Biological Perspectives on Memory

In the first section of this chapter we saw how memory research was influenced by the advent of computers. Neuropsychology also influenced memory research, beginning with the observation of some brain-damaged patients in the 1960s.

The story of H.M.

Henry Gustav Molaison was long known in the literature as patient H.M. He suffered from seizures caused by abnormal tissue deep within the brain. During a brain operation, a surgeon removed areas near the temporal lobe and hippocampus.

The operation was a success, in one sense: it halted H.M.'s seizures. Before the operation, H.M. had at least one severe seizure per week. After the operation, he was nearly seizure-free.

However, after the operation, H.M. could no longer transfer memories from primary (short-term) to secondary (long-term) memory. This finding was very influential in the field of psychology, because it showed that the two systems were biologically distinct.

What was H.M.'s problem, after the operation?

H.M.'s primary memory, after the operation, was normal. He could hold a normal conversation, and his memory span (primary memory capacity) was normal. However, when his attention was distracted, H.M. forgot everything in his mind a moment before.

This condition is called anterograde amnesia. The word amnesia refers to any forgetting syndrome. Anterograde amnesia refers specifically to a loss of memory for events after the traumatic event causing the amnesia.

H.M. could remember most of what happened in his life before the operation. However, his life after the operation was a complete blank to him, except for a few emotion-laden events.

When shown a Kennedy half dollar, H.M. identified Kennedy and said Kennedy had been assassinated, although this happened more than eight years after the operation. After his father died, H.M. remembered this fact vaguely.

What is anterograde amnesia? What did the Kennedy half dollar reveal?

The extent of H.M.'s problem was apparent during his return visits to the medical center.

During three of the nights at the Clinical Research Center, the patient (H.M) rang for the night nurse, asking her, with many apologies, if she would tell him where he was and how he came to be there.

He clearly realized he was in a hospital but seemed unable to reconstruct any of the events of the previous day (when he had been driven to Boston for the check-up). On another occasion he remarked, "Every day is alone in itself, whatever enjoyment I've had, and whatever sorrow I've had."

Our own impression is that many events fade for him long before the day is over. He often volunteers stereotyped descriptions of his own state, by saying that it is "like waking from a dream."

His experience seems to be that of a person who is just becoming aware of his surroundings without fully comprehending the situation, because he does not remember what went before. (Milner, Corkin and Teuber, 1968)

Where is the "gatekeeper" for event memory?

Larry Squire of the San Diego VA Medical Center found a stroke victim with anterograde amnesia similar to that of H.M. After the man died of natural causes, an autopsy showed that he had a normal brain except for one tiny area of degenerated cells in the hippocampus.

This tiny group of cells was in the middle of a circuit known as the trisynaptic circuit of the hippocampus. Squire theorized that this circuit pulls together information from various areas of the cerebral cortex, acting as a "gatekeeper of memory" (Hostetler, 1988).

Clive Wearing

Clive Wearing is a famous patient who lost his event memory in 1985 after a brain infection: encephalitis. Clive does not remember a moment of his life, before and after his illness, so he was more impaired than H.M. (who only lost memories for after his operation).

If Clive is questioned about his consciousness, he always says he feels like he is just waking up. That is like H.M., who said he always felt like he was waking up from a dream.

What does Clive Wearing always say about his present state of consciousness?

Despite lacking all episodic memory, Clive learned his way around a new environment when he was moved to an assisted care home in the English countryside. If he wanted to make a cup of coffee, he knew where to get the ingredients and how to put them together (showing he formed new declarative and procedural memories).

Clive wife reported that his personality and intelligence remained intact. He kept his skill at playing the piano, although when he sat down at the piano bench, he would often volunteer that he had never played in his life.

However, once he was seated at a piano, the situation would elicit his old skills, and he would start playing beautifully. What Clive lost was not his skills (procedural memory) but access to memory for the events of his life. He continually said (and wrote in his journal), "I am now becoming conscious for the first time."

Which memories did Clive lose, and which were preserved?

Several videos about Clive are on YouTube, and they make fascinating viewing. The first, from an old PBS series called The Mind (1988) shows Clive several years after his illness in 1985. The second video revisits Clive and his wife (both with slightly grayer hair) in 1998.

