5 February 2022 | New Scientist | 47quo has an important impact on whether
that experience feels good or bad. This makes
it particularly relevant to mental health. If
feelings and emotions are built on bodily
sensations, perhaps errant bodily signals,
or the brain’s interpretation of them, are
feeding into feelings of emotional distress.
The challenge to unravelling all this is
that the brain-body pathways involved are
fiendishly complicated. The body is crammed
full of sensors, not to mention kilometres
of nervous pathways connecting the organs
to each other and the brain. Body and brain
communicate in both directions, each
responding to the other and tweaking things
as necessary. This cacophony is broadcast over
a huge range of timescales, from the rhythmic
beating of the heart over seconds to changes
in hormones and other chemicals in the
bloodstream over minutes or hours.
To make sense of all this information,
the brain employs a certain amount of
guesswork, taking mental shortcuts based on
past experiences. This predictive processing is
a leading explanation for how the brain works
in general: it involves making a best guess
based on what happened on prior occasions,
comparing that prediction with incoming
information from the senses and intervening
if there is a mismatch between the two.
Where this becomes relevant to mental
health is that people vary considerably, not
only in the predictions their brains make,
but also in their physiological sensitivity to
bodily changes and in the threshold at which
unconscious signals cross over into conscious
awareness. The way people respond to these
signals and the meaning they attach to them
plays out in many mental health conditions.
Take, for instance, anorexia, which has
the highest death rate of all mental health
conditions and is notoriously difficult to treat.
One aspect that is particularly hard to address
is the intense and unpleasant sensations of
having food in the gut after eating. “I’d be so
aware of the food inside of me that it would be
hard to walk... How could I move with all of this
in me?” says Susan Burton, who wrote Empty:
A memoir about her experiences of anorexia.
Sahib Khalsa, a psychiatrist at the Laureate
Institute for Brain Research in Tulsa, Oklahoma,
was intrigued by an anorexia patient who had
told him that spending time in a floatation
tank made this uncomfortable sensation go
away. “She felt that was the only place that
she could digest in comfort,” says Khalsa.Feel the beat
Our inability to tap into our body’s inner signals has
been implicated in poor mental health – but there are
ways to get back on track, finds Caroline Williams
L
YING in the dark, my senses are straining
for inputs and finding none. I am
floating in warm, salty water that is so
close to my body temperature, I can’t tell where
my body ends and the water begins. After a
while, my senses go quiet and my focus turns
inwards. Now, all I am aware of is my breathing
and the surprisingly loud beating of my heart.
I am inside a pod-like floatation tank
to try to boost my powers of interoception.
According to a growing body of research,
interoceptive sensations – those that originate
from within the body, from its tissues, organs
and chemicals circulating in the bloodstream –
hold the key not only to better mental well-
being, but to revolutionary new treatments
for common, yet hard-to-treat conditions like
depression, anxiety and eating disorders. With
several now in clinical trials, it is a change of
direction that could see the focus on the brain
alone in mental health become a thing of the
past, offering hope of progress for millions.
In recent years, it has become clear that
to really understand mental health, you need
to factor in just how much the brain cares
about what is going on below the neck. For
any animal, survival depends on how well it
can detect physical changes that may signal
a threat and to take appropriate action to get
things back on track. Interoception is a bit
like our sixth sense – the ability to detect thesebodily changes, from heartbeat to changing
concentrations of certain hormones in the
blood, as well as the psychological expression
of these as feelings and emotions. Integrated
by the brain, these changing bodily sensations
feed into our mental state and behaviour,
consciously or unconsciously, and have a
say in every thought and emotion we have.
“Interoception is fundamental to every brain
process and behaviour that there is,” says Hugo
Critchley, a neuroscientist at the University of
Sussex, UK, who studies the process.Under the radar
The reason that we generally aren’t cognisant
of this life-sustaining system is because
interoceptive messages are below the radar
of conscious awareness most of the time. They
can and do break the surface when something
needs to be addressed, motivating us to seek
out food when our stomach rumbles, or get
ready to run when we feel a rush of adrenaline.
Yet even when they are being detected at
the unconscious level, these signals can affect
the way we think, feel and behave. Some
scientists believe that the brain’s integration
and interpretation of them is what provides
the sense of self, that there is one “I” living in
this moment and experiencing the world in
real time, and that any change from the status>