How Your Brain Senses Touch Beyond the Body
You’ve probably had a similar experience to this: I’m holding a mixing spoon in my hand and I can feel how soft the butter is, and how crunchy the sugar is through the spoon.
Sensing touch through tools is not a new concept, though it has not been extensively investigated. In the 17th century, philosopher René Descartes discussed the ability of blind people to sense their surroundings through their walking cane. While scientists have researched tool use extensively, they typically focused on how people move the tools. They, for the most part, neglected the sensory aspect of tool use.
In a 2018 Nature study, cognitive neuroscientist Luke Miller and his colleagues at Claude Bernard Lyon 1 University in France reported that humans are actually quite good at pinpointing where an object comes into contact with a handheld tool using touch alone, as if the object were touching their own skin. A tool is not innervated like our skin, so how does our brain know when and where it is touched? Results in a follow-up study, published in December in Current Biology,reveal that the brain regions involved with sensing touch on the body similarly processes it on the tool. It is as if the tool is being treated like a sensory extension of your own body.
In the initial experiment, the researchers asked 16 right-handed subjects to determine where they felt touches on a one-meter-long wooden rod. In a total of 400 trials, each subject compared the locations of two touches made on the rod: If they were felt in different locations, participants did not respond. If they were in the same location, the people in the study tapped a foot pedal to indicate whether the touches were close or far from their hand. Even without any experience with the rod or feedback on their performance, the participants were, on average, 96 percent accurate.
During the experiment, researchers recorded subjects’ cortical brain activity using scalp electrodes and found that the cortex rapidly processed where the tool was touched. In trials in which the rod was touched in the same location twice in a row, there was a marked suppression of neural responses in brain areas previously shown to identify touch on the body, including the primary somatosensory (touch) cortex and the posterior parietal cortex.
There is evidence that when the sensory brain regions are presented with the same stimulus repeatedly, the responses of the underlying neural population gets suppressed. This repetition suppression can be measured and used as a “time stamp” to signify when a stimulus is extracted in the brain.
When the team tested some of the same subjects with touches on their arm instead of the rod, it observed similar repetition suppression in the same brain regions on similar time scales. The somatosensory cortex was suppressed in 52 milliseconds (about one twentieth of a second) after contact on both the rod and the arm. At 80 milliseconds, that activity suppression spread throughout the posterior parietal cortex. These results indicate the neural mechanisms for detecting touch location on tools are remarkably similar to what happens to localise touch on your own body.
Interestingly, after each contact, the rod vibrates for about 100 milliseconds. So by the time the rod has finished vibrating in the hand, you’ve already extracted the location dozens of milliseconds before that. The vibrations on the rod are detected by touch sensors embedded in our skin called Pacinian receptors, which then relays neural signals up to the somatosensory cortex. Computer simulations of Pacinian activity in the hand showed that information about rod contact location could be extracted efficiently within 20 milliseconds.
The vibrations on the rod may provide the key information needed for touch localisation. Repeating the same rod experiment, the researchers tested a patient who lost proprioception in her right arm, meaning she could not sense the limb’s location in space. She could still sense superficial touch, however, and she was able to localise where the rod was touched when held in both hands and had similar brain activity as the healthy patients during the task. That finding suggests quite convincingly that vibration conveyed through the touch, which is spared in the patient, is sufficient for the brain to locate touches on the rod.
Taken together, these results indicate that people could locate touches on a tool quickly and efficiently using the same neural processes for detecting touch on the body. While the scientists emphasize that no one in the studies thought the tool had “become part of their own body,” the work indicates that the subjects experienced sensory embodiment. That means that the brain repurposes strategies for dealing with objects by reusing what it knows about the body.
This comprehensive and thoughtful work could help inform the design of better prostheses because it suggests that insensate objects can become, potentially, ways of detecting information from the world and relaying it toward the somatosensory systems. This isn’t something that people in the world of prosthetics had previously thought about. But maybe this suggests that they should!
References
Luke E. Miller et al. Somatosensory Cortex Efficiently Processes Touch Located Beyond the Body. Current Biology, volume 29, pages 4276–4283, December 16, 2019.
Luke E. Miller et al. Sensing with tools extends somatosensory processing beyond the body. Nature, volume 561, pages 239–242, 2018
The result was striking. In people who had been to their in-laws, there was a decrease in all types of the Ruminococcus species of bacteria in the intestines. It is believed that this type of bacteria has protects against depression and psychological stress. The lower levels following the Christmas visit suggest that the bacteria were ‘used up’ in trying to buffer the person against the in-laws.
