Biological Rhythms

1. Biological Rhythms

2. What are Body Rhythms? • Body rhythms are biological processes that show cyclical variation over time…ranging from hours to years and reflect the influence of the earths rotation upon us… it's living inhabitants, along with plants and animals. • There are three rhythms that we will focus our attention upon throughout this module. • Circadian Infradian, and ultradian biological rhythms.

3. Body Rhythms (cont’d)… • Circadian rhythms: (circa = approx and diem = day) go over 24hrs. Humans demonstrate a series of changes including temperature heart respiration and metabolism over this period. We (psychologists) are most interested in the sleep-wake cycle. • Ultradian rhythms: (Meaning less than one day) Sleep is a good example of an ultradian rhythm, as you sleep you pass through differing stages of sleep (e.g. light and deep sleep lasting about 90 minutes.)

4. Body Rhythms (cont’d)… • Infradian rhythm: (meaning more than 1 day). An example of a infradian rhythm would be a woman's menstrual cycle which lasts for 28 days. • A circannial cycle occurs yearly/annually. An example of this would be non human animals hibernation and waking patterns.

5. Research Studies into Circadian Rhythms. • If bodily rhythms show a similar daily pattern for people with different lifestyles it would seem these rhythms are ‘part of our nature’ and not our ‘upbringing or nurture’ • So..the next question would be is whether they are natural and triggered internally or whether they rely upon external cues in the environment.

6. Research Studies into Circadian Rhythms. • Siffre (1975) Spent 6 months inside a cave and found that his natural Circadian rhythm was just over 24 hr, but would sometimes change to 48 hr. • There were no zeitgebers such as natural light or sounds. He had no idea what time it was, although he did have contact with outside world via telephone. He had food and drink and so on. His behaviour such as when he slept/woke and when he ate his meals was monitored. From this study it was concluded our internal clock must have a 25-hr cycle and that our zeitgebers must reset the clock to our usual 24-hr day.

7. Research Studies into Circadian Rhythms… • Another way to test circadian rhythms is to alter our environmental cues. • Folkard (1985) 12 participants lived in ‘temporal isolation’ for 3 weeks…isolated from natural light and other time cues. They agreed to go to bed at 11.45 pm and get up when it said 7.45 am. The clock initially ran to time but gradually quickened until it indicated a passing of 24 hr for 22 hr. All but 1 of the participants kept pace with the clock…thus demonstrating a strong free-running rhythm.

8. Evaluation of Research Studies into Circadian Rhythms… • Participants were isolated from exogenous cues (environmental) and we know these have an effect upon our circadian rhythms….but were not isolated from artificial light...it is now known these too can have an effect!! • Individual differences- Are you a morning or evening person? • Duffy et al (2000) found early risers prefer 6 am-10 pm cycles and late starters prefer 10 am - 1 am cycles.

9. Evaluation of Research Studies into Circadian Rhythms… • What everyday application could we gain from studies such as these…(how useful is this stuff really???) • Deciding the best time to study. • Taking medication for serious medical conditions. (chronotherapeutics)

10. Research studies into infradian rhythms. • Monthly cycles...the function of this cycle is to regulate ovulation.

11. Research Studies into Infradian Rhythms. • Seasonal Affective Disorder (SAD). Research has shown that the hormone melatonin is secreted when it is dark...the more darkness...the more melatonin. This leads to severe disruption in mood.

12. Evaluation of Studies into Infradian Rhythms. • Menstrual cycles can also be disrupted by other factors as well as hormones...research has shown that when a several women live in a house together and they are not taking oral contraceptives they tend to fall in line with each other and menstruate at the same time this be possibly due to pheromones being released chemically and giving a scent. • SAD a greater understanding of this condition has lead to successful therapies such as phototherapy- very strong lights to increase the level of melatonin.

