HU Neuropsychology exam 7 (PSYC023)

H.M was described as having partial loss of memory (retrograde amnesia) for the 3 years leading up to his surgery with early memories "seemingly normal", there did not appear to have been any change in his capacity to recall remote events antedating his operation, and he produced well formed autobiographical (fact memory) memories from age 16 years or younger, meaning that H.M's remote memory impairment now extended back to how many years before his surgery?

11 years

A key insight about the organization of memory, and medial temporal lobe function, came with what?

A consideration of H.M's capacity to remember information that he had acquired before his surgery. H.M was severely impaired at recognizing faces from his post morbid period (1950s and 1960s), but he performed well as or better than age matched controls at recognizing faces of persons who were in the news before his surgery. This finding implied that the medial temporal lobe is not the ultimate storage site for previously acquired knowledge.

H.M's memory impairment has generally been taken as reflecting what?

A failure to convert transient, intermediate memory into stable long-term memory.

superior autobiographical memory

A new kind of memory that is completely new to science and is present in Individuals with the ability to remember every detail of their lives. Type of episodic memory (personal experience), compared to semantic memory (facts). Louise Owen, Jill Price, Brad Williams, Rick Baron, Bob Petrella, and Marilu Henner are all individuals who exhibit this kind of memory.

Clive wearing and the model of memory

Clive has semantic memory (facts) as well as non declarative memory (procedural memory; skills), but lacks...

According to Declarative and procedural Cohen and Squire, 1980

Declarative memory is what is meant when the term memory is used in everyday language; conscious knowledge of facts and events. Is dependent on the medial temporal lobe. Non-declarative memory refers to additional memory systems including systems supporting skill, learning, habit learning, simple conditioning, emotional learning, priming and perceptual learning. Structures with special importance for these kinds of memory include the basal ganglia, the cerebellum, the amygdala, and the neocortex. Procedural memory (non-declarative memory) refers to skill-based knowledge that develops gradually with little ability to report what is being learned.

What type of memory was impaired in H.M?

Declarative memory. Non-declarative memories were still present in H.M. After the surgery, there were long-term memories that were still accessible to H.M. He was able to acquire and retrieve some information.

Findings from H.M.

Established that memory is a distinct cerebral function, separable from other perceptual and cognitive abilities, and identified the medial aspect of the temporal lobe as important for memory.

It's predicted that remote memories could have been intact in H.M's early years after surgery, but then have what?

Faded with time because they could not be strengthened through rehearsal and relearning.

An example of H.M's short term memory:

H.M was shown a 5-pointed star, with a double counter, and was asked to trace its outline with a pencil, but in a condition when he could only see his hand and the star as a reflected in a mirror. He acquired this mirror-drawing skill during 10 trials and exhibited excellent retention across 3 days. However, at the end of testing, he had no recollection of having done the task before.

H.M.

H.M. was knocked down by a bicycle at age 9, resulting in minor seizures at age 10, and major seizures after age 16. At age 27 he became very incapacitated by his seizures despite high doses of anticonvulsant medication (can alter cognitive abilities), that he couldn't work or lead a normal life. Scoville offered H.M. an experimental procedure.

Differences and similarities between Clive Wearing and H.M

In Clive, there was no testing of his memory abilities, so it is speculated that he did not have procedural memory. There was no vividness in his memory, being that he was unable to recall past events. In H.M, there was procedural memory. Long-term memories of new events may not have been able to form in H.M. He was able to recall past events . Both had anterior grade amnesia.

Memory loss can sometimes extend back for decades in the case of what?

Large medial temporal lobe lesions (though additional damage to anterolateral temporal cortex may be important in H.M's circumstances). Memories from early life appear to be intact unless damage extends well into the lateral temporal lobe or the frontal lobe. Eventually, memory can be supported by the neocortex and becomes independent of the medial temporal lobe.

Clive Wearing

Man with 30 second memory due to his sudden and irreversible loss of memory caused by a cold sore virus called encephalitis. The virus traveled to his brain and created holes/dark spots in the temporal lobe and subcortical structures (hippocampus). He does not have any relocation of things. He knows of his illness, and journals every time he wakes up, but feels as though his wakes up for the first time every time. He only remembers his wife Deborah and their love.

Before H.M.

Memory functions were thought to be widely distributed in the cortex and to be integrated with intellectual and perceptual functions (originated with brain researcher Karl Lashley).

H.M had a remarkable capacity for sustained attention, including the ability to retain information for a period of time after it was presented. He exhibited an intact digit span. Information remained available so long as it could be actively maintained by rehearsal. However,

When his attention was diverted to a new topic, he forgot the whole event.

Did H.M perform better over a 3 day period in the experiment with the 5-pointed star?

Yes, but he was not aware of the changes occurring. There was a constant improvement in performance, and some learning was taking place (non declarative memory skills).

What is now clear about H.M's memory impairment and learning?

That his memory impairment was not absolute and he was able to acquire significant new knowledge.

From H.M's experiment with the 5-pointed star, what became appreciated of motor skills?

That motor skills are a subset of a larger domain of skill-like abilities, all of which are preserved in amnesia.

The experiment with H.M and the 5-pointed star was the first hint of what?

That there was more than one kind of memory in the brain. It suggested that some kinds of memory (motor skills) must lie outside of the province of the medial temporal lobe.

What were the differences in H.M's MRI scans from 2002-2003 and 1992-1993?

The 2002-2003 MRI scans documented a number of changes since his first 1992-1993 MRI scans, including cortical thinning, subcortical atrophy, large amounts of abnormal white matter, and subcortical infarcts.