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PubMedDate not supplied

Effects of wound architecture and suture technique on postoperative astigmatism.

BACKGROUND AND OBJECTIVE: A prospective randomized investigation was performed to evaluate the effects of wound architecture and suture techniques on postoperative astigmatism after phacoemulsification and intraocular lens implantation. PATIENTS AND METHODS: Two hundred eyes with preexisting with-the-rule astigmatism were randomized into four groups: (1) sutureless scleral tunnel frown incision, (2) scleral tunnel frown incision with a horizontal suture, (3) scleral tunnel frown incision with both a horizontal and a running suture, and (4) posterior limbal acute beveled cataract incision with a running suture. All the incisions were placed in the vertical steep meridian. RESULTS: Data were analyzed from 128 cases with 1-year follow-up. The results revealed that at the 2-month postoperative visit, preexisting astigmatism was significantly reduced in group 1 (P = .029) and significantly increased in groups 3 (P = .020) and 4 (P = .005). There was no significant change in group 2 (P = .06). By the 1-year postoperative visit, there was no significant difference in astigmatism from preoperative levels for all four groups. Vector analysis revealed no significant difference in the mean surgically induced cylinder at 1 year in all four groups. The number of eyes with induced against-the-rule astigmatism, however, was significantly higher than the number of eyes with induced with-the-rule astigmatism in all four groups (P <.01). CONCLUSION: The authors found that sutured wounds placed in the vertical steep meridian may initially increase with-the-rule astigmatism, whereas nonsutured wounds placed in the vertical steep meridian may initially reduce with-the-rule astigmatism. By 1 year, however, a mean flattening of the vertical steep meridian was observed in the three groups with sutures as well as in the group without sutures.

Aged↗
PubMed1996

Application of a modified keratometer in the study of corneal topography on Chinese subjects.

A corneal topography study was carried out on Hong Kong Chinese subjects using a modified keratometer. The Chinese corneal topography measured by this modified keratometer was similar to other studies using the Wesley-Jessen Photo Electronic Keratoscopy (PEK) System 2000. The mean p-values along the horizontal meridian and the vertical meridian were 0.82 and 0.87, respectively. A negative correlation was found between the p-value and the central corneal radius along the horizontal meridian which may indicate that a steeper central cornea will have a greater p-value. However, the correlation coefficient of 0.56 was not too certain for this conclusion to be drawn. A difference of 0.04 was found between the horizontal p-value and the vertical p-value, which may be a result of the tight lid tension along the vertical meridian. This modified keratometer can be considered as an inexpensive instrument for the study of corneal topography.

Adult↗
PubMed1996

Quantitative clinical anatomy of the human cornea in vivo. A morphometric study by ultrasonic pachymetry and computer-assisted topographic videokeratoscopy.

The cornea is the most important refractive element in the human ocular system, providing approximately two thirds of the eye's refractive power in the nonaccommodative state. The methods of description and analysis of the corneal anatomy in vivo continue to be refined thanks to the increased interest aroused by the advent of corneal refractive surgery, which aims to modify the dioptric power of the ocular system by altering the thickness and the radius of curvature of the cornea. In the present study we report quantitative morphometric data of corneal thickness and the radius of curvature of the anterior surface of the cornea obtained in vivo from normal human subjects using ultrasonic pachymetry and computer-assisted topographic videokeratoscopy. We found a highly significant statistical correlation in the distribution of corneal thickness and the radius of curvature of the anterior surface of the cornea along the principal corneal meridians (horizontal and vertical meridians) and within three different concentric zones of the cornea, 2, 4 and 6 mm, respectively, from the geometric center along the principal meridians. Correlation was also found for the same morphometric parameters between the right and the left eye. By contrast, no correlation was found between corneal thickness and the radius of curvature of the anterior surface of the cornea. These findings suggest that the adult human cornea is a structure characterized by a highly ordered tridimensional architecture and symmetry and that a specific distribution of corneal thickness and the radius of curvature of the anterior corneal surface along the principal meridians may be essential for the refractive function of the human corneal diopter in vivo.

Adult↗
PubMed1998

Liu-wei-dihuang: a study by pulse analysis.

