scholarly journals Two-phase model of the basal ganglia: implications for discontinuous control of the motor system

2014 ◽  
Vol 369 (1655) ◽  
pp. 20130489 ◽  
Author(s):  
John Lisman
Keyword(s):  
Basal Ganglia ◽  
Motor System ◽  
Selection Process ◽  
Action Selection ◽  
Positive Outcome ◽  
Second Phase ◽  
Two Phase ◽  
Single Action ◽  
Eligibility Trace

In this article, I point out that simple one-phase models of the role of the basal ganglia in action selection have a problem. Furthermore, I suggest a solution with major implications for the organization of the action-selection and motor systems. In current models, the striatum evaluates multiple potential actions by adding biases based on previous conditioning. These biases may arise in both the direct (bias for) and indirect (bias against) pathways. Together, these biases influence which action is ultimately chosen. For efficient conditioning to occur, a positive outcome must selectively strengthen the striatal bias for the chosen action (via a dopaminergic mechanism). This is problematic, however, because all potential action choices have influenced firing patterns in striatal cells during the selection process; it is therefore unclear how the synapses that represent the chosen plan could be selectively strengthened. I suggest a simple solution in which the striatum has two functional phases. In the first phase, the basal ganglia provide biases for multiple potential actions (using both the direct and indirect pathways), leading to the choice of a single action in the cortex. In the second phase, an efference copy of the chosen action is sent to the striatum, where it contributes to the establishment of the eligibility trace for that action. This trace, when acted on by subsequent dopaminergic reinforcement, leads to specific strengthening of the bias only for the chosen action. Consistent with this model, recordings show post-choice imposition onto the striatum of signals corresponding to the chosen action. The existence of dual phases of basal ganglia function implies that decisions about action choice are sent to the motor system in a discontinuous manner. This would not be problematic if the motor system also operated discontinuously. I will review evidence suggesting that this is the case, notably that action is organized by approximately 10 Hz oscillations.

Interaction between cognitive and motor cortico-basal ganglia loops during decision making: a computational study

2013 ◽  
Vol 109 (12) ◽  
pp. 3025-3040 ◽  
Author(s):  
M. Guthrie ◽  
A. Leblois ◽  
A. Garenne ◽  
T. Boraud
Keyword(s):  
Decision Making ◽  
Basal Ganglia ◽  
Computational Study ◽  
Selection Process ◽  
Action Selection ◽  
External Input ◽  
Projection Neurons ◽  
Cognitive Level ◽  
Striatal Projection Neurons ◽  
Previous Modeling Study

In a previous modeling study, Leblois et al. (2006) demonstrated an action selection mechanism in cortico-basal ganglia loops based on competition between the positive feedback, direct pathway through the striatum and the negative feedback, hyperdirect pathway through the subthalamic nucleus. The present study investigates how multiple level action selection could be performed by the basal ganglia. To do this, the model is extended in a manner consistent with known anatomy and electrophysiology in three main areas. First, two-level decision making has been incorporated, with a cognitive level selecting based on cue shape and a motor level selecting based on cue position. We show that the decision made at the cognitive level can be used to bias the decision at the motor level. We then demonstrate that, for accurate transmission of information between decision-making levels, low excitability of striatal projection neurons is necessary, a generally observed electrophysiological finding. Second, instead of providing a biasing signal between cue choices as an external input to the network, we show that the action selection process can be driven by reasonable levels of noise. Finally, we incorporate dopamine modulated learning at corticostriatal synapses. As learning progresses, the action selection becomes based on learned visual cue values and is not interfered with by the noise that was necessary before learning.

scholarly journals Judging Expertise Through Communication Styles in Intercultural Collaboration

2019 ◽  
Vol 33 (2) ◽  
pp. 238-271 ◽  
Author(s):  
Y. Connie Yuan ◽  
Wang Liao ◽  
Natalya N. Bazarova
Keyword(s):  
Cultural Differences ◽  
Chinese Students ◽  
Communication Styles ◽  
Second Phase ◽  
Two Phase ◽  
Intercultural Collaboration ◽  
Phase Study ◽  
Expertise Recognition ◽  
Task Oriented

Recent research on expertise management calls for more attention to the role of communication in expertise recognition. Cultural differences in communication styles can complicate communication of expertise and consequently make expertise recognition more difficult in mixed-culture groups than in same-culture groups. This article reports results from a two-phase study (348 Chinese and non-Asian U.S. citizen [NAUSC] students in the first phase, and 24 four-person groups that consist of both NAUSC and Chinese students in the second phase) on the role of communication styles in intercultural collaboration. The results suggest that for both Chinese and NAUSC students, conversational control, tenseness, task-oriented communication, and confidence are important cues influencing expertise judgment, but perceived expertise and actual expertise may be unrelated to each other.

