Download presentation
Published byCynthia Clark Modified over 9 years ago
1
BIORHYTHMS & SLEEP Psychology 2401, Foundations of Biopsychology
Sarah Arthurs, 2015
2
A Time for Everything Ecclesiastes 3: 1-8
There is a time for everything, and a season for every activity under the heavens: a time to be born and a time to die, a time to plant and a time to uproot, a time to kill and a time to heal, a time to tear down and a time to build, a time to weep and a time to laugh, a time to mourn and a time to dance, a time to scatter stones and a time to gather them, a time to embrace and a time to refrain from embracing, a time to search and a time to give up, a time to keep and a time to throw away, a time to tear and a time to mend, a time to be silent and a time to speak, a time to love and a time to hate, a time for war and a time for peace. Ecclesiastes 3: 1-8
3
DEFINITION OF A SECOND 9,192,631,770 periods of the radiation corresponding to the transition between two hyperfine levels of the ground state of the caesium-133 atom - 13th GENERAL CONFERENCE OF WEIGHTS AND MEASURES 1967
4
The environment is rhythmic Mairan (1729) and the Mimosa plant
Nature’s Rhythms The environment is rhythmic Mairan (1729) and the Mimosa plant Erwin Bünning and chronobiology Rhythms in insects and animals Erwin Bünning
5
Ultradian (less than a day) Circadian – (day) Circalunar (~29.5 days)
Nature’s Rhythms Ultradian (less than a day) Circadian – (day) Circalunar (~29.5 days) Annual (~365 days) Diurnal (active during the day) Nocturnal (active at night) Crepuscular (active at twilight)
6
Nature’s Rhythms Magicicada
7
CIRCADIAN RHYTHMS
8
Circadian Rhythms circa, about; diem, a day intertidal (~12.4 hours)
9
Human Circadian Rhythms
10
Zeitgebers Circadian Rhythms
(from the German zeit=time and geber=giver): Environmental time cues Light/dark, temperature, humidity… In their presence, animals become entrained to the day/night rhythm and maintain an activity of exactly 24 hrs In their absence, animals will settle into a rhythm of activity/rest within 24 hours (more or less)…these rhythms are free run Most free run rhythms range between hrs
11
Circadian Rhythms Free running
12
Endogenous Clocks: Early Evidence
Curtis Ritcher (early 1920s): first systematic study of the range of biological rhythms in mammals Behaviorism vs. homeostatic drives The search for the endogenous clock: lesioning studies and the hypothalamus
13
Suprachiasmatic Nucleus (SCN)
Hypothalamic nuclei containing 20,000 cells Receives major input from areas in the hypothalamus, thalamus, and midbrain Projects to hypothalamic nuclei, various thalamic nuclei, and spinal cord Light is its most potent Zeitgeber
15
Sidebar: Neural Oscillators
Endogenous Clocks The SCN acts as an neural oscillator Sidebar: Neural Oscillators - Generate endogenous rhythmic bursts of activity. Spike trains Local field potential Large scale oscillations
16
Sidebar: Neural Oscillators
Endogenous Clocks Sidebar: Neural Oscillators Activity of a large set of neurons produce synchronized oscillations in one of two ways: They may take cues from central clock (pacemaker) Share or distribute the timing among themselves by mutually exciting or inhibiting one another
17
Endogenous Clocks SCN neurons are NOT monophasic: 50-60% form a main phase group, and two other phases that each represent 10-20% of the oscillating neurons Peak every 3-4 hours, with a select smaller group peaking at nighttime (antiphase) Feedback inhibition (Quintero, Kuhlman, & McMahon, 2003)
18
Suprachiasmatic Nucleus (SCN)
Rates of firing vary with circadian rhythm SCN neurons show a circadian pattern of high activity in morning and low activity at night SCN neurons communicate via action potentials and chemical messenger (vasopressin)
19
Suprachiasmatic Nucleus (SCN)
20
Suprachiasmatic Nucleus (SCN)
Since behavior is synchronized with light/dark cycles, there must be a photosensitive mechanism involved: Retinal ganglion cells via retinohypothalamic tract Synapse directly on SCN neurons SCN neurons have very large receptive fields and respond to luminance changes (not motion or orientation)
21
Suprachiasmatic Nucleus (SCN)
Surprisingly, the retinal cells that aid in synchronizing the SCN are not rods or cones Eyeless mice cannot reset their clocks, but mice with intact retinas lacking rods and cones can “Visually blind but not circadian blind.”
22
Melanopsin
23
Light Entrainment Deleted/silenced photopigment gene(s)
Effect on circadian rhythms Melanopsin Diminished Rods and cones No effect Melanopsin, rods, and cones Abolished
24
Relay station or actual endogenous clock?
