Modification of cortical orientation selectivity in the cat by restricted visual experience: a reexamination.

Recent reports have stated that the orientation selectivity of cells in the cat's visual cortex can be biased by limiting the early visual environment to stripes of one orientation. Data obtained from seven kittens using systematic and quantitative sampling of preferred orientation, together with a blind procedure, do not show a bias toward the orientation presented in one type of restricted rearing environment.

Visual claustrum: topography and receptive field properties in the cat.

A region containing visually responsive cells was found in the dorsocaudal claustrum. This area contains a single orderly map of the contralateral visual field. Like cortical cells, most claustral cells are selective for stimulus orientation. They are binocular, and they respond to either direction of movement and to a broad range of velocities. Their most striking property is a marked preference for very long stimuli.

Coincidence of patchy inputs from the lateral geniculate complex and area 17 to the cat's Clare-Bishop area.

Pathways from a variety of structures to the largest of the cat's suprasylvian visual areas, the Clare-Bishop area, were found to patchy. These inputs arose from the lateral geniculate complex, from area 18, from area 19, and, as noted by Montero (Brain Behav. Evol. 18:194-218, '81), from area 17. The Clare-Bishop area was previously delineated on the basis of its uniform pattern of connections with cortex and thalamus (Sherk: J. Comp. Neurol. 247:1-31, '86) and found to incorporate pieces of several retinotopically defined areas (Tusa, Palmer, Rosenquist: Cortical Sensory Organization. Vol 2. Multiple Visual Areas. Clifton, NJ: Humana Press, pp. 1-31, '81). However, since individual patches did not correspond to particular retinotopically defined areas, other explanations of afferent patchiness were sought. An obvious question is whether the patches originating from different sources are systematically related to each other. Two hypotheses were considered. First, different inputs--for example, from the lateral geniculate nucleus (LGN) and from area 17--might terminate in intermingled but mutually exclusive zones in the Clare-Bishop area. Second, multiple patches of input might reflect duplicate representations of the corresponding visual field segment in the Clare-Bishop area. Both hypotheses were tested by injecting the lateral geniculate complex and either area 17 or area 19 with different anterograde tracers. In each case the two injections involved regions of the visual field that coincided to some degree, ranging from near-total overlap to almost complete exclusion. The first hypothesis predicted that the different labels in the Clare-Bishop area would never be found to overlap, while the second hypothesis predicted that when injections were closely matched retinotopically, there would be extensive overlap between patches. The results supported the second hypothesis: the better the retinotopic match between injections, the greater the overlap found between labeled geniculate and cortical input in the Clare-Bishop area. However, the multiplicity of patches seen in some experiments, and the close spacing between some patches, suggested that an additional, nonretinotopic mechanism also contributes to patchiness in the projections to the Clare-Bishop area.

Location and connections of visual cortical areas in the cat's suprasylvian sulcus.

The initial aim of the experiments described here was to identify and quantify the cortical and thalamic connections of visual cortical areas located in the vicinity of the suprasylvian sulcus. Inputs to various sites in this region were studied by making small injections of wheat germ agglutinin (conjugated to horseradish peroxidase) at physiologically identified locations. Retrogradely labeled cells were counted in each identifiable area of cortex and in thalamic nuclei. Some injections yielded quantitatively similar distributions of labeled cells, and it is suggested that such evidence provides a useful way of dividing the cortex into areas. By this criterion, a single, relatively large, cortical area was identified that occupied most of the medial bank of the suprasylvian sulcus, all or most of its posterior bank, and a small segment of its lateral bank. It was referred to as the Clare-Bishop area. Because neighboring visual areas were found to lack input from area 17, while the Clare-Bishop area received a strong striate input, its boundaries were investigated by labeling afferents from area 17. Together with the results of retrograde tracer injections, these data suggested that the Clare-Bishop area cuts across several of the visual areas defined physiologically by Tusa et al. ('81). As a consequence, its retinotopic organization must be relatively complex, with duplications of some parts of the visual field. Three other visual areas were tentatively identified on the basis of their distinctive connections. One was situated on the lateral bank of the suprasylvian sulcus and appeared to border the Clare-Bishop area laterally. Another, referred to as area 21, lay adjacent to area 19, and, for part of its length, also appeared to bound the Clare-Bishop area. The third, corresponding approximately to Heath and Jones's ('71) posterior suprasylvian region, lay lateral and anterior to the Clare-Bishop area in the depths of the posterior suprasylvian sulcus.

