Memory I PDF

Memory I LG1) What is the di.erence between working-memory and short-term memory? How does it work? Working memory like a subset of short-term memory where we mentally manipulate information Phonological Loop: deals with spoken and written material 1. Phonological Store (inner ear) processes sp...

Memory I LG1) What is the di.erence between working-memory and short-term memory? How does it work? Working memory like a subset of short-term memory where we mentally manipulate information Phonological Loop: deals with spoken and written material 1. Phonological Store (inner ear) processes speech perception and stores spoken words we hear for 1-2 seconds 2. Articulatory control process (inner voice) processes speech production, and rehearses and stores verbal information from the phonological store As long as we keep repeating it, we can retain the information in working memory Visuospatial Sketch ( inner eye): stores and processes information in a visual or spatial form -> used for navigation Executive Control: the boss of working memory manages attention and coordinates phonological loop and visuospatial sketch è Combines information from those two systems while also drawing information from the long-term memory enables the working memory system to selectively attend to some stimuli and ignore others Episodic Bu>er: acts as a “backup” store which communicates with both long-term memory and the components of working memory integrates more complex, multimodal information, resembling short film clips Short-term memory Working memory Lasting time Seconds - minutes About 30 secs (without repetition ) capacity 7 +/- 2 Elements Suggested more limited than short-term function To store information To store and process information system Uniform-system Multi-component-system LG2) What are di.erent memorisation techniques? Chunking: technique to bypass limitation (7 +/- 2 elements) by grouping information into larger, meaningful units example: instead of remembering a whole phone number, categorizing it into pairs of numbers Repetition: fundamental technique where information is reviewd repeatedly to keep it active in short-term memory & promote its transfer to long-term memory phonological loop maintains speech-based information through internal repetition Elaboration: information is linked to existing knowledge structures and embedded in a broader context instead of simply memorizing facts, one attempts to understand them, make connections to other concepts and find example Mnemonic Devices (eselsbrücken): usage of images, rhymes, stories or other associations to make information more memorable Retrieval Practice: involves actively recalling information from memory rather than passively reviewing it  è strengthens memory traces and makes it easier to retireve the information in the future Contextual Cues: hippocampus binds events, time and place contextual cues can improve memory by mimicking the environment or state during learning Sleep: supports memory consolidation critical for memory formation, as information gathered during the day is processed and stored in long-term memory during sleep LG3) What are the neural correlations of retaining information? (Brain activity) The Medial Temporal Lobe: Hippocampus: plays a critical role in forming new declarative memories, i.e., memories we can consciously retrieve and verbalize Studies on patients with amnesia, such as the famous case of patient H.M., have shown that damage to the hippocampus results in severe impairments in forming new declarative memories, while other memory types may remain intact Consolidation: medial temporal lobe is critical for consolidation, the process of transferring new memories from a transient short-term state to more stable long-term storage standard consolidation theory posits that the hippocampus plays a temporary role and that memories are eventually stored in the neocortex. multiple-trace theory suggests that the hippocampus remains involved in retrieving episodic memories even after they have been consolidated rength of synaptic connections between neurons is increased through repeated stimulation. LTP is considered a cellular mechanism underlying learning and memory. NMDA Receptors: NMDA receptors, a type of glutamate receptor, play a critical role in initiating LTP. Synaptic Changes: Long-term memories may require substantial changes in the nervous system that can be directly observed. These include forming new synapses, eliminating old ones, and reorganizing synaptic connections. LG4) Why is the retaining of information limited in time and amount? Short-Term Memory (STM) and Working Memory: Limited Capacity: 7 ± 2 items means that only a finite amount of information can be held in STM at a given time. Decay: Information in STM rapidly decays if it is not actively rehearsed or processed This explains why we often forget information we have just seen or heard shortly afterward Interference: New information can displace older information in STM, leading to interference explains why it can be challenging to remember something when simultaneously confronted with additional information Long-Term Memory (LTM): Consolidation (festigung): Transferring information from STM to LTM is a complex process that requires time and resources Not all information in STM is consolidated and stored in LTM Interference: Interference also occurs in LTM when similar pieces of information compete with one another explains why it can be di]icult to recall specific details when you have had many similar experiences. Synaptic Plasticity: Storing information in LTM