PS121 Brain & Behaviour Term 1 Part 2 Flashcards

Question

Monosynaptic stretch reflex arc

Answer 1

▪ This reflex arc is responsible for the limb jerk reactions produced in response to tendon taps ▪ E.g., if you tap the patellar tendon, you elicit a knee-jerk response ▪ Tapping the tendon produces hardly any change in the length of the (quadriceps) muscles ▪ The change in length is usually less than the thickness of a hair and is too small to be detected by the spindle afferents

Answer 2

▪ It’s the 1a afferents that are involved and the 1a endings do not respond to the amount of stretch but to how quickly the stretch occurs ▪ There is hardly any stretch, but it occurs very fast indeed. Quickly enough to evoke a large response from the 1a endings

Answer 3

1. Simple responses: responses are things like blinks, muscle twitches and knee jerks 2. Stereotyped responses: performance always involves the same movements and/or muscle contractions 3. Mediated by spinal circuits (circuits located in the spinal cord) 4. Mediated by reflex arcs: mechanisms are basically chains of neurons (pathways) between sensory receptors and muscles 5. Repeatable: the same stimulus always evokes the same response 6. Not acquired or modified by learning and experience (because they are innate)

Answer 4

▪ Eliciting stimulus: irritation at a location on the skin (e.g., applied using a piece of acid soaked paper) ▪ Response: movement involving extension of rear leg wiping the ‘toes’ over the stimulus ▪ So foot positioning depends upon stimulus location ▪ The position to which the foot should be moved depends upon the position of the forelimb

Answer 5

▪ Conclusion: frog’s spinal cord “knows” where the limbs are as well as where the stimulus is ▪ The frog’s spinal cord deals with the following: 1. Knee or ankle joint immobilized with a cast 2. Ankle weighted with a heavy bracelet 3. Stimulus is on the head and the body bent over ▪ These reflex responses are not fixed sequences of joint motions or fixed patterns of muscle activations

Answer 6

The reflex response is NOT stereotyped. The reflex response is able to achieve the same outcome (removal of the source of irritation) under different circumstances (location of stimulus, body posture, body condition)

Answer 7

Midbrain level

Answer 8

Medullary level

Answer 9

To look at things and to stop retinal images jiggling around too much We move our eyes so the light can hit the most sensitive part of the eye the fovea

Answer 10

The vestibular organs are the semi-circular cannals Stimulation of the vestibular organs reflexively evokes eye movements All of this is in the brain stem The purpose of the vestibular-ocular reflex is to keep the eyes steady when the head jiggles When you move your head your eyes stay straight if you remain looking in the same direction

Answer 11

Counter-rotate

Answer 12

If vestibular organs are lost balance can be relatively restored.

Answer 13

John Crawford - lost his vestibular organs - he COULD not read blood pumping through the arteries in the neck made the eyes jiggle enough to make reading very difficult

Answer 14

Some animals can only move the eyes by moving their head. They need good reflexes to keep the head steady these are the vestibulocolic reflex and the cervicollic reflex.

Answer 15

Rapid movements of the eye from one position in the orbit to another are called saccadic eye movements The joint movement and direction of both eyes are called a conjugate eye movement Convergent eye movement - when the eyes move closer together towards the nose Divergent eye movement - when both eyes move further away from the nose The joint movement of the two eyes in opposite directions is called a disconjugate eye movement The slow movement of eyes to follow a moving object are called small pursuit eye movements

Answer 16

False - To make a left eye movement motor neurons in the left lateral rectus and the right medial rectus must both contract simultaneously.

Answer 17

To make a conjugate saccade to the left these two nuclei must be activated simultaneously How can this be done? Interneurons in the abducens nucleus connect to the contralateral oculomtor nucleus To make a leftward saccade activating signals are sent to the left abducens These excite the MNs and also interneurons that carry the signal to the right oculomotor nucleus Contraction of the two muscles on the left sides of the eyes is NOT sufficient The muscles on the right sides need to relax This is achieved by shutting off (inhibiting) excitation of these muscles

Answer 18

Paramedian pontine reticular formation. The PPRF generates a burst of excitation that causes the eyes to move rapidly to a new position (the saccadic movement itself) The signal from the PPRF is a ‘burst’, once it’s over the situation is back to what it was before the burst

