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I have, on many occasions, railed against "stupid movie science" in the form of getting brain science wrong, or being unimaginative regarding use of brain disorders. As I have often said, the most misused brain disorder in TV (especially soap opera), movies and books is amnesia. Today's blog is meant to introduce the reader (and writer) to a number of other "Axxxx" diseases that can be used with interesting consequences in fiction.
epilepsy blogs last year.
Agnosia: A special case of amnesia, agnosia results from very localized damage to the brain. In particular, the damage occurs to the association areas of the brain that process the basic sensory information and deliver it tot he parts of the brain that make decisions and control our actions. In the visual areas, agnosia manifests as "visual neglect" the subject ignores what is in one part of the visual field, even though the eyes and pupils react to stimulation of that part of the field, and there is evidence that *some* of the sensory information is getting through to other parts of the visual system: for example, the eyes can track a moving object through that field, and the a subject shown an embarrassing picture to that part of the field will blush and act embarrassed without being able to say why. Neglect can apply to the body as well, a patient may not be physically aware of sensation from a limb or part of the body, even though the spinal cord, motor control, reflexes and pain reactions are intact. Frequently the damage is to the thalamus, which relays sensory information through the brain, or to specific nerve tracts in the Parietal Lobe.
Ataxia: Often confused with simple clumsiness, ataxia is a failure of the brain to provide coordination to movement. Ataxia may be accompanied by tremor, rigidity or weakness, and is thus hard to diagnose differently than other diseases. However, the key finding is the inability to coordinate the movement of more than one arm or leg at a time, clumsiness that occurs when a person stops concentrating on the movement, or the inability to stop a movement once it is started. Ataxia usually results from damage to the cerebellum, but may also be caused by damage to deep brain nuclei or brainstem.
Apraxia: Like ataxia, apraxia results in a failure to get the body to do what the patients wills it to do. In a typical case, it is easy for a patient to bend down, pick up a baseball that is in their way, and toss it away. However, if the patient is told to pick up the ball, or verbally expresses the desire to throw the ball, they cannot do it. All of the motor and sensory abilities - including coordination - are intact, but the patient cannot turn intent into action. Damage to the premotor areas of Frontal Lobe or the associational areas of Parietal Lobe are usually involved. Neither the motor nor sensory cortex areas are damaged, though, and all abilities remain intact.
Aphasia: When apraxia occurs within the speech centers, it is termed "aphasia." We all experience minor bouts of aphasia that occur as "tip of the tongue" phenomenon, but these are usually due to the inability to perform the appropriate memory recall of a word. Aphasia is different, because a patient can hear the word, write the word, choose it out of a list, but cannot speak it. It is a specific disorder of Broca's area, which sends signals to the motor cortex for diaphragm, throat, tongue and mouth to form words. Broca's Area is in the Frontal Lobe, just below and forward of the motor cortical areas for the face and neck, and lying just over a bundle of nerve axons (the arcuate fascilus) that run from sensory association areas of the Parietal Lobe, underneath Wernicke's Area (language), Broca's Area, and terminate in the "cognition" ares of the Frontal Lobe. Aphasia is frequently caused by damage to Broca's Area or the arcuate fasiculus.
Alexia: Also known as visual aphasia, this is a failure of language and speech generation - in this case the failure to recognize and understand words. Alexia is usually visual, and shows as the inability to recognize that printed or written characters represent language, i.e. "word-blindness." There are auditory forms, but those are usually associated with obvious hearing disorders. If the person retains the ability to speak and write words, then they have alexia without agraphia and the damage is between the visual cortex and Wernicke's area and confined to the lateral Parietal Lobe. Damage to Wernicke's Area also causes loss of ability to write and speak coherent language. Note the similarity to "dyslexia" and you can see how important the Wernicke/arcuate fasciculus/Broca linkage is to transforming sensory input to language.
So there, five new "A-words" to add to amnesia and spice up the plot of that new novel or movie. The unfortunate thing, though, is that these disorders are not new, and doctors face them every day with stroke, head trauma and battlefield trauma patients. Then again, the best stories come from real life incidents.
Thanks for reading, and tune in next time for some book reviews and a refresher on brain basics for The Lab Rats' Guide to the Brain!