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PubMed2002

Oscillatory neuronal synchronization in primary visual cortex as a correlate of stimulus selection.

Spike and local field potential activity were recorded simultaneously from multiple sites in primary visual cortex of strabismic cats, while monocular stimulation alternated with dichoptic stimulation, inducing interocular rivalry. During interocular rivalry, there is competition between the two nonfusible stimuli presented to the two eyes, and only one stimulus is selected at any time. We biased this competition in three different ways: (1) we exploited the condition that in strabismic cats there is often one dominant eye that is selected for most of the time. (2) We presented the two stimuli with a temporal offset, which biases competition in favor of the newly appearing stimulus. (3) We presented the two stimuli with highly different contrasts, which biases competition in favor of the stimulus with higher contrast. Whenever competition was biased in favor of the stimulus activating the recorded neurons, gamma-frequency synchronization of the respective responses was enhanced, and vice versa. Firing rates showed some differences between stimulation conditions. However, when present, these changes were inversely related to a competitive advantage of the respective stimulus. We hypothesize that enhanced gamma-frequency synchronization in primary visual cortex is a correlate of stimulus selection. Synchronization is likely to be translated into firing rate changes at later processing stages.

Action Potentials↗
PubMed1995

Postnatal development of pyramidal dendritic and axonal bundles in the visual cortex of the rat.

We studied the development and spatial organization of vertically arranged pyramidal dendritic and axonal bundles in the visual cortex of the rat by using extracellular biocytin injections into frontal brain slice preparations. Vertical bundles of intracortical axons could be clearly observed at time of birth with a initial center-to-center distance of 18 microns +/- 3.1 microns. At the same time a clustering of pyramidal cell apical dendrites was completely absent. Dendritic bundles were demonstrated for the first time at postnatal day 5 when the supragranular layer 2/3 begins to differentiate. In the following weeks both axonal as well as dendritic bundles grew continuously and completely in parallel with regard to their center-to-center distances, diameters and number of elements up to their adult values at around postnatal day 90. At adulthood both types of bundles showed a center-to-center distance of 50.1 microns +/- 20.1 microns (axons) and 52.6 microns +/- 18.1 microns (dendrites), respectively. Our results demonstrate that axonal and dendritic bundles originating from the same neurons in the visual cortex of the rat correspond very well with regard to their size and distances. Developing neurons migrating along radial glia fibers group their axons together in fascicles before the lamination of the cortex is completely matured. After all layers have been developed, the apical dendrites of pyramidal cells with aggregated axons also group in clusters. The following development of axonal and dendritic bundles is presumably concerned with the volume increase of the maturating neocortex. Evidence for activity dependent plasticity after eye opening could not be found.

Age Factors↗
PubMed1994

Distinct laminar differences in the distribution of excitatory amino acid receptors in adult ferret primary visual cortex.

In order to explore the relative contributions of the different ionotropic excitatory amino acid receptor subtypes to signalling in primary visual cortex, we have mapped their distributions in area 17 of adult ferret cerebral cortex by quantitative in vitro autoradiography. D,L-alpha-amino-3-hydroxy-5-methoxy-4-isoxazole propionate (AMPA) and kainate receptors, gating fast, Na(+)-permeable channels, were localized with [3H]dizocilpine maleate ([3H]MK-801). All three radioligands bound to single sites, with KDs of 414 nM [3H]AMPA and [3H]kainate, respectively. Slower-acting N-methyl-D-aspartate receptors, which gate the influx of Ca2+ as well as Na+, were localized with ([3H]AMPA), 78 nM ([3H]kainate) and 16 nM ([3H]MK-801), and each receptor subtype displayed a different laminar distribution pattern within area 17. AMPA receptors were concentrated in superficial layers, with intermediate densities in deep layers and lowest levels in layer IV. Kainate receptor levels were high in layers V and VI and low in all other layers. N-methyl-D-aspartate receptors were more homogeneously distributed than AMPA or kainate receptors, but were expressed at highest levels in layers I and IV and lowest levels in layers V and VI. The binding site densities found in the layers containing most receptors were Bmax = 2812 fmol/mg for [3H]AMPA, Bmax = 626 fmol/mg for [3H]MK-801 maleate and Bmax = 278 fmol/mg for [3H]kainate. Thus, while AMPA receptors were predominant and kainate receptors least abundant in all cortical layers, a complementary relative distribution of excitatory amino acid receptors was apparent, with AMPA receptor density highest in superficial layers, kainate receptor density highest in inferior layers and N-methyl-D-aspartate receptor density highest in the middle granular layer, as well as in layer I. The results indicate that although AMPA receptors are principally involved in excitatory signalling in adult ferret primary visual cortex, kainate receptors in layers V and VI and N-methyl-D-aspartate receptors in layers I and IV may have particularly important roles in mediating synaptic transmission.

