Peculiarities of cytochrome oxidase activity in the visual cortex neurons of kittens reared under the conditions of flickering illumination

The objective of this study was to analyze the influence of the light flickering with the frequency of 15 Hz, on the neuronal metabolic activity in kittens reared under the conditions of mesopic illumination. The method for demonstration of a respiratory enzyme cytochrome oxidase was used to study the visual cortex areas 17 and 18 and the lateral geniculate nucleus. It was shown that in kittens that were subjected to this stimulation as opposed to intact animals and to kittens reared under the conditions of mesopic illumination, specific changes in pattern of cytochrome oxidase distribution in area 17 took place. This change was manifested by the appearance of alternating zones of increased and decreased enzyme activity in layers III and IV. Within the cortical area 18 and lateral geniculate nucleus, no changes in the pattern of cytochrome oxidase activity distribution were detected in experimental kittens. It is suggested that flickering illumination results in disequilibrium of Y- and X-visual pathway activity.     

Patterns of cytochrome oxidase activity in areas 17, 18 and 19 of the visual cortex of cats and kittens

Summary The laminar pattern of cytochrome oxidase activity was studied in visual cortical areas 17,18 and 19 in adult cats and kittens, following electrophysiological determination of the boundaries of these areas in all but the youngest animals. The patterns of cytochrome oxidase staining and the cytoarchitectonic appearances of areas 17, 18 and 19 were compared. At all ages activity was especially high in the region of layers IV and VI in areas 17 and 18, and was low in all laminae in area 19. The results suggest that the degree of cytochrome oxidase activity in these regions of the visual cortex may be related to the strength and type of projection that they receive from the lateral geniculate nucleus. The cytochrome oxidase technique is a useful means of defining the 18/19 border, and may help locate the boundary between areas 17 and 18, in both adult cats and kittens.     

Some aspects of the modular organization of the primary visual cortex of the cat: Patterns of cytochrome oxidase activity

The distribution of the enzyme cytochrome oxidase (CO) in continuous series of parasagittal sections from field 17 and frontal sections of the dorsal nucleus of the lateral geniculate body (LGB) from normal kittens and adult cats was studied. In all cats apart from neonates, layer IV showed regularly alternating areas with above-background levels of CO activity (“spots”). There was a significant increase in the contrast of the “spots” from days 13 to 21, which was followed by a significant decrease from days 48 to 93. These changes coincided with ontogenetic changes in the level of visual system plasticity. There were no differences in CO activity between layers A and A1 of the dorsal nucleus of the LGB. It is suggested that the non-uniform distribution of the level of functional activity of neurons in field 17 reflects the formation of columnar cortical structures during the critical period of postnatal ontogenesis. __________ Translated from Morfologiya, Vol. 132, No. 5, pp. 28–33, September–October, 2007.     

Effects of Transient and Prolonged Flashing Light Stimulation on the Cytochrome Oxidase Module System in Layer IV of the Primary Visual Cortex of Kittens

Cytochrome oxidase spots in layer IV of field 17 of the primary visual cortex were studied in kittens aged 33, 49, and 93 days, stimulated with a light flashing at a frequency of 15 Hz. The kittens of one group received stimulation from the moment of eye opening until euthanasia (prolonged stimulation); other groups received stimulation for eight days starting from ages 26, 42, or 85 days (transient stimulation), again until euthanasia. Both types of stimulation were found not to alter the geometrical characteristics of cytochrome oxidase spots, but led to significant increases in the contrast of spots located in the splenial gyrus. Increases in spot contrast in the lateral gyrus occurred only after prolonged stimulation to age 93 days or after transient stimulation from age 26 days to age 33 days. Thus, stimulation of kittens of different ages with a light flashing at a frequency of 15 Hz led to structural-metabolic changes in the primary visual cortex. These changes were apparent to different extents in areas of the cortex responsible for central and peripheral vision. This may be explained, firstly, by the predominant activation of the Y conducting channel of the visual system and, secondly, by the increase in dominance of the contralateral input to the primary visual cortex. Translated from Rossiiskii Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 94, No. 5, pp. 557–565, May, 2008.     

