title: Dense gap-junction connections support dynamic Turing structures in the cortex

authors: Steyn-Ross, D. Alistair

abstract: The recent report by Fukuda et al [1] provides convincing evidence for dense gap-junction connectivity between inhibitory neurons in the cat visual cortex, each neuron making 60 +/- 12 gap-junction dendritic connections with neurons in both the same and adjoining orientation columns. These resistive connections provide a source of diffusive current to the receiving neuron, supplementing the chemical-synaptic currents generated by incoming action-potential spike activity. Fukuda et al describe how the gap junctions form a dense and homogeneous electrical coupling of interneurons, and propose that this diffusion-coupled network provides the substrate for synchronization of neuronal populations.

To date, large-scale population-based mathematical models of the cortex have ignored diffusive communication between neurons. Here we augment a well-established mean-field cortical model [2] by incorporating gap-junction-mediated diffusion currents, and we investigate the implications of strong diffusive coupling. The significant result is the model prediction that the 2D cortex can spontaneously generate centimetre-scale Turing structures (spatial patterns), in which regions of high-firing activity are intermixed with regions of low-firing activity (see Fig. 1). Since coupling strength decreases with increases in firing rate, these patterns are expected to exchange contrast on a slow time-scale, with low-firing patches increasing their activity at the expense of high-firing patches. These theoretical predictions are consistent with the slowly fluctuating large-scale brain-activity images detected from the BOLD (blood oxygen-level-dependent) signal [3].

text: Dense gap-junction connections support dynamic Turing structures in the cortex The recent report by Fukuda et al [1] provides convincing evidence for dense gap-junction connectivity between inhibitory neurons in the cat visual cortex, each neuron making 60 +/- 12 gap-junction dendritic connections with neurons in both the same and adjoining orientation columns. These resistive connections provide a source of diffusive current to the receiving neuron, supplementing the chemical-synaptic currents generated by incoming action-potential spike activity. Fukuda et al describe how the gap junctions form a dense and homogeneous electrical coupling of interneurons, and propose that this diffusion-coupled network provides the substrate for synchronization of neuronal populations.

To date, large-scale population-based mathematical models of the cortex have ignored diffusive communication between neurons. Here we augment a well-established mean-field cortical model [2] by incorporating gap-junction-mediated diffusion currents, and we investigate the implications of strong diffusive coupling. The significant result is the model prediction that the 2D cortex can spontaneously generate centimetre-scale Turing structures (spatial patterns), in which regions of high-firing activity are intermixed with regions of low-firing activity (see Fig. 1). Since coupling strength decreases with increases in firing rate, these patterns are expected to exchange contrast on a slow time-scale, with low-firing patches increasing their activity at the expense of high-firing patches. These theoretical predictions are consistent with the slowly fluctuating large-scale brain-activity images detected from the BOLD (blood oxygen-level-dependent) signal [3].

year: 2007-07

title: Distributed OpenGL Rendering in Network Bandwidth Constrained Environments

authors: Neal, Braden

subjects: computer science

abstract: Display walls made from multiple monitors are often used when very high resolution images are required. To utilise a display wall, rendering information must be sent to each computer that the monitors are connect to. The network is often the performance bottleneck for demanding applications, like high performance 3D animations. This paper introduces ClusterGL; a distribution library for OpenGL applications. ClusterGL reduces network traffic by using compression, frame differencing and multi-cast. Existing applications can use ClusterGL without recompilation. Benchmarks show that, for most applications, ClusterGL outperforms other systems that support unmodified OpenGL applications including Chromium and BroadcastGL. The difference is larger for more complex scene geometries and when there are more display machines. For example, when rendering OpenArena, ClusterGL outperforms Chromium by over 300% on the Symphony display wall at The University of Waikato, New Zealand. This display has 20 monitors supported by five computers connected by gigabit Ethernet, with a full resolution of over 35 megapixels. ClusterGL is freely available via Google Code.

text: Distributed OpenGL Rendering in Network Bandwidth Constrained Environments Display walls made from multiple monitors are often used when very high resolution images are required. To utilise a display wall, rendering information must be sent to each computer that the monitors are connect to. The network is often the performance bottleneck for demanding applications, like high performance 3D animations. This paper introduces ClusterGL; a distribution library for OpenGL applications. ClusterGL reduces network traffic by using compression, frame differencing and multi-cast. Existing applications can use ClusterGL without recompilation. Benchmarks show that, for most applications, ClusterGL outperforms other systems that support unmodified OpenGL applications including Chromium and BroadcastGL. The difference is larger for more complex scene geometries and when there are more display machines. For example, when rendering OpenArena, ClusterGL outperforms Chromium by over 300% on the Symphony display wall at The University of Waikato, New Zealand. This display has 20 monitors supported by five computers connected by gigabit Ethernet, with a full resolution of over 35 megapixels. ClusterGL is freely available via Google Code.

