Quantitative analyses of intracellularly characterized and labeled thalamocortical projection neurons in the ventrobasal complex of primates

This study describes the architecture of neurons and individual dendritic arbors of thirteen intracellularly labeled thalamocortical projection neurons that respond to non-noxious stimuli from the primate (Macaca fascicularis or Macaca mulatta) ventrobasal complex (VB). The neurons compose a homogeneous morphological class with total dendritic lengths from 10,169 μm to 21,711 μm (mean 17,615 μm ± 3,705). The labeled neurons were remarkably similar in most measured parameters including the number of dendrites (7.5 ± 1.2), percentage of dichotomous branching (89.8% ± 3.4), and contribution of terminal branches to total dendritic length (88.4% ± 2.0). The individual dendrites ranged in total length from 443 μm to 7,657 μm with a mean of 2,346 μm (±137, n = 98). There was a positive correlation between stem dendrite diameter and total dendrite length, making it possible to estimate the total size of an individual dendrite by measuring the stem dendrite diameter. There was only a small increase in mean path distance with increasing dendritic size at the whole neuron and individual dendritic levels, so that for individual dendrites the mean path distance of a dendrite consisting of only two segments was 199 μ, while the mean path distance for a dendrite with eight segments was only 45 μm longer. Analysis of dendrite diameter, segment order, and path distance shows that dendritic diameter is not reliable for determining the location of synaptic contacts viewed by electron microscopy onto dendritic trees. The small variation of measured parameters between these neurons presents a powerful tool for future developmental, plasticity and comparative studies of VB neurons. © 1993 Wiley-Liss, Inc.     

Alterations in the postnatal development of the cerebellar cortex due to zinc deficiency. III. Impaired dendritic differentiation of basket and stellate cells

The effects of zinc deficiency and undernutrition on the dendritic differentiation of basket and stellate cells were studied in 21-day-old rats. A morphometric analysis of the dendritic branching of basket and stellate neurons was used that took into account the cell's position in the molecular layer. Zinc deficiency and undernutrition during the suckling period impaired the dendritic differentiation of cerebellar basket and stellate cells. The effects of zinc deficiency were not due totally to the reduced food intake of lactating dams. In the lower 65-75% of the molecular layer of zinc-deficient (ZD) pups, the dendritic field area, the total dendritic length and the number of branches per interneuron were reduced by 45-61%. In the lower 50-60% of the molecular layer, undernutrition reduced the dendritic field area, the total dendritic length and the number of branches per neuron by 32-44%. A comparison of ZD and undernourished (pair-fed) pups indicated that the dendritic field area and total dendritic length of neurons of ZD animals were 43% and 30% smaller in the lower half of the molecular layer. The number of branches per neuron was not significantly different between ZD and undernourished animals. The area of the soma was unaffected by dietary treatment. A delay in the onset of dendritic differentiation and a retarded rate of dendritic growth were considered possible mechanisms for the impaired dendritic differentiation.     

Analysis of morphological features of thalamocortical neurons from the ventroposterolateral nucleus of the cat

Morphological features of the dendritic arborization can affect neuronal responses and thus the input‐output function of a particular neuron. In this study, morphological data of eight fully reconstructed thalamocortical (TC) neurons from the ventroposterolateral (VPL) nucleus of adult cats have been analyzed. We examined several geometrical and topological parameters, which have been previously shown to have a high impact on the neuron firing pattern and propagation of signals in the dendritic tree. In addition to well‐known morphological parameters such as number of dendritic trees (8.3 ± 1.5) and number of branching points (80–120), we investigated the distribution of dendritic membrane area, branching points, geometrical ratio, asymmetry index, and mean path length for all subtrees of the TC neurons. We demonstrate that due to extensive branching in proximal and middle dendritic sections, the maximum value of the dendritic area distribution is reached at 120–160 μm from the soma. Our analysis reveals that TC neurons are highly branched cells and their dendritic branching pattern does not follow Rall's 3/2 power rule; average values at proximal vs. distal dendritic sections were different. We also found that the dendritic branching pattern of each subtree of the cell had a wide range in symmetry index, whereas the mean path length did not show a large variation through the dendritic arborizations. J. Comp. Neurol. 518:3541–3556, 2010. © 2010 Wiley‐Liss, Inc.     

