Sex Sleep Eat Drink Dream (31 page)

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 "
In this way ... the circadian pacemaker":
T. A. Wehr, "A clock for all seasons' in the human brain," in R. M. Buijs et al., eds.,
Progress in Brain Research
111 (1996).
So sensitive are these pacemakers:
The following draws on Foster and Kreitzman,
Rhythms of Life,
11.
special light-sensitive cells:
M. S. Freedman et al., "Regulation of mammalian circadian behavior by non-rod, non-cone, ocular photoreceptors,"
Science
284, 502–4 (1999); D. M. Berson et al., "Phototransduction by retinal ganglion cells that set the circadian clock,"
Science
295, 1070–73 (2002); I. Provencio, "Photoreceptive net in the mammalian retina,"
Nature
415, 493 (2002); S. Hattar et al., "Melanopsin-containing retinal ganglion cells: architecture, projections, and intrinsic photosensitivity,"
Science
295, 1065–68 (2002); I. Provencio et al., "A novel human opsin in the inner retina,"
Journal of Neuroscience 20,
600–605 (2000); R. G. Foster, "Bright blue times,"
Nature
433, 698–99 (2005); Z. Melyan et al., "Addition of human melanopsin renders mammalian cells photoresponsive,"
Nature
433, 741–45 (2005); D. M. Dacey et al., "Melanopsin-expressing ganglion cells in primate retina signal colour and irradiance and project to the LGN,"
Nature
433, 749–51(2005).

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As Emerson wrote:
Ralph Waldo Emerson, "Circles," in
Essays and Poems
(London: Everyman Paperback Classics, 1992), 147.
the true average daily temperature:
P. A. Mackowiak et al., "A critical appraisal of 98.6 degrees F, the upper limit of the normal body temperature, and other legacies of Carl Reinhold August Wunderlich,"
Journal of the American Medical Association
268, 1578–80 (1992).
Our knack for holding steady:
The following information on homeostasis is from Foster and Kreitzman,
Rhythms of Life,
53–54.
An intricate and diverse network:
Catherine Rivier Laboratory Web site,
www.salk.edu/LABS/pbl-cr/02_Research.html
, retrieved March 11, 2006.
our set-points aren't set at all:
The following discussion of circadian rhythms in body function comes from Wehr, "A clock for all seasons' in the human brain"; T. Reilly et al.,
Biological Rhythms and Exercise
(New York: Oxford University Press, 1997), 50; Y. Watanabe et al., "Thousands of blood pressure and heart rate measurements at fixed clock hours may mislead,"
Neuroendocrinology Letters
24:5, 339–40 (2003); D. A. Conroy et al., "Daily rhythm of cerebral blood flow velocity,"
Journal of Circadian Rhythms
3:3, DOI: 10.1186/1740-3391-3-3 (2005); W.J.M. Hrushesky, "Timing is everything,"
The Sciences,
July/August 1994, 32–37; John Palmer,
The Living Clock
(New York: Oxford University Press, 2002); Foster and Kreitzman,
Rhythms of Life,
10–21.

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Some scientists even argue:
Foster and Kreitzman,
Rhythms of Life,
71.
The rest of us can use:
Foster and Kreitzman,
Rhythms of Life,
11; Smolensky and Lamberg,
The Body Clock Guide to Better Health,
5–12; Hrushesky, "Timing is everything."
So pervasive is the influence:
J. Arendt, "Biological rhythms: the science of chronobiology,"
journal of the Royal College of Physicians of London
32, 27–35 (1998).

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These clusters of ... neurons:
P. L. Lowrey and J. S. Takahashi, "Mammalian circadian biology: elucidating genome-wide levels of temporal organization,"
Annual Review of Genomics and Human Genetics
5, 407–41 (2004).
In one 2004 study, researchers:
S.-H. Yoo et al., "Period2: luciferase real-time reporting of circadian dynamics reveals persistent circadian oscillations in mouse peripheral tissues,"
Proceedings of the National Academy of Sciences
101, 5339–46 (2004).
Though the master clock:
S. Yamazaki et al., "Resetting central and peripheral circadian oscillators in transgenic rats,"
Science
288, 682–85 (2000).

