, into the car someone drives well, into the people they love. Anything the brain learns to predict the behavior of reliably enough becomes, at the level of neural representation, partly incorporated into the self. When you know someone well enough (their rhythms, their moods, their likely responses), your sense of who you are begins to include them. Close relationships, in the language of the research literature, involve what psychologists call “inclusion of other in the self.”

I’ve been thinking about this framework lately because someone I love is living through the early stages of Huntington’s disease, and what’s happening to them is also happening, in a smaller but real way, to me.

Huntington’s disease is a neurodegenerative genetic disorder that typically begins in a person’s thirties or forties. It progresses over years or decades, eventually affecting movement, cognition, and personality. Chorea – involuntary writhing or twitching movements – is the symptom most people associate with it, but the cognitive and behavioral changes often arrive first and do more to reshape who a person is. Irritability, impulsivity, loss of emotional regulation, difficulty with the kinds of thinking that let someone plan, adapt, and be in relationship with others. Each person gene-positive for HD has a fifty percent chance of passing the gene to each of their children, and every person who carries the expanded gene will eventually develop the disease. There is currently no cure and no treatment that meaningfully slows its progression.

If the self extends into the people we love through the same mechanism that extends it into canes and instruments (by learning to predict them reliably enough that their behavior becomes part of our own ongoing model of the world), then a disease that progressively dismantles someone’s predictability does something specific to the person who loves them. It doesn’t just cause grief. It contracts the self. The parts of you that were constituted through interaction with your person’s intact mind, their particular way of thinking and feeling and responding: those parts lose their substrate as the disease advances. You don’t stop loving them. You lose pieces of yourself that were built from loving them, because the person you were loving is changing in ways that make those pieces no longer fit who’s in front of you. 

There’s a second mechanism operating at the same time, and it’s the part that makes HD caregiving structurally different from most other forms of love under pressure. While the self contracts where the intact person used to be, it also grows in a different direction. The disease’s expressions: the chorea, the changed rhythms, the irritability that wasn’t there before, the new ways your person’s mind moves, become predictable in their own right. The brain that built its model of the beloved around who they were now builds model-structure around who the disease is making them into. That new structure is real. It lets you anticipate their needs, adapt to their moods, meet them where they are on a given day. It’s love operating on updated information.

This is not love becoming something else, but rather, continuing to do what love does, while the person you love is changing. The self-extension mechanism doesn’t have a setting for “pause incorporation while the beloved is ill.” If you’re present with someone day after day, and their behavior has patterns you can learn, you will learn them. The learning itself is still love, and the structure that learning builds is still part of you. 

What this produces, over time, is a caregiver whose sense of self contains both a contracting space where the intact partner used to be and a growing space organized around disease-expressions. Both are real self-structure. Both are shaped by love. The first is unambiguously grief-laden. The second is more complicated, because it’s functional adaptation that lets you continue to love someone whose accessible self has changed, but it’s also self-structure that couldn’t exist without the disease. Loving someone whose expressions are increasingly shaped by Huntington’s means having those expressions absorbed into your sense of who they are, which means absorbed into your sense of who you are in relation to them. This is not a failure of love. It’s what the mechanism produces when the thing it’s built to do runs into a condition it can’t stop doing.

For some caregivers, the self-extension problem compounds in a particular way. They are gene-positive themselves, watched a parent go through Huntington’s, and know the shape of what’s coming. Some have already started noticing the early signs in their own bodies and minds: the slight changes in coordination, the new difficulty with emotional regulation, the cognitive hitches that might be early symptoms or might just be ordinary aging. These caregivers aren’t only watching their loved one change. They are watching, in their loved one, a preview of what their own self will become. And the self that is doing the watching is already quietly restructuring in anticipation of the future restructuring it knows is coming. The grief isn’t only about who the beloved is becoming. It’s also about who the caregiver will become, and about the caregiver’s children who will eventually watch them go through what they are now watching.

