Think Smart: A Neuroscientist's Prescription for Improving Your Brain's Performance (10 page)

The final
sensory exercise involves body position and body shape:
changing what neurologists refer to as the
body schema.
In simple language, this term refers to the implicit knowledge that we all retain about the spatial properties of our body. For example, we’re able to pass people on a narrow sidewalk without bumping into them because we quickly and unconsciously estimate the available space separating our arms and shoulders from them. We can do this because over the years our brain has built up a dynamic internal representation of our body and its extension in external space—in essence, the body schema. It’s the integrity of our body schema that enables us to successfully return a tennis serve or sink that final putt during a hotly contested golf match.

Thanks to its dynamism, our body schema can be changed at any time by our own efforts. Usually these changes take a while before they are incorporated into the synthesis of a new body schema. If we opt for a new hairstyle or shave our beard, we’re likely to be startled the first few times we pass a mirror and catch a passing glance at our new appearance. But after a few additional mirror encounters, our brain incorporates the stylistic changes into a new body schema.

The most fascinating aspect of the body schema is that it can include more than just our body. For instance, when we drive our car along a narrow street and pass another car with just inches to spare, we judge the available distance between cars because at that moment our car has become a part of our body schema. For some people this incorporation of their car into internal representation influences both their perception and their behavior. Researchers have found that the lines separating parking places appear narrower to the driver of a Humvee than they do to the driver of a Prius. And body schema considerations help explain why some drivers fly into a rage over a minor ping or dent on a car door—their body schema has been altered.

The fine-tuning of motor skills leads to the creation of new and more powerful brain maps. For instance, after years of practice, musicians incorporate their musical instrument into their brain’s very circuitry. Eventually it’s as if the musician and his instrument have become inseparable. Look at any of the many pictures of Itzhak Perlman sitting with closed eyes and intense concentration as he fondly cradles his violin. Or watch YouTube videos of the late Glenn Gould (playing Bach Partita Number 6 in E minor, “Toccata,” or extracts from
The Art of Piano
), caressing the keyboard, his head lolling gently as he leans forward and whispers to his piano.

At times, this extension of body boundaries to include instruments and tools can take unusual, even amusing manifestations. Some people become personally attached to specific computers, cell phones, and other electronic gadgets. In some cases this leads to an insistence on the part of the owner that when the original unit malfunctions while under warranty, the manufacturer return to them the same unit rather than a replacement. That’s one of the reasons many warranties now routinely contain such phrases as “The manufacturer reserves the right to repair or replace this unit at its discretion.”

Before suggesting exercises for modifying the body schema, I want to describe an intriguing experiment involving what researchers refer to as peripersonal space (PPS), a force field that can be thought of as a virtual envelope around the skin’s surface that extends our body boundaries.

In a variety of species, including humans, some brain cells respond to both touch and sounds occurring near the face or the hands. Think of an imaginary border around the head and the hands around which sound-touch integration occurs. As a result of this integration, we are quicker to respond to something touching the hand when it is accompanied by a sound. This multisensory PPS serves a protective function: in the presence of a loud sound, something touching the face or the hand is detected more quickly. For a blind person the PPS is even more critical than it is for a sighted person, because of the blind person’s exclusive reliance for self-protection upon touch and sound.

According to research going back several years, the PPS of blind people is enlarged to include touch information coming not just from the hand but also from the tip of a walking cane. In essence their PPS has been expanded to form a new body representation where the space around the tip of the cane is as sensitive to touch as the space surrounding the hand. This holds true as well for those neurons that detect both touch and sound. Thus, if a noise originates near the tip of the cane, the blind person reacts to it as quickly as he would if it occurred close to the hand. In practical terms, such an arrangement enables the blind walker to detect touch or sound obstacles anywhere from the hand to the tip of the cane.

In an experiment carried out by a team of Italian brain scientists, normally sighted people received ten minutes of training in using a cane to find objects placed on the floor in a darkened room. That short training period was sufficient to alter their PPS to resemble that of blind people who regularly use a cane. They became as sensitive to touch and sound events occurring near the tip of the cane as to similar events happening near the hand.

In essence, just ten minutes of training with a cane by a person with perfectly normal vision brought about changes in PPS that were identical to those of a blind person. But this marvelous example of the plasticity of the adult brain was only temporary. Since the brain, thanks to its plasticity, changes from moment to moment, consistent and prolonged effort is required. That’s why blind people must use their cane for many years in order to shape and maintain their augmented PPS. And since the sighted volunteers’ training with a cane consisted of only a single ten-minute session, it should come as no surprise to learn that by the next day, in the absence of additional practice, their PPS boundary returned to the pretraining status: when blindfolded and holding their cane, the hand was once again much more responsive than the tip of the cane to touch or sudden noise.

The Body Has a Mind of Its Own,
a 2007 book by science writer Sandra Blakeslee and Matthew Blakeslee (her son), contains a succinct description of the practical implications of enhancing one’s peripersonal space:

Thanks to neurons in the frontal cortex that are bimodal (responding to touch and sound) or trimodal (responding to touch, sound, and vision), we activate identical brain areas whenever we use any of these three senses. Because of this intimate interplay among the neurons linking vision, touch, and proprioception, we’re able through our own efforts to enhance our brain’s functioning by integrating the information entering the brain from these senses. Trained athletes and musicians establish this integration through long years of practice leading to the development of a keen kinesthetic sense.

