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S M Sherman

Publications and source records attributed to S M Sherman.

At least 73 records · Page 4Linked to original sources
PubMed1987

Passive cable properties and morphological correlates of neurones in the lateral geniculate nucleus of the cat.

1. We used an in vivo preparation of the cat to study the passive cable properties of sixteen X and twelve Y cells in the lateral geniculate nucleus. Cells were modelled as equivalent cylinders according to Rall's formulations (Rall, 1959a, 1969, 1977). We injected intracellular current pulses into these geniculate neurones, and we analysed the resulting voltage transients to obtain the cable parameters of these cells. In addition, fifty-four physiologically characterized neurones were labelled with horseradish peroxidase (HRP) and analysed morphologically. 2. Analysis of HRP-labelled geniculate neurones showed that the dendritic branching pattern of these cells adheres closely to the 3/2 power rule. That is, at each branch point, the diameter of the parent branch raised to the 3/2 power equals the sum of the diameters of the daughter dendrites after each is raised to the 3/2 power. Furthermore, preliminary data indicate that the dendritic terminations emanating from each primary dendrite occur at the same electrotonic distance from the soma. These observations suggest that both X and Y cells meet the geometric constraints necessary for reduction of their dendritic arbors into equivalent cylinders. 3. We found a strong linear relationship between the diameter of each primary dendrite and the membrane surface area of the arbor emanating from it. We used this relationship to derive an algorithm for determining the total somatic and dendritic membrane surface area of an X and Y cell simply from knowledge of the diameters of its soma and primary dendrites. 4. Both geniculate X and Y cells display current-voltage relationships that were linear within +/- 20 mV of the resting membrane potential. This meant that we could easily remain within the linear voltage range during the voltage transient analyses. 5. X and Y cells clearly differ in terms of many of their electrical properties, including input resistance, membrane time constant and electrotonic length. The difference in input resistance between X and Y cells cannot be attributed solely to the smaller average size of X cells, but it also reflects a higher specific membrane resistance (Rm) of the X cells. Furthermore, X cells exhibit electrotonic lengths slightly larger than those of Y cells, but both neuronal types display electrotonic lengths of roughly 1. This indicates that even the most distally located innervation to these cells should have considerable influence on their somatic and axonal responses.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1987

Morphology of physiologically identified retinogeniculate X- and Y-axons in the cat.

1. We studied the morphology of individual, physiologically identified retinogeniculate axons in normal adult cats. The axons were recorded in the lateral geniculate nucleus or in the subjacent optic tract, characterized as X or Y by physiological criteria, penetrated, and injected with horseradish peroxidase. With subsequent application of appropriate histochemistry, the enzyme provides a complete label of the terminal arbors and parent trunks for morphological analysis. We have recovered for such analysis 26 X- and 25 Y-axons; of these, 14 X- and 12 Y-axons were studied in detail. 2. Within the optic tract, the parent trunk of every X-axon is located closer to the lateral geniculate nucleus and thus further from the pial surface than that of every Y-axon. This probably reflects the earlier development of X- than of Y-axons. Furthermore, the parent axon trunks of the X-axons are noticeably thinner than are those of the Y-axons. Every retinogeniculate X- and Y-axon in our sample branches within the optic tract. One of these branches heads dorsally to innervate the lateral geniculate nucleus and one heads medially and rostrally toward the midbrain, although none of these labeled axons were traced to a terminal arbor beyond the lateral geniculate nucleus. For Y-axons, all branches are of comparable diameter, but for X-axons, the branch heading toward the lateral geniculate nucleus is always noticeably thicker than is the branch directed toward the midbrain. 3. Every retinogeniculate X- and Y-axon produces the greatest portion of its terminal arbor in lamina A (if from the contralateral retina) or A1 (if from the ipsilateral retina). These arbors typically extend across most of the lamina along a projection line. Not a single terminal bouton from any axon was found in the inappropriate lamina A or A1 (i.e., in lamina A for ipsilaterally projecting axons or in lamina A1 for contralaterally projecting ones). Occasionally, an X-axon also innervates the medial interlaminar nucleus, and even more rarely does an X-axon innervate the C-laminae. In contrast, nearly all Y-axons from the contralateral retina branch to innervate part of the C-laminae (probably lamina C), and most from either retina also innervate the medial interlaminar nucleus. Although these details imply considerable variation in the overall pattern of retinogeniculate innervation for both X- and Y-axons, we found no physiological properties to correlate with this variation.(ABSTRACT TRUNCATED AT 400 WORDS)

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PubMed1986

Morphology of retinogeniculate X and Y axon arbors in monocularly enucleated cats.