The self-extension mechanism, under these conditions, is running in multiple directions simultaneously. Incorporating the beloved as they change. Anticipating the caregiver’s own change. Pre-grieving the pieces of self-structure that the caregiver’s children and partner and friends will lose when the caregiver’s own disease advances.

All of this happens in the same person, at the same time, with no way to disentangle the threads.

For adult children watching a parent decline, a related compounding occurs. Their self-concept is still being constituted through the parent in some ways, even well into adulthood. Parents remain reference points for the self long after childhood ends. The parent’s decline contracts that reference structure. At the same time, every adult child of a gene-positive parent has a fifty-percent chance of carrying the gene themselves. If they’ve tested positive, they are watching their own future. If they’ve tested negative, they carry survivor guilt. If they haven’t tested, they are living with the unresolved question folded into every observation of their parent’s symptoms. All three configurations involve self-structure being built around a future version of the self whose status depends on a genetic test that either has been taken or hasn’t.

And there’s something specific about Huntington’s that makes all of this harder. HD doesn’t just impair memory or movement. It changes personality. It affects the parts of the brain that handle impulse control, emotional regulation, empathy, and the capacity for the subtle give-and-take of close relationships. The caregiver’s extended self wasn’t only built around the beloved’s cognition. It was built around specific emotional features: their particular warmth, their humor, their way of attending to the caregiver in return. When those features change, the caregiver loses pieces of self-structure that were constituted specifically through the beloved’s emotional reciprocity. This is different from caring for someone with a stable cognitive disability, or someone whose core personality remains intact while their memory fails. It’s different enough that caregivers in the HD community often describe experiences that existing frameworks don’t fit. The self-extension framework predicts exactly this difference. The structures being dismantled are the structures the disease specifically targets, and Huntington’s targets the features that make close relationships possible. 

What the self-extension framework offers, for any of these configurations, is mostly just language. It doesn’t change the trajectory of the disease. It doesn’t make caring for someone with Huntington’s less exhausting, less grief-laden, or less expensive in ways that matter. It doesn’t prevent the specific cruelty of watching your person’s personality change, or of knowing your own is coming, or of seeing in your parent what your children may someday see in you. These are features of HD that no framework can touch. 

But there’s a kind of help that comes from being able to name what’s happening to you with enough precision that your experience stops feeling shapeless. If you’ve had the sense that something more than grief is happening, that the usual words for caregiver burden don’t quite describe what you’re living through, that parts of you seem to be disappearing while other parts are growing in directions you didn’t ask for, the self-extension framework is one way to describe why that’s so, and why it’s so hard. And this is worth saying out loud: it isn’t something wrong with you. It’s love continuing to do what love does, under conditions that love wasn’t designed for.

The person I love is gene-positive and symptomatic. Their parent died recently, with HD as a contributing factor. We live far apart more often than we’d like, and I am already feeling pieces of myself reshape themselves in response to what’s happening. I am not a caregiver in the way that many readers of this essay are caregivers. But the framework applies to me, and to anyone who loves someone going through this. That’s part of what I wanted to say. The other part is that if you’re reading this and you’ve been living with something you couldn’t quite name, the thing you’re living with has a shape. Being able to see the shape doesn’t make it smaller. It might make it easier to carry.

Sources

The cane example and the tool-extension of body schema are from Maravita and Iriki (2004), “Tools for the body (schema),” Trends in Cognitive Sciences 8(2), 79-86. The broader framework of self-extension into tools, prosthetics, and environments is developed in David Eagleman’s Livewired: The Inside Story of the Ever-Changing Brain (Pantheon, 2020). The “inclusion of other in the self” principle was articulated in Aron, Aron, Tudor, and Nelson (1991), “Close relationships as including other in the self,” Journal of Personality and Social Psychology 60(2), 241-253, and remains a foundation of contemporary self-expansion research.

The analytical framework and editorial direction here are mine; drafting assistance from Claude (Anthropic).

This article was written by one of our volunteers, Nathan Curfiss, and it is based on his personal experience.