Pulse analysis method was used in studying the traditional Chinese formula Liu-Wei-Dihuang as well as five of its main components (Rehmannia glutinosa, Cornus officinalis, Paeonia Suffruticosa, Poria cocos and Alisma plantogo-aquatica var oriental). Based on our recently developed resonance theory, we tried to elucidate the mechanism and mutual reactions of these meridian related herbs. Hot water herbal extracts were injected intraperitoneally into rats and the pressure pulse spectrum at the caudate artery was measured. The results of this study indicated that Liu-Wei-Dihuang mildly increased blood flow to meridians with lower resonance frequency: namely the liver C1, the kidney C2 and the spleen C3; but decreased blood flow to the higher resonance frequency organs and meridians: the lung C4, the stomach C5, the gall bladder C6, and the bladder C7. It also decreased the heart load C0. All of the five herb components increased blood flow to the kidney C2 and the spleen C3; but their effects on the high frequency organs varied. Alisma plantogo-aquatica var. oriental decreased the C0, C5, C6, C7; Poria cocos decreased C1, C4, C5, C6; Rehmannia glutinosa, Paeonia Suffruticosa decreased C0, C4, C5, C6, C7; Cornus officinalis increased C4 but decreased C0, C5, C6, C7.

Animals↗
PubMed2002

[Bioenergetic activity of bioactive spots in patients with chronic iron-deficiency anemia depending on the degree of its severity].

Identified in patients with anemia (irrespective of its severity) were significant deviations from the norm in energopotentials on biologically active points of meridians of the lungs and pancreas--the spleen. There has been ascertained a direct relation between the degree of anemia and lowering of indices of energopotentials on biologically active points of meridians of the lungs, three heaters, liver, kidneys, urinary bladder, which fact can be taken account of in assessment of degree of the pathological process, prognostication of its course. It will be noted that indices of meridian energopotentials are affected by the psychological state of the patients. Among patients with mild anemia vs those with moderately severe anemia personal conflict can come to be a more frequently encountered etiological factor. This warrants psychotherapeutic and energy-oriented correction to be embarked on.

Acupuncture Points↗
PubMed1996

[The detection and studies on the change of H+ concentration in the regular points of the rabbit suffering from arrhythmia induced by aconitine].

The past experiment showed that there was a specific change of H+ concentration in Neiguan (PC 6) of the rabbit suffering from arrhythmia induced by aconitine. When arrhythmia appeared, th ecocentration of H+ in Neiguan (PC 6) increased obviously. The authors found that it happened not only in the regular points but also along the course of the Heart Meridian and Pericardium Meridian in the furthe study and research. This may mean that on the course of the corresponding meridian there is a specific change of H+ concentration when the Zang-fu organs are in dysfunctional. But the mechanism and biological significance of the change of H+ concentration should remain to be further studied.

Aconitine↗
PubMed1999

Plaque radiotherapy of uveal melanoma with predominant ciliary body involvement.

BACKGROUND: There are several options for management of ciliary body melanoma, including plaque radiotherapy, charged particle irradiation, local resection, and enucleation. The choice of therapy depends on many factors, and plaque radiotherapy is often used. OBJECTIVES: To determine the outcome of plaque radiotherapy in the management of ciliary body melanoma and to identify the risk factors associated with the development of radiation complications, tumor recurrence, metastasis, and melanoma-related death after plaque radiotherapy of ciliary body melanoma. METHODS: We analyzed the clinical records of 136 patients with ciliary body melanoma who were treated with plaque radiotherapy between July 1976 and June 1992. RESULTS: The median follow-up period was 70 months. Using Kaplan-Meier survival estimates, the most frequent radiation complication at 5 years' follow-up was cataract, developing in 48% of the patients, followed by neovascular glaucoma (21%), retinopathy (20%), scleral necrosis (12%), and vitreous hemorrhage (11%). Visual acuity decrease (by > or =3 Snellen lines) was noted in 40% of the patients at 5 years. Kaplan-Meier estimates showed that 8% of the patients developed recurrence, 28% had metastasis, and 22% died of melanoma-related causes by 5 years. Univariate analysis demonstrated that the factors predictive of radiation cataract were superonasal (P = .003) and inferior tumor meridian (P = .02) compared with inferonasal meridian and apex dose rate greater than 57 cGy/h (P = .05). The development of neovascular glaucoma was significantly related to iris involvement with the ciliary body tumor (P<.001). The factors predictive of development of radiation retinopathy were base dose rate greater than 230 cGy/h (P = .03) and the presence of diabetes mellitus (P = .05). The only predictor of metastasis was tumor thickness greater than 7 mm (P = .02). The risk factors for melanoma-related death were the presence of metastasis (P<.001), tumor thickness greater than 7 mm (P = .02), and recurrence (P = .02). Multivariate analyses showed that the most significant variables predictive of the development of scleral necrosis were intraocular pressure greater than 15 mm Hg (P<.001) and tumor thickness greater than 7 mm (P = .007). The most significant predictive factors for vitreous hemorrhage were visual acuity of 20/40 to 20/200 (P = .02) and intraocular pressure greater than 15 mm Hg (P = .02). The best subset of independent predictors of vision decrease were mushroom tumor shape (P = .002), age older than 61 years (P = .006), and superonasal meridian (P = .04). The risks for melanoma-related death were presence of metastasis (P<.001) and tumor thickness greater than 7 mm (P = .01). There was no group of significant variables predictive for radiation cataract, neovascular glaucoma, retinopathy, tumor recurrence, and metastasis in multivariate analysis. CONCLUSIONS: Plaque radiotherapy offers 92% 5-year local control rate for ciliary body melanoma. Metastasis occurs in 28% of the patients treated with this method by 5 years. Patients with tumors greater than 7 mm in thickness are at greater risk than patients with thinner tumors for metastatic disease and melanoma-related death. Major radiation complications include radiation cataract, neovascular glaucoma, retinopathy, and scleral necrosis.

