Sleepy brains neglect half the world

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alertness, attentional deficits, bodily sensations, damage, drowsiness, frontal lobes, hemispatial neglect, parietal lobes, right hemisphere, sights, sleep, sounds, space, spatial awareness, stroke, visual field, visual neglect

Sleepy brains neglect half the world

Damage to certain parts of the brain can lead to a bizarre syndrome called hemispatial neglect, in which one loses awareness of one side of their body and the space around it. In extreme cases, a patient with hemispatial neglect might eat food from only one side of their plate, dress on only one side of their body, or shave or apply make-up to half of their face, apparently because they cannot pay attention to anything on that the other side.

Research published last week now suggests that something like this happens to all of us when we drift off to sleep each night. The work could help researchers to understand the causes of hemispatial neglect, and why it affects one side far more often than the other. It also begins to reveal the profound changes in conscious experience that take place while we fall asleep, and the brain changes that accompany them.

Hemispatial neglect is a debilitating condition that occurs often in people who suffer a stroke, where damage to the left hemisphere of the brain results in neglect of the right half of space, and vice versa. It can occur as a result of damage to certain parts of the frontal lobes, which are involved in alertness and attention, and the parietal lobes, which process information about the body and its surrounding space.

In clinical tests, patients with hemispatial neglect are typically unaware of all kinds of stimuli in one half of space – they fail to acknowledge objects placed in the affected half of their visual field, for example and cannot state the location of touch sensations on the affected side of their body. Some may stop using the limbs on the affected side, or even deny that the limbs belong to them. Patients with neglect can usually see perfectly well, but information from the affected side just does not reach their conscious awareness.

In 2005, researchers at the MRC Cognition and Brain Sciences Unit in Cambridge reported that reduced alertness dramatically alters spatial awareness in healthy people by shifting attention to the right so that they neglect visual stimuli to the left. To investigate further, they recruited 26 more healthy participants and tested their spatial awareness while they fell asleep.

To do so, they took the participants one by one into a dark room and told them to sit back in a comfortable reclining chair and relax. They recorded the participants’ brain wave patterns using electrodes attached to the scalp, and measured their reaction times, to determine exactly when they started getting drowsy, then played sounds to either their left or right, and asked them to indicate which side each one came from by pressing one of two buttons.

Again, the researchers saw that reduced alertness caused a rightward shift in spatial attention. During the few moments of drowsiness just before falling asleep, the participants consistently mislocated sounds played to their left, and said that they had been played to the right.

“This is an exciting development,” says Masud Husain, a clinical neurologist at the University of Oxford who studies neglect in stroke patients. “It suggests that while falling asleep the healthy brain behaves in a similar way to stroke patients who have difficulty keeping alert.”

The findings further suggest that the attentional deficits associated with hemispatial neglect apply to sounds as well as to sights and bodily sensations, and also provide clues about why, in the vast majority of cases, neglect only persists after damage to the right hemisphere of the brain. “Both groups appear to have particular difficulty attending to information to their left, consistent with the view that frontal and parietal regions of the right hemisphere play a key role in maintaining alertness.”

The study also provides clues about the brain mechanisms underlying neglect. “People don’t necessarily miss items on the left as they become more drowsy, but instead respond as if they had come from the right,” says Husain, “as if their perception of space becomes skewed to the right as their alertness declines.”

“The implication is that right hemisphere brain mechanisms that are crucial to representing space around our bodies also interact with processes that keep us vigilant and alert,” he adds. “The results are intriguing but need to be confirmed, perhaps with a more precise method than pressing buttons.”

Reference: Bareham, C. A., et al. (2014). Losing the left side of the world: Rightward shift in human spatial attention with sleep onset.Scientific Reports 4, doi: 10.1038/srep05092

Ways of seeing

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blindness, cane, disability, light adjustment, night vision, peripheral vision, retinitis pigmentosa, sight loss, visual field, visually impaired

Ways of seeing

Being different is bad. It’s a lesson most of us learn in the playground. Mercifully for society, it’s a lesson most of us go on to unlearn. But for some miserable unfortunates it sticks around. And, for me, it did more than stick. It got swallowed. It became physically part of me – like a filter, a lens through which I see the world.