Animals↗
PubMed1991

Lactate rise detected by 1H NMR in human visual cortex during physiologic stimulation.

Brain lactate concentration is usually assumed to be stable except when pathologic conditions cause a mismatch between glycolysis and respiration. Using newly developed 1H NMR spectroscopic techniques that allow measurement of lactate in vivo, we detected lactate elevations of 0.3-0.9 mM in human visual cortex during physiologic photic stimulation. The maximum rise appeared in the first few minutes; thereafter lactate concentration declined while stimulation continued. The results are consistent with a transient excess of glycolysis over respiration in the visual cortex, occurring as a normal response to stimulation in the physiologic range.

Energy Metabolism↗
PubMed2001

Correlation of activation sizes between lateral geniculate nucleus and primary visual cortex in humans.

It is well established that the lateral geniculate nucleus (LGN) and the primary visual cortex (V1) are retinotopically organized. This similarity is expected to reflect a correlation of activation sizes between V1 and LGN during visual stimulation. However, it is a challenge to determine this functional correlation experimentally in the human brain using most neuroimaging techniques due to their low sensitivity for detecting small LGN activation in the thalamus. The purpose of this study was to examine the functional correlation of activation sizes between LGN and V1 during fullfield and hemifield visual stimulation using a large visual field and high-resolution fMRI technique at 4 Tesla. The correlation was determined by comparing the V1 and LGN activation size ratios between the left and right hemispheres of the same subjects. The results reveal 1) a linear correlation of functional activation size ratio between LGN and V1 with a correlation coefficient of 0.96, and 2) the capability of fMRI for quantifying spatial correlation between cortical and subcortical activation. Magn Reson Med 45:202-205, 2001.

Geniculate Bodies↗
PubMed1992

Evidence for excitatory amino acid neurotransmitters in the geniculo-cortical pathway and local projections within rat primary visual cortex.

To examine the organization of axon collaterals of neurons that selectively take up and transport excitatory amino acids, we have used retrograde tracing with D-[3H]Aspartate after injections into different layers of rat primary visual cortex. The results show cells in the lateral geniculate nucleus retrogradely labeled from the cortex. Additional topographically precise input to the thalamic recipient layer 4 originates from neurons in the visual cortex lying in layers 2/3, 5 and 6. These inputs are reciprocated by point-to-point projections from layer 4. Layer 2/3 cells project to layers 5 and 6 in columnar fashion. Putative excitatory input to layer 2/3 originates from a vertical column of cells in layer 5 and the middle of layer 6. In addition layer 2/3 receives input via horizontal collaterals of topographically distant upper layer neurons, from more widespread projections in lower layer 6, and from very widespread projections of cells at the layer 5/6 border. Cells in the depth of layer 5 also distribute collaterals within layers 5 and 6. Our findings provide anatomical evidence that the geniculo-cortical pathway in the mammalian visual system may use excitatory amino acid transmitters. In addition, the results support the notion that most long range connections that link distant points of the topographic map are excitatory.

Animals↗
PubMed1989

Organization of visual cortex in the mouse revealed by correlating callosal and striate-extrastriate connections.

