Proprioceptive Stimuli Research Articles

External cue control of DRL performance in rats with septal lesions

Abstract Septally-lesioned, thalamically-lesioned, and normal animals were trained to bar-press on a DRL-20 schedule for food reinforcement. For half of the animals, a cue light signalled the end of the required delay during the first half of training. The light cue conditions were reversed for all animals in the last half of training. All animals decreased their rate of response during training, regardless of the presence or absence of the cue light. However, the septal animals, in contrast to the normal and thalamic animals, increased their reinforcement frequency only when the cue light was used. In addition, when the cue light was used, all animals had a bimodal distribution of inter-response times, with one mode at the shortest recorded delay and a mode at the 20-sec delay interval. When the cue light was not used, the thalamic and normal animals again had a bimodal distribution, while the septal animals had a unimodal distribution with the mode located at the shortest recorded delays. The results suggested that the cue light functioned as a discriminative cue for bar-pressing and secondly, as a reinforcing stimulus for behaviors which mediated the required delay. It was concluded that the septal deficit on DRL schedules results from a failure to utilize response-produced, proprioceptive stimuli as cues for bar-pressing.

Schizophrenic hallucinations and the transcephalic DC potential.

THE TRANSCEPHALIC direct current (TCDC) potential is the slowly changing aperiodic voltage recorded between the frontal and occipital emissary vein distributions on the midline surface of the head. 1-3 It now appears that a negative frontal shift reflects a lowered activation threshold of the subjacent frontal cortex, 4-6 and is related to the physiological substrate of the orienting reflex. 7 At an elementary level, a brief negative shift occurs when the subject attends to an exteroceptive or nonvestibular proprioceptive stimulus, and a positive shift is promoted by interoceptive stimuli. 2 Hunger and other externally oriented drive states promote a negative frontal baseline, and satiety states a positive one. 1,2,8 At a more complex functional level, anxiety increases the TCDC variance of a group without imparting a specific polarity to the potential. 2,8 An attempt to inhibit perception of an exteroceptive stimulus correlates

Anticipation and timing in human motor performance.

Recent evidence concerning the role of anticipation and timing in human motor performance is reviewed. Evidence generally indicates that anticipation and timing can be learned, and that there is substantial forgetting over retention intervals of up to 5 months. The spatial and temporal predictability of the stimuli appear to be the most potent determiners of anticipation, but response-produced proprioceptive stimulus traces may also provide a basis for more accurate timing. Changes in the nature of the stimulus predictability produce widely different response strategies, and after considerable practice, anticipated responses become automatic, freeing S to perform other tasks simultaneously. There has been a general lack of interest concerning both intraresponse timing and the motor variables determining anticipation.

Electro-clinical investigations on the role of proprioceptive stimuli in the onset and arrest of convulsive epileptic paroxysms.

SUMMARYA study was carried out on two cases of reflex epilepsy with hemiconvulsive seizures induced by proprioceptive stimulations (tuning fork vibrations and active and/or passive movements).A proprioceptive dissociation is shown to exist in reflex epilepsy, i.e. the seizures are induced only by certain proprioceptive stimuli (vibration or movement).It is assumed that the proprioceptive stimuli generated during the convulsive seizure intervene by a feedback mechanism. By means of this feedback mechanism the afferent proprioceptive impulses in the course of the seizure facilitate the cortical mechanisms of clonic transformation of the convulsive fit. Interruption of this mechanism in the clonic phase of the paroxysm by immobilization of the parts showing myoclonic jerks brought about immediate arrest of the seizure in the first case and temporary disappearance of the spontaneous focal discharges during the seizure in the second case.RÉSUMÉLes auteurs présentent deux cas d'épilepsie réflexe avec des crises hémiconvulsives provoquées par des stimulations proprioceptives (les vibrations d'un diapason et les mouvements passifs ou actifs).On a observé une dissociation proprioceptive au cours des crises, provoquées seulement par certaines stimulations proprioceptives (vibrations ou mouvements).On suppose que les stimulations proprioceptives apparaissant au cours des crises interviennent par un mécanisme de feedback. Par ce mécanisme les impulsions afférentes proprioceptives interviennent au niveau cortical, facilitant la transformation clonique des crises convulsives. L'interruption de ces mécanismes dans sa phase clonique par l'immobilisation du segment animé de mouvements myocloniques a provoqué un arrêt immédiat de la crise dans notre premier cas et une disparition de courte durée des décharges focales spontanées dans notre deuxième cas.

