Following brain injury long term memories (e.g. of personal events like weddings and birthdays), knowledge of word meanings and general information (e.g. the names of U.S. Presidents) tend to be preserved, because it is “overlearned” material. Such material has been re-used so many times in the past, it has become stored in many different places and in many different ways in the brain’s long term storage areas. What tends to most affected by brain injury is the capacity to attend to, recall and utilize newly presented or novel information.
The cognitive processes most vulnerable to brain injury are alertness (readiness to receive new information), selectivity (the capacity to focus on the material at hand and ignore or shut out distractions), encoding (the retention of the new information) and speed (the rate of overall information processing). A group of Dutch scientists has established that people without a brain injury show electrical brain activity in response to the expectation of learning something (an EEG pattern called the contingent negative varation, CNV, or “expectancy wave”), and that the CNV is decreased or absent in people with a TBI, suggestive of a “deficit in tonic alertness.”
Persons with a TBI experience a “slowing of the central nervous system clock.” They take longer to grasp new information, longer to retrieve it, longer to organize it and longer to apply it when forced to make choices or decisions. They have to work much harder to resist distraction and fatigue more easily. They are thrown off by any increase in the number or intensity of distractions in their environment and by any increase in the complexity or novelty of the information they are presented. They have difficulty making quick decisions and may become “flooded” (i.e. overwhelmed and confused) when forced to do so, especially when presented with a great many alternatives to choose from. A blow to the face which damages the frontal lobes is particularly like to cause these problems.
Trauma to the frontal lobes which alters the function of the anterior cingulate gyrus has been shown by SPECT scans to make people freeze or develop a “mental block” to carrying out activity, according to Dr. Daniel Amen in Fairfield, California. When the injury is to the medial orbito-frontal cortex (the part of the brain which lies just over the olfactory nerve bundle, which processes our sense of smell), the person experiences difficulty separating out current, ongoing reality (what is happening here and now) from memories of past events which are irrelevant to the situation at hand. They fail to inhibit memory traces, which push their way into the person’s consciousness at inappropriate times, making the person speak in non-sequitors, a process called “spontaneous confabulation.” See, Journal of Neuroscience 8/1/00 20(15)5880-5884.
Another problem is loss of the analytic capacity to detect and correct errors, which requires the capacity to link errors to the defective actions which cause them and learn how to correct them. Neuroscientists have established that the anterior cingulate cortex in the medial frontal lobe and the lateral pre-frontal cortex work in tandem to monitor actions, detect errors and compensate for them. See, Gehring W. et al. “Pre-frontal cingulate interactions in action monitoring” Nature Neuroscience 5/2000 3(5): 516-520.
Damage to either structure will impair those executive functions. Neurologist Antonio Damasio has demonstrated repeatedly that traumatic or stroke damage to a deeper brain structure (an almond shaped cluster of cells called the amygdala inside the dorso-medial temporal lobe) is associated with loss of “emotional intelligence.” The amygdala appraises the emotional significance of actions and events in terms of helpful/harmful, threatening/non-threatening, useful/not useful, desirable/undesirable, etc. It is the emotional alarm in our head, which should ring when we are in danger, e.g. about to lose a lot of money at the gaming table or about to drive into a high crime area with no police. People with amygdalar damage make the same mistakes of judgment over and over, and fail to learn the error of their ways, because their emotional alarm fails to sound.
“Cognitive performance deficits” relate to how a person processes information, not how much he knows or how smart he is. A very smart, well read person with a TBI can test in the superior range on vocabulary but test in the impaired range on various tests of attention and short term memory. Slowing of the rate at which the brain processes new information, or draws upon old information to solve new problems, is one of the most significant impairments of functioning caused by a TBI.
This is more true today than ever before, because of the speed of information processing required of us in this age of Information Technology, marked by the Internet, Palm Pilots, Web TV, cell phones, 2 way audio-visual conferencing, PCs with pentium microprocessors, laptop computers, and other technological innovations which continuously accelerate the pace of information creation, information delivery and decision making Learning to manage your emotional response to reams of new information (taking a deep breathe, breaking it down into chunks and analyzing it step by step instead of hyperventilating and feeling doomed); role playing situations involving decision making in a support group; using assistive technologies (e.g. tape recorder, notebook, day planner); and gradually boosting cognitive processing speed with computer-based cognitive therapy programs; will surely help.
Not all “thinking” problems are caused directly by damage to the parts of the brain which analyze information. Some cognitive losses stem from insomnia. Others are attributable to traumatic impairment of vision, hearing or short term memory. Some result from temporary incapacitation by headache pain. Identifying these problems and working to fix them (through new glasses, vision therapy, a hearing aid, auditory therapy, etc.), would help increase your cognitive processing speed.
A great deal of medical literature on “outcomes” from TBI stresses psychological and behavioral problems as the ones which last longest, and are most predictive of inability to return to work (e.g. being easily frustrated, irritable and socially inappropriate). This is not always the case. I have represented clients with positive outlooks and good emotional self-control, who could not successfully return to their jobs on account of persistent cognitive limitations from their TBI, such as poor auditory retention or inability to multi-task. One recent study found that cognitive impairments were more likely than any other problems to keep mild TBI patients from successfully resuming work. See, Journal of Head Trauma Rehab 15(5): 1103-1112 Oct. 2000.