The team measured this CSF inflow going into the fourth ventricle, one of four fluid-filled cavities involved in producing CSF (by filtering blood plasma) and circulating it around the brain. As CSF usually flows out of the fourth ventricle, this suggests a “pulsatile” flow, like a wave. This pushes CSF around the ventricles and into spaces between membranes surrounding the brain and spinal cord, called the meninges, where it mixes with “interstitial fluid” within the brain to carry away toxic waste products.
Coffee beans themselves have little to no taste at all. The flavour, the aroma of coffee: it all comes from the roasting process which releases a large number of chemicals from the tiny bean. In fact, the average cup of coffee contains more than 1,000 chemicals. To transfer those delicious chemicals to the hot water in our cup, we run water over those roasted beans. To increase our success, we both grind the beans to increase their surface area (and thus more exposure of those chemicals to the water) and heat the water since higher temperatures (and thus energies) speed up the removal of molecules from a solid.
The practice of drinking coffee dates as far back as the 15th century. Although the growing the coffee plant likely originated in what is now Yemen, legend has it that the power of coffee was first realised by a goat herder in Ethiopia. The herder noticed that his goats became energised and had trouble sleeping after eating the beans.
1) Coffee lowers the risk of developing Parkinson’s disease: One study showed that drinking 4 to 5 cups of coffee a day cut the risk of developing Parkinson’s Disease in half (compared to drinking little or no caffeine). Another recent study found that drinking coffee actually lessened the effects of Parkinson’s among those who already had it.
4) Coffee is a great source of antioxidants: Antioxidants help our bodies combat cell damage. While fruits and vegetables are also great sources of antioxidants, studies show that our bodies may absorb them more readily from coffee.
Current recommendations suggest not surpassing 400 milligrams of caffeine per day (about 3 to 5 cups of coffee, depending on your brew of choice). Too much coffee, and thus caffeine, can lead to anxiety, increased heart rate, and a lack of sleep.
But this fact doesn’t tell us how flexible a new brain might be—or how large and complex an animal a single brain could control. After all, even Brontosaurus, 22 metres in length and weighing in at thousands of kilos had but one brain. Because understanding the brain’s limits might help us transcend them, it should come as no surprise that some of neuroscience’s moon-shot projects—from restoring movement after spinal cord injuries to operating robotic limbs with one’s mind—are focused on the limits of the brain’s flexibility. But how can we study these limits? It turns out that Key West’s expert mousers provide a hint.
The scientists found that each of the subjects’ six fingers were represented by distinct areas of the brain’s motor cortex. Consistent with these findings, the subjects had awareness of where in space all six fingers were, even when they could not see their hand. Finally, using a cleverly designed video game, the researchers showed that their six-fingered subjects could perform tasks with one hand that most people would need both hands to achieve. Together, these findings suggest that the brain is not hardwired for five fingers but could foreseeably represent as many digits as might appear on a body. For the trivia buffs out there, the living record for digits goes to an Indian carpenter, Devendra Suthar, with 14 fingers and 14 toes and, presumably, a most interesting brain.
For nearly 20 years Thomas Ollendick, director of the Child Study Center at Virginia Tech, has been testing briefer, more intensive forms of CBT for childhood anxiety disorders and getting results that closely match those of slower versions. His centre often has a waiting list for treatments that include a four-day therapy for obsessive-compulsive disorder (OCD) and a three-hour intervention for specific phobias (such as fear of flying, heights or dogs). Around the U.S. and Europe, short-course therapies for anxiety disorders have begun to catch on, creating a new movement in both adult and child psychology.
The details vary, but the quick treatments have some common features. They generally begin with “psychoeducation,” in which patients learn about their condition and the catastrophic thoughts that keep it locked in place. In Bergen, this is done in a small group. With children, the lessons may be more hands-on and concrete. For instance, Ollendick might help a snake-phobic kid grasp why the creature moves in a creepy, slithering way by having the child lie on the floor and try to go forward without using any limbs.
An obvious advantage to quick therapy is that it accelerates relief. Making these briefer therapies more widely available could help address the sad fact that only about a third of patients with anxiety disorders get any kind of treatment. A weeklong therapy could be completed over a school or work vacation. Sufferers in out of the way places who cannot find CBT nearby could be treated during a short out-of-town stay. The intensive approach requires special training and a big shift for therapists—and health insurers— accustomed to the tradition of 50-minute blocks. But is there really anything sacred about that when it’s the person’s best interest at heart?
The spiral into a bad mood may occur in a brain network that connects two key regions involved with memory and negative emotions, says psychiatrist Vikaas Sohal at the University of California, San Francisco. In a study he co-authored, published in November in Cell, Sohal says he was able to tell if someone’s mood was getting worse just by looking at whether this network was active or not.