Adult↗
PubMed1986

Trapezoidal astigmatic keratotomy. Quantification in human cadaver eyes.

The mechanism by which surgical procedures correct astigmatism are incompletely understood and, therefore, the results are often unpredictable. In this study, a Terry keratometer was used to analyze the effect of each component part of a 3-, 4-, and 5-mm trapezoidal astigmatic keratotomy. Semiradial incisions along the horizontal meridian produced corneal flattening along the horizontal meridian twice that of the vertical meridian, therefore inducing positive cylinder astigmatism at 90 degrees. A single pair of tangential incisions placed 5 mm apart, when added to the semiradial incisions, accounted for 100%, 87%, and 78% of the maximal effect from the 3-, 4-, and 5-mm completed trapezoidal astigmatic keratotomies, respectively. This study suggests that maximal correction of astigmatism may be attained with a single set of tangential incisions placed 5 mm apart between two sets of semiradial incisions.

Astigmatism↗
PubMed1986

Dynamic shifts in corneal topography during the modified Ruiz procedure for astigmatism.

We utilized ten eye bank eyes to evaluate and quantitate the immediate corneal topographic shifts that occur after each stage of a modified Ruiz procedure for astigmatism. Computer digitization of photokeratoscope (Corneascope) photographs revealed that the initial two central paired tangential incisions induced an average of 5.10 diopters (D) of central astigmatism by flattening the meridian perpendicular to the incisions and by steepening the meridian 90 degrees away. Additional tangential incisions did not significantly alter the topography after placement of the first two central incisions. Addition of corridor incisions produced an additional 5.25 D of induced astigmatism by further extensive flattening of the incised meridian. The completed procedure produced an average of 11.03 D of astigmatic shift, but with a wide range of effect (7.15 to 12.96 D). With modification, the Ruiz procedure is a powerful keratorefractive surgical technique.

Astigmatism↗
PubMed1996

Distribution of M retinal ganglion cells in diurnal and nocturnal New World monkeys.

The topography of M ganglion cell distribution was studied in the retinae of two New World monkey species, the diurnal capuchin monkey Cebus apella and the nocturnal owl monkey Aotus azarae. Retinal whole mounts were stained by the neurofibrillar method of Gros-Schultze. As occurs with other diurnal primates, the Cebus M-ganglion cell density peaks in the foveal slope and declines towards the periphery. In the Aotus retina, the M ganglion cell density peaks in the area centralis and declines toward the periphery. In both species the cell density in the temporal, dorsal, and ventral meridians are similar for equivalent eccentricities. The cell density in the nasal meridian is higher than in the other meridians. The naso-temporal density ratio ranges between 1.2 and 4.3 in the Cebus and 1.6 and 2.2 in the Aotus. The total number of M-ganglion cells was 140,300 and 74,000 in the Cebus and Aotus retinae, respectively, corresponding to about 10% and 15.4% of the total retinal ganglion cell population in these species. The results indicate that M ganglion cells are similarly organized in both diurnal and nocturnal simians, but may be proportionally more important for the nocturnal species.

Animals↗
PubMed2002

Density gradients of trans-synaptically labeled collicular neurons after injections of rabies virus in the lateral rectus muscle of the rhesus monkey.

