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NHB MVST 1b > Motivation > Flashcards

Motivation Flashcards

1
Q

What drives motivation?

A

Motivation can be driven by internal factors (sensations) and external factors (incentives). These can interact.

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2
Q

What are the two phases of motivated behaviour?

A

Two phases of motivated behaviour: consummatory, where the animal interacts with the goal object (e.g. sexual reflexes, ingestive responses), and appetitive, where the animal performs

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3
Q

Describe the decerebrate precipitation experiment

A

Cut above midbrain to cut off influence of forebrain and just leave the brainstem. No longer able to do appetitive behaviours (i.e. seek out water, or a sexual partner), but can do consummatory behaviours (swallowing liquid water if placed in the mouth) if they are simple somatomotor reflex responses. Shows that brainstem controls the consummatory reflexes, but that the coordination of these and of appetitive behaviours is a forebrain activity.

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4
Q

Describe the stimulation and lesions of hypothalamic neurons experiment

A

Led to activation and loss of motivated behaviours respectively e.g. sex, feeding and drinking

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5
Q

What are the inputs to the hypothalamus?

A
  • Neural inputs from brainstem:
  • Non somatotopic somatic afferents important in neuroendocrine reflexes e.g. milk ejection and stereotypic behaviour (sex)
  • Visceral afferents from NST and reticular formation conveying gustatory and olfactory information
  • Neural inputs from forebrain:
  • Afferents from amygdala and orbitofrontal cortex: carries information about the motivational significance of external stimuli
  • Neurons directly responsive to hormones:
  • Hypothalamus has neurons with steroid hormone receptors
  • Neurons directly sensitive to temperature and osmolarity:
  • Preoptic area = changes in temperature
  • OVLT = osmoreceptors (circumventricular organ)
  • Hypothalamic capillaries fenestrated so large molecules from blood can move in, so can respond to changes in chemical composition of the blood
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6
Q

What are the outputs of the hypothalamus?

A
  • Endocrine responses via pituitary:
  • Directly via neural signal to posterior pituitary (parvocellular neurosecretory cells  general circulation)
  • Indirectly by secreting hormones into local portal plexus within the median eminence)  blood vessels of anterior pituitary  anterior pituitary hormone synthesis and release into general circulation  reproduction, maternal care etc
  • Behavioural responses:
  • Can control simple stereotyped movements e.g. biting, shivering, gnawing, drinking, mounting via brainstem motor circuits
  • Autonomic responses via descending projections:
  • Can control both neutrally and humorally
  • Reciprocal connections between NST and amygdala and paraventricular nucleus of the hypothalamus
  • NST: nucleus of the solitary tract. Acts upon other brainstem nuclei and spinal cord neurons to control preganglionic autonomic neurons
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7
Q

Define motivation

A

The higher order control that is responsible for the activation and direction of behaviour.

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8
Q

Define homeostasis

A

The use of negative feedback systems to maintain a constant internal milieu

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9
Q

Which part of the hypothalamus contains temperature sensitive neurons?

A

Preoptic area

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10
Q

How do we know that the preoptic area controls thermoregulation?

A
  1. Cooling and warming it elicits thermoregulatory behaviour
  2. Lesions impair thermoregulatory behaviour in response to changes in ambient temperature (however lesioned rats will still learn to press a lever for hot or cool air)
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11
Q

Discuss the Rolls experiment

A

Firing rate of cells within monkey hypothalamus that are responsive to food dependent upon the motivational state of the animal. There was more rejection of glucose when the rat had previously ingested more glucose.

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12
Q

Which hypothalamic area acts as a feeding centre?

A

Lateral hypothalamus

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13
Q

Discuss lesion and stimulation studies of the lateral hypothalamus

A

Lesions produced profound aphagia and stimulation induced eating in sated rats
When just used excitotoxins residual defects remained in dehydration (mimic by injecting NaCl) and starvation (2-DG treatment - glucose that has been altered so it can’t undergo glycolysis, but does compete for uptake to tissues, so tissues become glucose and energy deprived)

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14
Q

Which hypothalamic area is sensitive to satiety signals?

A

Ventromedial hypothalamus

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15
Q

Discuss lesions of the ventromedial hypothalamus

A

Led to overeating and obesity, in female rats abolished sexual behaviours including lordosis ands oslicitation

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16
Q

What was the problem with doing lesion studies of the lateral hypothalamus? How did they fix this?

A

Also destroyed fibres passing throught he LH including monoamine axons within the mfb medial forebrain bundle
Used excitotoxins that bind to the GluR, so only kill cell bodies, not axons

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17
Q

Which part of the hypothalamus detects steroid concentrations?

