Cytochrome Oxidase Patterns Research Articles

The Expression Patterns of Cytochrome Oxidase and Immediate-Early Genes Show Absence of Ocular Dominance Columns in the Striate Cortex of Squirrel Monkeys Following Monocular Inactivation.

Because at least some squirrel monkeys lack ocular dominance columns (ODCs) in the striate cortex (V1) that are detectable by cytochrome oxidase (CO) histochemistry, the functional importance of ODCs on stereoscopic 3-D vision has been questioned. However, conventional CO histochemistry or trans-synaptic tracer study has limited capacity to reveal cortical functional architecture, whereas the expression of immediate-early genes (IEGs), c-FOS and ZIF268, is more directly responsive to neuronal activity of cortical neurons to demonstrate ocular dominance (OD)-related domains in V1 following monocular inactivation. Thus, we wondered whether IEG expression would reveal ODCs in the squirrel monkey V1. In this study, we first examined CO histochemistry in V1 of five squirrel monkeys that were subjected to monocular enucleation or tetrodotoxin (TTX) treatment to address whether there is substantial cross-individual variation as reported previously. Then, we examined the IEG expression of the same V1 tissue to address whether OD-related domains are revealed. As a result, staining patterns of CO histochemistry were relatively homogeneous throughout layer 4 of V1. IEG expression was also moderate and homogeneous throughout layer 4 of V1 in all cases. On the other hand, the IEG expression was patchy in accordance with CO blobs outside layer 4, particularly in infragranular layers, although they may not directly represent OD clusters. Squirrel monkeys remain an exceptional species among anthropoid primates with regard to OD organization, and thus are potentially good subjects to study the development and function of ODCs.

Spatial specificity of the functional MRI blood oxygenation response relative to neuronal activity

Previous attempts at characterizing the spatial specificity of the blood oxygenation level dependent functional MRI (BOLD fMRI) response by estimating its point-spread function (PSF) have conventionally relied on retinotopic spatial representations of visual stimuli in area V1. Consequently, their estimates were confounded by the width and scatter of receptive fields of V1 neurons. Here, we circumvent these limits by instead using the inherent cortical spatial organization of ocular dominance columns (ODCs) to determine the PSF for both Gradient Echo (GE) and Spin Echo (SE) BOLD imaging at 7 Tesla.By applying Markov chain Monte Carlo sampling on a probabilistic generative model of imaging ODCs, we quantified the PSFs that best predict the spatial structure and magnitude of differential ODCs' responses. Prior distributions for the ODC model parameters were determined by analyzing published data of cytochrome oxidase patterns from post-mortem histology of human V1 and of neurophysiological ocular dominance indices. The average PSF full-widths at half-maximum obtained from differential ODCs’ responses following the removal of voxels influenced by contributions from macroscopic blood vessels were 0.86 mm (SE) and 0.99 mm (GE). Our results provide a quantitative basis for the spatial specificity of BOLD fMRI at ultra-high fields, which can be used for planning and interpretation of high-resolution differential fMRI of fine-scale cortical organizations.

Retinotopic organization of extrastriate cortex in the owl monkey--dorsal and lateral areas.

