The brain has two hemispheres (sides) that are two identical appearing halves. The functions of the right hemisphere and the left hemisphere virtually mirror each other, with the right side of the brain controlling the left half of the body's movement, sensation, vision, and hearing, while the left side controls the right half of these functions.1
The Dominant and Non-dominant Hemispheres
There are a few differences between the functions of the left and right hemispheres of the brain. One hemisphere is referred to as the dominant hemisphere, and it is most associated with language and with logical skills.2 The areas of the brain that control speech and mathematical abilities are located in the dominant hemisphere.
The non-dominant hemisphere is responsible for creativity, including art and imagination.3 The non-dominant hemisphere is also responsible for integrating spatial information and for controlling a sense of awareness of 3-dimensional space.
The dominant hemisphere of the brain is usually the hemisphere opposite your dominant hand.4 For right-handed individuals, the dominant hemisphere is typically on the left side. For left-handed individuals, the dominant hemisphere may be on the right side, and this is why strokes affect left-handed people differently than they affect right-handed people.5
Strokes Of Dominant vs. Non-dominant Hemispheres
People who have experienced brain injuries to the dominant hemisphere typically experience problems on the opposite side of their body, as well as trouble with language, which is called aphasia. Aphasia can affect the ability to find the right words, the ability to understand what others are saying and the ability to read or write.
People who have experienced brain injuries to the non-dominant hemisphere typically experience problems on the opposite side of their body, as well as problems with spatial judgment and with understanding and remembering things.
- Frontal lobe: Located at the front of the brain, right behind the forehead. The frontal lobe is quite large, occupying about one-third of the cerebral cortex's total mass, and it controls personality, behavior, emotional regulation and the ability to plan, solve problems and organize.
- Parietal lobe: Located near the back and top of the head, above the ears. The parietal lobe controls the ability to read, write and understand spatial concepts. The function of the left and right parietal lobes do not completely mirror each other, with the dominant parietal lobe controlling speech and logic, while the non-dominant parietal lobe controls spatial skills and creativity. In fact, a stroke affecting the non-dominant parietal lobe can produce its own set of problems, including disorientation and an inability to recognize one's own body.7
- Occipital lobe: A small region located at the back of the head. The occipital lobe is responsible for the integration of vision.
- Temporal lobe: Located at the side of the head above the ears and below the frontal lobe. The temporal lobe controls hearing, memory, speech, and comprehension.
The language areas of the brain include several structures that are located in the frontal, temporal and parietal lobes. A stroke or another injury to any of these specialized language regions, which include Broca's area, Wernicke's area, and the arcuate fasciculus, can cause specific types of aphasia that correspond to the specific language region of the brain affected by the stroke or brain injury.
Some of the most common types of aphasia include:
- Expressive aphasia, also known as Broca’s aphasia: The inability to speak in a fluent and clear way.
- Receptive aphasia, also known as Wernicke’s aphasia: The inability to understand the meaning of spoken or written language. Often, people who have Wernicke's aphasia can speak fluently but speak with words and phrases that do not make sense.
- Anomic or amnesia aphasia: The inability to find the correct name for objects, people, or places
- Global aphasia: The inability to speak or understand speech, read or write
Management of Aphasia
Recovery from aphasia is possible. The most common form of treatment is speech therapy. Other kinds of therapy include:
- Singing therapy
- Art therapy
- Visual speech perception therapy
- Group therapy
At-home therapy, to support aphasia recovery may include:
- Playing word-based games11
- Asking questions that require a yes or no
- Cooking a new recipe
- Practicing writing
- Reading or singing out loud
Guidelines jointly published by the American Heart Association and American Stroke for stroke recovery recommend communication partner training to help improve overall speech outcomes for stroke survivors with aphasia. Communication partners can be family members and caregivers, healthcare professionals or others in the community.12
Communicating With Stroke Survivors Who Have Aphasia
While it may be difficult to communicate, people with aphasia have several options when interacting with others.
Some of these options include:
- Using pictures to make conversations easier
- Having a conversation in a quiet, non-distracting area
- Drawing or writing
- Showing people what works best
- Connecting with people by email or blog
- Showing a card that explains your condition to others
Conversely, for those people without aphasia, communicating with stroke survivors who have aphasia can be made easier with some of the following methods:
- Using pictures or props to make conversation
- Drawing or writing
- Speaking simply and slowly
A Word From Verywell
The dominant hemisphere of the brain controls language, which is one of our more important ways of interacting with the world. Any injury to the dominant hemisphere of the brain- such as stroke, tumor or head trauma- can cause aphasia.
Aphasia is challenging for the person who has this condition, as well as for loved ones and caregivers. The majority of stroke survivors who have aphasia experience some recovery, which can be optimized through rehabilitative therapy after a stroke.