BY662 - Lecture 23 - Sensitization and Habituation (Learning)

What is stimuli?

A change in the internal or external environment

What is habituation?

A decrease in response to a stimulus after repeated presentations As the stimulus occurs over and over (and as long as it is not associated with any reward or punishment), we learn not to focus our attention on it. It is a form of non-associative learning that does not require conscious motivation or awareness. For example, an animal may be startled when it hears a loud noise, but if it is repeatedly exposed to loud noises and experiences no associated consequence, such as pain, it will eventually stop being startled.

Who was Eric Kendel and what was his contribution?

Aplasyia sea slugs CAMP, gill-withdrawal reflex, CREB Modern father for learning and memory in neurobiology

Long term memory requires what genes?

CRE CREB

What is long term sensitization?

Same as short-term, but PKA translocates to the nucleus and promotes CREB1 activator to produce CRE. Higher RNA expression of CRE increases synaptic plasticity (synaptic activity enhances) and allows short-term -> long-term.

What is signal transduction between sensory neurons and motor neurons?

Short-Term Sensitization- Serotonin -> Adenylate Cyclase -> cAMP -> PKA -> Glutamate Enhancement -> Motor Neuron Response

What type of stimulation causes the withdrawal response in the Aplysia?

Stimulation of the facilitator neuron causes the siphon sensory neuron to release more neurotransmitter (glutamate) at its synapse with the motor neuron, thus increasing the magnitude of the gill-withdrawal response.

Study of the gill-withdrawal in aplysia

Study of the gill-withdrawal reflex in the sea slug Aplysia has provided insight into short-term learning processes. This simple behavior exhibits three of the most elementary forms of learning familiar in vertebrates: habituation, sensitization, and classical conditioning. Habituation is a decrease in behavioral response to a stimulus following repeated exposure to the stimulus with no adverse effect. For example, an animal that is startled by a loud noise may show decreasing responses on prolonged repetition of the noise. Sensitization, in contrast, is an increase in behavioral response to a stimulus that does have an adverse effect.

Why study the siphon of the sea slug?

When a sea slug is touched gently on its siphon, the gill muscles contract vigorously and the gill retracts into the mantle cavity. This behavior is mediated by a simple reflex arc in which sensory neurons in the siphon synapse with motor neurons that innervate the gill muscles. In this section, we describe the short-term changes in synaptic function that occur during habituation, sensitization, and classical conditioning of the gill-withdrawal reflex in Aplysia.

What is sensitization?

an increase in behavioral response after exposure to a stimulus the strengthening of a neurological response to a stimulus due to the response to a secondary stimulus. For example, if a loud sound is suddenly heard, an individual may startle at that sound. If a shock is given following the sound, then the next time the sound occurs, the individual will subsequently react even more strongly to the sound. It is essentially an exaggerated startle response, and is often seen in trauma survivors.