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Papers by Walter Schneider

Architectures for Intelligence

Page 1. LE COPY An instructable connectionist/control architecture: Using rule-based instructions... more Page 1. LE COPY An instructable connectionist/control architecture: Using rule-based instructions to accomplish connectionist learning in a human time scale N Technical Report AlP - 95 Walter Schneider and William L. Oliver N ...

: Given the massively parallel nature of the brain an obvious question is why are so many informa... more : Given the massively parallel nature of the brain an obvious question is why are so many information processing functions serial? In particular, this paper addresses the issue of the comparison process. Behavioral data show that in perceptual matching tasks (such as memory scanning and visual search) performance is systematically affected by stimulus load, in that required processing time increases with each additional comparison item. It is arguable whether this indicates a processing system that performs serial comparisons, or a system for which comparisons are done in parallel but reaction time is affected by load because of other system limitations. In this simulation we show that in a modular connectionist system vector transmission is possible in parallel, but the comparison process within a module must be done serially unless accuracy is sacrificed.

It is widely held that there is a distinction between attentive and automatic cognitive processin... more It is widely held that there is a distinction between attentive and automatic cognitive processing. In research on attention using visual search tasks, the detection performance of human subjects in consistent mappingparadigms is generally regarded as indicating a shift, with practice, from serial, attentional, controlled processing to parallel, automatic processing, while detection performance in varied mappingparadigms is taken to indicate that processing remains under attentional control. This paper proposes a priority learningmechanism to model the effects of practice and the development of automaticity, in visual search tasks. A connectionist simulation model implements this learning algorithm. Five prominent features of visual search practice effects are simulated. These are: 1) in consistent mapping tasks, practice reduces processing time, particularly the slope of reaction times as a function of the number of comparisons; 2) in varied mapping tasks, there is no change in the...

Brain injury, 2018

Multisite and longitudinal neuroimaging studies are important in uncovering trajectories of recov... more Multisite and longitudinal neuroimaging studies are important in uncovering trajectories of recovery and neurodegeneration following traumatic brain injury (TBI) and concussion through the use of diffusion tensor imaging (DTI) and other imaging modalities. This study assessed differences in anisotropic diffusion measurement across four scanners using a human and a novel phantom developed in conjunction with the Chronic Effects of Neurotrauma Consortium. Human scans provided measurement within biological tissue, and the novel physical phantom provided measures of anisotropic intra-tubular diffusion to serve as a model for intra-axonal water diffusion. Intra- and inter-scanner measurement variances were compared, and the impact on effect size was calculated. Intra-scanner test-retest reliability estimates for fractional anisotropy (FA) demonstrated relative stability over testing intervals. The human tissue and phantom showed similar FA ranges, high linearity and large within-device e...

The neuroradiology journal, 2018

We employed a novel diffusion tensor imaging phantom to study intra- and interscanner reproducibi... more We employed a novel diffusion tensor imaging phantom to study intra- and interscanner reproducibility on two 3T magnetic resonance (MR) scanners. Using a phantom containing thousands of hollow micron-size tubes in complex arrays, we performed two experiments using a b value of 1000 s/ms on two Siemens 3T Trio scanners. First, we performed 12-direction scans. Second, on one scanner, we performed two 64-direction protocols with different repetition times (TRs). We used a one-way analysis of variance to calculate differences between scanners and the Mann-Whitney U test to assess differences between 12-direction and 64-direction data. We calculated the coefficient of variation (CoV) for intrascanner and interscanner data. For 12-direction protocols, mean fractional anisotropy (FA) was 0.3003 for Scanner 1 (four scans) and 0.3094 for Scanner 2 (three scans). Lowest FA value on Scanner 1 was 2.56 standard deviations below the mean of Scanner 2. For 64-direction scans, mean FA was 0.2640 f...

Data in brief, 2018

We provide a comprehensive diffusion MRI dataset acquired with a novel biomimetic phantom mimicki... more We provide a comprehensive diffusion MRI dataset acquired with a novel biomimetic phantom mimicking human white matter. The fiber substrates in the diffusion phantom were constructed from hollow textile axons ("taxons") with an inner diameter of 11.8±1.2 µm and outer diameter of 33.5±2.3 µm. Data were acquired on the 3 T CONNECTOM MRI scanner with multiple diffusion times and multiple q-values per diffusion time, which is a dedicated acquisition for validation of microstructural imaging methods, such as compartment size and volume fraction mapping. Minimal preprocessing was performed to correct for susceptibility and eddy current distortions. Data were deposited in the XNAT Central database (project ID: dMRI_Phant_MGH).

