Cognitive function is the term used to describe a person's state of consciousness (alertness and orientation), memory, and attention span. A mental status examination (MSE) is a standard test used by healthcare professionals to measure a patient's overall mental health. Evaluating a patient's cognitive function includes, first of all, measuring their level of alertness and orientation.

Awareness and thinking depend on organized thoughts, personal experiences, emotions, and mental processes, each existing in a special region of the brain. Self-awareness requires sensing this personal stream of thought and emotional experiences. When a person cannot maintain a logical sequence of thoughts, and when this goes along with not being able to pay attention and being disoriented, this describes confusion.(1)

Alertness measures a patient's awareness of his or her environment and situation. Abnormal states range from confusion to lethargy (tiredness), delirium (confusion), stupor (daze), or even coma. Orientation is a person's ability to describe their knowledge of person, place, and time. Asking simple questions such as the patient's name, where they live, the current date or day of the week, or season of the year can be used to evaluate orientation. Disorientation is very often linked with organic brain syndromes (for example, dementia).(2)

Confusion describes a behavior where there is decreased mental clearness, consistency, understanding, and being able to reason.(1) Lack of attention and disorientation are the main early signs; however, as the confusion gets worse, there is a decrease of memory, awareness, understanding, problem solving, language, actions, functioning in one's environment, and emotional behavior.

Changes in a person's state of consciousness, such as with confusion, lethargy, and delirium, may be caused by many medical conditions including fever, ischemia (decreased blood supply), trauma, or brain diseases. It may also be caused by some drugs or toxins. Other causes are hypoglycemia (low blood sugar), azotemia (nitrogen waste products in the blood), liver failure, hypercalcemia (increased calcium in the blood), or a lesion that can develop at the base of the brain.

Memory is a person's ability to remember information in the past and the present. Memory is considered the most common and the most important cognitive ability that can be lost. Healthcare professionals may test a patient's memory by asking questions about the history of their present illness or what they had to eat at a recent meal. They may ask a patient to remember three different words, such as a color, a person's address, and an object, then later in the interview, ask if the patient can remember what they were just asked. These are tests of present or short-term memory. Questions concerning family history, date of birth, and facts from a person's past test a patient's past (distant) memory. Delirium, dementias, amnesia, Korsakoff's psychosis, and anxiety are conditions associated with an impaired memory.(2)

Dementias are disorders with symptoms of memory loss and a decrease in cognition and the ability to reason.(3) Dementia, sometimes called "senility," is not a part of the normal aging process, and shows that some other disease may be present. Dementia affects a person's ability to be successful in carrying out their activities of daily living.(4) Accurate diagnosis of the disease that is present is necessary for treating the dementia properly.

The healthcare professional also measures attention span and the ability to concentrate in evaluating cognitive function. They ask the patient to solve a short series of problems such as subtracting seven from 100 in sequence (100, 93, 86, 79, and so on). The healthc