psych unit 3

• Memory


  The processing, storage and retrieval of information acquired through learning

  
• Memory


  A representation of a past experience

  
• Memory processes


  1. Encoding

  2. Storage

  3. Retrieval
• Atkinson-Shiffrin multi-store model of memory


  • Consists of three different stores/components: sensory memory, short-term memory, long-term memory
  • Each store processes information in different ways
  • The components differ in function, capacity and duration
  • Operate simultaneously and interact

  
• Sensory memory


  Entry point that stores all incoming sensory information (unlimited capacity) for a short amount of time (brief duration)
• Iconic memory


  Visual images are stored here for about a third (0.3) of a second
• Echoic memory


  Sound stimuli are stored here for around 3-4 seconds
• Short-term memory


  • Info is only transferred from sensory memory once it is paid attention to
  • Has a limited capacity and duration (unless renewed through rehearsal)
  • Info is encoded, no longer in its original form

  
• Short-term memory duration


  Recall starts to decline after about 12 seconds and is almost completely gone after 18 seconds (can last up to 30 secs)
• Short-term memory capacity


  • Limited capacity of 7 ± 2 bits of information
  • Can be increased by chunking - grouping individual items together

  
• Working memory


  Temporarily holds and manipulates ("works on") information from sensory memory and retrieved from long-term memory
• Long-term memory


  • Stores a potentially unlimited amount of information for a very long time
  • Not a single store for all kinds of info - different types are linked to different types of information, memory processes, and neural mechanisms
• Types of long-term memory


  • Explicit memory
  • Implicit memory
  • Classically conditioned memory
  • Procedural memory
  • Semantic memory
  • Episodic memory
• Explicit memory


  Memory that occurs when information can be consciously (intentionally) retrieved and stated
• Implicit memory


  Memory that does not require conscious (intentional) retrieval - the existence of a specific memory is inferred through actions

  
• Episodic memory


  The long-term memory of personally experienced events associated with a particular time and place

  
• Semantic memory


  The long-term memory of facts and knowledge about the world

  
• Procedural memory


  Memory of motor skills and actions - demonstrated through performance with no conscious attempt to retrieve them

  
• Classical conditioned memory


  A conditioned response (of fear or anxiety) to a conditioned stimulus acquired through classical conditioning

  
• Explanatory power


  The ability of a theory/model to explain subject matter effectively
• Hippocampus


  • Plays a role in the formation and encoding of explicit memories
  • Ensures memories are consolidated and long-lasting
  • Involved in spatial memories - the explicit memory for the physical location of objects in space
• Amygdala


  • Processes and regulates emotional reactions
  • Involved in the formation and consolidation of emotional memories, including implicit classically conditioned fear responses
• Neocortex


  • Interacts with the hippocampus to store explicit long-term memories
  • Permanent storage tends to be in the areas where the relevant information was first processed
  • The different components of a memory are linked via neural networks and reconstructed during retrieval
• Basal ganglia

  • Involved in the formation and encoding of implicit procedural memories - specifically habits and initiations and suppression of unwanted movements
• Cerebellum


  • Involved in the encoding and temporary storage of implicit procedural memories
  • Also forms and stores implicit memories of simple reflexes acquired through classical conditioning
• Autobiographical events contain both episodic and semantic memories
• To retrieve an autobiographical event we have to engage in 'mental time travel' and place ourselves in the context of the event
• Possible imagined futures draw on elements of past experiences from semantic and episodic memory
• Patients with hippocampal damage experienced difficulty remembering past events and imagining future scenarios
• Alzheimer's disease results in declining cognitive functions including memory loss, starting with short-term memory loss due to cortical damage
• Rationality


  Mentally 'trying out' different scenarios can guide our future behaviours (e.g. possible consequences)
• Patients who sustained damage to their hippocampus not only experienced difficulty remembering past events, but also struggled to imagine future scenarios
• Alzheimer's disease


  A neurodegenerative disease characterised by gradual widespread neuron death causing brain tissue to shrink
• Alzheimer's disease


  • Results in declining cognitive functions (inc. memory loss), social skills and personality changes
  • STM loss is first (due to cortical damage) then LTM becomes impaired (especially for explicit memories as the disease damages the medial temporal lobe)
  • Most common form of dementia (50-75% of cases)
  • Biggest risk factor is age (is not part of the normal aging process)
• Lesions


  Area of tissue that has been damaged due to disease or injury
• Lesions are predominantly identified in the hippocampus
• Lesions in Alzheimer's disease


  • Amyloid plaques: fragments of the protein beta-amyloid that accumulate into insoluble clumps
  • Neurofibrillary tangles: an accumulation of the protein tau that forms insoluble twisted strands within neurons
• Amyloid plaques inhibit communication between neurons
• Neurofibrillary tangles inhibit the transportation of essential substances within the neuron and eventually lead to cell death
• Comparison of an MRI of a healthy brain and the brain of someone with Alzheimer's disease


  • Note how the scan of the Alzheimer's brain shows more blank space, which indicates a loss of brain mass