Effects of monocular strobe rearing on kitten striate cortex

Summary Monocular deprivation in kittens does not lead to an ocular dominance shift in striate cortex if the visual stimuli do not contain contours. In the present study we sought to find out whether an ocular dominance shift is produced if the visual environment does contain contours but is devoid of motion. Six kittens were reared with one eye occluded in a visual environment that was lit only by the light of a stroboscope (2 flashes per sec). Exposure was started at 5–6 weeks of age after dark-rearing from birth and extended until 8–12 weeks of age for 8 h per day. The rest of the time was spent in total darkness. Thus, the animals were completely deprived of vision in one eye, while the other eye experienced only stationary flashing contours. Single units in area 17 of these animals were studied and compared to normally reared cats. In all six animals ocular dominance was clearly shifted towards the eye with strobe experience. The ocular dominance shift showed, however, the following interdependencies with other parameters: neurones that responded to stationary flashing test stimuli were nearly always dominated by the strobe eye; neurones that responded only to moving bars or edges remained binocular. In the normal control animals the ocular dominance distribution was similar for both groups of cells. Track analysis according to cortical lamination revealed that neurones in infragranular layers consistently showed a weaker OD shift towards the strobe eye than neurones in supragranular layers (including layer 4). Response latencies to stationary flashing stimuli were significantly shorter in the strobe-reared animals than in the normal controls. Orientation tuning was normal in all animals. Directional tuning was reduced after monocular strobe experience, but not by the same amount as described after binocular strobe rearing. The present results demonstrate that monocular visual experience reduced to stationary flashing contours is sufficient to produce on ocular dominance shift in striate cortex. This adds further support to existing notions about the role of nervous activity for changes in cortical connections. Cortical responses to afferent stimulation and the resulting correlated activation of pre- and postsynaptic neurones seem to be a prerequisite for a stabilization of synaptic connections.     

Effects of visual deprivation on the postnatal development of the geniculocortical projection in kittens

In kittens reared with either monocular, binocular or reverse suture, beginning before the physiological eyelid opening (around one week of age) and lasting until after one month, the cortical laminar distribution of geniculocortical afferents to area 17 was examined by using orthograde transport of wheat germ agglutinin conjugated with horseradish peroxidase, and compared with that in normal kittens. In normal kittens, at birth, the afferents were distributed most densely in layer I and, to a lesser extent, widely from the upper part of layer II to layers V or VI. After one month, the afferents were found mainly in and around layer IV and very sparsely in layer I. Neither binocular nor monocular suture affected this normal development. In contrast, when the present procedure of monocular suture had been followed by opening the sutured lid and suturing the other lid (reverse suture) for one week, the distribution was altered. The density of the afferents in layer I was increased while the labelled terminals in deeper layers were as segregated in and around layer IV as observed in normal kittens. Such increase in density of the afferents resulted only when the injected tracer covered the medial or intermediate part of the C complex of the lateral geniculate nucleus. To confirm these findings, geniculate neurons retrogradely labelled by horseradish peroxidase injections into layer 1 of area 17 were examined in normal and reverse-sutured kittens. In both kinds of kittens, the labelled neurons were dense in the C complex, and absent or sparse in the A laminae. But, the number was higher in reverse-sutured kittens. These results suggest an involvement of geniculocortical layer I projections in reorganization of neuronal circuits in the visual cortex.     

A periodic pattern in the distribution of cytochrome oxidase activity in the visual cortex in kittens

The aim of the present work was to study the distribution of cytochrome oxidase activity in the visual cortex of kittens in normal conditions. Studies were performed using computer filtration of digitized images of frontal sections. The occurrence of regularly alternating levels of enzyme activity was demonstrated in layers III, IV, and VI of field 17 and layers IV and VI in field 18. __________ Translated from Morfologiya, Vol. 129, No. 3, pp. 70–71, May–June, 2006.     

