A double-labeling investigation of the afferent connectivity to cortical areas V1 and V2 of the macaque monkey

The afferent connectivity of areas V1 and V2 was investigated using the fluorescent dyes fast blue and diamidino yellow. Simultaneous injection of each dye in retinotopically corresponding regions of these areas gave rise to two afferent populations of labeled neurons in subcortical and cortical structures which project to both areas. These two populations showed a variable degree of overlap in their spatial distribution. Neurons labeled by both dyes (double-labeled neurons) which, therefore, project to both areas, were found in substantial numbers in these overlap zones. When the injections were made in non-retinotopically corresponding regions in the two areas, both populations of labeled cells overlapped extensively in the cortex but not in subcortical structures, suggesting that the laws governing the topography of these two types of connections are different. In the cortex, the labeled neurons extended from the fundus of the lunate sulcus to the fundus of the superior temporal sulcus. A few labeled neurons were also found in the inferior temporal cortex and the parahippocampal gyrus. In all cortical regions, corticocortical neurons projecting to V1 and V2 were found in both supra- and infragranular layers, although double-labeled neurons were more numerous in infragranular layers. With increasing distance from V1 there was an increase in the proportion of neurons labeled in infragranular layers. The comparative strength of input to V1 and V2 was computed and was found to be higher to V2 in all cortical regions except the superior temporal sulcus which projected equally heavily to both areas. The superior temporal sulcus also stood out in that of all cortical regions it contained the highest proportion of double-labeled neurons. Single- and double-labeled neurons were found in a number of subcortical structures including the lateral geniculate nucleus, the inferior and lateral pulvinar, the intralaminar nuclei, the nucleus basalis of Meynert, and the amygdala. The pattern of labeling in the lateral pulvinar was in agreement with the suggestion that this structure has a complex topographical organization containing at least a dual representation of the visual field (Bender, D. B. (1981) J. Neurophysiol. 46: 672-693). In the pulvinar complex, densities of labeled neurons permitted evaluation of the strength of input to V1 and V2, the latter being the strongest. These results demonstrate that areas V1 and V2 share a vast amount of common input from the same cortical and subcortical structures and that a number of neurons project to both areas via branching axons.

Receptive field properties of neurones in visual area 1 and visual area 2 in the baboon

In order to compare the receptive field properties of cells in the striate area (visual area 1; V1), and the parastriate area (visual area 2; V2), we have recorded from 174 cells in V1 and 112 cells in V2 in five anaesthetized and paralysed baboons (Papio ursinus). The receptive fields were mapped to determine their type, size and position in the visual field, and the binocular interaction, if any. Moving and stationary optimally oriented bars were used to distinguish cells with single "on" or "off" subregions and those with more than one such subregion (S and A types) from those with overlapping "on" or "off" subregion (C and B types). The A types had larger receptive fields than S types and C types had larger receptive fields than B types, but as receptive fields increase in size with eccentricity in V1 and even more rapidly in V2, the distinction between large and small receptive fields has to be defined for the different ranges of eccentricity. In V1 there are more cells with non-oriented receptive fields than in V2. In V1 S cells are found in all cortical layers except layer 5. C cells are absent from layer 4C, but predominate in layer 5. There is a preference for horizontal and vertical orientations in S cells only. The transition in cell properties from V1 to V2 occurs in two stages. There is a strip extending from the V1-V2 border for up to 6 mm containing the representation of the visual field from -2 degrees ipsilateral to +2 degrees (contralateral) azimuth in which the cell type distribution resembles that of V1 more than that of V2. By contrast, in V2 from 2 to 10 degrees there are very few S cells, many more C cells and over three times as many cells driven only by binocular stimulation, as compared to V1.

Branching and laminar origin of projections between visual cortical areas in the cat