The Extent of the Dendritic Tree and the Number of Synapses in the Frog Motoneuron

Frog motoneurons were intracellularly labelled with cobaltic lysine in the brachial and the lumbar segments of the spinal cord, and the material was processed for light microscopy in serial sections. With the aid of the neuron reconstruction system NEUTRACE, the dendritic tree of neurons was reconstructed and the length and surface area of dendrites measured. The surface of somata was determined with the prolate - oblate average ellipsoid calculation. Corrections were made for shrinkage and for optical distortion. The mean surface area of somata was 6710 microm2; lumbar motoneurons were slightly larger than brachial motoneurons. The mean length of the combined dendritic tree of brachial neurons was 29 408 microm and that of lumbar neurons 46 806 microm. The mean surface area was 127 335 microm2 in brachial neurons, and 168 063 microm2 in lumbar neurons. The soma - dendrite surface area ratio was 3 - 5% in most cases. Dendrites with a diameter of 600 microm from the soma. This suggests that about two-thirds of the synapses impinged upon distant dendrites >600 microm from the soma. The efficacy of synapses at these large distances is investigated on model neurons in the accompanying paper (Wolf et al., Eur. J. Neurosci., 4 1013 - 1021, 1992).     

Changes in the length and organization of nucleus laminaris dendrites after unilateral otocyst ablation in chick embryos

To evaluate the contributions of the ear and acoustic stimulation to the structural development of central auditory neurons, the right otocyst was surgically destroyed in chick embryos on the third day of incubation. This pro-cedure prevents the formation of the inner ear and acousticovestibular nerve and thus removes the dominant afferent synaptic input to nucleus magnocellularis (NM). Subsequently, nucleus laminaris (NL), which receives afferent synaptic input to its dorsal dendrites from the ipsilateral NM and afferents to its ventral dendrites from the contralateral NM, was studied on both sides of the brain in Golgi preparations. By embryonic day 17, the total lengths of the individual NL dendritic fields connected to the right NM (i.e., the manipulated dendrites) were decreased by an average of 44% as compared to those NL dendrites connected to the left NM (i.e., the unmanipulated dendrites). The mean length of the unman-ipulated dendrites in experimental animals, however, did not differ from average dendritic length in normal control embryos. The amount of dendritic length lost by a NL neuron was strongly correlated with the length of the unmanipulated dendrites on the opposite side of the same neuron and with that neuron's position within NL. The lengths of dorsal and ventral dendrites on individual neurons were at least as highly correlated in experimental as in normal control animals. Correlation of dendrite length with the position of measured neurons within NL indicated that the large rostromedial-to-caudolateral gradient of increasing den-drite length present in the normal NL is also found in the manipulated dendrites in experimental animals. Regression and correlation analyses relating the length of dendrites to their longitudinal cross-sectional area revealed that there was no difference in mean dendritic diameter between the manipulated and unmani-pulated dendrites in experimental animals. The findings of a high dorsal-ventral length correlation in experimental animals and a normal spatial gradient of dendritic length among the manipulated dendrites suggests two explanations. Either (1) acoustically evoked synaptic activity is not essential for the develop-ment of these two aspects of dendritic organization, or (2) the normal NM afferents to the unmanipulated dendrites of each NL neuron in an animal with one ablated otocyst can, under the influence of acoustically driven activity, control develop-ment of the manipulated dendrites. These alternate hypotheses can be tested experimentally.     

