Sleep and waking activity of pontine gigantocellular field neurons

Abstract

The sleep and waking discharge of pontine gigantocellular field’ units was studied in unrestrained cats. Three cell types were distinguished on the basis of discharge rate. Type 1 had no spontaneous activity during quiet waking and sleep, discharging only during movements. Type 2 had high rates of tonic activity during both quiet waking and sleep. Type 3 had low activity rates during quiet waking and slow-wave sleep, but discharged in bursts during both waking movements and rapid eye movement (REM) sleep. Units with augmented discharge restricted to REM sleep were not observed. All pontine gigantocellular field cells discharged rapidly during specific waking movements at rates exceeding mean REM sleep rates. Among type 2 and 3 cells, REM sleep and active waking discharge rates were correlated, with cells that discharged rapidly in REM sleep also showing high rates during active waking. Adaptation to head restraint reduced waking motor activity and the correlated pontine gigantocellular field discharge, yielding a reduced estimate of waking discharge rates. Our results are consistent with an hypothesis of pontine gigantocellular field unit involvement in the motor activation common to both waking and REM sleep, but are not consistent with an executive role for these neurons in the triggering of the REM sleep state.

Fig. 1.

A type 1 (NSA) cell. Abbreviations for this and succeeding figures: EEG, electroencephalogram from sensorimotor cortex; EOG, electrooculogram; LGN, lateral geniculate nucleus activity; EMG, dorsal neck muscle electromyogram. The unit channel displays the pulse output of a window discriminator

Fig. 1.

A type 1 (NSA) cell. Abbreviations for this and succeeding figures: EEG, electroencephalogram from sensorimotor cortex; EOG, electrooculogram; LGN, lateral geniculate nucleus activity; EMG, dorsal neck muscle electromyogram. The unit channel displays the pulse output of a window discriminator

Fig. 2.

A type 2 cell. See Fig, 1 for abbreviations.

Fig. 2.

A type 2 cell. See Fig, 1 for abbreviations.

Fig. 3.

A type 3 cell. See Fig. 1 for abbreviations.

Fig. 3.

A type 3 cell. See Fig. 1 for abbreviations.

Fig. 4.

Stereotaxic positions of FTG cells mapped on sagittal sections 1.2 (top) or 1.9 (bottom) mm lateral to the midline. Type 1 cells are represented by triangles, type 2 by squares, and type 3 by circles. A-P— millimeters anterior or posterior to stereotaxic zero, H—millimeters ventral to Stereotaxic zero, 6—abducens nucleus, 7G— genu of the facial nerve, CAE—nucleus coeruleus, FTC—central tegmental field, FTG—gigantocellular tegmental field, FTL—lateral tegmental field, FTM—magno-cellular tegmental field, IOD—dorsal accessory nucleus of the inferior olive, IOMC— medial accessory nucleus of the inferior olive, caudal division, IOMR—medial accessory nucleus of the inferior olive, rostral division, IOP—principal nucleus of the inferior olive, PH—nucleus praepositus hypoglossi, TB—trapezoid body, TRC—tegmental reticular nucleus, central division, VMN—medial vestibular nucleus. to that of the maximum waking rates was 0.41. Comparison of the geometric mean of average REM rates with that of the minimum waking rates would produce a selectivity ratio of 120.15.

Fig. 5.

Representative electrode tracks. A—Coronal section at PS.2. Two electrode tracks are visible on left portion of slide. B—Coronal section at P7.7. A bilateral pair of electrode tracks is visible. C—Sagittal section at L1.2. A pair of electrode tracks and their terminal lesions are visible. D—Sagittal section at L1.2. An electrode track with two lesions. Calibration lines, 2 mm.

Fig. 6.

Activity of FTG unit during grooming. This cell fired during leftward head movements but not during vertical movements. Unit’s discharge rate was a function of the type of movements occurring during sampling periods.

Fig. 7.

Two continuous samples of the amplified unit recording of a type 3 cell. The upper portion is an 11-min waking sample, and the lower is a 4-min recording spanning an entire REM sleep period. Note the variability of rate. “Average” waking rates would be a function of the cat’s behavior during the sample period.

Fig. 8.

Effect of restraint on FTG unit activity. A—During first few minutes of restraint, cat struggles and correlated unit activity occurs. B—After several minutes, intensity of unit activity decreases together with motor activity. C—As cat becomes adapted to restraint, unit activity is maintained at low level.