Browsing by Subject "Hierarchical control"

Now showing 1 - 4 of 4

Open Access
Hierarchical instantiation of attention
(2022-10) Giray, İrem
Extended task executions involve goal-directed programs that control the execution of component steps. While the presence of such programs is widely accepted, their nature remains unclear. Prior studies saw them as controlling the identity and sequence of individual steps much like how a recipe controls and organizes cooking. However, this can happen only in predictable tasks where the identity and sequence of steps are known beforehand. Programs, on the other hand, are also evident in unpredictable tasks where the identity and sequence of steps are not foreknown. What is the role of these programs in such tasks? It has been suggested that, contrary to existing view, these programs may not be about specifying the identity and sequence of component steps. Perhaps they are the means of instantiating all kinds of goal-related control processes during extended tasks. We tested this thesis in relation to attention. If attention during extended tasks is instantiated via these programs, then attentional focus may be poorer on the initial steps of such tasks, especially if these steps are fast-paced. This is because when a new task starts a new program is needed. If attention can only be instantiated via these programs, then the initial steps cannot be attended unless the new program is in place. However, in fast-paced tasks the initial steps may be at hand before these programs have been assembled. Consequently, these steps may suffer from a lack of attention. We show that attention-dependent inhibitory control is indeed poorer on the initial steps of extended tasks, suggesting that attention may indeed be instantiated via these programs.
Open Access
Investigation of how task related programs affect activation of frontoparietal regions
(2023-01) Çiftçi, İpek
We prepare breakfast, take a shower, do grocery shopping. While completing these daily goals we don’t individually execute many components. For instance, while preparing instant coffee we sequentially execute subtask such as ’take the coffee, boil water, put coffee and water to a mug, take a spoon, mix it with spoon’ under the goal of preparing the coffee but we don’t individually execute them. We execute this whole temporally extended task as one entity which is called ’preparing instant coffee’ in this example. We execute a temporally extended, goal-directed behavior as one entity. The construction of this extended behavior in cognition is hierarchical since it consists of subtasks that complete the subgoals in different levels. For example, the step ’put coffee and water to a mug’ completes the subgoal of putting necessary ingredients together. Mixing them completes the actual goal. In terms of goal completion, former one is in a lower level than latter one. Execution of extended behavior that subsumes the entire task occurs via programs. Programs are related to the entire task. These programs are constructed in the beginning of episode. A program of a longer task requires larger programs than same but shorter task. Executing a longer task as one entity is more demanding than a shorter task. So, the program load of the longer task higher than the shorter one. it has been shown that the reaction time of the first item in a longer task is greater than the same but a shorter task [1]. A set of fronto-parietal regions (also known as Multiple Demands (MD) regions) activates in response to goal-directed tasks that require cognitive control and attention. Activation in MD regions higher for more demanding tasks. Demanding task here can be the tasks that have more working memory load or requires more cognitive control demands. In other words, a higher cognitive load is associated with higher activity in MD regions. Can it be a different cognitive load processing differently than the defined above? If the program loads differently than the typical cognitive load defined in the literature, the activity pattern in MD regions should be different than the typical effect of cognitive load in MD regions. In this study, we investigated this issue. In the experiment, participants executed 3-back task in 2 conditions. One condition had high working memory load (high cognitive control demands) and high program load. The other condition had low working memory load (low cognitive control demands) and low program load. Results showed that activity in low working memory load conditions in MD regions was higher than the activity in high working memory load condition. This indicates that the program load has different construction from working memory load because, it reflects different pattern of activity in MD regions.
Open Access
Nonlinear hierarchical control of a quad tilt-wing UAV: An adaptive control approach
(John Wiley and Sons Ltd, 2017) Yildiz, Y.; Unel, M.; Demirel, A.E.
In this paper, a nonlinear hierarchical adaptive control framework is proposed for the control of a quad tilt-wing unmanned aerial vehicle (UAV). An outer loop model reference adaptive controller with robustifying terms creates required forces to be able to move the UAV on a reference trajectory, and an inner loop nonlinear adaptive controller realizes the required attitude angles to achieve these forces. A rigorous stability analysis is provided showing the boundedness of all the signals in this cascaded controller structure. The development and the stability analysis of the controller do not use any linearizations and use the full nonlinear UAV dynamics. The controller is implemented on a high-fidelity nonlinear tilt-wing quadrotor model in the presence of uncertainties, wind disturbances, and measurement noise as well as actuator and structural failures. In this work, in addition to earlier modeling studies, the effect of wing-angle variations, actuator failures, and structural failures and their effect on the center of gravity of the UAV are rigorously and systematically investigated and reflected in the model. Simulation results showing the performance of the proposed controller and a comparison with the fixed controller used in earlier studies are presented in the paper. Copyright © 2017 John Wiley & Sons, Ltd.
Open Access
Working memory capacity: concurrent subtasks need not interfere
(2022-10) Şengil, Gülsüm Özge
Any extended task episode is subsumed by goal-directed programs that hierar- chically control its execution. We investigated the relationship between working memory capacity and the control instantiated by such hierarchical task entities across four experiments. In a new extended task consisting of subtask A and subtask B, participants first memorized the orientation of subtask A lines (let’s call this event mA), then memorized subtask B lines (mB), then recalled these B lines (rB), and finally recalled A lines (rA). The task structure was: mA-mB-rB- rA. Subtask A lines were thus held in mind during the execution of subtask B. Even though participants had to remember the orientation of lines in both cases, increased WM load of lines A only affected performance on subtask A and did not affect the performance on subtask B. In Experiment 2, four trials of Exp1 were organized into a complex 4-part task with the added condition that A lines of a part be recalled not in that part but in the next part. The task structure was: mA1-mB1-rB1—mA2-mB2-rB2-rA1—mA3-mB3-rB3-rA2—mB3-rB3-rA3. Load of A lines again did not affect B lines. Crucially, load of A2 and A3 lines did not affect the recall of A1 and A2 lines, respectively. In Experiment 3, in a design similar to Exp1, time constraint on mA and mB increased the interference across concurrent subtasks. Experiment 4 showed that increasing the similarity between subtask A and subtask B of Exp1 may increase the across-subtask in terference. We show that WM information of different concurrent subtasks can be maintained separately, perhaps as part of their goal-directed programs. And, encoding to these non-interfering stores, as well as retrieval from them, might depend on attentional and time-based mechanisms.