It’s fascinating to learn that most people who have lost a limb can still feel it in vivid detail. This isn’t just a distant memory or a vague shape; they can actually sense their phantom fingers moving and even feel sensations like a watchband’s pressure or an ingrown toenail’s discomfort. Surprisingly, even individuals born without a limb can sometimes experience these phantom sensations.
So, what causes these phantom limb sensations? The detailed nature of these feelings suggests that our brains have a built-in map of our bodies. The fact that people who have never had a limb can feel one indicates that this map is present from birth. However, one significant difference is that phantom limbs are often painful, unlike their physical counterparts.
To grasp the concept of phantom limbs and the associated pain, we need to explore the entire pathway from the limb to the brain. Our limbs are filled with sensory neurons that help us feel textures and understand our body’s position in space. These neurons send sensory information through the spinal cord to the brain. Even after an amputation, most of this pathway remains intact, although the loss of a limb changes how signals travel along it.
At the site of amputation, nerve endings can become thicker and more sensitive, sending distress signals even with mild pressure. Normally, these signals are controlled in the spinal cord’s dorsal horn, but after an amputation, this control is lost, allowing signals to become more intense.
Once sensory signals reach the brain, the somatosensory cortex processes them. This cortex contains a map of the entire body, with more sensitive parts having larger areas represented. The cortical homunculus is a model that shows the human body with proportions based on the size of each body part’s representation in the cortex. The brain can adjust the size of these representations based on sensory input. For instance, violinists have a larger representation of their left hand compared to non-violinists. When a body part is injured, the brain increases its representation to heighten sensations and alert us to danger, which can lead to phantom pain.
The cortical map likely explains why we can feel body parts that are no longer there, as they still have representation in the brain. Over time, this representation may shrink, and the phantom limb sensation may diminish. However, these sensations don’t always disappear on their own.
Treating phantom limb pain usually involves a combination of physical therapy, pain management medications, prosthetics, and time. One effective technique is mirror box therapy, where the patient places the phantom limb behind a mirror and the intact limb in front. This tricks the brain into seeing the phantom limb, not just feeling it. Virtual reality treatments are being developed to enhance this experience. Prosthetics can also help, as many patients report pain primarily when they remove their prosthetics at night. Phantom limbs may assist patients in viewing prosthetics as extensions of their bodies, allowing them to use them more naturally.
There are still many unanswered questions about phantom limbs. We don’t know why some amputees don’t experience the pain typically associated with these sensations or why some don’t have phantom sensations at all. Further research into phantom limbs is valuable not only for those who experience them but also for understanding how our brains construct the world we perceive. These sensations remind us that our experiences of reality are subjective.
Research and create a visual representation of the cortical homunculus. Use this model to understand how different body parts are represented in the brain. Discuss with your peers how this representation might relate to phantom limb sensations.
Participate in a hands-on workshop where you simulate mirror box therapy. Use mirrors to create the illusion of a phantom limb and discuss the psychological and physiological effects observed. Reflect on how this technique might alleviate phantom limb pain.
Engage in a virtual reality session designed to simulate phantom limb sensations. Analyze how VR can be used to treat phantom limb pain and discuss the potential benefits and limitations of this technology in therapy.
Examine case studies of individuals with phantom limb sensations. Identify common themes and differences in their experiences. Present your findings to the class, focusing on how these insights contribute to our understanding of the brain’s body map.
Develop a research proposal to investigate an unanswered question about phantom limbs. Consider the methodologies you would use and the potential impact of your research. Share your proposal with classmates for feedback and discussion.
The vast majority of people who have lost a limb can still feel it—not as a memory or vague shape, but in complete lifelike detail. They can flex their phantom fingers and sometimes even feel sensations like the chafe of a watchband or the throb of an ingrown toenail. Astonishingly, even people born without a limb can occasionally feel a phantom.
So, what causes phantom limb sensations? The accuracy of these sensations suggests that we have a map of the body in our brains. The fact that someone who has never had a limb can feel one implies that we are born with at least the beginnings of this map. However, one thing that sets the phantoms appearing after amputation apart from their physical counterparts is that the vast majority of them are painful.
