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Biomedical subjects

J I Johnson

Publications and source records attributed to J I Johnson.

At least 37 records · Page 2Linked to original sources
PubMed1983

Mechanosensory projections to cuneate, gracile, and external cuneate nuclei in a tree squirrel (fox squirrel, Sciurus niger).

The distribution and organization of mechanosensory projections to the cuneate, gracile and external cuneate nuclei were mapped in tree squirrels anesthetized with ketamine and urethane. Tungsten microelectrodes were used to record unit and unit cluster responses to mechanical stimulation. Most responses in the gracile nucleus were to stimulation of skin and hairs of the tail, hind foot and leg, and trunk, in that order going from dorsal to ventral in the nucleus. A similar distribution of responses was found in the cuneate nucleus to stimulation of forelimb, neck and pinna going from dorsomedial to ventrolateral in the nucleus. Some responses to stimulation or movement of subcutaneous tissue were found in the cuneate and gracile nuclei. Responses in the external cuneate were to stimulation of deep-lying tissues in the hand medially, the lower arm centrally and the shoulder and trunk laterally. The pattern of projections in the tree squirrel differed most strikingly from that seen in raccoons and opossums in the relatively small extent of projections from the glabrous skin of the forepaws which were concentrated in a small region near the obex in squirrels. In contrast, there was a large representation of hairy receptive fields located on the forelimb in all regions of the squirrel cuneate nucleus. Otherwise, the somatotopic organization of mechanosensory projections to these dorsal column nuclei in tree squirrels was similar to that reported in other mammals.

Afferent Pathways↗
PubMed1983

Contralateral as well as ipsilateral projections to raccoon cerebellum from external cuneate nuclei and cell groups f and x.

To assess the locations and densities of cells in the dorsal medulla giving rise to ipsilateral versus contralateral projections to the mechanosensory regions of cerebellar cortex in the anterior lobe and paramedian lobule, these cortical regions were injected unilaterally with horseradish peroxidase in each of 5 raccoons. To show injection sites and retrogradely labelled cells in the medulla, sections through the medulla and the cerebellum, in at least two different planes for each, were reacted with tetramethylbenzidine; alternate sections were reacted with cobalt-enhanced diaminobenzidine. Labelled were 60-80% of cells in the ipsilateral and 15-25% of cells in the contralateral external cuneate nuclei, as well as 25-50% of cells in the ipsilateral and the contralateral cell groups f and x near the descending vestibular nucleus. Substantial contralateral, as well as ipsilateral cerebellar projections from external cuneate nuclei and cell group x may be related to development of forelimb dexterity in raccoons, since these nuclei mediate forelimb muscular sensibility. The numerical complementarity of ipsilaterally versus contralaterally projecting cells suggests that they represent two separate populations.

Animals↗
PubMed1983

Phylogeny through brain traits: trees generated by neural characters.

Phylogenetic trees were computed by the Wagner algorithm from data on up to 15 brain characters scored on 154 specimens of 134 mammalian species. Because the data were not complete on all specimens, only one tree, of 18 taxa, was generated on all 15 features; a tree of 99 species was computed from 10 characters, and trees of 38 species from 10 and 12. The 38-taxon trees were considered best because they preserved most completely the integrity of mammalian orders. All trees consistently separated the subclasses of mammals and suggested that rodents, insectivores, and the tree shrew were most derived on the basis of brain characters. The trees' shapes are sensitive to small alterations in character scorings, largely because of the relatively few characters available and small differences in the number of states among them.

Animals↗
PubMed1983

Phylogeny through brain traits: the mammalian family tree.

Wagner trees based on the analysis of 15 brain characters scored on 154 specimens of 134 mammalian species show consistent patterns of relationship among the taxa, i.e. (1) monotremes are the primitive complement of the group uniting marsupials and placentals; (2) among marsupials, diprotodont Australian forms are more derived; (3) placental mammals divide into two groups of orders, roughly the ferungulates (carnivores, ungulates, and subungulates) and the unguiculates-plus-gliroids (chiropterans, dermopterans, lagomorphs, rodents, primates, and insectivores including elephant shrews); (4) edentates sit at the base of or just before the placental dichotomy; (5) the tree shrew and tarsier show the same pattern of distribution of brain traits as some rodents, as do prosimians and New World monkeys.

Animals↗
PubMed1983

The projection of cervical primary fibers to the DCN of the squirrel, Sciurus niger: fiber sorting in the dorsal columns.

The course and terminal distribution of cervical primary afferents in the dorsal column nuclei were studied in the fox squirrel, Sciurus niger. Unilateral rhizotomies were performed at cervical levels C3, C4, C5, C6 and C8. For all spinal levels studied except C8, degeneration in the medullary cuneate fasciculus was present within two distinct groups. They included a large oblique lateral lamina and a small superficial group of degeneration. The superficial group was horizontal, located medial to the large lamina and appeared to be formed by the medial shifting of fibers away from the initial larger group. Fibers in the large primary lamina appeared to terminate primarily in the ventrolateral areas of the cuneate nucleus. Fibers from the superficial group, however, appeared to project mostly to dorsal cuneate nuclear areas. Hence, the dual transverse terminal patterns for cervical fibers in the cuneate nucleus appeared to be related directly to a fiber sorting process that involved the formation of two often separate ascending fiber groups in the cuneate fasciculus. The results of this study are compared with the mechanosensory mapping of the dorsal column nuclei in the squirrel.