Neural analysis of visual information during locomotion.

For most vertebrate species, vision is critical during locomotion. In this review, we survey what is known about neural mechanisms that might be involved in this visual analysis. Problems that such mechanisms are likely to solve include: (1) determination of heading (the discrepancy between an observer's direction of motion and direction of gaze); (2) detection of course changes; (3) setting of courses using goals and landmarks; (4) obstacle avoidance; (5) accurate foot placement. To understand how the visual system handles these tasks, we must first consider what neurons 'see' during locomotion: this is determined both by an observer's motion and by his gaze. We then review response properties of neurons in the cortical 'motion pathways' of the monkey and cat as they relate to problems encountered during locomotion. The most studied areas are the medial superior temporal area in the monkey, which has been linked to heading determination, and the lateral suprasylvian area in the cat, where many cells are sensitive to motion in depth, and some are selective for optic flow patterns generated during locomotion. A few subcortical populations have also been linked to visual analysis during locomotion. Most notable are cells in the pigeon's nucleus rotundus: these respond selectively to looming stimuli, some firing at a specific time before the stimulus collides with the bird. Another intriguing population is in the cat's visual pontine nucleus, where cells respond to large displays suggestive of optic flow during locomotion.

Flattening the cerebral cortex by computer.

A computer program was developed for unfolding the cerebral cortex so that it could be viewed as a 2-dimensional surface. Input to the program consisted of tissue sections cut in a standard plane of section. Each section was represented by one line, which corresponded to a contour line in the flattened map. From these data, the computer constructed a 3-dimensional surface representation, which it then flattened. Because the cerebral cortex has considerable intrinsic curvature, flattening required that some regions be expanded and others shrunken. These changes occurred as a natural consequence of local decisions made by the computer as it laid down successive contours. The user could intervene during both surfacing and flattening in order to shape the developing map. The program has been used to generate 37 flattened maps from various regions of cat cortex, and 1 from monkey cortex. The local topography of cortical features such as gyri, sulci, architectonic boundaries, and patches of transported tracer, appeared to be conserved fairly faithfully. Areal distortion was also modest, with an average change in surface area of only 12%.

Retrograde transport of [3H]proline: a widespread phenomenon in the central nervous system.

[3H]Proline was injected into spinal cord, pons, inferior colliculus, superior colliculus, lateral geniculate nucleus, pulvinar-LP complex and visual cortex of cats or rats. After 1-3 days' survival the animals were perfused with formalin or mixed aldehydes. Autoradiography showed labeling of cell bodies in most regions known to project to the injection sites. The ability to take up and retrogradely transport [3H]proline appears to be a common property of central neurons. We infer that the transport of this compound is unrelated to its possible status as a neurotransmitter.

Prolonged survival of axons terminating within lesions of cat visual cortex.

It is well known that brain lesions made by the injection of ibotenic acid destroy neuronal cell bodies but do not kill passing axons. We have found that axons terminating within such lesions in visual cortex also survive for at least 2 months, despite the absence of available synaptic sites. We made tracer injections in area 17, and observed dense patches of anterograde label within lesions in other visual cortical areas. Furthermore, because the retinotopic site of the tracer injection was known, we could conclude that the retinotopic site was encompassed within the lesion.

Fractures of the odontoid process in young children.

We reviewed eleven patients less than seven years old with fractures of the odontoid process in an effort to establish a more standard form of treatment for the injury and to determine what complications, if any, occur as a result of fractures of the odontoid process in pediatric patients. Our study showed that children with odontoid fractures that are recognized and treated promptly usually do well. The fracture can usually be reduced by passive manipulation or by the "hanging head technique". Support in the reduced position for two to three months in a Minerva jacket or halo cast should be long enough to permit healing. Our study suggests that fractures of the odontoid process in young patients almost always heal.

Cystic lymphangioma in the adult: an unusual axillary mass.

