Motivation Flashcards
What is motivation responsible for
activation and direction of behaviour
What is the homeostatic school of thought on motivation
use eating as an example
the motivation or drive to feed is a consequence
of a deficit in nutrients that build up across time, after the last meal. Alleviation of that deficit state, by taking in
nutrients, acts to reduce drive and ultimately to stop feeding.
What is the problem with the idea that motivation is purely homeostatic
not all behaviours stem from an underlying deficit state.
So sexual behaviour, aggression and many motivated behaviours in humans, e.g. running in a race, do not appear to be alleviating some deficit state.
In these other examples it is more usual to talk about ‘incentive motivation’ – the
pull of behaviour towards goals/incentives, e.g. a gold medal at the Olympics, rather than a push (or drive) from within.
Describe the ‘internal’ and ‘external’ feelings involved with eating a cake when you are full
the smell and ‘look’ of the chocolate cake, along with our past experience with it, over-rides any internally driven satiety signals.
Is motivation thought to be based on internal or external factors
generally accepted that there can be both internal factors (sensations) and external factors (incentives) that motivate behaviour and these factors can interact. Thus, food can seem much more desirable and attractive when we are hungry than when we are ‘full’.
What are the 2 phases of motivated behaviour
1) consummatory, when the animal interacts with the
goal object e.g. ingestive responses and sexual reflexes
2) appetitive, when the animal performs voluntary
behaviour to seek out the goal, e.g. food searching, lever pressing for warm air.
What is a rat decerebrate preparation
if a cut is made above the midbrain of a rat to cut off the influence of the forebrain
How does appetitive and consummative behaviours change in a rat decerebrate preparation
animal is no longer able to seek out and consume food/water or a sexual partner, but is
able to interact with the goal object if the goal is placed appropriately to allow the activation of somato-motor
reflexes, e.g. swallowing liquid food/water if placed in the mouth. Thus, while the animal shows no appetitive, goal
directed behaviours, it can, nonetheless, perform very simple reflexive responses
Where is the coordination of consummatory reflex behaviours and appetitive behaviours found in the brain
neural activity in the forebrain,
including the hypothalamus and amygdala
What borders the hypothalamus rostrally and caudally
rostrally by the optic chiasm and
caudally by the mammillary bodies.
How can the hypothalamus be divided
grossly into lateral, medial and periventricular regions as well as anterior, middle and posterior regions.
What was the hypothalamus originally identified as ?
Why was this thought to be the case?
as a structure that could act as a drive centre.
Stimulation and lesions of neurons within the hypothalamus led, respectively, to the activation and loss of motivated behaviours such as sex, feeding and drinking.
Describe the neural inputs to the hypothalamus from the brainstem
(a) somatic afferents, n.b. not somatotopic, no feature detection important in neuroendocrine reflexes e.g. milk ejection (maternal care) and stereotypic behaviour (sex)
(b) visceral afferents from nucleus of the solitary tract (NST) and reticular formation conveying gustatory and olfactory information
Describe the neural inputs from the forebrain to the hypothalamus
Afferents from the amygdala (and orbitofrontal cortex) are carrying information about the motivational significance of external stimuli.
Is the hypothalamus directly responsive to hormones
yes
Many regions of the hypothalamus are rich in steroid hormone receptors.
How is the hypothalamus directly sensitive to temperature and osmolarity
Cells in the preoptic area are sensitive to changes in temperature while osmoreceptors are found in the OVLT, a circumventricular organ.
hypothalamus is well placed to respond to changes in the chemical composition of the blood as many of the hypothalamic capillaries are ‘fenestrated’, like peripheral capillaries and are therefore open to the entry of large molecules from blood to brain.
What are the different kinds of input to the hypothalamus (4)
neural inputs from the brainstem and forebrain
neurons directly responsive to hormones, temperature and osmolarity
What are the 3 ways types of output from the hypothalamus
endocrine via the pituitary
behavioural responses
autonomic responses via the descending projections
How can endocrine responses from the hypothalamus via the pituitary occur (2)
r (i) directly via a neural signal to the posterior pituitary resulting in the secretion of neuroendocrine
products into the general circulation
(ii) indirectly by secreting hormones into the local portal plexus (within the median eminence) which drains into the
blood vessels of the anterior pituitary. These in turn control the synthesis and release of anterior pituitary hormones into the general circulation involved in the control of reproduction, maternal care, etc.