In both cases, Clive greets his wife Deborah with great enthusiasm every time. He knows who she is, and that he loves her, but does not remember a thing about her or when she has visited in the past.

The "Onion Effect"

People with Alzheimer's Syndrome, a degenerative brain disease of old age, often suffer from anterograde amnesia similar to H.M.'s. They tend to forget recent events, such as conversations held a few minutes earlier.

As the condition worsens, forgetfulness may extend back for years, and the old person may fail to recognize his or her grandchildren. In the final, most pathetic state, the old person may call visitors by the names of long-dead brothers and sisters.

It is almost as though memory is organized like an onion, in layers. The most recent layers peel off first, followed by the older ones.

What is the "onion" effect in memory loss of old age?

A student describes the peeling away of memories.

In December, my great-grandmother will be 103 years old. She lived a remarkably healthy life up until about three years ago. Today she is bedridden or confined to a wheelchair most of the time.

She lives very little of her conscious life in the present; her mind is now in the past. After studying the lesson on Memory, I realized she lost her memory and retreated to the past by going through the "onion peeling" or layer process we heard about.

First of all, she began to forget the most recent things on her mind. She commonly misplaced things or forgot what she was doing.

When she made homemade rolls, she would forget they were in the oven. Therefore, to prevent them from burning, she would pull up a chair and sit in front of the oven until they were done.

The next major change was that she forgot her great-grandchildren. When we visited her, we would have to tell her who we were (partially due to bad eyesight) and then she would remember us.

Her next loss of memory was for her grandchildren. She once asked my grandmother who the girl was my father married. My father is actually her grandson-in-law and my mother is her granddaughter.

Just recently she has lost her memory for her own children. Today she lives in the past. Once when we visited her she had a very worried look on her face. When asked what was wrong, she replied "I'm worried about the baby."

When asked what was wrong with the baby, she replied, "It's sick." We asked who the baby was and she replied "George." George is my grandfather and her son. [Author's files]

Researcher Barry Reisberg at the New York University Medical Center documented this effect. He found that memory loss due to Alzheimer's Syndrome exactly reversed the cognitive gains of a young child.

The first abilities to disappear were adult skills such as financial management. Next came clothing selection, dressing ability, bathing, and control of bathroom functions.

What did Reisberg find to be typical of memory loss in Alzheimer's patients?

In late stages of Alzheimer's disease, speech ability dwindled to a few words, then only one. Finally this one word was lost, followed by the ability to sit up.

The last thing to go was the ability to smile. That is the first organized behavior of babyhood, which appears around the age of two months (Turkington, 1985).

Retrograde and Anterograde Amnesia

Retrograde amnesia is the loss of memories that formed before a trauma. If a person has a car crash and does not remember the minutes leading up to it, that is retrograde amnesia.

By contrast, anterograde amnesia, H.M.'s type, prevents new memories from being formed. The amnesia is for events after a trauma such as brain injury.

How is anterograde amnesia distinct from retrograde amnesia?

Think of the injury as a point in time. Loss of memories before this point is retrograde amnesia. Retro- means backward.

Loss of memory for the time after an injury is called anterograde amnesia. Antero- means forward.

H.M. had mostly anterograde amnesia, but he also had a bit of retrograde amnesia. The two years before his operation were blurry to him.

Clive Waring had both retrograde and anterograde amnesia. He could not remember events before or after his encephalitis.

Retrograde amnesia after a trauma such as a car accident is often a form of retrieval failure. We know this because those memories can come back.

What is evidence that retrograde amnesia involves retrieval failure, not storage failure?

By contrast, lost memories in anterograde amnesia never come back. Probably they were never formed in the first place.

The following essay from a student illustrates both retrograde and anterograde amnesia triggered by a powerful hit on the football field.

My senior year in high school was looked upon at Portal High as the year for a great football season. We had a tough schedule, including the defending state champions in Class A: Johnson County High.

Herschel Walker, who had just graduated, helped them to the championship. But this was another year, and we were expecting great things from our team.