A Data Mining Model for Risk Assessment and Customer Segmentation in the Insurance Industry

2013 ◽  
Vol 4 (1) ◽  
pp. 52-78 ◽  
Author(s):  
Payam Hanafizadeh ◽  
Neda Rastkhiz Paydar
Keyword(s):  
Selection Process ◽  
Insurance Industry ◽  
Customer Segmentation ◽  
Insurance Companies ◽  
Second Phase ◽  
Self Organizing Map ◽  
Two Phase ◽  
Self Organizing Maps ◽  
Car Insurance ◽  
Self Organizing

Customer segmentation on the basis of predictable risks can help insurance firms maximize their earnings and minimize their losses. Car insurance is one of the most lucrative and profitable branches in the insurance industry. Utilizing the concept of self-organizing map, the authors propose a two-phase model called ‘Auto Insurance Customers Segmentation Intelligent Tool’ to segment customers in insurance companies on basis of risk. In the first phase, the authors extract 18 risk factors in four categories consisting of demographic specifications, auto specifications, policy specifications, and the driver’s record extracted from the literature review. In the second phase, they finalize the selection process by drawing on expert opinion polls. The authors utilize self-organizing maps since they are able to display the output in the form of illustrative and comprehensible graphical maps capable of representing linear and non-linear relationships among variables, insensitive to the learning input, and slightly sensitive to the noise in the learning input. Finally, K-means are employed to compare the results with those obtained through self-organizing maps.

Coarsening of second phase in a two-phase Zr–2.5Nb: On the role of phase boundaries

2009 ◽  
Vol 57 (19) ◽  
pp. 5812-5821 ◽  
Author(s):  
V.D. Hiwarkar ◽  
S.K. Sahoo ◽  
K.V. Mani krishna ◽  
I. Samajdar ◽  
G.K. Dey ◽  
...  
Keyword(s):  
Second Phase ◽  
Phase Boundaries ◽  
Two Phase

scholarly journals Assessing Selectivity in the Basal Ganglia: The “Gearbox” Hypothesis

2017 ◽  
Author(s):  
Zafeirios Fountas ◽  
Murray Shanahan
Keyword(s):  
Basal Ganglia ◽  
Brain Region ◽  
Selection Process ◽  
Neural Model ◽  
Theoretical Work ◽  
Action Selection ◽  
Mode Switching ◽  
Low Frequencies ◽  
Cortical Areas ◽  
The Impact

AbstractDespite experimental evidence, the literature so far contains no systematic attempt to address the impact of cortical oscillations on the ability of the basal ganglia (BG) to select. In this study, we employed a state-of-the-art spiking neural model of the BG circuitry and investigated the effectiveness of this circuitry as an action selection device. We found that cortical frequency, phase, dopamine and the examined time scale, all have a very important impact on this process. Our simulations resulted in a canonical profile of selectivity, termed selectivity portraits, which suggests that the cortex is the structure that determines whether selection will be performed in the BG and what strategy will be utilized. Some frequency ranges promote the exploitation of highly salient actions, others promote the exploration of alternative options, while the remaining frequencies halt the selection process. Based on this behaviour, we propose that the BG circuitry can be viewed as the “gearbox” of action selection. Coalitions of rhythmic cortical areas are able to switch between a repertoire of available BG modes which, in turn, change the course of information flow within the cortico-BG-thalamo-cortical loop. Dopamine, akin to “control pedals”, either stops or initiates a decision, while cortical frequencies, as a “gear lever”, determine whether a decision can be triggered and what type of decision this will be. Finally, we identified a selection cycle with a period of around 200ms, which was used to assess the biological plausibility of the popular cognitive architectures.Author summaryOur brains are continuously called to select the most appropriate action between alternative competing choices. A plethora of evidence and theoretical work indicates that a fundamental brain region called the basal ganglia might be the locus where this competition occurs. But how is the winning choice determined each time? Using a detailed computational model, based on neurophysiological properties of this region, we suggest that, whereas the basal ganglia might indeed contain the circuitry of action selection, the cerebral cortex is, in fact, the brain region that dictates this process. Similarly to a gearbox in a car, the basal ganglia provide modes for the exploitation of the safest option (forward gears), exploration of alternative options (reverse gear) and a neutral state, in case that the selection process needs to be halted. Our results further indicate that the instructions for mode-switching are relayed to the basal ganglia through specific low frequencies of oscillations within cortical areas. Finally, we provide estimations for the frequency ranges that can be used to activate each selectivity mode, as well as the duration of the selection process under various conditions.