Military medicine, 2018

To determine if targeted, active interventions would improve symptoms and impairment in previousl... more To determine if targeted, active interventions would improve symptoms and impairment in previously intractable patients with chronic mild traumatic brain injury (mTBI). Twenty-six (20 males; 6 females) out of 51 (51%) former military and civilian patients with chronic (1-3 yr) mTBI enrolled in the TEAM traumatic brain injury (TBI) study completed both an initial and 6-mo post-intervention comprehensive mTBI assessment including symptoms (Post-concussion Symptom Scale [PCSS], Dizziness Handicap Inventory [DHI]), cognitive (Immediate Post-concussion Assessment and Cognitive Testing [ImPACT]), vestibular/oculomotor (Vestibular/Ocular Motor Screening [VOMS]), balance (Activities-specific Balance Confidence [ABC] scale, Balance Error Scoring System [BESS]), and cervical (Neck Disability Index [NDI]). Patients were prescribed progressive, targeted interventions and therapies (e.g., behavioral, vestibular, vision, and exertion) that matched their mTBI clinical profile. A series of paired t...

NeuroImage, Jan 12, 2018

Diffusion microstructural imaging techniques have attracted great interest in the last decade due... more Diffusion microstructural imaging techniques have attracted great interest in the last decade due to their ability to quantify axon diameter and volume fraction in healthy and diseased human white matter. The estimates of compartment size and volume fraction continue to be debated, in part due to the lack of a gold standard for validation and quality control. In this work, we validate diffusion MRI estimates of compartment size and volume fraction using a novel textile axon ("taxon") phantom constructed from hollow polypropylene yarns with distinct intra- and extra-taxonal compartments to mimic white matter in the brain. We acquired a comprehensive set of diffusion MRI measurements in the phantom using multiple gradient directions, diffusion times and gradient strengths on a human MRI scanner equipped with maximum gradient strength (G) of 300 mT/m. We obtained estimates of compartment size and restricted volume fraction through a straightforward extension of the AxCaliber/...

ACS Applied Materials & Interfaces

Current brain imaging methods largely fail to provide detailed information about the location and... more Current brain imaging methods largely fail to provide detailed information about the location and severity of axonal injuries and do not anticipate recovery of the patients with traumatic brain injury. High-definition fiber tractography appears as a novel imaging modality based on water motion in the brain that allows for direct visualization and quantification of the degree of axons damage, thus predicting the functional deficits due to traumatic axonal injury and loss of cortical projections. This neuroimaging modality still faces major challenges because it lacks a "gold standard" for the technique validation and respective quality control. The present work aims to study the potential of hollow polypropylene yarns to mimic human white matter axons and construct a brain phantom for the calibration and validation of brain diffusion techniques based on magnetic resonance imaging, including high-definition fiber tractography imaging. Hollow multifilament polypropylene yarns were produced by melt-spinning process and characterized in terms of their physicochemical properties. Scanning electronic microscopy images of the filaments cross section has shown an inner diameter of approximately 12 μm, confirming their appropriateness to mimic the brain axons. The chemical purity of polypropylene yarns as well as the interaction between the water and the filament surface, important properties for predicting water behavior and diffusion inside the yarns, were also evaluated. Restricted and hindered water diffusion was confirmed by fluorescence microscopy. Finally, the yarns were magnetic resonance imaging scanned and analyzed using high-definition fiber tractography, revealing an excellent choice of these hollow polypropylene structures for simulation of the white matter brain axons and their suitability for constructing an accurate brain phantom.

