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O S Vinogradova - One of the best experts on this subject based on the ideXlab platform.
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hippocampus as Comparator role of the two input and two output Systems of the hippocampus in selection and registration of information
Hippocampus, 2001Co-Authors: O S VinogradovaAbstract:Processing of multimodal sensory information by the morphological subdivisions of the hippocampus and its input and output structures was investigated in unanesthetized rabbits by extracellular recording of neuronal activity. Analysis shows principal differences between CA3 neurons with uniform multimodal, mainly inhibitory, rapidly habituating sensory responses, and CA1-subicular neurons, substantial parts of which have phasic reactions and patterned on-responses, depending on the characteristics of the stimuli. These differences result from the organization of the afferent inputs to CA1 and CA3. Analysis of neuronal responses in sources of hippocampal inputs, their electrical stimulation, and chronic disconnection show the greater functional significance of the brain-stem reticular input for tonic responses characteristic of CA3. This input signal before entering the hippocampus is additionally preprocessed at the MS-DB relay, where it becomes more uniform and frequency-modulated in the range of theta-rhythm. It is shown that the new sensory stimuli produce inhibitory reset, after which synchronized theta-modulation is triggered. Other stimuli, appearing at the background of the ongoing theta, do not evoke any responses of the hippocampal neurons. Thus, theta-modulation can be regarded as a mechanism of attention, which prolongs response to a selected stimulus and simultaneously protects its processing against interference. The cortical input of the hippocampus introduces highly differentiated information analyzed at the highest levels of the neocortex through the intermediary of the entorhinal cortex and presubiculum. However, only CA1-subiculum receives this information directly; before its entrance into CA3, it is additionally preprocessed at the FD relay, where the secondary simplification of signals occurs. As a result, CA3 receives by its two inputs (MS-DB and FD) messages just about the presence and level of input signals in each of them, and performs relatively simple functions of determination of match/mismatch of their weights. For this Comparator System, the presence of signal only in the reticulo-septal input is equivalent to quality of novelty. The cortical signal appears with some delay, after its analysis in the neocortex and shaping in the prehippocampal structures; besides, it is gradually increased due to LTP-like incremental changes in PP and mossy fiber synapses. The CA3 neurons with potentiated synapses of cortical input do not respond to sensory stimuli; that is, the increased efficacy of the cortical signals can be regarded as "familiarity" of a signal, terminating the reactive state of the CA3 neurons. The integrity of both inputs is necessary for gradual habituation of sensory responses in the hippocampus. The output signals of CA3 following in the precommissural fornix to the output relay-LS nucleus and to the brain-stem structures have strong regulatory influence on the level of brain activity (arousal), which is an important condition for processing and registration of information. The primary targets of this output signal are raphe nuclei, which suppress activity of the ascending excitatory RF. In the background state, activity of the CA3 neurons through the intermediary of raphe keeps RF under tonic inhibitory control. Inhibition of the majority of CA3 pyramidal neurons during a novel stimulus action decreases the volume of its output signal to raphe and releases RF from tonic inhibition (increase in level of activity of the forebrain, arousal). When the responses of CA3 neurons habituate, the initial high background activity is reinstated, as well as tonic suppression of RF. Analysis of the second output of CA3 (by Schaffer's collaterals to CA1) shows that activity in this pathway can block access of cortical signals from PP to CA1 neurons by action upon the local System of inhibitory neurons, or by shunting the propagation of signals in apical dendrites. Thus, CA3 can act as a filter controlling the information transmission by CA1; such transmission at any given moment is allowed only in those CA1 neurons which receive SC from CA3 neurons, responding to the sensory stimulus by suppression of their activity. Disconnection of the CA3 output fibers results in disappearance of habituation in all its target structures (raphe, RF, CA1). The output signal of CA1-subiculum follows by postcommissural fornix to the chain of structures of the main limbic circuit: mammillary bodies (medial nucleus), anterior thalamic nuclei (mainly antero-ventral nucleus), and cingulate limbic cortex (mainly posterior area). In each of these links, the signal is additionally processed. Habituation is nearly absent in these structures; instead, st
Antonio Rangel - One of the best experts on this subject based on the ideXlab platform.
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the decision value computations in the vmpfc and striatum use a relative value code that is guided by visual attention
The Journal of Neuroscience, 2011Co-Authors: Seunglark Lim, John P Odoherty, Antonio RangelAbstract:There is a growing consensus in behavioral neuroscience that the brain makes simple choices by first assigning a value to the options under consideration and then comparing them. Two important open questions are whether the brain encodes absolute or relative value signals, and what role attention might play in these computations. We investigated these questions using a human fMRI experiment with a binary choice task in which the fixations to both stimuli were exogenously manipulated to control for the role of visual attention in the valuation computation. We found that the ventromedial prefrontal cortex and the ventral striatum encoded fixation-dependent relative value signals: activity in these areas correlated with the difference in value between the attended and the unattended items. These attention-modulated relative value signals might serve as the input of a Comparator System that is used to make a choice.