What kind of behavioural responses can the hypothalamus control
can control simple stereotyped movements e.g. biting, shivering, gnawing, drinking and sexual mounting via reflex motor circuits in the brainstem
How can the hypothalamus affect the ANS
What is the other ANS coordinating centre in the brain? How does this work?
both neurally and humorally
NTS in the brainstem
acts upon other brainstem nuclei and neurons in the spinal cord to control preganglionic autonomic neurons
What ANS coordinating centres do elaborate homeostatic adjustments involve?
reciprocal connections between the NST and higher centres
including the amygdala and paraventricular nucleus of the
hypothalamus.
Where are the temperature sensitive areas in hypothalamus
preoptic area
What happens if you change the temperature of the preoptic area
elicits thermoregulatory behaviour, including reflexive shivering, panting and grooming as well as learning to perform an action to cause a brief lowering of hypothalamic temperature
What do lesions of the preoptic region result in
impairs thermoregulatory behaviour in
response to changes in ambient temperature
Cooling or warming of the preoptic area elicits thermoregulatory behaviour, including reflexive shivering, panting and grooming as well as learning to perform an action to cause a brief lowering of hypothalamic temperature Conversely, lesions of the preoptic region impair thermoregulatory behaviour in response to changes in ambient temperature. What does this suggest
changes in the internal environment can be sensed by the hypothalamus and, via negative feedback loops, the appropriate behaviours can be generated to restore the balance
What happens to a rat with a preoptic lesion if the temperature changes
don’t shiver or pant but can still learn to press a lever for hot or cool air and thus can achieve thermal regulation!
Which area of the hypothalamus increases activity upon presentation of food?
What is this activity dependent upon
lateral hypothalamus
the motivational state of the animal. They do
not fire if the monkey is satiated
the hypothalamus is in a position to match behaviour to current needs
What did early lesion studies suggest about the lateral hypothalamus
What was the evidence
Which area is suggested to serve an opposite function? What was a problem with this study?
it was a feeding centre
Electrolytic lesions of the LH produced profound aphagia and stimulation of the same region induced eating in sated rats
lesions of the ventromedial hypothalamus (VMH) caused over-eating and obesity
the overeating seen following VMH lesions was found to be due, in part, to disruption of axons between the arcuate nucleus and other hypothalamic and brainstem nuclei.
What are the LH and VMH sensitive to according to early lesion studies
LH- hunger
VMH - satiety
What was the problem with the early lesion studies of the LH
only looked at very selective
behaviours and LH lesions actually resulted in the loss of
MOST motivated behaviours, not just eating. Subsequently it
became clear that these electrolytic lesions not only destroyed
intrinsic cell bodies within the LH but also fibres passing
through the LH which included monoamine axons within the
medial forebrain bundle (mfb)
How does selective lesions of LH neurons differ to the original results which didn’t spare mfb fibres
more restricted feeding deficits were seen. There is considerable recovery of function across time but there remain residual deficits in the ability to respond appropriately to
homeostatic/physiological challenges that mimic dehydration (injection of NaCl) and starvation (2-DG treatment).
What is the mPOA
What receptors are abundant here? What can they detect
medial preoptic area
steriod receptors to detect changes in circulating testosterone and oestrogen/progesterone levels
What happened to male rats with mPOA lesions
loss of copulatory behaviour in the presence of a female rat BUT the male rat would still show intense excitement in the presence of a female rat in heat.
What are the environmental cues that initiate feeding
include the sight, smell and taste of food as well as conditioned stimuli associated with food such as McDonalds and Costa Coffee signs.
What are some physiological cues that initiate feeding
declining levels of blood glucose and fatty acids, i.e. gluco- and lipo-privation.
What are the short term satiety mechanisms
feedback from tasting, smelling and swallowing food as well as distension of the stomach following ingestion
Humoral factors e.g. CCK released by the duodenum when it receives food rich in fats acts on receptors in the pylorus that are transmitted to brainstem, via the vagus, to reduce feeding.