Postnatal dendritic development in the rabbit visual cortex

Golgi preparations of rabbit visual cortex aged 1-25 days, as well as similar tissues from adults, were examined for the growth of the dendritic arbor, and in particular the development of dendritic spines. The layer 5 pyramidal neurons and layer 4 stellate neuron were chosen as representatives of larger classes of neurons in the visual cortex. It was determined that the growth of the dendritic arbor, determined by counts of total number of dendritic and total dendritic length, is quite similar for pyramidal and stellate neurons. Dendritic spine development, however, is more rapid in pyramidal neurons than in stellate. This disparity in the rate of dendritic spine development is discussed in the light of physiologic studies on the development of receptive field properties in the rabbit visual cortex.     

Analysis of dendritic spines in rat CA1 pyramidal cells intracellularly filled with a fluorescent dye

The dendritic branching pattern and the distribution of dendritic spines were studied in hippocampal neurones with an improved technique. In slices taken from adult Wistar rats, CA1 pyramidal cells were filled with Lucifer yellow and examined under a laser-scanning confocal microscope. The basal dendrites were found evenly distributed inside a regular cupola-shaped volume. Their total length was about 4,500 μm. The branches divided between one and three times, with the initial segments comprising less than 2%, and the long terminal segments (mean length, 119 μm) including more than 80% of the total length of the basal dendrites. The apical dendritic branches emerged obliquely from the main shaft, ran for a distance of 50 to 250 μm, and made up a total length of about 5,100 μm in stratum radiatum and between 1,100 and 3,200 μm in stratum lacunosum-moleculare. The mean total length of the dendritic tree was 11,900 μm. All values were corrected for shrinkage. Shrinkage was measured in three dimensions and was 20.2% in the horizontal (x/y) plane and 40.9% in the vertical (z) plane. Both the basal and the apical dendritic branches were covered by regularly spaced spines. When corrected for dehydration-induced shrinkage and for hidden spines, the density was 1.80 and 2.00 spines/μm dendritic length for the basal and apical dendritic branches, respectively. Apart from the initial parts of the branches, which had few or no spines, the spines were remarkably evenly spaced. In particular, the distance between spine heads was significantly different from a random distribution, suggesting a regulatory process for the spacing of spines. © 1995 Wiley-Liss, Inc.     

Morphology of lumbar motoneurons innervating hindlimb muscles in the turtle Pseudemys scripta elegans: an intracellular horseradish peroxidase study

Motoneurons in the turtle lumbar spinal cord, electrophysiologically identified as innervating a muscle belonging to a functional group, were injected with horseradish peroxidase by electrophoresis. A total of 45 motoneurons were reconstructed from transverse sections. Eleven motoneurons were identified as innervating knee extensor muscles, eight as innervating hip retractor and knee flexor muscles, 14 as supplying ankle and/or toe extensors, and 12 as innervating ankle and/or toe flexor muscles. The cell bodies were elongated and spindle-shaped in the transverse plane. The mean equivalent soma diameter was calculated to be 33.4 micrometers. The mean axon conduction velocity was 15.7 m/second. Significant, though rather weak, positive correlations were found between soma diameter, axon diameter, and axon conduction velocity. The axons of the reconstructed motoneurons did not reveal a recurrent axon collateral. However, a few unidentified motoneurons did possess such collaterals. The dendritic trees were restricted to the ipsilateral side of the cord, but reached out in lateral, ventral, and ventromedial directions to the subpial surface. Easily recognizable and characteristic dendrites were found both in the dorsal dendritic tree and in the dorsomedial dendritic tree. Correlations were calculated between the soma diameter and (1) the number of first-order dendrites, (2) the mean diameter of the first-order dendrites, and (3) the combined diameter of the first-order dendrites. In each case no correlations or only weak correlations were found. Fair correlations were observed between the diameter of a first-order dendrite and the number of terminal dendritic branches (r = .61) and the combined dendritic length (r = .78). However, correlations between the combined diameter of all first-order dendrites per neuron and the total number of terminal dendritic branches and the total combined dendritic length of a neuron were extremely weak. The overall appearance of turtle spinal motoneurons is comparable to that observed in other "lower" vertebrates such as frog and lizard. However, similarities are also observed between certain morphometric parameters in turtle and cat lumbar motoneurons.     

