최근 기억력 저하의 원인, 기억의 유형 : 작업기억(Working Memory/Short-term Memory)

 

나이가 들거나 치매와 같은 질환이 생기면 기억 유지 및 회상 패턴이 종종 상당한 변화를 겪습니다. 이러한 과정의 두드러진 특징 중 하나는 새로운 기억을 형성하는 능력이 저하되는 동안 오래된 기억은 보존된다는 것입니다. 이 현상은 다양한 신경생물학적 및 인지적 메커니즘을 통해 설명할 수 있습니다.

최근 기억의 저하 :기억력 저하의 원인

◈기억의 유형

1. 에피소드 기억: 

이것은 과거의 특정 사건이나 경험을 회상하는 능력입니다.  구조화된 서사와 맥락에 굳건히 자리 잡은 오래된 기억은 장기 기억에 보관됩니다.

2. 작업 기억/단기 기억: 

이것은 단시간(초에서 분) 동안 정보를 보관하고 조작하는 능력을 포함합니다. 장기 저장소로 전환되기 전에 정보를 처리하고 인코딩하여 새로운 기억을 형성하는 데 중요한 역할을 합니다.

◈신경해부학적 고려 사항

1. 해마: 

해마는 새로운 에피소드 기억을 형성하는 데 중요합니다. 특히 알츠하이머병에서 볼 수 있는 위축과 같은 연령 관련 변화와 신경 퇴행성 과정에 취약합니다. 해마가 악화됨에 따라 새로운 기억을 인코딩하는 능력이 감소하여 최근 기억을 형성하는 데 어려움이 발생합니다.

2. 피질: 

오래된 기억은 종종 피질의 다양한 부분, 특히 기억과 관련된 감정적 의미와 맥락적 세부 사항을 반영하는 영역에서 통합됩니다. 이러한 기억은 시간이 지남에 따라 반복적인 검색 및 강화로 인해 더욱 강력해집니다.

◈인지 메커니즘

1. 기억 통합: 

초기 형성 후 기억 흔적을 안정화하는 통합 과정은 시간이 지남에 따라 발생합니다. 장기 기억으로 통합된 기억은 일반적으로 노화 또는 신경 퇴행성 과정으로 인해 방해를 덜 받습니다.

2. 신경 전달 시스템: 

노화 및 신경 퇴행성 질환은 신경 전달 시스템, 특히 학습과 기억에 중요한 아세틸콜린과 관련된 신경 전달 시스템을 손상시킬 수 있습니다. 이는 새로운 기억의 통합에 불균형적으로 영향을 미치는 반면, 더 오래되고 확립된 기억은 그대로 유지됩니다.

3. 간섭: 

작업 기억의 용량은 나이가 들면서 감소하는 경향이 있습니다. 많은 새로운 정보의 간섭은 최근 기억의 저장을 방해할 수 있으며, 특히 인지적 부하가 높을 때 그렇습니다.

4. 맥락적 단서: 

오래된 기억은 종종 시간이 지나도 뚜렷하게 남는 맥락적 단서의 도움으로 회상됩니다. 반면, 최근 기억은 잊혀지기 전에 효과적으로 맥락화될 기회가 없었을 수 있습니다.

◈치매와 기억 장애

1. 알츠하이머병: 

알츠하이머병에서는 기억 장애의 명확한 패턴이 있습니다. 환자는 종종 최근 사건에 어려움을 겪으면서도 먼 과거의 기억을 회상하는 능력을 유지합니다. 이는 주로 새로운 기억의 형성에 영향을 미치는 해마 손상 때문입니다.

2. 전두측두형 치매: 

이 유형에서는 기억 상실보다 일찍 성격 변화가 발생할 수 있습니다. 오래된 기억을 유지하는 것은 새로운 기억을 습득하는 데 필요한 영역보다 손상된 영역의 관여가 적기 때문일 수 있습니다.

3. 혈관성 치매: 

혈관 관련 기억 장애의 경우 혈류가 중단되면 기억과 관련된 영역을 포함한 뇌의 특정 영역이 손상되어 최근 기억을 상실하는 반면 오래된 기억은 그대로 유지될 수 있습니다.

