Transcript Figure 2.10
Concepts of Habituation and Sensitization • Habituation and sensitization are two fundamental ways that all organisms respond to previous experience with an eliciting stimulus • Habituation effects: Decrease in responsiveness with repeated exposure to a particular eliciting stimulus • Sensitization effects: Increase in responsiveness with repeated exposure to a particular eliciting stimulus • Sensitization and Habituation help us organize and focus our behavior by reducing the number of stimuli to respond to and which not to respond to Characteristics of Habituation and Sensitization • Habituation to startle Figure 2.10 • Time Course of Habituation – Habituation does not always persist for extended periods of time (weeks or months) – Short-term Habituation • response decreases within minutes • from frequent presentation of stimulus over short time • Spontaneous recovery is usually complete – Long-term Habituation • can persist for many days • from infrequent presentation of stimuli over longer time (many days) • spontaneous recovery is usually incomplete Spontaneous Recovery FIGURE 2.10 Startle response of rats to a tone presented once a day in Phase 1, every 3 seconds in Phase 2, and once a day in Phase 3. (Based on “Long-Term Retention of the Habituation of Lick Suppression and Startle Response Produced by a Single Auditory Stimulus,” by R.N. Leaton, 1976, Journal of Experimental Psychology: Animal Behavior Processes, 2, pp. 248–259.) The Principles of Learning and Behavior, 7e by Michael Domjan Copyright © 2015 Wadsworth Publishing, a division of Cengage Learning. All rights reserved. Characteristics of Habituation and Sensitization Time Course of Habituation • Spontaneous recovery after a period of time (days) without repeated stimulus presentation • when stimulus is again presented • response to the stimulus returns • size of spontaneous recovery • depends on characteristics of the stimulus and frequency of the repeated stimulus • fast simple reflexes (eye blink) have very robust recovery • short-term habituation has more robust recovery • Spontaneous recovery video Characteristics of Habituation and Sensitization • Sensitization and the Modulation of Elicited Behavior – Typically (but not always) short-lived – With only a repeated stimulus • salivation reflex seen in Figure 2.5 • visual attention seen in Figure 2.7 – With loud background noise which increases arousal • repeated stimulation elicited more vigorous startle reactions in Fig 2.1 • Common in movies and at concerts – Eyeblink startle response modulated by threat of shock and type of picture • group 1: threat of shock during pleasant pictures • group 2: threat of shock during unpleasant pictures • threat of shock produces more response • pleasant pictures without threat of shock produces the least response • Figure 2.12 • Emotional disorders such as anxiety, depression or PTSD FIGURE 2.11 Magnitude of the startle response of rats to successive presentations of a tone with a background noise of 60 or 80 dB. (Based on “Sensitization of the Rat Startle Response by Noise,” by M. Davis, 1974, Journal of Comparative and Physiological Psychology, 87, pp. 571–581.) The Principles of Learning and Behavior, 7e by Michael Domjan Copyright © 2015 Wadsworth Publishing, a division of Cengage Learning. All rights reserved. The Principles of Learning and Behavior, 7e by Michael Domjan Copyright © 2015 Wadsworth Publishing, a division of Cengage Learning. All rights reserved. Discrete and Recurrent Traumatization in PTSD • Symptoms of PTSD include hyperarousal and exaggerated startle • Potentiated startle (eyeblink) reflex using trauma imagery was larger in PTSD patients compared to control participants • Patients with a single, discrete trauma showed extreme startle potentiation to their fear memories • Patients with recurrent traumatization • had the least startle potentiation to their fear memories • more extensive comorbidity such as major depression and anxiety disorders as well as longer enduring PTSD • Individuals with a history of repeated trauma such as childhood physical and/or sexual abuse are the most vulnerable Dual-Process Theory • The most prominent theory developed to explain Habituation and Sensitization • Habituation and sensitization processes have different underlying neural mechanisms • The same stimulus can activate both underlying neural processes • These processes compete for control of behaviour Stimulus-Response (S-R) system versus the State system • Habituation processes occur in the S-R system • activated every time an eliciting stimulus is presented • shortest path (circuit) between sense organs and muscles • Sensitization processes occur in the state system • emotional and motivational states • activated only by arousing events such as fear or hunger • Involve other pathways (circuits) that relate to organisms general level of readiness or responsiveness • Actual behaviour reflects the combined actions (summation) of the