13. Research Studies into Ultradian Rhythms • These are rhythmic cycles with a period of less than one day. Examples include levels of alertness throughout the day and the cycle of brain activity during sleep. • NREM and REM: There are 4 stages (1 & 2) which are shallow into deep sleep/slow wave sleep (3 & 4). These cycles continue throughout the night with (SWS) becoming shorter and REM becoming longer as the night progresses. Cycles last for approx 60 min in early infancy and 90 min in adolescence. • The use of an electroencephalogram (EEG) can show the electrical activity of the brain. There are different patterns of activity at different times during sleep (Rechtschaffen & Kales, 1968).

14. Circadian Rhythms • Circadian = diurnal + nocturnal • Zeitgebers and the SCN: Biological clock • Altering light/dark cycles produces phase shift and entrainment

15. Suprachiasmatic Nucleus (SCN) SCN - main control center for sleep and temperature circadian rhythms

18. What sets the Clock? Zeitgeber: a stimulus that resets the biological clock (e.g. bright light, exercise, temperature)

19. Evidence for the SCN as biological clock • Free-running rhythms and the 24+ hour period • SCN lesions disrupt circadian rhythms • SCN tissue maintained in vitro retains cyclicity • Transplanted SCNs set rhythms of donor animal • Recall the pathway in the visual system from retina to SCN: These retinal ganglion cells contain a photopigment, melanopsin, and are light sensitive

20. The Role of Endogenous Pacemakers and Exogenous Zeitgebers. • The main pacemaker for endogenous (internal) rhythms is the suprachiasmatic nucleus (SCN). This is a small group of cells located in the area of the brain called the hypothalamus. Its called the SCN because it lies just above the optic chiasm, therefore it can receive information directly from the eye and the rhythm can be rest by the amount of light entering the eye.

21. The Role of Endogenous Pacemakers and Exogenous Zeitgebers (cont’d)…. Stimulation of the pineal gland produces the hormone melatonin (sleepy) When light levels are low we produce more melatonin.. • The way the SCN works is as follows: Production of protein for number of hours This rhythm then affects the sleep wake cycle via the pineal gland. Thelevel inhibits further production, again for a number of hours. The protein drops another level and the SCN starts producing the protein again.

22. The Role of Endogenous Pacemakers and Exogenous Zeitgebers (cont’d)…. • So what about exogenous (external) pacemakers??? • Light is considered to be the most dominant zeitgeber. (see..Miles et al 1977) • Opposing research also indicates that there are other factors that should be taken into consideration (see..Luce & Segal 1966) • Overall it appears the sleep-wake cycle is strongly dictated by endogenous pacemakers but we can override these cues. • It what circumstances might this happen?

23. The Role of Endogenous Pacemakers and Exogenous Zeitgebers Evaluation… • It is adaptive for endogenous rhythms to be rest by external cues so that animals are in tune with seasonal variations and day/night time. This idea of adaptive ness comes from evolutionary perspective that refers to the idea that behaviours which persist are more likely to promote ones survival. • It could be life threatening if we relied solely upon external cues, therefore we must not forget the significance of internal cues.

24. Optic nerve Pathways to SCN Optic chiasm Optic tract Lateral geniculate nucleus Optic radiation Primary visual cortex

25. Circadian Physiology • Circadian Rhythms • endogenous cycles • role of the suprachiasmatic nucleus • setting/resetting biological clocks • Sleep • why sleep? • stages of sleep • Dreaming • why dream?

26. Circadian Rhythms • Endogenous circadian rhythms • rhythms that last about a day • humans’ last around 24.2 h • Examples: • -activity • -temperature • -waking and sleeping • -secretion of hormones • -eating and drinking

28. What Resets the Clock? • Light • retinal ganglion cells send direct projections to the SCN • this provides information about light to the SCN • Melatonin • secreted from the pineal gland • increased levels of melatonin make you sleepy • melatonin can act on receptors in the SCN to phase-advance the • biological clock

29. Sleep

30. Neural Control of Sleep • Is sleep a passive process? • The cerveau isole’ of Bremer (1936): SWS only • The encephale isole’ and the RAS: normal sleep • Partial transections leaving the RAS intact • Ventrolateral Preoptic Area (VPA) triggers sleepiness and slow-wave sleep • Warming the basal forebrain induces slow-wave sleep: GABA on tuberomammillary nucl. • VPA receives input from thermoreceptors

31. More Neural Control • PGO waves in the EEG from implanted electrodes • Executive in the dorsolateral pons, called the peribrachial area. • Kainic acid lesions of peribrachial area reduce REM sleep • Carbachol, an ACh agonist, in ventral pons (medial pontine reticular formation) triggers REM phenomena.