We examined the terminal arbors of single, physiologically identified retinogeniculate X and Y axons from the remaining retinas of adult cats raised from birth with monocular enucleation. These were compared with arbors of X and Y axons in normally reared cats. We used intra-axonal injections of horseradish peroxidase to label each axon after recording its response properties. While the axons in monocularly enucleated cats exhibited normal response properties, both X and Y axons in these cats had abnormally large terminal arbors. Each of the hypertrophied X arbors appeared to be completely confined to the single geniculate lamina A or A1 appropriate to its eye of origin (i.e., lamina A for the contralateral retina and lamina A1 for the ipsilateral retina). In contrast, in addition to their normal terminations, most of the Y arbors seemed to extend well into laminae normally innervated only by the retina that was removed. Thus most or all of the translaminar sprouting previously reported for monocularly enucleated cats appears to reflect extensions of Y axon arbors. These data, in addition to earlier, analogous data from young kittens and cats reared with monocular lid suture, suggest the following sequelae during postnatal development: the retinogeniculate X arbors mature first and develop exuberant arbors that are later competitively pruned as the Y axons expand their innervation of the lateral geniculate nucleus; monocular lid suture prevents the Y axons from succeeding in this competition, so they fail to establish normal arbors and cannot reduce the exuberant X arbors; monocular enucleation offers a less resistant path in the denervated laminae for the rapidly growing Y arbors from the remaining eye, and the expansion of these arbors there reduces the competitive pressure on the exuberant X arbors. Thus, in monocularly enucleated cats, sprouting is limited to Y axons, either because only they possess the capacity to sprout or because they are in the midst of a period of relatively rapid growth at the time of the neonatal enucleation. The X axon arbors are also abnormally large within their appropriate laminae. This occurs presumably because they are able to maintain their immature exuberance, although we cannot rule out the possibility that they are pruned and later regrow to the final size seen in our experiments.

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PubMed1986

Role of competitive interactions in the postnatal development of X and Y retinogeniculate axons.

The cat's retinogeniculate pathway is largely composed of X and Y axons, which represent two distinct neuronal streams organized in parallel. Our earlier data, summarized in the previous paper, suggest that the postnatal development of retinogeniculate axon arbors is characterized by competitive interactions between the X and Y axons. Thus, during development, X arbors in lamina A or A1 are initially broad or exuberant before the Y arbors begin to develop adultlike arbors; the X arbors then shrink to their adult form as the Y arbors grow and establish their mature complement of connections; monocular lid suture prevents the rapid growth of Y arbors, which in turn prevents the pruning of X arbors; and monocular enucleation at birth allows X arbors from the remaining eye to retain their exuberance although completely confined to their appropriate lamina A or A1, whereas the Y arbors develop aberrant extensions into adjacent, previously denervated laminae. We now provide additional evidence for the role of competition between retinogeniculate X and Y axons during development. The addition of visual deprivation by lid suture of the remaining eye to monocular enucleation at birth causes no apparent change in the morphology of X arbors in laminae A and A1. In contrast, the Y arbors of such cats continue to form extensive translaminar sprouts in the previously denervated laminae despite severely reduced terminations in the lamina A or A1 normally innervated by the remaining eye. We interpret these new data, in conjunction with our earlier data, as follows. If retinogeniculate X and Y arbors complete for synaptic space during postnatal development, terminations of Y axons can be affected by lid suture only in geniculate laminae where terminations of X axons are also present. Thus, Y axon arbors are severely reduced in deprived lamina A or A1 following lid suture whether or not the other eye is removed. Where X arbors are not present, such as in lamina C or the laminae inappropriate for the remaining eye after removal of the other, the lid suture has no obvious effect on development of the Y arbors.

