8a. Motivation Flashcards
2 Types of Motivation
- Internal homeostatic drive
- External goal/incentive motivation
Internal Homeostatic Drive
- Definition
Motivation to correct deviations from physiological set points
Internal Homeostatic Drive
- Examples
- Hunger
- Thirst
- Thermoregulation
Internal Homeostatic Drive
- Steps
- Input from sensors
- Integration to determine deviation from set point
- Output to correct deviation
Internal Homeostatic Drive
- Outputs
- Endocrine
- Autonomic
- Behavioural
External Goal/Incentive Motivation
- Definition
External pull towards a goal/incentive rather than internal drive
External Goal/Incentive Motivation
- Examples
- Sexual behaviour
- Aggression
- Competitive behaviour (running a race)
- Feeding or drinking due to pleasant taste
External Goal/Incentive Motivation
- Steps
- Input from sensors
- Integration to determine value of incentive/goal
- Output to achieve goal/incentive
External Goal/Incentive Motivation
- Outputs
- Endocrine
- Autonomic
- Behavioural
2 Types of Motivated Behaviour
- Consummatory
- Appetitive
Consummatory Behaviour
- Defintion
Behaviours that involve interacting with the goal object directly.
- Inflexible
- Species/goal specific
- Reflexive
Consummatory Behaviour
- Examples
- Eating
- Copulating
- Drinking
Appetitive Behaviour
- Definition
Behaviours that involve the performance of a voluntary behaviour to seek out a goal
- Flexible
Appetitive Behaviour
- Examples
- Food searching
- Lever pressing for delivery of a pleasant stimuli
- Attracting and searching for a mate
Decerebration Experiments
Cut above the midbrain to remove the forebrain
Some motivational behaviours are intact:
- Simple somato-motor reflexes
- Taste differentiation
- Hunger and satiety signals
Some motivational behaviours are lost
Hypothalamus
- Location
Ventro-rostral to the thalamus
Bordered rostrally by the optic chasm and caudally by the maxillary bodies
Hypothalamus
- Divisions
Medio-lateral divisions:
- Lateral
- medial
- Pericentricular
Anterio-posterior divisions:
- Anterior
- Middle
- Posterior
Hypothalamus
- Nuclei
- Dorsomedial
- Ventromedial
- Lateral
- Periventricular
- Arcuate
Hypothalamus
- Inputs
Inputs carry information on internal state
- Neural
- Chemical
- Temperature
Hypothalamus
- Neural Inputs
Brainstem
- Somatic afferents
- Visceral afferents
Forebrain
Hypothalamus
- Somatic Afferents
Don’t contain somatotopically organised information so don’t allow feature detection
Important in neuroendocrine reflexes:
- Milk ejection
- Stereotypical behaviours
Hypothalamus
- Visceral Afferents
Project form the nucleus of the solitary tract (NST) and reticular formation
Convey gustatory and olfactory information
Hypothalamus
- Forebrain Afferents
Originate from the amygdala and orbitofrontal cortex
Convey information about motivation significance of external stimuli
Hypothalamus
- Chemical Inputs
- Endocrine inputs
- Osmolality inputs
Hypothalamus
- Osmolality Inputs
Neurones in the organum vasculosum of the lamina terminals (OVLT) are sensitive to changes in osmolality, acting as osmoreceptors
Hypothalamus
- Temperature inputs
Neurones in the pre-optic area
Hypothalamus
- Outputs
- Endocrine
- Autonomic
- Behavioural
Hypothalamus
- Endocrine Outputs
Stimulates hormone output from the pituitary:
- Indirectly from the anterior pituitary
- Directly from the posterior pituitary
Hypothalamus
- Behavioural Outputs
Consummatory behaviours via brainstem reflex circuits.
Plays no role in appetitive behaviour
Hypothalamus
- Autonomic Outputs
Innervates the NST in the brainstem, which acts upon other brainstem nuclei and spinal cord neurones to control pre-ganglionic autonomic neurones.
More elaborate homeostatic adjustments involve reciprocal connections between the NST and higher centres:
- Amygdala
- PVN of hypothalamus
Hypothalamus Role in Thermoregulation
- Location
POA
Hypothalamus Role in Thermoregulation
- Motivation
- Behaviours
- Internal homeostatic drive
- Consummatory behaviours
Hypothalamus Role in Thermoregulation
- Cooling POA
- Reflex shivering (consummatory)
- Lever pressing to receive warm air (appetitive)
Hypothalamus Role in Thermoregulation
- Warming POA
- Reflex panting and grooming (consummatory)
- Lever pressing to receive cool air (appetitive)
Hypothalamus Role in Thermoregulation
- POA Lesions
Impairs consummatory thermoregulatory behaviours
- Reflex panting and grooming
- Reflex shivering
Does not impair appetitive thermoregulatory behaviours
- Lever pressing for thermoregulatory relief
Feeding
- Motivation
- Internal homeostatic drives
- External goal/incentive drives
Feeding
- Types of Satiety Mechanisms
- Short term
- Long Term
Feeding
- Short Term Satiety Mechanisms
Feedback mechanisms triggered by:
- Tasting food
- Smelling food
- Swallowing food
- Gastric distension following ingestion
- Lipids in the duodenum (cholecystokinin)
Feeding
- Long Term Satiety Mechanisms
- Nutrient reserves
- Leptin secretion
Feeding
- Cholecystokinin
Released from duodenum when lipids are present in the lumen.
