Influence of temporal lobe lesions on photic-evoked responses in occipital visual areas.

In 20 patients with temporal lobe lesions and 10 controls, the averaged photic-evoked responses (APERs) and their dispersion pattern (DP) were investigated in inion-vertex-lead and bilaterally in inion-parietal leads (I-P3 and I-P4). The patients with temporal lobe lesions, regardless of lesion location in temporal areas, displayed either absence of APER (the whole APER or only the initial components) or a latency increase without amplitude changes. The DP was generally abnormal. The role of the temporal lobe in the organization of APER in visual areas is discussed.     

Morphometrical considerations on occipital condyles

From the study of the surface area of the occipital condyles and of skull volume resulted that the surface area is not proportional to skull volume. The measurements were conducted on a collection of 424 male and 317 female skulls. It was observed that the two condyles are rarely symmetrical and that also flat condyles appear. Bi-partitioned condyles can be divided into three types: roof-like bipartitions, simple bipartitions and total bipartitions.     

Prognostic value of visual evoked potentials in occipital blindness following basilar artery occlusion.

Three patients suffering from sudden occipital blindness following basilar artery occlusion underwent electroretinography and visual evoked potential (VEP) examinations. The VEPs performed early in those blind patients and repeated later seem to be of prognostic value. Responses of normal shape and amplitude after monocular and binocular stimulation were followed by complete recovery of vision. Unequal and subnormal VEPs obtained following monocular stimulation, and even smaller responses reached after binocular stimulation, accompanied permanent unilateral occipital damage resulting in homonymous hemianopsia. Lack of VEP was proved to be a preceding sign of permanent blindness.     

枕外隆凸点的定位

枕外隆凸点的定位张银运（中国科学院古脊椎动物与古人类研究所．北京１０００４４）枕外隆凸点（Ｉｈｉｏｎ）是人类头骨上的常用测点;无论是对人类头骨化石作鉴定,或是对现代人类头骨作测量,多先要定出该测点在枕骨上的确切位置。但枕外隆凸点的定义却有好几个．Ｂｒ...     

Androgen receptor immunoreactivity in rat occipital cortex after callosotomy

Gonadal steroidogenesis can be influenced by direct neural links between the central nervous system and the gonads. It is known that androgen receptor (AR) is expressed in many areas of the rat brain involved in neuroendocrine control of reproduction,such as the cerebral cortex.It has been recently shown that the occipital cortex exerts an inhibitory effect on testicular stereoidogenesis by a pituitary-independent neural mechanism. Moreover, the complete transection of the corpus callosum leads to an increase in testosterone (T) secretion of hemigonadectomized rats. The present study was undertaken to analyze the possible corticocortical influences regulating male reproductive activities. Adult male Wistar rats were divided into 4 groups: 1) intact animals as control; 2) rats undergoing sham callosotomy; 3) posterior callosotomy; 4) gonadectomy and posterior callosotomy. Western blot analysis showed no remarkable variations in cortical AR expression in any of the groups except in group I where a significant decrease in AR levels was found. Similarly, both immunocytochemical study and cell count estimation showed a lower AR immunoreactivity in occipital cortex of callosotomized rats than in other groups. In addition, there was no difference in serum T and LH concentration between sham-callosotomized and callosotomized rats. In conclusion, our results showthat posterior callosotomy led to a reduction in AR in the right occipital cortex suggesting a putative inhibiting effect of the contralateral cortical area.     

Feedback contributions to visual awareness in human occipital cortex

It has traditionally been assumed that processing within the visual system proceeds in a bottom-up, feedforward manner from retina to higher cortical areas. In addition to feedforward processing, it is now clear that there are also important contributions to sensory encoding that rely upon top-down, feedback (reentrant) projections from higher visual areas to lower ones. By utilizing transcranial magnetic stimulation (TMS) in a metacontrast masking paradigm, we addressed whether feedback processes in early visual cortex play a role in visual awareness. We show that TMS of visual cortex, when timed to produce visual suppression of an annulus serving as a metacontrast mask, induces recovery of an otherwise imperceptible disk. In addition to producing disk recovery, TMS suppression of an annulus was greater when a disk preceded it than when an annulus was presented alone. This latter result suggests that there are effects of the disk on the perceptibility of the subsequent mask that are additive and are revealed with TMS of the visual cortex. These results demonstrate spatial and temporal interactions of conscious vision in visual cortex and suggest that a prior visual stimulus can influence subsequent perception at early stages of visual encoding via feedback projections.     

Relevance of the lesser occipital nerve in facial rejuvenation surgery

Nerve injuries are possible during facial rejuvenation surgery. The great auricular nerve has been studied; however, little is known about the lesser occipital nerve and its relevance in facial rejuvenation surgery. To understand the importance of the lesser occipital nerve in a face lift procedure, the specific anatomy of the nerve was studied in the laboratory in 19 hemifaces, with additional nerve observations in the operating room. The course of the lesser occipital nerve, its branches, and the relationship with the surrounding structures were evaluated and recorded. The great auricular nerve was also dissected to compare the two nerve territories. In the majority of the dissections, the lesser occipital nerve supplied the superior ear and the mastoid area, whereas the great auricular nerve innervated the inferior ear and a portion of the preauricular area. The nerves, however, were variable in size and distribution. Five lesser occipital nerves provided the dominant supply to the ear, compensating for a small great auricular nerve contribution. Therefore, injury to the lesser occipital nerve can result in a major sensory deficit of the ear. We also found the lesser occipital nerve to have a subcutaneous course at a proximal and variable level. These nerve branches can be superficial, and therefore postauricular flap dissection can injure the nerve if the flap is dissected at the fascial level. We therefore suggest that the dissection be at a more superficial level to avoid nerve injury. And finally, if SMAS/platysma suspension sutures are placed, we suggest these be done in a vertical-oblique direction along the course of the lesser occipital nerve, because this should minimize the possibility of trapping terminal branches.     