The laminar distribution and branching pattern of corticocortical neurons were studied in areas 17, 18, 19, 20, 21, and the lateral suprasylvian areas of the adult cat neocortex. This was done by examining the laminar position of single-labelled neurons and the proportions of double-labelled cells in these areas after paired injections of the fluorescent retrograde labels fast blue and diamidino yellow in areas 17, 18, and 19 of the ipsilateral hemisphere. After injections in areas 18 and 19, the labelled neurons in area 17 were mostly confined to the supragranular layers, with a small proportion of labelled cells in lamina 5 and upper lamina 6. Double-labelled neurons were rare and were found in the region of overlap between the two populations of labelled cells. They were mostly found in the upper laminae but a few were observed in laminae 5 and 6. The cells projecting to either area were often grouped in patches which were seen to overlap or interdigitate depending on the region examined. As a population, the neurons projecting to area 18 occupied a deeper position in laminae 2 and 3 than those projecting to area 19. Labelled cells in area 18 after injections in areas 17 and 19 were mostly found in the upper laminae with a few double-labelled cells which were restricted to the region of overlap between the two populations of labelled cells. The pattern of labelling in area 19 after injections in areas 17 and 18 was different from the one seen in areas 17 and 18. Neurons were almost equally distributed between the supra- and infragranular layers and there was a substantial proportion of double-labelled neurons (10%) which tended to belong mostly to lamina 5 and upper lamina 6. In area PMLS, the laminar position of corticocortical cells was somewhat similar to the one observed in area 19, in that a substantial number of labelled neurons were found in the deep laminae, especially after injections in 17 or 18. After injections in area 19, labelled cells were mostly found in the upper layers. Double-labelled cells were numerous (20%) when the injections were placed in areas 17 and 18 but quite rare in the other cases (17-19 and 18-19). Most of the double-labelled neurons were found in the deep layers. After injections in areas 17, 18, and 19, labelled cells were found in area 20, thus demonstrating a hitherto unknown projection from area 20 to areas 17 and 18. Labelled cells in area 20 were almost exclusively confined to the infragranular layers.(ABSTRACT TRUNCATED AT 400 WORDS)

Bifurcation of subcortical afferents to visual areas 17, 18, and 19 in the cat cortex

We have examined the pattern of axon bifurcation in the thalamic and claustral afferents to visual areas 17, 18, and 19 in the adult cat neocortex. This was achieved by injecting two fluorescent retrograde tracers, fast blue and diamidino yellow, in retinotopically corresponding regions of two of these three cortical areas. The pattern of single- and double-labelled cells was then examined in subcortical structures and the presence of double-labelled cells was interpreted as indicating that these neurons send bifurcating axons to the two injected areas. The size of the cortical region surrounding the injection site where each fluorescent dye is taken up was studied by making side-by-side injections of the two tracers in area 17 and examining the size and the separation of the two groups of labelled cells in the lateral geniculate nucleus (LGN). From these experiments we conclude that the uptake region is smaller than 1 mm and is included in the region of dense coloring surrounding the track of the injection needle. Injections were made in cortical regions which were in retinotopic correspondence as determined by electrophysiological recording. The double-labelled neurons were always found in the zone of overlap of the two populations of colored cells and no double-labelled neurons were found when there was no overlap between these populations. This indicates that the bifurcating axons send branches to strictly retinotopically corresponding regions in the two cortical areas. After injections in areas 18 and 19, numerous double-labelled cells were observed in laminae C of the LGN, in the medial interlaminar nucleus (MIN), the posterior nucleus (PN), and the lateral part of the lateral posterior nucleus (LP), in the retinorecipient zone of the pulvinar (RRZ-Pul), the intralaminar nuclei (ILN), and the claustrum. The proportions of double-labelled cells with respect to the total number of labelled neurons were computed in the region of overlap of the two populations of labelled cells. These percentages ranged between 5 and 20% and were highest in the C laminae of the LGN, the intralaminar nuclei, and the claustrum. After injection of areas 17 and 18, similar proportions of double-labelled cells were observed in the same structures, as well as in the A laminae of the LGN. Here again, the intralaminar nuclei and the claustrum tended to have slightly higher (20-30%) proportions of double-labelled cells. When the nonadjacent areas 17 and 19 were injected, doubled-labelled neurons were also observed in all these structures, except the A laminae of the LGN.(ABSTRACT TRUNCATED AT 400 WORDS)

Hypertrophic osteoarthropathy in cystic fibrosis

Seven adult patients with cystic fibrosis who had radiological evidence of hypertrophic osteoarthropathy were reviewed. In five of the patients symptoms were particularly pronounced at times of acute infective exacerbations; appropriate treatment of the infective episodes resulted in reduction or resolution of the bone pain and joint effusions. Despite this symptomatic relief periosteal changes persisted radiologically and their chronic nature was indicated by changes in the midshafts of long bones. Four of the seven patients had transient gynaecomastia or mastalgia related to infective exacerbations. It is hypothesised that a neuroendocrine mechanism--namely, release of vasoactive intestinal polypeptide--might account for the osteoarthropathy.

