If you were to peer into the vast depth of the milky way galaxy and count each star one by one, it would not even scratch the surface into how many synapses a single brain has. In fact, it would take over 1,500 milky way galaxies to reach the number of synapses our cerebral cortex has. It is estimated that our cerebral cortex alone has roughly 125 trillion synapses. This allows our brain to calculate data at a rate that is unmatched even with the most complex supercomputers. Of all the important jobs and responsibilities our brain has, its most primary role is to receive and interpret information. In this article, we are going to discuss the parietal lobe and its role in allowing us to function.

Answering the Question – Where? – Without Having to Think About it

Our body is equipped with hundreds of thousands of little receptors (or sensors) that all relay important information up to the brain to answer two really important questions:

• Where are my limbs and body positioned?
• Where is my environment in relationship to my body?

Our parietal lobe lets us know where our body is at all times. Go ahead and close your eyes right now, just for 15 seconds. Did you do it? If you did, ask yourself the following questions:

• Were you aware of how your legs were positioned?
• Were your fingers bent or straight?
• Were you sitting upright? How about hunched over?

What about more complex questions like, when your eyes were closed:

• Could you tell how far away the nearest wall is from you?
• Could you tell how far away your head was in relationship to the floor?
• Or what about how far away the ceiling is from your head?

Although our parietal lobe receives input from multiple senses, the answers to these questions do not necessarily have to be provided by our traditional five senses. Think about it. You did not have to see, hear, smell, taste, or touch your limbs to know exactly how they were positioned, and where they were. You can just sense these things! And it is your parietal lobe that allows for that.

You may be aware of some of these things right now, but the majority of our day our brain computes this information on an unconscious level. The area in which the information is computed is our somatosensory cortex, a part of the parietal lobe.

The Somatosensory Cortex

The word soma in Greek translates to “body.” So our Somatosensory cortex is all about providing us with a “body” sense. Your somatosensory cortex is fed information from your skin and joint receptors, which allow you to process pressure, pain, vibration, touch, temperature, and joint position.

Sensory Homunculus – Our Little Body in Our Brains

If I were to touch you on your thumb, the perception of where your body is being touched is located in your brain. Within our somatosensory cortex lies a representation, of our body called the sensory homunculus. Homunculus is Latin translates to “little man” or “little body.” It is essentially a small map, or representation of our body. The sensory sensitivity of your body parts is directly related to how much space your parietal lobe devotes to that particular body part. For instance, we use our hands and our thumbs to do more things than our low back. Or we use our mouths and tongue to do more things than our big toe. Because of how the homunculus is oriented it can help our doctors better locate the area that is effected in the parietal lobe.

Painting Our World Around Us

The parietal lobe not only gives us a sense and perception for our bodies, but also helps us gain a sense of our three-dimensional world. The integration between sensory and visual processing happens in our posterior parietal lobe. It is this part of the brain that allows us to understand right from left, up and down, and the ability to sense objects around us without physically touching them.

With a higher functioning parietal lobe, it allows us to develop incredible physical skills like top level athletes. The more accurate representation of not only our body map and a map of our environment, the more accurate we can respond to things.

Because the parietal lobe provides such vital information, it is deeply integrated with the body’s other functions. For example, your spatial awareness gives you the ability to make decisions, plan, and navigate. In many ways, our parietal lobe has helped us become the explorers, pioneers, and astronauts that we are today.

What Happens With a Dysfunctional Parietal Lobe

For those with damage to their parietal lobes, even the most basic functions can be hindered. With physical damage to the parietal lobe, usually the symptoms are more obvious and prominent. More commonly, someone may have subtle symptoms suggesting a functional weakness/lesion. These types of lesions may not always be seen on imaging. This is usually because the person has enough neurons there, but the neurons may be weak or not firing appropriately. Usually, both functional and some physical lesions can be helped to some degree.

Some Symptoms That We See With Dysfunctional Parietal Lobes Are:

• Difficulty with spatial awareness
  • Being clumsy
  • Frequently bumping into objects
  • Bumping into things with objects you control (i.e. Hitting curbs with your car, bumping stands with your shopping cart)
• Reoccurring injury with the same body part, or on the same side of your body
• Pain that tends to be more on one side of the body
• Altered sensation on one side of the body (i.e. numbness or tingling)
• Poor visuospatial processing (weak non-dominant hemisphere)
  • Mental rotation of objects – like knowing directions, which way you are facing, or interpreting maps
  • Depth perception
  • Using spatial imagery for deductive reasoning
• Dyslexia (weak dominant hemisphere)
• Difficulty with math calculations, often called Dyscalculia (weak dominant hemisphere)
• Left/Right confusion
• Harder time tracking moving objects across your visual field
• Loss of vision or visual targeting on the lower portion of your visual fields – called a Lower Quadrantinopia
• Hemineglect Syndrome
• Apraxia, or poor motor planning
• Sensory Agnosia

Thankfully, these symptoms can help your neurologist locate which parietal lobe and and where in the parietal lobe is lacking in function. You may have noticed that some of the above symptoms stated that they may be an issue in the “dominant” or “non-dominant” hemisphere. The dominant hemisphere refers to usually which side of the brain language develops, in most right-handed (and-left handed) people the dominant hemisphere is the left side. Around 30% of left-handed individuals will have a right dominant hemisphere. So someone who has been diagnosed with dyscalculia, and cannot sense as well on the right side of their body may have dysfunction in their left parietal system. Someone who has poor visuospatial processing, and cant sense as well on the left side of their body may have dysfunction in their right parietal system. Through targeted therapy and rehabilitative exercises, the doctors at Integrative Brain and Body can better help a patient understand where they need treatment in their parietal lobes.

Therapy For The Parietal Lobe

Because the parietal lobe is sensory in nature many different sensory modalities can help activate certain areas of the parietal lobe. Heat, vibration, joint position, and electricity can all be therapeutic. In some individuals, sensory information is not enough. This is where creative therapies can be effective.

Mirrors have been used to trick the part of the parietal lobe that integrates with our visual centers of our brain. This has been shown to be effective in some stroke victims and other individuals with complex pain syndromes. Placing a mirror in front of someone, to split the body in half, and having them do therapy on the good side of the body can trick the brain into perceiving the other half of the body through the mirror.

Looking at rotated images of certain limbs can bring awareness to the map of that limb in our sensory homunculus. This is something called graded motor imagery, and can be used on individuals with complex pain syndromes, as well as hemineglect.

With a person’s eyes closed, and writing numbers that make up simple math equations on various body parts on the right side of the body can work multiple areas within the left parietal system.

In summary, the parietal lobe is a very important part of your brain and body’s function. It provides different neurologists an opportunity use therapies to strengthen your perception of self, and overall ability to respond appropriately and navigate in our world.