Magnetic resonance imaging (MRI) has rapidly become an effective technique for the diagnosis and localization of most musculoskeletal diseases. Because MRI lacks ionizing radiation and has superior soft tissue contrast as compared with computed tomography without the need for intravenous contrast material, MRI is emerging as the study of choice for soft tissue masses. This report describes the use of MRI in the evaluation of an unusual axillary soft tissue mass in an adult, a cystic lymphangioma.

Anterior approaches to the cervical spine.

Excellent exposure of the cervical spine from C4 to T1 can be attained with the standard anterior approach which utilizes a longitudinal or transverse incision to gain access to the anterior border of the sternocleidomastoid which, along with the trachea, esophagus, and carotid sheath, is retracted. Blunt dissection anterior to the sheath exposes the prevertebral fascia and the anterior aspect of the spine from C4 to T1. Occasionally surgery in the lower cervical spine necessitates detachment of the sternal head of the sternocleidomastoid. Anterolateral approaches to the upper cervical spine and base of the skull often require partial release of the sternocleidomastoid from the mastoid process and retraction of the carotid sheath and hypoglossal and spinal accessory nerves. If these retropharyngeal approaches do not provide sufficient access to the base of the skull and C1 and C2, a transoral approach, possibly with mandible and tongue splitting, can be useful. Infection is a consideration in transoral surgery, however, and this approach is indicated only in special circumstances.

The vertical stability of the cervical spine.

The concept of the three-column cervical spine and load transmission through each column was experimentally tested. Material consisted of five cervical columns removed from cadavers. The experiment was conducted on an Instron load testing machine. Load was applied on superior articular surfaces of the axis vertebra and was recorded below from each column separately at the level of the sixth cervical vertebra. It was found that 36% of the total load applied on the top of the specimen is transmitted through the anterior column formed by bodies and intervertebral discs and 32% each through the two posterior cervical columns formed by the articular processes. The experiment very strongly supported the role of neural arch in transmission of vertebral compressive forces.

Biomechanical evaluation of the extensor musculature of the cervical spine.

Dissection of the musculature in the cervical spines of four cadavers indicated that the semispinalis cervicis and capitis muscles appeared to be the muscles primarily responsible for extension of the cervical spine and head. The minimum force needed to balance a biomechanical model of the cervical spine in the neutral prone position against gravity measured 14.38 kg. The values obtained with this model, with roentgenograms of the cervical spine, and vector analysis were close enough to establish that the model is apparently valid for studying the extensor musculature of the cervical spine. Because the extensors appear to generate considerable force and may act as significant dynamic stabilizers of the cervical spine, the authors have altered their posterior surgical approach to minimize disruption of the extensor musculature.

Vertebra plana and eosinophilic granuloma of the cervical spine in children.

Eosinophilic granuloma of the cervical spine in children is a rare lesion which presents both diagnostic and therapeutic problems. The report describes three additional cases. Open biopsy is recommended instead of attempted needle aspiration in children. Laminectomy is likely to result in spinal deformity, and is not advised unless a second stage fusion is planned. Radiotherapy is effective in controlling the lesion. The ultimate outcome is usually good.

Facial malformations and spinal anomalies. A predictable relationship.

Facial malformations have generally been associated with spinal anomalies, but this report reviews patients with specific facial abnormalities and attempts to document accompanying spinal anomalies. The results indicate that the most common types of facial malformations vary predictably in their influence on spinal or other musculoskeletal abnormalities. Apert and Goldenhaar syndromes are associated with significant spinal anomalies.

Hydrocephalus, cervical cord lesions, and spinal deformity.

