Partial Information Decomposition as a Unified Approach to the Specification of Neural Goal Functions

In many neural systems anatomical motifs are present repeatedly, but despite their structural similarity they can serve very different tasks. A prime example for such a motif is the canonical microcircuit of six-layered neo-cortex, which is repeated across cortical areas, and is involved in a number of different tasks (e.g.sensory, cognitive, or motor tasks). This observation has spawned interest in finding a common underlying principle, a 'goal function', of information processing implemented in this structure. By definition such a goal function, if universal, cannot be cast in processing-domain specific language (e.g. 'edge filtering', 'working memory'). Thus, to formulate such a principle, we have to use a domain-independent framework. Information theory offers such a framework. However, while the classical framework of information theory focuses on the relation between one input and one output (Shannon's mutual information), we argue that neural information processing crucially depends on the combination of \textit{multiple} inputs to create the output of a processor. To account for this, we use a very recent extension of Shannon Information theory, called partial information decomposition (PID). PID allows to quantify the information that several inputs provide individually (unique information), redundantly (shared information) or only jointly (synergistic information) about the output. First, we review the framework of PID. Then we apply it to reevaluate and analyze several earlier proposals of information theoretic neural goal functions (predictive coding, infomax, coherent infomax, efficient coding). We find that PID allows to compare these goal functions in a common framework, and also provides a versatile approach to design new goal functions from first principles. Building on this, we design and analyze a novel goal function, called 'coding with synergy'. [...]Comment: 21 pages, 4 figures, appendi

Changes in structural network topology correlate with severity of hallucinatory behavior in Parkinson's disease

Inefficient integration between bottom-up visual input and higher order visual processing regions is implicated in visual hallucinations in Parkinson's disease (PD). Here, we investigated white matter contributions to this perceptual imbalance hypothesis. Twenty-nine PD patients were assessed for hallucinatory behavior. Hallucination severity was correlated to connectivity strength of the network using the network-based statistic approach. The results showed that hallucination severity was associated with reduced connectivity within a subnetwork that included the majority of the diverse club. This network showed overall greater between-module scores compared with nodes not associated with hallucination severity. Reduced between-module connectivity in the lateral occipital cortex, insula, and pars orbitalis and decreased within-module connectivity in the prefrontal, somatosensory, and primary visual cortices were associated with hallucination severity. Conversely, hallucination severity was associated with increased between- and within-module connectivity in the orbitofrontal and temporal cortex, as well as regions comprising the dorsal attentional and default mode network. These results suggest that hallucination severity is associated with marked alterations in structural network topology with changes in participation along the perceptual hierarchy. This may result in the inefficient transfer of information that gives rise to hallucinations in PD. Author SummaryInefficient integration of information between external stimuli and internal perceptual predictions may lead to misperceptions or visual hallucinations in Parkinson's disease (PD). In this study, we show that hallucinatory behavior in PD patients is associated with marked alterations in structural network topology. Severity of hallucinatory behavior was associated with decreased connectivity in a large subnetwork that included the majority of the diverse club, nodes with a high number of between-module connections. Furthermore, changes in between-module connectivity were found across brain regions involved in visual processing, top-down prediction centers, and endogenous attention, including the occipital, orbitofrontal, and posterior cingulate cortex. Together, these findings suggest that impaired integration across different sides across different perceptual processing regions may result in inefficient transfer of information

Traumatic spinal cord injury in South Africa and Sweden : epidemiologic features and functioning

Background: Trauma to the human spinal cord typically strikes out of the blue, leaving those surviving the initial ordeal with permanent or temporary deficits in health and functioning. Because of this, traumatic spinal cord injuries (TSCI) impose a significant burden on society. While these facts are well known for certain countries, the International Perspectives on Spinal Cord Injury Report highlights the need for the remaining countries to establish a foundation upon which injuries could be prevented and functioning problems addressed. In South Africa, the foundation for primary prevention and knowledge of the unmet needs of persons with TSCI are not yet established. Aim: To develop an evidence-based foundation for TSCI in South Africa that addresses prevention both in terms of injury occurrence and problems with functioning. Methods: This thesis utilised a mixed-method approach to answer epidemiologic and functioning questions. A prospective, population-based design was used in Study I and II to determine the incidence, aetiology and injury profiles of newly-injured adults with TSCI in Cape Town, South Africa and Stockholm, Sweden. In the Functioning section of the thesis (Study III), a comparative content validity design was used to define the nature of functioning categories in a generic outcome measure currently used in the South African SCI rehabilitation field, and a standardised measure not yet adopted in the local context, against the International Classification of Functioning, Disability and Health and the brief ICF core sets for SCI in the post-acute context. In Study IV, qualitative description was used to explore the experiences of reclaiming participation in 17 chronic survivors of TSCI by emphasising their met and unmet needs as well as the conditions influencing them. Findings: One-hundred and forty-seven and 49 incident cases, resulting in an annual crude incidence rate of 75.6 and 19.0 per million population, were registered for the region of South Africa (study I) and Sweden (study II), respectively. The leading cause of injury in South Africa was assault, accounting for approximately 60% of all incident cases, compared with the leading cause in Sweden, where falls was responsible for 58% of all cases. The two cohorts differed significantly with respect to demographic and aetiologic characteristics. Concerning functioning, Study III found that the generic rehabilitation outcome measure was not fully conceptualised within the ICF and did not cover all the essential functioning aspects as contained in the brief core set. In contrast, the standardised outcome measure was fully conceptualised within the ICF and covered, in its entirety, the activity and participation categories contained in the brief core set. In Study IV, clients’ perspectives confirmed 'participation' as a desirable and possible goal by effectively dealing with the new self, negotiating obstacles, identifying facilitators of participation, and becoming an agent. These critical aspects − also categories − were essential for reconstructing meaning and prioritising important life situations. Conclusions: The incidence of TSCI in South Africa is among the highest in the world and is mainly caused by assault, while the incidence in Sweden appeared consistent to what is proposed for Western Europe. Furthermore, there is a need to raise awareness and facilitate the use of standardised outcome measures in TSCI rehabilitation, since the current operational measure in the South African SCI rehabilitation field presented some shortcomings. It is remarkable to conclude that while participation is indeed a reality after injury, the dimensionality of challenges remains an issue for further discourse. The insights gained from these studies provide an evidence-based foundation for impacting primary prevention action plans and the alignment of rehabilitation practices towards addressing the unmet needs of survivors