Dense retinotopy data sets were obtained by microelectrode visual receptive field mapping in dorsal and lateral visual cortex of anesthetized owl monkeys. The cortex was then physically flatmounted and stained for myelin or cytochrome oxidase. Retinotopic mapping data were digitized, interpolated to a uniform grid, analyzed using the visual field sign technique-which locally distinguishes mirror image from nonmirror image visual field representations-and correlated with the myelin or cytochrome oxidase patterns. The region between V2 (nonmirror) and MT (nonmirror) contains three areas-DLp (mirror), DLi (nonmirror), and DLa/MTc (mirror). DM (mirror) was thin anteroposteriorly, and its reduced upper field bent somewhat anteriorly away from V2. DI (nonmirror) directly adjoined V2 (nonmirror) and contained only an upper field representation that also adjoined upper field DM (mirror). Retinotopy was used to define area VPP (nonmirror), which adjoins DM anteriorly, area FSTd (mirror), which adjoins MT ventrolaterally, and TP (mirror), which adjoins MT and DLa/MTc dorsoanteriorly. There was additional retinotopic and architectonic evidence for five more subdivisions of dorsal and lateral extrastriate cortex-TA (nonmirror), MSTd (mirror), MSTv (nonmirror), FSTv (nonmirror), and PP (mirror). Our data appear quite similar to data from marmosets, though our field sign-based areal subdivisions are slightly different. The region immediately anterior to the superiorly located central lower visual field V2 varied substantially between individuals, but always contained upper fields immediately touching lower visual field V2. This region appears to vary even more between species. Though we provide a summary diagram, given within- and between-species variation, it should be regarded as a guide to parsing complex retinotopy rather than a literal representation of any individual, or as the only way to agglomerate the complex mosaic of partial upper and lower field, mirror- and nonmirror-image patches into areas.

Species-specific traits predict genetic structure but not genetic diversity of three fragmented Afrotropical forest butterfly species

The Upper Guinean forests of Ghana, West Africa, are considered among the most threatened and fragmented in the world. Little is known about the genetic consequences of fragmentation on Ghana’s forest-associated species, but this genetic signature is generally expected to differ across species. We compared patterns of mtDNA cytochrome oxidase I (COI) variation of three Nymphalid forest butterfly species that differ with respect to their relative dispersibilities (Aterica galene: high habitat fidelity, low dispersal ability; Euphaedra medon: high habitat fidelity, strong dispersal ability; Gnophodes betsimena: relaxed habitat fidelity, low dispersal ability). Individuals were collected from two large forest reserves and five small sacred forest groves. Patterns of differentiation across species were broadly coincident with our predicted hierarchy of relative species dispersibility and suggested that genetic connectivity is most compromised by strict fidelity to forest habitat rather than by raw capacity for sustained flight. Connectivity was uncorrelated with geographic distance, but instead seemed best explained by urbanization and the sequential pattern of forest loss. Genetic diversity was dramatically different among species and not easily explained by either species-specific traits or effects of fragmentation. Aterica galene, the species most impacted by fragmentation, exhibited very high diversity, whereas G. betsimena, a broadly distributed, very common species, with relaxed habitat fidelity, was genetically depauperate. There was limited evidence of genetic erosion from the sacred groves despite these small forest patches accounting for less than 1–10 % of the total area of the forest reserves, which indicates these forest relics have high conservation value.

Cortical and subcortical connections of V1 and V2 in early postnatal macaque monkeys

Connections of primary (V1) and secondary (V2) visual areas were revealed in macaque monkeys ranging in age from 2 to 16 weeks by injecting small amounts of cholera toxin subunit B (CTB). Cortex was flattened and cut parallel to the surface to reveal injection sites, patterns of labeled cells, and patterns of cytochrome oxidase (CO) staining. Projections from the lateral geniculate nucleus and pulvinar to V1 were present at 4 weeks of age, as were pulvinar projections to thin and thick CO stripes in V2. Injections into V1 in 4- and 8-week-old monkeys labeled neurons in V2, V3, middle temporal area (MT), and dorsolateral area (DL)/V4. Within V1 and V2, labeled neurons were densely distributed around the injection sites, but formed patches at distances away from injection sites. Injections into V2 labeled neurons in V1, V3, DL/V4, and MT of monkeys 2-, 4-, and 8-weeks of age. Injections in thin stripes of V2 preferentially labeled neurons in other V2 thin stripes and neurons in the CO blob regions of V1. A likely thick stripe injection in V2 at 4 weeks of age labeled neurons around blobs. Most labeled neurons in V1 were in superficial cortical layers after V2 injections, and in deep layers of other areas. Although these features of adult V1 and V2 connectivity were in place as early as 2 postnatal weeks, labeled cells in V1 and V2 became more restricted to preferred CO compartments after 2 weeks of age.

