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Monkeys whose optic chiasm and forebrain commissures had been sectioned and control monkeys with only the optic chiasm cut were tested for interocular transfer of discriminations based on direction of movement. Only the control animals showed transfer to the untrained eye, which suggests that discrimination of movement, like pattern, is a function strongly dependent on the cortex.
The responses of cells in the visual cortex to stimulation of the two eyes changes dramatically following a period of monocular visual deprivation (MD) during a critical period in early life. This phenomenon, referred to as ocular dominance (OD) plasticity, is a widespread model for understanding cortical plasticity. In this study, we designed stimulus patterns and quantification methods to analyze OD in the mouse visual cortex using optical imaging of intrinsic signals. Using periodically drifting bars restricted to the binocular portion of the visual field, we obtained cortical maps for both contralateral (C) and ipsilateral (I) eyes and computed OD maps as (C - I)/(C + I). We defined the OD index (ODI) for individual animals as the mean of the OD map. The ODI obtained from an imaging session of less than 30 min gives reliable measures of OD for both normal and monocularly deprived mice under Nembutal anesthesia. Surprisingly, urethane anesthesia, which yields excellent topographic maps, did not produce consistent OD findings. Normal Nembutal-anesthetized mice have positive ODI (0.22 +/- 0.01), confirming a contralateral bias in the binocular zone. For mice monocularly deprived during the critical period, the ODI of the cortex contralateral to the deprived eye shifted negatively towards the nondeprived, ipsilateral eye (ODI after 2-day MD: 0.12 +/- 0.02, 4-day: 0.03 +/- 0.03, and 6- to 7-day MD: -0.01 +/- 0.04). The ODI shift induced by 4-day MD appeared to be near maximal, consistent with previous findings using single-unit recordings. We have thus established optical imaging of intrinsic signals as a fast and reliable screening method to study OD plasticity in the mouse.
The present study investigates the functional connections of different parts of the medial-most folium of crus I in the cat cerebellar hemisphere. Three areas were identified physiologically by recording on the cerebellar surface climbing fibre (CF) field potentials evoked by electrical stimulation of different body sites. From medial to lateral in relation to the long axis of the folium, area 1 receives convergent input from all body sites tested (optic chiasm, ipsilateral periorbital region, ipsilateral and contralateral forelimbs), area 2 receives input mainly from the ipsilateral periorbital region, while area 3 receives input mainly from the optic chiasm. These physiological differences were used to guide injections of bi-directional tracer material into individual cortical areas. The inferior olive and cerebellar nuclei were then mapped, revealing a precise topography within the olivo-cerebellar and cortico-nuclear projections for each area. On the basis of their anatomical and physiological characteristics areas 1, 2 and 3 correspond to zones C2, C3 and D1, respectively. CF inputs arise from the rostral medial accessory olive (C2), the interface between the rostral dorsal accessory olive and ventral lamella of the principal olive (vlPO, C3), and from vlPO (D1). The corresponding cortico-nuclear projections are nucleus interpositus posterior (C2), the transitional region between the dentate nucleus and nucleus interpositus anterior (C3), and the dentate nucleus (D1). Overall, the results provide a comprehensive description of the functional localization of different zones within crus I (folium 1), and suggest that a potent source of CF input to the C2 and D1 zones within this region of cortex arises from visual pathways.
We introduce the singular-optics approach for classification of rough surfaces with large-scale inhomogeneities into random and fractal surfaces. The maps of amplitude zeros of a field versusthe parameters of the rough surfaces and the position of the observation zone are obtained and analyzed. It is shown that the local density of amplitude zeros in the scattered field serves as an appropriate parameter with which to classify the surface of interest into a surface with a height distribution that can be described as a random or a fractal process.
