| H fields | Three circumscript, myelin-rich regions of the subthalamus known as H fields (from Haubenfelder); 1) field H1, corresponding to the thalamic fasciculus, a horizontal fibre stratum at the junction of the subthalamus and the overlying thalamus, is composed of pallidothalamic and cerebellothalamic fibres (brachium conjunctivum) and is separated by the zona incerta from the more ventrally placed field H2; 2) field H2, formed by the lenticular fasciculus and arching over the dorsal border of the subthalamic nucleus, is composed largely of pallidothalamic fibres; 3) field H3 or prerubral field, is a large field of intermingling gray and white matter immediately rostral to the red nucleus, uniting fields H1 and H2 around the medial margin of the zona incerta; its gray matter forms the prerubral nucleus. See: lenticular loop. Synonym: campi foreli, tegmental fields of Forel. (05 Mar 2000) |
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| shear fields | <radiobiology> As used in plasma physics, this refers to magnetic fields having a rotational transform (or, alternatively, safety factor) that changes with radius (for example, in the stellarator concept, magnetic fields that increase in pitch with distance from the magnetic axis.) (09 Oct 1997) |
| tegmental fields of Forel | Three circumscript, myelin-rich regions of the subthalamus known as H fields (from Haubenfelder); 1) field H1, corresponding to the thalamic fasciculus, a horizontal fibre stratum at the junction of the subthalamus and the overlying thalamus, is composed of pallidothalamic and cerebellothalamic fibres (brachium conjunctivum) and is separated by the zona incerta from the more ventrally placed field H2; 2) field H2, formed by the lenticular fasciculus and arching over the dorsal border of the subthalamic nucleus, is composed largely of pallidothalamic fibres; 3) field H3 or prerubral field, is a large field of intermingling gray and white matter immediately rostral to the red nucleus, uniting fields H1 and H2 around the medial margin of the zona incerta; its gray matter forms the prerubral nucleus. See: lenticular loop. Synonym: campi foreli, tegmental fields of Forel. (05 Mar 2000) |
| electromagnetic fields | Fields representing the joint interplay of electric and magnetic forces. (12 Dec 1998) |
| fields of Forel | Three circumscript, myelin-rich regions of the subthalamus known as H fields (from Haubenfelder); 1) field H1, corresponding to the thalamic fasciculus, a horizontal fibre stratum at the junction of the subthalamus and the overlying thalamus, is composed of pallidothalamic and cerebellothalamic fibres (brachium conjunctivum) and is separated by the zona incerta from the more ventrally placed field H2; 2) field H2, formed by the lenticular fasciculus and arching over the dorsal border of the subthalamic nucleus, is composed largely of pallidothalamic fibres; 3) field H3 or prerubral field, is a large field of intermingling gray and white matter immediately rostral to the red nucleus, uniting fields H1 and H2 around the medial margin of the zona incerta; its gray matter forms the prerubral nucleus. See: lenticular loop. Synonym: campi foreli, tegmental fields of Forel. (05 Mar 2000) |
| accessory visual apparatus | The eyelids, with lashes and eyebrows, lacrimal apparatus, conjunctival sac, and extrinsic muscles of the eyeball. Synonym: organa oculi accessoria, accessory organs, accessory visual apparatus, adnexa oculi, appendages of eye. (05 Mar 2000) |
| Bender Visual Motor Gestalt test | <psychology> A psychological test used by neurologists and clinical psychologists to measure a person's ability to visually copy a set of geometric designs. It consists of nine geometric designs on cards. The subject is asked to redraw them from memory after each one is presented individually. It is useful for measuring visuospatial and visuomotor coordination to detect brain damage. Synonym: Bender Visual Motor Gestalt test. (14 Aug 2000) |
| Broca's visual plane | A plane drawn through the visual axes of each eye. (05 Mar 2000) |
| receptor, visual | The layer of rods and cones, the visual cells, of the retina. (12 Dec 1998) |
| pattern recognition, visual | Visually perceived characters, shapes, displays, or designs. (12 Dec 1998) |
| visual | Pertaining to vision or sight. Origin: L. Visualis, from videre = to see (18 Nov 1997) |
| visual acuity | <microscopy> The ability to detect fine details or small distances with the eye. Visual acuity can vary substantially depending on the definition used and method of measurement chosen. Under favourable conditions, the resolution of the human eye or ability to distinguish the twoness of adjoining lines, is about I minute of arc while the threshold delectability, or the detection of misaligned steps in a line (which is also a form of visual acuity), can be as low as a fraction of a second of arc. (05 Aug 1998) |
| visual agnosia | The inability to recognise objects by sight; usually caused by bilateral parieto-occipital lesions. Synonym: optic agnosia. (05 Mar 2000) |
| visual angle | The angle formed at the retina by the meeting of lines drawn from the periphery of the object seen. (05 Mar 2000) |
| visual aphasia | <neurology> Loss of the ability to understand printed words or sentences (27 Sep 1997) |