Lecture 8: Sleep In Animals Species (Phylogeny Of Sleep)

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sleep phylogeny

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evolution of species sleep

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why study sleep phylogeny

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1) whats different: understand factors shaping sleep, can help make hypotheses about functions of sleep
2) what common: represent properties present in common ancestor and likely related to sleep restoration function & reinforces usefulness of invertebrate models ex) comparing fruit fly and mammal

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all animal studies show sleep/sleep like state
of 30+ animal phyla detailed info available for (2)

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chordates (vertebrates included) and arthropoda (includes insects)
* still possible to have truly sleepless animals just havent found them

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behavioral defn of sleepfor animals

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-quiescence w/ reduced response to stimuli,&rapid reversibility (unlike hibernation quiescence)
* exception of above = aquatic mammals/migrating birds
-homeostatic regulation seen in animals
-animals go to species specific location/get into specific posture

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in all nonhuman animals, the term SWS refers to all

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NREMS stages
in humans refers only to stage 3-4

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placental/marsupial mammals

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SWS, REMS

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monotremes ( egg laying--> platypus and echidna)

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echidna-->REMS seen only in brainstem SWS in cortex at same time!
platypus-->similar to above (refer to above as mixed sleep state)
**REMS= 8hours HIGHEST in any animals

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aquatic mammals (dolphins/porpoises that need to breath air)

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-uni hemisphere SWS (USWS)= one hemi SWS other similar to W
-lighter stage of SWS can happen in both hemi
-SWS homeostatically regulated independently in 2 hemispheres
-eye opposite to W hemi OPENED and monitor env
-can surface and breath during USWS

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aquatic: cetaceans (whales dolphins)

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signs of REM (twitching/rem) in small amounts/modified
ie) may have lost rem

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aquatic: manatees

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USWS, small amount REMS

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aquatic: seals

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sleep in water and on land

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1) phocidae seals

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some sleep on land,
hold underwater during bilateral SWS/REMS

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2) Otariidae family(fur/ear)

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sleep normally on land,
USWS when sleeping in water
W in one hemi S in other
unlike dolphin have asymmetrical posture/motor activity
--> active flipper (contralateral to W hemi) maintains position in water

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bird brain

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-comparable in relative size to mammals
& cognitive abilities like vocal learning and tool making
-but organized differently--> dorsal 2/3 forebrain derived from pallium (give rise to NeoCx in mammals), pallium organized nuclear manner lacks laminar organization
**only nonmammalian group to have unequivocal SWS/REMS

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bird sws

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like mammals-->low freq high volt EEG
diurnal bird (pigeon)--> SWS slow waves greatest early in night then decreases (mammalian like SWS homeostasis)
similarily regulated like mammals--> increase low freq EEG after sleep deprivation

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bird REMS

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close eyes
rem
bill movements
decrease muscle tone
*muscle atonia seen only in birds that can rest heads on back ex) ducks
similar to W
thermoregulation decrease
short (2-10sec) occur in cluster
less time in rem than mammals
time spent in rem increase after sleep deprivation
**SWS/REM recorded in all birds both probs present in most recent common dinosaur ancestors to birds

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more bird sleep info:
birds often sleep with ____like aquatic mammals
SWS in hemi opposite to
EEG between W and SWS in hemi opposite to
birds can switch between
is USWS common to all birds
REM happens

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one eye open
closed eye
open eye
both eye closed to one
yes, maybe ancestral
bi hemi

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Sleeping with one eye open and half‐a‐brain awake (USWS) may allow birds to

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sleep during flight

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sleep in reptiles:
EEG during sleep behaviour shows
Spikes reflect ____
their incidence correlated with___
increases after____
spike originate in
**Reptilian dorsal Cx, however, does not generate high voltage slow waves typical of mammal and bird SWS
describe REM

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intermittent high voltage spikes
sleep intensity
arousal threshold
sleep deprivation
the hippocampus
exist, but may represent partial arousal from sleep, no REM in BS

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The presence of unequivocal SWS and REMS in mammals and birds but not in reptiles, amphibians or fish, suggests these sleep states

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arose independently in mammals and birds (convergent evolution)

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lack of SWS in reptile may be due to

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connections within areas of cortex

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mammals: corticortical connections in layers ____play
role in _________and generate __

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2‐3
synchronizing slow neuron oscillations
slow waves

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birds: lack a true neocortex but their hyperpallium
shows

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lots interconnectivity

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reptiles: three‐layered dorsal cortex lacks ___and shows limited_____

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layers 2‐3
corticocortical connectivity

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sleep in invertabrates:
account for more than 97% of all animal life( T or F)
focused on arthropods (T or F) for studying sleep in invertabrates since better understood and easier to manipulate than mammals

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T
T *problem with it is hard to transfer insight to human sleep ex) no orexins in fruit fly, or no octopamine in mammals but in fruit fly

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honeybees:
describe sleep (3)
sleep is ____regulated in honeybees

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-quiescence, increased arousal threshold, specific posture (antennae immobile)
- homeostatically (sleep deprived--> antennae immobility increases)