Organization of the visual pathways in the newborn kitten

We have used retrograde and anterograde transport to examine the major visual pathways in newborn kittens. Retinal projections from both eyes to the dorsal lateral geniculate nucleus (dLGN) and superior colliculus (SC) are present and topographically organized. The dLGN projects topographically to areas 17 and 18 and receives reciprocal projections from cells in layer VI of areas 17, 18, 19 and suprasylvian cortex on the same side of the brain. Area 19 also has a sparse thalamic input but probably not from the dLGN. The laminar distribution of [3H]proline transported from dLGN to area 17 was quantified: label was spread through all layers, with a minimum at the border of layers I/II. Layer I was always labelled less heavily than IV. These results are critically compared with those based on other tracing techniques. Cells of layer V in areas 17, 18, 19 and the suprasylvian cortex project topographically to the superficial layers of the ipsilateral SC. Area 19 and the lateral suprasylvian cortex also send a crossed projection to restricted parts of the opposite SC. Thus these visual projections are not only present and topographically ordered on the day of birth, but, unlike certain highly exuberant interhemispheric and cortico-cortical projections, they are qualitatively remarkably mature, some days before the onset of visual activity. The major subcortical projections to and from the visual cortex appear to be constructed without the benefit of visual experience and much of the activity-dependent plasticity of cortical cells may well involve only local modulation of synaptic input.     

Centrifugal and centripetal connections of the cat visual cortex

In experiments on curarized cats unit responses in the dorsal lateral geniculate body to stimulation of various zones in area 17 of the visual cortex were analyzed. Of all cells tested 69% were found to respond antidromically and 8% orthodromically; in 7.6% of cells IPSPs occurred either after an initial antidromic spike or without it. The velocities of conduction of excitation along the corticopetal fibers of the optic radiation varied from 28 to 4.3 m/sec, but the three commonest groups of fibers had conduction velocities of 28-19, 14-12, and 10-9.5 m/sec. A difference between latent periods of antidromic responses of the same neurons was found to stimulation of different zones of the visual cortex; this indicates that axons of geniculo-cortical fibers split into several branches which form contacts with several neurons in area 17 of the visual cortex. The degree and possible mechanisms of cortical influences on neurons of the lateral geniculate body are discussed.Translated from Neirofiziologiya, Vol. 8, No. 3, pp. 243–249, May–June, 1976.     

Projections from visual cortical area 19, the posterior medial lateral suprasylvian area and the lateral posterior-pulvinar complex of the thalamus to areas 17 and 18 in young kittens

Retrogradely transported horseradish peroxidase (HRP) or HRP conjugated to wheat germ agglutinin was used to demonstrate projections from area 19, the posterior medial lateral suprasylvian area (PMLS) and the lateral posterior-pulvinar complex (LP-PC) of the thalamus to areas 17 and 18 of the visual cortex in young kittens. Areas 17 and 18 in kittens, as in adult cats, receive association fibres from cells lying mainly in deep cortical laminae in area 19 and PMLS, and projections from the LP-PC of the thalamus.     

Cytochrome oxidase activity in the striate cortex and lateral geniculate nucleus of the newborn and adult macaque monkey

Summary The laminar location of cytochrome oxidase staining has been compared in the lateral geniculate nucleus and area 17 in newborn and adult macaque monkeys. In area 17 of the adult, the distribution of cytochrome oxidase activity confirmed published findings. In the newborn animals, the tissue reacted as strongly for cytochrome oxidase as in the adult but the pattern of labelling was different in two respects. Firstly in layer 1 activity was stronger and occupied a wider portion of this layer. Secondly, cytochrome oxidase staining in layer 4C occupied two separate bands, a small narrow band at the bottom of 4C and a wider one occupying the full width of 4C and spilling over into 4B. The pattern of cytochrome oxidase activity did not appear to be influenced by eccentricity in the newborn whereas, in the adult, label in 4C was more intense in cortex subserving central vision. In the lateral geniculate nucleus of the adult, the magnocellular layers and the most dorsal parvocellular layer reacted most strongly for cytochrome oxidase. In the newborn, parvocellular layers were more uniformly labelled and the difference between parvo and magnocellular layers more pronounced. These results are discussed in relationship to the development of thalamo-cortical projections in the monkey.     