Mycorrhizal Feedbacks Influence Global Forest Structure and Diversity

One mechanism proposed to explain high species diversity in tropical systems is strong negative conspecific density dependence (CDD), which reduces recruitment of juveniles in proximity to conspecific adult plants. Although evidence shows that plant-specific soil pathogens can drive negative CDD, trees also form key mutualisms with mycorrhizal fungi, which may counteract these effects. Across 43 large-scale forest plots worldwide, we tested whether ectomycorrhizal tree species exhibit weaker negative CDD than arbuscular mycorrhizal tree species. We further tested for conmycorrhizal density dependence (CMDD) to test for benefit from shared mutualists. We found that the strength of CDD varies systematically with mycorrhizal type, with ectomycorrhizal tree species exhibiting higher sapling densities with increasing adult densities than arbuscular mycorrhizal tree species. Moreover, we found evidence of positive CMDD for tree species of both mycorrhizal types. Collectively, these findings indicate that mycorrhizal interactions likely play a foundational role in global forest diversity patterns and structure

Star formation in the merging Galaxy NGC3256

The central 5 kpc of the ultra-luminous merging galaxy NGC 3256 was mapped at J, H, K, L, and 10 micrometer, and a 2 micrometer spectra of the nuclear region was obtained. This data was used to identify and characterize the super starburst which has apparently been triggered and fuelled by the merger of two gas rich galaxies. It is also shown that the old stellar population has relaxed into a single spheroidal system, and that a supernova driven wind might eventually drive any remaining gas from the system to leave a relic which will be indistinguishable from an elliptical galaxy

Adenomatoid tumors of the male and female genital tract are defined by TRAF7 mutations that drive aberrant NF-kB pathway activation.

Adenomatoid tumors are the most common neoplasm of the epididymis, and histologically similar adenomatoid tumors also commonly arise in the uterus and fallopian tube. To investigate the molecular pathogenesis of these tumors, we performed genomic profiling on a cohort of 31 adenomatoid tumors of the male and female genital tracts. We identified that all tumors harbored somatic missense mutations in the TRAF7 gene, which encodes an E3 ubiquitin ligase belonging to the family of tumor necrosis factor receptor-associated factors (TRAFs). These mutations all clustered into one of five recurrent hotspots within the WD40 repeat domains at the C-terminus of the protein. Functional studies in vitro revealed that expression of mutant but not wild-type TRAF7 led to increased phosphorylation of nuclear factor-kappa B (NF-kB) and increased expression of L1 cell adhesion molecule (L1CAM), a marker of NF-kB pathway activation. Immunohistochemistry demonstrated robust L1CAM expression in adenomatoid tumors that was absent in normal mesothelial cells, malignant peritoneal mesotheliomas and multilocular peritoneal inclusion cysts. Together, these studies demonstrate that adenomatoid tumors of the male and female genital tract are genetically defined by TRAF7 mutation that drives aberrant NF-kB pathway activation

VLA Spectral Line Observations of a Shocked Cold H II Region in G70.7+1.2

We have observed the molecular globule G70.7+1.2 at 1375 MHz using the C configuration of the VLA, and have imaged a peculiar H168α recombination line detected at the Arecibo radio telescope. The narrow width of the recombination line (Δv ~ 3 km s-1) indicates gas cooler than 185 K and suggests that the globule harbors the coldest known H II region. Previous work showed that the recombination line came either from newly ionized gas outside a bow shock produced by supersonic motion of an early-type star through the molecular globule, or from a cold H II region inside the globule. The 20'' angular resolution of the VLA image of G70.7+1.2 was sufficient to resolve the separation between the nonthermal radio-emitting bow shock and the thermal H II region. The spectral line images show that the radio recombination line comes from cold gas near the outer boundary of the bow shock and that the line intensity is enhanced by stimulated amplification of the nonthermal continuum emanating from the bow shock

A national policy for malaria elimination in Swaziland: a first for sub-Saharan Africa

Swaziland is working to be the first country in mainland sub-Saharan Africa to eliminate malaria. The highest level of Swaziland's government recently approved a national elimination policy, which endorses Swaziland's robust national elimination strategic plan. This commentary outlines Swaziland's progress towards elimination as well as the challenges that remain, primarily around securing long-term financial resources and managing imported cases from neighbouring countries

Probing a Set of Trajectories to Maximize Captured Information

We study a trajectory analysis problem we call the Trajectory Capture Problem (TCP), in which, for a given input set T of trajectories in the plane, and an integer k? 2, we seek to compute a set of k points ("portals") to maximize the total weight of all subtrajectories of T between pairs of portals. This problem naturally arises in trajectory analysis and summarization. We show that the TCP is NP-hard (even in very special cases) and give some first approximation results. Our main focus is on attacking the TCP with practical algorithm-engineering approaches, including integer linear programming (to solve instances to provable optimality) and local search methods. We study the integrality gap arising from such approaches. We analyze our methods on different classes of data, including benchmark instances that we generate. Our goal is to understand the best performing heuristics, based on both solution time and solution quality. We demonstrate that we are able to compute provably optimal solutions for real-world instances