relies on synaptic plasticity ( =the ability of synapses to strengthen or weaken in response to experiences) Over time, these changes can diminish or be overwritten by new experiences. Additional Factors: Aging: Cognitive abilities, including memory performance, often decline with age è can be attributed to age-related changes in the brain, such as the loss of neurons and synaptic connections. Emotions: Strong emotions can impact memory formation both positively and negatively è Stress and anxiety can impair memory performance, while positive emotions may enhance consolidation Sleep: During sleep, the brain processes information and stores it in LTM Sleep deprivation can impair memory formation LG5)What is the part of the brain responsible for short-term memory? Not a single part of the brain that is exclusively responsible for short-term memory è But prefrontal cortex plays a central role The prefrontal Cortex: Studies on humans and animals indicate that activity in the prefrontal cortex increases during tasks requiring working memory Studies on humans and animals have shown that lesions in this area impair the working memory Patient H.M., who had his medial temporal lobe removed, retained normal working memory, suggesting that his prefrontal cortex remained intact Studies suggest that phonological working memory tasks primarily activate the left ventrolateral prefrontal cortex, while spatial working memory tasks tend to show bilateral (=two-sided) activation Lesions and Deficits: Lesions in the left supramarginal gyrus (Brodmann Area 40) lead to deficits in phonological working memory damage to the parieto-occipital region of both hemispheres a]ects visuospatial short-term memory. Recent research has identified additional brain regions potentially involved in short-term memory, such as the parietal lobe and the cerebellum LG6) Explain the monkey experiment Cue phase: 1) Cue is presented on the screen at a specific location 2) Monkey observes the position of the cue in his peripheral vision 3) Neural activity spikes briefly in brain areas responsible for processing visual stimulus and encoding its location ( V1 & dorsal stream) (called phasic activtiy) Delay phase 1) The cue disappears & monkey has to maintain the location of the cue in his working memory 2) Sustained (anhaltend) neural activity in brain regions responsible for working memory, such as the prefrontal cortex ( called tonic activity) 3) Activity stays high until stimuli is presented, then working memory doesn´t need to hold onto the location of cue Response phase: 1) Stimuli & arrow appear on the screen, ending the delay phase + fixation point vanishes 2) Neural activity spikes again due to the response of the monkey to the stimuli Memory II LG1) How is long-term memory organized? What are the di.erent types of long-term memory? Organization LTM: Medial Temporal Lobe Memory System: includes the hippocampus, amygdala, and surrounding parahippocampal, entorhinal, and perirhinal cortical areas o Hippocampus: plays a critical role in linking relationships between di>erent types of information, which is essential for episodic memories, such as time, place, and the people involved o Perirhinal cortex: is involved in familiarity-based recognition, while the hippocampus and posterior parahippocampal cortex support source- based recognition (episodic memory) o Studies of amnesic patients like H.M. show that the medial temporal lobe is necessary for forming new long-term memories but not for short-term memory or the formation and retrieval of new procedural long-term memories Neocortex: the brain's outer layer, is where long-term memories are ultimately stored Storage tends to occur in cortical areas where the information was first processed and held in short-term memory è For instance, the visual cortex is critical for visual object recognition Frontal Lobe: is involved in various aspects of memory, including working memory processes, encoding episodic information, and organizing the retrieval of information from long-term memory Parietal Lobe: The parietal lobe also plays a role in encoding and retrieving memories, particularly episodic or context-rich memories  The retrosplenial cortex (RSC) within the parietal lobe appears critical for retrieving contextual information. Types of LTM 1. Declarative Memory § Declarative memory refers to memory for facts and events that we can consciously access and verbalize § It is also called explicit memory § The medial temporal lobe is critical for forming declarative memories. o Semantic Memory: - Memory for facts and general knowledge - Is context-independent, meaning we don't necessarily remember the circumstances under which we learned the information. o Episodic Memory: - Memory for personal experiences and events including details about what happened, where, when, and with whom - always involve the self as the actor or recipient of an action - hippocampus plays a key role in encoding and retrieving episodic memories. 