Case Studies of Human Patients with Amnesia in Understanding of Short- and Long-term Memory

It goes without saying that the study of human memory has been well researched and studied for psychologists and neuroscientists for many years, needless to say, there have been several case studies with amnesic patients to help psychologists gain an insight into the understanding of short- and long-term memory. There have been several amnesic patients that have helped Psychologists and Neuroscientists understand to human memory and how certain parts of the brain are essential for short- and long-term memory. Memory is an active system that receives, stores, organizes, alerts, and retrieves information and is integral in cognition in many ways. The amnesic patients chose to help with the understanding of short- and long-term memory have either had Retrograde amnesia or Anterograde amnesia or both, Anterograde amnesia is an inability to make new memories following their trauma whilst Retrograde amnesia on the other hand is not being able to recall memories prior to patients trauma.

To start with one of the most popular amnesic case studies which involved Henry Gustav Molaison who suffered from severe epilepsy from 10 years old and started to have over 10 epileptic fits a day. In 1953 Henry met William Beecher Scoville who was a neurosurgeon who worked at Hartford hospital in America. William suggested that Henry undertook an experimental procedure which was for the removal of the medial temporal lobe to try and cure his severe epilepsy, this was done so by the removal of the Hippocampus, Amygdala, and parts of the lateral temporal lobes. The surgery was partially successful in controlling the seizures, but Henry had developed severe Anterograde amnesia, he also developed some Retrograde amnesia. Due to Henry’s new condition, he became one of the most studied men in history known as ‘Patient HM’. Henry was studied for 50 years of his life until he died in 2002 at the age of 82.

Some of the main findings that neuroscientists and psychologists found in Henry's condition was that Explicit, Episodic, and Semantic memory was based in the Medial temporal lobe (Hippocampus). Henry’s working memory was intact, and that showed that the Hippocampus was not critical for working memory. The difficulty that Henry had learning new information shows that the Hippocampus is essential for forming new memories and storing short-term memory into long-term memory. Henry's personality, intelligence, judgment, and IQ was unaffected suggesting that these are not located in the Hippocampus but in fact in the frontal lobe. (Corkin 2002).

Explained that these findings showed that the Hippocampus was the ‘gateway’ to permanence memories, and it is integral in early consolidation of memories but does not necessarily need to be there intact for accessing of longer-term memories that have already been consolidated. Some other findings that were involved was that conditioning does not require explicit memory or the brain regions (Hippocampus) necessary for explicit memory. In other amnesic evidence retrieved involving the Procedural memory is that it is used for learning new skills and those skills can be retained up for up to one year, even though the amnesic patient may have no Episodic memory of doing it before. Repetition priming in these amnesic case studies showed that the patient recognized words faster if presented previously even in the absence of explicit memory (Corkin 2002).

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(Corkin, 2002) found that Henry preserved motor skills in a study conducted by Milner in the early 1960s, Henry acquired the new skill of drawing a figure by looking at its reflection in a mirror. Further evidence for intact motor learning was provided in a study carried out by Corkin (1968). In this study, Henry was tested on three motor learning tasks and demonstrated full motor learning abilities in all of them. Experiments involving repetition priming underscored Henry's ability to acquire implicit (non-conscious) memories, in contrast to his inability to acquire new explicit semantic and episodic memories (Corkin, 2002). These findings provide evidence that memory of skills and repetition priming rely on different neural structures than memories of episodes and facts; whereas procedural memory and repetition priming do not rely on the medial temporal structures removed from Henrys, semantic and episodic memory do (cf. Corkin, 1984). (Smith & Kosslyn, 2007) found that the dissociation of Henry’s implicit and explicit learning abilities along their underlying neural structures has served as an important contribution to our understanding of human memory: Long-term memories are not unitary and can be differentiated as being either declarative or non-declarative.