To fully understand phantom limbs and phantom pain, we need to consider the entire pathway from limb to brain. Our limbs are full of sensory neurons responsible for everything from the textures we feel with our fingertips to our understanding of where our bodies are in space. Neural pathways carry this sensory input through the spinal cord and up to the brain. Since much of this pathway lies outside the limb itself, most of it remains after an amputation. However, the loss of a limb alters how signals travel at every step of the pathway.
At the site of an amputation, severed nerve endings can thicken and become more sensitive, transmitting distress signals even in response to mild pressure. Under normal circumstances, these signals would be curtailed in the dorsal horn of the spinal cord. For reasons we don’t fully understand, after an amputation, there is a loss of this inhibitory control in the dorsal horn, allowing signals to intensify.
Once they pass through the spinal cord, sensory signals reach the brain, where the somatosensory cortex processes them. The entire body is mapped in this cortex, with sensitive body parts having larger areas represented. The cortical homunculus is a model of the human body with proportions based on the size of each body part’s representation in the cortex. The amount of cortex devoted to a specific body part can grow or shrink based on how much sensory input the brain receives from that body part. For example, the representation of the left hand is larger in violinists than in non-violinists. The brain also increases cortical representation when a body part is injured to heighten sensations that alert us to danger. This increased representation can lead to phantom pain.
The cortical map is likely responsible for the feeling of body parts that are no longer there, as they still have representation in the brain. Over time, this representation may shrink, and the phantom limb may shrink with it. However, phantom limb sensations don’t necessarily disappear on their own. Treatment for phantom pain usually requires a combination of physical therapy, medications for pain management, prosthetics, and time.
A technique called mirror box therapy can be very helpful in developing the range of motion and reducing pain in the phantom limb. The patient places the phantom limb into a box behind a mirror and the intact limb in front of the mirror. This tricks the brain into seeing the phantom rather than just feeling it. Scientists are developing virtual reality treatments that make the experience of mirror box therapy even more lifelike. Prosthetics can also create a similar effect—many patients report pain primarily when they remove their prosthetics at night. Phantom limbs may help patients conceptualize prosthetics as extensions of their bodies and manipulate them intuitively.
There are still many questions about phantom limbs. We don’t know why some amputees escape the pain typically associated with these sensations, or why some don’t have phantoms at all. Further research into phantom limbs isn’t just applicable to those who experience them. A deeper understanding of these sensations will provide insight into the work our brains do every day to build the world as we perceive it. They serve as an important reminder that the realities we experience are, in fact, subjective.
Phantom – In psychology and neuroscience, a phantom refers to the sensation that an amputated or missing limb is still attached to the body and is moving appropriately with other body parts. – After the amputation, the patient reported experiencing phantom sensations, feeling as though his missing foot was still present.
Limb – In biology, a limb is an appendage of the human or animal body, such as an arm, leg, wing, or flipper, used for locomotion or manipulation. – The study focused on the regeneration capabilities of certain species, which can regrow a lost limb.
Sensations – In psychology, sensations are the processes by which our sensory receptors and nervous system receive and represent stimulus energies from our environment. – The experiment measured the participants’ sensations of heat and cold on different parts of their skin.
Brain – In biology and psychology, the brain is the organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals, responsible for processing sensory information and controlling behavior. – Neuroscientists are exploring how different regions of the brain contribute to emotional regulation.
Neurons – In biology, neurons are the fundamental units of the brain and nervous system, responsible for receiving sensory input from the external world, processing it, and sending commands to muscles. – The research highlighted how neurons communicate through synapses to transmit information throughout the body.
Cortex – In neuroscience, the cortex refers to the outer layer of the cerebrum, involved in complex brain functions such as perception, thought, and decision-making. – Functional MRI scans showed increased activity in the prefrontal cortex during problem-solving tasks.
Representation – In psychology, representation refers to the mental depiction of sensory information, allowing individuals to interpret and understand their environment. – The study examined how visual representation in the brain changes with learning and experience.
Pain – In biology and psychology, pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage. – Researchers are investigating new methods to manage chronic pain without the use of opioids.
Therapy – In psychology, therapy refers to the treatment of mental or psychological disorders by psychological means, often involving talking therapies or behavioral interventions. – Cognitive-behavioral therapy has been shown to be effective in treating anxiety disorders.
Research – In science, research is the systematic investigation into and study of materials and sources in order to establish facts and reach new conclusions. – The university’s research on neuroplasticity is contributing to our understanding of how the brain adapts to new information.
