Biomedical subjects
Publications and source records attributed to B Zernicki.
A two-choice apparatus for food reward was used. Normal and visually deprived cats were trained to discriminate white and black cards. After the animals had reached criterion, the contrast difference between the cards was diminished in steps. When the brightness ratio had been reduced to 1.8, discrimination was impaired in the deprived cats and not in the normally raised cats.
The brain was transected in eight rats: the transection passed through the posterior pole of the superior colliculi and ended down at midhypothalamic level. The EEG activity in the dorsal hippocampus and cortex showed continuously slow, high amplitude waves. Thus the posterior hypothalamus is critical for the previously described hippocampal theta rhythm found in rats transected at the posthypothalamic level.
Six normally reared cats were trained on a three-choice delayed response task to visual stimuli. All cats mastered 1 min delay, three cats 2 min delay and one cat 6 min delay. Learning was much better than in previously studied cats reared in laboratory cages. It was comparable to that known for auditory stimuli in normally reared cats.
Pattern discrimination learning was compared in cats reared in a normal environment during the first months of life (N cats), control cats reared in the laboratory with opened eyes (C cats), and cats deprived binocularly of patterned vision from birth (BD cats). A two-choice apparatus was used for training. In Expt. I the cats had been trained without a partition between stimuli and retrained with the partition. In Expt. II the partition was used from the beginning of training. The partition slowed down the learning in all groups. However, the BD cats were much more affected than N cats, and C cats seemed to be more affected than N cats and less than BD cats. In BD and C cats the number of errors of entering an incorrect alley without pushing the gate was increased. In contrast, when the partition was absent and discrimination very simple (stimulus vs no stimulus), the BD cats seemed to master the task even more quickly than N and C cats. The results suggest that the deficit produced by the partition consisted largely in a difficulty in rapid choosing a correct directional response at distance. In BD cats the mechanism of the deficit was complex.
In two adult cats and in three kittens aged from 8 to 11 days the brain stem was transected at the pretrigeminal level. The preparations were maintained from 7 to 79 days and processed histologically together with nonoperated controls. In kitten preparations brain was underdeveloped as shown by less numerous secondary sulci on the surface of the cortex. However, both cat and kitten preparations showed similar retrograde and anterograde neuronal degeneration. They also showed a similar transneuronal degeneration apparent in an increased density of neurons and their shrinkage in several structures investigated in the isolated cerebrum and the lower brain stem. Thus in kitten preparations a direct effect of transection predominated that of brain development. In the adult preparations at the level of transection a great accumulation of macrophages was found and the scar was built with connective tissue. In contrast, in kittens the transection scar was well delineated and built by astrocyte processes.
In eleven acute precollicular rats, cortical and hippocampal EEG activity was recorded. Hippocampal theta activity of low frequency (mean 4.5 c/sec) was found in nine rats and in four occupied above 50% of the recording time. In contrast, in the cortex the synchronized EEG activity dominated. The electrical stimulation of the posterior hypothalamus induced the theta rhythm, or increased its frequency. The large amounts of theta activity in some rats suggests that the forebrain theta pacemakers, partly modulated by the posterior hypothalamus, are released from brain stem inhibitory influences.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Pattern discrimination learning was compared in three groups of cats: reared in normal conditions, reared in the laboratory with opened eyes, and deprived of patterned vision from birth. A four-choice apparatus without partitions was used. The figure of a disc was reinforced with food, whereas a cross, triangle and square were not. All groups reached criterion after similar numbers of trials and errors, indicating that in binocularly deprived cats, simple perceptual and associative learning are not impaired.
The brain stem was transected in cats at the pretrigeminal level. Additional lesions were placed in 17 cats, whereas 10 served as controls without further manipulation. All received a small dose of amphetamine. The vertical following reflex was evoked by a slit of light or a black bar (1degrees X 4degrees). The stimuli moved along the vertical 'meridian or parall to it up to 40 degrees in the left or right hemifield. A unilateral removal of the superior colliculus produced a loss of reflexes evoked from the contralateral hemifield. In contrast, after unilateral ablation of the visual cortex only in one of 4 cats was the reflex from the contralateral hemifield smaller than ipsilaterally; and after unilateral ablation of the frontal oculomotor cortex, no hemifield asymmetry of these reflexes was found in any cat. The reflexes also survived bilateral ablation of the visual cortex or the frontal oculomotor cortex. After transection of the corpus callosum the reflexes were virtually normal. The data confirm that in the cat the orienting fixation reflex is mediated by the superior colliculus. On the other hand, this reflex appears to be largely independent of the cerebral cortex.
The concept of the orienting reflex is discussed from the historical perspective. The following conclusions are proposed: (1) in accordance with the spirit of Pavlov's concept the orienting reflex is a response to a stimulus unexpected in a given situation; (2) the reflex consists of targeting, arousal and perceptual components; (3) the reflex has three stages, which in the targeting component are represented by the movement towards the stimulus, the maintenance of fixation of the stimulus and the return movement; (4) when the reflex is evoked by a new stimulus, perceptual learning occurs in its second stage. The non-orienting targeting reflexes are reviewed. The pretrigeminal cat is discussed as a model for investigation of the ocular orienting reflex.
