John R. Economides

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Retinal spikes impinging on relay neurons in the lateral geniculate nucleus (LGN) generate synaptic potentials, which sometimes produce spikes sent to visual cortex. We examined how signal transmission is regulated in the macaque LGN by recording the retinal input to a single LGN neuron while stimulating the receptive field center with a naturalistic(More)
Many neurophysiological experiments involving monkeys require that the head be stabilized while the animal performs a task. Often a post is attached to the skull to accomplish this goal, using a headcap formed from dental acrylic. We describe a new headpost, developed by refinement of several prototypes, and supply an AutoCAD file to aid in machine shop(More)
We recorded from single units in the pretectal nucleus of the optic tract (NOT) of the nonhuman primate. Specifically, we examined units that are modulated during smooth tracking of a small laser spot against a dark background. We used a nonlinear optimization procedure to determine whether the unit responses of these parafoveal cells are better described(More)
The abundant concentration of cytochrome oxidase in patches or blobs of primate striate cortex has never been explained. Patches are thought to contain unoriented, color-opponent neurons. Lacking orientation selectivity, these cells might endow patches with high metabolic activity because they respond to all contours in visual scenes. To test this idea, we(More)
Neurophysiological recording in alert monkeys requires the creation of a permanent aperture in the skull for repeated insertion of microelectrodes. Most laboratories use polymethyl methacrylate to attach a recording chamber over the skull opening. Here, we describe a titanium chamber that fastens to the skull with screws, using no polymethyl methacrylate.(More)
The vascular supply to layers and columns was compared in macaque primary visual cortex (V1) by labeling red blood cells via their endogenous peroxidase activity. Alternate sections were processed for cytochrome oxidase to reveal "patches" or "blobs," which anchor the interdigitated column systems of striate cortex. More densely populated cell layers(More)
The dorsolateral pontine nucleus (DLPN) and nucleus reticularis tegmenti pontis (NRTP) comprise obligatory links in the cortico-ponto-cerebellar system supporting smooth pursuit eye movements. We examined the response properties of DLPN and rNRTP neurons during step-ramp smooth pursuit of a small target moving across a dark background. Our(More)
To provide an animal model of human exotropia, a free tenotomy of the medial recti was performed in two infant macaques. When the animals were old enough to record eye movements with video eye trackers, we measured their ductions, ocular alignment, comitance, smooth pursuit, fixation preference, and gaze stability. Partial recovery of adduction occurred in(More)
Misalignment of the eyes can lead to double vision and visual confusion. However, these sensations are rare when strabismus is acquired early in life, because the extra image is suppressed. To explore the mechanism of perceptual suppression in strabismus, the visual fields were mapped binocularly in 14 human subjects with exotropia. Subjects wore red/blue(More)
When an eye becomes deviated in early childhood, a person does not experience double vision, although the globes are aimed at different targets. The extra image is prevented from reaching perception in subjects with alternating exotropia by suppression of each eye's peripheral temporal retina. To test the impact of visual suppression on neuronal activity in(More)