Interoception: the hidden sense that shapes wellbeing
rael-science
Interoception: the hidden sense that shapes wellbeing
If
you’re sitting in a safe and comfortable position, close your eyes and
try to feel your heart beating in your chest. Can you, without moving
your hands to take your pulse, feel each movement and count its rhythm?
Or do you struggle to detect anything at all? This simple test is just
one way to assess your “interoception” – your brain’s perception of your
body’s state, transmitted from receptors on all your internal organs.
Interoception
may be less well known than the “outward facing” senses such as sight,
hearing, taste, touch and smell, but it has enormous consequences for
your wellbeing. Scientists have shown that our sensitivity to
interoceptive signals can determine our capacity to regulate our
emotions, and our subsequent susceptibility to mental health problems
such as anxiety and depression.
It is now one of the fastest moving areas in neuroscience and psychology, with academic conferences devoted to the subject and
a wealth of new papers emerging every month. “We are seeing an
exponential growth in interoceptive research,” says Prof Manos Tsakiris,
a psychologist at Royal Holloway, University of London.
Importantly,
these findings include promising new ways for you to “tune in” to the
body and alter your perception of its interoceptive signals – techniques
that may help treat a host of mental health problems. It is only by
listening to the heart, it seems, that we can take better care of the
mind.
The origin of emotion
First,
some definitions. Interoception includes all the signals from your
internal organs, including your cardiovascular system, your lungs, your
gut, your bladder and your kidneys. “There’s a constant communication
dialogue between the brain and the viscera,” says Tsakiris.
Much
of the processing of these signals takes place below conscious
awareness: you won’t be aware of the automatic feedback between brain
and body that helps to keep your blood pressure level, for instance, or
the signals that help to stabilise your blood sugar levels. But many of
these sensations – such as tension in your muscles, the clenching of
your stomach, or the beating of your heart – should be available to the
conscious mind, at least some of the time. And the ways you read and
interpret those feelings will have important consequences for your
wellbeing.
“Researchers
and clinicians are recognising interoception as a key mechanism to
mental and physical health, where understanding our body’s signals helps
us understand and regulate emotional and physical states,” says Dr
Helen Weng at the University of California San Francisco.
This
idea stems from the pioneering work of Prof Antonio Damasio at the
University of Southern California in the 1990s. He proposed that
emotional events begin with non-conscious changes in bodily states,
called “somatic markers”:
when you see an angry dog, for instance, and your muscles tense or your
heart begins to race. This physiological reaction occurs before you are
even aware of the emotion, and it is only when the brain detects the
alteration to the body’s internal state, through interoception, that we
actually experience the feeling and allow it to shape our behaviour.
Without the back-and-forth between the brain and the body, the feelings
of happiness, sadness or excitement wouldn’t exist.
Interoception lies behind our sense of intuition – when something feels “right” or “wrong” without an explanation
As
evidence, Damasio described the decision making of patients suffering
damage to areas such as the ventromedial prefrontal cortex, which
disrupted the creation of those unconscious bodily reactions. If they
saw a photo of a horrific car crash, for example, they did not have the
slightest physiological response – and this was accompanied by a lack of
any emotional feeling either. They reported knowing that they should feel
shocked or disgusted, but they didn’t actually experience the feelings.
Importantly, the impaired interoception and emotional awareness also
disrupted their decision making, meaning that they struggled to cope
with the simplest choices, such as what meal to pick on a dinner menu.
This suggests that our interoception lies behind our sense of intuition,
when something just feels “right” or “wrong” without us being able to
explain why.
We
now know that many other people – without any kind of brain damage –
struggle to tune in to their interoceptive signals, and this can be measured through various exercises.
You can ask subjects to count their heartbeat over a minute, for
example, and then compare that with the actual reading. Or you can play
recordings of a regular beat, and ask the participants to say whether it
is in sync with their own heart or not. You can also measure
interoceptive awareness with questionnaires that ask people how often
they notice their body’s signals.
In each case, individuals show a spectrum of responses, which seem to be related to their ability to recognise and regulate their
emotions. It makes sense: if you are more adept at accurately detecting
your bodily signals, you will be able to form more nuanced
interpretations of your feelings about a situation, and this in turn
should help you to make wiser choices about the best ways to respond.
Such processes may play an important role in many mental illnesses. A large subgroup of people with depression, for example, often show poorer interoceptive awareness on the heartbeat detection tasks,
and, for these patients, the reduced ability to feel their bodily
signals may lie behind their sense of lethargy and emotional numbness –
the sense that they can “feel nothing” at all.
People with anxiety, in contrast, do report being attentive to their interoceptive signals –
but they don’t necessarily read them accurately. They may misinterpret a
small change in heart rate as being much bigger than it really is, for
example, which can lead them to “catastrophise” their feelings and
amplify their sense of panic.
