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T A Woolsey

Publications and source records attributed to T A Woolsey.

At least 73 records · Page 4Linked to original sources
PubMed1978

Acute whisker removal reduces neuronal activity in barrels of mouse SmL cortex.

The autoradiographic 2-deoxy-D glucose (2-DG) method has been used to map relative changes in metabolic activity in the CNS during various functional states (Plum et al., '76). Here we describe the application of the 2-DG method to assay regional activity in the posteromedial barrel subfield (PMBSF) region of the mouse SmI cortex after acute removal of mystacial vibrissae. One day prior to isotope injection, various combinations of vibrissae (e.g., all vibrissae, row-C only, rows-B and -D only) were plucked from adult male Swiss Webster mice under anesthetic. The next day, 5 muCi of 14C-2-DG were injected into a tail vein, and the mice were allowed to actively explore an empty cage for 45 minutes. The animals were then sacrificed, the brains quickly removed, frozen, and sectioned either parallel or perpendicular to the pia at 80 mum in a cryostat. The sections were mounted, dried on coverslips, and were used to expose X-ray film, after which the sections were stained with thionin and the X-ray film developed. The tissue sections and matching autoradiograms were compared directly from photomicrographs of each. The autoradiograms showed areas of higher activity in barrels for which corresponding vibrissae were present and lower activity in barrels for which appropriate vibrissae were missing. In tangential sections from animals with all vibrissae intact, the PMBSF was uniformly and consistently higher in activity than in cases with all vibrissae missing. The removal of row-C or rows-B and -D resulted in strips of decreased activity in the corresponding PMBSF rows. The same patterns of increased or decreased activity were also seen in sections normal to the pia, but the changes in activity, while greatest in layer IV, extended through all layers of the cortex. Finally, in a number of the autoradiograms, density patterns could be recognized which later were shown to relate directly to sides of individual barrels. The results indicate: (1) Acute removal of the peripheral vibrissal hairs is sufficient to deprive the related contralateral cortical barrel neurons of normal activity. Thus in the mouse somatosensory system it may be possible to determine the relative importance of sensory deprivation and neonatal peripheral lesions in normal cortical development. (2) The barrels are part of a functional cortical columnar organization similar to that in other sensory systems. And, (3) the 14C-2-DG-X-ray technique is sufficiently sensitive to reveal parts of individual barrels in autoradiograms and thus, with some modification, may be suitable for the study of small populations of neurons.

Animals↗
PubMed1977

A simple stain for myelin in frozen sections: a modification of Mahon's method.

A simple and rapid method for demonstrating myelinated nerve fibers in frozen sections of the central and peripheral nervous system is described. Material fixed by perfusion with mixed aldehydes gives the best results but the method also works on specimens fixed by immersion in formaldehyde. Frozen sections varying in thickness from 15-50 micron are mounted on slides subbed with chrome alum-gelatin. After hydration (60-120 min), sections are mordanted (20-40 min) in 2.5% iron alum and rinsed briefly in three changes of distilled H2O (total 2 min). Staining is for 60-180 min in 20 cc freshly made 10% alcoholic hematoxylin diluted with 165 cc distilled H2O to which 15 cc saturated Li2CO3 is added. The sections are washed in distilled H2O (5-15 min) and dehydrated in graded alcohols without differentiation in mordant, and covered. Myelin stains a dark blue-purple against a light grey background. Fiber tracts, as well as individual myelinated fibers, are clearly demonstrated.

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PubMed1976

Areal changes in mouse cortical barrels following vibrissal damage at different postnatal ages.

The normal cytoarchitectonic pattern of barrels in layer IV of mouse SmI face cortex is altered by early damage to the mystacial vibrissae (Van der Loos and Woolsey, '73). In the present study, the middle row of vibrissae (row-C) on one side of the face in groups of Swiss mice was cauterized on the day of birth (postnatal day [PND] -1)or on PND's - 2, 3, 4, 5, 7, 10, 12, 15, 20 and 30; littermates in each group served as controls. All animals were perfused on PND-60 and the brains sectioned parallel to SmI layer IV. For each specimen, the posteromedial barrel subfields (PMBSF) of the two hemispheres were reconstructed with a camera lucida and the cross-sectional areas of individual barrels measured using a small computer. The findings are: (1) The hemispheres ipsilateral to the vibrissal damage are quantitatively indistinguishable from the littermate controls indicating that the ipsilateral hemispheres in lesioned animals can serve as controls for observations of the type reported in this paper. (2) There are no consistent differences in the cross-sectional areas of the PMBSF's as a whole in the hemispheres ipsi- and contralateral to the peripheral damage, suggesting that there is no net loss of cortex as a result of the lesions. (3) The contralateral row-C barrels are reduced in size. Expressed as a percentage of normal values; row-C is reduced to 17% for animals lesioned on PND-1, 16% on PND-2, 38% on PND-3, 52% on PND-4 and 79% on PND-5; on PND-7 and later the cross-sectional areas of row-C barrels are normal. This implies that the barrel field of the SmI face cortex becomes progressively refractory to the effects of peripheral damage during the first postnatal week and in the period prior to PND-6, an intact periphery is necessary for normal cortical development. (4) In every case, the decreased cross-sectional area of row-C is accompanied by precisely increased cross-sectional areas of the barrels in adjacent rows-B and D. in the case of the restricted peripheral damage which we produced, there is a "compensation" in the contralateral hemisphere, which can be correlated with patterns of the specific thalamocortical projections.

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PubMed1975

Comparative anatomical studies of the SmL face cortex with special reference to the occurrence of "barrels" in layer IV.