For example, a baseball pitcher can begin his windup and at the last second change direction and fire the ball to his left in a bid to pick off the first-base runner. Or a basketball player while charging down the court with the ball can look to his right in a feigning maneuver, change direction in an instant, run toward the basket and score two points with a hook shot. In both examples the athlete coordinates vision (what’s seen) with proprioception (what’s felt).

Even though most of us aren’t aiming at achieving the sensory integration of the athlete, we can enhance our brain’s functioning to enlarge our PPS by integrating our vision, sound, touch, and joint senses.

As a preliminary exercise in extending peripersonal space,
stand with your eyes closed and your hands at your sides. Now raise your arms to the horizontal position where they are exactly level with your shoulders along a straight line across your back so that the tip of the middle finger of one hand is on alignment with the tip of the middle finger of the other hand. Now extend the forefinger of each hand and close the other four fingers into a fist. Then, in a slow, sweeping, embracing motion in front of you, move the hands toward each other until you judge that the forefingers are just about to meet at the midline directly in front of you. At that point, stop moving your hands and open your eyes. Most people find that their forefingers are not on a direct projectory toward each other, but are off course by as much as an inch. In some cases, one or even both of the fingers will no longer be pointing in a horizontal direction, but slightly up or down. Repeat until you get it right.

When you’ve mastered that preliminary exercise, sit bare-footed in a chair with your right leg fully extended in front of you. Close your eyes and pretend that your right hand is a gun with the forefinger forming the barrel. Now with your eyes closed, point the forefinger directly at your big toe. When you’re confident that you’ve positioned the barrel of your imaginary gun so that you will be able to “shoot” your big toe, open your eyes. Few people are able on the first try to form a straight line from forefinger to toe in this test frequently used by neurologists to test joint (proprioceptive) sense. Joint-sense estimation is especially inaccurate in people with diseases affecting the nervous system anywhere along the route from the peripheral nerves in the legs to the parietal lobes, where joint and position sense is ultimately processed. But even people with normal nervous systems initially find it hard to point directly at their toe with their eyes closed. That’s because we rely primarily on our eyes to relay information to the brain. When we depend on sound, touch, or position sense we don’t do as well. But that over-dependence on vision can be balanced by exercises that enhance PPS.

Tai chi provides one of the most effective long-term approaches to enhancing peripersonal space. This ancient dancelike exercise requires the practitioner to perform a series of slow motions while simultaneously focusing attention on specific body areas, especially the hands and tips of the fingers. Over time this leads to alterations in the body image, especially PPS. For example, experienced tai chi practitioners develop a tactile acuity in the fingertips rivaling that of musicians and blind Braille readers. This suggests to C. E. Kerr and his Harvard-based colleagues that tai chi may create a plasticity within the brain similar to that found among individuals who play musical instruments, read Braille, or engage in other activities that require finely honed fingertip sensitivity. “There is a strong connection between tactile spatial acuity at the fingertips and measures of brain function,” says Kerr.

In order to get the maximum brain benefit, I suggest that you find a well-trained tai chi teacher and take some lessons. If this isn’t practical, several excellent DVD instructional programs are available. But whichever path you choose, you’ll learn as you move through the tai chi form, progressing from one of the sixty or more positions, that the hands and feet must be correctly and precisely aligned. To help you do this, your instructor will periodically ask you to pause, close your eyes, and mentally form an image of the current positions of your hands and legs. After you have envisioned the precise position of your hands and feet, he’ll ask you to open your eyes and check how accurately your internal image corresponds to your body position. It takes years of practicing tai chi forms before the internal image and the external positions correspond exactly.

Other everyday examples of extending peripersonal space include alternating between a pen and a word processor; learning to play a musical instrument; purchasing a newer and lighter tennis racket that frees your swing; spending a weekend at an auto-racing camp where you can learn highspeed control skills as taught by competition race-car drivers. In these instances the pen, the musical instrument, the tennis racket, and the high-performance car extend and enhance the body’s performance by creating new functional maps within the brain. The experience is similar to what happens when the blind person becomes skilled in the use of his cane. The more time spent creating these new maps the greater your proficiency. And while you can follow my suggestions of how you can form these new maps the best approach is to come up with your own program that incorporates activities that are interesting to you. The key is to activate those neurons that construct our PPS.

After enhancing sensory memory by performing one or more of the suggested approaches, you’re now in a better position to work on
ways to improve memory in general.

Science fiction writers are fond of presenting their readers with characters who no longer know who they are because their memories have been obliterated. In the 2000 movie
Memento,
the main character, Leonard Shelby, lives in an anxious and forebodingly eternal present; he can’t recall any of his past experiences and as a result doesn’t know who he is. But such devastating memory failures aren’t just the stuff of fiction.

A real-life patient (identified as H.M. in order to protect his privacy) lost his capacity to form new memories following a brain operation that removed the hippocampus and parts of his anterior temporal lobe on each side of his brain. As a result of his absent hippocampi (the plural form; there is one hippocampus on each side of the brain), H.M. permanently lost the ability to form new memories. Each time he encountered his doctor the experience was a new one for him. His memory was so bad that after learning of his mother’s death, he soon forgot this distressing information, and over the years he became upset and wept anew whenever anyone mentioned that she was no longer alive.