Clemens Becker - One of the best experts on this subject based on the ideXlab platform.
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validity reliability and feasibility of the usense activity monitor to register physical activity and gait performance in habitual settings of geriatric patients
Physiological Measurement, 2019Co-Authors: Martin Bongartz, Rainer Kiss, Andre Lacroix, Tobias Eckert, Phoebe Ullrich, Carlphilipp Jansen, Manuel Feist, Sabato Mellone, Lorenzo Chiari, Clemens BeckerAbstract:Objective The aim of the study was to investigate the psychometric quality of a newly developed activity monitor (uSense) to document established physical activity parameters as well as innovative qualitative and quantitative gait characteristics in geriatric patients. Approach Construct and concurrent validity, test-retest reliability, and feasibility of established as well as innovative characteristics for qualitative gait analysis were analyzed in multi-morbid, geriatric patients with cognitive impairment (CI) (n = 110), recently discharged from geriatric rehabilitation. Main results Spearman correlations of established and innovative uSense parameters reflecting active behavior with clinically relevant construct parameters were on average moderate to high for motor performance and life-space and low to moderate for other parameters, while correlations with uSense parameters reflecting inactive behavior were predominantly low. Concurrent validity of established physical activity parameters showed consistently high correlations between the uSense and an established Comparator System (PAMSys™), but the absolute agreement between both sensor Systems was low. On average excellent test-retest reliability for all uSense parameters and good feasibility could be documented. Significance The uSense monitor allows the assessment of established and-for the first time-a semi-qualitative gait assessment of habitual activity behavior in older persons most affected by motor and CI and activity restrictions. On average moderate to good construct validity, high test-retest reliability, and good feasibility indicated a sound psychometric quality of most measures, while the results of concurrent validity as measured by a comparable System indicated high correlation but low absolute agreement based on different algorithms used.
Seunglark Lim - One of the best experts on this subject based on the ideXlab platform.
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the decision value computations in the vmpfc and striatum use a relative value code that is guided by visual attention
The Journal of Neuroscience, 2011Co-Authors: Seunglark Lim, John P Odoherty, Antonio RangelAbstract:There is a growing consensus in behavioral neuroscience that the brain makes simple choices by first assigning a value to the options under consideration and then comparing them. Two important open questions are whether the brain encodes absolute or relative value signals, and what role attention might play in these computations. We investigated these questions using a human fMRI experiment with a binary choice task in which the fixations to both stimuli were exogenously manipulated to control for the role of visual attention in the valuation computation. We found that the ventromedial prefrontal cortex and the ventral striatum encoded fixation-dependent relative value signals: activity in these areas correlated with the difference in value between the attended and the unattended items. These attention-modulated relative value signals might serve as the input of a Comparator System that is used to make a choice.
Mahfouf M. - One of the best experts on this subject based on the ideXlab platform.
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Inspection by exception: a new machine learning-based approach for multistage manufacturing
'Elsevier BV', 2020Co-Authors: Papananias M., Obajemu O., Mcleay T.e., Mahfouf M.Abstract:Manufacturing processes usually consist of multiple different stages, each of which is influenced by a multitude of factors. Therefore, variations in product quality at a certain stage are contributed to by the errors generated at the current, as well as preceding, stages. The high cost of each production stage in the manufacture of high-quality products has stimulated a drive towards decreasing the volume of non-added value processes such as inspection. This paper presents a new method for what the authors have referred to as ‘inspection by exception’ – the principle of actively detecting and then inspecting only the parts that cannot be categorized as healthy or unhealthy with a high degree of certainty. The key idea is that by inspecting only those parts that are in the corridor of uncertainty, the volume of inspections are considerably reduced. This possibility is explored using multistage manufacturing data and both unsupervised and supervised learning algorithms. A case study is presented whereby material conditions and time domain features for force, vibration and tempering temperature are used as input data. Fuzzy C-Means (FCM) clustering is implemented to achieve inspection by exception in an unsupervised manner based on the normalized Euclidean distances between the principal components and cluster centres. Also, deviation vectors for product health are obtained using a Comparator System to train neural networks for supervised learning-based inspection by exception. It is shown that the volume of inspections can be reduced by as much as 82% and 93% using the unsupervised and supervised learning approaches, respectively