The cross-section of a human brain model.iStockPhoto / Getty Images
Jacob Berkowitz is an author and playwright in Almonte, Ont.
On a hot, humid August afternoon in Milwaukee, Wis., I watch as neuroscientist Bill Cullinan demonstrates a craniotomy and brain removal. The anonymous donor’s cadaver is in a blue body bag on a stainless-steel gurney. Just the top of the skull is visible, scalp removed, face covered in a tightly cinched white cloth. Dr. Cullinan starts a small oscillating saw.
“There might be a bit of a smell,” he says as tiny, singed bone fragments are ejected when he energetically leans in and begins a semicircle cut around the forehead. A trio of undergraduate assistants, keen and calm, flip the cadaver. The professor continues his cut around the base of the skull. Two taps of a chisel, and he deftly pries off the top of the skull.
“If I tried to take the brain out now it would just rip apart in my hands,” Dr. Cullinan says to the horseshoe of gathered observers in the windowless anatomy lab. He severs the spinal cord and adjacent tissues. He pulls back the frontal lobes to reveal the two white, straw-diameter optic nerves entering the skull. His scalpel blade slices through them, the neighbouring carotid artery and a host of cranial nerves, completely freeing the brain from its tetherings. He turns toward us, the two hemispheres cupped neatly in his palms.
The web page for Marquette University’s Neuroanatomical Dissection Course: Human Brain and Spinal Cord calls it “provocative.” Before I left for what I called brain camp, this seemed like an odd word for a continuing-education course. Now I get it.
“I don’t think that anyone who’s never done this can walk away without a new appreciation of the brain,” says Dr. Cullinan, 62, his mop of grey-brown hair giving him a boyish quality to match his infectious neuroanatomy enthusiasm. He’s the dean of the university’s college of health sciences, yet every summer he still dons latex gloves to teach this unique three-day program he founded 25 years ago.
Every one of the 100 participants this year is trying to wrap their head around the endlessly perplexing nature of our grey matter. Many are clinical psychologists hoping that a deeper understanding of the brain’s structure will help them heal military veterans suffering from PTSD. There are physical therapists wondering how their stroke patients’ conditions align with damage to specific areas of the brain and spinal cord.
And there’s me, a 57-year-old writer. As I increasingly reflect on the nature of “self,” I hark back to my university biology days and the guiding rubric that function follows form. So I’ve come to the source to see, and touch, for myself.
On the first afternoon I put on latex gloves, a surgical mask and a thin, disposable plastic gown, then sit down at a stainless-steel dissection table across from Alice, a 70-ish clinical psychologist from California. It’s her sixth time. “There’s always something new to learn!” she says.
We’ve barely sat down when one of the undergraduate assistants delivers a stainless-steel tray with the right hemisphere of a donor’s brain. It’s been soaking in formaldehyde for a year, turning the Jell-O-like living brain into a friable, rubbery mass that makes dissection easier.
Belgian researcher Jeroen Schuermans holds a human brain, part of a collection of more than 3,000 brains that could provide insight into psychiatric diseases, at the psychiatric hospital in Duffel, Belgium.Yves Herman/REUTERS
Alice brusquely picks up the hemisphere and gives it a quick once-over. “It’s a nice one,” she says of the grey-pink mass. “I’ve got a bad brain,” a neighbour jokes, holding it up to show us. On the convoluted topography of the brain’s outer surface – the cerebral cortex – the bulges (gyri) are shrunken, creating enlarged gaps (sulci). “Probably dementia,” Alice says, noting the telltale sign.
I had expected to be surprised, maybe repulsed or emotionally moved at the thought of holding what was once someone’s mind. Instead I am wholly fascinated. As instructed by Dr. Cullinan, I use a metal probe and tweezers to remove the surface blood vessels and Saran Wrap-like lining. Simultaneously, I’m aware of an Escheresque quality to the experience: Here I am, a brain contemplating itself.
That morning, Dr. Cullinan presented a whirlwind overview of “the exquisite architecture of the brain.” Now that I’m holding half of one, I see that we tend to think of our brains as somehow unique. Yet the incredibly densely packed architecture between our ears is as shared as the anatomy of our 206 bones.
And what’s clear – once I’ve made a first cut – is that what we colloquially call our “grey matter” mostly isn’t. Our brain’s primary grey matter is a thin layer, no wider than a pencil, of densely packed nerve cell bodies that form the outer surface of the cerebral cortex. Below this is an expansive solid white mass – the network of axons, or neuronal extensions, that we’re referring to when we talk about how the brain is wired. They’re covered in white fat (myelin) insulation to prevent electrical impulses from leaking out on their way down an axon. Some are really long – just two axons connect the motor region of your cerebral cortex with your little toe.
Probabilistic tractography of several white matter bundles derived from diffusion-weighted images. Data from the Human Connectome project.Luis Concha/INB-UNAM/Handout
Our goal on this first day is to reveal the primary axon highways, fibre tracts that internally wire regions of the brain and continue to the rest of the body. On the outer side of the hemisphere, I use the blunt end of a scalpel to pull away chunks of tissue until I’ve revealed a fibre tract that runs from the frontal lobe and makes a hairpin turn into brain regions behind the ear. It’s a high-bandwidth link literally connecting thoughts and the language to express them. Eventually we reveal the corona radiata, a peacock’s tail of axons that carry the bulk of information traffic – movement, sensations – into and out of the cerebral cortex and descend to form the spinal cord.
