1. Effects of repeated stimulation: Habituation

2. Habituation
Learning not to respond to a previously meaningful stimulus
The stimulus used to predict something.
Now the stimulus loses its predictability and you ignore it
Allows efficiency in learning

3. Habituation
Learning not to respond to a previously meaningful stimulus
The stimulus used to predict something.
Now the stimulus loses its predictability and you ignore it
Allows efficiency in learning

4. Habituation
Learning not to respond to a previously meaningful stimulus
The stimulus used to predict something.
Now the stimulus loses its predictability and you ignore it
Allows efficiency in learning

5. Habituation
Learning not to respond to a previously meaningful stimulus
The stimulus used to predict something.
Now the stimulus loses its predictability and you ignore it
Allows efficiency in learning

6. Habituation
Learning not to respond to a previously meaningful stimulus
The stimulus used to predict something.
Now the stimulus loses its predictability and you ignore it
Allows efficiency in learning

7. Dishabituation When the stimulus changes
Signals a change in the situation or setting
No longer appropriate to ignore, as changed stimulus may have meaning
Why? Something has changed in environment
check to see if it is meaningful
react to new situation, adapt!

8. Characteristics of habituation
Response decrement: response strength decreases with repeated stimulation. Spontaneous recovery: if the stimulus is withheld and then re- presented, the organism will react to the stimulus Repeated series: with repeated series of exposure, response strength is less ad less Generalization: similar stimuli may exhibit habituation when presented Dishabituation: what has been habituated can be dishabituated

10. Examples of habituated behavior
Salivation responses
Visual attention in human infants
Startle response in rats
Attention to your mother
Reaction to fire alarms in college dorms!

11. Sensitization When aroused, even light stimuli elicit strong reactions
Are sensitized: opposite of habituation
Over-react to stimuli
Over vigilance or hypervigilance
When do we see this?
Overly hungry/thirst
Sexual behaviors
Aggression
Fear

12. WHY do we show habituation and sensitization?
It is adaptive! Ignore what is irrelevant Attend or hyper-attend to what is important Is habituation and sensitization passive or active learning?

13. Isn’t this just fatigue or excitement?
Is habituation/sensitization the same or different from sensory adaptation or response fatigue?
Sensory Adaptation: occurs when you overstimulate a sense system: overuse the receptors; must wait our refractory period
Response fatigue: the muscles are tired from responding
How is learning to habituate or become sensitized different than this?

14. Example: Visits to a Nudist Colony
when first get there- S (naked people) --> R (lots of blushing)
staring behavior decreases over your stay: repeated exposure
if leave and come back (repeated series) gets easier with each trip: you adjust faster the more often you leave and come back
the more nude bodies- the easier to habituate: Frequency of stimulation
might generalize: less embarrassed in locker room, etc.
some one comes in with a camera- suddenly embarrassed again - dishabituation

15. Other Examples: Solomon's research on dogs supports this:
Dog presented with series of shocks
with repeated presentations of shock, the dog's overt behaviors and heart rate response was smaller
however, the after reaction (decrease in heart rate at cessation of shock) was greater
it took longer for the heart rate to return to normal

16. Other Examples: Visual attention in infants
Depending on size/complexity of stimulus
Infants showed simple habituation to simple visual stimuli
But: when shown stimulus again, showed increased sensitization (looked at it more)
Drug addiction: will talk about this with classical conditioning
Thrill seeking: go from frightened to adrenaline rush then recovery

17. Context is important Depends on how/when/where stimulus is presented
That is, reaction varies depending on context
Startle response:
Sitting talking with friends
Knowing that someone is about to jump out at you and beating them to the “boo”
Watching a scary movie
A startle will produce different levels of reaction across these settings

18. Context is important
Touch and sexual responses are another good example
Touch by a doctor
Touch by your mom
Touch by your lover
All can touch your face, ear, arm, etc., but it is context that regulates how you react to it.

19. Why habituation and sensitization?
Adaptive: Learn what to attend to and ignore
Things are more exciting the first time they happen!
Can’t attend to everything: need to learn what the important stimuli are
Important stimuli change depending on context and experience
If don’t learn, die!