The dendritic tree of spinal neurons

The size of the dendritic tree was determined from the number, length and diameter of primary dendrites and number and length of their branches in 360 unselected neurons from all areas of the spinal gray of L₇ segment in Golgi-Kopsch preparations (dog). A direct proportionality was demonstrated between the size of the dendritic tree of a neuron and the number of its primary dendrites; a basic dependence of the entire dendritic complex upon the number of initial dendrite extensions from cell body. The existence of two dendrite parameter levels, and consequently two size levels of the whole dendritic tree, was also established; one for the large neurons and one for the small ones. The parameter and tree size differences between the two classes of neurons, the latter distinguished by different cell body-size ranges, were all statistically highly significant. Very little of the variability of the parameters or of the whole tree could be accounted for by the variability of the specific cell body-size within each of the two groups of neurons or within the entire sample. The morphological distinction is between two classes of neurons. The mean dendrite surface area for the entire population sample of large neurons was some five times greater than the mean for the small ones. With commensurate cell body-size differences, and thus total receptive surface area, this implies a 5-fold difference in mean number of synaptic contacts/neuron. The evidence, in addition, strongly pointed to motoneurons as having larger dendritic trees, on the average, than interneurons with comparably-sized cell bodies. It was previously estimated that only 2% of interneurons in L₇ segment, which outnumber motoneurons 30:1, are large cells.     

Postnatal development of cat hind limb motoneurons. I: Changes in length, branching structure, and spatial distribution of dendrites of cat triceps surae motoneurons

The postnatal development of length, branching structure, and spatial distribution of dendrites of triceps surae motoneurons, intracellularly stained with horseradish peroxidase, was studied from birth up to 44-46 days of postnatal (d.p.n.) age in kittens and compared with corresponding data from adult cats. The number of dendrites of a triceps surae motoneuron was about 12, and the arborization of each dendrite generated an average of 12-15 terminal branches. There was no net change in the number of dendrites of a neuron or in the degree of branching of the dendrites despite the occurrence of both a transient remodeling of the dendritic branching structure and changes of the spatial distribution of the dendritic branches during postnatal development. The perisomatic territory in the transverse plane occupied by the dendritic branches of a motoneuron increased in parallel with the overall growth of the spinal cord. Thus, the relative size of the dendritic territory in this plane was kept almost constant, whereas dendritic branches projecting in the rostrocaudal direction grew much faster than the spinal cord and also became more numerous. At birth the rostro-caudal dendritic span of individual motoneurons bridged 1:6 to 1:5 of the L7 spinal cord segment length; this figure was 1:3 at 22-24 d.p.n. Hence, in this direction, the growing dendritic branches invaded novel dendritic territories. The change in dendritic branch length from birth to 6 weeks of age corresponded to an average growth rate of 2 to 4 microns per dendritic branch and day, which implies that the total increase in length of the dendrites of a neuron could amount to 1 mm/day. The increase in branch length did not occur in a uniform or random manner; instead, it followed a spatiotemporal pattern with three phases: From birth to 22-24 d.p.n., growth was particularly prominent in greater than or equal to 3rd order preterminal and 2nd through 6th order terminal branches. From 22-24 to 44-46 d.p.n., a large increase in branch length confined to terminal branches of greater than or equal to 3rd branch orders was observed. As indicated by topological analysis, this length increase was probably due in part to a resorption of peripheral dendritic branches during this stage of development. From 44-46 d.p.n. to maturity, the increase of dendritic branch length was restricted to preterminal branches of low (less than or equal to 4th) branch order.(ABSTRACT TRUNCATED AT 400 WORDS)     