Another interesting case study was Clive Wearing who was a talented musician, conductor, and singer prior to his illness. Clive was in his 40s when his incident occurred, Clive came home with a headache one day and over the following course of days, Clive’s headache got much worse whilst enduring a lot of pain. Clive started to forget stuff like his kid’s name. had viral encephalitis, which damaged both the left and right temporal lobe and even the frontal lobe. Clive was diagnosed with Anterograde amnesia and Retrograde amnesia. Due to Clive’s condition, his Hippocampus was completely eradicated which lead to his retrograde amnesia. Clive’s Anterograde amnesia only allows him to have a 30-second memory after that Clive cannot recall anything said to him during them 30 seconds. (What have we learned from Clive Wearing, 2018) explained that even though his capacity for explicit memories were damaged, he has a largely intact implicit memory. He can still do motor tasks that he learned prior to the hippocampal damage, for example, sight read piano music and conduct a choir. However, he would likely have no recollection of doing either of those things minutes after completing the task. as his skills have been unaffected by the amnesia it shows that Clive’s procedural memory is still intact. Procedural memory is an implicit memory which makes it able for you to perform tasks unconsciously. Clive is still able to remember his wife Deborah and his kids but has a problem recalling his children’s names. Clive would also get very frustrated if asked about his about past as he has no explanation to give because he cannot remember.

Another study consisted of Phineas Gage who was also one of the most well-known case studies. In 1984 Phineas Gage was working in construction in America, On September 13th Phineas was at work when a giant iron rod went through Gage’s skull entering through his left cheekbone and exiting through his head. Phineas then got up and clocked out off his work and saw his doctor John Harlow. Phineas had lost a vast proportion of his frontal lobe his wound also became infected which lead him to a semi-comatose state. (Case Studies: Phineas Gage 2013) explained that defying the odds Phineas Gage did not die but the injury he sustained to his brain impacted his behavior permanently, although accounts from the time are sometimes conflicting and often unreliable, numerous sources report that Gage’s character altered dramatically after his accident. In 1868 Harlow wrote a report on the ‘mental manifestations’ of Gage’s injuries. He described Gage as “fitful, irreverent, indulging at times in the grossest profanity… capricious and vacillating” and being “radically changed, so decidedly that his friends and acquaintances said he was ‘no longer Gage’.” (Case Studies: Phineas Gage 2013). Phineas died in 1868 from severe epileptic attacks that were caused by his trauma. This case study shows that a person can live without their frontal lobe, but the frontal lobe is more responsible for behavior as it shows that Gage’s character changed dramatically after the incident.

In conclusion, what psychologists and neuroscientists have found from these case studies have been very important for the understanding in both short- and long-term memory. As a result of Henry Molaison's condition, they discovered that the Hippocampus was detrimental for processing new memories as he had problems remembering new information after his incident this also shows that the hippocampus is also essential for converting short-term memory to long-term memory and that it was not necessary for working memory. Another important finding as you can see from Clive Wearing’s case study is that Procedural memory is not affected from Retrograde nor Anterograde amnesia as he was still able to play the piano whilst having no recollection of being able to play or listen to music. Finally, In Phineas Gage’s case study the doctors found that the frontal lobe is not fundamental for living but in fact, researchers found that it is used for regulating and controlling behavior as seen in Phineas Gage, that there were many reports saying that his behavior had gotten worse since his accident involving his cortex.

References

1. Corkin S. 2002. What’s new with the amnesic patient H.M.? Nat Rev Neurosci 3:153–160
2. S. Corkin (1984). 'Lasting consequences of bilateral medial temporal lobectomy: Clinical course and experimental findings in H.M.'. Seminars in Neurology. 4 (02): 249–259.
3. S. Corkin (1968). 'Acquisition of motor skill after bilateral medial temporal-lobe excision. Neuropsychologia. 6 (3): 255–265
4. E. E. Smith; S. M. Kosslyn (2007). Cognitive Psychology: Mind and Brain (1st ed.). Upper Saddle River, NJ: Pearson/Prentice Hall.
5. Case Studies: Phineas Gage, (2013), https://bigpictureeducation.com/brain-case-study-phineas-gage
6. What have we learned from Clive Wearing? , (2018) https://brainstuff.org/blog/memory-clive-wearing