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Biomedical subjects

B Zernicki

Publications and source records attributed to B Zernicki.

At least 55 records · Page 3Linked to original sources
PubMed1982

Rapid learning of visual and auditory spatial task in binocularly deprived cats.

Visually deprived and non-deprived cats were trained in a task involving a directional alimentary response spatially contiguous with a visual or an auditory cue. Both visual and auditory tasks were learned much faster by deprived cats. In these cats targeting reflexes evoked by the cues were stronger. When the modality of the cue was changed (from visual into auditory or vice versa), the learning was rapid in both non-deprived and deprived cats.

Animals↗
PubMed1981

Hippocampal theta activity in the acute cerveau isolé cat.

In three cerveau isole cats, cortical and hippocampal EEG activity were recorded. In the cortical records, spindles alternated with low-voltage activity, whereas theta activity dominated in the hippocampus. The amount and frequency of theta were similar to those described previously for the pretrigeminal cat. In confirmation of previous results on rats, although cortical EEG activity differs in cerveau isole cat and pretrigeminal cat, both preparations show domination of theta activity in the hippocampus. It is concluded that the mesencephalic transection eliminates inhibitory effects from the lower brainstem on generators of the theta rhythm.

Animals↗
PubMed1981

Chronic pretrigeminal kitten.

In two kittens the brainstem was transected at the pretrigeminal level at the age of 11 days. The kittens were then observed for 79 and 51 days. As compared with control littermates, the weight of the transected brains was reduced by about 25 percent. As compared with the controls transected at the age of 2 or 3 months, as well as with previously described cats transected at adult age, the function of the caudal part of the kittens was much better. They showed some locomotion, drank and ate when the mouth was placed in contact with the milk or meat, rejected untasty food and showed satiation. On the other hand, the function of the isolated cerebrum was reduced as shown by only abortive ocular and EEG responses to visual stimuli. Thus, the pretrigeminal transection performed at an early period of life improves the development of the caudal part of preparation, but impairs that of the isolated cerebrum.

Aging↗
PubMed1981

Diminution of cortical visually evoked potentials during the following eye-movement in the cat.

Six cats with brainstem transection at the pretrigeminal level were used. Visually evoked potentials (VEPs) to a diffused flash were recorded in the marginal, suprasylvian, ectosylvian and sigmoid gyri under three situations: the eyes were motionless in the position of rest, the eyes followed a moving object, and the eyes moved spontaneously. In the marginal and ectosylvian gyri the VEPs were smaller in the second situation, compared to the first and third. It is concluded that the VEP reduction is not produced by the eye-movement itself, but by the process of selective attention to the followed stimulus.

Animals↗
PubMed1980

Loss of object discrimination after ablation of the superior colliculus-pretectum in binocularly deprived cats.

The effects of ablation of the superior colliculus-pretectum on a previously elaborated object discrimination task were compared in cats reared in normal conditions, in cats reared in the laboratory, and in cats deprived of patterned vision. The normally reared cats were least deficient postoperatively, whereas deprived cats were most deficient. Seven of 8 deprived cats failed to re-reach criterion. Previous results showed that after removal of the visual cortex deprived cats were less deficient than normally reared controls. It is concluded that in discrimination learning the function of the abnormal visual cortex of deprived cats is partially taken over by the superior colliculus-pretectum.

Animals↗
PubMed1980

The acute pretrigeminal rat.

In five rats the brainstem was transected at the pretrigeminal level. In the frontal cortex, desynchronized EEG activity dominated, while in the dorsal hippocampus theta activity of low frequency (about 4 cycle/s) was almost continuously present. Olfactory and visual stimuli and electrical stimulation of the posterior hypothalamus induced or increased cortical EEG desynchronization and increased the regularity and the frequency of the theta activity in the hippocampus. However, visual stimuli were effective only in three rats. Ocular responses (pupillary dilatation, eye movements) were never observed to any stimulation. It is suggested that similarly as in the pretrigeminal cat, the isolated cerebrum is awake in the pretrigeminal rat.

Animals↗
PubMed1980

The pretrigeminal cat as an instrument for investigation of the ocular fixation reflex.

The fixation reflex is an important representative of orienting (targeting) reflexes. In the cat with the brainstem transected at the pretrigeminal level the fixation reflex is easy to investigate for the following reasons: (a) all sensory inputs to the isolated cerebrum of the pretrigeminal cat are eliminated, except for visual afferents, (b) the isolated cerebrum is continuously awake, (c) the vertical fixation reflex only is present. The behavioral and neural characteristics of the fixation reflex in the pretrigeminal cat are reviewed.

Animals↗
PubMed1979

Single-unit activity in cat's isolated midbrain.

The midbrain was isolated by two brainstem transections, pretrigeminal and premesencephalic. In the isolated midbrain, particularly within the reticular formation, EEG activity was greatly depressed. On the other hand, single-unit spike activity remained at a high level. The spatial density of active reticular units and the rate of their spontaneous activity were at least not smaller than those in the midbrain of the cat with only a pretrigeminal transection. Thus the flat EEG record is not necessarily a sign of the absence of neural activity.

Animals↗
PubMed1979

Regional cerebral blood flow and visual attention in the awake isolated cerebrium of the pretrigeminal cat.