Convergence of excitatory and inhibitory inputs onto CCK-containing basket cells in the CA1 area of the rat hippocampus

The number and distribution of excitatory and inhibitory inputs affect the integrative properties of neurons. These parameters have been studied recently for several hippocampal neuron populations. Besides parvalbumin- (PV) containing cells that include basket and axo-axonic cells, cholecystokinin (CCK)-containing interneurons also form a basket cell population with several properties distinct from PV cells. Here, at the light microscopic level, we reconstructed the entire dendritic tree of CCK-immunoreactive (IR) basket cells to describe their geometry, the total length and laminar distribution of their dendrites. This was followed by an electron microscopic analysis of serial ultrathin sections immunostained against gamma-aminobutyric acid, to estimate the density of excitatory and inhibitory synapses on their somata, axon initial segments and different subclasses of dendrites. The dendritic tree of CCK-IR basket cells has an average length of 6300 microm and penetrates all layers. At the electron microscopic level, CCK basket cells receive dendritic inputs with a density of 80-230 per 100 microm. The ratio of inhibitory inputs is relatively high (35%) and increases towards the soma (83%). The total numbers of excitatory and inhibitory synapses converging onto CCK-IR cells are approximately 8200. Comparison of the two, neurochemically distinct basket cells reveals that CCK-containing basket cells receive much less synaptic input than PV cells; however, the relative weight of inhibition is higher on CCK cells. Additional differences in their anatomical and physiological properties predict that CCK basket cells are under a more diverse, elaborate control than PV basket cells, and thus the function of the two populations must be different.     

Motor neuron disease with slow eye movements and vertical gaze palsy

Two middle-aged patients with motor neuron disease showed common eye movement disorders and intellectual impairment in the later stage of the illness. Eye movement disorders were characterized by slow saccades and vertical glaze palsy, which seemed to be supranuclear ophthalmoplegia. Neuropathological examination of one patient revealed degeneration of the substantia nigra without pathological changes in the ocular motor nuclei, in addition to findings compatible with motor neuron disease. These cases appear to raise a possibility of a distinct group of multiple system degenerations.     

Postnatal development of dendrites of relay neurons in the lateral geniculate nucleus of the marmoset (Callithrix jacchus): a quantitative Golgi study

Dendrites of multipolar relay neurons in the lateral geniculate nucleus of the marmoset (Callithrix jacchus), at various ages from birth to adulthood, were studied in rapid Golgi preparations. The dendrites were analyzed by means of three-dimensional computer reconstructions and decomposed into intermediate and terminal segments, both of which were further classified according to their centrifugal order. Measurements were made of the number of segments per dendrite, the total length of dendrites, and the mean length of intermediate and terminal segments. In adult marmosets, there are four stem dendrites on average per neuron, and each dendrite divides into a mean of 14 segments. Between birth and 6 weeks of age, the mean dendritic length doubles, mainly because of changes in terminal segments. There is a significant decrease in dendritic length into adulthood. The total number of stem dendrites does not change after birth, but during the first postnatal week dendrites lose distal segments, after which there is a significant increase in the number of segments of orders 3 to 7. The mean length of intermediate segments does not change with age, nor with order, whereas the length of terminal segments increases from 50 to 120 microns from birth to 6 weeks of age, and then decreases to the adult value of 80 microns. In conclusion, during the period of most rapid visual development, important morphological changes occur in geniculate relay-cell dendrites, involving essentially terminal segments. These observations correlate well with changes of geniculate volume and neuronal density.     