Acts on leptin receptors in the pylorus which transmit information via the vagus to the brainstem to reduce feeding
Feeding
- Leptin Release
Peptide released by well-nourished adipose tissue
Feeding
- Leptin Actions
- Increase metabolic rate
- Decrease food intake
- Increase brain’s sensitivity to short term satiety signals such as cholecystokinin
Feeding
- Leptin Discovery
Discovered in a stria of obese rats who could not produce leptin.
Daily leptin injections increase metabolic rate and activity.
Feeding
- Neuropeptide Y Action
Signals hunger
Feeding
- Neuropeptide Y Release
Neurones in the arcuate nucleus
- Inhibited by leptin, which is present in well-fed state
- Activates by Ghrelin
Feeding
- Ghrelin Release
Empty stomach
Feeding
- Ghrelin Action
Signals hunger
Feeding
- Neuropeptide Y Actions
Promote feeding and preserve energy reserves
Acts on:
- Lateral hypothalamus
- Paraventricular nucleus
Feeding
- Neuropeptide Y Actions on Lateral Hypothalamus
Increases production of:
- Melanin concentrating hormone (MCH)
- Orexin
Both hormones stimulate eating and reduce metabolic rate
MCH and orexin producing neurones project to:
- Reticular formation
- Periaqueductal grey
- Thalamus
- Locus coeruleus
Feeding
- Neuropeptide Y Actions on Paraventricular Neurones
- Decreases metabolic rate
- Decreases insulin production
Hypothalamus Role in Feeding
- Location
- Lateral hypothalamus
- Ventromedial hypothalamus
Hypothalamus Role in Feeding
- Lateral hypothalamus Experiments
Lesions:
- Aphagia
- Adipsia
Lesioning also destroyed monoamine oxidase neurones in the medial forebrain bundle
Stimulation:
- Induces eating
Feeding centre sensitive to hunger
Hypothalamus Role in Feeding
- Ventromedial Hypothalamus
Lesions:
- Over-eating
- Obesity
Lesioning also destroyed axons between the arcuate nucleus and other hypothalamic brainstem nuclei
Sensitive to satiety signals
Hypothalamus Role in Feeding
- Motivation
- Behaviour
- Internal homeostatic drive
- Consummatory behaviour
Hypothalamus Role in Sexual Behaviour
- Behaviour
- Consummatory behaviour
Hypothalamus Role in Sexual Behaviour
- Location
Males:
- Androgen receptors in medial POA
Females:
- Progesterone receptors in ventromedial hypothalamus
Hypothalamus Role in Sexual Behaviour
- Medial POA Lesions
- Inhibits sexual copulatory behaviour (consummatory)
- Excitement and lever pressing to receive a female remains (appetitive)
- Appetitive behaviour remains
Hypothalamus Role in Sexual Behaviour
- Castration
- Inhibits copulatory behaviour (consummatory)
- Inhibits excitement and lever pressing to receive a female (appetitive)
Therefore, testosterone is permissive for sexual behaviour
Hypothalamus Role in Sexual Behaviour
- Ventromedial Hypothalamus Lesions
- Impair female sexual behaviours
Hypothalamus Role in Sexual Behaviour
- Ovarectomy
- Inhibits female sexual behaviour
Therefore, sex steroids are permissive for sexual behaviour
Amygdala
- Location
Anterior temporal lobe rostral to the hippocampus in the end wall of the inferior horn of the lateral ventricle, adjacent to the olfactory cortex.