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PubMed1986

The control of retinogeniculate transmission in the mammalian lateral geniculate nucleus.

In the mammalian visual system, the lateral geniculate nucleus is commonly thought to act merely as a relay for the transmission of visual information from the retina to the visual cortex, a relay without significant elaboration in receptive field properties or signal strength. However, many morphological and electrophysiological observations are at odds with this view. Only 10-20% of the synapses found on geniculate relay neurons are retinal in origin. Roughly half of all synapses derive from cells in layer VI of visual cortex; roughly one third are inhibitory and GABAergic, derived either from interneurons or from cells of the nearby perigeniculate nucleus. Most of the remaining synapses probably derive from cholinergic, noradrenergic, and serotonergic sites within the brainstem reticular formation. Moreover, recent biophysical studies have revealed several ionic currents present in virtually all thalamic neurons. One is a Ca2+-dependent K+ current underlying the afterhyperpolarization (or the IAHP), which may last up to 100-200 ms following an action potential. Activation of the IAHP leads to spike frequency adaptation in response to a sustained, suprathreshold input. Intracellular recordings from other neuronal preparations have shown that the IAHP can be blocked by noradrenaline or acetylcholine, leading to an increased cellular excitability. Another ionic current results from a voltage- and time-dependent Ca2+ conductance that produces a low threshold spike. Activation of this conductance transforms a geniculate neuron from a state of faithful relay of information to one of bursting behavior that bears little relationship to the activity of its retinal afferents. We propose that state-dependent gating of geniculate relay cells, which may represent part of the neuronal substrate involved in certain forms of selective visual attention, can be effected through at least three different mechanisms: conventional GABAergic inhibition, which is largely controlled via brainstem and cortical afferents through interneurons and perigeniculate cells; the IAHP, which is controlled via noradrenergic and cholinergic afferents from the brainstem reticular formation; and the low threshold spike, which may be controlled by GABAergic inputs, cholinergic inputs, and/or the corticogeniculate input, although other possibilities also exist. Furthermore, it seems likely that gating functions involving the corticogeniculate pathway are suited to attentional processes within the visual domain (e.g., saccadic suppression), whereas brainstem inputs seem more likely to have more global effects that switch attention between sensory systems.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1986

Alpha and beta cells projecting from retina to lamina A of the lateral geniculate nucleus in normal cats, monocularly deprived cats, and young kittens.

We strictly limited small injection of horseradish peroxidase (HRP) to lamina A of the lateral geniculate nucleus of cats. This was done to label retrogradely only the alpha (Y) and beta (X) classes of retinal ganglion cell. Eighty-six such injections at a range of matched eccentricities were made bilaterally in 9 normal adult cats, 7 cats reared from birth to adulthood with monocular lid suture, and 9 normal kittens at 4 weeks of age; 5348 alpha and beta cells were retrogradely labeled from these injections. Quantitative measurements were made from these labeled cells and compared among 4 experimental conditions, these being normal adult retinas, the nondeprived and deprived retinas of lid sutured cats, and the retinas of kittens. Each injection led to a similar relative ratio of labeled alpha and beta cells (typically 5-15% alpha cells) that did not differ significantly among the experimental conditions, but further analysis suggested a slight diminution of labeled alpha cells in deprived retinas. Because the larger arbors of retinogeniculate Y axons are more likely to penetrate small geniculate HRP injection sites from eccentric locations than would be the case for the more restricted arbors of X axons, a normal tendency resulted for the peripheral halo of zones of retrograde labeling to be dominated by alpha cells. Thus a more accurate reflection of the relative numbers of labeled alpha and beta cells would result from considering only the core of zones of retrograde labeling. When this is done, deprived retinas exhibited relatively fewer labeled alpha cells than did normal, nondeprived, or kitten retinas. This may relate to prior observations (Sur et al. 1982) that abnormally few Y axons from the deprived retina innervate lamina A. No statistically significant differences in alpha or beta cell size were seen among normal, nondeprived, and deprived retinas, although both of these cell types in the kittens were equally smaller than their normal adult counterparts. This is particularly interesting in view of the postnatal growth of retinogeniculate axon arbors (Sur et al. 1984). The results are not surprising for alpha cells, since retinogeniculate Y axon arbors grow considerably after 4 weeks of age, but they are surprising for beta cells, since retinogeniculate arbors of X axons decrease after 4 weeks of age. This suggests no clear, general relationship between soma size and the extent of a cell's axonal arbor.(ABSTRACT TRUNCATED AT 400 WORDS)

