Hippocampus

I’ve got my thinking cap on. Will it help me remember?

Thinking and memory aren’t the same thing but highly related. Human memory is composed of several systems. It’s not a single process. Memory involves nearly every part of the brain, both sides.

The two hemispheres are connected by the corpus collosum. This bundle of neurons keeps our two super computers in touch with each other. One side names the object that your other side is reaching for. It’s teamwork.

 

 

NOTES

• Memory
  • Frontal lobe
    • Prefrontal cortex
      • 3 regions
      • 1. dorsolateral (previously)
      • 2.orbitofrontal (previously)
      • 3. ventralmedial
• 3. Ventralmedia
  • Anterior cingulate cortex
    • Collar around corpus collosum
  • Corpus collosum
    • Two Computers
      • Left and Right Hemispheres
    • Each controls contralateral side
      • Except taste and smell
      • Uncrossed
      • Its own side of the tongue
    • Work together
      • Control trunk & facial muscles
      • Staying Connected
    • Corpus Callosum is a set of axons
      • Interconnect hemispheres
      • Exchange information
      • Wide, flat bundle of neural fibers
      • Under cortex
      • Largest white matter structure
      • 200–250 million axons
      • Fast transmission (myelinated)
    • Parts
      • 1. Genu = anterior (knee)
        • Thin axons
        • Connect prefrontal cortexes
        • Larger in musicians
      • 2. Truncus = middle (body)
        • Thick axons
        • Connect motor cortexes
        • M1, premotor & supp. motor
      • 3. Splenium = posterior portion
        • Soatosensory info
        • Parietal lobes
        • Visual cortexes
    • Size
    • Sexual Dimorphism
      • Different size in men & women? No.
    • R. B. Bean,1906
      • Larger is intelligence
      • Men
      • Race
      • Ultimately refuted
    • Larger in left-handed?
      • 11% bigger
    • Dyslexic children have smaller CC
  • Childhood
    • Gradually thickens as grow
    • Slow growth until about age 10
    • Eventually develop adult patterns
    • Young children behavior similar to split-brain people
    • Fabric identification task
    • Five-year olds
      • Equally well w/ one or two hand
    • Three-year olds
      • 90% more errors w/ two hands
• Lateralization of Function
  • Epilepsy
  • Seizures = excessively synched neural activity
    • Most treated with drugs (90%)
    • More severe, tissue ablation
    • Extreme, severe CC
  • Neural activity rebounds between prolongs seizures
  • Called split-brain people
• Split-brain people
  • Present input of object to L field
    • Info to R hem (noses cross)
    • L hand controlled by R hem
    • Can point to it with L hand
    • Can’t do it with right hand
  • Present input of object to R field
    • Info to L hem (noses cross)
    • Can name or describe what see
    • Language in L hem
      • 95% of R-handed
      • 80% of L-handed
  • Independence
    • Each hem. can process info
    • Multitask
    • Draw circles
      • One with each hand
      • One hand going faster
    • For a few weeks, feels like two people in one body
  • Competition vs Cooperation
    • Take item off grocery self with L
    • Return them with R
    • Eventually
      • Brain uses smaller connection routes to avoid conflicts
      • CC not the only path
      • Just the biggest
  • Cooperation
    • Flash different word to each visual field at same time
    • Report combined concept
• HM
  • Henry Molaison (1926-2008)
  • 1 generalized seizure a week
    • began bilaterally
    • in medial aspects of both temporal lobes
  • Removed both of H.M.’s medial temporal lobes (in 1953)
    • included most of
    • hippocampus
    • amygdala
    • adjacent temporal cortex
  • Post-surgery symptoms
    • Major seizures almost completely eliminated
    • Minor seizures down to 1-2 day
    • IQ increased (104 to 118)
    • Normal short-term memory
    • Moderate retrograde amnesia
      • loss for events shortly before
    • Severe anterograde amnesia
      • memory loss for events after
•  *******************
  • Amnesia
    • Types
    • retrograde amnesia = before
    • anterograde amnesia = after
    • Progression
      • Normal cognition
      • Retrograde amnesia
      • Coma
      • Confusion
      • Anterograde amnesia
      • Normal cognitive function
• *******************
• HM (more)
  • Post-surgery symptoms
    • Can’t transfer anything to LTM
    • Everything is forgotten when attention shifts
    • Impaired ability to form LTM
      • newer words like Jacuzzi and granola regarded as nonsense
    • When distracted
      • underestimate his own age by 10+ years
    • Can’t form episodic memories
      • memories of a single event
      • could describe previously learned facts
      • not recount personal events
    • Retained ability to
      • Weakly retain semantic (factual) memories
      • Difficult to describe the future
• HM’s Implicit Memory
  • Mirror Drawing
    • First to show improvement in HM
    • Spatial –motor learning
    • Implicit learning
  • Rotating Disc
