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Biomedical subjects

A Michalski

Publications and source records attributed to A Michalski.

At least 55 records · Page 3Linked to original sources
PubMed1983

Interactions between cat striate cortex neurons.

A series of simultaneous recordings from several striate cortex neurons were made in paralyzed, anesthetized cats. Recordings were obtained with one or two bundles of extra fine wires and originated from one and two cortical orientation columns. Standard PST histograms and, in some cases, response planes were used to analyse the neuronal receptive fields. Functional connectivity between neurons was assessed by cross-correlation of their spike trains. It was found that 61% of neuronal pairs found within a column shared the same input, either excitatory or inhibitory, Even if neurons in a pair belonged to two different columns separated by 1mm lateral distance, 40% of pairs still exhibited shared input coordination. This type of coordination could also encompass all combinations of simple and complex fields in the pair. Direct connections between neurons were found almost exclusively within columns: excitatory connections were found in 20% of cases and inhibitory in 8%. Direct connections were often accompanied by the other types of interactions. Only one example of excitatory and one of inhibitory direct connections were found between columns. In both cases preferred orientations were almost identical.

Animals↗
PubMed1983

Responses of area 17 neurons in cats binocularly deprived by rearing in hoods.

Responses of single units of area 17 were recorded in cats binocularly deprived by rearing in hoods. Neurons were recorded in pairs or in three-neuron groups with multichannel microelectrodes. Of 131 units recorded 22 percent were not visually excitable. The rest were predominantly monocularly driven. Response strength defined as the PST peak-to-background ratio was lower than 10 in 90 percent of cells. The orientation selectivity defined as the ratio of response strengths for the preferred and null stimulus orientations was lower than 5 in 79 percent of neurons. Directional selectivity was detected in 22 percent of units. The aim of this paper is to show that, considering the electrophysiological effects in cortica1 area 17, rearing in hoods can be used instead of eyelid suturing. This paper describes the standard parameters of units that were subsequently used for the analysis of interneuronal connectivity in visually deprived cortex (10).

Adaptation, Physiological↗
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↗
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↗
PubMed1977

The effects of pursuit eye movements on single unit activity in cat visual cortex.

The pursuit eye movements were assumed to be an indicator of the time periods when visual information is actively processed. The experiment was performed on cats with pretrigeminal transection of the brain stem. In such preparations only vertical eye movements were preserved. Under these conditions the following eye movements could be evoked by vertical movements of the stimulus at the periphery of the retina. The influence of these movements on the activity of units which had their receptive fields in area centralis was tested. Contralateral eye was immobilized and the position and preferred direction of the units' receptive fields was tested. Significant differences in neuron activity correlated with the pursuit eye movement were found in 22 percent of cells. It is suggested that the effect is due rather to the active state of visual system than to the peripheral stimulation of retina or the information incoming from extraocular muscles.

Animals↗
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↗
PubMed1976

[Quantitative study of primitive pyramidal cells in rat anterior cingular cortex].

In the present paper the primitive pyramidal cells of the Vthlayer of the anterior cingulate cortex in adult male white rats were analyzed quantitatively and compared statisticaly with large pyramidal cells of the same region. The number of dendrites, the total lengths of dendrites, the number of spines and the density of spines -- according to the order of dendrites -- show similarity between the primitive pyramidal cells and the large pyramidal cells the latter one exhibit the higher values. The curves of distribution of the various density of spines along the apical main dendrite of both cell types are similar in shape, too. The lengths of the dendritic fields and their basal spines-values are without significant distinction for both cell types, however there are more dendritic fields in large pyramidal cells. Refered to a complete pyramidal neuron they can say: there are significantly higher values in large pyramidal cells for the number of dendrites and their total lengths, the total number of spines, the number of branching sites sites and free endings. However the density of spines of the complete neuron has no significant differences between primitive and large pyramidal cells.

Animals↗
PubMed1975

Single-unit responses to natural objects in area 19 of cats with different early visual experiences.

Cats deprived of pattern vision with hoods and normal cats were used. During the first 3 months of life some hood-reared cats had visual experience with a three-dimensional cross or a ping-pong ball. Recording were performed in adult cats with a pretrigeminal brainstem transection. Unit responses to the cross and the ball were recorded in area 19 within the projection of area centralis. Stimulus-dominance of the exposed object was manifested weakly. Both exposed and control objects activated more units in the experienced hood-reared cats than in hood-reared and normal controls. Compared with previous finding, the present results indicated that early visual experience affects area 19 differently than areas 17 and 18.

Age Factors↗
PubMed1975

Clare-Bishop area in the cat: location and retinotopical projection.

Visual responses of single units in the cortex of the middle suprasylvian sulcus were evaluated in the pretrigeminal cat. Electrode penetrations which passed through the Clare-Bishop area were in 94 percent of the cases within the stereotaxic coordinates A2 and A8. Within the Clare-Bishop area 40 percent of the units were responsive to the visual stimuli employed whereas adjacent to it only 10-20 percent responded. Correlation between receptive field size and eccentricity was poor or absent. Most receptive field centers lay within the lower contralateral quadrant. Because of the large size of the receptive fields, their scatter and individual variability, it was not possible to depict a precise scheme of retinotopical projection.

Animals↗