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PubMed1985

Projection patterns of individual X- and Y-cell axons from the lateral geniculate nucleus to cortical area 17 in the cat.

Horseradish peroxidase was injected intracellularly into single, physiologically-identified X- and Y-cell geniculocortical axons projecting to area 17 of the cat. This injection anterogradely labeled the axon terminal fields in cortex and retrogradely labeled the somata of these same axons in laminae A and A1 of the lateral geniculate nucleus (LGN). The laminar projections of 21 X- and 15 Y-cell axons were analyzed. For these, the laminar terminations of ten X- and seven Y-cell axons were also related to their cells' positions in the A-laminae. The terminal fields of X- and Y-cell axons overlapped substantially in layers IV and VI of area 17. Some X-cells terminated mainly in IVb, others mainly in IVa, and still others throughout IVa and IVb. The latter two groups also projected up to 100 micron into lower layer III. Y-cells terminated primarily in layer IVa and projected up to 200 microns into lower layer III. Some also arborized throughout the depth of layer IVb. Both X- and Y-cell axons terminated throughout the depth of layer VI, although more so in the upper half. We found no relationship between the diameter of the parent axon and its sublaminar projection within layer IV. Within layer IV, X-cell axons generally terminated within a single, continuous clump and had surface areas of 0.6 to 0.9 mm2. Axons of Y-cells often terminated in two to three separate clumps, separated by terminal free gaps 400 to 600 micron wide. Their total surface areas, including gaps, were 1.0 to 1.8 mm2, roughly 1.6 times the surface areas of X-cell axons. Despite considerable overlap, Y-cell arbors contained significantly more boutons than did X-cell arbors. The sublaminar projections of the X- and Y-cell axons within layer IV reflected the locations of the cells' somata within the depth of the A-laminae. X-cells located in the dorsal or ventral thirds of the depths of the laminae projected mainly to layer IVa or throughout layer IV in cortex. Those located in the central thirds projected mainly to layer IVb. Y-cells showed a similar positional relationship, but they appeared to follow different rules. Y-cells in the outer thirds of the A-laminae projected mainly to layer IVa; those in the central thirds, in addition, expanded their projections to include layer IVb. In general, larger sized somata in the LGN gave rise to more widely spreading terminal arbors and greater numbers of boutons in cortex than did smaller somata.(ABSTRACT TRUNCATED AT 400 WORDS)

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PubMed1985

Termination patterns of individual X- and Y-cell axons in the visual cortex of the cat: projections to area 18, to the 17/18 border region, and to both areas 17 and 18.