In this study, we have investigated the organization of mouse visual cortex by correlating in detail the distribution of striate-extrastriate projections with the pattern of callosal connections revealed by the transport of horseradish peroxidase from the contralateral hemisphere. Single injections of 3H-proline into striate cortex produce 8-9 discrete projection fields in the belt of cortex surrounding area 17. The number and arrangement of these fields closely resemble the pattern of extrastriate visual areas in the rat. The callosal pattern is also very similar to that in the rat, and provides a set of landmarks for the location of the striate-recipient zones. Thus, cortical regions containing dense aggregations of callosal cells and terminations surround totally or partially the sparsely callosal striate-recipient zones. By comparing our results with previous accounts of the rat visual plan, we were able to identify in lateral extrastriate cortex of the mouse areas anterolateral (AL), lateromedial (LM), laterointermediate (LI), laterolateral (LL), posterolateral (PL), and posterior (P). We also observed 1-2 projections fields into anteromedial (AM) extrastriate cortex, and one field (S) into the posteromedial border of the head representation in primary somatosensory cortex. Our results support the notions that the visual cortex in the mouse is subdivided into multiple visual areas, and that these areas are arranged according to a plan that is common in rodents.

Animals↗
PubMedDate not supplied

Cytochrome oxidase in the human visual cortex: distribution in the developing and the adult brain.

Cytochrome-oxidase (CO) histochemistry has revealed important functional subdivisions, modules, and processing streams in the macaque visual cortex. The present study is aimed at analyzing the development and characteristics of CO patterns in the human visual cortex by means of histochemistry and immunohistochemistry. At 26 weeks of gestation, both the ventricular and subventricular zones had low levels of CO, while the cortical plate had moderate levels of CO. At birth, supragranular CO-rich zones (puffs) were not clearly organized, indicating that the development of puffs in the neonatal striate cortex lags behind that of the macaque monkey, whose puffs appear weeks before birth. Puffs were more clearly discernible in human cortex at postnatal day 24, and became well organized by the fourth postnatal month. Layer IVc alpha in the neonate exhibited a higher level of activity and amount of CO than the central portion of IVc beta, which contained a dense aggregate of small neurons. The base of IVc beta, however, was often as CO reactive as IVc alpha. In contrast, the majority of specimens available to us from the fourth postnatal month and from adults with no known neurological diseases had significantly greater CO reactivity in layer IVc beta than in IVc alpha. Layer VI was moderately reactive for CO throughout development. In V2, stripes with globular zones of high CO activity were sporadically present at birth, suggesting that their development may parallel or precede that of puffs in V1. These stripes with CO-rich globular zones became more prominent in the adult and radiated orthogonally from the V1/V2 border. They were not, however, clearly organized into alternating thick and thin stripes as they are in the squirrel monkey. Visual cortical areas beyond V2 exhibited high CO activity mainly in layers III and IV and moderate levels in VI, suggesting that sites associated with cortico-cortical pathways may be metabolically most active.

Adult↗
PubMed1979

The development of the binocular depth cells in the secondary visual cortex of the lamb.

In most respects, the response properties of cells in the secondary visual cortex of the newborn lamb were indistinguishable from those in the adult. The cells were sharply selective to orientation; the orientation preferences were the same in each eye, and they varied systematically as the electrode penetrated the cortex. The receptive-field organization did not differ noticeably from that in adults, and complex, hypercomplex, and a few simple cells were all observed. The ocular dominance distribution was similar to that in the adult. Most importantly, binocular cells were found with disparate receptive fields even in newborn, visually inexperienced animals. As in the adult, the disparities were largely horizontal, and they appeared to be arranged in columns. Many of the cells responded preferentially to a binocular stimulus at a particular disparity setting (often approximately zero), but unlike those in the adult almost all the binocular cells in the newborn lamb would also respond monocularly, and the enhancement at the optimal disparity was less than in the adult. The full development of binocular selectivity took several weeks, and was blocked by binocular deprivation. We conclude that the basic wiring of stereoscopic mechanisms is innate, but the development of mature binocular interaction may depend on an adaptive process which makes use of the visual information received during binocular stimulation.

