What is the definition and types of memory?

Memory: Definition and Types

Memory is the capacity to acquire, process, store, and retrieve information through neurochemical processes that involve encoding, retention, and consolidation across multiple neural networks. 1

Core Definition

Memory represents a fundamental cognitive ability that enables organisms to encode experiences, retain information over time, and retrieve stored content when needed. 2 This process is not a literal reproduction of past events but rather an amalgam of dynamic constructive and reconstructive processes that are prone to errors, distortions, and modifications. 3

Key Characteristics of Memory

• Memory does not operate like a video recording - it involves selective encoding where limited perceptual information is "patched together to form memories with varying degrees of accuracy." 3
• Encoding is influenced by present knowledge, beliefs, and previous experiences, meaning current mental schemas intrude on how new information is stored. 3
• Reconsolidation irretrievably changes memories - each time a memory is recalled, it undergoes reconstruction and re-encoding, such that the original memory no longer exists and is replaced by a modified version. 3, 4

Major Types of Memory

Based on Temporal Duration

Short-term memory provides temporary storage of limited information for immediate use, typically lasting seconds to minutes. 1

Long-term memory involves more permanent storage of information that can persist for extended periods, from hours to a lifetime. 1, 2

Based on Consciousness of Remembering

Implicit memory operates without conscious awareness of the remembering process. 1

Explicit memory involves conscious, intentional recollection of information. 1

Based on Content Type

Declarative memory (knowing that) encompasses factual information and events that can be consciously recalled. 1

Procedural memory (knowing how) involves skills and habits that are performed without conscious awareness of the underlying knowledge. 1

Based on Functional Domains

Sensory memory includes modality-specific storage:

• Echoic (auditory)
• Iconic (visual)
• Haptic (tactile) 1

Semantic memory stores general knowledge and facts about the world. 1

Episodic memory retains personally experienced events with temporal and spatial context. 1

Working Memory System

Working memory is a brain system providing temporary storage and manipulation of information necessary for complex cognitive tasks such as language comprehension, learning, and reasoning. 5 This system consists of three subcomponents:

• Central executive: An attentional-controlling system that coordinates information processing and is particularly vulnerable in conditions like Alzheimer's disease. 5
• Visuospatial sketch pad: Manipulates and stores visual images and spatial information. 3, 5
• Phonological loop: Stores and rehearses speech-based information, essential for language acquisition. 5

Clinical Memory Disorders

Anterograde Amnesia

Impaired ability to store and retrieve memories subsequent to brain damage onset, affecting the formation of new memories. 3

Retrograde Amnesia

Impaired ability to retrieve memories stored before brain damage onset, affecting access to previously formed memories. 3

Critical Clinical Considerations

Memory is subject to multiple unintentional "sins" including distortions, misattribution, suggestibility, forgetting, falsehoods, and omissions. 3 These limitations have profound implications:

• False memories can be readily induced through techniques like semantic association, where presentation of related words leads to false recall of non-presented items in >75% of cases. 3
• Repeated recall sessions may inadvertently reinforce false memories through reconsolidation processes, making the original memory increasingly inaccessible. 3, 4
• Confidence in memory accuracy does not correlate with actual accuracy - individuals often express high confidence in falsified memories. 4

Common Pitfalls in Clinical Assessment

Clinicians must recognize that human memory is not a valid instrument for generating precise scientific data about past events. 3 When assessing patient recall:

• Avoid multiple interview sessions with identical questions, as this reinforces memory distortion through reconsolidation. 4
• Minimize suggestive questioning, guided imagery, or techniques that encourage elaboration, as these induce false memories. 4
• Recognize that commonplace events (like daily activities) are particularly susceptible to schema-based reconstruction rather than accurate recall. 3