Encrypted storage of medical data on a grid.

OBJECTIVES: In this article we present grids as an architecture for medical image processing and health-care networks. We argue that confidential patient data should not be stored unprotected on a grid and explain why access control systems alone do not offer sufficient protection. The objective of our work is to propose a method that complements access control systems on a grid architecture and thus makes the storage of confidential data more secure. METHODS: Effective protection can be achieved by storing confidential data in encrypted form. This raises the problem of how authorized users get access to the data, since they need to have the decryption keys. RESULTS: Our proposal details a key management architecture, that allows encrypted storage and still enables users to access decryption keys for data they are authorized to see. To achieve this functionality we use distributed keyservers storing redundant shares of the keys. CONCLUSIONS: The resulting architecture achieves our primary objective of making the storage of confidential data more secure without loosing the data sharing properties of the grid architecture. Furthermore our architecture is robust against breakdowns and denial of service attacks. It scales well with the number of users and does not introduce a single point of failure into the system.

Quantitative electroencephalographic changes induced by odor detection and identification tasks: age related effects.

There are no previous studies which have compared quantitative electroencephalographic (QEEG) activity in young adult and normal elderly participants during olfactory tasks. This may be important if QEEG is to have a role in distinguishing between normal and pathological aging associated with this sensory system. Seventeen healthy elderly subjects (mean age 79.00+/-3.54 years) and 16 young adult controls (mean age 22.60+/-2.00 years) participated in the study. As reported in previous studies, beta1 and 2 activity was significantly greater in elderly subjects compared to young adults, thus confirming the reliability and validity of this study's quantitative electroencephalographic (QEEG) methodology. More alpha activity was evident in young adults compared with the elderly, whilst θ activity was distributed differently in the two age groups. These findings support previous literature suggesting EEG bandwidth activity reflect greater attentional capacity in young adults and EEG desynchronization in older people. Elderly subjects who identified two or fewer odors were found to have more beta activity in the olfaction condition compared to resting eyes closed, which may reflect cognitive impairment. These findings stress the importance of distinguishing subgroups of healthy elderly adults when examining the electroencephalographic profile.

Age-related changes in qEEG during cognitive tasks.

Early diagnosis of dementia can be difficult. Quantitative EEG (qEEG) in combination with cognitive tasks shows promise for improving diagnostic accuracy. The study of task induced qEEG changes in normal ageing is a prerequisite for differentiating these changes from those which are specific to dementia. Sixteen young adults (mean age 28.8+/-5.6 years) and 16 healthy cognitively normal older subjects (mean age 73.4+/-7.9 years) participated in the study. EEG recordings were made while subjects were in a relaxed (or resting) state, and also while they performed arithmetic and language tasks. From the resting to the arithmetic conditions, there was decreased alpha activity and increased delta and beta-3 activity for both subject groups. Changes in alpha and delta activity were found in almost all sites and could be associated with arousal. Increase in beta-3 activity was focal, appearing only in the posterior region of the brain and it could be assumed that this area is highly involved in arithmetic processes. In the young adult group, theta activity increased from the resting to the arithmetic conditions, while in the older group theta activity changes were in the opposite direction. From the resting to the language condition, there was increased delta activity and decreased alpha and beta-1 activity for both subject groups. Changes in alpha and delta activity were again found in almost all sites. The decrease in beta-1 activity was found in only four sites, but these were not specific to a region of the brain known to be involved in language processing. This consistency in qEEG changes during cognitive tasks suggests that the method can be applied to the investigation of cognitive deficits associated with a number of neurological syndromes.

Quantitative electroencephalography, with serial subtraction and odour detection in the differentiation of Alzheimer's disease and vascular dementia.

The diagnosis of dementia can be difficult, yet diagnostic accuracy has important prognostic and therapeutic implications. Nevertheless, conventional electroencephalography (EEG) has always played a secondary role in dementia investigation. More recently quantitative EEG (qEEG) has allowed more detailed and objective analysis of EEG data, but there is still no clearly defined clinical role for qEEG. We have used relative power qEEG measures made during resting and active brain conditions (serial subtraction and odour detection tasks) to differentiate between demented and non-demented subjects, and between subjects with different forms of dementia. Electroencephalograms were obtained from 15 subjects with clinically diagnosed Alzheimer's disease (AD), 16 with a clinical diagnosis of vascular dementia (VaD), and 16 non-demented control subjects. Discriminate function analyses were used to differentiate groups according to task, electrode site, and frequency bandwidth. Correct classification, as demented or non-demented, was made for 93% of cases using qEEG comparisons of resting states with eyes closed and eyes opened. Almost all subjects with AD and VaD were correctly classified with qEEG recorded during odour detection (95%). qEEG for serial subtraction correctly classified AD and VaD in 91% of the dementia group. These results have important implications for future qEEG research, and may be pertinent to the precision of diagnosis in patients with dementia.

Diring Yuriakh: A lower paleolithic site in central Siberia.

Lower Paleolithic artifacts have been recovered from a single occupation surface within stratified deposits at Diring Yuriakh, an archaeological site in central Siberia. Thermoluminescence age estimates from eolian sediments indicate that the cultural horizon is greater than 260,000 years old. Diring Yuriakh is an order of magnitude older than documented Paleolithic sites in Siberia and is important for understanding the timing of human expansion into the far north, early adaptations to cold climates, and the peopling of the Americas.

A molecular phylogeny of Mobile River drainage basin pleurocerid snails (Caenogastropoda: Cerithioidea).

