Muriel was driving her car when she was struck by another vehicle. She hit her head and lost consciousness, and a friend traveling with her was killed. She eventually made a full physical recovery, but she had some new problems. She forgot conversations, missed appointments, failed to meet deadlines, lost things, and asked the same questions again and again. How would you explain these new problems? You could consider several possibilities. For example, you might wonder if she is still upset about the accident, is mourning her lost friend, or perhaps feeling guilty about having survived. Such emotional turmoil could impair concentration and cause forgetfulness. But how could you know whether, instead, brain damage was the cause? You might look at pictures of her brain structure with magnetic resonance imaging to spot areas of gross brain damage. But those pictures can't tell you if damage is fresh or old. Most important, you would still have to decide if the damage is relevant to Muriel's current problems. In other words, you would need to decide if the damaged regions are those which, when injured, could cause memory loss. Further complicating the picture is that brain damage on a microscopic or cellular level can impair psychological functioning but be invisible on an imaging scan. To help sort out all these possibilities, you need a way to assess Muriel psychologically, to test her mental abilities carefully. You must then use a detailed knowledge of psychology and brain function to decide if the pattern of findings suggests brain dysfunction, and if so, where it is. These are some of the tasks that neuropsychologists perform.
Neuropsychology is the field of study that seeks to understand how brain processes make human behavior and psychological functions possible (Heilman & Valenstein, 2011). Neuropsychologists are interested in a wide range of human abilities, including aspects of cognitive functioning (e.g., language, memory, attention, mathematical, and visuospatial skills), motor functioning (e.g., learned skilled movements, gross and fine motor skills), emotional functioning (e.g., motivation, understanding and expressing emotion, anxiety, depression, euphoria), social functioning (e.g., prejudice, social judgment, interpreting social information), and personality traits (e.g., extraversion, neuroticism). Neuropsychologists study how brain operations control such processes and how this control breaks down due to brain dysfunction (e.g., physical trauma, stroke, infection, neurodegeneration) or psychological disorders (e.g., posttraumatic stress disorder, clinical depression, schizophrenia).