Behavior Research Methods & Instrumentation

Human Factors: The Journal of the Human Factors and Ergonomics Society

Vigilance decrements are interpreted within a two-process (automatic/control) theory of human inf... more Vigilance decrements are interpreted within a two-process (automatic/control) theory of human information processing, and the theoretical components of the normal vigilance curve are discussed in relation to type of processing and amount of practice. Two experiments were conducted showing significant vigilance decrements when subjects utilized effortful control processing; the normal decrement was not observed when effortless automatic processing was possible. Maximum vigilance decrements occur when subjects must continually and redundantly allocate control-processing resources. Results disconfirm the habituation hypothesis. It is concluded that structuring a task such that there is a consistent relationship between signals and noise will reduce vigilance problems. System design implications suggest that tasks should be structured to minimize continuous and repetitive control processing. Methods for developing vigilance-decrement-resistant automatic processing are discussed.

Human Factors: The Journal of the Human Factors and Ergonomics Society

Three groups of subjects, differing in the kinds of augmentation provided, were trained to contro... more Three groups of subjects, differing in the kinds of augmentation provided, were trained to control a continuously moving track in a second-order system. Differences in performance among the three groups occurred only in transfer experiments when subjects were required to apply their knowledge, or their internal model, to solve system problems. These results indicated that subjects in a parabola-augmented group had learned to internalize this cue and mentally manipulate it to solve system problems even when the cue was not displayed. Subjects in the other two groups, a point-augmented group and a nonaugmented control group, used a set of simplifying rules, some correct and others incorrect, to guide their behavior. The results indicated that accurate control of the system does not necessarily imply that the operator's internal model of the system is also accurate. In addition, augmentation that made the system appear consistent was important in the development of an internal model.

Human Factors: The Journal of the Human Factors and Ergonomics Society

Experimental and statistical methods for examining individual differences in dual-task performanc... more Experimental and statistical methods for examining individual differences in dual-task performance and time-sharing ability are reviewed and criticized. Previous data and analysis procedures are generally inadequate to evaluate a time-sharing ability. Errors resulting from unsophisticated use of correlational and factor analytic procedures are described. Four previous studies that concern time-sharing are considered in detail. The nature of task selection, scoring methods, and control of practice and reliability issues are discussed. Based on a reanalysis of available data, a time-sharing ability is not rejected. Simulation, incorporation of theory in planning models, and crucial tests of the hypotheses are proposed as methods for assessing the time-sharing ability.

Human Factors: The Journal of the Human Factors and Ergonomics Society

ABSTRACT

Architectures for Intelligence

Page 1. LE COPY An instructable connectionist/control architecture: Using rule-based instructions... more Page 1. LE COPY An instructable connectionist/control architecture: Using rule-based instructions to accomplish connectionist learning in a human time scale N Technical Report AlP - 95 Walter Schneider and William L. Oliver N ...

: Given the massively parallel nature of the brain an obvious question is why are so many informa... more : Given the massively parallel nature of the brain an obvious question is why are so many information processing functions serial? In particular, this paper addresses the issue of the comparison process. Behavioral data show that in perceptual matching tasks (such as memory scanning and visual search) performance is systematically affected by stimulus load, in that required processing time increases with each additional comparison item. It is arguable whether this indicates a processing system that performs serial comparisons, or a system for which comparisons are done in parallel but reaction time is affected by load because of other system limitations. In this simulation we show that in a modular connectionist system vector transmission is possible in parallel, but the comparison process within a module must be done serially unless accuracy is sacrificed.

It is widely held that there is a distinction between attentive and automatic cognitive processin... more It is widely held that there is a distinction between attentive and automatic cognitive processing. In research on attention using visual search tasks, the detection performance of human subjects in consistent mappingparadigms is generally regarded as indicating a shift, with practice, from serial, attentional, controlled processing to parallel, automatic processing, while detection performance in varied mappingparadigms is taken to indicate that processing remains under attentional control. This paper proposes a priority learningmechanism to model the effects of practice and the development of automaticity, in visual search tasks. A connectionist simulation model implements this learning algorithm. Five prominent features of visual search practice effects are simulated. These are: 1) in consistent mapping tasks, practice reduces processing time, particularly the slope of reaction times as a function of the number of comparisons; 2) in varied mapping tasks, there is no change in the...