Aging↗
PubMed2000

Calcium-binding proteins calbindin D28K, calretinin, and parvalbumin immunoreactivity in the rabbit visual cortex.

The distribution and morphology of neurons containing three calcium-binding proteins, calbindin D28K, calretinin, and parvalbumin in the adult rabbit visual cortex were studied. The calcium-binding proteins were identified using antibody immunocytochemistry. Calbindin D28K-immunoreactive (IR) neurons were located throughout the cortical layers with the highest density in layer V. However, calbindin D28K-IR neurons were rarely encountered in layer I. Calretinin-IR neurons were mainly located in layers II and III. Considerably lower densities of calretinin-IR neurons were observed in the other layers. Parvalbumin-IR neurons were predominantly located in layers III, IV, V, and VI. In layers I and II, parvalbumin-IR neurons were only rarely seen. The majority of the calbindin D28K-IR neurons were stellate, round or oval cells with multipolar dendrites. The majority of calretinin-IR neurons were vertical fusiform cells with long processes traveling perpendicularly to the pial surface. The morphology of the majority of parvalbumin-IR neurons was similar to that of calbindin D28K: stellate, round or oval with multipolar dendrites. These results indicate that these three different calcium-binding proteins are contained in specific layers and cells in the rabbit visual cortex.

Animals↗
PubMed1981

Influence of morphine and haloperidol on the bioelectrical activity of n. raphe, n. caudatus, s. nigra and the visual cortex of cats.

The changes in the bioelectrical activity of n. raphe dorsalis (RD), s. nigra (SN), n. caudatus (NC) and the visual cortex (VC), induced by administration of morphinee, haloperidol, and morphine after pretreatment with haloperidol, were studied in acute experiments on 18 cats. Morphine caused changes in RD and NC, characteristic of increased excitability (increase in the amplitude and frequency of the spontaneous EEG-activity, improved assimilation upon light stimulation, higher amplitudes of the evoked potential). These phenomena were most marked until the 30th min, then they gradually decreased. In SN the bioelectrical activity was inhibited. After the initial changes suggesting inhibition, excitation phenomena occurred in the visual cortex after the 30th min. Haloperidol in SN caused changes characteristic of excitation, while in NC and VC--of inhibition. After pretreatment with haloperidol, morphine prevented its effects in all structures studied. The authors assume that the EEG-effects of morphin are conditioned both by its direct action on the serotoninergic neurones in RD and by the changes in the relationships between serotoninergic and dopaminergic neurones in RD, SN and NC.

Animals↗
PubMed1992

The effects of dark-rearing on the electrophysiology of the rat visual cortex.

Our previous two studies have shown that dark-rearing affects the morphology and chemistry of adult rat primary visual cortex (area 17). In this study we demonstrate correlated physiological alterations with single unit recordings in the same preparation. Rats were raised from birth in either 14 h light/10 h dark (Lt/Dk) or in total darkness (Dk). At the age of 3 months, single units were recorded in area 17 of both groups. The cortical cells of Dk animals showed significantly more spontaneous activity during ambient lighting. The mean rate of randomly appearing spontaneous activity was greatly increased in Dk animals. Moreover, many cells in Dk animals also exhibited a particular type of spontaneous activity which occurred as 'bursts' of spikes, i.e. quantified groupings of fast firing spikes, separated by randomly appearing spontaneous activity. The mean number of bursts per min seen in Dk animals was also significantly more than any such activity seen in Lt/Dk animals. Visual stimuli consisted of white or dark bars moving with different orientations and directions at slow and fast speeds, and full field flashes. In response to moving stimuli, notably fewer cells were orientation- or direction tuned in dark-reared animals, and when they did respond to moving bar stimuli, the responses were of relatively longer duration. The pathologically high spontaneous activity rate, as well as lack of tuning and relatively prolonged duration of responses to moving stimuli indicate that intracortical inhibitory mechanisms are seriously compromised in both the unstimulated and stimulated states and is in agreement with our previous findings (Bakkum, B.W., Port, J.D., Cohen, R.S. and Benevento, L.A., Soc. Neursci. Abst., 15 (1989) 797) of a decreased number of synapses and GABA-containing cells in the visual cortex of the same preparation. Other evidence suggests that there may be a decrease in stimulus-bound excitatory drive. Significantly fewer cells in Dk animals were excited by all visual stimuli, and responses elicited by flashes had relatively longer 'on' latencies, relatively shorter durations, and were generally weaker. This may correlate with our finding of a significantly smaller number of perforated postsynaptic densities in the cortex of the same preparation (Bakkum, B.W., Benevento, L.A. and Cohen, R.S., J. Neurosci. Res., 23 (1991) 65-80).

