Can you still feel a limb that's gone? - Joshua W. Pate

Summary

Phantom limb sensations occur when amputees or even those born without a limb experience vivid, sometimes painful, sensations of a missing body part. This phenomenon is tied to the brain's internal map of the body, which remains intact after amputation. Changes in nerve pathways and cortical representation contribute to these sensations. Treatments like mirror box therapy and prosthetics can help reduce pain and enhance functionality. Further research on phantom limbs offers insights into how our brains construct reality, highlighting the subjectivity of perception.

Takeaways

• 🧠 Phantom limbs are experienced by most people who lose a limb, and they feel realistic, not just as memories or vague shapes.
• 👶 Even people born without limbs can sometimes experience phantom limb sensations, suggesting we are born with a body map in the brain.
• 🩹 Phantom limbs are often painful, setting them apart from the limbs they replace.
• 🦾 Sensory neurons, which transmit signals from the body to the brain, remain mostly intact after amputation, affecting the way signals travel.
• ⚡ Severed nerve endings can become overly sensitive after amputation, sending pain signals even in response to mild stimuli.
• 🗺️ The somatosensory cortex, where the body is mapped, processes these sensory signals. Larger areas are dedicated to more sensitive body parts, like hands and lips.
• 🎻 The brain can adapt its cortical map depending on use or injury—violinists, for example, have a larger representation of their left hand in the brain.
• 🪞 Mirror box therapy can help reduce phantom limb pain by tricking the brain into seeing the missing limb.
• 🦿 Prosthetics can also reduce phantom pain, and patients may perceive them as natural extensions of their bodies.
• 🔍 Understanding phantom limbs offers insights into how the brain constructs the subjective realities we perceive daily.

Q & A

What is a phantom limb sensation?

A phantom limb sensation is the feeling that an amputated or missing limb is still present, often with vivid detail and sometimes pain.

Why do some people feel phantom limbs even if they were born without them?

The fact that some people born without a limb can feel a phantom suggests that we are born with at least the beginnings of a body map in our brains.

How does the loss of a limb affect the neural pathways?

The loss of a limb alters the way signals travel through the neural pathways, causing severed nerve endings to become more sensitive and transmit distress signals.

What is the role of the dorsal horn of the spinal cord in phantom limb sensations?

Under normal circumstances, the dorsal horn of the spinal cord curtails signals, but after an amputation, there is often a loss of this inhibitory control, leading to intensified signals.

How does the somatosensory cortex process sensory signals related to phantom limbs?

The somatosensory cortex processes sensory signals, and the entire body is mapped in this cortex. The cortical map is likely responsible for the feeling of body parts that are no longer there.

What is the cortical homunculus and how does it relate to phantom limb sensations?

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. It helps explain why sensitive body parts are represented by larger areas and how the brain can still 'feel' a limb that is no longer there.

Can the brain adjust the cortical representation of a body part?

Yes, 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.

How does the brain's representation of a body part relate to phantom pain?

An increased representation of a body part in the brain, often due to injury, can lead to heightened sensations and potentially phantom pain.

What is mirror box therapy and how can it help with phantom limb pain?

Mirror box therapy is a technique where a patient places the phantom limb behind a mirror and the intact limb in front, tricking the brain into seeing the phantom, which can help develop range of motion and reduce pain.

How can prosthetics help with phantom limb sensations and pain?

Prosthetics can help patients conceptualize them as extensions of their bodies, allowing for intuitive manipulation and potentially reducing pain, especially when used consistently.

What are some of the unanswered questions about phantom limbs?

We don't know why some amputees escape the pain typically associated with phantom limbs, or why some don't have phantoms at all.

How can the study of phantom limbs provide insight into our everyday perception?

A deeper understanding of phantom limbs can give us insight into how our brains build the world as we perceive it, reminding us that our realities are subjective.