OP-1 enhances dendritic growth from cerebral cortical neurons in vitro

Osteogenic protein-1 (OP-1), a member of the transforming growth factor-beta (TGF-beta) superfamily, has been demonstrated to stimulate dendrite growth from sympathetic neurons in culture. However, it is not known whether OP-1 affects dendrite growth from central nervous system neurons. Therefore we quantified axon and primary, secondary, and total dendritic growth from embryonic mouse cortical neurons (E 18) grown in vitro in a chemically defined medium. Morphology and double immunolabeling (MAP2, NF-H) were used to identify cortical dendrites and axons after 3 days in vitro. Cell morphology, neuron survival, and axon length were similar under all experimental conditions. The number of primary dendrites also was similar; however, the length of primary dendrites and the length and number of secondary dendrites were significantly increased by the addition of OP-1 to the culture medium. This increase in dendrite growth was dose-dependent; maximal dendritic growth was observed after the addition of 30-100 ng/ml of OP-1 to the culture medium. Specific support of dendrite growth was not observed when neurons were exposed to other members of the TGF-beta superfamily. These findings demonstrate that OP-1 selectively increases dendrite growth from cerebral cortical neurons in vitro.     

Contribution to the quantitative study of the nervous tissue. A new method for measurement of the volume and surface area of neurons

In our histological analysis of the brain stem of the kitten with the Golgi-Cox method, it was found that the application of reflecting illumination provides a clear outline of the soma surface including its relationship with the dendrites. Utilizing this method of illumination it was possible to develop a new approach for following the total course of dendrites in successive serial sections and a method for the photogrammetrical representation of neuron soma by means of microscopic stereophotograms. This has provided a means for estimating precisely the dimensions of the neuron. Five cells of the magnocellular nucleus of bulbar and pontine reticular formation have been measured as test cases by means of this new method. The following results were obtained: the mean area and volume of the neuron soma obtained by means of photogrammetry are 13,580μ² and 109,820μ³ respectively; the area and volume of the entire dendritic portion of the neuron are 66,640 μ² and 70,060 μ³ respectively. In the case of serial sections 250 μ thick, about 25% of the dendrites are lost in the neighboring sections with respect to length, and 16% to 14% with respect to area and volume. Thus the ratios of the dendritic area to the soma area and that of the dendritic volume to the soma volume average 5.1 and 0.6 respectively.     

The Purkinje cell dendritic tree: a computer-aided study of its development in the cat and in culture

Golgi-prepared cerebella from 1, 10, 13 and 30-day-old kittens were analyzed and compared with 30-45 days in vitro (DIV) HRP-stained organotypic cultures of newborn kitten cerebella. Computer reconstructions and morphometric parameters allowed a quantitative analysis of the Purkinje cell (P-cell) dendritic trees. In intact animals the dendritic organization appeared monoplanar as early as one day after birth and biplanar in 85% of the cells at day 13; however, by day 30, 90% of the cells were monoplanar. During the first 4 postnatal weeks, the dendritic expansion was due mostly to an increase in the total number of segments and the total dendritic length, whereas the overall mean segment length remained almost unchanged. In culture, the 30-45 DIV P-cell dendritic trees always appeared reduced in size when compared to their in vivo counterparts due mostly to a reduction in the total number of segments. Nevertheless, these cells retained several primary dendritic trunks and their overall mean segment length was longer. These supposedly 'mature' cultured P-cells never reached full adult development: a discriminant analysis classified them as resembling those from intact animals of 13 days but often maintaining some properties of newborn animals. These results demonstrate that the presence of all normal inputs is required to achieve the full elaboration and the planar disposition of the P-cell dendrites.     