Horseradish peroxidase was injected intracellularly into single, physiologically identified X- and Y-cell geniculocortical axons that projected to area 18, to the 17/18 border region, or to both areas 17 and 18 via branching axons. The axon terminal fields in cortex were labeled anterogradely, and the cell bodies of the axons in the A-laminae, lamina C, and the medial interlaminar nucleus (MIN) of the dorsal lateral geniculate nucleus (LGN) were labeled retrogradely. The laminar projections in area 18 of eight Y-cells and one geniculate, non-Y-cell were analyzed. Most of the cells arborized densely within layer IVa and the lower 200 to 400 microns of layer III. Most provided little or no input to layer IVb or layer VI. Thus, the laminar projections of Y-cells to layer IV of area 18 were similar to those of their area 17 counterparts, although the input to layer III was greater and rose much higher in area 18 than in area 17. The terminal arbors in area 18 were two to three times larger in lateral extent than those in area 17. They spread over 2.0 to 2.8 mm2 of layer IV and occupied proportionately much greater regions of area 18 than the Y-cell arbors in area 17. This may partially account for the large receptive fields of cortical cells in area 18, and it indicates that a small region of area 18 may receive converging inputs from a relatively wide retinotopic region of the LGN. The terminal arbors were also highly asymmetric, generally being two to four times longer anteroposteriorly than mediolaterally. These asymmetric arbors may form the structural basis for the anisotropic organization of the retinotopic map in area 18. We recovered three cells (two Y, one X) whose axons arborized in the border zone between areas 17 and 18. One Y-cell axon had a receptive field located in the ipsilateral visual hemifield and it arborized in a small region restricted almost exclusively to the border zone. The other two cells had receptive fields on or adjacent to the vertical meridian, and they terminated on either side of the 17/18 border region as well as within it. Thus, geniculate afferents representing the ipsilateral hemifield or the vertical meridian appear to have different patterns of termination on and adjacent to the 17/18 border zone. Also, some X-cell input may invade area 18 in the region immediately adjacent to the border zone.(ABSTRACT TRUNCATED AT 400 WORDS)

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PubMed1985

Morphology and physiology of single neurons in the medial interlaminar nucleus of the cat's lateral geniculate nucleus.

Physiological studies have shown that the cat's retinogeniculocortical system is comprised of at least three parallel and independent pathways, the W-, X-, and Y-cell pathways. The morphological correlates of the constituent W-, X-, and Y-cells have been determined both in the retina and in the A and C laminae of the lateral geniculate nucleus. The aim of this study was to extend these structure/function relationships to neurons in laminae 1 and 2 of the medial interlaminar nucleus (MIN), which is a division of the cat's dorsal lateral geniculate nucleus. We used intracellular injection of horseradish peroxidase (HRP) into individual, physiologically identified MIN neurons. Since this procedure may yield an unrepresentative sample of MIN neurons, two controls were performed. First Nissl staining showed that the soma sizes of intracellularly labeled cells were representative of those of all MIN cells. Second, retrograde labeling following HRP injections into the optic radiations or specific visual cortical areas showed that the intracellularly labeled MIN cells were representative of MIN relay neurons. Many of the retrogradely labeled cells were so well filled that their entire dendritic arbors were revealed. Of 70 MIN neurons recorded physiologically, 22 were injected with HRP and successfully recovered. We also completely labeled the somata and dendrites of 114 MIN neurons from HRP injections into the optic radiations and retrogradely labeled 165 MIN neurons by injection of HRP into visual cortical areas. Our sample of intracellularly injected neurons, which were all Y-cells, were morphologically representative of all MIN relay cells. We thus conclude that laminae 1 and 2 of the MIN contain a nearly homogeneous population of Y-cells with properties essentially identical to those of Y-cells in the A and C laminae of the lateral geniculate nucleus. When viewed in the coronal plane, MIN projection neurons typically exhibited oval or elongated somata. In the medial and ventral parts of the MIN, these somata were smaller and more flattened. MIN soma sizes extended over the full range of those seen in the A laminae. Dendritic arbors of most MIN relay neurons radiated in a fairly spherical fashion. In the medial and ventral parts of the MIN, however, dendrites were oriented in a more bipolar fashion, but intermediate forms between spherical and bipolar arbors were also common. Dendrites of MIN projection neurons were typically smooth; most primary dendrites were straight, but secondary dendrites were more variable in structure.(ABSTRACT TRUNCATED AT 400 WORDS)

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PubMed1984

Fine structural morphology of identified X- and Y-cells in the cat's lateral geniculate nucleus.

