Memory and the Brain

Sensory Memory

  • Information is gathered through five senses: touch, sight, taste, smell, and hearing.
  • We remember information by how it feels, looks, tastes, smells, or sounds.
  • Details registered by the senses determine what is remembered.
  • The more senses and emotion involved, the stronger the memory.

Short Term Memory

  • Also called primary or active memory.
  • Involves current thoughts or focus.
  • Information is easily forgotten if not repeated or actively used.
  • Temporarily stores information for everyday activities.
  • Details are forgotten once the activity concludes and focus shifts.
  • Duration is brief; data decays in seconds.
  • Storage capacity is limited.

George Miller's Experiment

  • Conducted an experiment in the 1950s to measure how much unfamiliar information the human brain could absorb.
  • Subjects repeated random lists of words, colors, tastes, numbers, and letters.
  • People could store between 5 and 9 items, averaging around 7.
  • Coined the term "magic number seven".
  • Analogy: Remembering grocery items without a list. You may easily remember three to four items, but if you need seven or more items, you are more likely to forget something.

Short Term Memory vs. Working Memory

  • Some experts use these terms interchangeably, but they are technically different.
  • Short term memory: temporary storage of new information.
  • Working memory: includes organizing and manipulating information.
  • Working memory manages information for complex cognitive tasks like learning, reasoning, and comprehension, and is the bridge between short term and long term memory.

Long Term Memory

  • Information stored in the brain that is retrievable over a long period.
  • Memories are deeply encoded or embedded, either by repetition or strong connection to emotions and senses.
  • Requires focus and/or rehearsal for working memories to become long term memories.

Categories of Long Term Memory

  • Explicit (declarative) memory: knowing "what"; conscious memory.
    • Includes facts, events, concepts, life experiences, and general knowledge.
    • Can be recalled or declared from storage.
    • Shaped by context and emotion.
  • Implicit (procedural) memory: knowing "how"; unconscious memory.
    • Includes skills such as riding a bike, playing an instrument, or speaking a language.
    • Becomes routine and automatic.

Memory Processes

Four Processes:

  • Encoding
  • Consolidation
  • Storage
  • Retrieval

Encoding

  • First process used to create a new memory.
  • Sensory information is changed into synapses.
  • Synapse: structural connection between two neurons, allowing chemical or electrical signals to pass.
  • Messages from different senses are sent to different brain parts.
  • The hippocampus processes and decodes information into a single experience.
  • The hippocampus acts as a sorting center where sensory perceptions are analyzed, compared, and associated with previous messages.
  • The sorting process determines what becomes short term vs. long term memory.
Types of Encoding
  • Acoustic: encoding by sound or auditory information (phonological loop/echoic memory).
    • Repeating information aids memorization.
  • Visual: encoding by images or visual information (iconic memory).
    • Fragmented or blurred images associated with memory.
  • Tactile: encoding through the sense of touch (vibrotactile memory).
  • Semantic: encoding sensory input associated with meaning or context.
  • Short term memory relies on acoustic encoding, while long term memory relies on semantic encoding.

Consolidation

  • Strengthens a memory trace by reinforcing synapses each time they are used.
  • Considered part of encoding or storage.
  • Long term potentiation: neurons firing together become permanently sensitive to each other.
  • Brain creates new synapses, reroutes old connections, or rearranges its organization in response to new information.
  • Synaptic plasticity/neuroplasticity: ability for synapses to change, foundational to memory and learning.

Memory Storage

  • Retaining information.
  • Can be temporary (sensory, short term, working memory) or permanent (long term memory).
  • Memories are sent to the cerebral cortex after encoding and consolidation.
  • Cerebral cortex: outermost grooved surface of gray matter of the brain.
  • Long term memories particularly are stored throughout the cortex.
  • Memory storage is a cross referencing system that activates associations in multiple brain parts.

Memory Retrieval

  • Ability to reaccess or remember encoded and stored information.
  • A single memory is recorded and retrieved through the same basic pattern.
  • Recalling a memory refires the same neural connections made during the original experience.
  • Memories are not static; new information can alter previous memories over time.
  • Memories can be reshaped by awareness or decline with age.
Methods for Retrieving Memories
  • Recognition: unconscious method requiring one process, making a decision based on familiarity.
    • Involves association and comparison of previously experienced information.
    • Used for true/false, matching, or multiple choice questions.
  • Recall: conscious retrieval requiring a two step process.
    • Searching and retrieving information from memory, then deciding based on familiarity.
    • Used for essay exams or debates.
Types of Memory Recall
  • Free recall: recalling information in any order.
  • Serial recall: recalling information in a specific order.
  • Cued recall: recalling information when stimulated by prompts or associations.
Memory Techniques
  • Designed to retrieve information based on cued recall, using prompts and associations.
  • Information we do not need at the present seems to go away. Human memory is more like a computer system with thousands of files organized in folders within folders. Just because a file cannot be found does not mean it is not there.
  • Need for structured system to mentally catalog what we need to remember.

Key Terms

  • Synapses: Neurological connections that form in the brain that allow a chemical or electrical signal to be passed from one neuron to another during the formation of memory.
  • Hippocampus: Central sorting center in the brain involved in the complex processes of forming, organizing, and storing memories, plays an important role in the consolidation of information into long term memories.
  • Cerebral Cortex: Outermost portion of the brain that is a large grooved surface of gray matter where encoded and consolidated memories are stored.