The effect of visual stimulation on cerebral blood flow (CBF) was studied in five cats with brainstem transection at the pretrigeminal level. The CBF was measured in the occipital and frontal cortex by external monitoring of the clearance of 133Xe. As a visual stimulus, a feather duster moving for 2 min in front of the cat’s eyes was used. This stimulus evoked an increase of CBF. In the occipital cortex the CBF increase was greater and comparable to that evoked by elevation of the arterial pCO2. Both in the occipital and frontal cortex the CBF response was positively correlated with the intensity of the ocular-following reflex and the cortical EEG arousal. It is concluded that the CBF increase was correlated with the degree of attention paid by the cat to the visual stimulus.

Animals↗
PubMed1978

The ocular following reflex in cats deprived of pattern vision from birth.

An investigation of vertical ocular following reflexes evoked from retinal sites of different horizontal eccentricity was carried out on visually deprived cats. The recording was performed in pretrigeminal preparations where horizontal eye movements are absent. A light slit or a black stick (1 degrees X 4 degrees) were moved with 10 degrees/sec speed for 2 sec along the vertical meridian or parallelly up to 40 degrees in the nasal or temporal hemifield. As in previously described normally reared cats, the following reflexes were evoked from the whole area, but the pursuit movements had longer latency and lower velocity at the periphery than in the center of the retina. However, irrespectively of the place of stimulation, the latency of the pursuit movements was longer, their velocity lower and the course less regular than in normally reared cats. It therefore follows that in visually deprived cats the ocular following reflex is impaired.

Age Factors↗
PubMed1978

The effect of first visual stimulation on incorporation of labelled leucine into cerebral cortex of binocularly deprived kittens.

One-month old kittens, binocularly deprived with hoods from birth, were used. Before the experiments in which visual stimulation was applied the brainstem of kittens was transected at the pretrigeminal level. Cortical EEG activity and ocular behavior indicated that the isolated cerebrum of preparations was usually awake during experiment. Patterned visual stimulation was directed to one hemisphere, while the other was used as a control. Visual stimulation evoked in some cases (in 8 out of 17) an increase of incorporation of labeled leucine into the proteins of the striate cortex. Electrophoresis on polyacrylamide gel did not reveal any differences in the pattern of insoluble proteins between the stimulated and control visual cortex. It is suggested that first visual stimulation may enhance the protein metabolism of striate cortex in young kittens. Some unknown up to now physiological factors (motivation, attention?) may be critical for these phenomena.

Animals↗
PubMed1978

Single unit responses to moving spots in the superior colliculus of the cat's isolated midbrain.

The midbrain was isolated from the pons and forebrain by two brainstem transections, pretrigeminal and "preoptic", inclined at 32 degree or 35 degree to the vertical plane. The preoptic transection passed along the rostral border of the optic tract, leaving it and the chiasm intact. Thus, direct visual input into the isolated tissue was maintained. Single unit responses to a moving spot were investigated in the superior colliculus. This stimulus evoked vigorous responses in most cells. Of the 70 tested units, 25 showed direction-selectivity, 48 speed-selectivity and 47 reacted to diffuse flash. Compared to cats with only pretrigeminal transection only the number of direction-selective units was reduced. The reduction was similar to that found previously in cats with ablated visual cortex or visually deprived from birth. Thus, the cells of the isolated superior colliculus show a striking degree of functional integrity.

Action Potentials↗
PubMed1977

A blood flow increase to a visual stimulus in the occipital lobe of the cat with brainstem transection at the pretrigeminal level.

The effects of visual stimulation on the cerebral blood flow were studied in pretrigeminal cats. The visual stimulus was a feather duster which was moved for 4-5 min in front of the cats eyes. The cerebral blood flow was measured each 15 min with [133]Xe clearance method in the left occipital lobe. The visual stimulation evoked an increase of the cerebral blood flow which was accompanied by an ocular following movements and a cortical EEG desynchronization. The arterial blood pressure was unchanged. All these responses habituated rapidly when the stimulus was repeated at 15 min intervals. A similar increase of the cerebral blood flow was obtained by 9 percent CO2 inhalation. The administration of amphetamine increased the cerebral blood flow, whereas Nembutal decreased it. The visual stimulus evokes an increase of the cerebral blood flow in a condition when the lower brainstem is separated from the cerebrum.

Amphetamine↗
PubMed1976

Hippocampal theta activity in the acute pretrigeminal cat.

In five cats with a pretrigeminal brainstem transection ocular behavior and cortical and hippocampal EEG activity were recorded. The ECoG desynchronization was usually accompanied by clear hippocampal theta activity. The episodes of ECoG desynchronization and hippocampal theta activity lasted in some cases for several hours. Visual stimuli evoked two types of hippocampal EEG response: (I) increase of regularity and frequency of theta activity (II) EEG desynchronization. The intensity of these responses was positively correlated with the intensity of ocular and ECoG components of the orienting reflex (the most conspicuous phenomenon being their habituation with stimulus repetition). Electrical stimulation of the midbrain reticular formation evoked theta activity of a frequency proportional to stimulus voltage; for maintaining it constant stimulus strength had to be elevated gradually. Depriving the brain of influences from the lower brainstem does not influence qualitatively the function of reticulo-septo-hippocampal system.

Animals↗