Visual shape discrimination in goldfish, modelled with the neural circuitry of optic tectum and torus longitudinalis.

There is no satisfactory neurally-based theory as to how vertebrates that lack a neocortex discriminate even simple geometric shapes. In fishes, an intact optic tectum is necessary for such discriminations, but physiological studies of it have found nothing like the hierarchically arranged feature detecting neurons of mammalian visual cortex. Here, a neural model attempts a solution by basing shape discrimination upon the responses of only those elementary detectors (e.

Holding visual attention for 400millionyears: A model of tectum and torus longitudinalis in teleost fishes.

Only ray-finned fishes possess a torus longitudinalis (TL), a paired, elongated body attached to the medial margins of the optic tectum. Its granule cells project large numbers of fine fibers running laterally over adjacent tectum, synapsing excitatorily on the spiny dendrites of pyramidal cells. Sustained TL activity is evoked visuotopically by dark stimuli; TL bursting is a corollary discharge of saccadic eye movements.

Acuity and contrast sensitivity of the bluegill sunfish and how they change during optic nerve regeneration.

Spatial vision was studied in the bluegill sunfish, Lepomis macrochirus (9.5-14 cm standard length) to assess the limitations imposed by the optics of the eye, the retinal receptor spacing and the retinotectal projection during regeneration. Examination of images formed by the dioptric elements of the eye showed that spatial frequencies up to 29 c/ degrees could be imaged on the retina.

Promoting healthy lifestyles in Ontario Family Health Networks.

Purpose: Primary health care reform presents new opportunities for registered dietitians (RDs) to contribute to health promotion and disease prevention in family practices. Since this is an emerging area of RD practice, a health promotion specialist was contracted to conduct a needs assessment and develop a plan for implementing nutrition-focused healthy lifestyle activities.

Methods: The needs assessment was conducted as part of an Ontario-based demonstration project in three Family Health Networks (FHNs).