Agnosia A loss of the ability to identify objects using one or more of the senses.
Agnosia is relatively rare. Agnosia is caused by damage to the parietal, temporal, or occipital lobe of the brain. These areas store memories of the uses and importance of familiar objects, sights, and sounds and integrate memory with perception and identification. Agnosia often occurs suddenly after a head injury or stroke. Usually, only one sense is affected. Frontal Lobe: The frontal lobe is one of four lobes in the cerebral hemisphere. This lobe controls a several elements including creative thought, problem solving, intellect, judgment, behavior, attention, abstract thinking, physical reactions, muscle movements, coordinated movements, smell and personality. Parietal Lobe: Located in the cerebral hemisphere, this lobe focuses on comprehension. Visual functions, language, reading, internal stimuli, tactile sensation and sensory comprehension will be monitored here. Sensory Cortex- The sensory cortex, located in the front portion of the parietal lobe, receives information relayed from the spinal cord regarding the position of various body parts and how they are moving. This middle area of the brain can also be used to relay information from the sense of touch, including pain or pressure which is affecting different portions of the body. Motor Cortex- This helps the brain monitor and control movement throughout the body. It is located in the top, middle portion of the brain. Temporal Lobe: The temporal lobe controls visual and auditory memories. It includes areas that help manage some speech and hearing capabilities, behavioral elements, and language. It is located in the cerebral hemisphere. Wernicke's Area- This portion of the temporal lobe is formed around the auditory cortex. While scientists have a limited understanding of the function of this area, it is known that it helps the body formulate or understand speech. Occipital Lobe: The optical lobe is located in the cerebral hemisphere in the back of the head. It helps to control vision. Broca's Area- This area of the brain controls the facial neurons as well as the understanding of speech and language. It is located in the triangular and opercular section of the inferior frontal gyrus.
Parietal lobe This type of damage usually results from a stroke. People have difficulty identifying a familiar object (such as a key or safety pin) that is placed in the hand on the side of the body opposite the damage (called somatosensory agnosia). However, when they look at the object, they immediately recognize and can identify it. Some people insist that nothing is wrong or ignore the problem, even when one side of their body is paralyzed.
Occipital lobe People cannot recognize common objects, such as a spoon or a pencil, even though they can see these things. This impairment is called visual agnosia. They may not recognize familiar faces (called prosopagnosia) or places (called environment agnosia).
Temporal lobe People may be unable to recognize sounds even though they can hear sounds. This impairment is called auditory agnosia.
Diagnosis Doctors ask the person to identify common objects by sight, touch, or another sense. Doctors also do a physical examination to determine whether symptoms are caused by another disorder such as an eye or a hearing disorder.
Certain standardized tests of brain function (neuropsychologic testing) may be done. These tests may involve questions and/or requests to do specific movements.
Imaging tests, such as computed tomography (CT) or magnetic resonance imaging (MRI), are done. Other tests may be done depending on the suspected cause.
Treatment Some people with agnosia improve or recover spontaneously. Others may benefit from speech and occupational therapy, which can help them learn to compensate for their impairments. No specific treatment exists.
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