This study evaluated the effects of the topical beta1-adrenergic antagonist betaxolol and the non-selective beta-adrenergic antagonist timolol on the choroidal pressure-flow relationship. Pentobarbital-anesthetized rabbits were instrumented with hydraulic occluders on the aorta and inferior vena cava to control MAP, an ear artery cannula to measure mean arterial pressure (MAP), and two vitreous cannulas to control and measure intraocular pressure (IOP). Choroidal blood flow was measured by laser Doppler flowmetry with the fiber-optic probe tip positioned over the posterior pole. Choroidal pressure-flow curves were obtained before and 30 min after topical application of 0.1 ml of betaxolol (Betoptic, 0.5%, n=10), timolol (Timoptic, 0.5%, n=10) or saline (n=8) by varying the MAP without controlling the IOP and by raising IOP while holding the MAP constant at 70 mmHg. The IOP was significantly reduced by betaxolol and timolol but not by saline. MAP was also slightly, but significantly, reduced after betaxolol but not after timolol or saline. However, the systemic hypotensive response to isoproterenol (8 microgram/kg, i.v.) was blunted after betaxolol and timolol indicating appreciable systemic absorption of both drugs. Timolol, but not betaxolol or saline, caused a significant, small increase in baseline choroidal vascular resistance. Timolol also attenuated the IOP response to MAP; however, none of the treatments had a significant effect on the choroidal pressure-flow relationship. We conclude that both drugs reach the systemic circulation after topical application, but neither betaxolol nor timolol alter the choroidal response to acute changes in perfusion pressure.
The visual capacity of the common barn owl (Tyto alba) was studied by quantitative analysis of the retina and optic nerve. Cell counts in the ganglion cell layer of the whole-mounted retina revealed a temporal area centralis with peak cell density of 12,500 cells/mm2 and a horizontal streak of high cell density extending from the area centralis into the nasal retina. Integration of the ganglion cell density map gave an estimated total of 1.4 million cells for the ganglion cell layer. Electron microscopy of a single, complete section of the optic nerve revealed a bimodal fiber diameter spectrum (modes at 0.3 and 0.9 microns; bin width = 0.2 microns), with diameters ranging from 0.15 microns (unmyelinated) to 6.05 microns (myelinated, sheath included). The total axon count for the optic nerve was estimated from sample counts to be about 680,000 axons (25% unmyelinated). Therefore, roughly half of the cells in the retinal ganglion cell layer do not send axons into the optic nerve. With certain assumptions, the data predict a visual spatial acuity for barn owls on the order of 8 cycles/degree, a value similar to the known behaviorally measured acuities of masked owls (10 cycles/degree) and domestic cats (6 cycles/degree).
In the visual system of young kittens, the layout of the cortical maps for ocular dominance and orientation preference converges to an equilibrium state within the first few weeks of life and normally remains largely unchanged. If during the critical period, however, patterned visual experience is restricted to only one eye for a few days, cortical neurons lose their ability to respond to stimulation of the deprived eye. We used the 'reverse occlusion' protocol together with chronical optical imaging to investigate how the profound anatomical changes accompanying monocular deprivation affect the spatial pattern of the cortical orientation preference map. We report here that after 1 week of monocular deprivation, cortical orientation maps for the deprived eye had vanished. But we also discovered that after subsequent reverse occlusion the restored orientation maps were very similar to the original maps. This demonstrates that in spite of functional disconnection of one eye after monocular deprivation, the layout of cortical orientation maps, when re-established for this eye, is not formed from scratch but is strongly influenced by previous experience.
An abnormal, ipsilateral projection was formed by deflecting optic fibers that normally innervate the posterior part of one tectum into the anterior end of the opposite tectum. When anterior recipient tectum was simultaneously denervate, the deflected fibers formed a retinotopic map in this region that was reversed with respect to the anterior-posterior tectal axis.
PURPOSE: To introduce high-resolution, digital three-dimensional (3-D) reconstruction of the connective tissues of the optic nerve head (ONH). METHODS: Trephinated ONH and peripapillary sclera from both eyes of three monkeys with early glaucoma (EG; one eye normal, one eye given laser-induced EG) were embedded in paraffin and serial sectioned at 3-mum thickness from the vitreous surface through the orbital optic nerve, with the embedded tissue block face stained and imaged after each cut. Each image was aligned, and then the scleral canal wall, sclera, border tissue of Elschnig, Bruch's membrane, lamina cribrosa, optic nerve septa, pial sheath, and vasculature were delineated as unique objects. Delineated images were stacked, color mapped, and volume rendered and then serial sagittal and transverse digital sections of the resultant voxel geometries were viewed and measured. RESULTS: Substantial differences in the 3-D architecture of the peripapillary sclera, scleral canal wall, and lamina cribrosa were present among the three normal eyes. All three EG eyes displayed permanent posterior deformation of the central lamina cribrosa, as well as expansion of the anterior and posterior neural canal openings in comparison with their respective contralateral normal control eyes. Peripherally, whereas laminar deformation was greatest inferiorly or superiorly in all three EG eyes, statistically significant deformation was present in all four quadrants of all three eyes. CONCLUSIONS: High-resolution, digital 3-D reconstructions of the load-bearing connective tissues of the monkey ONH confirm that the ONH connective tissues are profoundly altered at the onset of detectable ONH surface change in experimental glaucoma.
