ELM 19 Learning + memory 2 Flashcards
Question: What is Aplysia californica, and why is it used in research?
Answer: Aplysia californica, also known as the sea snail, is used in research to establish links between cellular studies and behavior. With approximately 20,000 neurons, it provides a simpler model system, making it easier to relate specific neurons to behavior.
Question: Why is Eric Kandel notable in the field of neuroscience?
Answer: Eric Kandel was awarded the Nobel Prize in 2000 for his research, particularly for his work with Aplysia californica, which significantly contributed to understanding the cellular mechanisms of learning and memory.
Question: Describe the anatomy of Aplysia californica.
Answer: Aplysia californica is a reddish-brown snail, typically measuring between 15 to 30 centimeters in length. It breathes through gills located on its back, covered by an overhanging mantle shelf and protected by parapodium. Water is drawn across the gill and evacuated through the siphon during respiration.
Question: What is the withdrawal reflex in Aplysia californica, and what purpose does it serve?
Answer: The withdrawal reflex in Aplysia californica involves the retraction of the gill and siphon in response to tactile stimulation. This reflex protects the delicate respiratory system of the snail from potential damage and indicates the formation of memory in the organism.
Question: What are the types of non-associative learning observed in Aplysia?
Answer: Non-associative learning in Aplysia includes habituation, where there’s a loss of response due to repeated stimulus; dishabituation, which is the recovery of an innate response; and sensitization, where the response becomes stronger than normal.
Question: How is classical conditioning demonstrated in Aplysia?
Answer: In Aplysia, classical conditioning involves pairing a neutral stimulus (such as a siphon stimulus) with a tactile stimulus to elicit a withdrawal reflex. Over time, the neutral stimulus becomes associated with the withdrawal reflex, leading to a conditioned response.
Question: What is differential classical conditioning, and how was it demonstrated in Aplysia?
Answer: Differential classical conditioning involves using two conditioned stimuli (CS) with different outcomes. In Aplysia, one group received siphon stimulus as CS+ and mantle stimulus as CS-, while another group received the opposite. The response showed that Aplysia responded more to the stimulus that was paired with the unconditioned stimulus (US).
Question: How is long-term memory demonstrated in Aplysia?
Answer: Aplysia exhibits long-term memory through distributed training (10 trials daily for 4 days) and massed training (40 trials in 1 day). It retains habituated responses for up to one day, shows sensitization for several weeks after training, and exhibits increased responses in classical conditioning even five days after training.
Question: What is the neural structure of Aplysia’s nervous system?
Answer: Aplysia’s nervous system consists of ganglia that communicate through connectives. Ganglia are arranged in bilaterally symmetrical pairs, with the abdominal ganglion controlling functions like heart rate, blood circulation, and respiration, and containing sensory neurons, interneurons, and motor neurons involved in withdrawal reflexes.
Question: Describe presynaptic facilitation in the context of sensitisation in Aplysia.
Answer: In sensitisation, presynaptic facilitation involves an increase in neurotransmitter release due to spike broadening and increased calcium influx. Serotonin plays a crucial role in inducing facilitation and enhancing sensory neuron excitability, motor neuron EPSP, and reflex amplitude.
Question: How does serotonin affect the biophysical properties of sensory neurons in Aplysia?
Answer: Serotonin temporarily closes potassium channels in sensory neurons, slowing the outward potassium current and repolarization of the membrane potential. This leads to spike broadening, increased calcium influx, enhanced neurotransmitter release, and heightened excitability.
Question: What molecular mechanisms are involved in the sensitisation of sensory neurons in Aplysia?
Answer: Sensitisation involves cyclic adenosine monophosphate (cAMP) acting as a second messenger. cAMP activates protein kinase A (PKA), which then phosphorylates substrate proteins, leading to enhanced synaptic transmission and increased excitability.
Question: How is long-term memory (LTM) for sensitisation achieved in Aplysia?
Answer: Repeated applications of serotonin or cAMP lead to persistent phosphorylation of preexisting proteins and the synthesis of new proteins. This results in long-term increases in synaptic facilitation, synaptic transmission, and the growth of sensory neuron processes, thereby contributing to the formation of long-term memory for sensitisation.
Question: Does postsynaptic protein synthesis play a role in sensitisation in Aplysia?
Answer: Yes, synaptic facilitation in sensitisation requires postsynaptic protein synthesis. While short-term facilitation does not rely on postsynaptic protein synthesis, long-term facilitation does, contributing to the structural and functional changes in neuron synapses observed during sensitisation.
