Transcript Neuroethology

Neuroethology
Study physical and chemical basis of
behavior
3 roles of nervous system in behavior
Relay information about environment
Processes information (brain and ganglion)
Relay instructions to muscles
Sign stimulus, releaser
Fix action pattern
Inner releasing mechanism – hypothetical
neural system responsible for triggering an
FAP in response to the appropriate sensory
input
Super-normal stimuli
Illegitimate signalers
Praying mantis
Protocerebral gangalia (PC) inhibits
subesophageal ganglion, and
suppresses abdominal muscle activity
Bat and moth
Properties of bat sounds – ultrasound and
pulsed
Bat navigation system has exerted strong
selection on nocturnal moth
Biaural hearing in moth
A1 cell response to low to moderate intensity
sound, fires much more frequently to pulses
of sound than to steady, uninterrupted sound
Auditory capability of A1 cell
A1 begin firing when bats about 100’
away
Location of bats at 3-dimensional space
Antipredator response
Fly directly away from bats
Only effective when bats are 8’ away
Noctuid moths respond to
sounds of bat-marking rings
(Anim. Beh. 57: 829-835, 1999)
Playback of bat calls and ring sound, check
neural & behavioral responses of moth
Peak energy of ring sounds occur closer in
frequency to the moth’s best auditory
frequency than calls
Ring sounds were detected at a
threshold 5~6 dB, lower than calls
Moths performed evasive responses to
playback of ring sound more frequently
than to control -- 14/33 no response, 1
to both, 14 respond to rings, 4 to
control
Retina  3 types of ganglia cell  optic
nerve  optic chiasm  optic tectum
(orienting) and thalamus (avoidance)
Type II tectal cells sum the excitory
signal from type I tectal cells and
inhibitory signal from thalamus
Circadian rhythm
Intrinsic or environmental-dependent?
w/o environmental cue – free-running
cycle
Entrains w/ environmental cue
 Environmental – independent biological
clock
 Environmental dependent entrainment
Neural mechanism
Disconnecting parts of brain and sensory
organs
In cricket, cut nerve from eyes to optic
lobes  free-running cycle begins
Severe optic lobes from rest of brain 
free-running cycle breaks down
In mammal, destroying SCN cells of
hypothalamus leads to arrhythmic cycle
Transplant SCN tissue from fetal hamster,
normal rhythm restored ~ 40%
Transplant of other brain tissues remain
arrhythmic
Environmental cues
Photoperiod
Moonlight – kangaroo rat
Temperature – green anoles
Food availability – breeding
Social interaction – regulating
reprodution
Neural basis of behavior
Lesion and split-brain technique
Functional neuroanatomy
Cannulation
Transplantation
Transection-cut
Neural stimulation
Psychopharmacology & neurotransmitter
Effects of hormone on behavior
Organizational - influence development
of structure
Metamorphosis
Brains - hormones regulate song nuclei
sizes
Gonads - sexual differentiation
Activational - coordinate responses to
environmental stimuli
influence sensation and perception
Courtship response - male mounts,
female lordosis
Reproductive behavior of
Anolis lizard
Females receptive in spring, affected by
the degree of courtship by dewlapdisplaying males
Courted females secret more
gonadotropic hormones, speed ovarian
development, and produce estrogen by
the mature ovaries
Estrogen affects endocrine and neural
targets  neck-arching behavior
Remove ovaries  abolish sexual
receptivity
Implantation of estrogen pellet  restore
sexual receptivity
Mated females cease receptivity in 5-7
min., attack males in next 10-14 days
Associated reproductive pattern – gamete
production and sexual activity are linked by
or associated w/ increases in particular
hormones
Disassociated reproductive pattern
Diverse effects of testosterone – promote
sperm production, activate sexual behavior,
stimulates aggressive behavior, suppress
immune system
Red-winged blackbird
Highest level of testosterone level in
male during nesting season, territory
defense, mate guarding
Higher level at high density areas
T level ~ # of females in territory ~ #
of offspring fledge
Testosterone and mating
Testosterone and territory
Dispersal of male ground squirrel
Am. Sci. 77:232-239, 1989
Background information of Belding's
ground squirrel.
Physiological mechanism: activational vs.
organizational?
Activational: lab (androgen level prior to
dispersal), field (castrated male/control)
Organizational: female + androgen induce
natal dispersal
External factor: aggression or avoiding
conspecific
Internal factors: min. age, min wt. +
behavioral changes: low level of fearfulness
during 4-10 wks, high levels of locomotion &
exploration=>shift of home range=>dispersal
Body fat and time of the year
mediate dispersal in ground squirrel
(Anim. Behav. 55: 606-614, 1998)
Early emergence: body mass as a good
indicator of dispersal
Late emergence: time, body mass are
not good indicator of dispersal
Methods in studying the
hormone basis of behavior
Extirpation (removal)
Hormone replacement therapy
Blood transfusion
Bioassey
Radioimmunoassey
Autoradiography