A

Medial preoptic area

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18
Q

Discuss lesion studies of the medial preoptic area

A

Resulted in loss of copulatory behaviour in the presence of a female rat, but the male rat would still show intense excitement in the presence of the female rat in hear –> shows it contributes, but not exclusively, to sexual control

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19
Q

What are the satiety mechanisms?

A

Short term: feedback from tasting, smelling, swallowing food
Distension of stomach
CCK released by the duodenum –> receptors in pylorus –> vagal to brainstem –> reduce feeding
Long term:
Leptin secreted by well nourished adipose tissue increases metabolic rate and decreases food intake. Modulates brain’s sensitivity to CCK

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20
Q

What is wrong in the Ob mouse?

A

No leptin - removes the inhibitory break

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21
Q

What stimulates eating?

A

Environmental cues: sight, smell, taste, conditioned stimuli
Physiological cues: declining levels of blood glucose and fatty acids

Neuropeptides: Leptin –> inhibit Neuropeoptide Y arcuate nucleus–> lateral hypothalamus –> MCH, orexin –> stimulate eating, reduce metabolic rate

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22
Q

What does MCH stand for?

A

Melanin concentrating hormone

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23
Q

What does the paraventricular nucleus do?

A

Acts via brainstem nuclei to reduce insulin secretion, decrease breakdown of fatty acids, decrease body temperature

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24
Q

Define the role of NPY

A

Acts at different hypothalamic sites to integrate a variety of physiological mechansims that promote feeding and preserve the body’s energy supplies

