Brain Hemispheres Explained: 6 Brain Hemisphere Parts

Like all mammalian brains, the human brain is divided into a left hemisphere, located on the left side of the cranium, and a right hemisphere, located on the right side. These hemispheres comprise the cerebrum, which is the part of the brain responsible for conscious thought and voluntary actions. As such, the two sides of the brain are called the cerebral hemispheres.

Each brain hemisphere consists of gray matter, white matter, and lobes that provide different functions:

1. 1. Cerebral cortex: The outer layer of each hemisphere is known as the cerebral cortex, which is made up of gray matter. Decades of neuroscience research shows that nearly all cognitive thinking occurs in the cerebral cortex. A brain injury can cause damage to this outer layer and therefore affect cognition. Beneath the cerebral cortex is a thick layer of white matter, which gets its color from bundles of neurons with white myelin sheaths. Neuroscientists understand less about the white matter than they do about the cerebral cortex. Still, it seems to play a key role in the central nervous system by connecting the cerebrum to the brainstem and vice versa. The white matter is thereby the conduit between the cerebral cortex and the entire peripheral nervous system.
2. 2. Frontal lobe: Within the cerebral cortex, each hemisphere has a frontal lobe that controls cognition and voluntary action.
3. 3. Parietal lobe: The parietal lobe in the cerebral cortex of each hemisphere processes sensory information related to temperature, smell, and touch.
4. 4. Temporal lobe: The temporal lobes in the cerebral cortex also process sensory information, particularly auditory information related to music and language. They also surround the hippocampus and amygdala, which help govern learning, memory, and emotional response as part of the brain's limbic system.
5. 5. Occipital lobe: The occipital lobes contain the cerebral cortex’s primary visual cortex, which processes information from the body's visual field.
6. 6. Corpus callosum: A band of soft tissue known as the corpus callosum joins the two cerebral hemispheres. Above the corpus callosum is a clear groove between the two hemispheres of the brain.

Scientists believe that the human brain has hemispheric lateralization. This means that, in terms of neuroanatomy, each side of the brain works with the other but performs its own unique functions:

• Each side of the brain controls the opposite side of the body. In terms of physical motion, the brain functions as a mirror image, meaning that each hemisphere of the brain controls the opposite side of the body. Magnetic resonance imaging clearly shows greater activity in the cortical receptors of the right hemisphere when the left side of the body is working; the same is true for the left hemisphere and the right side of the body.
• The left brain and right brain have different cognitive emphases. The left cerebral hemisphere and the right cerebral hemisphere have been shown to manage different parts of cognitive thinking. The left hemisphere is frequently associated with language function, such as grammar and speech. Neuroscientists also believe that the left hemisphere is more active in visually processing concrete shapes and applying absolute rules and ethics. By contrast, the right hemisphere appears integral to making sense of abstract or disparate stimuli and connecting them into a whole entity. This can apply to both sensory stimuli and abstract thought. Both hemispheres must work together for holistic cognition and problem-solving.
• Possible relationship with left- or right-handedness. Notably, handedness might affect the hemispheric difference between the two sides of the cerebrum. For instance, in right-handed people, language processing is heavily concentrated in the brain’s left hemisphere. Yet for those who favor their left hand, language tends to be processed by both hemispheres of the brain—and for some left-handed people, the right hemisphere may even be more active.

A common misconception is that different areas of the brain process certain functions entirely on their own. For instance, a popular myth is that the left hemisphere of the brain carries out mathematics and hard sciences, while creative expression is limited to the right side of the brain. Scientific research does not support functional asymmetry.

Find something comfortable to sit or lie on, grab a MasterClass Annual Membership, and dial into the present moment with Jon Kabat-Zinn, the father of the Western mindfulness movement. From formal meditation exercises to examinations of the science behind mindfulness, Jon will prepare you for the most important practice of them all: life itself.