Conservation genetics of three flightless beetle species in southern California

Regional scale conservation decisions can be aided by information on the distribution of intraspecific diversity, especially the extent to which patterns are common to multiple species. We compare patterns of intraspecific mitochondrial cytochrome oxidase I (COI) variation among three flightless beetles (Coleoptera: Tenebrionidae: Nyctoporis carinata LeConte; Staphylinidae: Sepedophilus castaneus (Horn); Carabidae: Calathus ruficollis Dejean) in the southern part of the California Floristic Province biodiversity hotspot. All species exhibit moderate to high levels of total variation, ranging from 2% to 10% (maximum uncorrected distance). Most populations of all species exhibit unique haplotypes, but few populations’ haplotypes constitute exclusive clades. Many adjacent pairs of populations show indications of some, though limited, genetic connectedness, due either to gene flow or ancestral polymorphism. However, in most cases this diminishes sharply over greater distances. By both statistical and phylogenetic measures, Sierra Nevadan populations are highly distinct from those in the coast and transverse ranges. Among the latter, the eastern transverse ranges are generally most unique and isolated, with diversity in the western parts of these ranges showing fewer barriers. Otherwise, few measures agree on areas of highest conservation value, and overall patterns tend to be species-specific.

Patterns of Mitochondrial Diversity among Desert Firefly Populations (Lampyridae: Microphotus octarthrus Fall)

Abstract The firefly Microphotus octarthrus occurs allopatricallly throughout pinyon-oak and juniper- oak habitats of the deserts of southwestern US. Adult dispersal is limited thus individuals are likely to be genetically isolated by geographic distances. However, during the Pleistocene, habitats may have been contiguous allowing for greater dispersal and genetic continuity. In this study we investigated the patterns of mitochondrial cytochrome oxidase I haplotypes among disjunct populations of M. octarthrus to determine whether current populations were historically contiguous. A total of 26 mtDNA COI haplotypes was found for 28 individuals from six populations spanning the beetle's range. Cladistic analysis of individuals resulted in 15,500 equally parsimonious trees. Strict consensus of these trees was mostly resolved except for a few individuals within well supported clades. Individuals from the same population were monophyletic and genetic isolation by distance was observed. Mean branch lengths for t...

Organization of sensory cortex in the East African hedgehog (Atelerix albiventris).

We investigated the organization of neocortex in the East African hedgehog (Atelerix albiventris) with microelectrode recordings from sensory areas that were later correlated with cytochrome oxidase patterns in sections of flattened cortex. The location of corticospinal projecting neurons was also examined and related to sensory areas by making small injections of wheat germ agglutinin-horseradish peroxidase into the spinal cord. Our goals were to determine how hedgehog cortex is organized, how much sensory areas overlap, and to compare results with recent findings in other insectivores. Evidence was found for three separate topographically organized somatosensory areas, two visual areas, and a caudolateral auditory area. A medial somatosensory area corresponded to S1, the primary somatosensory area, whereas two lateral areas partially encircled auditory cortex and corresponded to the parietal ventral area (PV) and the secondary somatosensory area (S2). Primary visual cortex (V1) was delineated by a caudomedial cytochrome oxidase dark oval, and a more lateral visual area between V1 and somatosensory cortex corresponded to V2, or area 18. Two patches of corticospinal projecting cells were found primarily overlapping S1 and S2. Some bimodal auditory and somatosensory responses were found in parts of PV and S2, but for the most part, areas had relatively sharp histochemically apparent and physiologically defined borders. The present results indicate that the caudal neocortex of hedgehogs has only a few sensory areas, corresponding to those commonly found in several other small-brained mammals. Hedgehog cortical organization differs significantly in somatotopy, number, and position of fields from that of closely related shrews and moles. Thus, clear specializations occur, even within the order Insectivora.

Phenotypic characterisation of respecified visual cortex subsequent to prenatal enucleation in the monkey: development of acetylcholinesterase and cytochrome oxidase patterns.