Answer 19

Nucleus Prepositus Hypoglossi The holding signal is generated by nucleus prepositus hypoglossi The NPH contains loops (that feedback the output back into the nucleus) Because it contains loops, this circuit cannot be described in terms of chains (arcs) This is the basic circuit for generating the leftwards horizontal saccades (the circuit for rightward saccades involves the PPRF, NPH and NGD) Reflex saccades involve pathways from the sensory organs to the superior colliculi and then to the PPRF

Answer 20

Superior colliculi

Answer 21

Retinas > Superior colliculi > PPRF

Answer 22

Originates in the frontal lobes of the cerebral cortex Frontal cortex > Superior colliculi > PPRF When you make a voluntary saccade, you most often also turn the head as well You turn the head and the eyes to look in a new direction You need to turn the VOR off when you make a voluntary head turn to look in a new direction

Answer 23

1) Response can become more/less vigorous (incl. faster/slower, more forceful/less forceful) 2) Eliciting stimulus can become more/less likely to elicit the response 3) Response can more/less effectively produce an outcome 4) A stimulus can come to elicit a new response

Answer 24

1) Bodily injury or muscle fatigue: what kinds of changes are produced? 2) Increases and decreases in physical fitness or strength: what kind of changes are produced? 3) Learning: what kind of changes are produced? 4) Internal state/mood/intention: what kind of changes are produced?

Answer 25

Relatively behaviour ▪ A key element for distinguishing changes due to learning from those due to factors such as fatigue is that learning produces changes that are relatively permanent ▪ Fatigue wears off quite quickly whereas forgetting is slow

Answer 26

A learning process that leads to the reduced responsiveness of a reflex as a result of repeatedly eliciting the response. It reduces the vigour (strength) of an animal’s behavioural response to a stimulus over repeated elicitations. Habituation is learning NOT to respond to a stimulus.

Answer 27

Train-rest-test protocol

Answer 28

1) In the retention test, the response vigor is restored (similar to the start of the training phase) - restoration of vigour is called spontaneous recovery 2) In the retention test, the response vigor is not restored (similar to the end of the training phase) - conclude that habituation took place - decline in vigour due to learning

Answer 29

▪ Effects that last days or more are called long-term habituation effects Long term habituation Long term habituation: a learning process that produces effects that last for days or months and may take many repeated sessions on successive days to establish

Answer 30

▪ We know that there are some situations in which the effects of learning last only a short time (minutes or hours) Short term habituation: a learning process that produces effects that typically last less than an hour and can be established during one session on a single day

Answer 31

▪ A method exists: it involves a phenomenon known as dishabituation ▪ This is undoing or reversing an habituation effect by the presentation of an intense aversive stimulus – a kind of unlearning ▪ Habituation can be ‘undone’ by presentation of such a stimulus, but it does not undo the effects of fatigue ▪ Fatigue effects persist after the presentation of such a stimulus, whereas habituation effects do not Dishabituation ▪ Dishabituation establishes the existence of short-term habituation

Answer 32

Reflex responsivness/vigour is restored

Answer 33

Responsiveness and vigour increase after aversive stimulation if it has not previously been habituated.

Answer 34

The reflex can be readily habituated and sensitized – the following video shows the reflex itself and its sensitization by an aversive stimulus (electric shock) ▪ Sensitization occurs mainly in defensive reflexes, avoidance reflexes and related reflexes like orienting and startle reflexes ▪ It has the opposite effect to habituation and is responsible for dishabituation – it can undo the effects of habituation (more later)

Answer 35

(1) It normally occurs more quickly (fewer stimuli needed) (2) It is non-specific: the effects of habituation are confined to the elicited response (it is specific), sensitization affects all defensive, avoidance and related reflexes

Answer 36

▪ A single aversive stimulus may be sufficient to produce a short term sensitization effect that lasts from a few minutes to a few hours ▪ Repeated sessions separated by several hours (each consisting of a few aversive stimuli) produce long term sensitization effects that can last for days or weeks

Answer 37

▪ Have seen that the two process have opposite effects: the habituation process reduces reflex responsiveness, the sensitization process increases it ▪ According to dual process theory, sensitization undoes the effects of habituation and vice versa (they are opponent processes)

Answer 38

Opponent processes: they act in opposition to each other - what one does the other undoes

Answer 39

▪ The theory proposes that the habituation process is always engaged by an eliciting stimulus, regardless of its nature ▪ The sensitization process may be engaged, but to an extent that depends upon how aversive or arousing the eliciting stimulus is – the more aversive/arousing the greater the effect of the process ▪ Thus, when an eliciting stimulus is presented, both processes are engaged ▪ Engagement of the habituation process means that responsiveness decreases, but simultaneous engagement of the sensitization process produces the opposite effect ▪ Depends upon which process has the larger effect