2. Non-Declarative Memory § Non-declarative memory refers to memory for skills, habits, and behaviors that we cannot consciously access or verbalize § also called implicit memory § independent of the medial temporal lobe o Procedural Memory: - Memory for motor and cognitive skills, such as riding a bike or reading - requires extensive and repeated experiences. o Priming:  -refers to a change in response to a stimulus or the ability to identify a stimulus after prior exposure - Types of priming include perceptual, conceptual, and semantic priming. o Classical Conditioning: - A form of associative learning in which a neutral stimulus is paired with an unconditioned stimulus that elicits an unconditioned response - After repeated pairings, the neutral stimulus elicits a conditioned response. o Spatial Memory: - Enables person to remember locations as well as where an object is located in correlation to other objects o Non-Associative Learning: - refers to changes in response to a stimulus after repeated exposure, without associating it with another stimulus - Examples include habituation and sensitization LG2) What does the case of patient HM tell us about the role of the medial temporal lobe (hippocampus) in long-term memory? Insights from the Case of Patient H.M. bilateral removal of most of his temporal lobes to treat his epilepsy è H.M. su]ered from severe anterograde amnesia, meaning he was unable to form new declarative memories related to facts and events that could be consciously recalled and verbalized  retained memories of events from his life before the surgery but struggled to recall any events that occurred afterward able to follow conversations and remember a series of numbers for a short time, but he could not repeat them an hour later His short-term memory function was normal; for instance, he could repeat word lists, indicating that the medial temporal lobe is not necessary for encoding sensory information in short-term memory. Was able to learn new skills, such as mirror drawing, even though he had no memory of practicing or learning the new skill è demonstrates that his non-declarative memory (or procedural memory) for perceptual and motor behaviors was intact insights into the role of the medial temporal lobe in long-term memory: 1. The medial temporal lobe, including the hippocampus, is crucial for forming new declarative memories o H.M.'s inability to learn new facts and events highlights the role of this brain region in consolidating information from short-term memory into long-term memory 2. The medial temporal lobe is not the area where long-term memories get stored o H.M. retained memories of events from his life before the surgery, suggesting that long-term memories are stored elsewhere in the cortex 3. Di]erent types of long-term memory are processed by di]erent brain regions o H.M.'s ability to learn new skills while being unable to recall new facts or events underscores the distinction between declarative and non- declarative memory and their reliance on separate neural systems LG3) What are the di]erent types of forgetting (anterograde vs. retrograde amnesia)? Which brain areas are involved in long-term memory formation / amnesia? Types of Forgetting Amnesia refers to a severe memory impairment typically caused by injury or illness di]erent types of forgetting: o Retrograde Amnesia: Di]iculty recalling memories formed before the onset of amnesia. This often a]ects events that occurred hours, days, or even a year prior to the event that triggered amnesia. o Anterograde Amnesia: The inability to form new memories starting from the onset of a disturbance. Brain Areas Involved in Long-Term Memory Formation and Amnesia Medial Temporal Lobe This brain region, which includes the hippocampus, entorhinal cortex, perirhinal cortex, and parahippocampal cortex, is crucial for forming new declarative memories.  o hippocampus acts as the brain's final hub, combining information from nearby cortical regions, and is especially important for connecting an object with its specific context, like where or when it was encountered o perirhinal cortex is thought to mediate the sense of familiarity with an object in memory o parahippocampal cortex appears to process contextual aspects of memory, including spatial cognition Medial Diencephalon This region, which includes the dorsomedial thalamus and mammillary bodies, also plays a role in long-term memory formation o Damage to this region, as observed in Patient N.A., can also lead to anterograde amnesia, suggesting it works in conjunction with the medial temporal lobe to support memory Other Brain Regions: Various other regions are involved in di]erent forms of non- declarative memory, including: o Basal Ganglia: Involved in skill learning o Cerebellum: Plays a role in classical conditioning o Amygdala: Engaged in emotional processing and conditioning, such as fear o Neocortex: Involved in storing declarative memories and in priming o Prefrontal Cortex: Engaged in working memory processes and encoding information LG4) How are long-term memories formed? What is memory consolidation? How Are Long-Term Memories Formed? 1. Encoding: processing incoming information from sensory channels transferring it into short-term memory Various brain areas contribute to the initial processing of stimuli è but only a few are associated with successful encoding  o For example, encoding visual elements in photos involves stronger activation of the right prefrontal cortex and the parahippocampal cortex in both hemispheres o For words, the critical areas are the left prefrontal cortex and the left parahippocampal cortex 2. Consolidation: memories transition from a temporary and fragile state to a more stable and lasting form è fleeting short-term memory contents are transformed into more durable long- term memories can take days, months, or even years, gradually leading to stronger representation of the memory o The medial temporal lobe, particularly the hippocampus, is critical for consolidating information from short-term to long-term memory o Long-term storage of information tends to occur in cortical regions where the information was initially processed and held in short-term memory 3. Retrieval: The