articlesThe optic flow 1 that is generated when a person moves through the environment can be locally decomposed into several basic components, including radial, circular, translation and sheer motion 2,3 . Neurons in the dorsal portion of the medial superior temporal cortex (MSTd) of macaque monkeys respond selectively to these components, alone or in combination [4][5][6][7] . Microstimulation can influence the direction of heading of a behaving monkey 8 , which demonstrates the functional importance of MST to heading. In the adjacent area MT (or V5), neurons also respond to motion and are highly directionally selective, but they do not show specific selectivity to circular or radial trajectories 9 . The neurophysiology findings are reinforced by psychophysical studies suggesting the existence of analogous neural units in humans that integrate local-motion signals along complex flow trajectories 10,11 . In agreement with the neurophysiological studies, these units have very large receptive fields 12 and sum information over periods of one or two seconds (L. Santoro and D.C. Burr, Perception 28, 90c, 1999). There is also some evidence in humans for selectivity along the 'cardinal directions' of optic flow (radial and circular) 13 , although this issue is somewhat controversial 14 .A very strong motion-selective response at the boundary of Brodmann's areas 19 and 37 is shown by human imaging [15][16][17][18][19][20][21][22][23] . This area is generally thought to be the human analogue of monkey V5/MT-MST regions, and is referred to as 'V5/MT complex' (MT+). Other motion-sensitive areas have been identified: a dorsal region referred to as V3A 16,21,22,24 and a ventral region, seemingly activated by motion boundaries and second-order motion 20,21 . Here, using fMRI, we examined the response to optic-flow stimuli, and showed selective activation of a large area within the V5/MT complex to radial and circular motion, very different from the area activated by translational motion. Activation in response to optic flow occurred only when the direction of optic flow changed-abruptly or gradually-during the presentation period; continuous radial or circular motion produced no reliable activation in any area when measured against a matched random control. RESULTS Response to optic flowWe created dynamic displays of circular, radial, spiral and translational motion from random-dot patterns. The control stimuli were locally identical to the active stimuli; each dot moved along independent, randomly chosen trajectories ( Fig. 1; Methods). Responses of subjects to flow motion were measured against these random controls, with both active and control stimuli reversing direction every two seconds. There was a clear and specific activation in the temporal-occipital cortex, with no response in V1 or any other cortical area (example, Fig. 2a). The response extended for more than 1 cm along the sulcus that separates Brodmann's area 19 and 37, within the region that is usually referred to the human analogue of V5/MT complex [15][16][...

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Infective endocarditis (IE) in chronic haemodialysis (HD) is significantly more common and causes greater morbidity and mortality than in the general population, being second only to cardiovascular disease as the leading cause of death in this group of patients. Because of the peculiarity of this group of patients, it has been recently proposed to add a fifth category (health-care associated and HD-associated IE) in the actually four categories classification of IE (namely, native valve IE, prosthetic valve IE, IE in e.v. drug users, and nosocomial IE). Given that rates of acceptance into HD are increasing (including a higher proportion of older patients in whom valvular calcification is virtually ubiquitous), and along with improved survival in HD patients, the incidence of IE in this subset of patients will probably increase with significant diagnostic and therapeutic implications. In particular cardiac, diagnostic, echocardiographic, and surgical expertises are required to correctly identify patients at higher risk and who may benefit from surgical treatment. The aim of this review is to clarify the peculiar features of chronic HD patients with regard to pathogenesis, diagnosis, current therapeutic options, and determinants of prognosis of IE.

(a) MRI abnormalities in phenylketonuria are the result of a distinctive alteration of white matter suggesting the intracellular accumulation of a hydrophilic metabolite, which leaves unaffected white matter architecture and structure. (b) White matter abnormalities do not seem to reflect the mechanisms involved in the derangement of mental development in PKU. (c) Our data do not support the usefulness of conventional brain MRI examination in the clinical monitoring of phenylketonuria patients.