Endogenous Clocks Relay station or actual endogenous clock? Evidence from the tau mutant hamster…
25
Endogenous Clocks An isolated cell from the SCN will maintain the same rhythmic oscillations Transplanted SCN cells into cerebral ventricles will still act as a central pacemaker Cells outside of the SCN (lungs, liver, pancreas, spleen, thymus, skin, etc.) also have free-running rhythms SCN functions as the central clock that ensures other central and peripheral rhythms are synchronized (think of world time zones, whereby the Coordinated Universal Time serves as the time standard by which other world clocks are regulated)
27
Endogenous Clocks
28
BRAIN RHYTHMS
29
Electroencephalogram (EEG)
Records generalized activity in the cerebral cortex Hans Berger (Austria, 1929) First described the human EEG Observed differences in EEG activity
30
Electroencephalogram (EEG)
31
Electroencephalogram (EEG)
WHAT GENERATES THE OSCILLATIONS OF AN EEG? An EEG measures voltages generated by dendritic synaptic excitation of pyramidal cells of the cortex However, any single neuron does not contribute much to the electrical signals recorded by the EEG Therefore, an EEG is a reflection of many thousands of neurons firing simultaneously
32
Electroencephalogram (EEG)
33
Electroencephalogram (EEG)
CONSEQUENCES OF SUMMATION The amplitude of EEG signal strongly depends, in part, on how synchronous the activity of the underlying neurons is. Synchronous activity: when a group of cells are simultaneously excited and the “mini” individual signals summate to generate one large surface signal Irregular activity: when a group of cells receives the same amount of excitation but do not respond simultaneously the summation does not amount to much
35
TYPES OF RHYTHMS EEG RHYTHMS
Beta rhythms: greater than 14Hz, signal activated, alert cortex Alpha rhythms: 8-13Hz, signal awake but quiet and relaxed states Theta rhythms: 4-7Hz, signal some of the deep sleep states Delta rhythms: very slow, very large in amplitude, less than 4Hz, hallmark of deep sleep
37
Both hemispheres show similar patterns of electrical activity
EEG RHYTHMS NORMAL EEG Alpha & beta waves Both hemispheres show similar patterns of electrical activity No abnormal bursts of electrical activity & no slow brain waves Proper response to photic stimulation
38
Sudden bursts of electrical activity or sudden slowing of brain waves
EEG RHYTHMS ABNORMAL EEG Sudden bursts of electrical activity or sudden slowing of brain waves Delta waves or too many theta waves in adults who are awake. a "flat" or "straight-line" EEG
39
EEG RHYTHMS EEG recordings do not allow us to read a persons thoughts, but they do allow us to tell if a person is thinking. frequency and amplitude rhythms are associated with alertness, waking, and dreaming sleep states frequency and amplitude rhythms are associated with non-dreaming sleep states and pathological states of coma
40
BRAIN RHYTHMS Rhythmic synchronous activity is usually coordinated by a combination of a pacemaker & collective methods Similar to the SCN, the thalamus can generate very rhythmic action potential discharges
41
FUNCTION OF BRAIN RHYTHMS
Synaptic connections between excitatory and inhibitory thalamic neurons force each individual neuron to conform to the rhythm of the group Coordinated rhythms passed to cortex
42
Seizures & Epilepsy Most extreme form of synchronous brain activity
BRAIN RHYTHMS Seizures & Epilepsy Most extreme form of synchronous brain activity Generalized seizure: involves the entire cortex of both hemispheres Partial seizure: involves a particular area of the cortex Epilepsy: a condition defined by repeated seizure experiences ~ 1% of the American population has epilepsy
43
During more forms of generalized seizures:
BRAIN RHYTHMS During more forms of generalized seizures: All cortical neurons are engaged Unconscious Muscles – tonic or clonic activity
44
Seizures & Epilepsy BRAIN RHYTHMS
GABA receptor antagonists are very potent convulsants: Block GABA receptors Seizure-promoting agents GABA receptor agonists are very potent anticonvulsants: Suppresses seizures by countering excitability in various ways (e.g., prolong inhibitory influence of GABA)
46
Sleep
47
Sleep DEFINITION Sleep is a readily reversible state of reduced responsiveness to, and interaction with, the environment (anesthesia and coma do not count since they are not readily reversible).