process of searching for a memory and finding it Retrieval from long-term memory is guided by various cognitive processes, including attention o Evidence suggests that retrieval temporarily makes memories plastic again, allowing them to be updated and strengthened before being reconsolidated into a stable state What Is Memory Consolidation? The process of stabilizing a memory over time after initial acquisition It is a critical step in forming long-term memories and involves both cellular and systemic processes Synaptic Consolidation: § refers to structural and functional changes at synapses in response to learning and experience § These changes can include the formation of new synapses, strengthening of existing synapses, and alterations in neurotransmitter release Systems Consolidation: § involves interaction between di]erent brain regions, particularly the hippocampus and neocortex § two main theories about systems consolidation: o Standard Consolidation Theory: suggests that the neocortex is essential for storing fully consolidated long-term memories, while the hippocampus plays only a temporary role o Multiple Trace Theory: suggest that the hippocampus remains involved in retrieving episodic memories, regardless of whether they are consolidated, while semantic information is stored exclusively in the neocortex Factors Influencing Memory Consolidation: Sleep: studies in rats have shown that neurons in the hippocampus repeat activity patterns during sleep that occurred during learning, suggesting that the brain "replays" learned tasks during sleep Stress: Both physical and psychological stress can influence memory consolidation o Acute stress, combined with adrenaline, can enhance the initial encoding and consolidation of information perceived around the time of the stressor o Chronic stress, however, can negatively a>ect memory, possibly by impairing long-term potentiation (LTP) in the hippocampus. LG5) What is long-term potentiation (LTP)? Explain how LTP works. What is the role of calcium in LTP? How is LTP related to neural activity during perception / working memory? What Is Long-Term Potentiation (LTP)? synaptic strength between two neurons increases after repeated, strong stimulation identified through classical experiments (1970s) on the hippocampus of rats, researchers observed that stimulating presynaptic axons with high-frequency bursts (tetanus) led to enhanced responses on postsynaptic neurons è this heightened responsiveness (LTP) can last for weeks or even longer considered one of the key mechanisms behind learning and memory formation How Does LTP Work? Occurs at synapses that use the excitatory neurotransmitter glutamate and is critically dependent on a specific subtype of glutamate receptor (NMDA receptor) 1. Normal Synaptic Transmission: During regular, low-level activity, the release of glutamate at a synapse primarily activates AMPA receptors. NMDA receptors remain unresponsive because their calcium channels (Ca2+) are blocked by magnesium ions (Mg2+) 2. Induction of LTP: When presynaptic neurons are stimulated with a burst of action potentials (tetanus), a large amount of glutamate is released. This strongly activates AMPA receptors, depolarizing the postsynaptic membrane. 3. Removal of Mg2+ Block: If depolarization reaches a threshold, Mg2+ ions are expelled from NMDA receptors, allowing them to respond to glutamate and permit the entry of Ca2+ ions into the postsynaptic neuron. 4. Activation of Protein Kinases: The influx of Ca2+ activates intracellular enzymes called protein kinases, such as CaMKII, which modify or activate other proteins. These changes a]ect AMPA receptors in significant ways. 5. Strengthening of the Synapse: Activated CaMKII promotes the production of more AMPA receptors and their insertion into the postsynaptic membrane. Existing AMPA receptors are also redistributed to the active synapse, and their ion conductivity increases. These adjustments make the synapse more sensitive to released glutamate.  6. Retrograde Signaling: In addition to postsynaptic changes, the activation of NMDA receptors triggers the release of a retrograde messenger from the postsynaptic cell, which travels back to the presynaptic cell and prompts it to release more glutamate, further strengthening the synapse. The Role of Calcium in LTP Calcium (Ca2+) plays a critical role in the induction of LTP The influx of Ca2+ through NMDA receptors serves as the key signal triggering the downstream cascade that strengthens the synapse: Ca2+ as an Intracellular Messenger: Ca2+ acts as a signal indicating high synaptic activity Activation of Protein Kinases: Increased Ca2+ levels activate protein kinases like CaMKII, which phosphorylate AMPA receptors and enhance their functionality Long-Term Changes: Calcium-mediated processes lead to the insertion of additional AMPA receptors and increased glutamate release, making the synapse stronger and more e]icient LTP and Neural Activity During Perception and Working Memory Perception: - LTP may underlie the neural circuits involved in processing and storing sensory information ð Strengthening synapses in sensory cortices (=areas in the brain that process sensory information) in response to repeated  stimuli could improve perception and recognition of these stimuli Working Memory: - involves the temporary storage and manipulation of information over seconds to minutes - LTP may help sustain (erhalten) neural activity in prefrontal cortical circuits involved in working memory tasks ð Strengthening synapses in these circuits may aid in keeping information accessible for processing