Answer 40

▪ If the eliciting stimulus is non-aversive/non-arousing, the habituation process proceeds unopposed and the responsiveness of the reflex declines progressively with repeated elicitations

Answer 41

If an eliciting stimulus is aversive/arousing, the habituation process is still automatically engaged, but its effects are counteracted by a stronger sensitization process and reflex responsiveness increases progressively with repeated elicitations

Answer 42

Both processes are engaged, but cancel each other out – reflex responsiveness does not change ▪ Are there examples of reflexes which do not change in responsiveness/vigour over repeated elicitations? Dual process theory ▪ Of course: the pupillary reflex and the vestibular-ocular reflex are two examples that we’ve encountered

Answer 43

In summary: sensitization effects occur when the sensitization process is stronger than the habituation process; habituation effects occur when the habituation process is stronger; when the two are equally strong, there is no observable change in reflex responsiveness/vigour ▪ Dual process theory is also able to explain results like this Dual process theory Response amplitude ▪ These results are from repeated elicitations of a foot withdrawal response in cats by mildly aversive stimulation

Answer 44

▪ Without the sensitization process, habituation is not learning – it is merely a mechanism that reduces responsiveness regardless of whether the stimulus is worth responding to Dual process theory ▪ Sensitization and habituation are two process that work together to produce learning – both are learning processes

Answer 45

This reflex is mediated by a simple neural circuit involving a population of about 20-30 SNs, some interneurons and about 10 motorneurons A brief tickle of the siphon elicits a rapid gill withdrawal. A few tickles repeated with an ISI of no more than about 30 to 40 seconds will quickly habituate the response.

Answer 46

The effectiveness (strength) of the synaptic connections shown hatched ▪ The synaptic terminals of the SNs release less transmitter substance in response to the arrival of action potentials - so less excitatory effect on INs and MNs ▪ This change only happens if the effects of the previous release of transmitter are present when the next release occurs (a sort of memory). Explains why short ISI needed

Answer 47

If sessions of repeated ticklings with short ISIs are repeated at intervals of a day or so, a long term effect is produced that can last weeks or months. The changes that occur in long term habituation involve structural changes at the cellular level. ▪ These changes include a reduced number of connections between one neuron and the next. Regardless of the changes to synaptic connectivity that take place, habituation effects in elementary reflex circuits are due to a reduction of the efficacy (strength) of some synaptic connections within the circuitry

Answer 48

Homosynaptic depression

Answer 49

▪ The presynaptic connections cause increased neurotransmitter release at the ringed synapses ▪ This increases the strength of the connections, which leads to an increase in the ‘strength’ (vigour) of the withdrawal response ▪ The effect is the exact opposite of that produced by short term habituation

Answer 50

▪ Long term effects can be produced by a series of sessions of shock delivery over a few days Long term effects are associated with structural changes in the synaptic connections. ▪ These changes include an increased number of connections between one neuron and the next

Answer 51

False - ‘Dishabituation’ only reverses the short term habituation changes

Answer 52

(1) The reduction is only present if the person continues to stand up. If they sit or lie down, the response amplitude is back to normal (2) In a sitting or lying person, 4 or 5 stretches of the calf muscles produces no change in reflex response amplitude (3) The reduction cannot be dishabituated by presenting aversive stimuli

Answer 53

True - Pavlovian learning can lead to the acquisition of new reflexes (and so refutes the claim that all reflexes are innate and not acquired as a result of experience)

Answer 54

US elicits UR US and CR combined elicits UR (conditioning) CS elicits CR

Answer 55

1) The CR is the same as the UR. 2) Pairing the US and CS is a necessary condition for acquiring a CR – i.e., they must occur together if acquisition is to occur. 3) Pairing the US and CS is a sufficient condition for acquiring a CR – i.e., if they occur together, then a CR will (eventually) be acquired. Standard view of Pavlovian learning 4) The US-UR reflex is a pre-existing, innate reflex; the CSCR reflex is an acquired reflex; so it’s all about reflexes

Answer 56

▪ Consider conditioning a rat using foot shock as the US and a tone or light as the CS ▪ Electric shock (US) delivered to the feet of a rat (through the cage floor) reflexively elicits a jump (withdrawal reflex response = UR ▪ Before training the tone alone (CS) only elicits an orienting response ▪ During training the CS and US are paired CR ≡ UR? ▪ Rats learn to respond to the CS, but the CR is not a withdrawal response – the rat does not jump or lift its feet from the floor when the CS is presented ▪ After training, the rat responds to the CS by ‘freezing’ ▪ The CR is a different kind of response – its result is quite different to that of the UR

