Right Brain, Left Brain: Memory and Cognition After Stroke

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Presented by: Simon Tan, PsyD, ABPP-CN
Clinical Assistant Professor, Neurology and Neurological Sciences
Stanford University Medical Center
March 30, 2011

Lecture Overview:

While most people know about the physical aftereffects of a stroke, there are also many associated invisible consequences that can affect cognition and emotion. Strokes can cause language disturbances, coordination or balance difficulties, confusion, or sensory loss. Though physiologically based, many people are reluctant to discuss these unseen difficulties, which can hamper function and complicate interactions.

A stroke, or cerebrovascular accident (CVA), occurs when blood supply to part of the brain is disrupted, causing brain cells to die. The most common cause of a stroke is blockage of an artery in the brain by a clot (thrombosis), usually stemming from a buildup of plaque caused by high blood pressure, cholesterol, obesity, or other risk factors related to heart disease. Hemorrhagic stroke occurs when a blood vessel breaks and leaks blood in or around the brain. An embolism, or embolic infarct, occurs when a blood clot travels through the bloodstream and lodges in a blood vessel in the brain.

“Mini” strokes called TIAs may not cause any lasting symptoms but they can still damage brain tissue and be a sign of bigger problems to come, explained Simon Tan, PsyD ABPP-CN, a Stanford neuropsychologist, at a presentation sponsored by the Stanford Stroke Support Group.

“The symptoms of a stroke relate to its location,” said Dr. Tan. “The effects depend on which part of the brain has been affected. In visual tests, people with a right-side stroke may have visual perception changes, while people with a left-side stroke may suffer some form of language disturbance.

Whether the stroke occurs on the left side or the right, common symptoms include reduced attention, reduced short-term memory, emotional impacts, and weakness on one side.

Left Side: Language and Comprehension
The left side of the brain is related to language. A stroke situated on the left can damage the ability to communicate, which can lead to depression, withdrawal, and stress. Dr. Tan explained some of the categories involved in left-side strokes:

  • Aphasia affects the ability to express and understand verbal or written language. A person with aphasia may speak in short or incomplete sentences, make up words (neologism), forget the proper word or substitute one word for another (semantic paraphrasia), or change words and sentences in an inappropriate way. People with aphasia can have trouble comprehending conversations, leading to social misunderstandings.
  • Apraxia is the loss of the ability to carry out purposeful movements, despite having the physical capability of performing the action. There can be diminished ability to use objects for commonly learned activities like dressing and brushing teeth.
  • Dyscalculia refers to a reduced ability to calculate or comprehend mathematics.
  • Amnesia is the loss of short-term memories and the inability to retain new information. They can often recall the past but not events from a day or a week ago.
  • Emotionality is a common aftereffect of stroke. People may develop behavioral changes: They may become cautious and slower to participate or make decisions, or they may become easily frustrated and overreact.

Family members and caregivers need to adjust to a new way of communication as well, said Dr. Tan. He suggests you use a normal voice but speak slowly using simple words. Ask yes-or-no questions. Don’t be wordy.

“The best response is to be patient,” said Dr. Tan. “Try to give the person independence and resist the temptation to jump in to finish a sentence. “

Right Side: Perception and Judgment
The right side of the brain controls visual-spatial functions, such as judging the distance, position, size, and speed of objects. People who had a right-side stroke can have trouble with depth perception and with judging where they are in relation to their surroundings. This makes it difficult to locate objects, walk up or down stairs, bring food to their mouth, or get dressed.

The right side of the brain is also related to intuitive thinking, so reasoning and solving problems may be affected. And many people lose the ability to read the subtleties of social interaction and the capacity to relate to other people, said Dr. Tan.

  • Hemispatial neglect: Some right-brain stroke patients may ignore people or objects on their left sides. In extreme cases, they may deny ownership of their own left arm or leg (somatoparaphrenia).
  • Anosognosia: Right-side stroke patients can manifest a lack of insight and may not be aware of their own mental and physical changes. They may show poor judgment of their abilities or deny their changed condition. Since they believe nothing is wrong, they are less willing to take part in rehabilitation and may endanger themselves by doing normal activities with diminished capability.
  • Anosodiaphoria: Some people become indifferent or show lack of concern that there have been any changes following a stroke. They are poorly motivated to change making rehabilitation difficult.
  • Visual spatial dysfunction: Right-side stroke patients can lose the ability to associate the parts that make up a whole, so they can misperceive situations. Reduced visual memory means they cannot recall the location or shape of objects.
  • Social misperception: With trouble interpreting nuance, body language, and nonverbal clues, patients have trouble following social rules and recognizing others’ perspectives. They cannot pick up on subtleties like sarcasm or humor.

Behavioral changes can range from impulsiveness to trouble describing emotions. Patients are taught to turn their head often to scan more of their environment and to put objects back in the same place.

Recovery depends on the extent of damage and how quickly blood flow is restored to the brain. For most people there is a relatively rapid recovery within the first few months, but it generally takes about two years to determine how much physical and mental ability will be regained. Dr. Tan said that left-handed people tend to recover better from language problems, and that right-brain stroke patients who ignore one side have poorer outcomes.

“The brain as it recovers may reroute its circuitry to compensate for what has happened,” he said. ‘Every brain is different.”

About the Speaker
Simon Tan, PsyD, ABPP-CN, is a clinical assistant professor of neurology and neurological sciences, with a special interest in behavioral neurology and dementia-related disorders. He received his doctorate in clinical psychology from Yeshiva University in New York, and completed an internship in clinical psychology and two fellowships in clinical neuropsychology at Harvard Medical School. He was a clinical rehabilitation neuropsychologist at NYU Medical Center before coming to Stanford in 2005.

For More Information:

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About Dr. Tan

Stanford Center for Memory Disorders

Department of Neurology & Neurological Sciences

Stanford Stroke Center