Animals↗
PubMed1982

The anterior border zones of primary somatic sensory (S1) neocortex and their relation to cerebral convolutions, shown by micromapping of peripheral projections to the region of the fourth forepaw digit representation in raccoons.

In raccoons the somatic sensory neocortex is greatly expanded, with separate gyral crowns devoted to and intervening sulci separating, sensory representations of separate body parts, most strikingly those of the volar surfaces of individual forepaw digits. Most of the cortex in this region is buried in widely ramifying sulcal walls, wherein sensory projections have not been studied. We have determined mechanosensory projections to the fourth digit representation region including all neighboring sulcal walls, using tungsten microelectrodes for 3-dimensional micromapping. We found no significant alteration in the location and pattern of projections when the following different anesthetics were used: dial-urethane, chloralose, or methoxyflurane with nitrous oxide. The precisely organized somatotopic representation of the distal volar surface of the fourth digit, on the causal aspect of its gyral crown, continues down the anterior bank of the triradiate sulcus. This meets, at the fundus, projections from the proximal volar surface of the digit which occupy the posterior sulcus wall; they in turn meet projections from the volar palm at the gyral crown. In the anterior part of the crown containing the representation of the distal volar digit, across the crown. In the anterior part of the crown containing the representation of the distal volar digit, across the crown of the gyral bridge intervening between the medial and lateral segments of the central sulcus, throughout the posterior walls of the central sulci, and in the walls of the interbrachial sulcus, we found a distinctive border-zone of projections from heterogeneous receptive fields. Within a roughly somatotopic basic pattern of organization we found intermingled projections from single and multiple claws and dorsal hairy surfaces of digits and proximal hand, along with additional projections from volar surfaces. These projections can be construed as forming something of a distorted mirror-image of the representation of the volar hand. Beyond this was a second zone of distinctive projections from afferents of the forelimb muscles, in the anterior walls of the central sulci. These projections are interrupted where the sulci are interrupted. The zone of muscle afferent projections corresponds to those seen between sensory and motor regions in other species; its strict association with sulcal folding here and in other species suggests a general relationship of these projections to central sulci. The zone of heterogeneous projections resembles similar zones seen at other levels of this system in raccoons, in the cortex of other species, and it may relate to some of the multiple representation reported in other species. It also may be related to the formation of sulci in this region and may be a specialized zone for cortico-cortical connections.

Animals↗
PubMed1982

Phylogeny through brain traits: fifteen characters which adumbrate mammalian genealogy.

Fifteen characters of brain organization are identified for which primitive and derived states can be distinguished, and which are thus useful in reconstructing mammalian phylogeny. The states of the characters are numerically coded in sequence from most primitive to most derived, to facilitate reciprocal comparisons in comprehensive genealogical analyses. The characters include certain features of cerebral circulation, cytoarchitecture, fiber pathways, and sensory projections. Seven characters are shared with nonmammals, a fact which makes then particularly useful for establishing their primitive vs. derived states; the other eight characters are features peculiar to mammals. Ten characters provide impressive reinforcement for traditional major grouping of the species, while five provide bases for new ideas about mammalian relationships.

Animals↗
PubMed1982

Phylogeny through brain traits: the distribution of categorizing characters in contemporary mammals.

The varying states of 15 characters of the central neural organization are tabulated as they occur in each of 147 mammalian species. For each character and species, scores are entered designating the primitive or derived state of the character as it is observed in that species. This tabulation provides data in numerically ordered form for multiple analyses of possible phylogenetic relationships which take into account variations in several different characters simultaneously.

Animals↗
PubMed1980

Somatic sensory cortical regions of the agouti, Dasyprocta aguti.

The localization and organization of primary (SmI) and secondary (SmI) somatic sensory cortical regions in agoutis, have been studied with micro- and macroelectrode-evoked potential techniques. For SmI, the mean surface area determined using microelectrodes was 13% smaller than that obtained using macroelectrodes. The location and organization of SmI are similar to those of other rodents: the largest representations were those of the vibrissae, the perioral regions and the first digit of the hand. As in some other animals, SmII is related to both sides of the body. It shows excellent somatopic differentiation and was located lateral and posterior to SmI, in relation to which it is arranged as a reduced mirror image. The area of SmII represents 31% of that of SmI in agoutis. The large size of the forepaw representation in SmI is reflected in SmII, that of the face representation is not; this agrees with similar findings from several other species. SmI was completely mapped using light touch stimuli, and contains many projections from vibrissae and hairs along with some proprioceptive projections. SmI overlaps with visual projections. SmII receives less light touch, vibrissae and hair projections than SmI, and it receives numerous deep mechanical and auditory projections. In SmII latencies were 10.96 msec for somesthetic and 13.39 msec for auditory stimuli; in SmI latencies were 13.25 msec for somesthetic and 39.80 msec for visual stimuli. One sulcus separates the SmI projections of the forelimb from those of the hindlimb, and another is often found marking the posterolateral boundary of SmII.