Action Potentials↗
PubMed1976

[Studies on the spine density in lamina V pyramidal cells of the visual cortex in young and subadult rats after dark-rearing and destruction of the dorsal nucleus in the lateral geniculate body].

1. Dark reared 50 days old rats have a significantly diminuished number of spines at the apical dendrite of the lamina-V-pyramidal cells in the visual cortex. 2. Likewise we could ascertain a significant diminution of spines after destroying the upsilateral Cgld. The topistical distribution of spine density differs in both investigated series. 3. The spine diminution at the apical dendrites of lamina-V-pyramidal cells differs in this way: pyramidal cells with thick apical dendrites show a weaker spine diminution than the pyramidal cells with thin apical dendrites. 4. Some topistical problems concerning specific afferents in the visual cortex are discussed.

Age Factors↗
PubMed1989

Actions of excitatory amino acid antagonists on synaptic potentials of layer II/III neurons of the cat's visual cortex.

Actions of excitatory amino acid (EAA) antagonists on the responses of cells in layers II/III and IV of the cat's visual cortex to stimulation of layer VI and the underlying white matter were studied in slice preparations. Antagonists used were 2-amino-5-phosphonovalerate (APV), a selective antagonist for the N-methyl-D-aspartate (NMDA) type of EAA receptors, and kynurenate, a broad-spectrum antagonist for the three types of EAA receptors. In extracellular recordings it was demonstrated that most of the layer II/III cells were sensitive to APV, while the great majority of the layer IV cells were not. By contrast, kynurenate suppressed the responses completely in both layers. Excitatory post-synaptic potentials (EPSPs) evoked by stimulation of layer VI and the while matter were recorded intracellularly from layer II/III neurons. To determine whether the EPSPs were elicited mono- or polysynaptically, the synaptic delay for each EPSP was calculated from a pair of onset latencies of EPSPs evoked by stimulation of the two sites. Forty-two percent of the layer II/III cells were classified as having monosynaptic EPSPs. In 60% of these monosynaptic cells, the rising slope of the EPSPs was reduced by APV while in the other 40%, it was not. In the former (APV-sensitive cells), subtraction of the APV-sensitive component from the total EPSP indicated that the onset latency of the NMDA receptor-mediated component was roughly equal to that of the non-NMDA component. In the latter (APV-resistant cells), only the slowly-decaying component was in part mediated by NMDA receptors. The conduction velocities of the afferent fibers innervating APV-resistant cells were slower than those of the APV-sensitive cells, suggesting that both types of cells are innervated by different types of afferents. The polysynaptic EPSPs of almost all layer II/III cells were sensitive to APV. The subtraction method indicated that the NMDA component had about the same magnitude as the non-NMDA components. When the slices were superfused by a Mg2+-free solution, the EPSPs were potentiated dramatically, but this potentiation was reduced to the control level during the administration of APV. Similarly, APV-sensitive components were potentiated during the administration of bicuculline, a selective antagonist for gamma-aminobutyric acid receptors of A type. These results suggest that NMDA receptors participate, at varying degrees, in excitatory synaptic transmission at most layer II/III cells in the cat's visual cortex, and their actions appear to be regulated by intracortical inhibition.

2-Amino-5-phosphonovalerate↗
PubMed1993

Cytochemical redistribution of 5'-nucleotidase in the developing cat visual cortex.