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25
What abolishes male sexual behaviour?
Medial preoptic area lesion (androgen receptors) abolishes consummatory Basolateral amygdala abolishes appetitive Loss of steroids by castration abolishes both
26
What abolishes female sexual behaviour?
Ventromedial hypothalamic lesion (oestradiol and oestrogen inducible progesterone receptors) Ovariectomy
27
Discuss the Everitt study with respect to the medial preoptic area
Looked at motivation of a male rat to learn to press a lever to obtain a conditioned stimulus that had previously bene paired with a sexually active female. After pressed lever a certain number of times, rat got the female. Excitotoxic lesions of medial preoptic area inhibited copulatory behaviour in the rat, but didn’t affect the rat’s motivation to lever press to access the female. Castration did affect lever pressing and copulatory behaviour, showed that sex hormones essential more generally in sexually motivated behaviour.
28
What aspect of motivation survives hypothalamic lesions?
Incentive motivational responses: appetitive behavioural acts to obtain food, a sexual partner, or warmth.
29
What is the aim of the hypothalamus?
To integrate reflexive and consummatory behaviours from the primary needs of the organism: food, shelter, sexual and social interactions. Signals biological priorities.
30
Where is the hypothalamus?
Rostral to it: optic chiasm Causal to it: mammillary bodies It lies below and rostral to the thalamus
31
Where is the amygdala?
Anterior temporal lobe | Rostral to hippocampus in the end wall of the inferior horn of the lateral ventricle. Adjacent to olfactory cortex
32
How do you tell if you're looking at the rostral or caudal amygdala?
Size of caudate, anterior commissure, presence of thalamus
33
What is Urbach-Weithe disease?
A rare genetic disorder causing bilateral calcification of the amygdala. Can also damage uncus.
34
Where is the caudate widest?
Rostrally
35
What are the 3 basic subdivisions of the amydala?
1. Corticomedial division: olfactory input, efferents to ventromedial hypothalamus 2. Central nucleus: controls autonomic nervous system, endocrine system, simple motor reflexes. Afferents NTS, efferents to hypothalamus and brainstem. 3. Basolateral amygdala: afferent higher order sensory, efferent regions involved in planning and action - prefrontal cortex and ventral striatum. (assesses external motivational cues for appetitive, but not consummatory behaviour)
36
What are pheromones?
Secretions from the urogenital tract, act via corticomedial division of amygdala, elicit social and sexual behaviour. Important in non-human animals.
37
What are the two efferent pathways of the amygdala?
1. Ventral amygdalofugal pathway (diffuse pathway directly across temporal stem). From corticomedial nucleus to ventromedial nucleus hypothalamus 2. Stria terminalis (fibre bundle running around lateral ventricle in groove between caudate tail and thalamus). From central nucleus and basolateral nucleus to medial dorsal nucleus of thalamus, hypoth, basal forebrain, septal nuclei, nucleus accumbens. Modulate PAG
38
Medial to lateral: globus pallidus, caudate, putamen
Caudate, globus pallidus, putamen
39
Discuss the Everitt experiment wrt to the amygdala
Basolateral amygdala lesions inhibit lever pressing, but the rats can still mount and intromit (consummatory response still intact, appetitive lost)
40
What does the amygdala do?
Appetitive behaviour elicited by cues (conditioned stimuli) in the environment predictive of primary rewards Learning about the emotional significance of stimuli and subsequent expression of these emotions
41
How does the amygdala control voluntary action?
1. Output to ventral striatum --> nucleus accumbens and ventral regions of caudate and putamen --> motor systems of basal ganglia 2. Ventral striatum specific dopaminergic input from A10 group of dopamine neurons in the VTA ventral tegmental area (adjacent to A9 substantia nigra)
42
What are the ascending activating system chemicals?
Dopamine Noradrenaline Serotonin Acetylcholine
43
What is the striatum?
The caudate-putamen and nucleus accumbens
44
What type of projections run in the medial forebrain bundle and where are they going?
Dopaminergic to striatum | From periamygdala, olfactory, septal nuclei, ventral tegmental area
45
How is Parkinson's related to motivational responses?
Lose dopaminergic projections | Lose consummatory ingestive responses (so that is lateral hypothalamus)
46
What is the role of dopamine in motivation?
Activation and energisation of behaviour, especially in preparation for action
47
What is the mesolimbic dopaminergic pathway?
DA projections to ventral striatum, including nucleus accumbens
48
What projects to the nucleus accumbens?
``` Mesolimbic dopaminergic pathway (DA) Orexin neurons (also send innervation to the dopaminergic pathway) ```
49
When is orexin released?
Hunger state
50
What is the brainstem reticular core connected to caudally and rostrally?
Caudally intermediate gray of spinal cord | Lateral hypothalamus and subthalamic regions rostrally
51
What is the brainstem reticular formation made of?
Loosely aggregated cells of different types and sizes intermingled with fibres of different orientations
52
What does the EEG do?
Electroencephalogram Measures fluctuations in electrical activity in the brain from surface scalp electrodes Represents summed activity of many cortical cells that are probably synchronised in part by thalamic activity
53
What makes up most of the activity seen by the EEG?
IPSPs and EPSPs
54
When can the EEG detect APs?
Epileptic seizures
55
What are the functions of the reticular formation?
1. Integration of basic, stereotyped patterns of responding: - Pattern generation for posture and locomotion, swallowing, chewing, vomiting, sneezing, eye movements - Regulation of the respiratory cycle and cardiovascular control 2. Regulation of brain activity levels - Ascending activating system - Sleep and wakefulness
56
What does electrical stimulation of the reticular formation lead to?
Widespread cortical activation so desynchronisation of the EEG
57
Who is Hebb?
Developed notion of reticular neurons subserving state that optimised processing of sensory stimuli in the cerebral cortex: attentional function.
58
What did Yerkes and Dodson do?
Linked arousal to concepts like drive and motivation May be an optimal level of arousal for optimal behaviour as in lower for a relatively simple task optimal, but higher for a difficult mathematical problem
59
What is the isodendritic core?
3 types of neurons in the brain, isodendritic most of them, if you remove the isodendritic neurons that mediate sensory and motor function left with isodendritic core (basically the reticular formation)
60
How does the reticular formation project to the cortex?
Direct: medial forebrain bundle through lateral hypothalamus Indirect: via intralaminar nuclei of thalamus --> cortex and striatum