◈마무리

신경 해부학적 무결성, 인지 처리 능력, 기억 인코딩 및 검색 메커니즘의 상호 작용은 노화 또는 치매에도 불구하고 오래된 기억은 종종 접근 가능한 반면 새로운 기억은 점점 더 애매해지는 이유를 설명합니다. 이러한 불일치는 기억의 복잡한 본질을 강조하고 노화에 따른 인지 저하의 치료 및 관리에 대한 통찰력을 제공합니다. 인지 기능을 향상시키는 것을 목표로 하는 치료적 개입은 장기 기억을 보호하는 통합 프로세스를 강화하는 동시에 해마 및 기타 관련 구조의 기능을 보존하는 데 중점을 둘 수 있습니다.

 

As we age or develop conditions such as dementia, the patterns of memory retention and recall often undergo significant changes. One of the striking features of these processes is the preservation of older memories while the ability to form new memories deteriorates. This phenomenon can be explained through various neurobiological and cognitive mechanisms.


Types of Memory  

1. Episodic Memory: This is the ability to recall specific events or experiences from the past. Older memories, often cemented in structured narratives and contexts, are held in our long-term memory.

2. Working Memory/Short-term Memory: This involves the ability to hold and manipulate information for short durations (seconds to minutes). It plays a crucial role in forming new memories by processing and encoding information before it transitions into long-term storage.


Neuroanatomical Considerations  

1. Hippocampus: The hippocampus is critical for the formation of new episodic memories. It is particularly vulnerable to age-related changes and neurodegenerative processes, such as atrophy seen in Alzheimer’s disease. As the hippocampus deteriorates, its ability to encode new memories diminishes, leading to difficulties in forming recent memories.

2. Cortex: Older memories are often consolidated in various parts of the cortex, especially areas that reflect the emotional significance and contextual details associated with the memories. These memories become more robust due to repeated retrieval and reinforcement over time.


Cognitive Mechanisms  

1. Memory Consolidation: The process of consolidation, which involves the stabilization of memory traces after initial formation, occurs over time. Memories that have been consolidated into long-term memory are typically less susceptible to disruption by aging or neurodegenerative processes.

2. Neurotransmitter Systems: Aging and neurodegenerative diseases can impair neurotransmitter systems, particularly those involving acetylcholine, which is critical for learning and memory. This can disproportionately affect the consolidation of new memories while older, more established memories remain intact.

3. Interference: The capacity of working memory tends to decline with age. The interference from many new incoming pieces of information can hinder the storage of recent memories, particularly when there is a high cognitive load.

4. Contextual Cues: Older memories are often recalled with the assistance of contextual cues that remain salient despite the passage of time. In contrast, recent memories may not have had the chance to be contextualized effectively before they are forgotten.


Dementia and Memory Impairment  

1. Alzheimer’s Disease: In Alzheimer's, there is a clear pattern of memory impairment. Patients often retain their ability to recall memories from their distant past while struggling with recent events, primarily due to the hippocampal damage that impacts the formation of new memories.

2. Frontotemporal Dementia: In this type, personality changes may occur earlier than memory loss. The retention of older memories can be attributed to less involvement of the impaired regions compared to those required for the acquisition of new memories.

3. Vascular Dementia: In vascular-related memory disorders, interruptions in blood flow can cause specific areas of the brain, including those associated with memory, to become damaged, leading to recent memory loss while older memories may remain intact.


Conclusion  

The interplay of neuroanatomical integrity, cognitive processing abilities, and the mechanisms of memory encoding and retrieval explains why older memories often remain accessible even in the face of aging or dementia, while new memories become increasingly elusive. This discrepancy highlights the complex nature of memory and offers insight into the treatment and management of cognitive decline as we age. Therapeutic interventions that aim to enhance cognitive function may focus on preserving the functioning of the hippocampus and other related structures while reinforcing the consolidation processes that safeguard long-term memories.