1/39. Non-conscious recognition of affect in the absence of striate cortex.functional neuroimaging experiments have shown that recognition of emotional expressions does not depend on awareness of visual stimuli and that unseen fear stimuli can activate the amygdala via a colliculopulvinar pathway. Perception of emotional expressions in the absence of awareness in normal subjects has some similarities with the unconscious recognition of visual stimuli which is well documented in patients with striate cortex lesions (blindsight). Presumably in these patients residual vision engages alternative extra-striate routes such as the superior colliculus and pulvinar. Against this background, we conjectured that a blindsight subject (GY) might recognize facial expressions presented in his blind field. The present study now provides direct evidence for this claim.- - - - - - - - - - ranking = 1keywords = motion (Clic here for more details about this article) |
2/39. blindness after liver transplant.A 58-year-old woman developed a generalized seizure 12 days after undergoing liver transplantation and awakened with persistent hand motions vision binocularly. cyclosporine levels were normal and blood pressure was only mildly elevated. The ophthalmic and neurologic examinations were otherwise normal. brain MRI revealed bilateral parieto-occipital white matter signal abnormalities consistent with vasogenic edema. The cyclosporine was abruptly replaced with tacrolimus and the patient recovered normal vision within 48 hours. A subsequent brain MRI taken 30 days later showed that the patient had reverted to normal. This is an example of posterior leukoencephalopathy owing to cyclosporine toxicity. It points out that visual loss may be an isolated or most prominent clinical manifestation, cyclosporine and blood pressure levels may be normal, deficits are reversible if cyclosporine is promptly discontinued, and tacrolimus, a similar immunosuppressive agent, may be a safe substitute.- - - - - - - - - - ranking = 0.5keywords = motion (Clic here for more details about this article) |
3/39. Encephalopathy and neuropathy in end-stage liver disease before and after liver transplantation.The nervous system involvement of 8 patients with end-stage liver disease was evaluated by means of clinical neurological, neuropsychological, neurophysiological and neuroradiological investigation before and 6-12 months after a successful liver transplantation. Preoperatively, all subjects (7 women, 1 man; mean age 40 years, range 30-54 years) exhibited decreased muscle strength and 2 patients manifested clinical signs of polyneuropathy. In neuropsychological tests, slight visuoconstructive apraxia, and disturbances of verbal memory and cognitive function were observed. magnetic resonance imaging (MRI) revealed cerebral lesions in two patients. After transplantation, muscle strength reverted to normal in all patients, polyneuropathy improved and in all but 2 patients recovery of neuropsychological functioning was observed. Clinical signs of encephalopathy had disappeared. All patients were emotionally better adjusted after transplantation. Four subjects showed new, albeit mild changes in neurophysiological and neuropsychological tests postoperatively. We conclude that the majority of neurological impairment disappeared after liver transplantation. We want to stress that evaluation of neurological sequelae of liver transplantation needs to be based on assessments both before and after liver transplantation.- - - - - - - - - - ranking = 0.5keywords = motion (Clic here for more details about this article) |
4/39. Attentional capture by colour and motion in cerebral achromatopsia.Cerebral achromatopsia is a rare condition in which damage to the ventromedial occipital area of the cortex results in the loss of colour experience. Nevertheless, cortically colour-blind patients can still use wavelength variation to perceive form and motion. In a series of six experiments we examined whether colour could also direct exogenous attention in an achromatopsic observer. We employed the colour singleton paradigm, the phi motion effect, and the correspondence process to assess attentional modulation. Although colour singletons failed to capture attention, a motion signal, based solely on chromatic information, was able to direct attention in the patient. We then show that the effect is abolished when the chromatic contours of stimuli are masked with simultaneous luminance contrast. We argue that the motion effect is dependent on chromatic contrast mediated via intact colour-opponent mechanisms. The results are taken as further evidence for the processing of wavelength variation in achromatopsia despite the absence of colour experience.- - - - - - - - - - ranking = 4keywords = motion (Clic here for more details about this article) |
5/39. Areas MT/V5 and their transcallosal connectivity in cortical dysplasia by fMRI.A patient with unilateral focal cortical dysplasia with a significant impairment of visual motion perception within the contralateral hemifield was examined with fMRI. During hemifield visual motion stimulation primary visual cortex areas were activated contralaterally and deactivated ipsilaterally to the stimulated hemifield. Transcallosal visuo-visual interaction was further evident as bilateral activation in temporo-occipital areas that best correspond to the motion sensitive areas MT/V5. MT/V5 was displaced anteriorly, superiorly, and medially within the dysplastic hemisphere and separated into two distinct activation clusters. During visual motion stimulation the parieto-insular vestibular cortex showed signal decreases that agree with the concept of inhibitory visuo-vestibular interaction. Thus, fMRI is a suitable tool for detecting preserved function and transcallosal connections in patients with focal cortical dysplasia.- - - - - - - - - - ranking = 2keywords = motion (Clic here for more details about this article) |
6/39. Unusual case of kluver-bucy syndrome in a Chinese boy.Following an encephalopathic illness, a 13-year-old Chinese boy had a partial form of kluver-bucy syndrome with emotional disturbance, recent memory loss, hypersexuality, and polyphagia. Other unusual features included narcolepsy, polydipsia, and polyuria. Virologic studies failed to incriminate the etiologic agent, including herpes simplex virus. brain biopsy of the frontal lobe demonstrated Alzheimer type II astrocytosis.- - - - - - - - - - ranking = 0.5keywords = motion (Clic here for more details about this article) |