The night we met Johnson County, our team was really ready emotionally. We shut out a team in our first game and that added enthusiasm for this one.

When we kicked off to Johnson County to start the game, I missed a great opportunity to hit the return man because I shied away. But we held them and scored ourselves.

On the ensuing kickoff they ran to my side again. I made up my mind I was going to put a hit on the return man this time. The kickoff seemed like an instant replay of the first, except this time I hit the runner going full speed.

It was Herschel's little brother Lorenzo, who weighed 185 pounds. At full speed, the impact of the hit was tremendous. I lay on the ground a couple of seconds and finally struggled up with the help of my teammates.

At that moment, I did not know what was going on. When our team got in the huddle I asked how we scored the touchdown.

They asked if I was all right, and (they told me later) our quarterback held up two fingers and asked how many I saw. I do not remember any of that.

Only after the half was over did I begin to remember how we had scored and the tackle I made on the kickoff. After that is a complete blank.

While I was watching the second half, I tried to recall parts of the first half, but it was lost. To this day most of the first half after my hit is lost to my memory. [Author's files]

How did the football player's experience illustrate characteristics of the two varieties of amnesia?

The retrograde amnesia (his loss of memory of how the team scored) was temporary. The memory came back. The anterograde amnesia (remembering what happened for the rest of the half after the hit) did not come back. This is typical of what happens with retrograde and anterograde amnesia.

Chemical Modulation of Memory

McGaugh (2000) summarized four decades of research showing that chemicals in the nervous system influence memory. In particular, low doses of adrenaline secreted within the nervous system very soon after learning (within about 30 seconds) seem to encourage memory formation.

This process by which memories are strengthened over time, following an experience, is called consolidation. McGaugh points out that the brain does not "need" consolidation, because some forms of memory are extremely fast.

McGaugh suggested that consolidation evolved because it gives emotions a chance to have an impact on memory formation. Emotions act over an extended period of time, so a process that gradually strengthens memory helps to insure that important events (those remaining emotionally important for minutes or hours) are better remembered.

What is memory consolidation?

Adrenaline helps memory, but only in small doses. Rats given a small dose of adrenaline can remember classical conditioning even if it happens while the rats are deeply anesthesized, a remarkable finding that we will discuss more on the next page (Weinberger, Gold, and Steinberg, 1984).

Larger doses of adrenaline actually hurt memory. If a rat receives a large dose of adrenaline, the rat's memory performance worsens.

McGaugh noted that the effects of adrenaline are very strong. They are also very widespread in the animal kingdom.

The obvious explanation is that events which alert an animal (such as the presence of danger or opportunity) are also the events worth remembering. Events that stimulate adrenaline are selected for memory.

Why would the effect of adrenaline be useful for the brain?

Opiate transmitters like the endorphins have an effect opposite to adrenaline. They reduce the likelihood animals will remember an event (Cicala, Azorlosa, Estall, & Grant, 1990).

To have this effect, they must be injected immediately after training. This could cause anterograde amnesia after a physical trauma, such as the "big hit" that affected the football player above, because such a blow to the body probably stimulates endorphin release./p>

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References:

Cicala, G. A., Azorlosa, J. L., Estall, L. B., & Grant, S. J. (1990). Endogenous opioids interfere with second-order Pavlovian fear conditioning. Psychological Science, 1, 312-315.

McGaugh, J. L. (1980, December). Adrenaline: A secret agent in memory. Psychology Today, p.132.

McGaugh, J. L. (2000) Science, 287, 248-251.

Hostetler, A. J. (1988, April). Exploring the 'gatekeeper' of memory. APA Monitor, 19, 3.

Milner, B., Corkin, S, & Teuber, H-L. (1968). Further analysis of the hippocampal amnesic syndrome: 14-yr follow-up study of H.M. Neuropsychologia, 6, 213-234.

Turkington, C. (1985, November) Alzheimer's losses reverse child's gains. APA Monitor, p.17.

Weinberg, N. M., Gold, P. E., & Sternberg, D. B. (1984) Epinephrine enables Pavlovian fear conditioning under anesthesia. Science, 223, 605-607.

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