We evaluated the two-dimensional distribution of superior colliculus (SC) neurons visualized after retrograde transneuronal transport of rabies virus injected into the lateral rectus muscle of rhesus monkeys to test whether the density of projection neurons might play a role in the spatiotemporal transformation and vector decomposition. If this were the case, the number of horizontal eye movement-related SC neurons should increase with their distance from the rostral pole of the SC and decrease with their distance from the representation of the horizontal meridian. Labeled neurons of the intermediate SC layers were counted inside a 1-mm-wide band that matched the horizontal meridian of the collicular motor map. Local areal densities were plotted against distance from the rostral SC pole. At 2.5 days after inoculation, there was no labeling in the SC. At 3 days, moderate labeling appeared on both sides, mostly in the intermediate layers. At 3.5 days, cell numbers substantially increased and the laminar distribution changed as cells appeared in the superficial SC layers. At 3 days, rostrocaudal density profiles were unimodal, with peaks at locations near 50 degrees (contralateral SC) and 25-30 degrees (ipsilateral SC) horizontal eccentricity. At 3.5 days, distributions were bimodal due to the appearance of a second high-density region near the rostral pole of the SC. The distribution of SC neurons influencing the abducens nucleus, thus, was nonuniform. Caudal sites contained more neurons, but the experimentally observed density gradients were shallower than the theoretically predicted ones that would be necessary to fully account for the spatiotemporal transformation. Similarly, we studied the distributions of cell densities in the intermediate SC layers along an isoamplitude line (representing saccades of equal amplitudes but different directions). Consistent with theoretical estimates of the density gradients required for vector decomposition, we found that the concentrations of labeled cells were highest in the vicinity of the horizontal meridian but their decrease toward the periphery of the motor map was steeper than predicted. We conclude that SC cell density gradients cannot fully account for the spatiotemporal transformation and vector decomposition in the absence of an additional mechanism such as the previously demonstrated (Grantyn et al., [1997] Soc. Neurosci. Abstr. 23:1295; Moschovakis et al., [1998] J. Neurosci. 18:10219-10229) locus-dependent weighting of the strength of efferent projections to the saccade generators.

Animals↗
PubMed1977

Topographic organization of the projections from cortical areas 17, 18 and 19 onto the thalamus, pretectum and superior colliculus in the cat.

The distribution of cortical projections from areas 17, 18 and 19 to the lateral thalamus, pretectum, and superior colliculus was investigated with the autoradiographic tracing method. Cortical areas 17, 18 and 19 were demonstrated to project retinotypically and in register upon the dorsal lateral geniculate nucleus, medial interlaminar nucleus, lateral zone of the lateral posterior complex, nucleus of the optic tract and superior colliculus. Area 19 was shown to project retinotopically upon the pulvinar nucleus. Clear retinotopic organization was not demonstrable in the projections of areas 17, 18 and 19 to the reticular complex of the thalamus and ventral lateral geniculate nucleus, or in the projection of area 19 to the anterior pretectal nucleus. The cortical projections were employed to define the retinotopic organization of the nucleus of the optic tract, pulvinar nucleus, and later zone of the lateral posterior complex. The cortical projections show the vertical meridian to be represented caudally, with the lower visual field represented laterally, and the upper visual field medially, within the nucleus of the optic tract. The projections of area 19 to the pulvinar nucleus demonstrate the lower visual field to be represented rostrally and the upper field caudally in this mucleus; the vertical meridian to be represented at the lateral border and the visual field periphery to be represented at the medial border of the pulvinar nucleus. Cortical projections to the lateral zone of the lateral posterior complex demonstrate the lower visual field to be represented rostrally and the upper visual field caudally; the vertical meridian to be represented at the medial limit and the visual field periphery at the lateral border of the termination zones. On the basis of the experimental findings a new terminology is introduced for the feline lateral posterior complex. Divisions are proposed which correspond to zones with demonstrably distinct afferent input. The pulvinar nucleus is defined by the distribution of projections from area 19. Three flanking divisions are defined within the lateral posterior complex; a lateral division recipient of projections from area 17, 18 and 19, and interjacent division recipient of projections of the superficial layers of the superior colliculus, and a medial division flanking the tectorecipient zone medially.

Animals↗
PubMed1979

Thalamic projections to area 17 in a prosimian primate, Microcebus murinus.

