Cetaceans: Brains Flashcards
Why does absolute brain size matter?
more matter = more connections
What is Encephalization Quotient (EQ)?
ratio of actual brain mass to expected brain mass of comparison animal, corrected for body size
What is special about the cerebellum for Tursiops?
bottlenose dolphins have largest relative size of any cerebellum of any mammal
What does the cerebellum do for cetaceans?
-area involved in movement of limbs, posture, head (visual tracking) REDUCED
- areas controlling face, trunk and tail = ENLARGED
- articulate vocalizations
Unlike primates who are altricial, cetaceans are ______ at birth
precocial (well developed)
Dolphins have ____ month gestation
12
Dolphin brain at birth is _____% of the adult brain
40
Human brain at birth is _____% of the adult brain
25
What is the importance of the impedance match of seawater and amniotic fluids for cetacean fetuses?
sound is able to impede vibration in different ways, possibly explains for extensive development of acoustic processing by brain
Cetacean auditory nerve has _____ times the fibers to humans
2.5
What is unique about the auditory system for cetaceans?
main source of info on shape, size, content, distance of stimuli
Cetaceans have what in their auditory nerve to increase transmission speed?
huge, myelinated fibers
The fact that the lateral lemniscus is 250x size humans, the inferior colliculus is 12x size humans, and the thalamus MGN 7x size of humans allows dolphins to what?
easily find where sounds are
Explain the dual processing system
brain stem = giant, broadband, brief, fast changing inputs
cortex = layers, intepreting sound => “Language”/higher cognitive processing
What is similar and different about the auditory system in humans and dolphins?
dolphins have same process but the proportions at each stage different
(True/False): Cetaceans have small amounts of fovea
FALSE; Cetaceans have NO fovea
BUT have dense, giant, myelinated ganglions from central area
(True/False): Cetaceans can see colors the way humans see color.
FALSE; Cetaceans see no color- only one kind of cone receptor
Do cetaceans have more rods or cones?
more rods for motion, allows them to be sensitive moving stimuli
The cetacean visual system has ______ ______, resulting in very little binocular vision and little depth perception
complete crossover
What is the superior colliculus for? Who has a bigger superior colliculus, humans or cetaceans?
visual motion; Cetaceans
Describe the basic auditory pathway in cetaceans.
cochlea -> cochlear nucleus -> superior olivary (where sounds from both ears combine) ->inferior colliculus (how sounds moving) -> A1 (auditory cortex)
Where do cetaceans have the greatest tactile sensitivity?
face (esp eyes, lower jaw), blowhole, genital area
What is unique about the specialized tacto-acoustic cortex in cetaceans?
sound and tough converge together in this cortex so that there is a response to touch and sound; adjacent to A1 => early processing, touch and sound merged
Vestibular tracts in cetaceans are ____ ____ compared to other mammals
much reduced
What does the vestibular system allow for cetaceans?
enable frequent, rapid, body rotations; grace, balance handled by other systems
Explain the ability to smell for odontocetes.
No smell in odontocetes = no olfactory bulb in odontocetes (severely reduced in mysticetes)
Can cetaceans taste?
have taste receptors and tracts but minimal
What is different about the limbic system in cetaceans in comparison to primates?
overall well developed, but with certain structures enlarged, others reduced
What is unique about the hippocampus in cetaceans?
much reduced, yet have excellent memory
The amygdala in cetaceans is ______ and heavily connected with the ______ system
enlarged; Auditory system
Do cetaceans show the presence of the Theory of Mind?
presume, but not proven due to large amygdala; cetaceans known to live “rich emotional life” run by feelings
What is unique about the cortex of cetaceans?
most convoluted surface of any mammal although cortex layer is thinner than primates
-1/3 more surface area than humans, fewer neurons, more glial cells
What is unique about the cytoarchitecture (cell structure/configuration) in cetaceans from other mammals?
- No obvious granularity in Layer IV (normally the receiving layer from Thalamus)
- less columnar differentaiation
The division of the occipital and parietal lobe in cetaceans is ____ ______
not present
What is the S-A area in cetacean brains?
specialized frontal area, adjacent to S1, for processing “Tacto-Acoustic” info
What parts of the brain do cetaceans have that allow for “higher” processing?
- sulcus after sulcus in S-A and V1 area
- unmapped Association Cortex
- extra lobe that does not correspond to any in human/primate brain
The Prefrontal cortex in cetaceans, including frontal pole is ______ than in humans
smaller
What cetaceans have Von Economo Neurons?
Bottle nose dolphins, belugas, sperm whales, orcas and humpback whales for mysticetes
Where are Von Economo Neurons found in cetaceans?
ACC and FI (like us); also in frontal pole (nlike us)
(True/False): Cetacean brain is symmetrical.
FALSE; right hemisphere larger
What size is the corpus callosum? What does this suggest about sleep patterns?
smallest corpus callosum among mammals, suggests minimal communication between 2 hemispheres, allows them to sleep with one half of brain “on” and “off”
(True/False): Cetaceans undergo REM sleep in their final stage, stage 3, of sleep
FALSE; Cetaceans undergo NO REM sleep
What stage of cetacean sleep can we only detect one hemisphere at a time?
3
Why do cetaceans have to sleep with one hemisphere “on” at all times?
the other non asleep hemisphere must stay awake enough to breath
Do cetaceans have mirror neurons? How does Chris feel about it and what would she bet to prove it?
not proven; Chris believes they do and would bet her firstborn
Dolphins preferentially use _____ eye , which gets from information from the _____ brain to look at strangers
left eye, right brain
Humans are lateralized to ______ hemisphere for speech and handedness
LEFT
What is unique about the cetacean brain compared to primates?
faces down, strange layout that is very different than primates, faces opposite way of primates