61
Where are histaminergic neurons?
Posterior hypothalamus
62
Which other group of cholinergic neurons are included in the concept of the isodendritic core?
Basal forebrain cholinergic neurons
63
Where does the dopaminergic population of neurons project to and from?
Substantia nigra --> striatum (ventral = nucleus accumbens, dorsal = caudate and putamen)
64
Where does the NA population of neurons project to and from?
Locus coerulus --> Frontal association, primary somatosensory, primary visual
65
Where does the serotonin population project to and from?
Raphe --> primary visual
66
Where does the ACh population project to and from?
Basal forebrain
67
What is the function of the noradrenergic ascending pathway?
Attention and orienting
68
What is the function of the noradrenergic ascending pathway?
Attention and orienting General arousal function Maybe particularly important under times of stress
69
What is the function of the serotonin system?
Can affect behavioural inhibition particularly in aversive stiuations
70
What is the function of the serotonin system?
Can affect behavioural inhibition particularly in aversive situations
71
Which neurotransmitter does Prozac affect?
5-HT
72
What is the function of the acetylcholine ascending system?
Learning and memory
73
What is affected in Alzheimer's disease?
Forebrain acetylcholine system | Disorders of learning and memory
74
Which cholinergic neuron groups are involved in what?
Forebrain cholinergic = learning and memory | Pedunculopontine in brainstem = wakefulness
75
Define sleep
The normal suspension of consciousness and electrophysiology by specific brain wave activity
76
What happens to sleep cycles when you remove light and dark?
Sleep-wake cycle either lengthens or shortens by half an hour
77
During the waking day, what are the 2 characteristic EEG patterns?
1. Beta activity = High frequency (15-60Hz) low amplitude, eyes are open, signals active cortex 2. Alpha activity = lower freq (8-13Hz) associated with quiet waking states
78
What are the stages of sleep?
1. Theta waves. Drowsy period, decreasing EEG freq (4-8Hz and increasing amplitude) 2. Spindles. Light sleep - further decreases in frequency and increases in amplitude, and intermittent high frequency spike clusters 3. Moderate to deep sleep 4. Delta waves: deep sleep, lowest frequencies and highest amplitudes
79
What are the stages of non-REM sleep?
1. Theta waves. Drowsy period, decreasing EEG freq (4-8Hz and increasing amplitude) 2. Spindles. Light sleep - further decreases in frequency and increases in amplitude, and intermittent high frequency spike clusters 3. Moderate to deep sleep 4. Delta waves: deep sleep, lowest frequencies and highest amplitudes
80
Summarise how the EEG progressively changes as you fall into a deeper sleep
Lower frequency, higher amplitude
81
What is REM sleep?
Rapid eye movement | EEG recordings look like the awake state
82
What happens physiologically in REM and non-REM sleep?
REM: increased BP, HR, metabolic rate, rapid rolling eye movements, paralysis of large muscles Non-REM: decreases in muscle tone, HR, breathing, BP and metabolic rate
83
Which structures are more active during REM sleep than the awake state?
Extra-striate cortex and certain limbic structures
84
Which structures are more and less active during REM sleep than the awake state?
More: Extra-striate cortex and certain limbic structures Less: Prefrontal cortex
85
What is the function of sleep?
Restoration of bodily and mental functions, brain development in children, memory consolidation
86
What controls the sleep-wake cycle?
Brainstem modulatory NT systems | Thalamus
87
Stimulating what causes a state of wakefulness, and stimulating what stimulates slow wave sleep?
``` Wake = pedunculopontine neurons Sleep = thalamus (stim with low freq pulses) ```
88
How does ACh and NA change cell firing properties in the cortex and thalamus?
From intrinsic burst-firing to single spiking mode (may underly transition rom non-REM sleep to the waking state)
89
Which NTs are active in wakefulness and inactive in non-REM sleep?
NA ACh 5-HT
90
Which NTs are changed in REM sleep?
ACh increased, 5-HT and NA even further decreased
91
What is the difference between sleep and wakefulness?
Thalamic-cortical synchronicity If they are synchronised (intrinsic burst firing) the cortex is disconnected from the outside world - maximal in delta sleep If they are single spike firing - tonically active state
92
What changes at the end of REM sleep?
Firing rates of serotonin and NA neurons increase again
93
Which part of the brain switches between the awake and sleeping state?
Ventrolateral preoptic area of hypothalamus VLPA
94
How does the flip-flop model work?
Inhibits ascending arousal system Ascending arousal system inhibits VLPA Provides sharp and clearly defined boundaries between wakefulness and sleep
95
Discuss lesions and stimulation of the VLPA
Reduce sleep time by more than 50%. Circadian pattern normal, but tend to wake up more during the sleep cycle, and also fall asleep more during the wake cycle too. Can cause total insomnia and death in rats. Stimulation causes drowsiness
96
What tips the balance between the awake and asleep phases of the flip-flop model?
Unsure | Many other neurochemical systems in the hypothalamus feed in: orexin excitatory, MCH inhibitory
97
Define narcolepsy
Sleep disorder characterised by frequent REM sleep attacks during the day and possible cataplexy (temporary loss of muscle control)
98
What can cause narcolepsy?
Mutation of orexin receptor 2 gene
99
Where are orexin neurons found?
In cells of the tuberal region of the hypothalamus (lateral hypothalamus)
100
What can activate orexin neurons in feeding?
Hunger signals from the arcuate NPY neurons
101
What links feeding to sleep-wake?
1. Orexin: higher conc when hungry, and keeps flipflop towards being awake (VLPA) 2. Nocturnal animals can become diurnal if the only available food source can be found in the day
102
What does the suprachiasmatic nucleus do?
Paired Biological circadian clock In the absence of light-dark signals runs freely with a period slightly below or above 24 hours Individual cells are oscillators that are coupled to make a pacemaker Also rhythmicity of physiological functions especially via connection to dorsomedial nucleus of hypothalamus, midline thalamus, bed nucleus of stria terminalis
103
How does the SCN receive light-dark information?
Directly from retina via retinohypothalamic tract - melanopsin (light sensitive pigment) in a subset of retinal ganglion cells is particularly sensitive to blue wavelengthlight. Sends their axons to the SCN.
104
Where does the suprachiasmatic nucleus lie?
Anterior hypothalamus | Above optic chiasm on each side of the third ventricle
105
How does the SCN act as regulator of circadian rhythm?
Connected via dorsomedial nucleus to VLPA

NHB MVST 1b (11 decks)

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