L9 - Learning and Memory: Hippocampus and Amygdala

Question 1

Neuroanatomy and Physiology:

Answer 1

• Neuron theory: Brain is made up of cells (neurons) and nerves are cell axons
• Learning and memory: Making and strengthening connections between neurons that represent associated concepts

Different components of memory are mediated by different parts of the brain

Question 2

Neurogenesis:

Answer 2

Neurogenesis = Generation of new neurons

• Neurons never regenerate or repair: damaged brain areas never “re-grow”

BUT

• New neurons constantly “born” throughout life from Neural stem cells
• Only two areas in adult brain:
  
  • Hippocampus (learning and memory)
  • Subventricular zone for olfactory bulb

Question 3

Synaptogenesis:

Answer 3

Synaptogenesis: Generation of new synapses (connections between neurons)

• MORE important than neurogenesis
• Synapses are constantly formed and strengthened with learning
• “Enriched” conditions (lots of stimuli) lead to growth of dendrites and more extensive synaptic connections

Question 4

Neuroplasticity:

Answer 4

The capability of the brain to alter its functional organisation as a result of experience

Sensory cortex: Sensory cortex areas expand with use and experience

• String musicians develop larger area on primary sensory cortex for left hand fingers

Motor cortex: After damage, motor cortex can re-organise with use to recover function

• Lesioned motor cortex in monkeys and used electrical stimulation to map hand area
  
  • No rehab = Maladaptive plasticity (motor cortex for that hand got smaller);
  • Rehab = Motor cortex area for hand expanding + ↑ movement

Visual cortex: Brain areas lacking their normal input can take new functions with use

• Visual cortex activity increased only in blind people reading brail (not sighted participants)

Question 5

Limbic System:

Answer 5

Medial temporal lobe

• Amygdala
• Hippocampus

Question 6

Amygdala:

Answer 6

• Fear and arousal
  
  • Responds to threat/danger (snakes, spiders, angry/fearful faces)
• Fear conditioning/learning/phobias involve classical conditioning

Question 7

Hippocampus:

Answer 7

Forming new episodic memories + spatial navigation (mental map of familiar environment)

• Damage causes memory loss (can’t form new memories)

Spreading Activation Model (theoretical): Activation (firing) of one neuron leads to spreading activation to related or connected neurons (concepts)

• Memory is represented by individual neurons each encoding specific concepts or objects (e.g. “Grandmother” cells: Neurons can “represent” (encode or “fire” to) a specific concept, such as your grandmother)
• Shared connections with neurons that represent related concepts (e.g. Fire-engine → Red, Truck, Fire, Siren)

Question 8

Learning and Memory in the brain: Long-Term Potentiation (LTP)

Answer 8

Change in the structure of synapses to give stronger signal from pre- to post-synaptic neuron

• Involves ↑ neurotransmitters + ↑ post-synaptic receptors

Question 9

Learning and Memory in the brain: Graded potentials:

Answer 9

Excitatory and inhibitory inputs (via dendrites) sum together to change membrane potential at axon hillock; dependant on strength of synapse connection (on dendrite)

• Strong stimulus = Large change in membrane potential;
• Weak stimulus = Small change For neuroplasticity ONLY, the strength of the synapse changes with learning

Question 10

Hebb’s law: “Neurons that fire together wire together”

Answer 10

When an axon of cell A is near enough to excite cell B and repeatedly or persistently takes part in firing it, some growth process or metabolic change takes place in one or both cells; A’s efficiency at firing B is increased

• Hebbian Learning: Repeated firing of pre- and post-synaptic neuron AT THE SAME TIME strengthens synaptic connection
• Brain “learns” associations via repeated pairings which strengthens connections between paired stimuli/events