32. The Sleep Cycle • Electronic recording: EEG, EOG, EMG • EEG patterns divide sleep into four stages: • 1: a waves, 8 - 12 Hz, low amplitude, moderate frequency, similar to drowsy wakefulness • 2: slower frequency, higher amplitude, plus • K complexes • Sleep spindles • 3: d waves appear, 1-2 Hz, large amplitude • 4: Dominated by d waves

33. EEG patterns b a 2k 3d 1 sec

34. EEG patterns... 4 d 1 sec

35. REM sleep phenomena • Stage 1 EEG: Paradoxical sleep • EOG (and corneal bulge) show frequent eye movements, as if scanning a visual field. • EMG shows loss of muscle tonus due to downward inhibition of a motor neurons, although muscles moving hands and feet may twitch. • Many brain structures function as if awake.

36. More REM phenomena • SNS is partially activated: Increases blood pressure, respiration, and heart rate. • Genital response • Narrative dreaming • CBF is high to visual cortex, low to inferior frontal cortex (Madsen, 1991) • Eye movements match dream events • One EEG waveform is unique to REM and wakeful scanning

37. Sleep: Stages

38. A Typical Night

39. After 11 days of total sleep deprivation

40. Research studies into Ultradian rhythms….

41. Effects of sleep deprivation • Sleep deprivation within a circadian cycle is followed by less sleep, not more • Internal desynchronization: free-running body temperature cycle and sleep-wake cycle may desynchronize.

42. So, what goes on in the brain in SWS? • Areas that  arousal  shut down. • Primary sensory areas also shut down. • Areas involved in memory consolidation and retrieval don’t shut down, but are isolated from sensory input.

43. So, what goes on in the brain in REM? • INCREASE in sensory integration, motor, limbic, and memory areas. • Why don’t we move, if motor areas are activated? • One brain area sends inhibitory input to the spinal cord to prevent movement. • Frontal cortex shuts down, disinhibiting limbic system.

44. Reticular formation (red) wakes the brain.Locus coeruleus (blue) inhibits muscles.Basal forebrain (yellow)  SWS.

45. Why Sleep? Repair and Restoration Theory • Sleep enables the body and brain to repair itself after working hard all day • Brain is ~3% of total body weight, but uses almost ¼ of the energy. • Going without sleep causes people to be irritable, dizzy, and to have hallucinations and impaired concentration • Sleep-deprived rats’ bodies work harder • BUT, how much we sleep does not depend on how much we worked that day

46. Who sleeps? • Mammals and birds • Opossums, sloths, bats: 19-20 hours daily • Cats, dogs, rodents: 12-15 hours daily • Ruminant herbivores: 2-3 hours daily • Reptiles, amphibians, fish, and insects have cycles of inactivity • Note that sleep time does not correlate with waking activity levels, but does relate to waking vulnerability.

47. Why Sleep? • Evolutionary Theory • we evolved to sleep so that we would conserve energy when we were least efficient • during sleep body temperature decreases • predicts that species will sleep different amounts depending on how much they must look for food and watch for predators

48. Dream research • External stimuli may be incorporated into a dream. • Dream events happen in real time. • Everyone dreams; recall depends on when in the sleep cycle you awaken. • Genital response is independent of dream content. • Sleep-walking and talking are non-REM.

49. Interpretation of dreams • Manifest content is symbolic of latent desires (Freud) • Activation-synthesis theory: cf. incorporation of external events into dreams. • Lucid dreams: Have you had one?

50. Why Dream? Facilitate problem solving ? Facilitate memory consolidation ? • Lots of REM sleep predicts better consolidation of emotional information. • Lots of SWS predicts better consolidation of motor tasks. • Lots of SWS+REM predicts better consolidation of perceptual information. • Patterns of activation of hippocampal neurons are repeated