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Louis Ptáček and his colleagues:
C. R. Jones et al., "Familial advanced sleep-phase syndrome: a short-period circadian rhythm variant in humans,"
Nature Medicine
5:9, 1062 (1999); K. L. Toh et al., "An h
Per2
phosphorylation site mutation in familial advanced sleep phase syndrome,"
Science
291, 1040–43 (2001).
British scientists have shown:
S. Archer et al., "A length polymorphism in the circadian clock gene
Per
3 is linked to delayed sleep phase syndrome and extreme diurnal preference,"
Sleep
26:4, 413–15 (2003).
A team of scientists gave:
D. Katzenberg, "A clock polymorphism associated with human diurnal preference,"
Sleep
21:6, 568–76 (1998).
"
It seems that our parents":
C. M. Singer and A. J. Lewy, "Does our DNA determine when we sleep?,"
Nature Medicine
5, 983 (1999).
When Till Roenneberg studied:
Till Roenneberg, "A marker for the end of adolescence,"
Current Biology
14:24, R1038–39 (2004).

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Research by Roenneberg suggests:
Till Roenneberg, personal communication, September 8, 2006; Roenneberg et al., "Life between clocks."
Bach loved coffee:
S. M. Somani and P. Gupta, "Caffeine: a new look at an age-old drug,"
International Journal of Clinical Pharmacology, Therapeutics, and Toxicology
26, 521–33 (1988).
Two hundred years ago:
Samuel Hahnemann,
Der Kaffee in seinen Wir-kungen
(Leipzig, 1803), quoted in Bennett Alan Weinberg and Bonnie K. Bealer,
The World of Caffeine
(New York: Routledge, 2002), 119.
More than 80 percent:
Jack James,
Understanding Caffeine
(Thousand Oaks, Calif.: Sage Publications, 1997); Laura Juliano, personal communication, October 2006.

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Members of the Achuar Jivaro tribe:
W. H. Lewis et al., "Ritualistic use of the holly
Ilex guayusa
by Amazonian Jivaro Indians,"
Journal of Ethno-pharmacology
33:1–2, 25–30 (1991).
Czeisler and his team at Harvard:
J. K. Wyatt et al., "Low-dose repeated caffeine administration for circadian-phase-dependent performance degradation during extended wakefulness,"
Sleep
27, 374–81 (2004). The study was designed to find the best strategy for boosting and sustaining alertness among workers who have to stay awake for long hours—for example, doctors and long-distance truck drivers.
Just why caffeine has:
Jean-Marie Vaugeois, "Positive feedback from coffee,"
Nature
418, 734–36 (2002).
Within fifteen to twenty minutes:
J. Blanchard and S.J.A. Sawers, "The absolute bioavailability of caffeine in man,"
European Journal of Clinical Pharmacology
24, 93–98 (1983).
Caffeine enhances alertness:
J. W. Daly et al., "The role of adenosine receptors in the central action of caffeine," in B. S. Gupta and U. Gupta, eds.,
Caffeine and Behavior: Current Views and Research Trends
(Boca Raton, Fla.: CRC Press, 1999), 1–16.

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Whether it actually perks up:
H.P.A. Van Dongen et al., "Caffeine eliminates psychomotor vigilance deficits from sleep inertia,"
Sleep
24:7, 813–19 (2001); L. M. Juliano and R. R. Griffiths, "A critical review of caffeine withdrawal: empirical validation of symptoms and signs, incidence, severity, and associated features,"
Psychopharmacology
176, 1–29 (2004).
In 2005, a team of Austrian scientists:
F. Koppelstatter et al., "Influence of caffeine excess on activation patterns in verbal working memory," scientific poster at the Radiological Society of North America annual meeting, November 2005.
There are naysayers, however:
Juliano and Griffiths, "A critical review of caffeine withdrawal."

2. MAKING SENSE

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Now smell is regarded:
Rainer W. Friedrich, "Odorant receptors make scents,"
Nature
430, 511–12 (2004).
Our thresholds for detection of many odors:
J. A. Gottfried, "Smell: central nervous processing," in'T. Hummel and A. Welge-Liissen, eds.,
Taste and Smell: An Update (Advances in Otorhinolaryngology)
(Basel, Switzerland: Karger, 2006), 44–69; Jay Gottfried, personal communication, September 2006.
Millions of olfactory nerve endings:
Information about the olfactory system is from Z. Zou et al., "Odor maps in the olfactory cortex,"
Proceedings of the National Academy of Sciences
102:21, 7724–29 (2005); Z. Zou and L. B. Buck, "Combinatorial effects of odorant mixes in olfactory cortex,"
Science
311, 1477–81 (2006); R. Ranganathan and L. B. Buck, "Olfactory axon pathfinding: who is the pied piper?,"
Neuron
35:4, 599–600 (2002).
The character of a smell:
A. K. Anderson et al., "Dissociated neural representations of intensity and valence in human olfaction,"
Nature Neuroscience
6:2, 196–202 (2003); Stephan Hamann, "Nosing in on the emotional brain,"
Nature Neuroscience
6, 106–8 (2003).
Its strength (how pungent?):
T. W. Buchanan et al., "A specific role for the human amygdala in olfactory memory,"
Learning and Memory
10:5, 319–25 (2003); Jay Gottfried, personal communication, September 2006.
A French study in 2005:
J. Plailly, "Involvement of right piriform cortex in olfactory familiarity judgments,"
Neuroimage
24, 1032–41 (2005).