Brain injury, 2018

Multisite and longitudinal neuroimaging studies are important in uncovering trajectories of recov... more Multisite and longitudinal neuroimaging studies are important in uncovering trajectories of recovery and neurodegeneration following traumatic brain injury (TBI) and concussion through the use of diffusion tensor imaging (DTI) and other imaging modalities. This study assessed differences in anisotropic diffusion measurement across four scanners using a human and a novel phantom developed in conjunction with the Chronic Effects of Neurotrauma Consortium. Human scans provided measurement within biological tissue, and the novel physical phantom provided measures of anisotropic intra-tubular diffusion to serve as a model for intra-axonal water diffusion. Intra- and inter-scanner measurement variances were compared, and the impact on effect size was calculated. Intra-scanner test-retest reliability estimates for fractional anisotropy (FA) demonstrated relative stability over testing intervals. The human tissue and phantom showed similar FA ranges, high linearity and large within-device e...

The neuroradiology journal, 2018

We employed a novel diffusion tensor imaging phantom to study intra- and interscanner reproducibi... more We employed a novel diffusion tensor imaging phantom to study intra- and interscanner reproducibility on two 3T magnetic resonance (MR) scanners. Using a phantom containing thousands of hollow micron-size tubes in complex arrays, we performed two experiments using a b value of 1000 s/ms on two Siemens 3T Trio scanners. First, we performed 12-direction scans. Second, on one scanner, we performed two 64-direction protocols with different repetition times (TRs). We used a one-way analysis of variance to calculate differences between scanners and the Mann-Whitney U test to assess differences between 12-direction and 64-direction data. We calculated the coefficient of variation (CoV) for intrascanner and interscanner data. For 12-direction protocols, mean fractional anisotropy (FA) was 0.3003 for Scanner 1 (four scans) and 0.3094 for Scanner 2 (three scans). Lowest FA value on Scanner 1 was 2.56 standard deviations below the mean of Scanner 2. For 64-direction scans, mean FA was 0.2640 f...

Data in brief, 2018

We provide a comprehensive diffusion MRI dataset acquired with a novel biomimetic phantom mimicki... more We provide a comprehensive diffusion MRI dataset acquired with a novel biomimetic phantom mimicking human white matter. The fiber substrates in the diffusion phantom were constructed from hollow textile axons ("taxons") with an inner diameter of 11.8±1.2 µm and outer diameter of 33.5±2.3 µm. Data were acquired on the 3 T CONNECTOM MRI scanner with multiple diffusion times and multiple q-values per diffusion time, which is a dedicated acquisition for validation of microstructural imaging methods, such as compartment size and volume fraction mapping. Minimal preprocessing was performed to correct for susceptibility and eddy current distortions. Data were deposited in the XNAT Central database (project ID: dMRI_Phant_MGH).

Military medicine, 2018

To determine if targeted, active interventions would improve symptoms and impairment in previousl... more To determine if targeted, active interventions would improve symptoms and impairment in previously intractable patients with chronic mild traumatic brain injury (mTBI). Twenty-six (20 males; 6 females) out of 51 (51%) former military and civilian patients with chronic (1-3 yr) mTBI enrolled in the TEAM traumatic brain injury (TBI) study completed both an initial and 6-mo post-intervention comprehensive mTBI assessment including symptoms (Post-concussion Symptom Scale [PCSS], Dizziness Handicap Inventory [DHI]), cognitive (Immediate Post-concussion Assessment and Cognitive Testing [ImPACT]), vestibular/oculomotor (Vestibular/Ocular Motor Screening [VOMS]), balance (Activities-specific Balance Confidence [ABC] scale, Balance Error Scoring System [BESS]), and cervical (Neck Disability Index [NDI]). Patients were prescribed progressive, targeted interventions and therapies (e.g., behavioral, vestibular, vision, and exertion) that matched their mTBI clinical profile. A series of paired t...

NeuroImage, Jan 12, 2018

Diffusion microstructural imaging techniques have attracted great interest in the last decade due... more Diffusion microstructural imaging techniques have attracted great interest in the last decade due to their ability to quantify axon diameter and volume fraction in healthy and diseased human white matter. The estimates of compartment size and volume fraction continue to be debated, in part due to the lack of a gold standard for validation and quality control. In this work, we validate diffusion MRI estimates of compartment size and volume fraction using a novel textile axon ("taxon") phantom constructed from hollow polypropylene yarns with distinct intra- and extra-taxonal compartments to mimic white matter in the brain. We acquired a comprehensive set of diffusion MRI measurements in the phantom using multiple gradient directions, diffusion times and gradient strengths on a human MRI scanner equipped with maximum gradient strength (G) of 300 mT/m. We obtained estimates of compartment size and restricted volume fraction through a straightforward extension of the AxCaliber/...