Cholinergic innervation of ferret visual system

The distribution of acetylcholinesterase and choline acetyltransferase in primary visual areas of adult pigmented ferret was determined with cholinesterase histochemistry and choline acetyltransferase immunohistochemistry. In all visual areas the distribution of acetylcholinesterase in the neuropil closely matches that of choline acetyltransferase. In the cerebral cortex acetylcholinesterase and choline acetyltransferase are associated with axons found in every cortical layer and in the white matter. Area 17, identified by Nissl architectonics and cytochrome oxidase histochemistry, is distinguished by having a relatively low density of choline acetyltransferase- and acetylcholinesterase-stained axons in layer IV. Certain cortical non-pyramidal cell types show moderate staining for acetylcholinesterase after relatively long incubations, but no choline acetyltransferase-positive cells are observed in the cortex. In the lateral geniculate nucleus and superior colliculus the levels of choline acetyltransferase and acetylcholinesterase are considerably higher than in cerebral cortex, and choline acetyltransferase-stained axons there display prominent varicosities. The distribution of choline acetyltransferase and acetylcholinesterase in the neuropil of lateral geniculate nucleus and superior colliculus of ferret shows marked laminar variation. For instance, in the lateral geniculate nucleus, the levels of acetylcholinesterase and choline acetyltransferase in the "On" sublaminae of laminae A and A1 are higher than the "Off" sublaminae. In the superficial layers of the superior colliculus the levels of choline acetyltransferase and acetylcholinesterase are highest in the stratum zonale and lowest in the stratum opticum; in the intermediate gray layer of the superior colliculus acetylcholinesterase- and choline acetyltransferase-stained fibres are distributed into dense patches. As in cortex, choline acetyltransferase-positive cell bodies are not found in the lateral geniculate nucleus or superior colliculus, and acetylcholinesterase-stained cell bodies are visible only after long incubations. Cell bodies staining positively for choline acetyltransferase are found in a satellite of the superior colliculus, the parabigeminal nucleus.     

Alterations in visual evoked responses and behavior in kittens reared under constant illumination

Kittens reared with their mother under constant illumination from birth to 8 months were compared electrophysiologically, physically, and behaviorally with normally reared kittens. Initial components of visual electrocortical responses recorded from the light-reared kittens in an awake state were of considerably greater magnitude in contrast to control kittens and adults. The light-reared kittens also differed significantly in terms of minimal eye blink responses to light and to an approaching object and initially displayed continuous mydriasis independent of light-dark conditions. The kittens did not differ in orientation to objects, following objects, visual placing, and visual cliff responding.     

Does the vestibular apparatus play a role in the development of the visual system?

1. The receptive field properties of visual cortical neurones were investigated in kittens that had been subjected to either unilateral or bilateral labyrinthectomy shortly after birth.

2. Two kittens were reared in a normal visual environment. Another two were reared in the dark with recurrent exposures to vertically oriented black and white stripes, which in normal kittens is known to bias the distribution of receptive field orientations.

3. For both normally reared and stripe-reared labyrinthectomized kittens, no differences were detected in cell types, preferred orientations, binocularity, columnar organization, or any other neuronal properties, compared with similarly reared intact kittens.

4. The failure to detect deficits in visual development after labyrinthectomy is discussed in relation to other reports of vestibular influences on the visual system of the adult cat.

     

Apoptosis of Retrogradely Degenerating Neurons Occurs in Association with the Accumulation of Perikaryal Mitochondria and Oxidative Damage to the Nucleus