Prenatal bilateral enucleation induces cortex, which normally would have become striate cortex, to follow a default developmental pathway and to take on the cytoarchitectonic appearance of extrastriate cortex (default extrastriate cortex, Dehay et al. [1996] J. Comp. Neurol. 367:70-89). We have investigated if this manipulation influences the cortical expression of acetylcholinesterase (AChE) and cytochrome oxidase (CO). Early enucleation (before embryonic day 81; E81) had only minor effects on the distribution of AChE and CO in the striate cortex. In animals that underwent operation, the striate cortex CO blobs were significantly more closely spaced on the operculum compared with the calcarine. After early enucleation, there was a periodic distribution of CO dense patches in default extrastriate cortex. These CO patches had a center-to-center spacing that was considerably smaller than that of CO stripes in normal area V2, but was somewhat larger than that of the CO blobs in striate cortex. Although the CO stripes characteristic of normal area V2 could not be detected, there were some high-frequency CO patches, similar to those found in default extrastriate cortex. Early enucleation caused a failure to form the transient AChE bands running perpendicular to the striate border, which are normally present in the fetus and early neonate. Late enucleation did not alter AChE expression in extrastriate cortex. The relatively minor effects of early enucleation in the reduced striate cortex contrast with the changes in expression of these enzymes in extrastriate cortex, which accompany large shifts in the location of the striate border. This suggests a massive reorganisation of cortical phenotype in extrastriate cortex.

Effect of neonatal axoplasmic transport attenuation in the infraorbital nerve on vibrissae-related patterns in the rat's brainstem, thalamus and cortex.

This study evaluated the effects of neonatal attenuation of axoplasmic transport in the infraorbital nerve (ION) on the organization of vibrissae-related patterns in the rat's CNS. Application of colchicine- or vinblastine- impregnated implants to the ION from birth until postnatal day (P)6 to P10 resulted in a 92.4% reduction in the number of trigeminal (V) ganglion cells labelled by application of horseradish peroxidase to the vibrissa pad and a 44.8% decrease in the number of Nissl-stained ganglion cells in the ophthalamic-maxillary portion of the V ganglion. These implants also decreased the number of myelinated fibres in the ION. In normal rats killed on P6-10, there was an average of 10273 +/- 1259 myelinated axons in the nerve. In the animals with colchicine- or vinblastine-treated implants, this value was 3891 +/- 1965. The highest axon count in an experimental animal was 9859. In all animals, axoplasmic transport attenuation resulted in the disappearance of normal vibrissae-related cytochrome oxidase patterns in the brainstem, thalamus and primary somatosensory cortex. Axoplasmic transport attenuation did not result in the disappearance of vibrissae-related ordering of V primary afferent terminal arbors, as demonstrated by anterograde labelling with neurobiotin. These results suggest that some factor conveyed from the periphery of the V ganglion and perhaps on to the brainstem is necessary for the maintenance of vibrissae-related patterns in the thalamus and cortex.

Limits on plasticity in somatosensory cortex of adult rats: hindlimb cortex is not reactivated after dorsal column section.

1. To better understand the limits and extents of plasticity in sensory systems of adult mammals, we unilaterally sectioned the dorsal funiculus at thoracic levels in nine adult rats to deactivate ascending afferents from the hindpaw and lower body. After postsurgical recovery periods of 3 h to 3 mo, the region of primary somatosensory cortex (S1) representing the limbs and trunk was extensively mapped with microelectrodes. 2. Recording sites were later identified as being within the hindlimb representation and other parts of S1 by relating locations of microlesions to the cytochrome oxidase pattern in sections of cortex cut tangential to the pial surface. The extent and effectiveness of spinal cord lesions were evaluated by injecting cholera toxin B subunit conjugated with horseradish peroxidase (B-HRP) at various sites in the deafferented hindpaw. 3. In five animals with complete section of the dorsal funiculus, we failed to detect any response to cutaneous stimulation of any part of the body in the deafferented hindlimb cortex. In four other animals with incomplete lesions, neurons in some penetrations could be activated by hindlimb stimulation, but not by stimulating other body parts. In those cases without activation of hindlimb cortex, B-HRP was detected in the spinal cord only caudal to the lesion, and it was not transported to the nucleus gracilis. Limited transport past the lesion to nucleus gracilis was detected in cases with incomplete lesions. 4. The results indicate that forelimb inputs do not substitute for missing hindlimb inputs in primary somatosensory cortex in rats and that the potential for somatotopic reorganization is more limited than previously thought.

