Assessing the solid protocol in relation to security and privacy obligations

The Solid specification aims to empower data subjects by giving them direct access control over their data across multiple applications. As governments are manifesting their interest in this framework for citizen empowerment and e-government services, security and privacy represent pivotal issues to be addressed. By analysing the relevant legislation, with an emphasis on GDPR and officially approved documents such as codes of conduct and relevant security ISO standards, we formulate the primary security and privacy requirements for such a framework. The legislation places some obligations on pod providers, much like cloud services. However, what is more interesting is that Solid has the potential to support GDPR compliance of Solid apps and data users that connect, via the protocol, to Solid pods containing personal data. A Solid-based healthcare use case is illustrated where identifying such controllers responsible for apps and data users is essential for the system to be deployed. Furthermore, we survey the current Solid protocol specifications regarding how they cover the highlighted requirements, and draw attention to potential gaps between the specifications and requirements. We also point out the contribution of recent academic work presenting novel approaches to increase the security and privacy degree provided by the Solid project. This paper has a twofold contribution to improve user awareness of how Solid can help protect their data and to present possible future research lines on Solid security and privacy enhancements

Of house and men: The functional organization of face and place representations in the ventral visual stream using fMRI techniques

The ventral part of the visual cortex has been proven to be highly selective to objects. Certain areas seem to be specifically tuned to certain categories of objects, such as faces, body parts, and houses. Even though the ventral visual stream has been studied extensively in the past, not much is known about its precise organization. Do the object-selective areas operate as separate clusters, or are they part of a larger topographic map, where continuous changes in stimuli lead to continuous shifts in activations across the cortex? Such topographic maps have been found in the primary visual cortex and surrounding areas when looking at the retinotopic organization of visual information, but few studies have focused on the extent of topographic maps and to what extent they are applicable to other aspects of perception. As the face-selective areas of the ventral visual stream have received special attention in the ongoing discussions about functional organization, a series of studies were set up with the face-and place-selective areas of high-level visual cortex as the main focus. Study 1 investigated whether the category-selective regions are embedded in a topographic map, adapting the continuous mapping techniques used in retinotopic mapping research to suit the object-selective areas of the human brain. A morph-series was created between a face and a house, to try and establish whether the morph-stimuli were represented in the intermediate area between the face-and house-selective areas, forming a continuous map of object category. While the phase-encoding technique was proven to be successful in detecting the presented stimulus information (face and house information), no large-scale maps were found in the ventral visual stream. Study 2 tested the potential of the phase-encoding technique by performing the same tests as in Study 1, this time on participants suffering from specific retinal defects. It highlighted the differences in responses in lower and higher visual cortex and it illustrated the risks involved in using relative comparison techniques: deactivations in the primary visual cortex and the foveal confluence caused patterns of ‘activations’ in areas that should not be responsive due to a lack of retinal input. Finally, Study 3 focused on the functional organization of the face-selective areas, using a multivariate technique to try and gain more insight into the representations of these areas by manipulating perceptual (featural information such as eye color and mouth shape, and configural information such as spacing between eyes and the position of the mouth) and contextual information linked to faces. As the contextual information dealt with the location a face was associated with, the place-selective areas were also taken into account. Results show that mainly perceptual information was represented in the face-selective regions. Contextual information linked to location was only distinguishable in the place-selective areas, while effects of familiarity (whether or not a face was associated with background information) were found in some of the face-selective areas. Together, these studies reveal more about the functional organization and the representations in high-level cortex.nrpages: 120status: publishe

Representations of facial identity information in the ventral visual stream investigated with multivoxel pattern analyses

The neural basis of face recognition has been investigated extensively. Using fMRI, several regions have been identified in the human ventral visual stream that seem to be involved in processing and identifying faces, but the nature of the face representations in these regions is not well known. In particular, multivoxel pattern analyses have revealed distributed maps within these regions, but did not reveal the organizing principles of these maps. Here we isolated different types of perceptual and conceptual face properties to determine which properties are mapped in which regions. A set of faces was created with systematic manipulations of featural and configural visual characteristics. In a second part of the study, personal and spatial context information was added to all faces except one. The perceptual properties of faces were represented in face regions and in other regions of interest such as early visual and object-selective cortex. Only representations in early visual cortex were correlated with pixel-based similarities between the stimuli. The representation of nonperceptual properties was less distributed. In particular, the spatial location associated with a face was only represented in the parahippocampal place area. These findings demonstrate a relatively distributed representation of perceptual and conceptual face properties that involves both face-selective/sensitive and non-face-selective cortical regions.status: publishe