Four physiologically identified neurons in the A laminae of the cat's dorsal lateral geniculate nucleus were filled with horseradish peroxidase and studied using the electron microscope. Two were X-cells and two were Y-cells. Each had electrophysiological properties appropriate for its X- Or Y-cell class, and each also had an axon that projected into the optic radiation, indicative of a geniculocortical relay cell. Representative samples from about 10% of each neuron's entire dendritic arbor (proximal and distal) were taken to obtain an estimate of the types and distributions of synapses contacting these arbors. One X-cell had a cytoplasmic laminar body, but there were no other significant cytological differences seen among the neurons. Common to each of the neurons were the following synaptic features: (i) retinal terminals (r.l.p.) were mostly or entirely restricted to proximal dendrites or dendritic appendages (less than 100 microns from the soma). These terminals constituted about 15-25% of the synapses on the proximal dendrites. (ii) Terminals with flattened or pleomorphic synaptic vesicles (f. terminals) were predominant on the proximal dendrites (30-55% of the total synapses for that region) and were mainly located near the retinal terminals. A smaller percentage (10-20%) were also distributed onto the distal dendrites. (iii) Small terminals with round synaptic vesicles (r.s.d.), many presumably having a cortical origin, predominated (60-80%) on distal dendrites (greater than 100 microns), but also formed a large proportion (40-70%) of the synapses on the intermediate (50-150 microns) dendrites. Total synaptic contacts for one X-cell and one Y-cell were estimated at about 4000 and 5000, respectively. The major fine structural differences observed between X- and Y-cells were almost entirely related to the retinal afferents. First, the retinal synapses for X-cells were mostly made on to dendritic appendages (spines, etc.), whereas Y-cells had most of their retinal synapses onto the shafts of primary and proximal secondary dendrites (that is, near branch points. Second, the retinal terminals that contacted X-cell dendrites nearly always formed triadic arrangements that included nearby f. terminals, but those on Y-cells rarely did so. Finally, the main type of f. terminals associated with X-cells were morphologically different from most of those associated with the Y-cells, and this also related directly to the triadic arrangements; that is, f. terminals in the triadic arrangements were morphologically distinguishable from f. terminals that did not participate in triadic arrangements.(ABSTRACT TRUNCATED AT 400 WORDS)

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PubMed1984

Structure/function relationships of retinal ganglion cells in the cat.

Intracellular recording and horseradish peroxidase (HRP) iontophoresis was used to define structure/function relationships for single retinal ganglion cells in the intact cat eye. Fifteen physiologically characterized cells were labeled as follows. Five W-cells had gamma morphology, 6 X-cells had beta morphology, and 1 Y-cell had alpha morphology, and these relationships support earlier conclusions. However, one cell could not be physiologically classified despite beta morphology, one X-cell was not a beta cell, and one Y-cell was not an alpha cell. Whether these unusual structure/function relationships represent an artifact of methodology or complications to be added to prevailing notions requires further study.

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PubMed1984

The position sensitivity of retinal X- and Y-cells in cats.

We have devised a measure of a retinal ganglion cell's sensitivity to changes in the spatial position of a grating stimulus. At maximum, this relative position sensitivity is a scaled product of the stimulus spatial frequency and the cell's fundamental component of response to that spatial frequency. We obtained the relative position sensitivity as a function of spatial frequency for 13 X-cells and 14 Y-cells. X-cell functions peak at significantly higher spatial frequencies than do those of Y-cells. At their peaks, X-cells display significantly higher values of relative position sensitivity than do Y-cells. However, Y-cells have higher position sensitivity at lower spatial frequencies, but exhibit less of a range of variation from maximum to minimum than do X-cells. These results are consistent with a hypothesis that Y-cells provide the crucial substrate for form vision at lower spatial frequencies, while X-cells are important for details carried by the higher spatial frequencies.

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PubMed1984

Spatial contrast sensitivity of dark-reared cats with striate cortex lesions.

We measured the spatial contrast sensitivity of two dark-reared cats before and after bilateral ablations of area 17 and parts of area 18. These lesions produced large deficits in the contrast sensitivity of both cats at intermediate and high spatial frequencies. This postoperative reduction in contrast sensitivity in dark-reared cats is relatively similar to the sensitivity deficits produced by the same cortical lesions in normally reared cats. However, both pre- and postoperatively, the normally reared cats exhibited contrast sensitivity that is clearly superior to that of the dark-reared cats. The results demonstrate both that striate cortex is significantly involved in the spatial contrast sensitivity of dark-reared cats and that dark rearing produces widespread deficits, independent of those in striate cortex, through much of the visual system.