Answer 57

▪ Rat is injected with insulin (US) ▪ UR = hypoglycemia (a decrease in blood glucose level) ▪ CS = stimuli associated with being injected CR ≡ UR? ▪ Training: injection repeated a number of times at suitable intervals (sufficiently long for recovery) ▪ The result is that the rat acquires a CR (revealed when the injection contains only saline) ▪ The CR is the opposite of the UR ▪ CR = hyperglycemia (increase in blood glucose level)

Answer 58

If pairing is necessary, then there can be no situations in which a CR is acquired when the CS and US are not paired ▪ Consider a conditioning procedure in which the US is only presented if the CS is not presented (no pairing) ▪ Are there any such situations? ▪ If the CS (e.g., tone) is presented, then no US (e.g., shock) is presented. The US & CS are both presented, but not paired ▪ If CS-US pairing is necessary, predict that no CRs will be acquired when they are not paired. Is this what happens? ▪ No - CRs can be acquired ▪ When US is aversive, CR = approach to the location of the CS ▪ When the US is appetitive (desirable/pleasurable ), CR = avoidance of the location of the CS ▪ The unpaired procedure (if CS then no US) is called an inhibitory conditioning procedure

Answer 59

Simultaneous conditioning Trace conditioning Delay conditioning Backward conditioning The most effective for acquisition of CRs simultaneous and delay conditioning.

Answer 60

▪ The eye blink conditioning results are typical Does the type of pairing matter? ▪ It matters how the CS and US are paired: backwards and simultaneous conditioning are ineffective as are positive delays (forward conditioning) that are too short or too long ▪ It is true that conditioning is less effective when the interval is longer, but only for ‘forward’ procedures (and very short intervals are ineffective) ▪ If pairing is sufficient, then the only thing that would matter would be the time between stimuli – the longer the delay or trace interval, the less effective the procedure ▪ Similar results are obtained using the trace conditioning procedure, but trace intervals more than 2 or 3 seconds are ineffective in eye blink conditioning

Answer 61

▪ What do these results tell us? ▪ First: simultaneous conditioning is ineffective (0% CRs acquired) ▪ Second: short delays are ineffective in both backward and forward directions ▪ NB: backward conditioning has been found to be ineffective for any length of delay ▪ Positive (forward) delays are most effective between 200 – 400 ms, shorter and longer delays are less effective ▪ NB: positive delays of more than about 5 seconds are ineffective

Answer 62

For examples of debunking myths of Pavlovian learning

Answer 63

In Pavlovian conditioning, the anticipated/predicted thing is called the US and the preceding thing is called the CS (as both are stimuli)

Answer 64

Rabbit in experimental conditions cannot move around had an unchanging view with very little in it. The only changing external stimuli is exposed to the air puff US and tone CS. Acquisition is not a quick process it is a slow process needing over 200 trials for rabbits to be reliably blinking (>50%) in response to the CS.

Answer 65

1. Only stimuli that occur before significant events/stimuli that are relevant 2. Stimuli that occur both before and after are not relevant 3. Only stimuli that occur within the right period of time are relevant (not too soon and not to long before) 4. Familiar stimuli are not relevant

Answer 66

CS-US belongingness

Answer 67

▪ Seligman recounted a tale about how he once ate this dish in a restaurant ▪ Several hours after eating it, he fell very ill ▪ Some time later he had sauce béarnaise again, but found that he couldn’t bear the taste and smell of it, just thinking about it made him nauseous ▪ He had acquired an aversion to a once loved food and reports that it was more than 10 years until he could eat it again

Answer 68

▪ It is unusual because the CS-US delay can be very long (up to 6 or 7 hours is most effective, but delays of as much as 24 hours may produce some aversion) and just one experience may be sufficient ▪ The learning process is easily ‘fooled’ – if you fall sick after having eaten a novel/strongly/unusually flavoured food/ drink you are likely to develop an aversion to it, regardless of the cause of your illness ▪ Seligman’s illness was not caused by the sauce (or anything else he ate) but by gastric flu

Answer 69

Would receive a dose of x-rays sufficient to cause radiation sickness (US) and a audio-visual stimulus bright noisy water and tasty water (CS) . Group 1 acquired an aversion to the tasty water but not the bright-noisy water - rats still thirsty were tested with either the audio-visual CS alone or the flavour CS alone the more averse the less they licked.