    • Keep pen on target (rotating disk)
    • Improved over 7-day period
    • Each time saw task, claimed he had never seen it before
• Hippocampus
  • Temporal lobe & Dorsalmedial area of frontal lobe
  • Semi-circle
  • If damaged, amnesia
    • Remember before & after accident
    • Not accident or around it
  • If small damage
    • Retrograde amnesia
    • Can’t remember past
    • Just before accident
  • If bilateral damage
    • Anterograde amnesia
    • Can’t form new memories
  • Consolidation memory
    • move from short to long term
    • not necessary to retrieve info
    • must work to put into long term
  • Reproduces patterns during sleep
    • Encodes patterns
    • Sparse representations (non-overlapping)
    • Sparse encoding allows quick learning
    • Componential encoding
      • 9×9 pixel bit map
      • 81 pixels
      • like cortex
      • efficient
      • good for generalization
    • Sparse encoding uses 13 lines
    • Trains cortex
      • Repeats pattern over time
        • Find L in field of Ts
        • Patterns repeated
        • Ss unaware of pattern
      • Improves over time
        • No “thinking” required
        • Priming
• Memory Systems
  • Procedural Memory
    • What you can do
  • Sensory Memory
    • Buffers for vision & audition
  • Prospective Memory
    • Remember what going to do
    • Sensitive to elderly
  • Declarative (things you know)
    • Episodic (life story of events)
      • right hemisphere
    • Semantic (names and facts)
      • left hemisphere
• Neurotransmitters
  • Epinephrine
    • enhances consolidation
    • if blocked, interferes with memory formation
  • Cortisol
    • enhances consolidation
    • increase glucose availability?
  • Ginkgo Biloba may increase blood flow
  • Acetylcholine is necessary to form new declarative memories
• Non-Declarative Memory
  • Doesn’t use hippocampus
  • Non-word learning
  • Acquired slowly
  • Includes
  • conditioned responses
  • skills
  • habits
  • priming
•  Types of Memory
  • Short-term memory
    • Memory of events just occurred
    • About seven items (+-2)
    • Rehearsal to get it in
    • Once gone, lost forever
  • Long-term memory
    • Memory of previous events
    • Long-term memory is vast
    • Difficult to estimate how big
    • Rehearsal not needed
    • May recall with hints
  • STM can be moved to LTM
    • Held in working memory
    • If score changes, throw out old score
  • Consolidation
    • Varies widely between people & material
    • Interesting facts more than boring
    • Emotional items learned quickly
      • Cortisol activates
        • Amygdala
          • storage of emotional events
        • Hippocampus
          • Consolidates emotional event
    • LTM not permanent
      • Change, fade & vary in detail
      • Reconsolidate a memory if:
      • A reminder followed by similar experience
      • New experiences during reconsolidation can modify memory
• Working Memory
  • Temporary storage of tasks
  • Attending to right now
  • Delayed-response task
    • Ss given signal
    • Give response after a delay
    •  Damage to prefrontal cortex
      • Impairs working memory tasks
    • Older people often have impaired working memory
      • Prefrontal cortex may change as age?
• Amnesia
  • Memory loss
    • Better Implicit Memory
    • Nearly all patients with amnesia show better implicit memory
    • Impact of recent experience on behavior
      • even if not realize using memory at all
    • Not good at deliberate recall
    • Good at doing without knowing
• Usually
  • better implicit than explicit
  • normal working memory
  • nearly intact procedural memory
  • some retrograde amnesia
  • severe anterograde amnesia
• Hippocampal damage
  • Impairs performance on
    • Delayed matching-to-sample tasks
      • Task used in animals
      • Animals see an object (sample)
      • After a delay choose between two objects
      • Goal: choose one matches the sample
    • Delayed nonmatching-to-sample tasks
      • Same procedure
      • Except animal must choose the different object
• Spatial Memory
  • Hippocampal neurons
    • spatially tuned
    • to particular spatial locations
  • Cab drivers
    • Larger than normal posterior hippocampus
  • When answering spatial Qs
    • hippocampus activated
  • Need to recall detail & context
  • Recent memories have sig detail
  • Recalling recent memories
    • activates hippocampus
  • Recalling older memories
    • may not require hippocampus
• The Basal Ganglia
  • Needed for implicit learning
  • habit learning
• Other Brain Areas in Memory
  • Almost all brain involved in some aspect of memory
  • Amygdala used in fear learning
• Parietal lobe damage
  • Affects ability to associate one type of info with another
• Temporal lobe damage
  • Anterior & inferior lobes results in
  • Semantic dementia
  • Impaired semantic memories
• Prefrontal lobe damage
  • Impairs ability to learn about rewards and punishments
• Summary
  • Don’t lose all aspects of memory equally
  • Several somewhat independent kinds of memory
  • Each depends on different brain areas