Psych 8

• Plasticity in the Brain

  • Brains change as we develop (biological factors) and as we encounter things in our environments (environmental factors)
  • Neuroplasticity: potential for physical or chemical change
  • Enhances our nervous system's adaptability
• Learning


  • Enduring change in an organism's behaviour as a result of experience
  • Need to be able to observe changes to conclude learning has taken place
• Memory


  • Ability to recall or recognize previous experience
  • Mental representation of a previous experience
  • Engram (memory trace): physical change in the brain connected to that mental representation

  
• Challenges in Studying Learning


  • How do we define behaviour?
  • Observing leaning can be complicated
  • Learning can include making a response or not making a response
  • Learning creates a change in behaviour, but behaviour can change for other reasons, too!
• What isn't Learning


  • Changes in bodily state
  • Change in environment
  • Fatigue
  • Maturation
• How Can We Study Learning

  • Experimentation (usually in the lab)
  • Allows for control of the environmental stimuli
  • Compare behaviour between two groups (usually experimental group and control group)

  
• Why Have Complicated Experiments
• Conditioning


  • Learning
  • Conditioned = learned
• Association


  Learned link between things
• Acquisition


  • Process of learning an association
  • Acquiring a link between things
• Pavlovian Conditioning


  • Respondent conditioning, classical conditioning
  • Unlearned behaviours become associated with previously neutral stimuli
  • Learning relationships between events allows us to predict the occurrence of an event
• Pavlovian Conditioning Terms


  • Unconditioned Stimulus (US)
  • Unconditioned Response (UR)
  • Neutral Stimulus (NS)
  • Conditioned Stimulus (CS)
  • Conditioned Response (CR)
• Pavlovian Conditioning


  1. Before conditioning: Neutral stimulus (NS) produces no response, Unconditioned stimulus (US) produces the unconditioned response (UR)

  2. During conditioning: Neutral stimulus (NS) paired with the unconditioned stimulus (US)

  3. After conditioning: Neutral stimulus (NS) is now the conditioned stimulus (CS) and produces the conditioned response (CR)
• Fear Conditioning Mechanisms


  • Neural circuits in the cerebellum mediate most forms of stimulus-response learning
  • Fear is an emotional response and produces activation in the amygdala
  • Although eyeblink and fear conditioning are Pavlovian conditioning processes, different brain areas mediate learning
• Operant Conditioning


  • Instrumental conditioning
  • Learning that is controlled by the consequences of the organisms behaviour
  • Learn the association between making a response and having a specific consequence occur
  • Learning that our actions can make a certain event occur in the environment through experience
• E. L. Thorndike's Law of Effect


  • "If a response, in the presence of a stimulus, is followed by a satisfying state of affairs, the bond between stimulus and response will be strengthened."
  • Satisfaction = stamping in
  • Discomfort = stamping out
• Operant Conditioning


  1. Stimulus

  2. Response

  3. Outcome
• Operant Conditioning Mechanisms


  • Operant learning is not localized to any particular brain circuit
  • Necessary circuits vary with the task requirements
• Types of Memory


  • Implicit memory (aka procedural memory)
  • Explicit memory (aka declarative memory)
• Amnesia


  • Anterograde amnesia: loss of ability to assimilate and retain new knowledge
  • Retrograde amnesia: loss of memory for events that have happened in the past
• Priming


  • Using a stimulus to sensitize the nervous system to a later presentation of the same or a similar stimulus
  • Unconscious learning
• Learned actions


  Testing for improvements in motor actions
• Encoding and Processing Memories


  • Brain processes explicit and implicit information differently
  • Implicit information processed in a bottom-up or data-driven manner
  • Explicit information processed in a top-down or conceptually driven manner

  
• Short-term memory


  • Information held in memory only briefly, then discarded
  • Involves the frontal lobe

  
• Long-term memory


  • Information held in memory indefinitely, perhaps for a lifetime
  • Involves the temporal lobe

  
• Storing Memories


  • Jeffrey Binder and colleagues (2009)
  • Meta-analysis of 120 fMRI semantic memory studies
  • Evidence for network of seven different left-hemisphere regions, including regions of the parietal lobe, temporal lobe, prefrontal cortex, and posterior cingulate cortex
  • Not all regions active at once when a semantic memory is stored
  • Subregions relatively specialized for specific object characteristics or types of knowledge

  
• • This identified network similar to "default network"
  • Issue because activity during rest is similar to activity during cognitive tasks
  • Semantic processing constitutes large component of cognitive activity evenduring passive states
• Episodic or Autobiographical Memory


  • Memory for events/episodes we have experienced
  • What we did, who was there, where we were, etc.
  • Linked to specific place and time contexts
  • Involves the ventromedial prefrontal cortex (vmPFC) and hippocampus, and the pathways between them

  
• Function of the Hippocampus

  • Hippocampal injury associated with poor episodic memory
  • Reduced hippocampal activity during episodic memory versus controls
  • Associated with impaired episodic memory
  • Increased vmPFC activity during memory retrieval as a result of partial compensation for hippocampal dysfunction
• Superior Autobiographical Memory


  • Highly superior autobiographical memory (HSAM)
  • Show superior personal memories but not superior cognitive functioning
  • Still susceptible to false memories
  • Increased grey matter in temporal and parietal lobes
  • Increased connectivity between temporal and frontal lobes

  
• Dissociating Memory Circuits


  • Karl Lashley searched unsuccessfully for the neural circuits underlying memories
  • Severity of memory disturbance related to size, not location, of injury

  
• Primary Structures for Explicit Memory

  • Medial temporal region
  • Entorhinal cortex
  • Parahippocampal cortex
  • Perirhinal cortex
  • Hippocampus
  • Amygdala
  • Prefrontal cortex

  
• Parahippocampal cortex


  • Visuospatial processing
  • Receives connections from the parietal cortex
• Perirhinal cortex


  • Visual object memory
  • Receives connections from the visual regions of the ventral stream

  
• Entorhinal cortex


  • Integration
  • Receives projections from parahippocampal and perirhinal cortices

  
• Hippocampus


  • Organisms with good visuospatial memory have larger hippocampi
  • Lesions to hippocampus impairs ability to learn and use visuospatial information
  • E.g., visual–recognition and object-position tasks

  
• Spatial Cells in Hippocampal Formation

  • Place cells: discharge when rats are in a spatial location, regardless of orientation
  • Head direction cells: discharge whenever a rat's head points in a particular direction
  • Grid cells: discharge at many locations, forming a virtual grid invariant to changes in the rat's direction, movement, or speed
• Reciprocal Connections


  • Neocortex projects to entorhinal cortex, which projects back to neocortex
  • Signals from the medial temporal regions to cortical sensory regions keep sensory experience alive in the brain so the neural record outlasts the experience
  • Pathway back to the neocortex means it is kept apprised of the information processed in medial temporal regions
  • Frontal lobe's role in explicit memory is subtler than that of the medial temporal lobe

  
• Frontal Lobe and Short-Term Memory


  • All sensory systems project to frontal lobes
  • During tasks in which monkeys must keep information in short-term memory over a delay, certain cells in the frontal cortex will fire throughout the delay
  • Animals that have not learned the task show no such cell activity

  
• Neural Circuit for Explicit Memories

  • Sensory and motor neocortical areas connect to medial temporal regions
  • Basal forebrain structures maintain appropriate activity levels in other forebrain structures
  • Temporal lobe central to long-term explicit memory formation
  • Prefrontal cortex central to maintaining temporary (short term) explicit memories and memory for the recency (chronological order) of explicit events