The mechanisms for neuronal apoptosis after axotomy and target deprivation in the adult central nervous system are poorly understood. We used a unilateral occipital cortex ablation model in the adult rat to test the hypothesis that apoptotic retrograde neurodegeneration in the dorsal lateral geniculate nucleus occurs in association with oxidative stress and mitochondrial abnormalities. Immunodetection of 8-hydroxy-2′-deoxyguanosine, a marker for oxidative injury to DNA, demonstrated that these apoptotic neurons undergo oxidative stress. Dual immunolabeling for the retrograde tracer Fluorogold to identify projection neurons and for 8-hydroxy-2′-deoxyguanosine demonstrated that apoptotic, oxidatively damaged neurons are geniculocortical projection neurons. By electron microscopy, degeneration of dorsal lateral geniculate nucleus neurons evolved in association with a transient increase in mitochondria within the perikaryon of dying neurons during the transition between chromatolysis and early apoptosis. The morphological integrity of mitochondria was preserved until late in the progression of apoptosis. The dorsal lateral geniculate nucleus ipsilateral to the cortical lesion had a transient increase in cytochrome c oxidase activity, and geniculocortical neurons at the transitional, early apoptotic stage accumulated cytochrome c oxidase activity. We conclude that axotomy-induced, retrograde neuronal apoptosis in the adult central nervous system occurs in association with the accumulation of functionally active mitochondria within the perikaryon and oxidative damage to nuclear DNA.     

Visual cortical cells: their developmental properties in normal and dark reared kittens.

582 units were recorded in area 17 in twenty-one normally reared kittens, and fourteen dark reared ones, aged between 8 and 42 days. 2. Four classes of neurones were defined: (a) non-activable cells that cannot be excited by any peripheral stimulation; (b) non-specific cells that are sensitive to a visual stimulus moving in any direction; (c) immature cells that are preferentially excited by a rectilinear stimulus but are unselective for its precise orientation; (d) specific cells that appear to be as selective for orientation as the simple or complex cells of the adult cat. 3. 23% of the cells presenting adult characteristics of specificity in terms of directionality and orientation are present in both the normally reared and in the dark reared kittens as soon as the first visual response (12 days) appears. 4. In normally reared kittens the proportion of specific cells increases with age, while that of the non-specific cells decreases. 5. Up to 3 weeks of age there is no significant difference in the proportion of the different types of cells in the dark reared from the normal kittens. But thereafter in the dark reared kittens the specific cells tend to disappear while the non-specific cells increase in number. 6. This confirms the view that cells with some highly specific response properties of the adult visual cortical neurones, especially in relation to orientation specificity, are present in the earliest stages in the absence of all visual experience. However, visual experience is necessary to maintain and develop these specific cells after the third week of post-natal life.     

Postnatal development of thalamocortical projections upon striate and extrastriate visual cortical areas in the cat

The development of visual thalamocortical projections was analyzed quantitatively by comparing, in cresyl violet-stained brain sections of early postnatal (10–17 days) and adult cats, the cell body dimensions and total cell packing density (CPD) of neuronal populations in different laminae (A, A1 and C) of the dorsal lateral geniculate (dLGN), medial interlaminar nucleus (MIN), and in lateral (LPl), intermediate (LPi) and medial (LPm) subdivisions of the lateral posterior complex. Following injections of different fluorescent tracers (FB, NY, EB, RITC) into cortical visual areas 17/18, posterior medial (PMLS) and posterior lateral (PLLS) lateral suprasylvian and anterior ectosylvian (AEV), the thalamic distribution and densities of retrogradely labeled neurons were analyzed. Projection CPDs and ratios of projection/total CPDs were determined and compared within the different thalamic components in the kitten and adult cat. A significant decrease in total cell packing density was observed in the various thalamic components of the adult cat, varying between 43% and 65%, and a marked increase in mean cell body diameter in the A, A1 and C laminae and MIN from kitten to adult (8.4±1.8 and 11.8±2.8 μm respectively) compared to the LP subnuclei (9.0±1.3 and 9.1±1.5 μm). The ratios of projection/total CPDs decreased significantly for projections upon areas 17/18 stemming from layers A and A1 (20 and 25%, respectively) and from LPi upon both PMLS (34%) and AEV (16%). Thalamocortical projections observed in the kitten from LPi upon areas 17/18 and from the A-laminae upon PMLS were absent in the adult cat. The data indicate that, in comparison to the lateral posterior nucleus, the maturation of neurons within the dLGN and MIN is incomplete with respect to cell body size during the early postnatal period. In addition, the developmental changes observed involve both reductions in the total number of thalamic neurons and a differential loss of cortical projections. The selective elimination of early cortical connections stemming from dorsal lateral geniculate laminae A and A1 and from the intermediate division of the lateral posterior nucleus may occur through a process of axon collateral withdrawal from the expanded cortical sites, thereby giving rise to the adult pattern. Accepted: 15 June 2000     