7/39. Disturbance of movement vision after bilateral posterior brain damage. Further evidence and follow up observations.In 1983 we reported in this Journal a patient who suffered a disturbance of movement vision in a relatively pure form. This uncommon cerebral visual deficit resulted as a consequence of bilateral brain damage affecting the lateral temporo-occipital cortex and the underlying white matter. In this paper we present further evidence for the selectivity of the movement vision deficit. Furthermore, follow-up examination did not reveal any significant change which indicates that the disorder appears irreversible. magnetic resonance imaging (MRI) shows bilateral lesions involving the upper (cranial) part of the occipital gyri and the adjacent portion of the middle temporal gyri, with the main focus of damage in the upper (cranial) banks of the anterior occipital sulcus. In addition, cortico-cortical fibre pathways interconnecting occipital, temporal and parietal 'visual' areas are also affected bilaterally. The selectivity of the movement vision deficit and the irreversibility of the disorder strongly support the idea that movement vision is a separate function which is subserved by a visual pathway specialized for the processing of visual motion.- - - - - - - - - - ranking = 0.5keywords = motion (Clic here for more details about this article) |
8/39. diffusion-weighted MR imaging of the brain: value of differentiating between extraaxial cysts and epidermoid tumors.This study demonstrates the use of diffusion-weighted MR imaging in improving the specificity of the diagnosis of extraaxial brain tumors. Three surgically proved lesions (one arachnoid cyst and two epidermoid tumors) and two nonsurgically proved lesions (arachnoid and ependymal cysts) were evaluated with T1- and T2-weighted spin-echo studies followed by intravoxel incoherent motion (IVIM) MR imaging. The IVIM images of the lesions were displayed as an apparent diffusion coefficient (ADC) image obtained at 0.65 G/cm (maximum gradient b value = 100 sec/mm2) and compared with external oil and water phantoms. The ADC of arachnoid cysts was similar to stationary water whereas the ADC of epidermoid tumors was similar to brain parenchyma, indicating the solid nature and the slower diffusion rate of the epidermoid tumors. Cisternal CSF demonstrated uniformly high ADC, primarily because of bulk flow, which enhanced image contrast. Improved delineation of postsurgical changes was also possible. Our preliminary results show that diffusion-weighted MR imaging can be useful in distinguishing between arachnoid cysts and epidermoid tumors.- - - - - - - - - - ranking = 0.5keywords = motion (Clic here for more details about this article) |
9/39. diffusion-weighted MR imaging of the brain: value of differentiating between extraaxial cysts and epidermoid tumors.This study demonstrates the use of diffusion-weighted MR imaging in improving the specificity of the diagnosis of extraaxial brain tumors. Three surgically proved lesions (one arachnoid cyst and two epidermoid tumors) and two nonsurgically proved lesions (arachnoid and ependymal cysts) were evaluated with T1- and T2-weighted spin-echo studies followed by intravoxel incoherent motion (IVIM) MR imaging. The IVIM images of the lesions were displayed as an apparent diffusion coefficient (ADC) image obtained at 0.65 G/cm (maximum gradient b value = 100 sec/mm2) and compared with external oil and water phantoms. The ADC of arachnoid cysts was similar to stationary water whereas the ADC of epidermoid tumors was similar to brain parenchyma, indicating the solid nature and the slower diffusion rate of the epidermoid tumors. Cisternal CSF demonstrated uniformly high ADC, primarily because of bulk flow, which enhanced image contrast. Improved delineation of postsurgical changes was also possible. Our preliminary results show that diffusion-weighted MR imaging can be useful in distinguishing between arachnoid cysts and epidermoid tumors.- - - - - - - - - - ranking = 0.5keywords = motion (Clic here for more details about this article) |
10/39. Furtive incursions into bicameral minds. Integrative and coordinating role of subcortical structures.Section of forebrain commissures results in a pervasive disconnection syndrome characterized by the incapacity of the two cerebral hemispheres to exchange their respective information content. Yet commissurotomized patients are capable of unified behaviour in their daily activities and, in laboratory situations, are able to produce a single response as a function of the information received by both hemispheres. This study further investigated the nature of the information that can be communicated between the disconnected hemispheres in 3 commissurotomized patients. The first part comprised 7 experiments in which the patients were required to compare 2 digits simultaneously, 1 projected to each hemisphere. While the stimulus and experimental conditions were the same across experiments, the information content on which to base the comparison was manipulated. The level of performance varied as a function of the information content, such that the patients were unable to decide whether the 2 digits were the same or different, performed better when required to compare the digits in terms of their odd-even category, and were highly accurate at deciding which digit was the higher. In addition, when instructed to focus on the numerical value of the digits to decide whether the 2 digits were the same or different, they performed significantly above chance. In the second part, they were requested to report verbally information about emotional faces and familiar faces projected to the right hemisphere. While they were unable to access the visual characteristics and the identity of the faces, they could provide various correct items of semantic information about the individuals. Taken together, the results indicate that the disconnection syndrome is limited to specific categories of information and does not extend to all the knowledge that may be derived from a given object. They also suggest that subcortical structures do not serve simply as pathways linking the two hemispheres but play an essential coordinating role in the integration of hemisphere activity.- - - - - - - - - - ranking = 0.5keywords = motion (Clic here for more details about this article) |
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