Transient projections from the fronto-parietal and temporal cortex to areas 17, 18 and 19 in the kitten

Using the retrograde tracers, fast blue and horseradish peroxidase we have shown the presence of projections from extensive regions of the frontoparietal and temporal cortex to areas 17, 18 and 19 in the newborn kitten. These projections are transitory as they do not exist in the adult cat. The anterograde transport of horseradish peroxidase conjugated with wheat germ agglutinin after injections in frontoparietal and temporal cortex revealed that these transitory projections terminate in the gray matter and that they could therefore play a functional role in the development of the visual cortex.

Human umbilical cord conditioned medium: a stimulus for human CFU-G

Segments of human umbilical cord have been used to prepare a highly active conditioned medium (HUCCM) for in vitro human granulopoiesis and have been compared with human placenta conditioned medium (HPCM) and feeder layers. The HUCCM produced more colonies on day 7 than HPCM (P less than 0.001), and colonies consisted almost exclusively (over 98%) of granulocytic cells by both morphological and cytochemical analysis. The HUCCM-stimulated colonies have a short culture life, the number of colonies being maximal on day 7 of culture with few colonies remaining on day 10. The main source of the colony-stimulating activity in the umbilical cord was found in the Wharton's Jelly component.

Projection of the lateral geniculate nucleus onto cortical area V2 in the macaque monkey

Recent publications have demonstrated a projection of the lateral geniculate nucleus (LGN) onto extrastriate cortical regions in the old world monkey but have failed to identify a projection from this nucleus to V2, the area adjacent to the striate cortex. In this report we show that such a projection exists, as demonstrated by the retrograde transport of the fluorescent labels fast blue (FB) and diamidino yellow (DY). Neurons labelled after V2 injections are more scattered in the LGN than the cells backfilled by the V1 injections and mostly belong to the interlaminar zones and the S layers, regions which are largely devoid of neurons labelled by the V1 injections.

Receptive field characteristics of neurones in striate cortex of newborn lambs and adult sheep

The properties of cells of the striate visual cortex (V1) have been studied in the normal adult sheep and in new-born lambs without visual experience, the majority of cells in the lamb are orientation specific, but 20% are non-oriented compared to only 3% cells in the adult. In the lamb there was little or no facilitation of binocularly-driven cells by simultaneous stimulation of both receptive fields. Cells which responded only to binocular stimulation of particular disparities ('obligate binocular' cells) were rarely encountered. In the adult, 15% of the sample were obligate binocular cells and a further 28% showed binocular facilitation. Simple and complex receptive fields were found in similar proportions in both new-born lambs and adult sheep. End-stopped cells comprised 17% of the sample in adults but only 2% in the lambs. Direction sensitive cells were found more frequently in the sheep (21% of cells) than in the lamb (4% of cells). It is concluded that facilitatory processes in binocular cells and inhibitory mechanisms generally, seem much less developed in the lamb.

Response properties of visual cortical neurons in cats reared in stroboscopic illumination

1. The response properties of 182 units were studied in the primary visual cortices (155 in area 18 and 27 in area 17) in eight cats reared from birth in a stroboscopically illuminated environment (frequency, 2/s; duration, 200 microseconds). Multihistogram quantitative testing was carried out in 82 units (64 in area 18 and 18 in area 17). Two hundred three neurons recorded and quantitatively tested in areas 17 and 18 of the normal adult cat were used for comparison. 2. Spatial characteristics of receptive fields investigated using hand-held stimuli were found to be abnormal. The correlation between receptive-field width and eccentricity was lost in area 18 and consequently, receptive fields were significantly wider in area 18 subserving central vision. Cells could be classified according to the spatial characteristics of their receptive fields. There was a much smaller proportion of end-stopped cells in strobe-reared animals. Orientation tuning in the deprived animals was normal except for a small number of cells that showed no selectivity for stimulus orientation. 3. Compilation of velocity-response curves made it possible to classify areas 17 and 18 neurons into four categories: velocity low-pass, velocity broad-band, velocity tuned, and velocity high-pass cells. The proportion of velocity high-pass cells was reduced in area 18 subserving peripheral vision, as was the proportion of velocity-tuned cells in area 18 subserving central vision. 4. In the strobe-reared animal velocity sensitivity was somewhat different from that of the normal animal. Neurons in area 18 subserving the peripheral visual field failed to respond to fast velocities. Neurons in area 17 subserving the central visual field in strobe-reared animals responded to slightly higher velocities than in the normal animal. 5. In the deprived animals the number of neurons that were selective to the direction of motion was strongly reduced. The majority of neurons failed to show a selectivity for direction at all velocities. A number of neurons could be directional at some velocities but were unreliable, since they inverted their preferred direction with velocity changes. 6. Binocular convergence onto visual cortical cells was perturbed. In area 18 the majority of neurons were driven by the contralateral eye. In area 17 most neurons could be driven only by either the ipsilateral or contralateral eye. 7. Quantitative testing (of direction selectivity, sensitivity to high velocities, response latency, and strength) and qualitative testing (receptive-field width, end stopping, and ocular dominance) showed that the normal influence of eccentricity on functional properties was strongly reduced by strobe rearing.