20. What happens physiologicallY?
Simple Systems Approach: Eric Kandel
Look for similarities in process of habituation across species
See strong similarities in terms of behavior
Are physiological correlates also similar?
Why is this important?
If there are strong physiological AND behavioral similarities, suggests that there are generalizable principles and structures that underlie habituation
Suggests that this is a very basic and critical type of learning
If all organisms show it, must be very robust
Must be necessary for survival

21. The Sea Aplysia A large marine snail
Contains only a few thousand neurons so can map the neurons much more easily than larger animal
Examine siphon or fleshy spout withdrawal response
When you poke the siphon, it withdraws into the snail

22. Gill-withdrawal reflex
Siphon contains 24 sensory neurons that respond to tactile stimulation
6 motor neurons control the gill-withdrawal response
Each sensory neuron has a monosynptic connnection
Direct connection that involves just one synapse
Connects to EACH of the 6 motor neurons
Axons from other sensory neurons involved in polysynaptic connections
indirect connections mediated by 1 or more interneurons
Also connect to these motor neurons

23. Habituation of the Siphon
Stimulate by touching once every minute for trials
Get habituation within this time
Habituation lasts about 1 hour but can extend to 24 hours
If continue this stimulation for 3-4 days: long term habituation
Lasts several weeks
Change in way withdrawal reflex occurs
Think of the parameters of habituation: what would you expect?

25. What is happening to neurons?
During habituation: decrease in excitatory conduction always occurs in synapses involving the axons of the sensory neurons
NO change in postsynaptic neuron’s sensitivity to the neurotransmitter
What changed?
Amount of transmitter released by presynaptic (sensory) neurons
With repeated stimulation: LESS transmitter released into synapse
Similar process found in other animals as well
Won Nobel prize for this work!

26. chemical mechanisms in Habituation?
Each time a neuron fires, is an influx of calcium (Ca+) ions into the axon terminals
Calcium responsible for release of neurotransmitter
Calcium current into axon terminals becomes progressively weaker with repeated stimulation

27. Why important? Physiological demonstration of learning
Later work shows LTP and LTD of axons
Able to pinpoint neural changes responsible for habituation
Habituation does not necessarily involve long term anatomical changes, but temporary chemical changes
Thus appears that learning is flexible:
In short term, is likely due to chemical changes
For more permanent memories: anatomical changes

28. Explanation: Opponent Process Theory
For every action there is a reaction (wait, isn’t that physics?)
Solomon and Corbitt (1974)
lots of attention
made very "broad"- tried to apply to everything
Undermined their own theory

29. Two (okay 4) effects
Primary affective reaction: initially excited by unexpected event-
get euphoria from this
which will peak:
E.g., Think have won the lottery
Adaptation phase and steady level: euphoria levels off
Peak of after-reaction: a let-down occurs- you were one number off- get "depressed“
Decay of after reaction: return to baseline levels

30. Church, et al., 1966
Dogs receive 10-s shock while restrained in harness
at first- many overt responses
freezing
escape behaviors
pain behaviors
at termination of shock: stealthy, hesitant, unfriendly behavior
after short time: friendliness reappeared heart rates paralleled these changes

31. Model Assumes that:
For every hedonic reaction (state A) will come opposing reaction (state B) Decline in hedonic value from peak of state A to steady level will result from state B's effect of reducing state A Steady level of hedonic intensity is state A minus state B When stimulus creating state A stops, full force of state B is felt State B slowly decays until hedonic intensity turns to 0

32. Two main states critically differ:
usually are opposite reactions
State A develops quickly, closely associated w/intensity of stimulus that produces it
when stimulus triggering state A is removed, state A ceases
state B develops slowly, produced as reaction to A
is slow to decrease, when state A ceases, decays

33. Effects of Repeated Stimulation
repeated presentation of stimulus eliciting state A habituation occurs in state A
repeated elicitation of state B strengthens state B and reduces intensity of state A
thus: REPEATED presentations of the stimulus that triggered state A will actually lead to a reduction of state A --> because state B increases in intensity
that is: w/extended experience:
the reaction to the initial stimulus will be smaller than before,
but the after reaction will be larger and of longer duration

