We have studied the morphology and physiology of retinal ganglion cells of a short-wavelength-sensitive cone (SWS-cone) pathway in dichromatic and trichromatic New World anthropoids, the capuchin monkey (Cebus apella) and tufted-ear marmoset (Callithrix jacchus). In Old World anthropoids, in which males and females are both trichromats, blue-ON/yellow-OFF retinal ganglion cells have excitatory SWS-cone and inhibitory middle- and long-wavelength-sensitive (MWS- and LWS-) cone inputs, and have been anatomically identified as small-field bistratified ganglion cells (SB-cells) (Dacey & Lee, 1994). Among retinal ganglion cells of New World monkeys, we find SB-cells which have very similar morphology to such cells in macaque and human; for example, the inner dendritic tree is larger and denser than the outer dendritic tree. We also find blue-on retinal ganglion cells of the capuchin to have physiological responses strongly resembling such cells of the macaque monkey retina; for example, responses were more sustained, with a gentler low frequency roll-off than MC-cells, and no evidence of contrast gain control. There was no difference between dichromatic and trichromatic individuals. The results support the view that SWS-cone pathways are similarly organized in New and Old World primates, consistent with the hypothesis that these pathways form a phylogenetically ancient color system.

Although epilepsy surgery may be the best treatment option for patients with refractory TLE-MTS, our findings emphasize the importance of performing a detailed psychiatric examination as part of the pre-surgical evaluation protocol.

We performed a quantitative analysis of M and P cell mosaics of the common-marmoset retina. Ganglion cells were labeled retrogradely from optic nerve deposits of Biocytin. The labeling was visualized using horseradish peroxidase (HRP) histochemistry and 3-3'diaminobenzidine as chromogen. M and P cells were morphologically similar to those found in Old-and New-World primates. Measurements were performed on well-stained cells from 4 retinas of different animals. We analyzed separate mosaics for inner and outer M and P cells at increasing distances from the fovea (2.5-9 mm of eccentricity) to estimate cell density, proportion, and dendritic coverage. M cell density decreased towards the retinal periphery in all quadrants. M cell density was higher in the nasal quadrant than in other retinal regions at similar eccentricities, reaching about 740 cells/mm 2 at 2.5 mm of temporal eccentricity, and representing 8-14% of all ganglion cells. P cell density increased from peripheral to more central regions, reaching about 5540 cells/mm 2 at 2.5 mm of temporal eccentricity. P cells represented a smaller proportion of all ganglion cells in the nasal quadrant than in other quadrants, and their numbers increased towards central retinal regions. The M cell coverage factor ranged from 5 to 12 and the P cell coverage factor ranged from 1 to 3 in the nasal quadrant and from 5 to 12 in the other quadrants. These results show that central and peripheral retinal regions differ in terms of cell class proportions and dendritic coverage, and their properties do not result from simply scaling down cell density. Therefore, differences in functional properties between central and peripheral vision should take these distinct regional retinal characteristics into account.

No abstract

-We re p o rt two patients with central neurocytomas at an uncommon location in the brain. The first, a 58-year-old man presenting with signs and symptoms of increased intracranial pre s s u re, had a tumor located at the pineal region. The second, a 21-year-old woman with tumor in the aqueductal region had worsening migraine-like headaches and diplopia. Both patients had obstructive hydrocephalus treated by n e u roendoscopic third ventriculostomy and biopsy of the tumors. No additional treatment was done. We conclude that neurocytomas should be considered in the diff e rential diagnosis of tumors located in the pineal and aqueductal regions.KEY WORDS: central neurocytoma, aqueductal region, pineal region, third ventriculostomy. Localizações incomuns do neurocitoma central: relato de dois casosRESUMO -Relatamos dois pacientes com neurocitoma central com localização incomum no sistema nervoso central. O primeiro, 58 anos, masculino, apresentava sinais e sintomas de hipertensão intracraniana, tinha um tumor na região da pineal. O segundo, feminino, 21 anos, tinha um tumor na região do aqueduto de Sylvius e apresentava cefaléia migranosa pro g ressiva e diplopia. Ambos apresentavam hidro c efalia obstrutiva tratada com terceiroventriculostomia endoscópica e biópsia da lesão. Não foi feito tratamento adicional. Concluimos que os neurocitomas devem ser considerados no diagnóstico diferencial de tumores localizados na região da pineal e do aqueduto. We re p o rt two patients with central neuro c y t o m a s at uncommon locations in the brain. In one patient the tumor was located in the aqueductal region and in the other the tumor laid in the pineal region. PALAVRAS-CHAVE CASESCase 1 -A 58-year-old man presented with a one-year h i s t o ry of memory loss, gait disturbance and headache. N e u rologic examination showed ataxic gait and papilledema. Computerized tomography images showed a hyperdense mass at the pineal region, with small points of calcification and moderate enhancement after contrast agent. Neither cysts nor invasion of the ventricular walls were seen. Lateral and third ventricles were dilated and showed periventricular edema, characterizing obstructive hydro c e p h alus. FLAIR and post-gadolinium T1-weighted MR images (Fig 1) revealed a mass with heterogeneous signal and moderate enhancement after paramagnetic agent, without