What is the Difference Between Retrograde and Anterograde Amnesia?

The major difference between retrograde amnesia and anterograde amnesia is the following: Retrograde amnesia is the inability to recall past memories while anterograde amnesia is the inability to create new memories. Read the full article below for the explanation.

Sudden memory loss is more commonly referred to as amnesia. It can be either retrograde, in which the person forget what happened before their memory loss, or anterograde in which they are no longer able to remember things that happen to them after. Where retrograde amnesia is a failure in the brain’s ability to retrieve information, anterograde amnesia is a failure in the ability to store information. When people suffer from sudden memory loss, the memories that they lose are generally what are known as episodic or explicit – they forget events and facts. They do not lose their implicit or procedural memory, which is what allows us to perform functions such as operating a cell phone or riding a bike. (How Stuff Works)

Anterograde Amnesia

When a person is unable to store and retain new information but is able to recall data and events that happened previously, it’s known as anterograde amnesia. Movie enthusiasts will recognize this form of amnesia from the popular film Fifty First Dates. Though the movie was fiction, it is a reflection of events that can happen in real life, and which have. Shortly after the movie was released the news was filled with similar medical cases including a young woman whose combination of epilepsy and Functional Neurological Disorder prevent her from forming new memories, and a dental patient who had a negative reaction to anesthesia and suffered a similar loss in ability. (Medical Daily)

Anterograde amnesia is often a permanent condition generally thought to be caused by damage to the hippocampus section of the brain. This damage can be caused by an accident, as a result of surgery, alcohol, and even an acute deficiency of thiamine known as Korsakoff’s syndrome. Whatever the cause of the trauma, the person who is affected is unable to convert their short term experiences into long-term memory. (Simply Psychology) Studies have also shown that patients who have been prescribed benzodiazepines, familiarly known as tranquilizers such as Valium or Xanax, can suffer from anterograde amnesia.

Retrograde Amnesia

Retrograde amnesia occurs when a person is unable to access memories of events that happened in the past, prior to the precipitating injury or disease that caused the loss. Those who are impacted are generally able to remember meanings and other actual information, but are not able to recall specific events or situations. The severity of the condition is often indicated by what memories are retained, as under a medical principle known as Ribot’s Law, more recent memories are lost first, with more ingrained memories tending to be less likely to be dislodged. Recent studies have indicated that the extensiveness of the memory loss is a reflection of whether damage to the brain is limited to the hippocampus or also includes the temporal cortex. (Journal of Neuroscience)

Psychogenic Amnesia – The Movie Version of Sudden Memory Loss

Most of us have an image of amnesia that we get from the movies and television. We’ve all seen characters who’ve been in car accidents or struck on the head, then recover consciousness and ask, “Who am I? How did I get here?” In real life there are few instances of amnesia that involve the loss of personal identity, and these are much more commonly a result of psychological distress then of illness or structural brain damage. Our personal identity is lodged in a specific part of the brain called the median temporal lobe. It is close to the midline of the brain, and that means that is rarely impacted by external structural damage. There have been instances of people suffering from an acute brain infection that damaged this section of the brain losing all sense of their former identity. (The Guardian)

Causes of Sudden Memory Loss

Though the most obvious cause of sudden memory loss is brain damage that is a result of traumatic injury, there are other functional causes, including illness, chemical reactions from drugs or alcohol, and psychological factors.

• Stroke – People who suffer left-brain strokes tend to lose their short-term memory capabilities, while those who suffer right-brain strokes will remember events, but confuse specific details. (Stroke Association)
• Encephalitis (brain inflammation) – This condition can be either viral or bacterial, and has been referred to as an acquired brain injury with effects similar to having suffered a traumatic brain injury, a stroke, or having had oxygen to the brain cut off by a cardiac arrest. (ABC News)
• Oxygen deprivation – When the brain is depleted of oxygen, cells in the hippocampus can die. If the brain is deprived of oxygen for more than four to six minutes, the result can be death. Shorter intervals can result in anterograde amnesia. (Memory Disorders Project at Rutgers University)
• Alcohol abuse – People who are chronic alcohol users often suffer from a thiamine deficiency that progresses to Wernicke-Korsakoff Syndrome, which leads to permanent damage to the areas of the brain associated with memory. (American Addiction Centers)
• Tumors – Patients who have brain tumors can experience memory loss as a result of the tumor itself or the treatments. In undiagnosed tumors, the sudden loss of short-term memory is often one of the symptoms that precipitate diagnosis. (American Brain Tumor Association)
• Seizures – There are different types of seizures that occur in different parts of the brain.  The different types can have different impact on memory, with left temporal lobe seizures causing difficulty remembering names and right temporal lobe seizures causing the inability to recognize a person or remembering a familiar travel route.
• Medications – Antidepressants, antihistamines, anti-anxiety medications, muscle relaxants, sleeping pills, and pain medications can slow the transfer of memory from short term to long term. Statins can eliminate cholesterol in the brain that facilitates the formation of connections between nerve cells, and hypertension drugs/beta blockers can block chemical messengers in the brain that facilitate memory. (AARP)
• Head injuries – When a person suffers a severe head injury they may experience what is known as post-traumatic amnesia. (Brainline)
• Emotional shock or trauma – Known as dissociative amnesia, this is memory loss that is specific to important information from the person’s life, much of which may have been traumatic. The condition is generally temporary, and best treated through therapy. (Cleveland Clinic)

Treatment for Amnesia

Though there are no medications available for the treatment of sudden memory loss, physicians have found some success with various types of therapy, including working with an occupational therapist to replace the information that has been lost as well as to develop strategies and use technology to deal with the inability to form long lasting memories. (Mayo Clinic)