Electrophysiological recording of single neurons was used to describe the representation of visual space in area 17, and the technique of retrograde transport of horseradish peroxidase (HRP) was applied to relate these results to projections from the thalamus in the prosimian primate Microcebus murinus. The visuotopic organization of area 17 was found to resemble that of other primates. On the dorsal surface, the border of area 17 corresponds to the representation of the vertical meridian. Proceeding medially across the surface the location of receptive fields descends along the vertical meridian, while moving caudally receptive fields progress temporally. Most of the dorsolateral surface is devoted to central vision and corresponds to a well developed area centralis. Following HRP injections in striate cortex, columns of labeled cells were found in the dorsal lateral geniculate (dLGN) extending orthogonally across all six layers. These columns run in a general ventrodorsal and caudorostral direction, parallel to a line connecting the cellular discontinuities corresponding to the optic disc. These discontinuities are present in magnocellular layer 1 and parvocellular layers 5 and 6, thus receiving from the nasal retina of the contralateral eye. The representation of the vertical meridian is situated in the ventromedial portion of the dLGN, and the monocular field is represented in the dorsal extremity. Anterior dLGN projects to the calcarine fissure (lower field) and posterior dLGN projects to the ventral surface of the cortex (upper field). Extrageniculate input to area 17 was found to originate from the pulvinar. HRP labeled cells were located in two distinct divisions of this nucleus, the cytoarchitecture of which is described. In addition, projections to occipital cortex were found to arise from the intralaminar nuclei.

Animals↗
PubMed1980

Retinotopic organization of striate and extrastriate visual cortex in the mouse.

Detailed retinotopic maps of primary visual cortex (area 17) and the extrastriate visual regions surrounding it (areas 18a and 18b) have been constructed for the C57BL/6J mouse using standard electrophysiological mapping techniques. Primary visual cortex (area 17), as defined cytoarchitectonically, contains one complete representation of the contralateral visual field, termed V1, in which azimuth and elevation lines are approximately orthogonal. The upper visual field is represented caudally and the nasal field laterally. Binocular cells are encountered in the cortical representation of the nasal 30--40 degrees of the visual field, and there is an expanded representation of the nasal field. Extrastriate visual cortex of the mouse, like that of other mammals, contains multiple representations of the visual field. The cytoarchitectonic region of cortex lateral and rostral to area 17, termed area 18a, contains at least two such representations. The more medial of these, which by convention we have called V2, is a narrow strip surrounding V1 on its lateral and rostral aspects; the vertical meridian lies along a portion of its common border with V1. The visual field representation in V2 is not a mirror image of that in V1; the representation of the horizontal meridian forms the lateral border of V2, and the visual field representation is split so that adjacent points on either side of the horizontal meridian are represented in nonadjacent parts of V2. The other visual field representation within area 18a, which we have termed V3, is a small but apparently complete representation that lies lateral to V2. The visual field representations medial to area 17 correspond to cytoarchitectonic area 18b. Area 18b contains two representations of the temporal visual field that we have labeled Vm-r and Vm-c, and contains little or no representation of the most nasal aspect of the field.

Animals↗
PubMed1980

Regional variation in the representation of the visual field in the visual cortex of the Siamese cat.

In Siamese cats, many ganglion cell fibers from the temporal retina misproject to the contralateral hemisphere; as a result, each lateral geniculate nucleus contains an abnormally large representation of the ipsilateral visual field. The manner in which the visual cortex processes this aberrant visual information has been examined in several previous studies. In some Siamese cats, the region of the 17/18 border was found to contain an extensive, systematic map of the ipsilateral field, while in other animals no such map was found, and the 17/18 border appeared to represent the zero meridian of azimuth (as in normal cats). These results have led to the suggestion that there are two distinct types of Siamese cat ("Boston" and "Midwestern") which can be distinguished on the basis of cortical topography and the anatomical organization oif the geniculocortical pathway. In the present study, we have recorded from four Siamese cats in order to examine the visual field map in the region of the 17/18 border; in each cat we recorded at anterior coronal levels corresponding to the representation of the lower visual field, and also at more posterior levels near the horizontal meridian representation. In all of the animals we found that the anterior penetrations (corresponding to mean receptive field elevations inferior to -7 degrees) yielded 15-20 degrees of ipsilateral field representation at the 17/18 border; however, the posterior, horizontal meridian penetrations (with mean elevations from +1 degrees to -4 degrees) showed excursions of only about 5 degrees into the ipsilateral field. This large difference in the representation of azimuth was not due to rotation of the eyes during our recording sessions. The finding of appreciable differences in the amount of ipsilateral field represented at different anterior-posterior levels of the same animal might lead to the suggestion that there are not two distinct populations (or types) of Siamese cat with regard to the cortical map of the ipsilateral field. Rather, we raise the possibility that Siamese cats form one population in which there is a continuous variation in the extent of ipsilateral field represented in the cortex.