If that’s right, doctors might figure out how to interrupt that cycle with deep-brain stimulation or electroshock therapy for people with major depressive and anxiety disorders. If this is the part of the brain that makes you feel bad, maybe you could reverse how that’s firing and get yourself to feel better….but it will be a long haul before this knowledge could be used in the clinical setting. However, for those of us in the psychotherpay and healing arenas, becoming aware of your triggering throughts and then shifting them is a great way to bypass this downward spiral.
In fact, every relaxation, calming or meditation technique relies on breathing, which may be the lowest common denominator in all the approaches to calming the body and mind. Research into basic physiology and into the effects of applying breath-control methods lends credence to the value of monitoring and regulating our inhalations and exhalations.
This power is evident in patients who have breathing difficulties. When these difficulties are sporadic and acute, they can trigger panic attacks; when they are chronic, they often induce a more muted anxiety. It is estimated that more than 60 percent of people with chronic obstructive pulmonary disease (COPD) have anxiety or depressive disorders. These disorders probably stem in part from concerns about the consequences of the disease (what could be more distressing than struggling to breathe?), but purely mechanical factors may contribute as well: the difficulty these patients experience often leads to faster breathing, which does not necessarily improve the quality of their oxygen supply but can aggravate their physical discomfort and anxiety.
Whether anxiety derives from breathing problems or other causes, it can be eased by a number of breathing techniques derived from traditional Eastern approaches (see “Six Techniques for Relieving Stress”). For example, “follow your breath,” an exercise that focuses attention on breathing, is one of the first steps in mindfulness meditation, whereas alternate nostril breathing comes from yoga. Combining reassuring thoughts with breathing is an approach incorporated into sophrology, a technique that emphasises harmony of body and mind and that borrows exercises from many approaches, including yoga and mindfulness.
Cardiac coherence’s stabilisation of the heartbeat can dampen anxiety powerfully. Conversely, patients with overactive heartbeats are sometimes misdiagnosed as victims of panic attacks because their racing heartbeat affects their mind.
In addition, paying attention to breathing causes most people to slow it down and to deepen it, which as I have mentioned, is soothing. Cognitive resources are limited, and so when individuals concentrate on breathing, they are not thinking about their worries. Those who practice mindfulness learn to notice when their attention drifts away from breathing and goes back to their concerns, and they train themselves to return periodically to their breathing. This refocusing has a relaxing effect on anyone and helps to combat ruminative thinking in people who have anxiety or depression, especially those who are particularly prone to negative thoughts that run in a loop.
These exercises may also help when insomnia strikes. In 2012 Suzanne M. Bertisch of Harvard Medical School and her colleagues reported, based on survey data, that more than 20 percent of American insomniacs do these breathing exercises to sleep better. They may be on to something. In 2015 Cheryl Yang and her team at National Yang-Ming University in Taiwan showed that 20 minutes of slow breathing exercises (six respiration cycles per minute) before going to bed significantly improves sleep. Insomniac participants went to sleep faster, woke up less frequently in the night and went back to sleep faster when they did wake up. On average, it took them only 10 minutes to fall asleep, almost three times faster than normal. The investigators attributed the results both to the calming mediated by the parasympathetic system and to the relaxing effect of focused breathing.
But why confine breathing techniques to negative emotions? It is also worth applying them during pleasurable moments, to take the time to appreciate and remember them. In short, one can pause and breathe for enjoyment as well as to calm down.
In the first condition, subjects focused on negative reappraisals of their ex-partner (eg, by responding to prompts about their ex’s annoying habits). In the second condition they were asked to reframe their loving feelings as less problematic (eg, by endorsing prompts such as ‘It’s okay to love someone I’m no longer with’). The last condition used distraction (eg, questions about the subjects’ favourite food) to get the participants’ mind off their heartbreak. The researchers found that only negative reappraisals were truly effective in reducing love feelings. However, doing so did increase feelings of unpleasantness.
Second, negative reappraisals should include not just our perceptions and memories of our ex but of the relationship as well. We tend to idealise the relationship just as much as we do the person and think almost exclusively of the good times and the happy moments. We are far less likely to consider the compromises we had to make, the fights that hurt our feelings or frustrated us, or our unmet emotional needs. People often grieve both the person and the relationship itself—the experience of being a couple, having a significant other, the companionship and partnering. Therefore, it is necessary to address idealised perceptions of the relationship by introducing negative reappraisals of our couplehood, as well as of our ex as a person, in order to more effectively reduce feelings of attachment and love.
One crucial aspect of recovery from heartbreak that was not covered in the current study is that breakups leave all kinds of voids in our lives. Our social circle gets diminished, our activities change, our physical space changes (eg, their ‘stuff’ is no longer there), some of the things we did as couples we no longer do, and the list goes on. A significant part of the emotional pain we feel after a breakup is related to these other losses, the ripple effects that go beyond the loss of the actual person. Finding ways to recognise these voids and fill them is an important task of recovery from heartbreak and one that is often neglected.