Architectonic subdivisions of the motor thalamus of owl monkeys: Nissl, acetylcholinesterase, and cytochrome oxidase patterns.

As the first part of an investigation of the motor thalamus and its cortical connections in the owl monkey, a New World anthropoid primate, we studied thalamic architecture by using stains for Nissl, acetylcholinesterase (AChE), and cytochrome oxidase (CO), in order to identify subdivisions of the ventrolateral thalamic region as well as other nuclei with motor connections. Material was obtained from brains cut in the frontal, horizontal, and parasagittal planes. Our results indicate that the ventrolateral thalamic region (VL) of owl monkeys is a heterogeneous structure composed of several architectonic subdivisions that resemble divisions that have been described in macaques and other Old World anthropoids. All of these subdivisions are more readily distinguished in AChE than in Nissl or CO preparations. The anterior part of VL, VLa (VLo of Olszewski), is characterized by clusters of medium-sized, darkly stained neurons. VLa is also distinguished by AChE-positive cells embedded in a matrix of neurites as well as by a characteristic dark, irregular net of blood vessels. The posterior part of VL is rather uniform cytoarchitectonically and contains large, darkly stained, and sparsely distributed neurons. However, we were able to distinguish three subdivisions of posterior VL that closely correspond to structures described by Olszewski in macaques: a principal segment, VLp (VPLo of Olszewski), a medial segment, VLx ("area X" of Olszewski), and a dorsal segment, VLd (VLc and VLps of Olszewski). In AChE, VLd is much darker than the other divisions. The distinction between VLp and VLx, which together make up the largest part of VL, is less marked, although VLp is somewhat darker and more irregular in appearance in AChE than is VLx.

Modular organization of human extrastriate visual cortex: evidence from cytochrome oxidase pattern in normal and macular degeneration cases.

The human extrastriate occipital cortex contains several visual areas that are probably analogues of macaque areas V2, V3, VP, V4 and V5. Tracing of callosal connections has led to the anatomical identification of these areas and to the characterization of some of them by cyto- and myeloarchitecture (Clarke and Miklossy, 1990). The pattern of cytochrome oxidase activity in these visual areas is now described in a normal case and in a case of age-related bilateral macular degeneration. In normal cortex, the laminar distribution of cytochrome oxidase activity was similar in V2, V3, VP, V4 and V5; a prominent dark band covered most of layers III and IV, and its upper and lower limits were gradual. In V2, V3, V4 and V5 but not VP, layer II tended to be darker than the infragranular layers. The overall intensity of the staining varied between areas: VP was very light, V2, V3 and V4 were darker, and V5 was very dark. A different, two-band pattern of cytochrome oxidase activity was found in a restricted region of the posterosuperior precuneus. The bilateral age-related macular degeneration had led to a great loss of ganglion cells in the central, but not in the peripheral retinae. The central representation in the lateral geniculate nuclei showed abnormally weak staining for cytochrome oxidase, particularly in the parvocellular layers. In the cortex, the contrast between lightly and darkly stained regions was greater than in the normal case. In particular, V5 was very heavily stained, and in V1 and V2 there were two different types of dark stripes that may represent compartments driven predominantly by the magnocellular system.

Amblyopia induced by anisometropia without shrinkage of ocular dominance columns in human striate cortex.

