Primary visual area

Certain areas in the primary visual area (PVA) were more intensely activated when the subjects imagined a scene, compared with when they actually viewed the scene. 

Glucose utilization (jjimoI/100 g/min). The administration of muscimol (1.5 mg/kg) and THIP (10 mg/kg) effected reductions in glucose use of a similar magnitude in each primary visual area except the superficial layer of the superior colliculus. 

The one region of the CNS in which glucose utilization responded in a different manner to muscimol than to THIP was the superficial layer of the superior colliculus, and the response in this area contrasted with that in other primary visual areas and the deeper layers of the superior colliculus, which responded in a similar manner to both agents (Table 7, Fig. 27) (Kelly and McCulloch, 1981 >). Whether the differential response in the superficial layer is a consequence of the abundance of intrinsic benzodiazepine receptors in this lamina (Young and Kuhar, 1980), or whether it is the result of alterations in the retinotectal pathway, remains undetermined. 

The inferior longitudinal fasciculus follows the ventral stream and involves a pathway conjoining the primary visual cortex with the inferior temporal cortex. It is believed to be involved in object identification by integrating feature analysis with object discrimination. Single cell recordings from area V4 of the extrastriate cortex during covert orientation of attention reveal an in-... 

List of Abbreviations ISI, interstimulus interval LGN, lateral geniculate nucleus M, magnocellular MST, medial superior temporal area MT, medial temporal area NMDA, N-methyl-D-aspartate P, parvocellular ssVEP, steady-state visual evoked potential TE, temporal lobe TEO, temporal occipital area tVEP, transient visual evoked potential YEP, visual evoked potential VI, primary visual cortex... 

VIB primary visual cortex, binocular area 42-57,85-88 VIM primary visual cortex, monocular area 42-57,81-86 V2L secondary visual cortex, lateral area 39-57, 86-89, 113-116 V2ML secondary visual cortex, mediolateral area 38-47, 84-86 V2MM secondary visual cortex, mediomedial area 37-53, 81-83 VA ventral anterior thalamic nucleus 25-28, 82-83, 101-105 vaf ventral amygdalofugal pathway 28 VC ventral cochlear nucleus 96... 

Anterior Cingulate Gyrus. C Frontal Lobe. D Parietal Lobe. E occipital Lobe (primary visual cortex), f Temporal Lobe most of this area of the cortex is on the outside of the far side of the brain, hidden in this view. G Cerebellum. H Thalamus. Encircling the Thalamus are the Hippocampus, the Amygdala, the Basal Ganglia and other parts of the limbic system. l Pons. 3 Midbrain, area in which are found the various brain stem nuclei including the Raphe Nuclei, the Locus Coeruleus, the Substantia Nigra, etc. K Medulla. 

List of Abbreviations SI, primary somatosensory cortex SII, second somatosensory area PV, parietal ventral area SA, slowly adapting RA, rapidly adapting PC, pacinian VPL, ventral posterior lateral VPI, ventroposterior inferior CCD, charge coupled device VI, primary visual cortex V2, second visual area V4, fourth visual area IT, inferotemporal cortex... 

Fig. 3 Diagrammatic representation of the pyramidal cell module in rat primary visual cortex, area 17. The cortical layers are indicated on the left and the number of neurons in each layer contributing to the module is given on the right. After Peters (1993)...

The LGN contains approximately 1.5 million cells. By comparison, the primary visual cortex, or striate cortex, which receives the visual information from the LGN, contains 200 million cells. It consists of a thin (2-mm) layer of gray matter (neuronal cell bodies) over a thicker collection of white matter (myelinated axons) and occupies a few square inches of the occipital lobes. The primary visual cortex has been called area 17 from the days when the cortical areas were first differentiated by their cytoarchitectonics (the microscopic architecture of their layered neurons). In modern terminology, the primary visual cortex is often called visual area 1, or simply VI. 

The primary visual cortex contains six layers, numbered 1 through 6. Distinct functional and anatomic types of cells are found in each layer. Layer 4 contains neurons that receive information Ifom the LGN. Beyond the initial synapses, cells demonstrate progressively more complex responses. The outputs of VI project to an area known as visual area 2 (V2), which surrounds VI, and to higher visual areas in the occipital, temporal, and parietal lobes as well as to the superior colliculus. VI also sends reentrant projections back to the LGN. Reentrant projections are present at almost every level of the visual system [Edelman, 1978 FeUeman and Essen, 1991],... 

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