THE BRAIN

The brain controls all the body’s functions – from

consciousness and heart rate to thinking, memory

and emotion. It is the most complex thing we know of,

and the gaps in our knowledge about how it works are

vast. Neuroscientists have the daunting job of making

sense of this complicated organ – to provide insights

into our minds and behaviour and to find ways to

tackle debilitating brain diseases and injuries. Brain

injuries can occur in many ways, such as through

accidents, stroke or infections. The rehabilitation

group at the Medical Research Council Cognition

and Brain Sciences Unit in Cambridge specialises

in helping people with brain injuries to compensate

for cognitive problems and to cope with everyday life.

Its work includes developing new ways to measure

the problems faced by people with brain injuries and

developing new treatments. The scientists are also

interested in finding out more about how people

recover from brain injury and related memory loss.

The brain stem controls our core body functions –

the things our body must do unconsciously to keep us

alive, such as altering our heart beat and regulating

our blood pressure and body temperature. It also

controls functions such as alertness, swallowing,

digestion and breathing.

Consciousness is part of what makes each of us

unique. It encompasses many of our ideas, thoughts,

feelings, plans and memories. Conscious thought is

different from the unconscious workings of the brain

– which enable us to breathe, walk and talk and our

hearts to beat automatically. There are two aspects to

consciousness: awareness and wakefulness.

— Awareness refers to our internal, subjective

experience. It includes self awareness – the ability to

understand that you exist, as an individual, separate

from other people and with private thoughts. It also

includes awareness of the relationship between

oneself and one’s environment through use of our

senses and by thinking about ideas and acting upon

them using judgement.

— Wakefulness refers to different levels of

conscious awareness. Each day we experience a

spectrum of wakefulness, from full attentiveness, such

as if we are involved in an interesting conversation,

through inattentiveness, drowsiness and normal

sleep. Following some types of brain injury or during

anaesthesia people can’t be woken: they have a lower

level of wakefulness. Brain death lies at the far end of

this spectrum.

These two aspects of consciousness normally go

hand-in-hand; we don’t expect to have an interesting

conversation with someone who is asleep. However,

we can possess awareness when we are asleep, for

example when we dream.

Where does consciousness come from?

Scientists have amassed much evidence linking

different aspects of consciousness to our brain. We

now know that consciousness requires many parts of

the brain to work together. Parts of the cerebral cortex

act together to produce our thoughts and experiences.

A functioning thalamus is also required to produce

wakefulness – we know this because if a part of the

thalamus called the centromedian nucleus becomes

damaged, we become unconscious.

Unconsciousness can also be caused by

anaesthesia, or changes to the body’s internal

environment such as a rise or drop in core body

temperature or a lack of oxygen. A prolonged period

of unconsciousness is known as a coma. Sometimes,

after a severe brain injury, a person can enter a

vegetative state (VS). Unlike coma patients, VS

patients show normal wake/sleep cycles, but even

when they are awake they show no external sign of

awareness. When all electrical activity in the brain

stops irreversibly, this is known as brain death.

Scientists at the MRC Cognition and Brain

Sciences Unit in Cambridge study patients with

disorders of consciousness. Their work recently

revealed that a woman who was diagnosed as

being in a persistent vegetative state following

a car accident was aware of her surroundings.

Working with colleagues in Belgium, the scientists

used functional magnetic resonance imaging

(fMRI) to map the woman’s brain activity. She was

physically unresponsive and fulfilled all the criteria

for a diagnosis of vegetative state according to

international guidelines. But scans showed that her

brain responded to speech. Her brain also actively

processed the meaning of sentences, becoming

more active when she heard sentences containing

words with several meanings, like ‘rain’ and ‘reign’.

When asked to imagine playing tennis or moving

around her home, brain scans showed that the

woman could do this, activating various areas of her

brain in the same way as healthy volunteers. “These

are startling results. They confirm that, despite the

diagnosis of vegetative state, this patient retained

the ability to understand spoken commands and

to respond to them through her brain activity,” said

one of the researchers. “Her decision to work with

us represents a clear act of intent which confirmed

beyond any doubt that she was consciously aware of

herself and her surroundings.”

Doctors use different levels of sedation to reduce

people’s awareness of their bodies and surroundings.

For example, high levels of anaesthetic drugs cause

general anaesthesia: a complete loss of consciousness.

Another team of scientists at the MRC Cognition and

Brain Sciences Unit used fMRI to study how sedation

affects the brain’s processing of speech. Working with

researchers at the Wolfson Brain Imaging Centre in

Cambridge, they found that during heavy sedation,

volunteers’ brains still responded to the sounds of

speech but they were unable to process or remember

it. The findings have important implications for the care

of patients undergoing general anaesthesia or coming

out of a coma.

Available at: <http://www.mrc.ac.uk/publications/browse/the-brain-mrc- -research-for-lifelong-health/>. Retrieved on: 28 June 2016. Adapted. 

The verb “to flee” can be replaced by:

Can plants hear?

Flora may be able to detect the sounds of flowing water or munching insects