48
Sleep REM sleep When EEG looks more awake than asleep
Your body (except eye and respiratory muscles) is immobilized Often associated with dreaming
49
Temperature and energy consumption lowered
Sleep Non-REM sleep (slow-wave) sleep Period of rest Temperature and energy consumption lowered Heart rate, respiration, and kidney function all slow down Digestive processes speed up Brain rests William Dement (Stanford University): REM SLEEP: “An active, hallucinating brain in a paralyzed body” NON-REM SLEEP: “An idling brain in a movable body”
52
Non-REM Sleep Stage 1: muscles relax; beta waves replaced by alpha waves; lasts 3-12 min. Stage 2: characterized by theta waves with occasional bursts of higher frequency waves known as sleep spindles (8-14 hz); also experience high amplitude K complex associated with brief awakenings; 50% of total time asleep spent in stage 2.
53
Origin of Sleep Spindles
Thalamic neurons can exhibit one of two steady states: spontaneous oscillatory activity and tonic activity (neurons are depolarized by external inputs)
54
Origin of Sleep Spindles
The more the thalamocortical neurons are hyperpolarized by the thalamic reticular nucleus, the more stable their oscillatory activity, and thus the more steady the action potentials that are sent to the cortex. These action potentials summate to generate the sleep spindles that are recorded with EEG during stage 2 sleep. Interrupted by external input from brainstem
55
Non-REM Sleep Stage 1: muscles relax; beta waves replaced by alpha waves; lasts 3-12 min. Stage 2: characterized by theta waves with occasional bursts of higher frequency waves known as sleep spindles (8-14 hz); also experience high amplitude K complex associated with brief awakenings; 50% of total time asleep spent in stage 2.
56
Non-REM Sleep Stage 3: deep sleep; delta waves appear, with still some sleep spindles and K complexes; some muscle tonus; lasts ~ 10 min. and accounts for ~ 7% of total sleep time Stage 4: deepest sleep; dominated by delta waves; parasympathetic nervous system lowers brain temperature, breathing, heart rate, and blood pressure; lasts min. and accounts for15-20% of total sleep time; some muscle tonus and movement; body’s repair work; stage when children experience sleepwalking and night terrors
57
ultradian rhythms
58
Sleep Stages
59
Localization of Sleep Mechanisms in the Brain
A forebrain system generates SWS sleep and inhibits the tuberomammillary nucleus of the hypothalamus A brainstem system activates the sleeping forebrain into wakefulness A pontine system (in brainstem) triggers REM sleep A hypothalamic system to coordinate the other three brain regions to determine what state we are in
60
Neurobiology of Sleep SLEEP PROMOTER
Ventromedial preoptic nucleus (VLPO) of the anterior hypothalamus: contains neurons that release GABA and project to and inhibit activity of the ascending arousal system and the lateral hypothalamus (LH)
61
Neurobiology of Sleep WAKEFULLNESS
Ascending Arousal System (AAS) consists of: Reticular formation Laterodorsal tegmental area (LDT) and pedunculopontine tegmental nuclei (PPT), which are in the brainstem and project to the thalamus, and then onto the forebrain; release acetylcholine (Ach) Locus coerulueus (LC) of the brainstem; neurons project to forebrain and release norepinephrine (NE)
62
Neurobiology of Sleep WAKEFULLNESS
Ascending Arousal System (AAS) consists of: Dorsal raphe nucleus (DR) of the brainstem; neurons project to the forebrain and release serotonin Tuberomammillary nucleus (TMN) of the hypothalamus project to the forebrain and release histamine
63
Neurobiology of Sleep WAKEFULLNESS
Laterodorsal hypothalamus (LH) projects to the nuclei of the AAS, the forebrain, and the VLPO, and releases orexins (hypocretin)
64
Neurobiology of Sleep Suprachiasmatic Nucleus (SCN) regulates various sleep structures of the brain either directly by neural or chemical outputs, or indirectly through melatonin.