Visual Space and Object Space in the Cerebral Cortex of Retinal Disease Patients

<div><p>The lower areas of the hierarchically organized visual cortex are strongly retinotopically organized, with strong responses to specific retinotopic stimuli, and no response to other stimuli outside these preferred regions. Higher areas in the ventral occipitotemporal cortex show a weak eccentricity bias, and are mainly sensitive for object category (e.g., faces versus buildings). This study investigated how the mapping of eccentricity and category sensitivity using functional magnetic resonance imaging is affected by a retinal lesion in two very different low vision patients: a patient with a large central scotoma, affecting central input to the retina (juvenile macular degeneration), and a patient where input to the peripheral retina is lost (retinitis pigmentosa). From the retinal degeneration, we can predict specific losses of retinotopic activation. These predictions were confirmed when comparing stimulus activations with a no-stimulus fixation baseline. At the same time, however, seemingly contradictory patterns of activation, unexpected given the retinal degeneration, were observed when different stimulus conditions were directly compared. These unexpected activations were due to position-specific deactivations, indicating the importance of investigating absolute activation (relative to a no-stimulus baseline) rather than relative activation (comparing different stimulus conditions). Data from two controls, with simulated scotomas that matched the lesions in the two patients also showed that retinotopic mapping results could be explained by a combination of activations at the stimulated locations and deactivations at unstimulated locations. Category sensitivity was preserved in the two patients. In sum, when we take into account the full pattern of activations and deactivations elicited in retinotopic cortex and throughout the ventral object vision pathway in low vision patients, the pattern of (de)activation is consistent with the retinal loss.</p></div

Stimulus set filtered with simulated retinal defects.

<p>(A) Example of the stimulus set under normal viewing conditions (B) Stimulus set for the JMD control study. Most conditions show a blank screen, with the five most eccentric stimuli showing part of the rings. (C) Stimulus set for the RP control study. The shift between the visible and not visible stimuli is more gradual, with input present in a large part of the stimulus sequence. Only the most eccentric stimuli are not visible any more.</p

Relative preference for different eccentricities in lower visual areas without a simulated scotoma.

<p>The medial view of the posterior part of right and left hemisphere is shown on an inflated cortical surface for control 2. The approximate location of the calcarine sulcus is marked with a dotted line. The color legend is shown above (orange-red for central stimuli, green for paracentral stimuli, blue-purple for peripheral stimuli).</p

Preference and activity patterns for different eccentricities in the ventral cortex with peripheral (simulated) scotoma.

<p>(Left) Relative preference in the eccentricity mapping paradigm for the RP patient (A), control 1 (C) and control 2 (E), shown on an inflated hemisphere. The color legend is shown above (orange-red for central stimuli, green for paracentral stimuli, blue-purple for peripheral stimuli). The black lines mark the face-sensitive areas (FA), the red lines mark the house (place)-sensitive areas (PA) defined by the blocked localizer design. (Right) average beta values of three conditions, when the eccentricity data are analyzed as a block design and compared to a fixation baseline, in both the FA and PA region for the RP patient (B), control 1 (D) and control 2 (F).</p

Preference and activity patterns for different eccentricities in lower visual areas for the RP patient.

<p>(A) The medial view of the posterior part of right and left hemisphere is shown on an inflated cortical surface. The approximate location of the calcarine sulcus is marked with a dotted line. The color legend is shown above (orange-red for central stimuli, green for paracentral stimuli, blue-purple for peripheral stimuli) and reflects the relative preference to the different eccentricities. In black two regions are marked which are further characterized for illustration purposes. The data of one region (red arrow/box) are mostly dominated by a positive response, and for the other region (blue arrow/box) mostly by a negative response compared to a no-stimulus baseline (B) Activity patterns in both hemispheres compared to a fixation baseline, at p<0.05 uncorrected for one of three conditions: central (8 most central stimuli, contrasted against baseline), paracentral (8 paracentral stimuli, contrasted against baseline) and peripheral (8 most eccentric stimuli, contrasted against baseline). The selected ROIs now show the underlying positive and negative responses. (C) Time course averaged across runs and across stimulus sequences to represent the response in a selected ROI to different eccentricities. The red dotted lines represent the 95% confidence intervals (calculated using the variation across runs). (C, left panel) A positive response to the most central stimuli, with a strong drop in activation to a near zero response when more eccentric stimuli are presented (C, right panel) Strong deactivations for the central and paracentral stimuli, and a response close to zero for the peripheral stimuli (D) Average beta values in each selected ROI. (D, left panel) Positive responses in the central and paracentral conditions, and a near zero response in the peripheral condition. (D, right panel) Negative responses (beta values) for the (para)central conditions and a near zero response to the peripheral condition.</p

Preference and activity patterns for different eccentricities in lower visual areas for the JMD controls.

<p>(A) The medial view of the posterior part of right and left hemisphere is shown on an inflated cortical surface for the two controls (control 1: upper figure, control 2: lower figure). They were tested with the stimulus set simulating the JMD scotoma. The approximate location of the calcarine sulcus is marked with a dotted line. The color legend is shown above (orange-red for central stimuli, green for paracentral stimuli, blue-purple for peripheral stimuli) and reflects the relative preference to the different eccentricities. In black two regions are marked which are further characterized for illustration purposes. The data of one region (red arrow/box) are mostly dominated by a positive response, and for the other region (blue arrow/box) mostly by a negative response compared to a no-stimulus baseline. (B) Average beta values in each selected ROI. The red arrows and box indicate activity of a ROI that shows a positive response to the (visible) peripheral stimuli, while the blue arrows and box show a ROI where negative responses to unstimulated central parts of the visual field cause a phase preference in the absence of activation in the other conditions.</p

Relative preference to the object-morph stimuli in the ventral cortex of the two patients.

<p>Relative preference in the object-morph paradigm, shown on an inflated hemisphere for the JMD patient (A) and the RP patient (B). The color legend is shown above (orange-red for central stimuli, green for paracentral stimuli, blue-purple for peripheral stimuli). The black lines mark the face-sensitive areas; the red lines mark the house (place)-sensitive areas, defined by the blocked localizer design.</p