The adenosine-producing ectoenzyme 5'-nucleotidase has recently been shown to undergo a marked redistribution during development of the cat visual cortex and to be involved in the remodelling of ocular dominance columns (Schoen et al., J. Comp. Neurol., 296, 379-392, 1990). Using an enzyme-cytochemical technique, we now investigate the developmental redistribution of 5'-nucleotidase activity in area 17 of kittens at the ultrastructural level. Between postnatal days 35 and 42, when 5'-nucleotidase is concentrated in layer IV, enzyme reaction product occupies the clefts of asymmetrical synapses within the neuropil. During later development (9th and 13th postnatal weeks), when 5'-nucleotidase spreads over all cortical laminae, the enzyme disappears from its synaptic localization and becomes increasingly associated with astrocytic membranes. The transient appearance of 5'-nucleotidase at synapses parallels the time-course and laminar profile of the synaptic remodelling which takes place during the critical period of visual cortex development. This suggests that synapse-bound 5'-nucleotidase activity plays a role in synaptic malleability, whereas its later association with glial profiles is likely to reflect other functions of the enzyme.

5'-Nucleotidase↗
PubMed1993

Development and regulation of beta adrenergic receptors in kitten visual cortex: an immunocytochemical and autoradiographic study.

The developmental pattern and laminar distribution of beta 1 and beta 2 adrenergic receptor subtypes were studied in cat visual cortex with autoradiography using [125I]iodocyanopindolol as a ligand and also with immunocytochemistry using a monoclonal antibody directed against beta adrenergic receptors. In the primary visual cortex of adult cats, the laminar distributions of both beta 1 and beta 2 adrenergic receptors revealed by autoradiography were very similar, with concentrations in layers I, II, III and VI. In young kittens (postnatal days 1 and 10), fewer beta adrenergic receptors were present, and they were concentrated in the deep cortical layers (V-VI) and subcortical white matter. Between postnatal days 15 and 40, beta adrenergic receptors increased in density more quickly in the superficial layers than they did in the deep and middle cortical layers. By postnatal day 40, the adult pattern was achieved, with two bands of intense binding in the superficial and deep cortical layers and a lower density in layer IV. Immunocytochemical techniques applied to adult cat cortex showed that beta adrenergic receptor-like immunoreactivity was found in different populations of neurons and glial cells. The immunoreactive neural cells were most dense in layers II, III and VI. About 50% of these immunoreactive neural cells were glial cells, primarily astrocytes. Immunoreactive pyramidal cells were mostly located in layers III and V. In layer IV, many stellate cells were stained. Immunoreactive astrocytes in the subplate and white matter progressively increased in number during development until adulthood. The pattern of laminar distribution and the developmental process was not affected by interrupting noradrenergic innervation from locus coeruleus either before or after the critical period. However, when visual input was interrupted by lesions of the lateral geniculate nucleus in young kittens (postnatal day 10), the density of both beta adrenergic receptor subtypes decreased significantly in the deep cortical layers. Lateral geniculate nucleus lesions in adult cats resulted in a pronounced decrease in beta adrenergic receptor density in layer IV.

Aging↗
PubMed1990

Long-term depression but not potentiation is induced in Ca(2+)-chelated visual cortex neurons.

An entry of Ca2+ into postsynaptic sites may play a role in the induction of long-term potentiation (LTP) of synaptic transmission in the visual cortex. To test this hypothesis, a Ca(2+)-chelator was injected into layer II/III neurons of sliced visual cortex obtained from young rats, and excitatory postsynaptic potentials (EPSPs) of these cells to test stimulation of the white matter were observed before and after tetanic stimulation of the same site. To confirm the effectiveness of the tetanus, field potentials reflecting the activities of many cells were recorded with another extracellular electrode. The chelator injection led to long-term depression (LTD) of EPSPs following tetanic stimuli which simultaneously induced LTP of field potentials derived from unchelated cells in most of the slices tested. This suggests that a low concentration of post-synaptic, free Ca2+, when associated with tetanic inputs, may lead to LTD while a rise of Ca2+ may lead to LTP.

Animals↗