The Human Brain
The human brain is a unique and complex structure; it facilitates vital and complicated physiological and psychological functions such as consciousness, mobility, emotion, and personality. Different parts of the brain are responsible for specific functions. Injury affecting any one part of the brain may rob a person of many essential faculties. Familiarity with brain anatomy provides better understanding of how traumatic brain injury impairs brain function and how it affects a person's behavior, consciousness, and quality of life.
Human Brain Anatomy
The human brain is the powerhouse and control center for all physiological and cognitive functions. The brain controls lower, unconscious physiological activities such as breathing, pulse, and digestion; and higher, conscious activities such as thinking, reasoning, and feeling. The human brain is unique because it contains billions of neurological connections that work together to carry out complex functions.
Brain injury disrupts neurological connections, which impairs normal brain function. Following injury, function impairment is dependant on where in the brain the damage occurs and how many areas are affected. Open head brain injury often damages a specific brain area, such as the location where an object penetrates brain tissue. Closed head brain injury damages several brain areas. Closed head brain injury swelling, or diffuse axonal injury, shear and destroy nerve fibers, leaving neurons unable to communicate to carry out functions.
Four primary regions are the brainstem, the cerebellum, the cerebrum, and the cerebral cortex. Each brain region is responsible for a variety of functions, and injury to any of these regions impairs specific functions.
The brainstem is connected to the spinal cord at the back of the brain. The brainstem controls unconscious functions such as respiration, digestion, and pulse. Three structures comprise the brainstem: the midbrain, the pons, and the medulla oblongata. The midbrain controls eye movement and focus. The pons sends signals back and forth between the cerebrum and cerebellum. The medulla oblongata controls respiration, blood pressure, pulse rate, and digestion.
As the brainstem is responsible for vital survival functions, brain injury that damages the brainstem is often fatal. People who survive brainstem injury usually require assistance with simple physical functions like breathing and regulating pulse.
- Sleep / wake cycle
- Concentration and attention
Brainstem Injury Problems
- Problems with breathing
- Inability to swallow food and water (dysphagia)
- Dizziness and nausea
- Sleep apnea
- Irregular heartbeat (arrhythmia)
Meaning "little brain" in Latin, the cerebellum controls motor activity and helps a person maintain posture and balance. The cerebellum also enables a person to perform rapid and repetitive movements like running. Injury to the cerebellum causes dizziness, mobility problems, or paralysis.
Cerebellum Brain Functions
Cerebellum Injury Problems
- Inability to coordinate movement
- Inability to walk
"Cerebrum" denotes the right and left brain hemispheres. Each hemisphere contains four lobes (frontal, temporal, occipital, and parietal) that are responsible for a variety of functions, including memory, vision, hearing, and speaking. Injury to these areas often causes vision impairment, temporary or permanent memory loss (amnesia), an inability to speak, and other problems.
The frontal lobe is the largest of the four lobes. The frontal lobe is responsible for many different functions involving conscious thought, voluntary movement, and personality. The frontal lobe also facilitates word choice, organization, and behavior. Frontal lobe damage can dramatically change personality and behavior, and impair judgment, attention span and organization.
Frontal Lobe Functions
- Behavioral choices
- Expressive language and word choice
Frontal Lobe Injury Complications
- Personality change
- Lack of attention
- Loss of executive function (planning, organizing, and reasoning)
- Loss of judgment
- Dramatic change in behavior
- Loss of motivation
Located at the back of the brain, the occipital lobes receive and process visual information. The occipital lobes also process colors and shapes. Whereas the right occipital lobe interprets images from the left visual space, the left occipital lobe interprets images from the right visual space. Damage to the occipital lobes can permanently damage visual perception.
Occipital Lobe Functions
Occipital Lobe Injury Complications
- Loss of visual capability
- Inability to identify colors
The parietal lobes process and interpret signals received from other brain areas. These signals include vision, hearing, motor skills, and memory. The parietal lobes give objects meaning and environments depth. Parietal lobe damage disrupts shape, size and color identification, and distance perception.
Parietal Lobe Functions
- Size, shape, color identification
- Spatial perception
- Visual perception
Parietal Lobe Injury Complications
- Inability to identify objects
- Inability to associate words with meaning
- Inability to distinguish left from right
- Loss of spatial perception
The temporal lobes are on the bottom (ventral) and the side (lateral) of each brain hemisphere. The right temporal lobe facilitates visual memory. The left temporal lobe facilitates verbal and language memory and assists with organization and event sequencing. The back of the temporal lobes enables emotional interpretation.
Temporal Lobe Functions
- Processing language and communication
- Emotional interpretation
Temporal Lobe Injury Consequences
- Inability to recognize faces
- Communication and comprehension problems
- Inability to identify objects
- Short-term memory loss
- Inability to categorize objects
The cerebral cortex is tissue that covers the cerebrum. A thick band of nerves (corpus callosum) connects the right and left cerebral cortex sides. The cerebral cortex is responsible for most "higher order" or intellectual brain functions such as thinking, reasoning, judging, planning, voluntary movement, and overall behavior. Injury to this area of the brain can impair judgment, cause dramatic personality change, and create problems with attention and focus.
Cerebral Cortex Functions
- Voluntary movements
- Speech and language
Cerebral Cortex Injury Problems
- Problems with sequencing
- Lack of attention
- Mood changes
- Inability to use expressive language (Broca's aphasia)
Specific functions impaired by brain injury can be determined during brain injury treatment and rehabilitation. Doctors use computed tomography (CT) scans, magnetic resonance imaging (MRI), and other x-rays and specialized tests to locate injury in the brain and to predict which functions have been impaired or lost.
With treatment and rehabilitation, it is possible to restore impaired brain functions. To learn more about traumatic brain injury treatment and traumatic brain injury rehabilitation, please read other articles on this site.
[Last revision: July 2009]