Amblyopia can be induced by opacity of the ocular media (e.g., cataract), misalignment of the ocular axes (strabismus), or unequal refractive error in the eyes (anisometropia). Experiments in monkeys have shown that early monocular eyelid suture, a model of amblyopia caused by cataract, results in shrinkage of the eye's ocular dominance columns in striate cortex. This reduction of the geniculocortical projection from the deprived eye has been thought to explain in part the mechanism of amblyopia. We labeled the ocular dominance columns in monkeys with amblyopia by using cytochrome oxidase histochemistry. In animals rendered amblyopic by early unilateral eyelid suture, no pattern of cytochrome oxidase activity appeared in layer IVc. Outside layer IVc, alternating rows of light and dark patches were present; the pale patches fit in register with the shrunken ocular dominance columns of the deprived eye, which were labeled by autoradiography. Subsequent removal of one eye caused a striking cytochrome oxidase pattern to emerge in layer IVc that correlated precisely with the shrunken (deprived eye) and expanded (normal eye) ocular dominance columns. This correlation was shown by injecting one eye with [3H]proline. It has remained unsettled whether other forms of amblyopia are accompanied by shrinkage of ocular dominance columns. To address this issue, in an analogous clinical case, we examined the pattern of cytochrome oxidase activity in a human subject with a history of anisometropic amblyopia who suffered a lesion of one optic nerve shortly before death. The ocular dominance columns were normal in width, indicating that some forms of amblyopia occur without shrinkage of ocular dominance columns.

Functional organization of area V2 in the alert macaque.

We studied the relation between anatomical structure and functional properties of cells in area V2 of the macaque. Visual function was assessed in the alert animal during fixation of gaze. Recording sites were reconstructed with respect to cortical lamination and the cytochrome oxidase pattern. We measured orientation and direction selectivity, end-stopping, sensitivity to binocular disparity and ocular dominance, and determined more complex functions like sensitivity to anomalous contours and lines defined by coherent motion. Orientation selectivity was found in all parts of area V2, with high frequencies in the pale and thick stripes of the cytochrome oxidase pattern, and with lower frequency in the thin stripes. Representations of anomalous contours were found in the pale and thick stripes with similar frequencies, but generally not in the thin stripes, which have been thought to process colour. Lines defined by coherent motion were most frequently represented in the thick stripes; they were less frequent in the pale stripes, and (as with anomalous contours) were not found in the thin stripes. Sensitivity to binocular disparity was found in all types of stripes, but more frequently in the thick stripes, where the exclusively binocular neurons were also concentrated. By contrast, no segregation was found for direction selectivity and end-stopping. All neuronal properties were distributed evenly across cortical laminae. We conclude that mechanisms for figure-ground segregation involve the pale and the thick stripes of the cytochrome oxidase pattern, perhaps with greater emphasis on 'shape from motion' and 'stereoscopic depth' in the thick stripes, while more elementary neuronal properties are distributed almost evenly across the stripe pattern.

Visual resolution and sensitivity of single cells in the primary visual cortex (V1) of a nocturnal primate (bush baby): correlations with cortical layers and cytochrome oxidase patterns

1. This study describes the response properties of V1 cortical cells in a nocturnal primate and examines the receptive field organization of these cells in relationship to anatomically defined layers and cytochrome oxidase (CO) rich blobs and CO poor interblob compartments. Visual resolution and contrast sensitivity are consistent with other physiological and behavioral measures in this species. Comparisons are made with response properties of the same zones in macaque monkey, as well as of area 17 of a distantly related species (cat) that also occupies a nocturnal niche. 2. The responses of single cells to drifting sinusoidal gratings were recorded in V1 (striate cortex) of anesthetized, paralyzed bush babies (Galago crassicaudatus). Cells tended to be grouped with respect to ocular dominance, orientation preference, and direction selectivity. There was a high proportion of monocularly driven cells as in macaque monkey. Only 6% of the cells were nonoriented. These were poorly tuned complex cells and bore no resemblance to nonoriented lateral geniculate nucleus (LGN)-like cells reported in layer IV of macaque monkeys. Unidirectional cells were most frequently encountered in cortical layers that receive input from the magnocellular layers of the LGN. 3. Cells were classified as simple (31%) or complex (69%) according to standard criteria. Simple cells were significantly more narrowly tuned than complex cells for both orientation and spatial frequency. Complex cells had significantly higher average optimal spatial frequencies and spatial frequency cutoffs than simple cells. Contrast sensitivity of simple and complex cells averaged 38 and 34, respectively. Spatial resolution and sensitivity of these cells matches behavioral measures in bush baby. The spatial and temporal resolution of bush baby cells are similar to those of cats, which is likely related to the nocturnal niche of both species. 4. Cells in supragranular (I-III) and infragranular (V, VI) layers differed significantly in their response characteristics. The cells in the supragranular layers had significantly higher contrast sensitivity than did the cells in the infragranular layers. Cells in the supragranular layers likewise had higher temporal frequency cutoffs, significantly lower optimal spatial frequencies, lower spatial frequency cutoffs, and tighter orientation tuning than did cells in the infragranular layers. 5. Properties of cells in individual layers and CO blob and interblob compartments also showed differentiation. Layer III had the narrowest orientation and spatial frequency tuning with the tightest tuning in layer IIIC (IVB).(ABSTRACT TRUNCATED AT 400 WORDS)

