The word cognition is used commonly but inconsistently for “thinking” types of activities. Cognition could be thought of as the functions of the nervous system other than those that are motor, sensory, autonomic, or emotional. Consciousness is tougher to untangle from cognition, but there are many cognitive functions that can be lost without a person being thought of as having lost consciousness, at least by most people.
The different aspects of cognition are tested with the mental status examination, which, depending on the clinical situation, can be highly variable in length. A typical neurological mental status examination includes assessment of arousal (responsiveness to stimuli), orientation (to person, place, time, or situation), attention (maintaining focus on a task), language (expression, comprehension, repetition, or naming), memory (forming new ones or remembering old ones), fund of knowledge (facts or current events), and executive function (controlling the other cognitive functions and behavior to achieve goals). Some of these functions are associated with specific brain areas, such as certain areas of cerebral cortex, while others appear to arise from diffuse neuronal networks of large areas of cerebral cortex or subcortical structures. Language functions occur mostly on one side in most people, which is called their dominant cerebral hemisphere, and the other is called their nondominant hemisphere. Most people are left hemisphere dominant.
Thought process and content are also aspects of cognition that are often affected by psychiatric disorders, and occasionally by neurological disorders. Aspects of thought process to examine include whether it is logical and goal-directed, as well as the speed of mentation. Slow mentation is called bradyphrenia. Aspects of thought content to examine include delusions, hallucinations, and illusions. A delusion is a fixed, false belief that is unusual for that culture. A hallucination is a sensory perception without a stimulus. An illusion is a misperception of a stimulus. An example of an illusion would be seeing a snake when looking at a stick, while a hallucination could be seeing a snake when nothing is there.