Prof
Hugo Critchley at Brighton and Sussex Medical School points out that
poor interoceptive awareness can also lead to the sense of
“depersonalisation” and dissociation, which are early symptoms of
psychosis and may be a precursor of their delusions. Interoception helps
us to form our most basic sense of self, he says – and it seems to be
askew in these patients.
New therapies
Therapies
that aim to address these problems are still in their infancy, but the
early signs are promising. Critchley recently worked with 121 autistic
adults – a group known to be at high risk of anxiety disorders – to see
if improved interoception could reduce their feelings of stress. Over a
course of six sessions, half the participants were given repeated
attempts at the heartbeat detection tasks followed by detailed feedback
on their performance. Those in the control condition, meanwhile, took
part in voice recognition training, which was designed to help them
detect the emotional overtones of people’s speech – a task that could
well be useful in their lives, but which did not specifically target
their interoceptive awareness.
Reporting their results in the Lancet earlier this month, the team found that the interoceptive training group showed markedly lower incidence of anxiety at
a three-month follow-up, with 31% completely recovering from their
anxiety disorder, compared with just 16% in the control group. “It
improved people’s ability to recognise and ‘de-catastrophise’ their
physiological experiences,” Critchley says. He tells me that his group
has seen similar benefits in a more diverse student population, though
that research has yet to be published.
Other
teams have been investigating the potential use of mindfulness to
improve people’s interoceptive awareness. There are many kinds of
mindfulness, of course – some of which may place more focus on the
mental experience and the appearance of thoughts. But Prof Cynthia Price
at the University of Washington in Seattle has tested a training
programme that specifically encourages participants to focus on the
internal sensations within sequential body areas.
Her
participants were people with substance use problems. The condition is
often accompanied by poor emotional regulation, which can make it harder
to avoid relapse – and, crucially, many people report a sense of
disembodiment that might contribute to their problems.
Price’s
results so far suggest that the therapy successfully reduces symptoms
of depression and cravings, and in one year-long study, it significantly increased abstinence,
compared with those undergoing the standard treatments. She hopes the
practice could be beneficial for many other people. “These skills should
be helpful for anyone, regardless of whether they have a health
condition.”
If you’re deconditioned from a lack of exercise, you’re more likely to experience symptoms associated with anxiety
Prof Hugo Critchley
These
are early findings, he emphasises, but if further research confirms the
benefits, it could be used during mindfulness exercises to train
people’s interoception, he suggests.With
time, it is possible that new technologies could ease this process.
Tsakiris, for example, has investigated a small non-invasive device that
clips to the ear and delivers a mild electric current, through the
skin, to the vagus nerve, which acts as a pathway between the gut, the
heart and the brain. In one experiment, Tsakiris found that the gentle stimulation increased people’s accuracy on one of the heartbeat detection tasks. “It seemed to strengthen the communication between the brain and the body; it opens up the bandwidth a little bit,” he says.
Inner strength
Perhaps
most intriguingly, the new awareness of interoception can help us to
understand why certain physical exercises can be so good for our mental
health. For one thing, regular workouts may change the nature of the
signals that your brain receives. “If you’re deconditioned from a lack
of exercise, you’re more likely to experience symptoms that you might
associate with anxiety,” says Critchley. “Your heart will race more when
you experience challenges – be it physical or emotional.” As you get
fitter, however, and organs such as the heart become more adept at
dealing with strain, your body will show a more resilient response to
changing circumstances – changes that could spill over into your
emotional wellbeing.
Equally
importantly, the practice of exercise should lead you to be more
attentive to those signals, so that you are also more accurate in
reading and interpreting the changes that you detect. “This doesn’t mean
that all athletes
have very high emotion regulation capacities,” Tsakiris warns. “But
they do have an advantage, precisely because their interoceptive system
is better attuned.”
“Interoceptive
feedback from the muscles can tell you something, unconsciously, about
what you can achieve in the world,” explains science writer Caroline
Williams, whose recent book Move! (Profile,
2021) explores the many ways that physical exercise can benefit the
mind. “After strength training, your body feels that it can cope, and
so, on some level, you feel a bit more in control of life.”It’s not just aerobic exercise that will help; increasing evidence suggests that strength training can particularly effectively reduce feelings of anxiety.
You might expect this to arise from the aesthetic improvements and the
ego-boost that comes from looking more toned – but the effects remain
even if you control for visible changes in muscle size. One potential
explanation is that the training somehow alters the interoceptive
signals we’re receiving from the muscles. By engaging with our muscles,
we feel physically sturdier and more capable to deal with threats – and
this bolsters our sense of self-esteem and mental resilience, too.
Interoception,
it seems, is one of our most important senses. And by paying a little
bit more attention to the signals it sends you, you may be healthier in
body and mind.