Differential effects of peripheral damage on vibrissa-related patterns in trigeminal nucleus principalis, subnucleus interpolaris, and subnucleus caudalis

Histochemistry for cytochrome oxidase reveals a vibrissa-related pattern in trigeminal nucleus principalis, subnucleus interpolaris, and the magnocellular portion of subnucleus caudalis. This pattern is apparent in late fetal animals and is disrupted by transection of the infraorbital nerve on the day of birth. We recently reported results suggesting that the cytochrome oxidase pattern reflects primary afferent-induced clustering of second order neurons in all of these nuclei. If this conclusion is correct, it should follow that primary afferent lesions made after the cytochrome oxidase pattern became established in the brainstem might have little effect upon it. Accordingly, we transected the infraorbital nerve (the trigeminal branch that supplies the vibrissae) on postnatal days 0–10 and evaluated the vibrissa-related pattern in the brainstem with cytochrome oxidase histochemistry at varying intervals after these lesions. If the infraorbital nerve was sectioned on postnatal days 0–2, the vibrissa-related pattern was absent in trigeminal nucleus principalis, and both subnucleus interpolaris and caudalis. If such lesions were made after postnatal day 9, there was no appreciable effect upon the cytochrome oxidase pattern in any portion of the trigeminal brainstem complex. However, if lesions were made between postnatal days 3 and 8, the density and clarity of the cytochrome oxidase staining pattern were reduced in interpolaris and caudalis, but not in principalis. This difference was not due to differential transganglionic degeneration in these nuclei. Tracing with horseradish peroxidase demonstrated qualitatively equivalent primary afferent losses in principalis, interpolaris, and caudalis. Immunocytochemistry with a monoclonal antibody directed against parvalbumin also demonstrated a vibrissa-related pattern of cell bodies in principalis and interpolaris in rats killed on postnatal day 9 or later ages. The combination of retrograde tracing and immunocytochemistry revealed that the parvalbuminimmunoreactive neurons in principalis projected to thalamus while those in interpolaris were not labelled by tracer injections into the thalamus, midbrain, cerebellum or spinal cord. Infraorbital nerve transections made as late as postnatal day 8 resulted in a sharp decrease in the staining of parvalbumin-positive neurons in interpolaris, but not in principalis. Lesions made on postnatal day 10 had no qualitative effect upon parvalbumin-positive neurons in any portion of the trigeminal brainstem complex. The results of this study support the conclusion that the vibrissa-related cytochrome oxidase pattern in principalis becomes independent of primary afferent input at a very short interval after its initial appearance. In contrast, the patterns in more caudal portions of the trigeminal brainstem complex require maintenance of primary afferent input for a much longer postnatal period. The present results also provide further support for the conclusion that postsynaptic elements in the trigeminal brainstem complex may underlie the primary afferent-induced cytochrome oxidase pattern.