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As one researcher said:
Tim Jacob of Cardiff University; see
www.cf.ac.uk/biosi/staff/jacob/teaching/sensory/taste.html
and
www.cardiff.ac.uk/biosi/staff/jacob/index.html.
Scientists have found that olfactory stimuli:
S. Chu and J. J. Downes, "Odour-evoked autobiographical memories: psychological investigations of the Proustian phenomena,"
Chemical Senses
25, 111–16 (2000).
And they fall away less rapidly:
C. Miles and R. Jenkins, "Recency and suffix effects with serial recall of odours,"
Memory
8:3, 195–206 (2000).
Smell memories endure:
Zou et al., "Odor maps in the olfactory cortex"; Ranganathan and Buck, "Olfactory axon pathfinding"; M. Pines, "The memory of smells," in
Seeing, Hearing, and Smelling the World: A Report from the Howard Hughes Medical Institute,
at
www.hhmi.org/senses/d140.html
, retrieved March 25, 2005.
Small and her colleagues ... discovered:
D. M. Small et al., "Differential neural responses evoked by orthonasal versus retronasal odorant perception in humans,"
Neuron
47, 593–605 (2005).

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 "
A key fact about":
G. M. Shepherd, "Smell images and the flavour system in the human brain,"
Nature
406, 316–21 (2006).
Though some taste cells:
D. V. Smith and R. R Margolskee, "Making sense of taste,"
Scientific American,
March 2001, 32–39.
Each bud possesses up to one hundred:
Bernd Lindemann, "Receptors and transduction in taste,"
Nature
413, 219–25 (2001).

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Even temperature enters the picture:
A. Cruz and B. G. Green, "Thermal stimulation of taste,"
Nature
403, 889–92 (2000).
In 2005, a team of researchers:
K. Talavera et al., "Heat activation of TRPM5 underlies thermal sensitivity of sweet taste,"
Nature
438, 1022–25 (2005).
as Emerson described it:
Ralph Waldo Emerson,
Essays and English Traits,
vol. 5, ch. 2, "Voyage to England" (Harvard Classics, 1909–14),
www.bartleby.com/5/202.html.
"
Virtually every plant":
Paul Breslin, personal communication, October 2006.
Scientists recently pinpointed:
U.-K. Kim et al., "Genetics of human taste perception,"
Journal of Dental Research
83:6, 448–53 (2004); B. Bufe et al., "The molecular basis of individual differences in phenylthiocarbamide and propylthiouracil bitterness perception,"
Current Biology
15:4, 322–27 (2005); A. Caicedo and'S. D. Roper, "Taste receptor cells that discriminate between bitter stimuli,"
Science
291, 1557–60 (2001).

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Breslin has found:
M. A. Sandell and P.A.S. Breslin, "Variability in a taste receptor gene determines whether we taste toxins in food"; Paul Breslin, personal communication, September 6, 2006.

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Our early mammalian ancestors saw:
N. J. Dominy and P. Lucas, "The ecological importance of trichromatic colour vision in primates,"
Nature
410, 363–66 (2001).
This enhanced color vision:
L. A. Isbell, "Snakes as agents of evolutionary change in primate brains,"
Journal of Human Evolution
51, 1–35 (2006).
New research hints at individual variations:
B. C. Verrelli and'S. A. Tish-koff, "Signatures of selection and gene conversion associated with human color vision variation,"
American Journal of Human Genetics
75, 363–75 (2004).
Some percentage of women may experience:
K. Jameson et al., "Richer color experience in observers with multiple photopigment opsin genes,"
Psychonomic Bulletin and Review
8:2, 244–61 (2001).
As the great psychologist William James said:
William James,
Principles of Psychology,
vol. 1 (1890),
http://psychcIassics.yorku.ca/james/principles/prin9.htm.