The timing of spheno‐occipital fusion in hominoids

The degree of spheno‐occipital fusion has been used to assign a relative age to dentally mature hominoid cranial specimens. However, a recent study of captive individuals (Poe: Am J Phys Anthropol 144 (2011) 162–165) concluded that fusion of the spheno‐occipital suture in great ape taxa is of little utility for aging dentally mature individuals. In this contribution, I use dentally mature samples of extant hominoid taxa (Homo sapiens, Pan troglodytes schweinfurthii, Gorilla gorilla gorilla, Pongo pygmaeus pygmaeus and Hylobates lar) to investigate a) the temporal relationship between spheno‐occipital fusion and dental maturity, b) whether there is an association between the degree of spheno‐occipital fusion and relative age, c) whether there are differences in relative timing of spheno‐occipital fusion between taxa, and d) whether there are sex differences in the relative timing of spheno‐occipital fusion. Results suggest that a) a substantial proportion of dentally mature wild‐shot chimpanzee, gorilla and orang‐utans have unfused or partially fused spheno‐occipital synchondoses, b) there is an association between the degree of spheno‐occipital fusion and age, c) there are interspecific differences in the timing of spheno‐occipital fusion, and d) there are significant sex differences in spheno‐occipital fusion in chimpanzees, orang‐utans and gibbons. Thus, contrary to previous work, degree of spheno‐occipital fusion is a potentially useful indicator of relative maturity, especially in great ape taxa. Am J Phys Anthropol 156:135–140, 2015. © 2014 Wiley Periodicals, Inc.     

Factors affecting neurite outgrowth of occipital cortical explants

The effects of various substrata including laminin, collagen gel, collagen I, and human amniotic basement membrane on neurite outgrowth of occipital cortical and diencephalic explants were studied. The results showed that the extent and pattern of growing neurites of cortical explants varied considerably depending on the substrata used. While an elaborated network of growing neurites was observed when cortical explants were plated on laminin, the most extensive neurite outgrowth was observed when collagen gel was used as the substratum. In contrast, diencephalic explants did not grow on most of the substrata. The significance of the findings are discussed.     

Contrast invariance in the human lateral occipital complex depends on attention

The human visual system has a remarkable ability to successfully operate under a variety of challenging viewing conditions. For example, our object-recognition capabilities are largely unaffected by low-contrast (e.g., foggy) environments. The basis for this ability appears to be reflected in the neural responses in higher cortical visual areas that have been characterized as being invariant to changes in luminance contrast: neurons in these areas respond nearly equally to low-contrast as compared to high-contrast stimuli. This response pattern is fundamentally different than that observed in earlier visual areas such as primary visual cortex (V1), which is highly dependent on contrast. How this invariance is achieved in higher visual areas is largely unknown. We hypothesized that directed spatial attention is an important prerequisite of the contrast-invariant responses in higher visual areas and tested this with functional MRI (fMRI) while subjects directed their attention either toward or away from contrast-varying shape stimuli. We found that in the lateral occipital complex (LOC), a visual area important for processing shape information, attention changes the form of the contrast response function (CRF). By directing attention away from the shape stimuli, the CRF in the LOC was similar to that measured in V1. We describe a number of mechanisms that could account for this important function of attention.     

Neural response to perception of volume in the lateral occipital complex

Projection of a 3D scene onto the 2D retina necessarily entails a loss of information, yet perceivers experience a world populated with volumetric objects. Using simultaneous behavioral and neural (fMRI) measures, we identify neural bases of volume perception. Neural activity in the lateral occipital cortex increased with presentation of 3D volumes relative to presentation of 2D shapes. Neural activity also modulated with perceived volume, independent of image information. When behavioral responses indicated that observers saw ambiguous images as 3D volumes, neural response increased; when behavioral data revealed a 2D interpretation, neural response waned. Crucially, the physical stimulus was identical under both interpretations; only the percept of volume can account for the increased neural activity.     

Differential roles for parietal and occipital cortices in visual working memory

Visual working memory (VWM) is known as a highly capacity-limited cognitive system that can hold 3-4 items. Recent studies have demonstrated that activity in the intraparietal sulcus (IPS) and occipital cortices correlates with the number of representations held in VWM. However, differences among those regions are poorly understood, particularly when task-irrelevant items are to be ignored. The present fMRI-based study investigated whether memory load-sensitive regions such as the IPS and occipital cortices respond differently to task-relevant information. Using a change detection task in which participants are required to remember pre-specified targets, here we show that while the IPS exhibited comparable responses to both targets and distractors, the dorsal occipital cortex manifested significantly weaker responses to an array containing distractors than to an array containing only targets, despite that the number of objects presented was the same for the two arrays. These results suggest that parietal and occipital cortices engage differently in distractor processing and that the dorsal occipital, rather than parietal, activity appears to reflect output of stimulus filtering and selection based on behavioral relevance.