In the SmL cortex of mice and rats there are cytoarchitestonically identificable groups of cells -- called barrels -- some of which have been shown to be directly related to whiskers and other sensory hairs on the contralateral face. In this study we have used a comparative approach to determine the incidence and variation of the barrels. The brains of 27 mammalian species have been examined histologically to determine whether barrels exist in layer IV of what is known or likely to be the face area of SmI. Thick sections (50-100 mum) were taken tangential to the pia overlying SmI and stained with thionin. The patterns of facial whiskers were also mapped by dissection of the facial skin. Barrels were seen only in brains of species belonging to three of the seven mammalian orders examined. We have confirmed Weller's ('72) observation of barrels in the Australian brush-tailed possum but have not found barrels in two marsupials from the western hemisphere. Barrels were demonstrable in representatives of four of five rodent suborders examined and in the rabbit. From the study of the rodent brains, a number of trends emerge. (1) The organization of the barrel fields is "dictated" by the organization of the sensory periphery. Animals with five rows of large mystacial (moustache-like) vibrissae have five rows of PMBSF (Posteromedial barrel sub-field) barrels. (2) The barrels are confined to layer IV of (what is known or likely to be) the SmI face area. The pattern and cortical location of the barrel field is consistent among different specimens of the same species. (3) Certain behavioral patterns do not preclude the existence of the barrels. Species which possess well developed visual systems and behaviors (e.g., grey squirrel) and forms which do not actively explore the environment by whisking their vibrissae (e.g., guinea pig) have barrels. (4) Within a given rodent suborder, the barrels become more difficult to identify, as the brains become larger. We have not yet been able to demonstrate barrels in the largest rodent, the capybara.

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PubMed1975

The number, size and spatial distribution of neurons in lamina IV of the mouse SmI neocortex.

We located the corresponding barrel in Layer IV of the mouse SmI cortex in eleven cerebral hemispheres sectioned in a plane tangential to the pia overlying SmI and in one sectioned and prepared by a combined Golgi-Nissl method. In the section in which barrel C-1 could be optimally visualized each neuronal soma was outlined with a camera lucida and the cross-sectional area measured with the aid of a small computer. In all, nearly 7,000 neurons were measured. We estimate that on average barrel C-1 contains about 2,000 neurons. The mean cross-sectional area of the perikarya is 62.51 mu2 (S.D. plus or minus 14.51 mu2) and the size distribution of the neurons is unimodal and positively skewed. There is no segregation of cells within the barrel on the basis of size. The spatial distribution of cells in the barrel is fairly constant, from specimen to specimen, and the charactieristic cytoarchitectonic appearance of the barrel can be related to regional neuronal packing density since there are at least 1.6 as many neurons in the sides of the barrel as the hollow. The constancy of the cellular composition of the barrels indicates that the mechanisms responsible for the development of the mouse SmI cortex are fairly rigidly determined, and that the barrel field should lend itself well to further quantitative, developmental and physiological analysis.

Animals↗
PubMed1975

On the "selectivity" of the Golgi-Cox method.

The randomness of the impregnation of layer IV cortical neurons by the Golgi-Cox method (Van der Loos, '56) has been assessed directly in Barrel C-1 of the mouse SmI. All Golgi-Cox impregnated neurons and unimpregnated neurons which were revealed with a Nissl counterstain were counted and measured in ten cerebral hemispheres cut tangential to the pia overlying the barrel field. The percentage of Golgi stained neurons varied considerably in different preparations from 0.73% to 2.26% with an average of 1.29%. The size distributions of both the Golgi impregnated and Nissl stained cells are similar but the difference of the means is statistically significant. However, if the means are equated there is no statistical difference in the two populations. When the Golgi precipitate is removed and the cells re-measured following Nissl staining there is a systematic reduction of the perikaryal cross-sectional area which is compatible with the differences in the means observed for the two populations as a whole. Finally, the frequency with which Golgi impregnated neurons are found in the barrel sides and hollows parallels the frequency with which Nissl stained neurons are observed in these two locations. We conclude that this variant of the Golgi method impregnates barrel neurons randomly. The value of this information for quantitative studies of cerebral cortex is discussed as is the potential of the system for elucidating some of the mechanisms responsible for Golgi impregnation.

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PubMed1975

Mouse SmI cortex: qualitative and quantitative classification of golgi-impregnated barrel neurons.

The neurons in layer IV of the mouse somatosensory cortex are arranged in a remarkably consistent pattern of multicellular cytoarchitectonic units called "barrels." Each barrel is known to be related, in a one to one manner, to a contralateral whisker or vibrissa on the animal's face. In this study we have examined Golgi-impregnated neurons that comprise the "barrels." Several criteria, some being quantitative measures of dendritic arbors and somal sizes which were obtained with a computer-microscope system, suggest that all barrel neurons can be placed in two classes, the members of which are present in approximately equal numbers. The cells in the two classes can be further subdivided on the basis of the relationship of their processes to the barrels: 85% of them have processes restricted to a single barrel; 15% of them distribute their processes to two or more barrels. From these observations it is possible to suggest that a majority of neurons comprising the barrels would respond initially to movements of only one whisker while the remainder would respond to movements of two or more whiskers. In addition it has been shown that the quantitation of neuronal structure can provide a numerical basis for the classification of neurons in the central nervous system.

Animals↗
PubMed1973

Somatosensory cortex: structural alterations following early injury to sense organs.

In mouse somatosensory cortex there are discrete cytoarchitectonic units, called "barrels." Each barrel is related to one sensory vibrissa on the muzzle. Individual vibrissae were carefully injured at birth; 12 to 43 days later, the corresponding barrels proved to be absent. Evidently the sensory periphery has an important influence on the structure of the somatosensory cortex.

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