Stimulus control in pigeons based on proprioceptive stimuli from floor inclination.

Two groups of pigeons trained to peck a dimly illuminated disc in an otherwise dark experimental chamber with the floor horizontal (0 degrees tilt) or inclined 30 degrees to the left, respectively, show decremental generalization gradients of response rate when the floor inclination is varied from its training position. Discrimination training in which food reinforcement is available under one floor tilt condition but not under another steepens the slope of such gradients. In a secondv experiment, pigeons reinforced for pecking when the floor was tilted 10 degrees or 20 degrees and not reinforced under the alternative condition showed steep gradients with maximal responding displaced from the reinforced stimulus.

The control of the rocking response in hemileucine moths by sensory stimulation

The control by precurrent sensory stimulation of the side to which Automeris first swings its head at the beginning of a rocking response (the bias of the response) was examined. The responses of some moths are always biased to the same side whatever stimuli are presented. The direction of the bias of other moths can be controlled by bilaterally asymmetric stimuli which themselves do not release a response. When rocking is elicited after unequal, sustained illumination of the eyes, the response is biased to the more brightly lit side. The response is also biased to the same side as a unilateral ‘on’ stimulus and less consistently to the opposite side from a unilateral ‘off’ stimulus. The following results imply that the action of light and of ‘on’ stimuli on rocking are excitatory, whereas the action of ‘off’ stimuli is inhibitory: (1) Intense ‘on’ stimuli evoke the rocking response more frequently than intense ‘off’ stimuli; (2) the number of oscillations in a response (rocking score) is greater if moths are kept under bright illumination than if they are kept under dimmer illumination; and (3) an ‘off’ stimulus delivered during the course of a response will cut it short. The opposite actions of ‘on’ and ‘off’ stimuli can also be seen in the bias of the response after flashes of different lengths. After a long flash (500 msec) the response is biased to the same side as the flash, but after a short flash (5 msec) the response is more commonly biased to the opposite side from the flash. The flash length at which the direction of the bias switches is related to the excitability of the system emdiating rocking. Thus the responses of moths with high rocking scores are biased ipsilaterally by flashes which impose a contralateral bias on the response of moths with lower rocking scores. Stimulation with identical, overlapping flashes to both eyes showed that an ‘on’ stimulus to one eye inhibits the effects of a slightly later ‘on’ stimulus to the other eye. Proprioceptive stimuli also control the direction of the bias. The after-effects of visual and proprioceptive stimuli probably decay at different rates and may be stored simultaneously. The results are discussed with reference to the electrical activity of visually sensitive units recorded in the medial protocerebrum of saturniid and sphingid moths.

"Descending" neuronal units in the commissure of the crayfish central nervous system; and their integration of visual, tactile and proprioceptive stimuli.

AbstractThe integrative properties of “descending” neuronal units in respect to visual, tactile and proprioceptive stimuli were studied at the commissure level of the crayfish central nervous system and 41 entities were established, bringing the total number of established descending entities at this level to 69. All but three of these are interneurons, over half of which have an entirely homolateral input. Altogether 227 interneurons have so far been established in the crayfish central nervous system, 73 of which extend through more than one of the studied levels. Compared to the thoracic‐abdominal level, interneurons transmitting both anteriorly and posteriorly are very scarce. The properties of high order interneurons are discussed. In addition to those which respond to visual stimuli, or are multimodal, a number react only to mechanorecptive stimulation, and some of this latter type have peripheral sensory fields exclusively posterior to the recording level. A few interneurons, both visual and non‐visual, exibit inhibitory phenomena of various kinds, again mirroring the findings in the mammalian central nervous system. Visual interneurons were shown to respond to specific types of optic stimulation such as movement of objects or changes in light intensity in correspondence with units found in the optic nerves of other decapod crustaceans.

Matching Speech Cineradiography with Pseudospeech

The product of “speech synthesis” is, at best, pseudospeech, and since the neurophysiological processes operative in perception in general are little understood, the perception of pseudospeech remains particularly enigmatic. In the perception of natural speech, the ultimate cues have been postulated (Liberman) to depend upon proprioceptive stimuli arising from articulatory gestures and upon perceived differences and similarities to correspond more closely to articulatory than to acoustic features. The visual inspection of speech articulation possible with high-speed, x-ray motion-picture photography suggests the attempted fitting of pseudospeech continua to “corresponding” speech-articulation sequences, not only in the specific interest of improving the acoustic quality of simulated speech, with especial reference to timing phenomena, but also in the consequent general increase of knowledge about speech analysis, and as a contrivance for acoustically matching sustained articulation instants. Acoustically simulated “steady-state isolated vowels” and corresponding slides of typical articulatory instants are presented as an introduction to a demonstration of high-speed cineradiography of vowels uttered in isolation augmented with matching pseudospeech continua.