“When you’re done, just leave everything and go,” Dr. Cullinan says over the cacophony of discussion. Our dissection tray contains chunks and slices of preserved brain, resembling something between pulled pork and turkey. I notice that the lab instructors’ gloves are speckled with brain bits. That morning, out of respect for the enormous generosity of the anatomical donors, Dr. Cullinan said, “The lab is hallowed ground.” There was a sense of the sacred, yet not like any I’d experienced before.
We graduate to the evening social. “Oh, I thought of staying at the Ambassador Hotel,” says Connie, a 30-something physiotherapist. “But then I read more reviews. That’s where Jeffrey Dahmer killed one of his first victims.” I sip my IPA, laugh and say that it doesn’t bother me that I am staying in the former haunt of the serial killer dubbed the Milwaukee Cannibal.
At 2 a.m. I wake to pee. Before I swing my legs off the hotel bed, a name pops into my consciousness: Jeffrey Dahmer. Anxiousness wells up in me as I walk in the dark to the bathroom. I reason with myself: Relax. Lying back in bed, I close my eyes and in a moment am startled upright by the sound of the room’s door handle being tested. Heart pounding, I switch on a light and secure the door’s additional bolt and chain.
It is as if my brain is preparing me for the day’s descent into the unconscious. The next morning, Dr. Cullinan and his colleagues introduce us to the structures at the centre of the brain. There’s a lot of popular buzz about some bits of this three-dimensional terrain, such as the amygdala, which plays a central role in processing feelings, including alone-in-a-hotel-room fear. But straight behind each eye, beginning at about the temple, is a group of unsung structures, the basal ganglia. They program and plan all our movements, from riffing fingers on a guitar fretboard to an NHL goalie’s seemingly superhuman glove save of a puck moving at 160 kilometres an hour.
Consciousness is the very tip of the great brain iceberg. Almost all of the axonal bundles I uncovered the day before flow through and are integrated in the basal ganglia in a great, constant internal dialogue. Yet we’re consciously aware of only a puny 0.01 per cent of this neuronal conversation.
“You are really not in control of yourself as much as you think,” Marquette neuroscientist SuJean Choi says during a presentation about the neuroanatomy of perception. She shows a 30-second video of TN, a famous patient who’d had a massive stroke that destroyed much of his visual cortex, a region at the back of the head. Yet, asked by a physician to walk a hallway obstacle course, he shuffled left around a box, then sidestepped right past a chair. Why did he choose that route? “I don’t know,” he replied. TN had cortical blindness and, even with no conscious awareness of seeing, his basal ganglia structures were still processing visual information unconsciously and passing this on to his motor cortex.
We look at insects, birds or a pet and see instinctual behaviour – mating, eating, fighting, parenting, playing. In ourselves, we think of this as deliberate. We delude ourselves. We are animals for whom the vast bulk of our actions are instinctual, driven unconsciously by the thousands of components of the vast integrative system we call our brain.
Brain magnetic resonance imaging (MRI) scans provide detailed images of brain tissues and structures for medical diagnosis of some brain-related conditions, such as dementia and multiple sclerosis (MS).iStockPhoto / Getty Images
It’s an astounding system we usually don’t notice until, as with TN, it breaks down. Parkinson’s disease, Dr. Cullinan tells us, involves the death of cells in the basal ganglia that produce the neurotransmitter dopamine. As a result, these brain areas can’t accurately regulate motion, resulting in the uncontrolled movements of what was originally called the shaking palsy.
That afternoon in the lab, Alice’s friend Bonnie, a retired nursing professor and the third in my dissection trio, holds an object like a bread knife and makes thin lengthwise slices of a brain, starting laterally, to gradually reveal the structures of the basal ganglia. There’s the caudate process, a beautiful, glistening organ that looks like a diving porpoise, its head abutting the delicate putamen, a baguette-shaped structure that stretches back to the super-dense oval thalamus, through which flows every sensory axon except those of smell.
Visiting my 83-year-old dad the weekend before, I was struck by his much more pronounced Parkinsonian tremors. Sitting on his deck overlooking Lake Ontario, he’d wanted to talk about how I felt about our relationship and my childhood. These were topics that, when I’d previously broached them, had elicited a stony silence from him. Another participant in the dissection course, whose father also has Parkinson’s, tells me that these affective changes are a lesser-known part of the disease – not just involuntary shaking, but involuntary emotional transformation. The experience is still disorienting, as I wonder who my father really is if the death of basal ganglia cells has so profoundly, achingly, changed the man I knew.
After the craniotomy, we return to our lab tables for a last time to dissect what are often referred to as the reptilian or evolutionarily ancient parts of the brain located at the base of the skull. These brain stem structures co-ordinate all our vital functions – the rhythm of the heart, breathing – and the remarkable interplay of postural muscles that, without a thought, enable upright balance.
At the base of the brain stem, I start cutting thin slices. In one piece, we realize that the faint, almost gentle (though the term doesn’t make anatomical sense) X-shaped white striations are axon bundles crossing from left to right and vice versa. It’s why each brain hemisphere operates and senses the opposite side of the body – why a stroke in the right motor cortex paralyzes parts of a person’s left side.
“Geez, you’ve got to wonder how, or who …” Bonnie says, her voice trailing off as she absorbs the elegance of what we’re seeing.
I share her sense of wonder, in a firmly evolutionary sense. I’d come to brain camp seeking greater understanding and leave changed in more complex ways. I look in the mirror the next morning, and it’s as if I’m looking through my face, behind my nose, and seeing my two olfactory bulbs, their fibre stalks tucked neatly into a sulcus on the bottom of my frontal lobe. I see the great illusion of the expression “brain and body.” The brain is body. The mind-body connection is a great misnomer: Mind, conscious and unconscious, is body, just as much as a left toe.
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