Animals↗
PubMed1984

Relationship between preferred orientation and receptive field position of neurons in extrastriate cortex (area 19) in the cat.

Orientation sensitivity is a characteristic of most retinal ganglion cells (Levick and Thibos, '82), most relay cells in the dorsal lateral geniculate nucleus (Vidyasagar and Urbas, '82), and most neurons in the visual cortex (Hubel and Wiesel, '62) in the cat. In the retina there is a systematic relationship between receptive field position (polar angle) and preferred orientation. Outside of the area centralis most retinal ganglion cells respond best to stimuli oriented radially, i.e., oriented parallel to the line connecting their receptive fields to the area centralis (Levick and Thibos, '82). This relationship is strongest along the horizontal meridian (the visual streak) and appears to reflect the innate, radial orientation of retinal ganglion cell dendritic fields (Leventhal and Schall, '83). A relationship between preferred orientation and polar angle also exists in cat striate cortex; outside of the area centralis representation most cells respond best to lines oriented radially. This relationship is strongest for S-type cells, the most orientation-selective cells, and cells in regions representing the horizontal meridian (Leventhal, '83). To determine if similar relationships exist in cat extrastriate cortex, the preferred orientations and receptive field positions of 226 neurons in area 19 were studied. We find that, as in area 17, most area 19 cells outside of the representation of the area centralis respond best to lines oriented radially; this relationship is strongest for the cells having the narrowest receptive fields and in regions subserving the horizontal meridian. Unlike in striate cortex, in area 19 the relationship between preferred orientation and polar angle is not dependent upon cell type (S or C) or to the degree of orientation sensitivity exhibited. Also, in area 19, but not in area 17, the relationship between preferred orientation and polar angle fails for the cells having the widest receptive fields.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Ventral posterior visual area of the macaque: visual topography and areal boundaries.

Using both physiological and anatomical techniques, we have studied the topographic organization of extrastriate visual cortex on the ventral surface of the occipital lobe in macaque monkeys. Our results show that a topographically organized representation of the superior contralateral quadrant of the visual field lies immediately anterior to the ventral half of V2. This area is organized in a mirror symmetric fashion to ventral V2: it shares a horizontal meridian representation with V2 and a representation of the superior vertical meridian forms its anterior border. A well-defined strip of callosal inputs runs along the vertical meridian representation, thereby providing a reliable anatomical marker for areal boundaries in ventral extrastriate cortex. We refer to this area as the ventral posterior area (VP) because it is, in all these respects, notably similar to VP in the owl monkey. Ventral V2 has strong reciprocal connections with VP, and the topography of the V2 projection agrees closely with the topography revealed in our physiological mapping experiments. The visual field representation in VP is strikingly anisotropic, with linear magnification factor being much larger along contours of constant polar angle than along contours of constant eccentricity.

Animals↗
PubMed1987

Topographic organization of the middle temporal visual area in the macaque monkey: representational biases and the relationship to callosal connections and myeloarchitectonic boundaries.

We have used physiological and anatomical techniques to address three general issues concerning the topographic organization of the middle temporal visual area (MT) of the macaque monkey. First, we carried out a quantitative analysis of irregularities and asymmetries in the visual representation in MT. This analysis revealed a striking overemphasis on a restricted portion of the visual field that runs obliquely through the inferior contralateral quadrant and largely avoids both the horizontal meridian and the inferior vertical meridian. This corresponds to the portion of the visual field that would be maximally stimulated during visually guided hand movements. Second, the physiologically determined topographic organization of MT was compared to the pattern of callosal inputs in the same hemisphere, which are known to be distributed irregularly within MT. Callosal inputs tended to be densest near the representation of the vertical meridian, but there were numerous exceptions to this trend. Thus, topographic irregularities account for only part of the irregularities in callosal inputs to MT. Finally, comparison of these data with previous reports shows a strong correlation between body weight and the average size of MT. The representation in myeloarchitectonically defined MT was found to include much of the visual periphery, although it is unclear from our data whether this representation is invariably complete.

Animals↗