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fruit flies:
like honey bees meet behavioral definition of sleep. Their threshold increases during immobility BUT

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rapidly awaken when enough stimuli applied
make up for sleep deprivation with rebound of inactivity

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so arthropods demonstrating sleep (5)

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honey bees
fruit fly
scorpions
cockroaches
crayfish

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3 new animal phyla that may show sleep=

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nematodes (c elegan)
mollusca (octopus)
cnidaria (jellyfish)

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Drosophila activity monitoring system

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tube with agar plug one end, cross tube with infrared

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More is known about sleep in ____ than in any other group of animals

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mammals

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Sleep has been studied in more than ___ mammalian species, but only about ___ species have been studied with sufficient measurements of the amount of REMS/NREMS over the 24‐hr period

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100
60

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These species are by no means a _____. They are species that are viable/available for study in laboratories or for noninvasive (less accurate) studies in zoos

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random sample of the more than 5,000 mammalian species

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In laboratories, animals are typically kept with food ad libitum, and on(2)
*This environment differs greatly from those in which they normally live

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artificial light and at thermoneutral temperature/humidity.

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In addition, studies are not at all exhaustive
(T or F)

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T

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Digital recording and storage technologies now exist to enable ____ but they are not widely used yet. This would allow study of the variation in sleep time cause by hunger, temperature changes, predation and other variables that have driven evolution

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sleep data collection from animals in the wild

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Studies correlating sleep parameters with various behavioral and physiological parameters have found some ______ between single measured or hypothesized conditions, but have not been able to explain a substantial portion of the variance of these parameters between _____

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small correlations
mammals
correlations do not necessarily mean causation

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The strongest correlation found in earlier studies is that between the ________ (the time from the start of a REMS period to the start of the next, excluding interposed W) and _______ (positive correlation) and ________ (negative correlation)

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duration of the sleep cycle
brain weight
metabolic rate/body temperature
*accounts for 80% variance in sleep cycle time amongst animals

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Earliest studies found that total S duration was
_____with body weight
and______with metabolic rate/body temperature
*Since S is linked to a reduction in body temperature
and a reduction in energy usage, it was hypothesized
that
**A later re‐analysis found that the inverse relationship between time spent in S and body weight is was true only for _____ and not for carnivores or omnivores

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negatively correlated
directly correlated
energy conservation might be a function of sleep
herbivores,

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Most comparative studies treat each species
as a statistically independent unit. However,
species cannot be considered independent
because they are related to one another
through common ancestry
* use ______(3 words) to deal with such interspecific relatedness in comparative studies

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Phylogenetic comparative methods

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using Phylogenetic comparative methods:
Rattenborg & coll obtained that, contrary to the
expectations under the “energy conservation hypothesis”, species with higher basal metabolic rate sleep

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less

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“energy conservation hypothesis” may still hold true
based on the following considerations

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a) the observed relationship may reflect increased feeding demands and thus less time available for sleep
b) nonetheless, these animals may obtain comparable amount of SWS by engaging in a more intense SWS,
although such intensity data are largely unavailable
c) alternatively, the sleep restorative process could be achieved more quickly with higher residual basal
metabolic rate

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Significant _____ correlations were found between REMS time (but not total S time) and _____(2)
*accounts for only for 4% of the variance in REMS time among species.

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negative
brain weight and encephalization (brain weight/body weight).

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Using phylogenetic comparative methods, Rattenborg & coll obtained that species with higher____ show more REMS, thus providing the first comparative support for a neurophysiological role of REMS.

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encephalization

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No such correlation was found for time spent in SWS. However, a more accurate measure of SWS may be _____rather than simply the time spent in SWS

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cumulative slow‐wave activity

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-Animals with high______ sleep less. Predation risk may be an important factor affecting sleep structure and sleeping time. Because of their high arousal threshold, SWS and REMS are “dangerous” states
-Rattenborg & coll found that species sleeping in risky location in the wild engage in less _____.
-time spent in SWS seemed largely _____ from predation risk. However, SWS intensity/activity may correlate more strongly with predation risk in these animals

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-predatorial risk
*carnivores>omnivores>herbivores (sleep more)
-REMS
-independent

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Another robust correlation is between adult REMS time and immaturity at birth: species more immature at birth (altricial species, as rats, cats, dogs, humans) show ____ REMS as adults while species more precocial at birth (ex.guinea pigs, sheeps, horses) show ___REMS as adults

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more
less
*doesnt depend on predation risk
**may reflect extension of ontogenetic changes in rems-->supports idea that REMS important in early brain development

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conclusion:
-why is are people raising the question whether correlational approach thats being used is actually even getting at core issues of sleep function
-why take above with grain of salt
-Despite similar genetics, anatomy, cognitive abilities and physiological functioning, closely related species can have very different sleep parameters and distantly related species can have very similar sleep parameters (T or F)

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-because all the other correlations (except strong correlation between cycle length and brain/body mass) account only for a small portion of the variance in S parameter
-many measurements lack for many species
-T