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PubMed1983

Development of neuronal response properties in the cat dorsal lateral geniculate nucleus during monocular deprivation.

We measured response properties of X- and Y-cells from laminae A and A1 of the dorsal lateral geniculate nucleus of monocularly lid-sutured cats at 8, 12, 16, 24, and 52-60 wk of age. Visual stimuli consisted of small spots of light and vertically oriented sine-wave gratings counterphased at a rate of 2 cycles/s. In cats as young as 8 wk of age, nondeprived and deprived neurons could be clearly identified as X-cells or Y-cells with criteria previously established for adult animals. Nonlinear responses of Y-cells from 8- and 12-wk-old cats were often temporally labile; that is, the amplitude of the nonlinear response of nondeprived and deprived cells increased or decreased suddenly. A similar lability was not noted for the linear response component. This phenomenon rarely occurred in older cats. At 8 wk of age, Y-cell proportions (number of Y-cells/total number of cells) in nondeprived and deprived A-laminae were approximately equal. By 12 wk of age and thereafter, the proportion of Y-cells in deprived laminae was significantly lower than that in nondeprived laminae. At no age was there a systematic difference in response properties (spatial resolution, latency to optic chiasm stimulation, etc.) for Y-cells between deprived and nondeprived laminae. Spatial resolution, defined as the highest spatial frequency to which a cell would respond at a contrast of 0.6, was similar for nondeprived and deprived X-cells until 24 wk of age. In these and older cats, the mean spatial resolution of deprived X-cells was lower than that of nondeprived X-cells. This difference was noted first for lamina A1 at 24 wk of age and later for lamina A at 52-60 wk of age. The average latency of X-cells to optic chiasm stimulation was slightly greater in deprived laminae than in nondeprived laminae. No such difference was seen for Y-cells. Cells with poor and inconsistent responses were encountered infrequently but were observed far more often in deprived laminae than in nondeprived laminae. Lid suture appears to affect the development of geniculate X- and Y-cells in very different ways. Not only is the final pattern of abnormalities quite different between these cell groups, but the developmental dynamics of these abnormalities also differ.

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PubMed1982

Monocular deprivation affects X- and Y-cell retinogeniculate terminations in cats.

The X- and Y-cell pathways in cats form two functionally distinct, parallel systems from the retina through the lateral geniculate nucleus (LGN) to the visual cortex1-4. We recently used the technique of intraaxonal injection of horseradish peroxidase (HRP) to demonstrate major differences between X- and Y-cells in their retinogeniculate termination patterns5 (compare Figs 1 alpha and 2 alpha). Normally, axons of X-cells innervate geniculate lamina A or A1 (depending on the eye of origin) in narrow zones oriented perpendicular to the lamination. Some X-cells also terminate sparsely (that is, with few boutons) in the medial interlaminar nucleus (MIN), a subdivision of the LGN. Y-cell axons terminate either in laminae C and A (from the contralateral retina) or in lamina A1 (from the ipsilateral retina) in broad zones5,6, and most also terminate densely (with many boutons) in the MIN. We now report that cats raised with monocular lid suture develop abnormal retinogeniculate termination patterns. Many X-cell axons arising from the deprived eye have unusually broad terminal fields in lamina A or A1, and some also densely innervate the MIN. Many Y-cell axons from the deprived eye have dramatically shrunken or absent terminal fields in the A laminae and MIN. These changes constitute the most peripheral effects of monocular deprivation discovered so far, are consistent with previous reports of functional abnormalities among deprived geniculate neurones4,7,8 ad suggest possible mechanisms by which the visual environment influences neuronal development.

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PubMed1982

Retinogeniculate terminations in cats: morphological differences between X and Y cell axons.

We injected horseradish peroxidase into single, physiologically identified, optic tract axons of X and Y cells in cats and studied their termination patterns in the lateral geniculate nucleus. All X cell axons innervate lamina A or A1 in narrow zones, and some sparsely innervate the medical interlaminar nucleus. All Y cell axons have broad terminal zones in laminae A and C (from the contralateral retina) or lamina A1 (if ipsilateral), and most innervate the medial interlaminar nucleus densely.

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