Amygdala
- Divisions
- Cortico-medial division
- Central nucleus
- Basolateral division
Amygdala
- Inputs
Inputs carry information on external state, which often are conditioned stimuli that are predictive of rewards
Amygdala
- Outputs
- Endocrine
- Autonomic
- Behavioural
Amygdala
- Behavioural Outputs
Appetitive behaviours
Plays no role in consummatory behaviours
Amygdala
- Portico-Medial Division Nuclei
- Cortical nucleus
- Medial nucleus
Amygdala
- Corticomedial Division Afferents
- Olfactory cortex
- Olfactory bulb
Amygdala
- Corticomedial Divison Role
Olfaction and social and behavioural responses to pheromone secretion
Amygdala
- Central Nucleus Afferents
Solitary tract
Amygdala
- Central Nucleus Efferents
Major output of the amygdala
- Hypothalamus
- Brainstem
Amygdala
- Central Nucleus Role
Control of:
- Autonomic nervous system
- Endocrine system
- Simple motor reflexes
Amygdala
- Basolateral Division Afferents
Higher-order sensory regions:
- Pre-frontal cortex
Amygdala
- Basolateral Division Efferents
Project to regions involved in planning and action:
- Pre-frontal cortex
- Ventral striatum
- orbitofrontal cortex
Can be direct, or indirect via the mediodorsal nucleus of the thalamus
Amygdala
- 2 Efferent Pathways
- Ventral amygdalofugal pathway
- Diffuse pathway coursing directly across the temporal stem - Stria terminalis
- Runs around the lateral ventricle in the groove between the caudate tail and thalamus
Amygdala
- 2 Roles
- Assessment of motivational significance of stimuli in the basolateral nucleus
- Coordination of the output of a variety of response systems in the central nucleus
Amygdala Role in Fear Conditioning
Conditioned stimulus and fear stimulus follow different brain pathways and converge onto individual neurones with the lateral nucleus of the basolateral division of the amygdala
Amygdala initiates emotional responses by:
- Projections to the lateral hypothalamus to alter blood pressure
- Projections to the paraventricular nucleus to alter hormone output
Amygdala Role in Sexual Responses
Basolateral amygdala lesions inhibit lever pressing to obtain a female (appetitive), but don’t inhibit mounting and consumption when presented with a female (consummatory)
Amygdala Role in Feeding
Basolateral amygdala lesions inhibit lever pressing to obtain food (appetitive), but don’t inhibit eating when presented with food (consummatory)
Human’s brain activity measured by PET scans increases in the amygdala when reading a greater incentive value menu
Amygdala Role in Control of Voluntary Action
Basolateral amygdala identifies emotionally significant environmental cues and controls voluntary action by its output projections to the ventral striatum
Ventral Striatum
- Location
Part of the basal ganglia including nucleus accumbens
Lies ventral to the head of the caudate and putamen nuclei, and rostral to the hypothalamus
Dopaminergic Neurones
- Locations
- Substantia nigra (A9)
- Ventral tegmental area (A10)
Dopaminergic Neurones
- Projections
- Ventral striatum
- Amygdala
- Orbito-frontal cortex
Dopaminergic Neurones
- Lateral Hypothalamus Lesions
Lateral hypothalamus lesions damage the medial forebrain bundle, which contains dopamine projections to the striatum.
Some of this damage can be reversed by giving dopamine agonists
Dopaminergic Neurones
- Selective Lesions
Selective lesions of the medial forebrain bundle are made using 6-OHDA.
Cause dopamine deflation within the striatum, causing:
- Aphagia
- Adipsia
- Akinesia
Ascending Activating System of the Reticular Formation
- 4 Pathways
- Dopmine system
- Noradrenaline system
- Serotoninergic system
- Cholinergic system
Ascending Activating System of the Reticular Formation
- Pathway Activation
All 4 pathways are activated by motivationally charged environmental stimuli
Dopaminergic neurones may be modified by the amygdala and orbitofrontal cortex
Dopamine
- Role
Energises motivated behaviour, especially in preparation for action during appetitive behaviours
Dopamine release in the nucleus accumbens of the striatum increases during appetitive behaviour
Parkinson’s Disease
Selective neurodegeneration of dopaminergic neurones in subststantia nigra
Inability to initiate movement
Dopamine
- Measurement
Dopamine transmission can be measured using micro dialysis.
Dopaminergic Neurones
- Nucleus Accumbens Lesions
Loss of appetitive behaviours but intact consummatory behaviours.
Dopaminergic Neurones
- Caudate and Putamen Lesions
Causes:
- Aphagia
- Adipsia
- Akinesia
Loss of consummatory motivated behaviours
Dorsal Striatum
- Nuclei
Contains caudate and putamen nuclei
Dorsal Striatum
- Dopaminergic Neurones
Dopaminergic neurones in the substantia nigra project to the dorsal striatum, specifically to the caudate and putamen nuclei
Dorsal Striatum
- Role
- Activation of motor responses
- Sensory-motor integration
Ventral Striatum
- Dopaminergic Neurones
Dopaminergic neurones in the ventral tegmental area project to the ventral striatum, specifically the nucleus accumbens
Dopamine is released in the presence of primary rewards and stimuli associated with them
Ventral Striatum
- Nuclei
Nucleus accumbens
Interaction Between External Drives and Internal Incentives
- Feeding
Orexin neurones in the hypothalamus are activated in hungry state to activate feeding
Orexin neurones give output to the ventral striatum and ventral tegmental area and amygdala, allowing the internal drives to alter significance of external incentives
