Maurice B. Sterman

Sleep suppression after basal forebrain lesions in the cat.

Large bilateral preoptic lesions produced complete sleeplessness in two cats. In eight additional cats, similar but smaller lesions resulted in a significant reduction of quiet (slow-wave) sleep by 55 to 73 percent, and active (paradoxical) sleep by 80 to 100 percent. These values were determined by pre- and postlesion 22-hour continuous observations. Complete sleeplessness was followed by lethal exhaustion within a few days, whereas incomplete sleeplessness persisted at maximum levels for 2 to 3 weeks. The suppression of sleep was characterized by a gradual onset during the first 1 to 2 weeks, and a complete or partial recovery after 6 to 8 weeks. The severity of sleep suppression was found to be related to the size and localization of lesions placed specifically within the preoptic area and not to transient disturbances in feeding and temperature regulation.

Instrumental Conditioning of Sensorimotor Cortex EEG Spindles in the Waking Cat

Abstract The spontaneous occurrence of a 12–20 cps slow-wave spindle recorded from sensorimotor cortex in waking food-deprived cats was systematically reinforced by presentation of milk. This specific EEG pattern was detected by a filter-relay system, the discharge of which was capable of activating the feeding apparatus within an experimental behavior chamber. After several sessions, with 50 reinforcements per session, this sensorimotor rhythm appeared more frequently and demonstrated a regular temporal pattern of occurrence. The consistent behavioral correlate of this EEG response was the assumption of stereotyped postures, characterized by a complete cessation of spontaneous activity. Withholding milk reinforcement resulted in a considerable enhancement of the sensorimotor rhythm during the initial period of extinction. Such changes were not observed, however, when other patterns of sensorimotor cortex electrical activity were reinforced in a similar manner. We conclude that, in the present experiments, it was possible to establish a conditioned sensorimotor cortex slow-wave response of the instrumental type, and that this sensorimotor rhythm has functional significance as a conditioned “central state” related to the inhibition of phasic motor behavior.

Afferent vagal stimulation: Neurographic correlates of induced eeg synchronization and desynchronization

Summary o 1. Cortical synchronization and desynchronization were induced by afferent cervical vagal stimulation in the cat. 2. By simultaneously recording the vagal neurogram and the induced EEG responses, it was determined that rapidly conducted vagal potentials were associated with EEG synchronization, while potentials conducted at approximately 15 m/sec were correlated with EEG desynchronization. 3. The specific factor which determined the nature of the EEG response was whether synchronogenic or desynchronogenic vagal afferent fibers were stimulated and not the frequency of stimulation. 4. Following supranodose transection of the vagus nerve, the sensory elements remaining in the vagus could be stimulated to induce a vagal neurogram which contained the potential complexes seen in the intact nerve and which had been correlated with the induced EEG responses. A histologic analysis of intact and transected vagi confirmed the neurographic findings. 5. The patterns of the induced synchronization which occur as a result of afferent vagal stimulation are similar to those which occur spontaneously or during quiet sleep in the unrestrained cat. It was concluded that the vagal afferent system is comprised of fiber groups which are able to initiate and maintain either synchronization or desynchronization of the EEG and that these fiber groups are both functionally and structurally discrete.

Facilitation of spindle-burst sleep by conditioning of electroencephalographic activity while awake.

A slow-wave electroencephalographic rhythm recorded from the sensorimotor cortex of the waking cat has been correlated behaviorally with the suppression of movement. Facilitation of this rhythm through conditioning selectively enhances a similar pattern recorded during sleep, the familiar spindle burst. The training also produced longer epochs of undisturbed sleep. The specific neural mechanism manipulated during wakefulness appears to function also in sleep and to be involved with the regulation of phasic motor behavior.

Cortical-subcortical EEG correlates of suppressed motor behavior during sleep and waking in the cat ☆

Abstract During suppression of motor behavior in cats, a 12–16 c/sec EEG activity generally localized over the sensorimotor cortex has been described previously and termed the sensorimotor rhythm (SMR). It has recently been shown that SMR conditioning can alter EEG spindle activity of slow wave or quiet sleep. The SMR can also appear in non-phasic portions of rapid eye movements or active sleep. Therefore, the purpose of this study was to examine the SMR and sleep spindle phenomena in detail. Cortical and subcortical EEG data were recorded from the somatosensory, motor and visual systems during sleep and wakefulness. EEG tracings were examined for any EEG rhythms or activity characteristics of any behavioral state or location or both. These results were tabled according to location and state and were quantified. States were defined by using EEG from both the sensorimotor and visual cortex areas, electrooculogram and behavioral observations. The SMR was found primarily within the somatosensory system in nucleus ventralis posterior lateralis (VPL) and its primary cortical projection area, the postcruciate gyrus. It occurred in these structures during the absence of phasic motor activity in both the alert animal and in active sleep. Centrum medianum (CM) also possessed a low voltage SMR correlate in the alert animal. The subcortical correlates of the SMR were not present during quiet sleep. In this state, spindle bursts were located primarily within the motor system in ventralis lateralis (VL) and its cortical projections area, the precruciate gyrus. The cerebral peduncles and CM also displayed sleep spindle activity. The VL-motor cortex spindle bursts showed a marked increase in frequency of occurrence in the 1 min interval preceding active sleep. It was proposed that the generators for the SMR and sleep spindle phenomena are probably located at the thalamic level. Although their thalamocortical projections and correlated behavioral states are relatively discrete, their functional origins both appear to reside in a mechanism concerned with the specific suppression of phasic motor activity.