S-R and state systems Implications of the Dual-Process Theory •S-R system always involved in processing stimuli so habituation is always possible •State system modulates the response depending on amount of arousal •Stimulus specificity • Habituation is specific to the stimulus that is repeatedly presented • A change in the stimulus will interrupt A difference in a critical feature of the stimulus • Change in taste stimulus (sweeter) • Change in sound (different source of sound or louder sound) •Sensitization is not highly stimulus-specific, Footshock increases sensitivity to auditory and visual cues Application of the Dual Process Theory •Infant attention to complex 12X12 pattern shows more arousal (State system) then 4X4 pattern (see figure 2.7) •With a background noise of 80 db rats have more arousal (state system) (see figure 2.11) •Discrete and Recurrent Traumatization in PTSD Extensions to Emotions and Motivated Behavior • Stimuli “your romantic partner” can elicit complex emotional responses such as love • Stimuli “drinking alcohol” can elicit complex physiological responses • These complex emotional and physiological responses can habituate with repeated exposure Opponent-Process Theory (Solomon & Corbit, 1974) • Three features of emotional reactions to various stimuli – 1. Biphasic- primary reaction to the eliciting stimulus and the opposite “after-reaction” when exposure is discontinued – 2. With repeated exposure to the stimulus, the primary reaction becomes weaker – 3. With repeated exposure to the stimulus, the “after-reaction” becomes stronger – Habituation of primary drug reaction is partially responsible for drug tolerance • Decline in effectiveness (amount of response) of drug with repeated exposure • Enjoyment decreases and crashes or hangovers more severe – Habituation of Love: • Infatuation (initial reaction) declines over time • grief at the loss of partner even after initial affection has declined is very intense (after effect) The Opponent-Process Theory of Motivation • Primary process or "a" process: An emotional reaction :to presentation of emotion-arousing stimulus pushes us away from emotional equilibrium • Opponent reaction or "b" process: Opposite emotional reaction elicited by primary or a process to bring emotions back into equilibrium Opponent process "b" lags the onset of the primary process "a" • Strength of the opponent process "b" subtracts from the strength of the primary process "a" • After the stimulus is remove "a" process ends so Opponent process "b" dominates the response • The pattern represents the net effect of the two opponent processes or forces Fig. 2.15 FIGURE 2.15 Opponent process mechanism during the initial presentation of an emotion arousing stimulus. The observed emotional reactions are represented in the top panel. The underlying opponent processes are represented in the bottom panel. Notice that the b process starts a bit after the onset of the a process. In addition, the b process ends much later than the a process. This last feature allows the opponent emotions to dominate after the end of the stimulus. (From “An Opponent Process Theory of Motivation: I. The Temporal Dynamics of Affect,” by R. L. Solomon and J. D. Corbit, 1974, Psychological Review, 81, pp. 119–145.) Primary After Reaction The Principles of Learning and Behavior, 7e by Michael Domjan Copyright © 2015 Wadsworth Publishing, a division of Cengage Learning. All rights reserved. The Opponent-Process Theory of Motivation • Opponent Mechanism After Extensive Stimulus Exposure – – – – initial "a" process is little changed Opponent process "b" becomes strengthened with repeated activation Opponent process "b" dominates the response So after response is very large becasue "b" process is large and unopposed by the "a" process (Fig 2.16) • Opponent Aftereffects and Motivation Pleasure of drugs gone for habitual users and negative effects of withdrawal is much stronger • Drug addiction is theorized to be an attempt to minimize the aversiveness of the negative aftereffects (i.e., to reduce withdrawal not obtain pleasure ) FIGURE 2.16 Opponent process mechanism that produces the affective changes to a habituated stimulus. The observed emotional reactions are represented in the top panel. The underlying opponent processes are represented in the bottom panel. Notice that the b process starts promptly after the onset of the a process and is much stronger than in Figure 2.15. In addition, the b process ends much later than the a process. Because of these changes in the b process, the primary emotional response is nearly invisible during the stimulus, but the affective after-reaction is very strong. (From “An Opponent Process Theory of Motivation: I. The Temporal Dynamics of Affect,” by R. L. Solomon and J. D. Corbit, 1974, Psychological Review, 81, pp. 119–145.) Primary After Reaction The Principles of Learning and Behavior, 7e by Michael Domjan Copyright © 2015 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.