Apart from dementia, the brain can be affected by concussion, infections such as COVID, and stroke, and a variety of degenerative diseases. This page is a brief look at how you might “model” the impairment, so that you can work around it.
The coronavirus before vaccines were available, had an acute phase in which vigorous confrontation between the body’s white cells and virus was taking place in the airways. Some people were affected over many weeks, during which the battle had also occurred in the brain, sometimes leaving inert white material behidn. Sufferers described this aftermath as intense fatigue and “brain fog”. This metaphor is not very helpful, as the impairment is not visual. Instead it could be modelled as impaired attention and information processing. A standard neuropsychological test for this is trail making. In the example below, the patient has to put the pen on number “1” and draw a continuous line to “2” and continue until “8” is reached. The main part of the test involves letters as well as numbers, so considerable concentration and information processing is required. The score for the test is how many seconds it takes.
It turns out that both persistent COVID and concussion have one main effect – to reduce the rate of information processing. Although this can be quite discouraging, it does enable the sufferer to recognise their new, reduced, limits. This means they can write a Post-it note or dictate a voice recording on their phone if the task is beyond their revised limit.
A cerebrovascular accident, known as stroke for short, needs a different “one-sided”
model. A bleed or clot usually affects one cerebral hemisphere only. (Lesions in the brain stem are also possible). The nerves cross over. If the damage is to the left hemisphere, loss of sensation on the right side of the body will be experienced and speech may be impaired. If the damage is on the right, sensation loss on the left side of the body will be experienced and visual information may be impaired. (For a few left-handed people a different pattern applies.) There may also be loss of voluntary movement and a blank visual field with missing information.
Recognition that a stoke is occurring needs rapid attention by paramedics and doctors to prevent further damage. Then there will be days of slow and partial return of function as the workaround phase begins. If aphasia – selective loss of speech and language – has occurred, there will be gaps in lexicon, comprehension and possibly phonology. This is the point at which a bilingual person can see the problem more quickly and work around the gaps.
Japanese speakers are in an unusual and slightly advantageous situation here, as their language is stored on opposite sides of the brain. Japanese uses the Chinese script – kanji (‘Han characters’) , but also syllabic scripts – kana, which are learned first in childhood. A stroke in the left hemisphere of the brain would probably cause forgetting of kana. The kanji, used for adult reading, would be unaffected. Conversely a right hemisphere injury would make the Chinese characters unreadable, but the script learned in childhood would be unaffected.
The image below compares the way a rare word “gnat” might be stored in the two languages. In the English speaker’s brain, the spelling has a “g” at the beginning, but this is not present in speech, which makes it hard to retrieve and a dictionary may not help. In Japanese the sound is “buyo”. The spelling uses two kana syllables. At the same time, in the right side of the brain, two Chinese characters, which in this case look a bit like the referents, represent “insect” and “inside”. So the Japanese speaker has an easier task in working around a stroke.
Rehabilitation of brain injuries thus has fairly simple strategies for someone who has learned a second language.