L&M Lecture 4: Habituation and Sensitization PDF

9/3/2024 Habituation and Sensitization ​ Learning from repeated exposure ○​ We’re constantly bombarded with information from multiple senses but we have a limited capacity to react ○​ An adaptive function of the mind is to learn to predict which stimuli are...

9/3/2024 Habituation and Sensitization ​ Learning from repeated exposure ○​ We’re constantly bombarded with information from multiple senses but we have a limited capacity to react ○​ An adaptive function of the mind is to learn to predict which stimuli are important and to prioritize responses to them ○​ This process can be voluntary, when you choose to focus on something, but also occurs at an unconscious, involuntary level ○​ Habituation and sensitization are simple, universal forms of learning from experience ○​ Allows psychologists to understand how organisms: ​ Identify novel events ​ Discriminate (tell the difference) between similar stimuli ​ Adjust behavior in response to threats and other important events ​ Habituation ○​ A decrease in the strength or occurrence of a behavior after repeated exposure to the stimulus that produces the behavior ○​ Reduction in innate responses that occur automatically in response to certain types of stimuli ​ Startle response: defensive response to a sudden, unexpected or threatening stimulus ​ Whole body startle, protection of head/neck ​ Orienting response: innate reaction to a novel stimulus or change in the environment ​ Response to stimuli that are not strong enough to elicit startle ​ Principles of habituation ○​ Habituation is slower/less likely to occur with more intense stimuli ○​ Spontaneous recovery: a stimulus-evoked response that has been weakened by habituation increases in strength or reappears after a period of no stimulus presentation ○​ Stimulus specificity: habituation to one event doesn’t cause habituation to all other stimuli in the same sensory modality ​ Response to new stimuli depends on similarity to original, habituated stimulus ○​ Dishabituation: a renewal of a response, previously habituates, that occurs when the organism is presented with a novel stimulus ○​ Long term habituation: accumulation of habituation effects across repeated sessions of exposure to a stimulus ​ Habituation summary  ○​ Habituation is ubiquitous: found throughout the animal kingdom, even in some single-celled organisms ○​ Across all these organisms, there are common principles in how habituation works: ​ More likely to habituate to innocuous (weak) stimuli ​ Spontaneous recovery ​ Stimulus specificity ​ Dis-habituation ​ Short and long term forms ​ Spaced presentation works betters than massed exposure for creating long term habituation ​ The downside of habituation ○​ Most of the time it occurs with benign stimuli that are unchanging, uninteresting, or don’t require attention ○​ In some cases it may be bad to habituate ​ Low battery on smoke detector ​ From habituation to sensitization ○​ Habituation: a decrease in the strength or occurrence of a behavior after repeated exposure to the stimulus that produces the behavior ○​ Sensitization: phenomenon in which a salient stimulus temporarily increases the strength of responses to other stimuli ​ Sensitization ○​ The stronger the stimulus, the less habituation ○​ With very strong (noxious) stimuli, sensitization occurs ○​ Weak/useless stimuli are ignored, by painful/important stimuli draw attention ○​ Effects of sensitization are typically short lived, but it’s possible to have long term sensitization: chronic state of heightened arousal that increases responses to weak/innocuous stimuli ​ Chronic pain following injury ​ Repeated stressors lead to stress sensitization ​ Sensitization vs Habituation ○​ Like habituation, sensitization ​ Is a ubiquitous process found throughout the animal kingdom ​ Effects typically rapidly diminish, but can also persist over long time periods ○​ Unlike habituation, sensitization ​ Only occurs for highly arousing stimuli ​ Is not stimulus specific (increases responsiveness to all kinds of stimuli) ​ Can occur with a single noxious stimulus (although effect increases with increased repetitions)  ○​ Habituation is stimulus-specific: weakening of response to familiar, uninteresting stimuli ○​ Sensitization is not stimulus-specific ​ Paying attention to everything going on to assess the situation ​ Quiz 1 Review ○​ Diffusion tensor imaging allows researchers to map the structural connections between different regions of the brain ○​ Functional neuroimaging maps changes in oxygen levels ○​ We have cues that allow us to recognize important things (penny) ​ Dual process theory ○​ Groves and Thompson proposed that habituation and sensitization reflect activation of two different systems: ​ A low threshold reflex pathway that weakens with repeated use ​ After repetition of the same stimulus, the connection between the sensory and motor neurons have weakened, leading to a smaller response ​ A second, similar stimulus will activity the same sensory neurons leading to a similar weak response ​ A high threshold state system that, when activated, increases responses globally (to all stimuli) ​ A noxious stimulus will produce a reflex response and lead to activation of the state system when then potentiates other connections between sensory and motor neurons ​ The next time the weaker stimulus occurs, it is more likely to produce a response ○​ Explains several features of habituation and sensitization ​ Weak stimulus: primary reflex pathway activation leading to a stimulus specific decline in responsiveness ​ Highly arousing stimulus: state system activation leading to generalized increase in responsiveness ​ Aplysia ○​ Aplysia californica, the sea hare, has only 20,000 neurons in its CNS, the neurons are very lage ○​ Popular for studying the neural mechanisms of learning and memory ○​ Gill withdrawal reflex: ​ Touch the tail, siphon, or gill ​ Gill contracts within the mantle ​ Relaxation time is measured ○​ Reflexive response to potential threats ​ Habituation in aplysia  ○​ Gentle touch to siphon leads to gill withdrawal reflex ○​ Repeat same touch every 10-15 minutes ○​ Progressive shorter withdrawal durations (habituation) ○​ Recovers quickly but with many sessions becomes long lasting ​ Sensitization in aplysia ○​ Gentle touch to siphon leads to gill withdrawal ○​ Aversive shock to tail ○​ Next touch to siphon leads to longer withdrawal duration ○​ Recovers quickly, but becomes long lasting with multiple sessions ​ Habituation and sensitization in aplysia ○​ Short term: repeated weak stimulation leads to synaptic depression in connection between sensory neuron and motor neuron (less release of neurotransmitters) ○​ Long term: reduced number of synaptic connections between sensory and motor neurons ○​ Stimulus-specificity: effect is homosynaptic (does not carryover to synapses involving other neurons) ○​ Tail shock activates interneurons that release serotonin ○​ The serotonin modulates multiple sensory neurons to release more transmitters on next activation (effect is heterosynaptic) ○​ In long term sensitization, new sensory-motor synapses are added