Linguistic precocity and the development of reading: The role of extralinguistic factors

1995 ◽  
Vol 16 (2) ◽  
pp. 173-187 ◽  
Author(s):  
Philip S. Dale ◽  
Catherine Crain-Thoreson ◽  
Nancy M. Robinson
Keyword(s):  
Reading Instruction ◽  
Reading Development ◽  
Literacy Skills ◽  
Book Reading ◽  
Second Phase ◽  
Language And Literacy ◽  
Two Phase ◽  
Verbal Abilities ◽  
Superior Level

ABSTRACTThe language and literacy skills of 21 children (aged 6;6), who were selected for linguistic precocity at age 1;8, are reported here. Verbal abilities remained high, and in contrast to the findings at 4;6 (reported in Crain-Thoreson & Dale, 1992), reading achievement is now at a superior level. Overall, the results are consistent with a two-phase model of reading development, in which the second phase is more closely related to language ability than the first. Phonological awareness, as indexed by a phoneme deletion task, appears to emerge as a consequence, rather than a cause, of early reading. There also appears to be a complex relationship among early interest in reading, instruction, and reading development. Differences in child interest in books and book reading may evoke variation in literacy-relevant experiences.

scholarly journals A Compression-Based Toolkit for Modelling and Processing Natural Language Text

Information ◽  
2018 ◽  
Vol 9 (12) ◽  
pp. 294 ◽  
Author(s):  
William Teahan
Keyword(s):  
Natural Language ◽  
Model Building ◽  
Channel Model ◽  
Text Processing ◽  
Training Model ◽  
Second Phase ◽  
Two Phase ◽  
Natural Language Text ◽  
Language Text

A novel compression-based toolkit for modelling and processing natural language text is described. The design of the toolkit adopts an encoding perspective—applications are considered to be problems in searching for the best encoding of different transformations of the source text into the target text. This paper describes a two phase `noiseless channel model’ architecture that underpins the toolkit which models the text processing as a lossless communication down a noise-free channel. The transformation and encoding that is performed in the first phase must be both lossless and reversible. The role of the verification and decoding second phase is to verify the correctness of the communication of the target text that is produced by the application. This paper argues that this encoding approach has several advantages over the decoding approach of the standard noisy channel model. The concepts abstracted by the toolkit’s design are explained together with details of the library calls. The pseudo-code for a number of algorithms is also described for the applications that the toolkit implements including encoding, decoding, classification, training (model building), parallel sentence alignment, word segmentation and language segmentation. Some experimental results, implementation details, memory usage and execution speeds are also discussed for these applications.

A Dictionary of Affect in Language: I. Establishment and Preliminary Validation

1984 ◽  
Vol 59 (3) ◽  
pp. 695-698 ◽  
Author(s):  
Kevin Sweeney ◽  
Cynthia Whissell
Keyword(s):  
Positive Outcome ◽  
Second Phase ◽  
High Activation ◽  
Two Phase ◽  
Locus Of Causality ◽  
Preliminary Validation ◽  
Affective Dimensions ◽  
Normally Distributed

73 subjects participated in a two-phase experiment. In the first phase, 33 subjects rated more than 4000 words in terms of the affective dimensions of Evaluation (Pleasantness) and Activation (Arousal). Mean scores for the words were normally distributed on both dimensions, and the correlation between dimensions was very low (.15). In the second phase, 40 subjects responded in a free written format to four “imaginary” situations distinguished by their Outcome (“A” Grade, Failing Grade) and their implied Locus of Causality (Internal or Self, External or Other). Ratings from the words in Phase One were used to score subjects' protocols for both dimensions, and greater pleasantness was evident for the positive outcome and the internally-attributed situations while greater arousal was evident for externally attributed situations; data were the frequencies of occurrence of high Activation and high Evaluation words.

scholarly journals A Biologically Inspired Computational Model of Basal Ganglia in Action Selection

2015 ◽  
Vol 2015 ◽  
pp. 1-24 ◽  
Author(s):  
Chiara Baston ◽  
Mauro Ursino
Keyword(s):  
Basal Ganglia ◽  
Previous History ◽  
Action Selection ◽  
Dopamine Depletion ◽  
Behavioral Experiments ◽  
Biologically Inspired ◽  
Cholinergic Interneurons ◽  
Hebb Rule ◽  
History Of

The basal ganglia (BG) are a subcortical structure implicated in action selection. The aim of this work is to present a new cognitive neuroscience model of the BG, which aspires to represent a parsimonious balance between simplicity and completeness. The model includes the 3 main pathways operating in the BG circuitry, that is, the direct (Go), indirect (NoGo), and hyperdirect pathways. The main original aspects, compared with previous models, are the use of a two-term Hebb rule to train synapses in the striatum, based exclusively on neuronal activity changes caused by dopamine peaks or dips, and the role of the cholinergic interneurons (affected by dopamine themselves) during learning. Some examples are displayed, concerning a few paradigmatic cases: action selection in basal conditions, action selection in the presence of a strong conflict (where the role of the hyperdirect pathway emerges), synapse changes induced by phasic dopamine, and learning new actions based on a previous history of rewards and punishments. Finally, some simulations show model working in conditions of altered dopamine levels, to illustrate pathological cases (dopamine depletion in parkinsonian subjects or dopamine hypermedication). Due to its parsimonious approach, the model may represent a straightforward tool to analyze BG functionality in behavioral experiments.

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