year: 2011

title: Whanau Whakapakari: a Māori-centred approach to child rearing and Parent-training programmes

authors: Herbert, Averil May Lloyd

subjects: Whanau Whakapakari

abstract: The goal of this Whanau Whakapakari (Strengthening Families) research was to define critical aspects of Māori experiences and views on child-rearing practices, and to describe whanau (extended family) values and expectations for tamariki (children) and mokopuna (grandchildren).  Furthermore, these Māori views were included in culturally adapted parent-training programmes.  The overall aim was to devise an approach to emphasise client strengths and provide best outcomes for research participants.  Qualitative aspects included discussing the research processes in the Māori community by acknowledging the roles of whanau, hapu (sub-tribal), and iwi (tribal) structures.  I also identified the importance of pan-tribal and urban Māori groups in the current research.  As the project developed, an ongoing consultation and feedback protocol was established to ensure that Māori views on the research and the written outcomes were recognised.  In-depth interviews with kaumatua (elders), and focus groups with Māori service providers and Māori parents were analysed qualitatively to establish Māori values in child rearing and parenting, and the knowledge and skills that contribute to effective parenting and family functioning.  Values identified from these participants confirmed the central role of whanaungatanga (family connections), whakapapa (genealogy), and awhinatanga (support) for Māori. Two culturally adapted parent-training programmes, the Matuatanga (Parenting) Relationships Model and the Matuatanga Values Model programmes, were developed and compared with a Standard Parent Training programme.  The Matuatanga Relationships Model programme emphasised the importance of child, parent and whanau relationships and interactions.  The Matuatanga Values Model programme emphasised Māori values derived from the qualitative data - whanaungatanga, whakapapa and awhinatanga.  A range of pre- and post-training measures were undertaken to identify acceptable and appropriate measures for quantifying parent-training outcomes.  These included questions on support networks, parent expectations of children, parental self-efficacy, parental self-rating, critical-incident scenarios, and programme evaluation.  While 78 participants attended at least one of the research sessions 22 participants provided pre- and post-training measures for the Whanau Whakapakari programmes.  Results showed that there was a medium effect size improvement across all Standard Parent Training and Matuatanga Model programmes and a statistically significant improvement in the Standard Parent Training and Matuatanga Relationship Model programmes.  There were no statistically significant differences between the outcomes of the different programmes but qualitative differences from evaluation and feedback data were considered in identifying specific skills acquisition, general understanding and enjoyment components in the programmes.  Results from the different measures indicated that parent expectations and critical-incident scenario measures provided the most information on post-training changes.  Analysis of the outcome data with the attendance patterns confirmed the value of parent-training programmes per se and indicated that at least in the short term, parent effectiveness scores continued to improve for participants who continued to attend for more than one programme.  Programme follow-ups considered natural whanau supports in the Māori community and issues of social and cultural validity.  Integration of standard parent-training concepts and cultural concepts suggest a multi-dimensional approach which recognises parenting skills acquisition and cultural validation of whanau concepts relevant to parenting for Māori.

text: Whanau Whakapakari: a Māori-centred approach to child rearing and Parent-training programmes The goal of this Whanau Whakapakari (Strengthening Families) research was to define critical aspects of Māori experiences and views on child-rearing practices, and to describe whanau (extended family) values and expectations for tamariki (children) and mokopuna (grandchildren).  Furthermore, these Māori views were included in culturally adapted parent-training programmes.  The overall aim was to devise an approach to emphasise client strengths and provide best outcomes for research participants.  Qualitative aspects included discussing the research processes in the Māori community by acknowledging the roles of whanau, hapu (sub-tribal), and iwi (tribal) structures.  I also identified the importance of pan-tribal and urban Māori groups in the current research.  As the project developed, an ongoing consultation and feedback protocol was established to ensure that Māori views on the research and the written outcomes were recognised.  In-depth interviews with kaumatua (elders), and focus groups with Māori service providers and Māori parents were analysed qualitatively to establish Māori values in child rearing and parenting, and the knowledge and skills that contribute to effective parenting and family functioning.  Values identified from these participants confirmed the central role of whanaungatanga (family connections), whakapapa (genealogy), and awhinatanga (support) for Māori. Two culturally adapted parent-training programmes, the Matuatanga (Parenting) Relationships Model and the Matuatanga Values Model programmes, were developed and compared with a Standard Parent Training programme.  The Matuatanga Relationships Model programme emphasised the importance of child, parent and whanau relationships and interactions.  The Matuatanga Values Model programme emphasised Māori values derived from the qualitative data - whanaungatanga, whakapapa and awhinatanga.  A range of pre- and post-training measures were undertaken to identify acceptable and appropriate measures for quantifying parent-training outcomes.  These included questions on support networks, parent expectations of children, parental self-efficacy, parental self-rating, critical-incident scenarios, and programme evaluation.  While 78 participants attended at least one of the research sessions 22 participants provided pre- and post-training measures for the Whanau Whakapakari programmes.  Results showed that there was a medium effect size improvement across all Standard Parent Training and Matuatanga Model programmes and a statistically significant improvement in the Standard Parent Training and Matuatanga Relationship Model programmes.  There were no statistically significant differences between the outcomes of the different programmes but qualitative differences from evaluation and feedback data were considered in identifying specific skills acquisition, general understanding and enjoyment components in the programmes.  Results from the different measures indicated that parent expectations and critical-incident scenario measures provided the most information on post-training changes.  Analysis of the outcome data with the attendance patterns confirmed the value of parent-training programmes per se and indicated that at least in the short term, parent effectiveness scores continued to improve for participants who continued to attend for more than one programme.  Programme follow-ups considered natural whanau supports in the Māori community and issues of social and cultural validity.  Integration of standard parent-training concepts and cultural concepts suggest a multi-dimensional approach which recognises parenting skills acquisition and cultural validation of whanau concepts relevant to parenting for Māori.

year: 2001