OVERTRAINING, TRANSFER TO PROPRIOCEPTIVE CONTROL AND POSITION REVERSAL.

If rats are overtrained on a visual discrimination they generally learn the reversal of the discrimination faster than non-overtrained rats. In position discriminations, however, this effect does not generally hold—indeed several investigators have found overtraining to retard position reversal. One of the important differences between the two types of problem seems to be the presence of irrelevant cues in visual discriminations, and their absence in position discriminations. It is suggested that a second important feature of position discriminations is that overtraining usually causes control of the maze running habit to be transferred from external to proprioceptive stimuli, and that successful reversal cannot normally occur until external control is re-established. In two experiments a study by Krechevsky and Honzik (1932) is repeated with certain modifications, with results that support this hypothesis; and a third experiment provides direct evidence of transfer to proprioceptive control in a T-maze. It is shown that this analysis will explain the apparently conflicting results of all recent position reversal experiments.

ON THE CHANGES OF CONSCIOUSNESS PRODUCED BY SUBTENTORIAL LESIONS.

In order to study the changes of consciousness associated with lesions of the posterior fossa it is necessary to define consciousness so that we may be ready to recognise the different mechanisms which may affect it. Many authors have attempted definition. We believe that the following proposition may be satisfactory: consciousness is a state which allows us to react at every moment to exteroceptive and proprioceptive stimuli and to know their respective values; this implies both vigilance and the confrontation with more or less precise memories. As G. Jefferson wrote, there are “two extreme meanings, the psychological and the physiological”.

Abnormal states of consciousness and muscle tone in infants born to schizophrenic mothers.

The evaluation of the changing pattern of consciousness can be used as a measure of the growing integrative capacity of the central nervous system in infancy. In the first months of life, at least two skills develop which are necessary for the maintenance of the quiet, open-eyed alert state. There is an increased general level of arousal(17) sufficient to permit responses to minimal visual and auditory stimuli. There is also a gradual modulation of spontaneous excitability and an increase in the toleration of proprioceptive stimuli. This permits a continuing stable state of awareness and prolonged, focused attention. These abilities are essential prerequisites for the well-integrated development of specffic alerting responses(17), which involve differentiated attentiveness, perceptual discrimination, patterns of accommodation, and the more complex functions which modify the accessibility of the CNS to different stimuli. The organization of a stable, sustained state of alertness by 8 weeks of age, as measu...

Proprioception variables as determiners of anticipatory timing behavior.

Anticipatory timing, where the human operator initiates an accurate response before the actual occurrence of the environmental event, is one of the most striking and least studied aspects of skilled motor performance. An experiment was performed on temporal and control system variables that could influence the timing of responses in a tracking task. Verification was sought for a proprioceptive trace hypothesis that holds the time-varying proprioceptive after-effects of movements to be the internal trace that persists in time and cues the occurrence of a future response. Ninety-six subjects participated. A 2×2×2 randomized factorial design used two values each of movement amplitude, spring loading, and signal duration as a means of manipulating proprioceptive stimuli and their time trace. Results supported the hypothesis. Signal duration and spring loading of the control induced significant effects for the number of beneficial anticipations, but movement amplitude had no significant effect. It was concluded that proprioception has a role in response timing, in addition to its traditional one of informative feedback.

Spasticity and spasms in hemiplegia and paraplegia.

SUMMARYThere are differences between the spasticities appearing in hemiplegia due to supraspinal lesions and in paraplegia due to spinal lesions, although the basic quality is progressive increased tension in muscles in response to stretch. Spasticity in hemiplegia is characterised by extensor predominance in the lower extremity and flexor predominance in the upper. In spinal paraplegia the spastic lower extremities are usually in flexion, although occasionally extension is present, more so with incomplete spinal lesions. Spasms, or rapid involuntary muscular contractions, have a similar distribution in the two states and may be spontaneous or induced by a variety of stimuli.The general physiological mechanisms involve exaggerated spinal stretch reflexes, due to release from and facilitation by supraspinal controls, especially reticular and cerebellar influences, increased susceptibility to proprioceptive stimuli, and possible overactivity in the gamma control system of the muscle spindles.Other special factors in spinal lesions include irritative phenomena at the site of the lesion and excessive activity at interneurones related to sprouting of boutons.

