ISSN:
1432-1106
Keywords:
Lateral geniculate nucleus
;
Alertness
;
Non-alertness
;
Sleep
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary 1. Cats with chronically implanted electrodes have been used to study the excitability of the lateral geniculate nucleus (LGN) during alertness, non-alertness and sleep. Excitability has been assessed by the amplitude of the field response in the LGN to electrical stimulation of the optic tract and by the amplitude of the antidromic response in the optic tract evoked by stimulating the LGN. 2. Changes in responsiveness associated with eye movements in the awake animal have been avoided. The change from the alert state to the non-alert state is accompanied by a decrease in the excitability of both the LGN cells and the optic tract nerve endings. 3. Postsynaptic excitability decreases further in slow-wave (SW) sleep but during low-voltage-fast-activity (LVF) sleep it returns to a level that is intermediate between that of alertness and non-alertness. During the ponto-geniculooccipital (PGO) waves of LVF sleep excitability is phasically enhanced to above the alert level. 4. Presynaptic excitability during SW sleep and LVF sleep in the intervals between the PGO waves is less than during non-alertness, but during the waves it returns to the alert level. 5. Our findings indicate that the optic tract endings are tonically depolarized in the alert animal and that the depolarization is reduced in non-alertness and reduced further in sleep. Depolarization is phasically enhanced during the PGO waves. 6. It is suggested that the LGN may be the first site on the visual pathway at which information is modified according to the animal's state of consciousness.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00235052
Permalink