The total number of neurons within six subdivisions of the rat basal ganglia was estimated using unbiased stereological counting methods and systematic random sampling techniques. Six young adult rats were perfuse-fixed, their right cerebral hemispheres were embedded in glycolmethacrylate, and a complete set of serial 40-mu m sections was cut through each hemisphere. After a random start, a systematic subset (e.g., every tenth) of these sections was used to estimate the total volume of each subdivision using Cavalieri's method. The same set of sampled sections was used to estimate the number of neurons in a known subvolume (i.e., the Nv) by the optical disector method. The product of the total volume and the Nv by these methods yields an unbiased estimate of the total number of neurons. It was found that the right basal ganglia consisted, on average, of 2.79 million neostriatal or caudate-putamen neurons (with a coefficient of variation of 0.07), 46,000 external globus pallidus neurons (0.11), 3,200 entopeduncular/internal globus pallidus neurons (0.10), 13,600 subthalamic neurons (0.10), 7,200 substantial nigra pars compacta neurons (0.15), and 26,300 substantia nigra pars reticulata neurons (0.07).
1. The superior colliculus (SC)/optic tectum is a multi-layered midbrain area that harbours representations of visual and auditory space and somatic body surface. The development and maintenance of these sensory maps has been shown to involve activity and experience-dependent mechanisms. 2. The implantation of an extra eye primordium into the developing forebrain of Rana pipens results in the formation of dually innervated tecta that would have normally be solely innervated by the contralateral retina. The retinal projections are arranged in an interdigitating pattern of alternate stripes of terminations from each retina. The establishment of this striped pattern requires retinal activity and depends on N-methyl-D-aspartate (NMDA) receptors. Manipulation of protein kinase activity leads to the formation of an abnormal stripe pattern. 3. Regeneration of the goldfish retinotectal projection, following crush of the optic nerve, occurs in an activity dependent manner involving NMDA receptors. Furthermore, a critical period exists, during which retinal activity is vital for reformation of the visual map. Protein kinase manipulations during this period disrupt normal reformation. The same manoeuvres at other time points have little effect on map reformation. 4. An unusual form of long-term potentiation (SC-LTP) has been demonstrated in the in vitro preparation of the guinea-pig SC. By stimulating the optic layer of the SC, a postsynaptic potentiation can be recorded in the superficial grey layer. The expression of SC-LTP is masked but not prevented by blockade of NMDA receptors. The role of protein kinases in this form of synaptic modification has also been studied using various manipulations and inhibitors with varying substrate specificity. Whereas H7, an inhibitor reputed to be protein kinase C specific, only masks the expression of SC-LTP, K252a which has a broad substrate specificity blocks the induction of SC-LTP. 5. Experience-dependent formation of the auditory space map in the deeper layers of the SC is believed to be under the instruction of the visual representation in the superficial layers. Furthermore, a crucial period exists during which normal auditory and visual experience are required for successful establishment of the auditory map. Chronic exposure to 5-aminophosphonopentanoic acid (AP5) during this time prevents the formation of the map. Chronic exposure to K252a, a broad kinase inhibitor, over the same time period, also disrupts the formation of the auditory space map. 6. Taken together, these models emphasise the role of protein kinases in synaptic plasticity observed in the SC. Furthermore, interference with protein kinase activity at crucial stages of regeneration or development appears to disrupt the sequence of events that lead to the consolidation of SC receptive fields.
Quantitative descriptors of corneal topography determined by computerized algorithm and designed to augment the information derived from topographic maps were evaluated in a clinical study. The surface regularity index, a measure of central corneal optical quality, was highly correlated with best spectacle-corrected visual acuity (rho = 0.80, P less than .001). The relatively low correlation between the surface asymmetry index, a measure of central corneal asymmetry, and best spectacle-corrected visual acuity (rho = 0.62, P less than .005) suggests that corneal symmetry is a lesser but still important determinant of the optical performance of the anterior corneal surface. There was also a high correlation between factors determined from computer-generated orthogonal simulated keratometer values and clinical keratometry values (mean corneal power, total corneal cylinder, and the location of the steepest corneal meridian). The information derived from these algorithms has both clinical and research applications and can be incorporated into computer-assisted topographic analysis systems.