35. Critique of Opponent Process Theory
Great deal of older research to support the basic phenomenon common criticism: little actual evidence as to actual physiological mechanisms that might correspond to hypothetical a and b states various research shows vastly different time course between examples: immediate to months long

36. Critique of Opponent Process Theory
Several Good aspects of theory
as long as emotional responses conform to predictions of theory, not matter whether these are based on single or multiple physiological mechanisms
Theory is basically predictive
good descriptive model, fairly well supported by research
greatest virtue may be its attempt to unite diverse emotional situations into single framework
allows for commonalities between emotional responses

37. Habituation and eating
Eating involves repeated presentation of visual, olfactory, gustatory and tactile cues
Habituation involves decreases in physiological and behavioral responses to food
We eat in food bouts:
Begin a bout, often a brief increase in intake rate, followed by a decreasing rate until cessation
Time between bouts can vary
Presence of other foods
Presence of other activities
Physiological states: physical and emotional/affective

38. Habituation and eating
What factors affect rate of habituation when eating?
Dishabituation: presentation of another food increases eating (but not necessarily for original food)
Variety of foods at meal slows habituation
Different foods act as novel stimuli inbetween bites of original food
Different foods slows habituation to one another
Distractors: adding a distractor task slows habituation

39. Long term habituation Often studied for startle, fear responses
Think fire alarms:
Repeated presentation with no cause
Stop paying attention to fire alarm
Generalizes to other settings
VERY little research on LTH in humans or even other animals
Little evidence that it occurs for eating/food

40. Affective/emotional/motivational states
Classical conditioning is part of eating:
associate food with X
these are often “motivational” or affective/emotional states
Comfort foods: foods associated with comfort
Often from childhood
Eat to make us emotionally feel better
AESOP:
affective extension of standard operating procedure
assumption that classical conditioning links emotions and food consumption

41. Habituation and eating!
Taking what we know about habituation and applying to food intake (especially in humans).
Eat a single food in a meal = faster habituation
Distractions reduce rate of habituation
Reading
Watching tv
talking
Dishabituation occurs during meals:
eatIng another food affects habituation for each food
Should we eat 1 food or many foods at a meal?
What is the effect of drinking/beverages?
In animals: eating bouts followed by drinking bouts
Same in humans
Does drinking = dishabituation?
Does drinking = disruption of eating?
Why do bars give out free popcorn and restaurants bring drinks before ordering?

42. Memory and eating Memory for food is important
Do we like this food? Is it familiar? It is rich? Etc….
Differences in individuals for memory for any given food
Also individual differences in memory for intake of food
Particularly normal body weight and obese
Anorexics, bulimic individuals show differences from typical body weight individuals
Important factor is sensitization:
Food tastes better to some
Physical differences: more or fewer taste buds
Bodily states
Personal experiences

43. Memory and eating Learning is important part of this memory
Clean plate club or not?
Individual differences again:
Highly sensitized individuals more prone to overeating?
Differences in processing of stimulus signals
Is over-eating an addiction?
Differences in way we react to food
Differences in size of DA spike for foods across individuals
Some people may be physiologically primed to become “addicted”

44. Isn’t overeating just sensory specific satiety?
Authors argue that eating is more than simple satiety
Satiety = full; stop eating because you have had enough
Habituation = stop eating because you are “tired of the food”
Two are not necessarily related!
Habituation model assumes:
Hedonic value of one food may influence hedonic value of another food
Allows for dishabituation, distraction effects
Assumes habituation is a normal nervous system processes
Sensory specific satiety only deals with eating and food, not other kinds of stimuli
Habituation model assumes that LEARNING is critical factor
All the associative stimuli influence intake
We eat long after it “tastes good”

45. Implications of habituation model of eating:
We must examine individual differences in
Dopaminergic/reward systems
Behavioral histories with food
Emotional/affective states
Unlike in animals, eating for most humans is NOT an energy intake regulation behavior, but a learned behavior
We eat because we are
Hungry
Bored
Upset
Replacing a thwarted activity
It feels good

46. Good eating practices? Present low fat/healthy food in variety
Lots of different kinds of these foods presented at once
Encourage low rates of habituation
Even encourage disruptors
Present high fat/unhealthy food alone
Eat alone in absence of disruptions
Allow for faster habituation of that food
But: don’t assume long term habituation!