In her excellent book, The Grieving Brain, clinical psychologist Mary-Frances O’Connor describes loss as a “learning problem” for our brains. After death shatters our physical world, our mental maps also need to be rebuilt. This exhausting process takes time and energy, leaving us depleted and depressed.

Human attachment needs are wired into our brains. We need other people like we need food – to survive. Love nurtures and sustains us. Grief manifests as an unrequited type of love, a form of separation anxiety that we must learn to tolerate, eternally. Our brains need time to reconfigure in response to this frustrated, unmet need, to process the stark new reality.

As human children, separation anxiety emerges after we learn object permanence. That is, we learn even if objects or people move out of sight, they still exist. And as human children, we learn that separations consistently lead to reunions, at least eventually. These experiences embed themselves into our brains.

As a child, I attended elementary school. My beloved kindergarten teacher hugged me each morning. Each afternoon, I returned home in happy anticipation, confident that I’d see her again the next school day. Throughout my childhood, we visited my grandparents a few times a month. Whenever my family drove to my grandparents’ house, we saw them. Each time we called their landline, we either talked to them or left a message, and they’d call us back. Time and time again, I learned that distances can be bridged. Proximity was always possible. These types of repeated, routine interactions taught me that physical separations from our loved ones are merely temporary.

Initially, our loved one’s absence after death mistakenly resembles these more typical separations. But – no. Proximity isn’t possible. Death forces us to face a terrible new permanent change. Our loved one can’t be located. He’s gone, forever. He won’t return.

According to Dr. O’Connor, specific neurons in our brains activate when we encounter specific objects or people. She calls these “object cells.” Based on our experiences, our brain cells activate even in the absence of these objects — when we expect to see someone who is gone. That is, we respond to negative space – the non-appearance of our loved one. Dr. O’Connor calls these cells “object trace cells.” Object trace cells persist in firing until we have enough new experience so that we no longer expect to encounter our loved one.

This new learning takes time. The world feels disorienting and disturbing. We yearn for our person. Automatically, we may look for him – at the grocer’s, at the gym. We may listen for the sound of his car in the driveway and his key in the lock. Mindlessly, we may call out, “honey, are you home?”

Early in grief, I caught myself pretending my beloved had traveled for work. Repeatedly, I planned to tell him something he’d find interesting – then realized that he wasn’t here. Every morning, when I woke up alone in our bed, his absence struck me anew. Living without him felt incredible. Every day felt unbelievable, unnatural, unreal.

With enough time and enough experience, my brain seems to have rebuilt my mental map of the world. I no longer call out to him. The object trace cells no longer fire. But although my brain has adjusted, my heart hasn’t. There, his ghostly trace lives on.

To live on in hearts that love is not to die.