Answer 70

Would receive a foot shock (US) and audio-visual stimulus bright noisy water and taste stimulus tasty water. Group 2 acquired an aversion to the bright noisy water, but not the tasty water Taste/smell aversions The flavour CS ‘belongs with’ the illness inducing US the audio-visual CS ‘belongs with’ the foot shock US.

Answer 71

A cancer patient enters hospital for chemotherapy treatment and they eat a meal at lunchtime A few hours later they receive their treatment and subsequently feel sick and nausesous They may develop an aversion to some of the foods they ate at lunchtime Over repeated chemotherapy sessions, the acquired aversions may extend to many common foods (depending on what they’ve eaten in the previous meal) It is established that these acquired aversions can contribute to the severe loss of appetite that is a common side effect of chemotherapy (and radiotherapy) Solution: include as part of the last meal/snack before therapy a strongly flavoured/smelling or novel food/drink therefore preventing aversions to basic food

Answer 72

Antcipatory Nausea and Vomiting (ANV) ANV refers to nausea and vomiting that occurs before any chemotherapeutic agent has been administered to the patient It has been reported that about 30% of cancer patients receiving chemotherapy experience ANV by their fourth session A Pavlovian conditioning account of ANV is fairly clear and is known to contribute to the phenomenon CSs - being in the hospital and adminstration of the drug CRs - nausea and vomitting USs - the chemotherapeutic agents URs: nausea and vomiting

Answer 73

Drug tolerance refers to the finding that over repeated administrations, the effects of a drug get progressively smaller

Answer 74

CR = hyperalgesia (increased sensitivity to pain) UR = decrease in sensitivity to pain A compensatory response as it counteracts the analgesic effects of the drug and so acts to maintain pain sensitivity As the CR develops (increases) over repeated administrations of morphine, so tolerance to the drug develops Larger and larger doses are needed to produce the same effect Thus, tolerance to a drug like morphine is in part due to the action of compensatory responses (CRs) elicited by the stimuli (CSs) that accompany drug taking Thus called the behavioural theory of drug tolerence

Answer 75

If the CSs are not present (new situation), the CR will be reduced or absent so the effect of a dose will be greater This can lead to OVERDOSE A person used to taking a drug in certain locations develops a tolerance partly due to the CR evoked by a situational stimuli (CSs) To get high they need a large dose to overcome the effect of the CR If they take the same dose in unfamiliar circumstances, they may be unable to cope (overdose) since the CR is not elicited

Answer 76

Cyclophosphamide was used in a study of conditional taste/smell aversions The experiments (on rats) involved drinking flavoured water (taste CS) and being dosed with cyclophosphamide (US) The animals would quickly acquire an aversion to the flavoured water, but by the end of the experiments many became seriously ill and some died The size and number of cyclophosphamide doses were chosen to be safe so what could have caused their death? It was found that repeated doses of cyclophasmide led to learned immunosuppression effect (the rats immune system was suppressed for a period in response to drinking the flavoured water)

Answer 77

Avoidance of side effects: drugs with side-effects need only be used until the learned effect is established Cost savings Studies show that the strategy could work but it has yet to be implemented

Answer 78

Experiments with animals have shown that if such drugs are used as a US, it is possible to produce conditional immune enhancement using similar procedures to those that produce conditional immunosuppression It has been proposed that conditional immune suppression and enhancement contribute to some instances of the placebo effect Indeed the CR in these cases is a placebo effect (according to the definition we will develop) When the patient is presented with the CS alone (e.g the sight of the pill, the prick of a needle - a placebo) there is an actual physical effect (the immune response) that can be beneficial to health

Answer 79

An objectively measurable effect on the body’s function or condition (e.g patient recovers from a condition more quickly, heals faste etc) A psychological effect that is not accompanied by any measurable improvement in function or condition (e.g person reports feeling better or having less pain, but there is no measurable change in their physical condition)

Answer 80

Thus a person’s history of medication and treatment can act like a Pavlovian conditioning procedure: treatment/medicine (US) is presented in a paired fashion with a variety of other contextual stimuli (CSs) e.g the therapist, a pill, a syringe It is not fully understood what role CRs play in the placebo effects that have been observed in clinical contexts (usually as part of clinical trials and other research) In people the problem is that there are always going to be belief and expectancy effects in addition to CRs Research investigating the relationship between mind, brain and immune function is called psychoneuroimmunology