Temporal visual cortex

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-... 

Figure 2. A. Distribution of the serotonin receptor, 5-HT2 subtype which binds the indoleamine hallucinogens, in human temporal cortex as indicated by the binding of radiolabelled ketanserin. While the receptor is relatively sparse in the hippocampal area and entorhinal cortex on the top right, it is concentrated in the temporal association cortex including the area concerned with visual association.

Visual cortex Frontal lobe Prefrontal cortex Olfactory bulb Prefrontal cortex Superior temporal gyrus Left middle temporal gyrus Left superior temporal gyrus... 

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... 

The visual cortex occupies the occipital and parts of the parietal and temporal lobes of the cerebral cortex. Like the entire cortex, it forms a highly folded structure, with a thickness of approximately 1.5 mm. It is surrounded by the cerebrospinal fluid, several layers of meninges- pia mater, arachnoid, dura, and the skull. 

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. 

Perception begins with topographic localization in the occipital cortex of retinal representations, and progresses to visual memories in the temporal cortex (Farah, 2000). Neuronal pathways connecting different parts of the visual cortex run in both directions. 

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],... 

The retina contains photoreceptors which are connected to the ganglion cells via neuronal circuits. The ganglion cells axons form the optical nerve. Besides the optical nerve, the visual pathway encloses the optic chiasm and the LGN (Lateral Geniculate Nucleus). The main processing unit for visual perception is the terminal of the optical path The visual cortex, which contains visual stimuli responsive cells performing the final formation of mental representations of the perceived scene (see Fig. 1). It shall be noted that the fibres of the inner (nasal) and outer (temporal) part of the retina of each eye are separated in the optic chiasm and conducted to the same terminal in the visual cortex. Thus, the left hemisphere processes the right visual field of both eyes, whereas the right hemisphere processes the left visual... 

The visual cortex receives the low-level pre-processed differential signals from the LGN and generates a mental representation of the currently viewed scene. The receptive fields of the visual cortex are much more complex and show neuronal sensitivities for depth and motion cues as well as for temporal progression. 

The temporal lobe is the inferior middle portion of the cerebral cortex of both hemispheres. The temporal lobes are involved in the analysis of visual and acoustic information and in memory formation. The hippocampus is part of the inner, medial side of the temporal lobes. 

Named for the bones of the cranium under which they lie, the lobes are conspicuously defined by prominent sulci of the cortex, which have a relatively constant position in human brains. Each lobe is specialized for different activities (see Figure 6.3). Located in the anterior portions of the hemispheres, the frontal lobes are responsible for voluntary motor activity, speaking ability, and higher intellectual activities. The parietal lobes, which are posterior to the frontal lobes, process and integrate sensory information. The occipital lobes, located in the posterior-most aspects of the cerebrum, process visual information, and the temporal lobes, located laterally, process auditory information. 

The thalamus is the gateway to cortical processing of all incoming sensory information, represented in Figure 2.1 by the three major systems somatosensory (S), auditory (A), and visual (V). Primary sensory cortices (SI, Al, VI) receive information from the appropriate input modules (sensory organ -I- thalamus). The association cortex integrates information from primary cortices, from subcortical structures, and from brain areas affiliated with memory to create an internal representation of the sensory information. The medial temporal lobe (i.e., hippocampus, amygdala) serves two major... 

The medial and caudal portions of the midbody of the CC contain interhemispheric projections from the auditory cortices, posterior cingulate, retrosplenial cortex, and insula, and somatosensory and visual cortices to a lesser extent. It also includes connections from the inferior parietal lobe to the contralateral superior temporal sulcus, cingulate, and parahippocampal gyrus (Pandya and Seltzer, 1986). Several of the regions with interhemispheric projections through the medial and caudal portions of the midbody of the CC are involved in the processing of emotional stimuli and various memory functions—core disturbances frequently observed in children with a history of early trauma. 

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