Sequences from the mitochondrial 16S rRNA gene were obtained to construct a molecular phylogeny for Mobile River drainage basin pleurocerid snails. Data from 876 aligned positions generated a single most-parsimonious tree for each of three analytical approaches: (1) equal weighting, (2) transversions weighted 2 x transitions; and (3) transversions weighted 4 x transitions. Identical topologies for the resulting trees depict the genera Elimia and Pleurocera as monophyletic sister taxa. The genus Leptoxis is paraphyletic with Leptoxis plicata sister to the Elimia + Pleurocera clade. L. taeniata and L. ampla are sister taxa and L. picta is the most basal pleurocerid examined. When transversions were weighted 10x transitions a single most-parsimonious tree was obtained with the only topological difference being L. picta depicted as sister to L. taeniata and L. ampla and L. plicata is now the most basal pleurocerid examined. Many of the Elimia species are closely related, but we await further data before making any taxonomic recommendations. L. picta and L. plicata are quite distinct from each other and all other pleurocerid species examined. These data serves as an important foundation for future studies examining conservation genetics and systematics of this diverse and imperiled family.

To see or not to see: the effects of visible and invisible cues on line bisection judgements in unilateral neglect.

Patients with left unilateral neglect and matched controls were tested in two experiments to examine the effects of lateralized cues on line bisection judgements. Unlike previous studies in which letter or number cues were placed beyond the endpoint(s) of each line, we adopted a procedure which maintained the perceptual point of balance in the horizontal axis of each line. We also related the cueing task more closely to the act of bisection by requiring subjects to place a small mark in direct alignment with the endpoint(s) of each line. In the first experiment, it was found that, for controls, the presence or absence of visible lateralized cues did not differentially affect the magnitude of bisection errors. However, the magnitude of bisection errors made by neglect patients was significantly reduced (and reversed) in the presence of a visible left-sided cue, but remained well to the right of the midpoint in the absence of such cues. In a second experiment, subjects engaged in an otherwise identical cueing procedure, except that no visible marks appeared on the stimulus lines. Neither subject group was affected by the presence or absence of right-sided cues. However, the presence of left-sided cues again reduced the magnitude of bisection errors in neglect patients, but not in controls. These results indicate that the extent of the attentional bias exhibited by neglect patients can be ameliorated even in the absence of lateralized visible cues.

Initiation and execution of movement sequences in those suffering from and at-risk of developing Huntington's disease.

Recent research has shown that Huntington's disease (HD) causes problems in the initiation and execution of movement (akinesia, bradykinesia): information which is useful in documenting the functional progression of the disease. The present experiment used a sequential movement task to characterize such impairments. Eighteen patients diagnosed as suffering from HD, and a similar number of matched At-Risk (AR) and Normal control subjects, performed sequential button pressing tasks, under varying amounts of visual advance information. Specific dimensions of motor control were examined (hand, direction). Movement initiation and in particular movement duration were useful indicators of the functional progression of the disease, and also detected anomalies of performance in some AR individuals. Impaired motor programming was indicated by patients' difficulty in initiating movements in the absence of external visual cues, and their problems in utilizing advance information to control movement. Patients had specific deficits in initiating movements with the nonpreferred hand, and directional movement asymmetries were accentuated. The results suggest that HD causes difficulties at three discrete levels: in utilizing advance information, in the initiation and in the spatial representation of movement.

Direction of gaze during vibrotactile choice reaction time tasks.

A vibrotactile choice reaction time (RT) task was used, with the hands in their own hemispace (arms uncrossed), and in their opposite hemispace (arms crossed). Gaze was directed at the stimulated and responding hand, away from it at the other (inactive) hand, or at a central fixation point (a neutral control). Responses were slower in the crossed than the uncrossed condition. Further, in the crossed condition, responses were faster when subjects looked at the stimulated and responding hand, rather than at the inactive hand or at the central fixation point. As RT in the latter two conditions did not differ, there is a benefit when subjects look at the stimulated and responding hand, rather than a cost when they look at the inactive hand. In the look at condition, visual or attentional factors may reduce the response coding conflict which occurs when arms are crossed.

Head and body hemispace to left and right III: Vibrotactile stimulation and sensory and motor components.

Response latencies were measured to vibrotactile stimulation delivered to the forefingers of the left or right hands which were positioned ipsilaterally or contralaterally (across the midline) in left or right hemispace. While the two hands did not differ in speed of response, either hand performed better when located in right hemispace (experiment 1). This effect was greatly reduced, though not eliminated, with 90 degrees lateral head turn, when performance was better with stimulation and responding in right-of-head hemispace, but not right-of-body hemispace (experiment 2). When different hands received stimulation and initiated responses, and were located in either the same or opposite hemispace, right-hemispace superiority was found to be motor rather than sensory (experiment 3). These findings are discussed in the context of the true and the phenomenological midline and the clinical syndrome of hemineglect.

Head and body space to left and right, front and rear--I. Unidirectional competitive auditory stimulation.

Very substantial right ear advantages (REAs) and right side advantages (RSAs) are reported for vocal shadowing latencies to laterally presented competitive verbal stimuli from a single earphone or loudspeaker. When head and body hemispace were dissociated by inducing a 90 degree head turn, with presentations either lateral or front-back with respect to the body, RSAs and REAs vanished, indicating that stimuli neither in the head nor in the body hemispace alone appear capable of generating any lateral asymmetries. However, a front-of-body (but not front-of-head) superiority compared with the rear was obtained. Most importantly, a powerful ventriloquism effect was obtained whereby a laterally placed dummy loudspeaker produced "pseudo"-RSAs with anterior-posterior-located sound sources. This suggests that it is the perceived position of a sound source rather than its actual position or ear of entry which determines asymmetries.