Topographic and toposcopic study of origin and spread of the regular synchronized arousal pattern in the rabbit

1. 1. Arousal-causing stimulation of an unanesthetized rabbit results in a regular 4–7/sec. activity in the hippocampus, the diencephalon and in parts of the cortex (synchronized arousal pattern). The activity was elicited by electrical, proprioceptive and pharmacological (physostigmine) stimuli. 2. 2. The amplitude distribution of this regular activity was determined by means of unipolar registration. Topographical distribution is independent of the type of stimulus used, but amplitude depends on type and intensity of stimulus and may vary with each animal. The highest amplitudes are to be found in the hippocampus in the region CA 3 and CA 4. The phenomenon was demonstrable not only in the hippocampus but also in the diencephalon as far frontal as the septum, caudally to the corpora quadrigemina and ventrally as deep as the base of brain. The most irregular activity occurs on the cortex, where the local activity is not completely suppressed, and the most regular in the diencephalon. The hippocampal activity is always masked by a more rapid (40–60/sec.) phenomenon. 3. 3. Phase relations of the synchronized arousal activity were examined in unipolar leads with the multivibrator toposcope. In almost all regions examined, the arousal pattern has the character of travelling waves and the point of maximum amplitude rarely coincides with the point of origin of the wave. Between cortex on the one hand and hippocampus and diencephalon on the other, there is almost always a phase shift of nearly 180°; there is little or no phase shift between hippocampus and diencephalon. There is rarely propagation at the cortex since the activity here is not sufficiently distinct. Waves arrive in the hippocampus from a region in the septum by way of the fimbria and from there they are propagated caudally and laterally. They arrive in the diencephalon frontal to N. anterior thalami and are propagated caudally as spherical waves with an average velocity of 340 mm/sec. at 6/sec. Spherical propagation is demonstrated by recording from three-dimensionally placed electrode rows; in transverse leads, a symmetrical propagation component from medial to lateral can be seen. Arousal pattern waves travel through both, diencephalon and hippocampus, as through a homogenous medium. 4. 4. Since destruction of the medial region of the septum results in irreversible inhibition of the synchronized arousal pattern in all parts of the brain, it may be assumed that the pace-maker for this activity, from which waves travel to the hippocampus and diencephalon, is to be sought in this region. 5. 5. Statistical treatment of data concerning the relation between frequency and propagation velocity of the arousal waves gives a linear relationship with a high significance. From this it can be concluded that the electrical field which corresponds to the single wave is of constant size and independent of frequency.

Activity patterns of interneurons in the caudal ganglion of the crayfish.

Responses of ascending interneurons from the caudal ganglion of crayfish have been recorded from single units isolated by dissection from the ventral nerve cord; in addition, post-synaptic activity within the ganglionic neuropile has been studied with intracellular micropipettes. The following classes of interneurons have been found: (1) Large fibers which responded to tactile stimuli with single spikes or phasic bursts. These units usually showed broad receptive fields; and spontaneous activity, when present, showed transitory depressions following responses to natural stimuli. (2) A group of fibers, including many small ones, which responded to proprioceptive stimuli with tonic discharges of varying adaptation rate. (3) Interneurons which showed responses both to tactile stimuli and to activation of the sixth ganglion photoreceptor; and (4) units with constant frequency discharges which were unmodifiable by any of the above afferent inputs. Intracellular recording of post-synaptic activity has shown (1) that widely graded excitatory post-synaptic potentials occur; (2) that multiple firing from single synaptic potentials is usual; (3) that the post-synaptic responses to phasic natural stimuli and to electrical stimulation of ganglionic roots are similar. The existence of widely graded post-synaptic potentials and of extensive receptive fields suggests a high degree of convergence from primary afferents to interneurons. The activation of such post-synaptic units involves integrative synaptic transfer, without 1:1 correspondence between pre- and post-fiber activity.

