What Is Meant By The Term Cognitive Impairment?

At times, the term "disordered thinking" is used interchangeably with "cognitive impairment", but technically speaking, disorders of thought involve abnormal thought content  (delusions or ideas of reference) or thought process (loose associations, tangential thoughts, or flight of ideas).  The distinction may be confusing.

Cognitive impairment may occur before other symptoms of schizophrenia.  It involves problems with attention, concentration, memory, information processing and what is called "backward masking dysfunction".

Furthermore, if we have problems with either attention or concentration, we will have difficulty retaining information by delivering it to short-term and then long-term memory.  

Some individuals with Attention Deficit Disorder often do remarkably well in school in spite of their disability.  This may be because they can attend long enough to allow information to be transferred to short term memory.  

People with depression consistently experience problems in the area, probably because they cannot maintain concentration.

The problems that people with schizophrenia experience with memory are often quite unique.  These people may have problems associating an event with the details of that event.  They may remember the event but cannot recall the details,  such as when, where and how it occurred.

Information processing may involve information in general.  When it involves the connects between words their speech becomes unintelligible.  This is called "word salad".  They may associate words because they sound the same and not because they have the same or related meanings or are naturally connected with one another.  This results in what is referred to as "clang associations.

Backward masking dysfunction involves a person's inability to remember a preceding event.  This may occur even if they have normal working memory.  This is usually the result of some distraction such as hallucinations or some disturbing internal process.

Why do people with schizophrenia experience these difficulties?  They are probably related to structural and functional abnormalities in their brains.  Function has to do with activity and may represent reduced or increased levels of activity.  

Imaging techniques such as MRI (Magnetic Resonance Imaging) and CAT (Computerized Axial Tomography) reveal a loss of brain tissue in people with schizophrenia, especially in the areas of the brain known as the prefrontal cortex and temporal lobes.

PET (Positron Emission Tomography), an imaging technique that reveals brain tissue activity rather than structure, demonstrates abnormalities in the brains of people with schizophrenia.

The prefrontal cortex affects logical thought and verbal memory, which may affect clear and fluent speech.  Aggression has also been linked to this area.  Abnormally increased activity in the frontal and temporal lobes is associated with auditory hallucinations.  Reduced tissue volume in the temporal lobes is related to problems in other areas of the brain that influence memory, emotions, as well as delusions and hallucinations.