When I was seven, my family moved to Tokyo. Mum enrolled me in a ballet class. We arrived at the dance studio to discover that none of the Japanese kids had ever seen a blonde girl before. I still have visions of that hall of mirrors, those armies of identical giggling ballerinas.

When I was 12, my family moved to Sydney. On my first day at school, the teacher asked me to stand in front of the class and tell them where I was from. So I did. Then she repeated my every word in a mock English accent. If I had to pinpoint the exact moment I learned my lesson, I’d say that was it. It was while living in Sydney that Mum began to notice I was having trouble seeing. I was always bumping into things – overhanging branches, toys left on the floor. Initially she found it funny, but after our first appointment with the ophthalmologist, she stopped laughing.

I was diagnosed with retinitis pigmentosa. It is a genetic disease that affects the parts of the eye that deal with peripheral vision, night vision and light adjustment. There is no way of knowing how quickly the condition degenerates into blindness. Some lose their sight before they turn 20 and some retain a small window of vision throughout their life. I was referred to a psychologist to help me digest the information and advised not to take my driving test. I was also advised to learn how to use a white cane.

In typical teenage fashion I told the psychologist where to stick it and reacted to the idea of a cane with such fury that my parents never dared raise the subject again. I would, quite honestly, have rather died than take a cane to school. Thankfully, I never had to. In fact, I didn’t have to tell anybody unless I chose to do so. My strategy of denial worked wonders – though I was terrible at netball. And most of the time I forgot I had a problem at all. Until I bumped into something. And then it would be a battle to hold back the tears.

I confided in my close friends and they took my arm as we strutted around Kings Cross on Saturday nights with our fake IDs. They led me into darkened pubs. They even helped me assess boys on dance floors using, as I recall, the terms: “hot”, “semi-hot” and “feral bush-pig”.

The enthusiasm with which these girls adapted to my strange disability was touching. And baffling. I never really understood why they didn’t just leave me at home.

But this happy arrangement was short-lived. I moved back to England for university and reverted to outright denial. I walked slowly and appeared vague. Fellow students thought I was permanently stoned, which was fine by me.

When I moved to London and began a career in television documentaries, I did everything I could to appear normal. Occasionally I’d miss a handshake and have no idea how to deal with it. It was the most stressful time of my life.

Today, aged 34, I have very little sight. While the average visual field spans 160 degrees, mine spans four degrees. I am registered blind with my local council. I know this sounds shocking. But it isn’t. I function pretty normally. I move my eyes around and get as much of the picture as I need. I’ve never been happier. I have a wonderful husband, a gorgeous two-year-old daughter and I love my work. The fact I bump into things a lot is very low on my list of worries.

I still don’t use a white cane. I’m not proud of this fact. I really ought to. I own one. It sometimes lives, folded up, in my handbag. I took it out for a spin the other day. I’d been inspired by comedian Adam Hills joking about the Paralympics on Channel 4.

I went back to Sydney recently. My friend Jane noticed my tinted glasses on an overcast day. “Are you wearing sunnies cause your future’s so bright?” she quipped.

Later, as we dined in Bondi, we were gossiping about a girl at school we had both admired. “She had something special. She had what you had,” said Jane. “What’s that?” I was taken by surprise. “I dunno,” said Jane, “She was from the outside. She was different.”

“Why do you think being different is bad?” asks Seema, a therapist who is helping me use my cane. “Some people love to be different.”

This makes me think of my Dad. When I was young, he would hold my hand and skip down the street singing in his native Italian. Mortified, I would beg him to stop. “For a girl who is so intelligent,” he would exclaim as I wriggled from his grasp, “you are emotionally stupid.”

Then I think of my tiny daughter. One rainy day, we were in a charity shop when she persuaded me to buy her a glittery snorkel mask. Later, as we walked through the downpour, she held her umbrella and wore that mask with such beautiful beaming pride that several strangers stopped to smile.

Seema explains that, when we are young, the lessons we learn can become embedded in our subconscious. They become almost physically part of us. Those feelings are deep and hard to shake – hard, but not impossible.

“Being different isn’t bad,” she says gently as we end our session. “Being different is a gift. It is something to be cherished.”