Neuroscience and Amnesia Study Notes

Neuroscience and Amnesia

Condition: Suffered from epilepsy
Treatments:
- Seizure localization
- Use of drugs
- Surgical intervention (medial temporal lobotomy) performed by William Beecher Scoville in 1953
EEG: Electroencephalogram utilized to determine the focus of seizures

Psychosurgery:
- Concept of treating psychiatric illnesses via destruction of brain tissue
Frontal Lobotomy:
- Disconnection of frontal lobes from the rest of the brain
- Practiced from 1930 – 40 until late 1950s; now discredited and banned
Medial Temporal Lobotomy:
- Involved the removal of a considerable amount of brain tissue to treat epilepsy
- Importance of the hippocampus in the sense of smell and emotion
- Outcome for H. M.: Surgery did alleviate epilepsy but resulted in severe memory impairments

IQ was not significantly affected:
- Pre-Surgery IQ: 112
- Post-Surgery IQ: 104
No personality impairment noted
Measured with standardized Wechsler Memory Scale, where he showed below-average performance in story recall

Drastic Loss of Recent Memory:
- Unable to recognize hospital staff or recall day-to-day events
- Unaware of his uncle's death three years prior
- Early memories remain vivid and intact
Corkin's Interview with H. M.:
- Example dialogues highlighting his memory deficits

Corkin et al. (1997): Utilized structural MRI
Findings:
- Damage less extensive than initially thought (5 cm instead of 8 cm)
- Affected areas:
- Bilateral temporal pole, bilateral hippocampus (except for posterior portion), and cortices including entorhinal, perirhinal, and parahippocampal
- Damage to bilateral amygdala

Definition: Loss of memory, typically due to lesions or surgical removal of brain areas
Classifications of Amnesia:
- Causes: Illness, injury, surgery, drugs, psychological factors
- Types:
- Source-based classifications (e.g., illness, injury)
- Location-focused classifications (e.g., area of brain damage)
- Functional classifications (e.g., types of memory impaired)
Common Causes:
- Korsakoff’s syndrome (nutritional deficiency), traumatic brain injury (TBI), electroconvulsive therapy, illnesses (dementia, encephalitis, epilepsy), psychological trauma

Organic Causes of Amnesia:
- Medial Temporal Lobe Amnesia:
- Damage to hippocampus and surrounding regions
- Diencephalic Amnesia:
- Damage to thalamus and mammillary bodies
- Other regions (occipital cortex, frontal cortex) can also cause selective amnesia

Evidence suggests different brain lesions affect varying memory types, indicating multiple "memory systems" exist in the brain
Anterograde Amnesia:
- Inability to form new memories post-injury
  -Commonly associated with damage to hippocampus and diencephalon (thalamus)
Retrograde Amnesia:
- Loss of episodic memories formed prior to the injury
- Related to hippocampal damage, potentially involving other brain areas

Observation: More recent memories are typically more affected than older memories
Principle: The concept of "Last In, First Out" concerning memory retrieval and consolidation

Tested retrograde memory through recall of major news events from 1955 to 2002
Events chosen could be verified for accuracy
Findings: Patients with hippocampal lesions showed greater impairment with more recent news events

Definition: Condition typically resulting from thiamine deficiency, often linked to chronic alcoholism
Symptoms: Damage to thalamus and mammillary bodies leading to memory issues

Background: University Professor diagnosed with alcohol-related Korsakoff syndrome at age 65
Memory Tests: Analyzed using paired associate tasks and semantic memory tests (identity of famous individuals)
Performance: Notable impairment in recalling recent personal information as opposed to older memories

Background: Kent Cochrane, suffered amnesia due to a motorcycle accident at age 30
Brain Damage: Extensive injury to medial temporal lobes with complete bilateral hippocampal loss

Methodology: Photograph description tasks used to assess memory
Outcome: K.C. could not recall specific events even when retrieval cues were present; demonstrated recognition but no temporal gradient in retrograde amnesia

Comparison of Memory Performance:
- H.M. demonstrated normal performance for older news events, but impairments for recent memories indicated temporal gradient effects
- H.M. retained some political knowledge despite anterograde amnesia, aiding familiarity-based retrieval

Example of Beth, Jon, and Kate: Children affected by hippocampal damage from early childhood resulting in impaired episodic memory
Semantic Knowledge Acquisition: Despite difficulties, they managed to acquire semantic knowledge although at a slower pace than typical individuals

Declarative Memory Types:
- Episodic Memory: Personal autobiographical memories
- Semantic Memory: General knowledge or information
- Supported by medial temporal lobe and connections to diencephalon and cortical areas
Amnesia Types: Both retrograde and anterograde forms discussed, with specific focus on Korsakoff’s syndrome and medial temporal lobe-based amnesia

Definition: A form of frontotemporal dementia typically resulting from progressive damage to the anterior temporal lobe
Symptoms: Severe semantic memory loss, while episodic memory may remain relatively intact

Case Study: Patient E.L. diagnosed with semantic dementia
Assessment Tools: Evaluated ability to name familiar individuals from photos and described events surrounding those photographs
Results: Severely impaired in identifying people, while retaining recognition of event details from before diagnosis

Findings in Research:
- Patient K.C. demonstrated episodic memory impairment but intact semantic memory despite hippocampal damage
- Patient with anterior temporal lobe damage (semantic dementia) showed the opposite pattern, with impaired semantic memory but intact episodic memory
Conclusion: These observations suggest that distinct memory systems are supported by separable brain structures for episodic and semantic memory retrieval.