NHB (Neurobiology and Human Behaviour) Motivation, Arousal, Homeostasis

NHB (Neurobiology and Human Behaviour) Lecture
Notes: Motivation, Homeostasis, Arousal
Motivation
Motivation is activation and direction to behaviour

Drives
● Internal drives (push) to reduce deficit state (homeostasis)
● External incentives (pull) towards a goal
○ Drives sexual, red bottom on female monkey
○ Feeding, see chocolate, want to eat it


Phases
● Consummatory: interacting with goal, species/goal-specific
● Appetitive: seek/prepare for goal (catching food, pulling lever), flexible

HT (HypoThalamus) (direction of consummatory behaviour)
● Organisation
○ Periventricular, medial and lateral
○ Anterior, tubal, lateral-posterior
● Inputs
○ BS
◆ Somatic (not somatotopic, for specific behavioural reflexes):

breast (for milk ejection), genitals (for sexual behaviour)
◆ Visceral (NST) for state of body
○ Forebrain (higher-order afferents)
◆ Amygdala, OFC (OrbitoFrontal Cortex): carries motivational

significance of external stimuli
○ Hormones (e.g. sex hormones)
○ Temperature (MPOA (Medial PreOptic Area)), osmolarity (no BBB

in OVLT (circumventricular organ))
● Outputs
○ Endocrine
◆ Indirect: parvocellular secretory cells -> portal -> anterior

pituitary (makes hormone)
◆ Direct: magnocellular secretory cells -> posterior pituitary (site

of hormone release)
○ Neural
◆ To BS for reflex behaviours (spinal reflex that incorporates BS)

(e.g gnawing, eating, shivering, drinking)
◆ To NST (also via hormones), to BS and spinal neurones, to

preganglionic ANS (fight or flight)
○ So HT can control hormonal, autonomic and behavioural systems
● Lesions lead to loss of consummatory reflexes but not appetitive
behaviour (loss of forebrain (amygdala) does this)
○ Warming MPOA -> rat presses lever more for cool air

, ◆ Lesion loses reflexes (shivering, panting, groom) but rat still
presses lever if MPOA gets warmer
○ MPOA also has steroid (sex hormone) receptors
◆ Lesion loses copulatory behaviour but male rat is still excited in

presence of female in heat

Amygdala (direction of appetitive behaviour)
● Organisation
○ Only subcortical structure in temporal lobe (hippocampus is

cortical)
○ Cortico-medial division, olfaction/pheromones
◆ Tiny in humans
◆ Sexual and social behaviour dependent on pheromones
○ Central nucleus, autonomic/endocrine
◆ To HT (autonomic and endocrine), BS reflexes (simple motor

reflexes)
◆ Similar output to HT but different input
○ Baso-lateral amygdala (biggest in humans), higher-order sensory/

motivational/emotional assessment
◆ Receives highly processed sensory information from all

unimodal association cortices and information about internal
state
◆ So can associate external stimuli with internal factors
◆ To VS and (MD thalamus ->) OFC
● Output
○ Ventral amygdalofugal pathway
◆ Diffuse pathway, directly across temporal stem, to forebrain

(HT)
○ Stria terminalis
◆ Longer pathway into HT
● Lesions of BL reduce appetitive but not consummatory
○ 6-OHDA in VS -> female rat does no ear wiggling but still does

lordotic position
● Experiments
○ Measure dopamine in male rat VS with CSF dialysis
◆ Rises when enter chamber to see female (conditioned

stimulus)
◆ Rises more when see female
◆ Goes down after mating
◆ Same with seeing and eating food


Dopamine (activation of behaviour)
● Substantia nigra -> DS (Dorsal Striatum)
○ Activates consummatory behaviour
● VTA (Ventral Tegmental Area) -> VS (Ventral Striatum), amygdala and