幼儿外侧膝状体及视皮质微血管的形态学

目的：探讨幼儿外侧膝状体及视皮质微血管构筑的形态结构。方法：采用8例幼儿外侧膝状体及视皮质，经碱性磷酸酶染色，组织切片，光镜观察。结果：幼儿视皮质(17区)后1／3的微血管密度最高，前1／3次之，中1／3最低。外侧膝状体后2／3的微血管密度高于前1／3。视皮质内动脉多数以直角、少数以锐角发自软脑膜动脉。视皮质内静脉数量明显少于动脉。静脉属支汇入处可见一三角形膨大，且深层微静脉粗，浅层微静脉细。结论：幼儿外侧膝状体及视皮质相对应区域微血管同步发育。皮质微静脉的这种结构特点可能是皮质微静脉栓塞的因素之一。     

Enhanced metabolic capacity of the frontal cerebral cortex after Pavlovian conditioning

While Pavlovian conditioning alters stimulus-evoked metabolic activity in the cerebral cortex, less is known about the effects of Pavlovian conditioning on neuronal metabolic capacity. Pavlovian conditioning may increase prefrontal cortical metabolic capacity, as suggested by evidence of changes in cortical synaptic strengths, and evidence for a shift in memory initially processed in subcortical regions to more distributed prefrontal cortical circuits. Quantitative cytochrome oxidase histochemistry was used to measure cumulative changes in brain metabolic capacity associated with both cued and contextual Pavlovian conditioning in rats. The cued conditioned group received tone-foot-shock pairings to elicit a conditioned freezing response to the tone conditioned stimulus, while the contextually conditioned group received pseudorandom tone-foot-shock pairings in an excitatory context. Untrained control group was handled daily, but did not receive any tone presentations or foot shocks. The cued conditioned group had higher cytochrome oxidase activity in the infralimbic and anterior cingulate cortex, and lower cytochrome oxidase activity in dorsal hippocampus than the other two groups. A significant increase in cytochrome oxidase activity was found in anterior cortical areas (medial, dorsal and lateral frontal cortex; agranular insular cortex; lateral and medial orbital cortex and prelimbic cortex) in both conditioned groups, as compared with the untrained control group. In addition, no differences in cytochrome oxidase activity in the somatosensory regions and the amygdala were detected among all groups. The findings indicate that cued and contextual Pavlovian conditioning induces sustained increases in frontal cortical neuronal metabolic demand resulting in regional enhancement in the metabolic capacity of anterior cortical regions. Enhanced metabolic capacity of these anterior cortical areas after Pavlovian conditioning suggests that the frontal cortex may play a role in the retention and regulation of learned associations.     

Participation of the lateral geniculate body in mechanisms of brain activation

The significance of the lateral geniculate body for nonspecific activation of the brain was elucidated in experiments on cats. It was established that when the connections of the lateral geniculate body remain intact, its stimulation elicits the usual activation of the EEG, but at higher threshold values of the current (120–190 A) than when the mesencephalic recticular formation of the medial center of the thalamus is stimulated (50–80 A). If only direct connections with the cortex remain, however, and the others are disrupted, the threshold for activation increases to 220–400 A. When the lateral geniculate body is coagulated, cortical activity occurs only in response to very bright light flashes (250–1000 1x). All of this indicates that, in addition to carrying out its principal function of processing and sending the basic flow of visual impulsation to higher optical centers, the lateral geniculate body may be the source of activating transmissions sent to the cortex. Non-specific stimulation that develops in the cortex is subsequently regulated by the cortex itself; the cortex plays a leading role in these processes.Translated from Fiziologicheskii Zhurnal SSSR imeni I. M. Sechenova, Vol. 68, No. 7, pp. 960–965, July, 1982.