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By injecting one lateral geniculate nucleus with large amounts of horseradish peroxidase (HRP), we have determined the retinal distributions of contra- and ipsilaterally projecting retinothalamic ganglion cells in the Siamese cat. In accord with the data of others, we observe that large numbers of temporal ganglion cells, which normally send axons ipsilaterally, instead misproject to the contralateral thalamus. However, in contrast to the expectations raised by previous work, we do not find the Siamese defect to be a simple 20 degrees shift of the naso-temporal decussation line. Rather, there is intermingling of the crossed and uncrossed retinothalamic populations in the temporal retina, with a gradual increase in the proportion of ipsilaterally projecting ganglion cells as one moves temporally. Thus, the Siamese abnormality represents not only a temporal displacement of the retinothalamic decussation line, but also a smearing of the normally rather sharp division between regions of ipsilateral and contralateral projection. Cell size measurements and anterograde transport of H3-proline confirm the HRP findings and suggest differential effects of the Siamese abnormality according to ganglion cell class. In particular, it appears that the large ganglion cells to misproject to a greater degree than the rest of the retinothalamic population.
Utilizing the horseradish peroxidase retrograde tracing technique and the 2-deoxy-D-glucose metabolic mapping technique, we have demonstrated in chickens the distribution of retinal ganglion cells that project to the lentiform nucleus of the mesencephalon (LM) and the retinotopic organization of the projection in the LM. Retinal ganglion cells labeled after a nearly complete injection into the LM were found in the four quadrants, distributed in a wide horizontal belt lying along both sides of the retinal equator and stretching from the temporal to the nasal retina. The HRP-labeled cells, which appeared round or oval, ranged from 25 to 840 micron 2 in size with most in the smaller size range. Results of partial HRP injections into the LM and metabolic mapping patterns in the LM produced by stimulation of half the retina with horizontal visual motion suggest that there is an orderly mapping of the retina onto the LM. The inferior temporal quadrant projects to the rostrodorsal LM; the inferior nasal quadrant projects to the caudodorsal LM. The superior temporal quadrant projects to the middle and ventral LM, extending from the rostral to the caudal pole, whereas the superior nasal quadrant projects to a small zone in the caudal LM. The mapping of the retinal quadrants in the LM is remarkably similar to that reported in the optic tectum of birds. We suggest that a common embryological anlage with the optic tectum and the arrangement of retinal axons in the optic tract are important factors in establishing the retinotopic organization of the LM.
Fingerprint recognition technology is an important part of criminal investigations it is the basis of some security systems and an important tool of government operations such as the Immigration and Naturalization Services, registration procedures in the Armed Forces, and so forth. After the tragic events of September 11, 2001, the importance of reliable fingerprint recognition technology became even more obvious. In the current study, pressure-induced changes of distances between ridges of a fingerprint were measured. Using calibrated silicon pressure sensors we scanned the distribution of pressure across a finger pixel by pixel, and also generated maps of an average pressure distribution during fingerprinting. Emulating the fingerprinting procedure employed with widely used optical scanners, we found that on average the distance between ridges decreases by about 20% when a finger is positioned on a scanner. Controlled loading of a finger demonstrated that it is impossible to reproduce the same distribution of pressure across a given finger during repeated fingerprinting procedures.
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Neurons and glioblasts that arise in the ventricular zone migrate to form discrete nuclei and laminae as the central nervous system develops. By stably labeling precursor cells in the ventricular zone, pathways taken by different cells within an individual clone can be described. We have used recombinant retroviruses to label precursor cells with a heritable marker, the E. coli lacZ gene; clones of lacZ-positive cells are later mapped histochemically. Here we review results from three regions of the chicken central nervous system--the optic tectum, spinal cord, and forebrain--and compare them with previous results from mammalian cortex and other regions of the vertebrate CNS. In particular, we consider the relationship between migratory patterns and functional organization, the existence of multiple cellular sources of migratory guidance, and the issue of whether a cell's choice of migratory pathway influences its ultimate phenotype.