The encephalogram and electromyogram of motor conditioned reflexes after paralysis with curare

The author, like Liwanow, distinguishes three stages of bioelectric changes in the brain of a rabbit during the formation of a defensive motor conditioned reflex. He also separates a fourth stage, an already formed conditioned reflex, in which the rhythmic activity in the kinaesthetic analyzer disappears. A number of rabbits were subjected to the following procedures: 1. (a) Paralysis of the extremity with curare. 2. (b) Substitution of active with passive movements during the operation of the conditioned stimulus. 3. (c) The formation of conditioned motor reflexes after administration of pontocaine into the joint. In the light of these studies, the author discusses the factors underlying the appearance and disappearance of the driven rhythmic activity in the kinaesthetic analyzer (stages III and IV) and emphasizes the importance of proprioceptive stimuli for the formation of motor conditioned reflexes.

THE INFLUENCE OF PROPRIOCEPTIVE STIMULI UPON PERROTATORY AND POSTROTATORY NYSTAGMUS

Without covering their eyes, five leghorns were rotated at two different postures and both perrotatory and postrotatory head nystagmus were observed.Constant optic stimuli were given to the animals during the rotation by rotating the revolving chair in the center of a large cyclinder.The animals at the posture on a perch grasping it with their claws showed more jerks of perrotatoric head nystagmus but less jerks of postrotatory head nystagmus compared with them at the posture crouching on the flat plate of the revolving chair.Namely, the proprioceptive stimuli from the an;mal's legs to grasp a perch with their claws promote perrotatoric head nystagmus but decrease postrotatory head nystagmus.

POSTURE AND OPTIC REFLEX

In order to study the influence of animal's posture upon the optic reflex, five leghorns were kept in two different posture and certain amount of optic stimulation was given.1)Leghorns on a perch grasping it with their claws showed active optic head nystagmus and skillfuly maintained the posture adapting to the rapid optic stimulation.2)Leghorns crouching on a flat desk without grasping a perch with their claws, however, showed less jerks of optic head nystagmus and optic ataxia due to difficulty to maintain the posture.Namely, the proprioceptive stimuli from the animal's legs to grasp a perch influenced remarkably on optic reflex, promoting the jerks of optic head nystagmus and mainterance of the original posture without optic ataxia.

Tonus sympathique et activité électrique corticale

Simultaneous recording of the electrical activity of the cortex and of the arterial blood pressure in animals (cats and dogs) under Flaxédil demonstrates the following: 1. 1. In an animal which has no external sensory stimulation, there is a spontaneous fluctuation in the electrical activity of the cortex and also in the level of sympathetic tone. These variations both in the electrical activity of the cortex and in sympathetic tone are always synchronous and parallel; activation of the cortex corresponding with an increase (even a small one) in the blood pressure. 2. 2. Nociceptive stimuli (e.g. electrical stimulation of the sciatic nerve) produce a marked cortical activation and an increase in sympathetic tone (vasomotor effects and adrenaline secretion, etc.). Analysis of the effects of such stimuli under different experimental conditions, shows that: 2.1. ( a) the duration of the cortical activation after the nociceptive stimulus is directly related to the intensity of the sympathetic response; 2.2. ( b) while pre-bulbar section completely eliminates the possibility of putting into action the reticular activating system of Moruzzi and Magoun by means of nociceptive stimulation, peripheral sympathetic discharge is still preserved. However, there is still an intense cortical activation corresponding with increase in sympathetic tone, but this activation appears later, i.e. during the ⪡adrenaline phase⪢ of the hypertension produced by sciatic stimulation; 2.3. ( c) stimulation of the peripheral end of the splanchnic nerve or injection of adrenaline, either in the normal animal or in the animal after pre-bulbar section, produces an intense activation of all cortical areas, an activation which develops in parallel with the increase in peripheral sympathetic tone; 2.4. ( d) intercollicular section of the brain stem, passing to the ventral surface just rostral to the pons (section A, fig. 18) completely suppresses the cortical activation in response to a peripheral sympathetic discharge. After a section slightly more caudal (section B, fig. 18) this cortical activation persists. Cortical activation corresponding with a peripheral sympathetic discharge is therefore not due to a direct action of adrenaline or to the increase of blood pressure (both of which factors are of course interrelated) on the cortex, but to an action on pontomesencephalic formations; 2.5. ( e) cortical activation in response to an nociceptive stimulus therefore occurs by means of two mechanisms which, in general, overlap each other: (i) an immediate nervous activation which operates by means of a mechanisms which is now well known, i.e., through the ascending reticular activating system, and, (ii) by means of a subsequent “humoral” activation which also works not directly on the cortex but through pontomesencephalic formations; 2.6. ( f) the “humoral” activation allows an adjustment of cortical activity to the peripheral sympathetic activity existing at the moment. The fact that the increase in sympathetic tone (adrenaline, slight hypertension) is able to produce an electrical picture of cortical activation which is indistinguishable from that produced by an exteroceptive stimulus, suggests that the level of peripheral sympathetic tone is just as important a factor in maintaining the waking state as the continuous inflow to the brain of proprioceptive and exteroceptive stimuli. 2.7. 3. All these effects on cortical activity of a peripheral sympathetic discharge are suppressed by very small doses of anaesthetics. 2.8. 4. Distention of the carotid sinus (within physiological limits) produces a progressive reduction in cortical activity and the appearance of slow waves. This effect is still seen after high spinal section combined with bilateral vagotomy, a procedure which suppresses the hypotensive response to carotid sinus distention, and which suppresses in the same time direct effects from the carotid sinus on the vasomotor control of the cerebral circulation. The reduction in cortical activity in response to carotid sinus distension is therefore independent of variations in the blood pressure and is mediated by purely nervous mechanisms. This appears to be the first example of an afferent inflow which “damps” rather than activates the cortex. 2.9. 5. The experimental facts described in this paper have been integrated in a provisional schema of the regulatory mechanisms responsible for the continuous adjustment and interrelations of cortical activity and peripheral sympathetic tone.

