What is the difference between the two cerebral hemispheres

Some areas of the cerebral hemispheres control muscular activity, and their nerve cells send processes to the brain stem and spinal cord, where they are connected with motor neurons, the processes of which leave by way of cranial nerves or ventral roots in the spinal cord.

Other areas are sensory and receive impulses that have reached the spinal cord by way of peripheral nerves and dorsal roots, and have ascended in the spinal cord and brain stem by pathways that consist of a succession of nerve cells and their processes.

In general, the left hemisphere or side of the brain is responsible for language and speech. Because of this, it has been called the "dominant" hemisphere. The right hemisphere plays a large part in interpreting visual information and spatial processing. In about one third of individuals who are left-handed, speech function may be located on the right side of the brain.

Left-handed individuals may need specialized testing to determine if their speech center is on the left or right side prior to any surgery in that area. Research has determined that touching one side of the brain sends electrical signals to the other side of the body. Touching the motor region on the right side of the brain, would cause the opposite side or the left side of the body to move.

Stimulating the left primary motor cortex would cause the right side of the body to move. The messages for movement and sensation cross to the other side of the brain and cause the opposite limb to move or feel a sensation. The right side of the brain controls the left side of the body and vice versa So if damage occurs on the right side of the brain that controls the movement of the arm, the left arm may be weak or paralyzed.

Broca French neurosurgeon Pierre Paul Broca's research in gave one of the first indications of brain function lateralization. His research involved a man who suffered a speech deficit or aphasia. In the later autopsy of the man, Broca determined he had a syphilitic lesion in the left cerebral hemisphere. This left frontal lobe brain area, or Broca's Area, is an important speech production region.

In clinical assessment of this aphasia, it's noted that the patient can't clearly articulate the language being employed. Wernicke German physician Karl Wernicke began pursuing his own research into the effects of brain disease on speech and language by studying language deficits unlike Broca aphasias. Resources for News Media.

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Levels of Evidence: Integrative Therapies. However, they are able to recreate the picture with their left hand, which is also controlled by the right hemisphere. When the more verbal left hemisphere sees the picture that the hand drew, the patient is able to name it assuming the left hemisphere can interpret what was drawn by the left hand.

Figure 2. Much of what we know about the functions of different areas of the brain comes from studying changes in the behavior and ability of individuals who have suffered damage to the brain. For example, researchers study the behavioral changes caused by strokes to learn about the functions of specific brain areas.

A stroke, caused by an interruption of blood flow to a region in the brain, causes a loss of brain function in the affected region. The damage can be in a small area, and, if it is, this gives researchers the opportunity to link any resulting behavioral changes to a specific area. The types of deficits displayed after a stroke will be largely dependent on where in the brain the damage occurred.

Consider Theona, an intelligent, self-sufficient woman, who is 62 years old. Recently, she suffered a stroke in the front portion of her right hemisphere. As a result, she has great difficulty moving her left leg. Theona has also experienced behavioral changes. For example, while in the produce section of the grocery store, she sometimes eats grapes, strawberries, and apples directly from their bins before paying for them. This behavior—which would have been very embarrassing to her before the stroke—is consistent with damage in another region in the frontal lobe—the prefrontal cortex, which is associated with judgment, reasoning, and impulse control.

Watch this video to see an incredible example of the challenges facing a split-brain patient shortly following the surgery to sever her corpus callosum. Watch this second video about another patient who underwent a dramatic surgery to prevent her seizures.

Improve this page Learn More. Additionally, neuroplasticity the ability of a brain to adapt to experience enables the brain to compensate for damage to one hemisphere by taking on extra functions in the other half, especially in young brains.

The two hemispheres communicate with one another through the corpus callosum. The corpus callosum is a wide, flat bundle of neural fibers beneath the cortex that connects the left and right cerebral hemispheres and facilitates interhemispheric communication. The corpus callosum is sometimes implicated in the cause of seizures; patients with epilepsy sometimes undergo a corpus callostomy, or the removal of the corpus callosum.

The brain is divided into four lobes, each of which is associated with different types of mental processes. Clockwise from left: The frontal lobe is in blue, the parietal lobe in yellow, the occipital lobe in red, and the temporal lobe in green. The frontal lobe is associated with executive functions and motor performance.

Executive functions are some of the highest-order cognitive processes that humans have. Examples include:. The frontal lobe is considered to be the moral center of the brain because it is responsible for advanced decision-making processes. It also plays an important role in retaining emotional memories derived from the limbic system , and modifying those emotions to fit socially accepted norms.