Twenty-six children (4-16 years) had hydrocephalus and spinal deformity; 22 children had scoliosis over 50 degrees, and five children had kyphosis over 100 degrees. Twenty-one children had metrizamide enhanced cord CT scans, and 12 had additional head scans. Two children died, and one was autopsied. Three children had intracranial pressures monitored during spinal surgery. All children had Type I and II Arnold-Chiari malformations, 58% had cord cavitation (syringo/hydromyelia), 67% had cord tethering. The anatomic study showed extensive fibrosis and scarring of the upper cord and brain stem, but intraoperative studies showed that there is free transmission of fluid pressure wave from the cord across the foramen magnum with a consequent rise in intracranial pressure. This study documents frequent coexistence of spinal deformity and central nervous system lesions (hydrocephalus, Arnold-Chiari malformation, cord tethering with atresia, and cord cavitation). It supports the theory that the Arnold-Chiari malformation is a primary developmental deformity and that cord cavitation noted in these patients is primarily syringomyelia formed on the basis of ischemic necrosis within the cord. The free transmission of a fluid pressure wave from the cord to the lateral ventricle supports the Williams theory of propagation of syringomyelic cavities once they have developed. It is conjectural but likely that the CNS lesions cause spinal deformity by disrupting coordinating control of spinal musculature by the normal postural reflex mechanisms. Hydrocephalic patients who develop spinal deformity require thorough investigation for CNS lesions with head scans, CT scans, and metrizamide enhanced CT scans. NMR technology, however, may supplant techniques currently employed.

Injuries in the sport of luge. Epidemiology and analysis.

We undertook this study to determine the types and frequency of injuries sustained in the sport of luge. Before this study, no data were available in the medical literature on luge injuries. We performed a retrospective analysis between the years 1985 and 1992 using data obtained from the athlete injury and illness report forms at the US Training Center Sports Medicine Clinic in Lake Placid, New York. During the 7 years examined, 1043 athletes took 57,244 track runs and sustained 407 injuries. The risk of sustaining an injury was 0.39 per person per year, and the risk of an injury causing the loss of more than 1 day of practice was 0.04 per person per year. Contusions were the major injury (51%), followed by strains (27%). Strains of the neck muscles and contusions of extremities, especially the hands, were characteristic injuries sustained by athletes. The most serious injuries were concussions (2%) and fractures (3%). Crashes were responsible for 64% of injuries. Luge appears to be a relatively safe sport with injury rates comparable with recreational alpine skiing.

Fractures of the proximal humeral epiphysis.

Displacements of the proximal humeral epiphysis at the epiphyseal plate result from extension injuries. The configuration of the epiphyseal plate and the thickness of the periosteum surrounding the epiphysis make slight to moderate displacements relatively stable injuries, which can be treated successfully with external support. In patients with more severe displacement, flexion, abduction, and slight external rotation of the distal fragment bring the metaphysis into alignment with the proximal fragment, correcting the anterior angulation. The thick periosteal sleeve attached to the physis through which the metaphysis tears out anteriorly has great potential for remodeling the persistant bowing that remains after healing of the fracture. Although shortening and residual angulation results from closed treatment are almost always good and open surgery is rarely indicated.

Fractures and dislocations of the cervical spine in children.

Correct diagnosis of fractures and dislocations of the cervical spine in children requires an awareness of the pseudosubluxation and other normal variants noted in x-ray films of patients in this age group. Fractures of the odontoid process occur frequently and almost always can be treated by closed reduction and external fixation until union occurs. Fractures of the lower cervical spine are difficult to detect roentgenographically, and x-ray changes can belie the severity of soft tissue injury and cord trauma. Instability tends to persist in adolescent patients after cervical spine injury because of the combination of epiphyseal and posterior ligamentous disruption. Neoplastic, inflammatory, and congenital lesions render the cervical spine vulnerable to injury and can permit major damage to result from minor stress.

Accurate compartment pressure measurement using the Intervenous Alarm Control (IVAC) Pump. Report of a technique.

This study demonstrates the accuracy of a common, readily available pressure transducer system (IVAC pump) for the measurement of compartment syndromes. An in vitro assay was used to compare the accuracy of the IVAC pump manometer with the Hewlett-Packard monometer (HP78532B) and a miniaturized digital fluid pressure manometer (Stryker). The IVAC pump was accurate within 2.4 mm Hg difference of the HP78532B and Stryker manometers. Twenty-five patients suspected of having compartment syndrome posttibial fracture had compartment pressures measured using the IVAC pump. In all the patients, compartment syndrome was accurately assessed (positive in one case and negative in the remainder). The IVAC pump is readily available in most hospitals. It is easy to use and provides accurate measurements of compartment pressures.