On the physiological action of carbon dioxide on cortex and hypothalamus

Inhalation of 10 per cent CO 2 reduces the responsiveness of specific sensory projection areas to optic and acoustic stimuli while it increases the reactivity of the hypothalamic cortical system. The activation of the latter is evident from the increased asynchrony of potentials in all parts of the cerebral cortex which is associated with similar changes in hypothalamic potentials. In sensitive preparations and/or under the influence of slightly higher concentrations of carbon dioxide neuronal recruitment may occur resulting in a marked increase in the amplitude of the potentials. This effect of carbon dioxide on the hypothalamic-cortical system is similar to that produced by proprioceptive or nociceptive stimuli which evoke arousal reactions in lightly anesthetized animals. It is shown that the action of proprioceptive and nociceptive stimuli is greatly magnified in hypercapnia. The excitability of the cortex is thought to depend, other conditions being equal, on the hypothalamic-cortical system which influences the cerebral cortex as a whole and afferent impulses whose action is confined to a specific cortical projection area (optic stimulus → visual cortex). A functional separation of these two systems can be achieved by the action of carbon dioxide. The effect of high concentrations of carbon dioxide (30 to 40 per cent) administered in oxygen or air is fundamentally different from that of “low” carbon dioxide. The chief actions of “high” carbon dioxide are: It reduces or eliminates the small, frequent background potentials while the grouped, Dial potentials are relatively unchanged. If high carbon dioxide is administered for longer periods cortical activity may temporarily disappear. Thereafer, Dial potentials reappear and may occur more frequently than prior to the administration of carbon dioxide. Topically induced cortical strychnine spikes undergo a slight reduction in amplitude and a marked diminution in frequency under the influence of high carbon dioxide concentrations. Potentials recorded from the posterior hypothalamic area show similar changes. The reduction in amplitude and frequency of the potentials suggests neuronal decruitment in cortex and hypothalamus under the influence of anesthetic carbon dioxide concentrations. The potential changes described in the preceding paragraphs occur in carbon dioxide-air as well as in carbon dioxide-oxygen mixtures. They are reversible on readmission of air. Occasionally, rebound phenomena are observed under these conditions. Optic and acoustic stimuli still elicit typical responses in their specific cortical projection areas even when the resting potentials of these or other parts of the cortex have vanished. The reduction in amplitude of the acoustic potentials is less than that of the visual cortical responses. While specific cortical projection areas remain excitable in high carbon dioxide, the generalized response of the whole cerebral cortex to proprio- and nociceptive stimuli is abolished. Since hypothalamic excitation is likewise missing this result is interpreted as indicating that “high” carbon dioxide eliminates the reactivity of the hypothalamic-cortical system while the responsiveness of specific cortical projection areas is retained. It is suggested: ( a) that the selective functional elimination of the hypothalamic-cortical system, which is activated in arousal, is characteristic for the state of loss of awareness and narcosis; ( b) that the background potentials of the cortex depend primarily on hypothalamic-cortical discharges; ( c) that functional elimination of the activating hypothalamic-cortical system releases the inhibitory system regulated by intralaminar thalamic nuclei and leads to more frequent Dial potentials in the cortex.