Vestibulo-ocular reflex and optokinetic nystagmus in adult cats reared in stroboscopic illumination

Cats reared in stroboscopic illumination (strobe reared cats) have been found to have abnormal eye movements. Visual and vestibular evoked compensatory eye movements were inefficient. Vestibulo-ocular reflex in the dark had a maximum gain of 0.6 (1.0 in normal animals). Optokinetic nystagmus had a mean gain which approached unity only at stimulus velocities around 7 degrees/S (up to 30 degrees/S in normal animals). The asymmetry of the optokinetic nystagmus resulting from monocular stimulation was more pronounced in strobe reared cat than in normal animals. Interaction between vestibulo-ocular reflex and optokinetic nystagmus to give adequate compensatory eye movements was absent in strobe reared cats: visual suppression of vestibulo-ocular reflex was absent when the animal was rotated in an illuminated environment which remained stationary with respect to the head. Optokinetic nystagmus failed to improve the gain of the vestibulo-ocular reflex when the animal was rotated in a normally lit environment. The deprived animals showed no signs of recovery after 5 months exposure to normal lighting.

Types of synapses contacting the soma of corticotectal cells in the visual cortex of the cat

Retrograde transport of horseradish peroxidase has been used to single out a distinct functional cortical cell type for ultrastructural study. Following injection of horseradish peroxidase into the superior colliculus, labelled pyramidal cells were found in layer V of the visual cortex. Examination of the labelled corticotectal cells from the visual cortex showed that their cell bodies received two types of synaptic contacts, one from boutons containing spherical vesicles and one from boutons containing flattened vesicles. The possible functional significance of this dual type of input is pointed out.

Treating monocularly deprived lambs with 4-aminopyridine produces rapid changes in ocular dominance only after short periods of deprivation

Lambs of various ages (4-30 days) were monocularly deprived for periods ranging from 4 to 51 days after which they were prepared for conventional electrophysiological recording from the striate cortex. Sufficient units were sampled to obtain a representative ocular dominance (OD) histogram. A second sample of units was then obtained after the lambs had been given an i.v. dose of 4-aminopyridine (4-AP; 0.5-5.3 mg/kg) which increases synaptic transmission. For four out of five lambs in which the deprivation had been of 4-5 days duration there was a significant increase in responsiveness of the deprived eye to stimulation after the 4-AP had been given. By contrast, only one out of four lambs which had been deprived for 19-51 days showed a significant recovery after 4-AP treatment. The results suggest that during the initial stages of monocular deprivation the deprived eye remains connected to, but is less effective in driving, cortical cells. One explanation of the failure to reactivate the deprived eye after long periods of deprivation is that the deprived eye becomes anatomically disconnected from cortical cells.

Velocity sensitivity of areas 17 and 18 of the cat

Velocity sensitivity of areas 17 and 18 of the cat has been evaluated by preparing neuronal velocity-response (VR) curves in paralyzed and anaesthetized cats. VR curves suggest two possible mechanisms for neuronal coding of stimulus velocity as well as criterion for distinguishing between cells involved in analysis of stationary or moving objects. VR curves differ between cortical areas and with retinal eccentricity. Neurones with larger receptive fields (RFs) become, on the average, sensitive to faster velocities. Parallels with human psychophysics are pointed out as support of the suggestion that the present results are relevant for our insights in human motion perception.

Predictors of ventricular fibrillation or cardiac arrest in patients hospitalized for acute myocardial infarction

A community-wide study of patients hospitalized with acute myocardial infarction in metropolitan Baltimore was conducted to examine socio-demographic and clinical characteristics in association with ventricular fibrillation and cardiac arrest (VF/CA). Multivariate analyses revealed that variables significantly associated with occurrence of VF/CA included older age (60 years or older), male sex, and a history of cigarette smoking. These factors allow the identification of subgroups of patients hospitalized with acute myocardial infarction at high risk for the subsequent development of VF/CA, in whom prophylactic therapy and close surveillance are especially recommended.