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S M Zeki

Publications and source records attributed to S M Zeki.

32 records · Page 2Linked to original sources
PubMed1974

Functional organization of a visual area in the posterior bank of the superior temporal sulcus of the rhesus monkey.

1. Anatomical studies have shown the cortex of the posterior bank of the superior temporal sulcus to receive a projection from visual cortical areas, including areas 17, 18 and 19. In this paper the response of single neurones in this area to simple visual stimulation is reported. Ten monkeys were studied.2. A clear but relatively crude topographic representation of the visual field was found. There was a large variation in the size of the receptive fields of individual cells, even in a single penetration. Some cells, with the central parts of their receptive fields located from between 1 and 5 degrees from the centre of gaze had receptive fields averaging about 10 degrees x 10 degrees or even larger. Other cells with central receptive fields had much smaller field sizes.3. Two main types of neurones were encountered, with subdivisions within each type. The first type responded to movement irrespective of form. These could be subdivided into neurones which responded to movement in any direction within the receptive field and neurones which responded to movement in one direction only (directionally selective neurones). Another type of cell was responsive to both contour and movement, much like the complex and lower order hypercomplex cells. Almost all such neurones were directionally selective.4. In oblique penetrations through this cortical region, there tended frequently to be an orderly shift in preferred directions of motion, thus suggesting the possibility of a columnar organization for movement.5. Combined anatomical (degeneration) and electrophysiological experiments showed that these types of neurones are found in those regions of the posterior bank of the superior temporal sulcus receiving a direct projection from area 17.

Animals↗
PubMed1974

Cells responding to changing image size and disparity in the cortex of the rhesus monkey.

1. The cells of the cortex of the posterior bank of the superior temporal sulcus of the monkey appear to be specialized to signal motion in the visual field. In this paper, cells in this cortical area capable of signalling motion towards or away from the animal are described.2. Two such types of cell were encountered. One type, the opposed movement complex and opposed movement hypercomplex cells, responded to two edges at a given orientation moving towards or away from each other within the receptive fields. These cells were driven either monocularly or binocularly, but when binocularly driven the cells responded in an identical manner to stimulation of each eye, thus suggesting that such cells must receive a double, and opposed, input from each eye. The other type of cell, always binocularly driven, responded to movement in opposite directions on the two retinas, thus suggesting that such cells must receive diametrically opposite connexions from the two eyes.3. Long penetrations made to study the manner in which such cells were grouped together in the cortex revealed that they were arranged in small groups or clusters, separated from each other by the common directionally selective cells so prominently present in this area. Thus, cells with one type of wiring mechanism were separated from each other by cells receiving another, and more common, type of anatomical wiring.

Animals↗
PubMedDate not supplied

Neuroradiological features of patients with optic nerve hypoplasia.

Optic nerve hypoplasia (ONH) is associated with a wide range of neurological and endocrine disorders. A series of 21 patients is reported. This comprised 17 with ONH in association with manifest neurological and endocrine disturbance, 3 who were blind but who were otherwise normal, and 1 with bilateral impaired visual acuity only. All patients underwent neuroradiological and detailed ophthalmic assessment. A wide range of abnormalities was observed. The most common findings were absent septum pellucidum, hydrocephaly, and porencephaly. Evidence of hypothalamic/pituitary hormone deficiency was present in nine patients, six of whom had demonstrable intracranial radiological abnormalities. All patients except one had bilateral optic nerve hypoplasia. Most patients had poor visual acuities and nystagmus. Astigmatism was also common. Two conditions which have not previously been reported in association with optic nerve hypoplasia were found: an intracranial arachnoid cyst and an intracranial epidermoid cyst.

Abnormalities, Multiple↗