What are long term satiety mechanisms
signals arising from nutrient reservoirs can affect food intake.
eg Leptin, a peptide secreted by well nourished adipose tissue increases metabolic rate and decreases food intake. It also increases brain’s sensitivity to short term satiety signals such as CCK
What are 2 neuropeptides are in involved in stimulating eating
melanin concentrating hormone (MCH) and orexin in the LH
What are orexin and MCH activated by
NPY from neurons in the arcuate nucleus
What NPY neurons affected by
contain leptin receptors, that when stimulated act to inhibit NPY neuronal activity.
What happens to NPY neurons when we become hungry
leptin levels decrease and this releases NPY neurons in the arcuate nucleus from their inhibition by leptin. Also, other cues, such as the release of ghrelin from the stomach when it empties, activate NPY neurons directly. The resulting increase in NPY release in the LH, causes voracious eating and, in the paraventricular nucleus (PVN), a decrease in metabolic rate and a decrease in insulin
How does NPY integrate a variety of physiological mechanisms that promote feeding and preserve the body’s energy supplies
increase in NPY release in the LH, causes voracious eating and, in the paraventricular nucleus (PVN), a decrease in metabolic rate and a decrease in insulin
What happens to NPY when the body becomes well nourished
leptin levels increase, causing a reduction in NPY activity and as a consequence, a reduction in LH orexin and MCH neuronal activity.
The latter results in
decreased feeding and, via a loss of NPY release in the PVN, an increase in metabolic activity (via ACTH release from the pituitary and increase of tone in the SNS).
How do lesions in the hypothalamus affect sexual reflexes
What can give the same result
lesions of the mPOA abolish sexual copulatory behaviour in male rats while lesions of VMH impair female sexual behaviours including lordosis and solicitation.
even with an intact POA, a loss of steroids, brought about by castration, will abolish, as effectively, male sexual behaviour
What is the role of circulating steroid levels in sexual motivation
permissive role
How do we know circulating sex hormones play a permissive role in female sexual behviour
Ovariectomy in females reduces female sexual behaviour in the presence of an intact VMH
behaviours can be reinstated with oestradiol, followed by progesterone
How do sex hormones act to stimulate sexual behaviour normally
How was this shown
Androgen receptors are especially concentrated in the mPOA and oestradiol receptors and oestrogen
inducible progesterone receptors are found within the VMH.
sex hormones act on the steroid dependent neurons in these areas
implanting testosterone directly into the mPOA of castrated male rats and oestrogen/progesterone into the VMH of ovariectomised female rats restores their sexual behaviour
How do lesions of the mPOA affect the sexuality and motivation for access to a female
How does that compare to castration
impaired copulatory behaviour in the rat, as expected, but did not affect the rat’s motivation to lever press to obtain access to the female
castration did disrupt lever pressing as well as copulatory behaviour demonstrating that sex hormones are essential more generally in motivated sexual behaviou
How are the effects of lesions in the POA similar for temperature and sex in males
Rats with preoptic lesions didn’t display usual panting and vascular dilation in response to warming but did press a lever to obtain a cold puff of air.
lesions of the medial preoptic area impaired copulatory behaviour in the rat, as expected, but did not effect the rats motivation to lever press to obtain access to the female
Generally which motivational responses survive hypothalamic lesion
What is the hypothalamus therefore more preoccupied
incentive motivational responses/ instrumental responses
primarily to subserve the integration and expression of more reflexive and consummatory responses
Give a brief overview of the hypothalamus in motivation and homeostasis (3)
- The hypothalamus controls the internal environment via efferent systems which co-ordinate endocrine, autonomic and
behavioural responses. - The expression of motivated behaviours fulfill the primary needs of the organism - food, shelter, sexual and social interactions. By monitoring the internal state, the hypothalamus performs a key role in signalling biological priorities.
- Lesions of the hypothalamus that interfere with this information flow disrupt the expression of stereotyped motivated
behaviours
Where is the amygdala
lies in the anterior temporal lobe rostral to the hippocampus in the end wall of the inferior
horn of the lateral ventricle, adjacent to olfactory cortex.
What are the 3 subdivisions of the amygdala
cortico-medial division (Co+M) central nucleus (C) basolateral amygdala (BL)
