Traumatic brain injury can affect the brain in many ways. Both the degree of injury and the location of the injury greatly influence the outcome and impairment. Learning about the brain’s functions will help us to later understand what happens to the brain as a result of an MTBI. First we will divide the brain’s functioning into five categories or domains. The cognitive domains are:
- Memory
- Executive functioning (for instance, planning, decision making, impulse control)
- Attention
- Language and communication
- Sensory and motor functions (visuospatial processing)
THE FIVE COGNITIVE DOMAINS:
Memory:
Memory is a primary function that is often affected by MTBI. Memory disorders interfere with numerous processes, including new learning and relearning, recall, recognition, and rote memory. Memory disorders frequently trigger apathy about learning and are often caused by acquired deficits in attention. We will cover memory in much greater detail in subsequent chapters.
Executive Functioning:
Executive functioning covers a wide variety of skills. These are the skills that the successful “executive” has to master, like time management, judgement, and planning. That’s why these operations are referred to as “executive functions.” These functions are controlled by the front of the brain. Given the physical location of the frontal lobes, executive skills are almost always affected to some degree by an MTBI. Another consideration is the wiring of the brain. Many subcortical (lower brain) regions are wired to cortical areas (higher areas of the brain) through the frontal lobes. Damage to the frontal lobes therefore affects not only the functions that are governed by the frontal lobes, but also the connections of other brain regions that run through this area. The frontal lobes govern a wide variety of functions, including awareness, insight, judgment, cognitive flexibility, rage, apathy, attention, fine motor initiation, planning, and behaviors. Impairment in executive function is beyond the scope of this book and should be addressed by professionals trained in these areas. For this reason it will not be addressed in the cognitive impairment portion of the book.
Attention:
Attention is the foundation for all the other cognitive domains. It is essentially your ability to donate a given amount of cognitive energy in order to perform the task at hand. It allows you to organize tasks into a coherent, logical pattern that makes them easier to accomplish. If executive function is named thus because of its ability to help you perform executive-type tasks, attention would be a governor—directing your cognitive resources to where they need to be at any given time. Attention is finite, as it has a limited capacity. This capacity is controlled by both arousal (how aroused or stirred up we are) and velocity (how fast we can mentally process information). Impairments in attention are among the most common symptoms associated with acquired brain damage, and because the attention system is the foundation of other cognitive processes, the ramifications of attentional deficits seem all encompassing. Fortunately, research has demonstrated that attentional deficits are often responsive to neurocognitive therapy (Sohlberg and Mateer 1987).
Language and Communication:
Language and communication disorders result from two types of dysfunction—aphasia and dysarthria. Aphasia, the loss of the ability to understand words, results from damage to the receptive and expressive centers in the frontal, parietal, occipital, and temporal lobes of the cerebral cortex. Information processing, verbal expression, and language interpretation are disrupted when injury to these parts of the brain occurs. Dysarthria is impaired neuromuscular control of the facial, oral, and laryngeal muscles needed for speech articulation. Researchers report overall good recovery of basic language skills with treatment, but deficits in analysis and expressive language skills (ability to talk) continue beyond one year after injury.
Sensory and Motor Functions:
The senses are the first step in thinking (cognition). They are our link to the outside world and allow us to monitor and process the data in the environment around us. For the most part, motor functions will only be covered in this book as they relate to the other cognitive domains (like the motor functions of speech). Motor impairments secondary to MTBI require the assistance of a professional physical therapist. The primary sensory system that we will focus on in this book is the visual system. Within the visual system we will identify two primary systems: the spatial system, which answers the question of where something is and the visual form system, which answers the questions of what something is.