Storing and Retrieving Memories Module 23 Storing and Retrieving Memories Josef F. Steufer/Getty Images

Storing and Retrieving Memories Memory Storage 23-1: WHAT IS THE CAPACITY OF LONG-TERM MEMORY? ARE OUR LONG-TERM MEMORIES PROCESSED AND STORED IN SPECIFIC LOCATIONS? Our capacity for storing long-term memories is essentially limitless. This is contrary to the belief that we can fill more items only if we discard old ones.

Storing and Retrieving Memories Memory Storage Retaining Information in the Brain Information is not stored in single, precise locations in the brain. Memories are brain-based, but the brain distributes the components of a memory across a network of locations in the brain. Some of the brain cells that fired when we experienced something fire again when we recall it. Despite the brain’s vast storage capacity, we do not store information as libraries store their books, in single, precise locations. Instead, brain networks encode, store, and retrieve the information that forms our complex memories.

Storing and Retrieving Memories Memory Storage Retaining Information in the Brain 23-2: WHAT ARE THE ROLES OF THE FRONTAL LOBES AND HIPPOCAMPUS IN MEMORY PROCESSING? We have two conscious memory systems: Semantic memory: Explicit memory of facts and general knowledge Episodic memory: Explicit memory of personally experienced events. The hippocampus is a neural center located in the limbic system; registers and temporarily holds elements of explicit memories before moving them to other brain regions for long-term storage. Neural storage of long-term memories is called memory consolidation.

Explicit-Memory System: The Hippocampus Explicit memories for facts and episodes are processed in the hippocampus (orange structures) and fed to other brain regions for storage. Separate brain regions process explicit and implicit memories During sleep, the hippocampus and brain cortex display rhythmic patterns of activity, as if they were talking to each other (Euston et al., 2007; Mehta, 2007). Researchers suspect that the brain is replaying the day’s experiences as it transfers them to the cortex for long-term storage. THE HIPPOCAMPUS

Storing and Retrieving Memories Memory Storage Retaining Information in the Brain Implicit Memory System: Cerebellum and Basal Ganglia 23-3: WHAT ARE THE ROLES OF THE CEREBELLUM AND BASAL GANGLIA IN MEMORY PROCESSING? The cerebellum plays important role in forming and storing implicit memories created by classical conditioning. The basal ganglia, deep brain structures involved in motor movement, facilitate formation of our procedural memories for skills. Infantile amnesia Conscious memory of first three years is blank. Command of language and well-developed hippocampus needed. Hippocampus is one of the last brain structures to mature.

Storing and Retrieving Memories Memory Storage Retaining Information in the Brain The Amygdala, Emotions, and Memory 23-4: HOW DO EMOTIONS AFFECT OUR MEMORY PROCESSING? Excitement or stress triggers hormone production and provokes the amygdala (two limbic system, emotion-processing clusters) to engage memory. Emotions often persist with or without conscious awareness. Emotional arousal causes an outpouring of stress hormones, which lead to activity in the brain’s memory-forming areas. Flashbulb memories, clear memories of emotionally significant moments or events, occur via emotion-triggered hormonal changes and rehearsal.

Review Key Memory Structures in the Brain Frontal lobes and hippocampus: explicit memory formation Cerebellum and basal ganglia: implicit memory formation Amygdala: emotion-related memory formation

Storing and Retrieving Memories Memory Storage Synaptic Changes 23-5: HOW DO CHANGES AT THE SYNAPSE LEVEL AFFECT OUR MEMORY PROCESSING? Long-term Potentiation (LTP) Increase in a synapse’s firing potential after brief, rapid stimulation After LTP, brain will not erase memories Believed to be a neural basis for learning and memory Kandel and Schwartz (1982) observed synaptic changes during learning in the neurons of the California sea slug, Aplysia. Their research pinpointed changes in sea slugs neural connections; with learning, more serotonin is released and cell efficiency is increased.

Aplysia Aplysia, the California sea slug, which neuroscientist Eric Kandel studied for 45 years, has increased our understanding of the neural basis of learning and memory. After LTP has occurred, an electric current passing through the brain won’t erase old memories. But the same current will wipe out very recent memories.

Doubled receptor sites Electron microscope image (a) shows just one receptor site (gray) reaching toward a sending neuron before long-term potentiation. Image (b) shows that, after LTP, the receptor sites have doubled. This means that the receiving neuron has increased sensitivity for detecting the presence of the neurotransmitter molecules that may be released by the sending neuron. (From Toni et al., 1999.)

Storing and Retrieving Memories Memory Storage Our Two Memory Systems

Storing and Retrieving Memories Memory Retrieval Retrieval Cues 23-6: HOW DO EXTERNAL CUES, INTERNAL EMOTIONS, AND ORDER OF APPEARANCE INFLUENCE MEMORY RETRIEVAL? Memories held in storage by web of associations Retrieval cues serve as anchor points for pathways to memory suspended in this web When you encode into memory the name of the person sitting next to you in class, you associate it with other bits of information about your surroundings, mood, seating position, and so on Best retrieval cues come from associations formed at the time a memory is encoded Priming Activation, often unconsciously, of particular associations in memory

Memory Retrieval Retrieval Cues PRIMING—AWAKENING ASSOCIATIONS After seeing or hearing rabbit, we are later more likely to spell the spoken word hair/hare as h-a-r-e (Bower, 1986). Associations unconsciously activate related associations. This process is called priming.

Storing and Retrieving Memories Memory Retrieval Retrieval Cues Context-dependent memory Involves improved recall of specific information when the context present at encoding and retrieval are the same Cues and contexts specific to a particular memory will be most effective in helping recall

Storing and Retrieving Memories Memory Retrieval Retrieval Cues State-dependent memory Emotions that accompany good or bad events become retrieval cues. Mood-congruent memory: The tendency to recall experiences that are consistent with one’s current good or bad mood. In a bad mood, we may read someone’s look as a glare and feel even worse. IN a good mood, we may encode the same look as interest and feel even better. Passions exaggerate.

Storing and Retrieving Memories Memory Retrieval Retrieval Cues Serial Position Effect Our tendency to recall best the last (recency effect) and first (primacy effect) items in a list.