Post-reinforcement EEG synchronization during alimentary behavior

Abstract 1. 1. Cats were trained to manipulate a lever which delivered small amounts of liquid food (milk-broth) from a dispenser. Discrete periods of EEG synchronization were observed coincident to the development of this simple instrumental response. 2. 2. Slow wave synchronous activity in the EEG replaced low voltage fast activity when the animals received positive reinforcement. These “spindles” did not appear if the animals were not reinforced. They could be abolished by thalamic electrical stimulation at arousal parameters or by novel auditory stimuli, even though these internal and external stimuli were not intense enough to alter the behaving pattern of the cats in the instrumental situation. 3. 3. Water substituted for the milk-broth reward in a food deprived animal resulted in a disappearance of the post-reinforcement cortical synchronization. 4. 4. The EEG synchronization previously described during prolonged alimentary behavior was also observed in our animals under these circumstances. 5. 5. The presentation of a sensory stimulus in association with the delivery of larger amounts of food resulted in the classical conditioning of this synchronization. Extinction of the conditioned synchronization was also achieved. The prolonged presentation of a non-reinforced CS resulted in the reappearance of a synchronization, which, in this case, was associated with the extinction of an alimentary response.

Cortical and subcortical patterns of response to afferent vagal stimulation

Cortical and subcortical patterns of activity were studied upon electrical stimulation of the cut central end of the cervical vagus nerve in acutely prepared adult cats. The effects of different frequencies and voltages of afferent vagal stimulation were studied while the duration of the stimulus pulses was kept constant (0.75 msec). High-frequency (> 70/sec) low voltage (< 3v) stimulation resulted in the induction of cortical EEG synchronization, while all other combinations of frequency and voltage gave rise to cortical activation. Subcortical structures responded in a manner consistent with the cortical observations. The cerebral cortex and thalamic nuclei responded to synchronogenic vagal afferent stimulus parameters only after an initial latent period, while the hippocampus responded immediately. All responses were bilaterally equivalent and could be induced by either vagus nerve. Severance of both sympathetic trunks and vagi and transection of the neuraxis at the spinomedullary junction indicated that the central responses were neurogenic in origin. These and other studies presently in progress offer convincing evidence that the different cortical responses (synchronization or desynchronization) observed by various investigators from stimulation of the central end of the cervical vagus nerve result from the differential stimulation of specific afferent fiber systems within that nerve.

Multiband topographic EEG analysis of a simulated visuomotor aviation task.

Topographic EEG spectral magnitudes from 19 cortical sites were compared in 15 adult male subjects during performance of a simulated flight task and during control conditions which attempted to separately evaluate functional components of this task. Four conditions were studied, including eyes closed, a visual control, a motor control and a simulated landing task requiring integration of both visual and motor components. Each condition was repeated twice in a counterbalanced replicated measures design. A linked-ear EEG reference was used and spectral magnitudes calculated for 6 frequency bands. Decisions concerning band width and spectral transform were empirically determined. Findings indicated no significant differences between replications. A broad posterior cortical suppression of all frequencies was observed in the visual control condition. Anterior sites were affected only in the 7-12 Hz range. Additional suppression was seen during the motor control condition but limited to frontocentral sites in the 11-13 Hz band. The flight task, however, produced a further suppression at centroparietal cortex in the 9-13 Hz range. The extraction of both attentional and motor components from this task suggests that the parietal EEG activation was specific to cognitive processing.

Inhibition of a monosynaptic reflex by electrical stimulation of the basal forebrain or the orbital gyrus in the cat.

Der monosynaptische Reflex des Nervus massetericus, durch elektrische Reizung des Nucleus mesencephalicus des Trigeminus hervorgerufen und vom Nervus massetericus abgeleitet, konnte durch Reizung bestimmt umschriebener Gebiete des präoptischen basalen Telencephalons oder durch Reizung des Gyrus orbital im Katzen-Cortex effektiv gehemmt werden. Entsprechende Reizung der gleichen Hirngebiete führt zur Synchronisation des Elektrocorticogramms und ruft Schlaf hervor.

Forebrain inhibitory mechanisms: conditioning of basal forebrain induced EEG synchronization and sleep.

Abstract There is evidence suggesting that EEG synchronization and sleep are capable of becoming associated with specific sensory stimuli through the process of conditioning. In some preliminary experiments it was found that the EEG and behavioral patterns induced by basal forebrain stimulation could be evoked by a tone which had been paired in time with electrical stimulation of this area in the cat. The present experiments are concerned with a closer examination of this conditioning. Adult cats were surgically prepared for chronic study with stimulating electrodes lowered bilaterally into the basal forebrain synchronizing area and the intralaminar thalamic nuclei with recording electrodes placed diffusely in the calvarium over the cerebral cortex. After recovery, these animals were placed in an observation chamber and presented with a fixed interval conditioning sequence of tone followed by basal forebrain stimulation. A conditioned EEG synchronization accompanied by behavioral manifestations of sleep developed rapidly to the tone when either low- (5 cycle/sec) or high- (150 cycle/sec) frequency stimulation in the basal forebrain was used as the unconditioned stimulus. Generalization of the conditioned response was observed when tone frequencies were changed, and discrimination developed in relation to a different tone paired with high-frequency (alerting) stimulation of intralaminar thalamic nuclei. A relationship between the frequency of basal forebrain stimulation and that of the conditioned EEG synchronization was also observed. These findings support the conclusion that important functional connections exist between the basal forebrain synchronizing areas and the cerebral cortex.