Principles of

Organization
Circadian Rhythmicity
Thermoregulation
Saccadic Eye

Movement Generation
"Motor Tape" 25 hr oscillation in hypothalamic suprachiasmatic nucleus Thermogenic response (via somatic & autonomic N.S. and via Hypophyseal-thyroid endocrine output High frequency burst continues until there is a match between intended eye-position signal and actual eye-position signal.
Feedback not necessary

for rhythm

 Visual input resets rhythm ("Zeitgeber" function) but does not alter its free running period Cold receptors can trigger thermogenic response even though core body-temperature is normal Saccades are ballistic
Pattern generator IPSP + EPSP + Oscillator Rhythm can be reset by electrical stimulation of suprachiasmatic N. in rats Medullary vasomotor centre has some reciprocal inhibitory circuits which can explain some aspects of response. Pauser, burster and reference neurons and their interconnections are well described. Saccade generation well understood
Genetic control of pattern Individual variation in actual length of free-running period. Mutants without a clock known from Drosophila (?in man also) Sexual dimorphism of hypothalamic circuits: e.g. higher threshold for sweating in? E E Species-specific variation in saccade dynamics (e.g. birds have spiral oscillations during saccades)
Command Neuron or Hormone

(Neuromodulation)

 Melatonin is produced during night phase of the rhythm with wide effects on brain. TR. has widespread effects in brain Command neuron in superior colliculus map of motor-error. Activation of command neuron leads to saccade vector of magnitude appropriate to position in map.