Adaptive changes of vertical vestibulo-ocular reflex induced by tenectomy of vertical recti muscles and neuronal behavior related to vertical eye movement in the region of the interstitial nucleus of Cajal in alert cats

Experiments were performed in alert cats to examine adaptive changes of the vertical vestibulo-ocular reflex (VOR) induced by tenectomy of the vertical recti muscles of one eye and behavior of neurons in the region of the interstitial nucleus of Cajal (INC) during this adaptation. Continuous pitch rotations (0.11 Hz) of a constant amplitude (+/- 10 degrees) with only the operated eye uncovered produced a gradual and significant increase in VOR gain that started within 15 min, reaching a plateau within 1 h. When only the normal eye was allowed to view again, VOR gain quickly decreased to the control values within 10 min. Such reversible gain change was not observed when visual input was not allowed to the operated eye, indicating that these changes are adaptive ones to reduce visual-vestibular conflict. A total of 18 neurons were recorded from the INC region during the VOR adaptation. These include 9 eye-movement-related neurons (8 vertical burst-tonic neurons and 1 vertical tonic neuron) and 9 other neurons that did not show close correlation with eye movement but were activated by pitch rotations (tentatively called pitch cells). During adaptive gain increase of the vertical VOR, all the vertical burst-tonic and tonic neurons showed a significant gain increase, whereas a significant change in response gain was observed in only 1 of the 9 pitch cells, indicating that vertical burst-tonic neurons in the INC region are involved in the adaptive gain increase in the vertical VOR.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pyramidal cortical cell morphology studied by multivariate analysis: effects of neonatal thyroidectomy, ageing and thyroxine-substitution therapy

The changes produced on the whole dendritic morphology of layer III cortical pyramidal neurons by neonatal hypothyroidism, induced in rats by thyroidectomy at 10 days of age (T), as well as those changes related to ageing, have been studied in rats at 40 and 80 days of age. For these purposes, the dendritic structure of these neurons was defined by a set of 10 variables whose measurements were analyzed using multivariate methods. The effect of tyroxine (T4) substitution therapies applied to T rats between 12-40 and 30-80 days of age has been further investigated with the same mathematical methodology. The results obtained from the analyses performed show that hypothyroidism affects both the apical tuft and the basal dendritic arborization of these neurons. The observed damage was similar: a decrease of the total length of the dendritic segments of the apical tuft and the basal arborization. This change, however, was detected in these two different subregions with a different timing. These results seem to reinforce our findings concerning the selective effect of T on different sites of these neurons. On the other hand, 3 morphological changes have been revealed regarding the development of the pyramidal neuron studied: (1) the total length of the apical tuft dendritic segments increases from 40 to 80 days of age; (2) the total length of the basal dendritic segments decreases from 40 to 80 days of age; and (3) the perimeter of the cell body decreases from 40 to 80 days of age. Finally, the results obtained did not allow us to detect any recovery of the damage induced by T, as a consequence of the T4 substitution therapies applied.     

A quantitative dendritic analysis of wernicke's area in humans. I. Lifespan changes

Age-related increases and decreases have been described in cortical dendritic neuropil. Here, we examine age-related changes in the basilar dendrites of supragranular pyramidal cells in human superior temporal gyrus (i.e., Wernicke's area) of left and right hemispheres. Tissue was obtained from 20 neurologically normal right-handers from 18–79 years: 10 males (M_age = 52.2 years; SD _age = 17.4) and 10 females (M_age = 47.8; SD_age = 20.5). In tissue prepared by a modified rapid Golgi technique, ten pyramidal cells were sampled from each hemisphere and evaluated according to the following parameters: total dendritic length, mean dendritic length, and dendritic segment count. Despite considerable interindividual variation, the data exhibited significant dendritic degeneration with aging. There was an age-related decrease in total dendritic length (r[20] = ?0.44; P < 0.05) and especially in mean dendritic length (r[20] = –0.69; P < 0.001) with increasing age. Age-mean dendritic length correlations were negative for all segment orders and revealed a progressive decrease in segment length in more distal branches. The number of dendritic segments remained relatively stable across the age span sampled. The data also indicated that interhemispheric dendritic asymmetries decreased with age. Individuals under 50 years of age had significantly greater total dendritic length values in the left hemisphere. Interhemispheric dendritic differences were not significant in individuals over 50. © 1993 Wiley-Liss, Inc.