65
Neurobiology of Sleep The SCN connects to the pineal gland via the superior cervical ganglion (SCG) Pineal gland releases melatonin When red light (~ > 650 μm) hits the eye, the transduction signal travels through the optic nerve to the SCN, which then signals the the pineal gland by activating norepinephrine (NE) receptors This results in the release of melatonin, which decreases alertness and increases sleepiness Melatonin is inhibited by blue light (~ < 500 μm)
66
Sleep-Regulating Factor
Melatonin Released from pineal gland: located just above tectum Derivative of tryptophan “Dracula of hormones”
67
RGCs → melanopsin → SCN → SCG → pineal gland → melatonin suppression
Neurobiology of Sleep RGCs → melanopsin → SCN → SCG → pineal gland → melatonin suppression
69
Other Sleep-Promoting Factors
Adenosine Inhibitory effect on Ach, NE, and 5-HT Adenosine levels throughout the day Neural activity in the awake brain increases adenosine levels Administration increases sleep Brain will fall into the slow-wave synchronous activity (e.g., increases NREM sleep)
71
Other Sleep-Promoting Factors
Interleukin-1 Immune responses (inflammation, fever, etc.) Synthesized by brain Plasma levels highest at sleep onset Strengthens NREM and suppresses REM
72
Mechanisms of REM Sleep
Neurons of the motor cortex continue to fire rapidly and attempt to command the muscles of the body but only succeed with the eye, ear, and respiratory muscles V1 is equally active in REM and waking Extrastriate areas and limbic areas more active during REM Frontal lobe activity less active in REM sleep
73
Mechanisms of REM Sleep
The firing rates of the locus coeruleus and raphe nuclei decrease to almost nothing Sharp increase in firing rate of ACh neurons in the pons
74
Can also dream during SWS – “thinking” type
REM and Dreaming Although the most vivid dreaming occurs during REM sleep, REM and dreaming ARE NOT SYNONOMOUS Can also dream during SWS – “thinking” type While REM is largely controlled by the brainstem, dreaming is a function of cortical activity Where occipital, temporal, and parietal cortices meet Frontal lobe and the mesolimbic pathway Dopamine innervation
75
Hobson & McCarley (Harvard University)
Dream Theories Sigmund Freud Dreams are disguised wish-fulfillment, an unconscious way for us to express our sexual and aggressive fantasies, which are forbidden to us when we are awake Hobson & McCarley (Harvard University) More biologically based theories “activation-synthesis hypothesis” Dreams are seen as associations and memories of the cortex that are elicited by the random discharges of the pons during REM sleep
76
Activation Synthesis Hypothesis
The pontine nucleus, via the thalamus, activate different areas of the cortex, elicit images/emotions, and the cortex attempts to synthesize the disparate images into a coherent whole This process can account for the often bizarre and nonsensical nature of many dreams; since they are triggered by the semi-random activity of the pons
77
Why don’t we act out our dreams?
Adaptive Brainstem areas responsible for REM sleep contain GABAB & GABAA/glycine that project to and synapse with motorneurons Hyperpolarize motorneuron activity Blocking these receptors prevent sleep paralysis REM sleep behaviour disorder (Brooks & Peever, 2012)
78
Theories of restoration vs. theories of adaptation
Sleep Theories Theories of restoration vs. theories of adaptation We sleep to rest and recover We sleep to keep us out of trouble Does sleep renew us the same way eating and drinking do? Familial Fatal Insomnia
79
Sleep & Performance
80
REM and Memory Consolidation
Rats learning new tasks show increased REM sleep after tests; the more trials a rat experienced, the faster it fell into REM sleep REM sleep deprivation in humans and rats can impair ability to learn new tasks Memory loss occurs when sleep is deprived on the same night or two nights after material has been learned (first or last two REM episodes of the night) Non-REM sleep deprivation actually enhanced their performances Hippocampus and theta waves
81
Sleep and Academic Performance
Typical sleep habits of a student Regular sleep/wake cycles associated with higher CGPAs Individuals who engage in “all-nighters” tend to have poorer GPAs (Forquer, Camden, Gabriau, & Johnson, 2008; Thacher, 2008)
82
Chronotype Chronotype: propensity to sleep at a particular time during a 24 hour period “Eveningness” (owls; delayed sleep period) and “Morningness” (larks; advanced sleep period) Sleep/wake preferences validated by observable daily rhythms in body temperature, melatonin, and cortisol levels Age and sex influences (Önder, Horzum, & Beşoluk, 2012)
83
Chronotype and Academic Performance
E-types: lower academic performance, more cognitive failures uniformly distributed throughout the day; sleep qualities are poorer and daytime sleepiness is higher Sleep deprivation and phase delays = academic performance M-types: more cognitive failures in the evening Class/Exam Scheduling and Achievement: M-types with a class schedule that runs from morning to early afternoon showed higher CGPAs and performed better on morning exams than E-types on this same schedule. E-types with a class schedule that runs from late afternoon through the evening showed higher CGPAs and performed better on afternoon exams than M-types on same schedule (Önder, Horzum, & Beşoluk, 2012)
84
Disrupted Rhythms
85
More severe when traveling west to east
Jet Lag Circadian misalignment: the inevitable consequence of crossing time zones too rapidly for the circadian system to keep pace More severe when traveling west to east
86
Seasonal Affective Disorder (SAD)
A clinical condition characterized by regular onset and remission of depressive episodes that follow a seasonal pattern Circadian Models Monoamine Hypothesis Genetic predisposition (Kreitzman, & Foster, 2011)
87
Adjusting Circadian Rhythms
Prescribed sleep scheduling Circadian phase shifting (use of therapeutic light) Timed melatonin administration Manipulating body temperature Promoting sleep with hypnotic medication Promoting alertness with stimulant medication
Similar presentations
© 2025 SlidePlayer.com Inc.
All rights reserved.