How do cerebral hemispheres communicate

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. Skip to main content. Search for:. Brain Hemispheres Learning Objectives Explain the relationship between the two hemispheres of the brain.

Watch It 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.

Try It. Did you have an idea for improving this content? Licenses and Attributions. Are you right-handed or left-handed? Another way to refer to people who use their right hand is to say that they are dominant.

Exactly why people are right-handed or left-handed is somewhat of a mystery. William Calvin has developed a fascinating theory about the origin of handedness and has written an essay called The Throwing Madonna to explain it.

The right side of the brain controls muscles on the left side of the body and the left side of the brain controls muscles on the right side of the body. Also, in general, sensory information from the left side of the body crosses over to the right side of the brain and information from the right side of the body crosses over to the left side of the brain.

Therefore, damage to one side of the brain will affect the opposite side of the body. Back in the s and s, two neurologists Paul Broca and Karl Wernicke observed that people who had damage to a particular area on the left side of the brain had speech and language problems.

People with damage to these areas on the right side usually did not have any language problems. The two language areas of the brain that are important for language now bear their names: Broca's area and Wernicke's area. Each hemisphere of the brain is dominant for other behaviors. For example, it appears that the right brain is dominant for spatial abilities, face recognition, visual imagery and music. The left brain may be more dominant for calculations, math and logical abilities. Of course, these are generalizations and in normal people, the two hemispheres work together, are connected, and share information through the corpus callosum.

Much of what we know about the right and left hemispheres comes from studies in people who have had the corpus callosum split - this surgical operation isolates most of the right hemisphere from the left hemisphere. This type of surgery is performed in patients suffering from epilepsy.

The corpus callosum is cut to prevent the spread of the "epileptic seizure" from one hemisphere to the other. Roger Sperry who won the Nobel prize in and Michael Gazzaniga are two neuroscientists who studied patients who had surgery to cut the corpus callosum.

These studies are called "Split-Brain Experiments". After surgery, these people appeared quite "normal" - they could walk, read, talk, play sports and do all the everyday things they did before surgery.

Only after careful experiments that isolated information from reaching one hemisphere, could the real effects of the surgery be determined. The cerebrum is a term often used to describe the entire brain. A fissure or groove that separates the two hemispheres is called the great longitudinal fissure. The two sides of the brain are joined at the bottom by the corpus callosum. The corpus callosum connects the two halves of the brain and delivers messages from one half of the brain to the other.

The surface of the cerebrum contains billions of neurons and glia that together form the cerebral cortex. The cerebral cortex, which is the most superficial part of the hemispheres and is only a few millimeters in thickness, is composed of gray matter, in contrast to the interior of the hemispheres, which is composed partly of white matter. The exterior surface of the cerebrum, the cerebral cortex, is a convoluted folded grayish colored layer known as gray matter.

The convolutions are made up of ridge like bulges gyri separated by small grooves called sulci and larger grooves called fissures. Gray matter which consists of unmyelinated nerve cell bodies, composes the cerebral cortex or outer portion of the cerebrum. Beneath the cortex lies the white matter or myelinated axons.

During embryonic development, the cortex folds upon itself to form gyri folds and sulci shallow grooves so that more gray matter can reside within the skull cavity and giving the brain its distinctive look. The cerebral cortex is the structure within the brain that plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. Gray matter is formed by neurons and their unmyelinated fibers, whereas the white matter below the gray matter of the cortex is formed predominantly by myelinated axons interconnecting different regions of the central nervous system CNS.

The human cerebral cortex is between 2 to 4 mm thick. The Cerebrum. The cerebrum is divided into two major parts: the right and left cerebral hemispheres or halves at a fissure, the deep groove down the middle.

The cerebral cortex is connected to various subcortical structures like the thalamus and the basal ganglia, sending information to them along efferent connections and receiving information from them via afferent connections.

Most sensory information is routed to the cerebral cortex via the thalamus. Olfactory information, however, passes through the olfactory bulb to the olfactory cortex or piriform cortex.

The vast majority of connections are from one area of the cortex to another rather than to subcortical areas. Cortical regions known as associative cortex are responsible for integrating multiple inputs, processing the information, and carrying out complex responses. Sensory Areas are the areas that receive and process information from the senses.

The parts of the cortex that receive sensory inputs from the thalamus are called primary sensory areas. The senses of vision, audition, and touch are served respectively by the primary visual cortex, primary auditory cortex and primary somatosensory cortex.