Effects of cortical and thalamic lesions upon primary afferent terminations, distributions of projection neurons, and the cytochrome oxidase pattern in the trigeminal brainstem complex

Early postnatal lesions of the primary somatosensory cortex alter the vibrissa-related cytochrome oxidase (CO) pattern in nucleus principalis (PrV) of the rat's trigeminal (V) brainstem complex (Erzurumlu and Ebner, '88: Dev. Brain Res. 44:302-308). At present, the reason for this change is not clear. It may be that the corticotrigeminal projection is necessary for the maintenance of vibrissa-related patterns in PrV. However, it is also possible that the loss of the normal pattern of CO activity reflects a change in the organization of brainstem cells resulting from transneuronal retrograde degeneration. In order to address this question, we made lesions of either the primary somatosensory cortex (S-I) or ventrobasal thalamus (VB) in newborn rats and directly assayed distribution of V primary afferents by transganglionic transport of horseradish peroxidase and V-thalamic neurons by retrograde transport of either fluorogold or true blue. Neonatal cortical and thalamic lesions produced no qualitative change in the distribution of primary afferent terminals in either PrV or V subnucleus interpolaris (SpI) beyond that which could be attributed to shrinkage of the brainstem resulting from retrograde degeneration. Most importantly, the "patchy" pattern of terminations observed in normal rats remained apparent in the brain-damaged animals. The normal distribution of V-thalamic neurons in PrV was disrupted by both cortical and thalamic lesions. These cells are normally patterned in a way that matches the distribution of primary afferent terminals and thus that of the mystacial vibrissae. This was not the case in the neonatally brain-damaged rats. Taken together, these results are consistent with the conclusion that neonatal cortical and thalamic lesions disrupt the normal CO pattern in PrV primarily because of their effects upon the patterning of brainstem cells. The present findings demonstrate further that clustering of primary afferents does not require a normal complement of postsynaptic neurons.

Chemically distinct compartments of the thalamic VPM nucleus in monkeys relay principal and spinal trigeminal pathways to different layers of the somatosensory cortex

The ventral posteromedial nucleus (VPM) of the monkey thalamus was investigated with combined immunocytochemical, histochemical, and connection-tracing techniques. Injections of anterogradely transported tracers were placed selectively in the caudal nucleus of the spinal trigeminal nuclear complex, and retrogradely transported horseradish peroxidase (HRP) or fluorescent dyes were placed on the surface or into the depths of defined parts of the trigeminal representation in the first somatic sensory area (SI) of the cerebral cortex. The results are correlated with those of the preceding paper (Rausell and Jones, 1991), which demonstrated the presence of 2 domains in the nucleus on the basis of different patterns of cytochrome oxidase (CO) staining and calcium-binding protein immunoreactivity. The cells of the CO-defined rod and matrix domains receive inputs from different components of the trigeminal afferent system and project to different layers of SI. The large- and medium-sized relay cells of the CO-rich rods, which are immunoreactive for parvalbumin, all project to middle layers of SI. The small relay cells of the weakly-stained CO-matrix, surrounding and intervening between the rods, are immunoreactive for 28-kDa calbindin and project to superficial layers (I and II) of SI. Anterograde tracing studies reveal that the rod domain in VPM is innervated by fibers arising in the contra- and ipsilateral principal trigeminal nucleus, while the matrix domain (and calbindin-positive domains in adjacent nuclei) are innervated by fibers arising in the caudal nucleus of the spinal trigeminal complex. These results demonstrate the modularity and parallel streaming of the functional components of the trigeminal part of the somatic sensory system and suggest that lemniscal and nonlemniscal elements of the system gain access by separate routes to different layers of the SI cortex.

Parvalbumin in rat superior colliculus

Parvalbumin-like immunoreactivity (PA-LI) has been studied in sections of the superior colliculus (SC) of the rat and its distribution compared to the patterns of acetylcholinesterase (AChE) and cytochrome oxidase (CO) staining. In the intermediate layers it was found that PA-LI is spatially associated with AChE only in the medial part of the SC, but assumes a complementary distribution further laterally. There was a positive correlation between PA-LI and CO. We conclude that the patterns of PA-LI and CO are not systematically related to collicular input known to be associated with the AChE-rich zones, but may reflect adherence to channel separation beyond the terminal fields of clustered afferents.