The pretrigeminal preparation (pretrigeminal animal) is obtained by transection the pons in front of roots of the trigeminal nerves. The rostral part of the preparation (isolated cerebrum) has olfactory, visual and humoral inputs and controls vertical position of eye and their pupillary diameter and accommodation. The pretrigeminal preparation was described in the cat and rat. During the acute stage the isolated cerebrum is continuously awake, alternatively alert and drowsy. In the chronic stage a sleep-waking cycle recovers, but paradoxical sleep remains absent and synchronized sleep is reduced. Thus the cerebrum can largely compensate for the withdrawal of influences from the deactivating structures of the lower brain stem. Olfactory and visual stimuli produce a virtually normal arousal response. Its major components are: dilatation of pupils, desynchronization of cortical EEG activity, appearance of theta activity in the hippocampal EEG, and an increase of the cerebral blood flow. If the stimulus is repeated, the arousal response habituates with a normal rate. In the pretrigeminal cat there are two ocular targeting reflexes: vertical fixation and accommodation. The fixation reflex has a normal general course and shows normal habituation, but it is less precise than in the intact cat. The accommodation reflex is normal. Classical and instrumental ocular conditioned reflexes can be elaborated in the pretrigeminal cat. The conditioned pupillary dilatation appears at a normal rate. On the other hand, the elaboration of the conditioned vertical eye movement is slower than in the intact cat, possibly as a result of the lack of the proprioceptive feedback from the extraocular muscles. In conclusion, excitability, integrity and plasticity of the isolated cerebrum of the pretrigeminal preparation seem to be virtually normal. In contrast to the pretrigeminal preparation, the "cerveau isolé" is comatose during the acute stage. In the chronic stage, however, the sleep-waking cycle recovers and with time it becomes similar to that in the pretrigeminal preparation. However, the vertical fixation reflex remains impaired in the low "cerveau isolé" and is obviously absent in the high "cerveau isolé". The caudal part of the preparation has a normal contact with the outside world, but it cannot largely make use of it. However, it satisfactorily controls the circulation and respiration. Rats are superior than cats: pretrigeminal cat cannot turn over from one side to the other and is fed by stomach tube, whereas pretrigeminal rat can crawl and eat food introduced into the mouth.(ABSTRACT TRUNCATED AT 400 WORDS)
Cortical and hippocampal EEG activity was analysed in cerveau isolé and and pretrigeminal rats. In the acute stage, waking EEG patterns were absent in the cerveau isolé, whereas sleep EGG patterns were absent in the preparations. However, already on the second day the EEG waking sleep cycle recovered in the majority of rats. Paradoxically, stimuli directed to the caudal part of the preparations evoked stronger cortical and hippocampal EEG arousal than olfactory and visual stimuli. The rats exhibited some locomotor and grooming behaviour and could be fed orally. It is concluded that the activity of the isolated cerebrum of the rat is similar to that of cat preparations, but that functions of the caudal neuraxis are superior in rats.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Cortical and hippocampal EEG activity was analysed in 14 cerveau isole and 8 pretrigerninal rats. In the acute stage, waking EEG patterns were absent in the cerveau isole, whereas sleep EEG patterns were absent in the pretrigeminal preparations. However, already on the second day the EEG waking-sleep cycle recovered in the majority of rats. Paradoxically, stimuli directed to the caudal part of preparations evoked stronger cortical and hippocampal EEG arousal than olfactory and visual stimuli. The behavior of the caudal part was observed in 25 preparations. Although in abortive form, the rats did show some locomotor and grooming behavior, and could be fed orally. The peripheral events of paradoxical sleep appeared only on the fourth or fifth day of survival of the cerveau isole rats. It is concluded that the activity of the isolated cerebrum of the rat is similar to that of cat preparations, but that functions of the caudal neuraxis are superior in rats.
Intermediate stage of sleep, previously described in the rat, was studied in the cat. The intermediate stage was a short-lasting episode, represented in the EEG activity by cortical spindles, which was accompanied by theta activity in the hippocampus. The cortical EEG spindles appeared simultaneously with hippocampal theta or on its background. Sometimes, geniculo-occipital waves were recorded during this stage. Such an episode of a few such episodes in sequence occurred frequently just before the paradoxical sleep and occasionally just after it. The amplitude of the positive fourth component of the somesthetic evoked potential induced in the S1 cortex by stimulation of the ventrobasal complex, was lower during the intermediate stage than during the other stages of the sleep-waking cycle. The EEG pattern of the intermediate stage was periodically observed under Nembutal anesthesia at the expense of paradoxical sleep and in acute cerveau isolé preparation. The results suggest that activatory ascending influences from the brainstem, which modulate waking processes, gradually decrease during slow sleep and are the lowest during the intermediate stage, when the influences for paradoxical sleep are still negligible.