Animals↗
PubMed1980

Phylogeny through brain traits. Relation of lateral olfactory tract fibers to the accessory olfactory formation as a palimpsest of mammalian descent.

In mammals the fibers of the dorsal lateral olfactory tract either pass under the accessory olfactory formation, or they penetrate through it separating the internal granule cells from the output cells. The use of this trait as a phylogenetic indicator in 181 specimens representing 131 species of 16 orders yielded evidence for common ancestry of Insectivora, Chiroptera, Dermoptera, Rodentia, and Primates (including Tupaia), since all share the derived trait, their dorsal lateral olfactory tract fibers passing through the accessory olfactory formation. Carnivora (including Pinnipedia), Hyracoidea, Perissodactyla, and most Artiodactyla share the primitive condition (fibers passing under) with the one order of monotremes and three marsupial orders. The Edentata and Lagomorpha may be separate from the two major placental groups and from each other, or they may represent successive stages in the evolution of the derived state through progressive alterations in the relative chronology of development of olfactory system components, or one or both orders may occupy an ancestral position with respect to the dichotomy within placental mammals.

Animals↗
PubMed1980

Influence of intonation on auditory sequential memory skills.

This study was designed to investigate the effect of intonation on the auditory sequential memory spans of children normal in language development and those with delay. Analysis indicated that intonation as a cue did not facilitate recall of monosyllabic nouns presented in sequences of two, three, four, and five words. Children with a language delay of six months or longer had spans of one word less than children with no language delay. Neither recall nor the memory span was related to chronological age over the range of 42 and 72 mo. for either group of children.

Child, Preschool↗
PubMed1978

Evaluation of a clinical method for measuring comfortable loudness for speech.

The reliability of a clinical method for measuring most comfortable loudness for speech was evaluated on 100 subjects with sensorineural hearing loss. The method uses spondaic words as the test stimuli. The test-retest reliability was determined for an ascending and descending approach mode for all 100 subjects as well as for subgroups categorized on the basis of severity of hearing loss and pure-tone configuration. Results indicated that reliability was not affected by approach mode, hearing loss severity, or pure-tone configuration. Test-retest differences were not significant and test-retest correlations were high (r = 0.73 to 0.93) across all subgroup categories. Clinical reliability was demonstrated by the high percentages (85 to 92%) of subjects who had test-retest differences no greater +/-5 dB. The procedure is rapid, uses no special equipment, is easily performed, and is reliable. Thus, it is recommended as the preferred clinical procedure.

Adult↗
PubMed1977

Absence of mitral cells in monolayer in monotremes. Variations in vertebrate olfactory bulbs.

An invariant feature of the olfactory bulb in placental and marsupial mammals is the arrangement of the perikarya of mitral cells in a monolayer. Contrasting with this is the arrangement found in the olfactory bulbs of the monotremes, platypus and echidna, where the large perikarya are not only absent from the position of a monolayer (usually forming the external boundary of the internal plexiform layer) but occupy a region which would characterize them as tufted cells. In other classes of amniote vertebrates, reptiles and birds, the placement of large perikarya in the olfactory bulb ranges from a compact layer to a broad band. Such an overview among several vertebrate classes suggests that a monolayer of mitral cells may be a specialized subset of the tufted-mitral cell population. The accessory olfactory formation among mammals also exhibits variation in the compactness of the large perikarya: a broadband in most but a compact layer in a few others such as the chinchilla and the capybara. Such specialized alignment of perikarya (and, consequently, of their dendritic and axonal elements) may enable more refined signal processing than does random alignment of these elements. Such speculations can be tested using appropriate phylogenetic sampling, and monotremes provide particularly advantageous test cases.

Anatomy, Comparative↗
PubMed1975

Species differences in mechanosensory projections from the mouth to the ventrobasal thalamus.

To determine whether the largely ipsilateral, inverted representation of mouth parts in the ventrobasal thalamus of sheep was unique to that species or an expansion of a general mammalian pattern, the corresponding thalamic projections were mapped electrophysiologically in a selected series of mammals (oppossums, agoutis, squirrel monkeys, cats, raccoons, and sheep) representing major branches of evolution among therian mammals. In mapping, tungsten microelectrodes were used to record multi-unit discharges in the thalamus in response to mechanical stimulation of oral surfaces. The pattern of projections seen in sheep is not a general mammalian pattern; there is extensive variability among mammals in the laterality and internal orgainzation of the projections from the mouth. In spite of the great variability, the results suggest an hypothesis concerning phylogenetic trends: descendants of palaeoryctoid insectivores (cats, raccoons, and sheep in our sample) have extensive ipsilateral projections from the mouth, in other therian mammals (opossums, agoutis, and squirrel monkeys in our sample) the ipsilateral component is small or absent.

Animals↗