ACS Applied Materials & Interfaces

Current brain imaging methods largely fail to provide detailed information about the location and... more Current brain imaging methods largely fail to provide detailed information about the location and severity of axonal injuries and do not anticipate recovery of the patients with traumatic brain injury. High-definition fiber tractography appears as a novel imaging modality based on water motion in the brain that allows for direct visualization and quantification of the degree of axons damage, thus predicting the functional deficits due to traumatic axonal injury and loss of cortical projections. This neuroimaging modality still faces major challenges because it lacks a "gold standard" for the technique validation and respective quality control. The present work aims to study the potential of hollow polypropylene yarns to mimic human white matter axons and construct a brain phantom for the calibration and validation of brain diffusion techniques based on magnetic resonance imaging, including high-definition fiber tractography imaging. Hollow multifilament polypropylene yarns were produced by melt-spinning process and characterized in terms of their physicochemical properties. Scanning electronic microscopy images of the filaments cross section has shown an inner diameter of approximately 12 μm, confirming their appropriateness to mimic the brain axons. The chemical purity of polypropylene yarns as well as the interaction between the water and the filament surface, important properties for predicting water behavior and diffusion inside the yarns, were also evaluated. Restricted and hindered water diffusion was confirmed by fluorescence microscopy. Finally, the yarns were magnetic resonance imaging scanned and analyzed using high-definition fiber tractography, revealing an excellent choice of these hollow polypropylene structures for simulation of the white matter brain axons and their suitability for constructing an accurate brain phantom.

Behavior Research Methods & Instrumentation

Human Factors: The Journal of the Human Factors and Ergonomics Society

Vigilance decrements are interpreted within a two-process (automatic/control) theory of human inf... more Vigilance decrements are interpreted within a two-process (automatic/control) theory of human information processing, and the theoretical components of the normal vigilance curve are discussed in relation to type of processing and amount of practice. Two experiments were conducted showing significant vigilance decrements when subjects utilized effortful control processing; the normal decrement was not observed when effortless automatic processing was possible. Maximum vigilance decrements occur when subjects must continually and redundantly allocate control-processing resources. Results disconfirm the habituation hypothesis. It is concluded that structuring a task such that there is a consistent relationship between signals and noise will reduce vigilance problems. System design implications suggest that tasks should be structured to minimize continuous and repetitive control processing. Methods for developing vigilance-decrement-resistant automatic processing are discussed.

Human Factors: The Journal of the Human Factors and Ergonomics Society

Three groups of subjects, differing in the kinds of augmentation provided, were trained to contro... more Three groups of subjects, differing in the kinds of augmentation provided, were trained to control a continuously moving track in a second-order system. Differences in performance among the three groups occurred only in transfer experiments when subjects were required to apply their knowledge, or their internal model, to solve system problems. These results indicated that subjects in a parabola-augmented group had learned to internalize this cue and mentally manipulate it to solve system problems even when the cue was not displayed. Subjects in the other two groups, a point-augmented group and a nonaugmented control group, used a set of simplifying rules, some correct and others incorrect, to guide their behavior. The results indicated that accurate control of the system does not necessarily imply that the operator's internal model of the system is also accurate. In addition, augmentation that made the system appear consistent was important in the development of an internal model.

Human Factors: The Journal of the Human Factors and Ergonomics Society

Experimental and statistical methods for examining individual differences in dual-task performanc... more Experimental and statistical methods for examining individual differences in dual-task performance and time-sharing ability are reviewed and criticized. Previous data and analysis procedures are generally inadequate to evaluate a time-sharing ability. Errors resulting from unsophisticated use of correlational and factor analytic procedures are described. Four previous studies that concern time-sharing are considered in detail. The nature of task selection, scoring methods, and control of practice and reliability issues are discussed. Based on a reanalysis of available data, a time-sharing ability is not rejected. Simulation, incorporation of theory in planning models, and crucial tests of the hypotheses are proposed as methods for assessing the time-sharing ability.

Human Factors: The Journal of the Human Factors and Ergonomics Society

ABSTRACT