Synchronization of low-frequency rhythms in corticothalamic networks
Section snippets
Experimental animals
Experiments were performed on 39 adult cats. Of those, 12 were anaesthetized with urethane (1.8 g/kg, i.p.) and 27 with ketamine-xylazine (10–15 mg/kg and 2–3 mg/kg, i.m.). All wounds and pressure points were infiltrated with lidocaine. Additional doses of urethane (0.2–0.5 g/kg, i.p.), ketamine-xylazine (2–3 mg/kg; 0.4–0.6 mg/kg) or nitrous oxide were used at the earliest signs of diminished amplitude and/or increased frequency of EEG waves in order to maintain a picture of deep anaesthesia
Database and neuronal identification
Results are based on simultaneous extracellular recordings from 142 groups of cells making a total of 156 cortical cells from the pericruciate region, 318 RE cells from the rostral pole, rostrolateral and lateral regions (including the peri-VL and the peri-VP sectors), and 184 TC cells from the VL and the VP nucleus. Each group of simultaneously recorded cells had one to three cortical cells, two to five RE cells, and one to three TC cells. Several groups (n=51) consisted of neurons from both
Discussion
Our data show that: (i) high-amplitude, low-frequency oscillations are associated with highly coherent activities of cortical, RE and TC neurons; (ii) under urethane and ketamine-xylazine anaesthesia, cortical and RE cells mostly display spontaneous and synchronized slow oscillations between 0.3 and 0.9 Hz, while TC cells prevalently show clock-like delta oscillations at 1–4 Hz; and (iii) cortical stimulation is effective in entraining and synchronizing RE and TC cells within the frequency of
Conclusion
The only sleep oscillation in which the rhythmicity and phase between cells is kept relatively constant is the slow oscillation. The other two, thalamic-generated sleep oscillations (spindling and clock-like delta) display continuous variations in frequency and in relations between cells, rendering less homogeneous the population samples being recorded and therefore making it necessary to record from larger populations of neurons.
Acknowledgements
This work was supported by grant MT-3689 from the Medical Research Council of Canada. D.C. is a graduate student in this laboratory, partially supported by the Savoy Foundation. We thank P. Giguère and D. Drolet for technical assistance.
References (26)
- et al.
Evaluation of neuronal connectivity: sensitivity of cross-correlation
Brain Res.
(1985) - et al.
Delta frequency (1–4 Hz) oscillations of perigeniculate thalamic neurons and their modulation by light
Neuroscience
(1992) Neurotransmitter actions in the thalamus and cerebral cortex and their role in neuromodulation of thalamocortical activity
Prog. Neurobiol.
(1992)- et al.
Intracellular evidence for incompatibility between spindle and delta oscillations in thalamocortical neurons of cat
Neuroscience
(1992) - et al.
The interpretation of potential waves in the cortex
J. Physiol., Lond.
(1934) - et al.
Dynamics of neuronal firing correlation: modulation of “effective connectivity”
J. Neurophysiol.
(1989) - et al.
Short- and long-range neuronal synchronization of the slow (<1 Hz) cortical oscillation
J. Neurophysiol.
(1995) - et al.
Disconnection of intracortical synaptic linkages disrupts synchronization of a slow oscillation
J. Neurosci.
(1995) - et al.
Mechanisms of oscillatory activity in guinea-pig nucleus reticularis thalami in vitro: A mammalian pacemaker
J. Physiol., Lond.
(1993) - et al.
Electrophysiological properties of cat reticular thalamic neurones in vivo
J. Physiol., Lond.
(1993)