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Goal-directed control with cortical units that are gated by both top-down feedback and oscillatory coherence.

Kerr RR, Grayden DB, Thomas DA, Gilson M, Burkitt AN - Front Neural Circuits (2014)

Bottom Line: We demonstrate that more sophisticated and flexible top-down control is possible when the gain of units is modulated by not only top-down feedback but by coherence between the activities of the oscillating units.With these types of units, it is possible to not only add units to, or remove units from, a higher-level unit's logic operation using top-down feedback, but also to modify the type of role that a unit plays in the operation.Based on this, we make predictions about the likely connectivities between certain brain regions that have been experimentally observed to be involved in goal-directed behavior and top-down attention.

View Article: PubMed Central - PubMed

Affiliation: NeuroEngineering Laboratory, Department of Electrical and Electronic Engineering, The University of Melbourne Melbourne, VIC, Australia ; Centre for Neural Engineering, The University of Melbourne Melbourne, VIC, Australia ; NICTA, Victoria Research Lab, The University of Melbourne Melbourne, VIC, Australia.

ABSTRACT
The brain is able to flexibly select behaviors that adapt to both its environment and its present goals. This cognitive control is understood to occur within the hierarchy of the cortex and relies strongly on the prefrontal and premotor cortices, which sit at the top of this hierarchy. Pyramidal neurons, the principal neurons in the cortex, have been observed to exhibit much stronger responses when they receive inputs at their soma/basal dendrites that are coincident with inputs at their apical dendrites. This corresponds to inputs from both lower-order regions (feedforward) and higher-order regions (feedback), respectively. In addition to this, coherence between oscillations, such as gamma oscillations, in different neuronal groups has been proposed to modulate and route communication in the brain. In this paper, we develop a simple, but novel, neural mass model in which cortical units (or ensembles) exhibit gamma oscillations when they receive coherent oscillatory inputs from both feedforward and feedback connections. By forming these units into circuits that can perform logic operations, we identify the different ways in which operations can be initiated and manipulated by top-down feedback. We demonstrate that more sophisticated and flexible top-down control is possible when the gain of units is modulated by not only top-down feedback but by coherence between the activities of the oscillating units. With these types of units, it is possible to not only add units to, or remove units from, a higher-level unit's logic operation using top-down feedback, but also to modify the type of role that a unit plays in the operation. Finally, we explore how different network properties affect top-down control and processing in large networks. Based on this, we make predictions about the likely connectivities between certain brain regions that have been experimentally observed to be involved in goal-directed behavior and top-down attention.

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Goal-directed Network. An illustration of the proposed cortical architecture. Sensory, feedforward input (left) is mapped to percepts, actions, and finally motor responses (right), and this mapping is controlled by goal-dependent feedback (top). In the diagram, blue, red, and magenta arrows correspond to feedforward, internal feedback and external feedback (feedback corresponding to the goals of the system) connections, respectively. It should be noted that only the connections from active or searching units have been shown and they would exist other connections which have not been shown. White, green, and red units correspond to resting, active, and searching units, respectively.
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Figure 2: Goal-directed Network. An illustration of the proposed cortical architecture. Sensory, feedforward input (left) is mapped to percepts, actions, and finally motor responses (right), and this mapping is controlled by goal-dependent feedback (top). In the diagram, blue, red, and magenta arrows correspond to feedforward, internal feedback and external feedback (feedback corresponding to the goals of the system) connections, respectively. It should be noted that only the connections from active or searching units have been shown and they would exist other connections which have not been shown. White, green, and red units correspond to resting, active, and searching units, respectively.

Mentions: In this paper, we consider that the previously defined cortical units are organized into architectures similar to that presented in Figure 2. Here, the system receives sensory inputs (left) and produces motor outputs (right). Units in the system represent abstract concepts, such as percepts and actions, that depend on the sensory inputs and determine the behavior, respectively. In Figure 2, we divided the architecture into levels (using vertical black lines). These levels embody a hierarchy in the processing of information. Feedforward connections are made from units in lower levels to units in higher levels while the reverse is true for feedback connections. Here, the number of levels depicted is arbitrary and for illustrative purposes; the actual number of levels is most likely much greater. Similarly, the multiple vertical lines between the sensory and the percepts, and between the actions and motor, are only intended to indicate that there would be a number of levels of processing (e.g., for the visual pathway: those in the retina, LGN, V1, etc.) in between. The levels aim to convey the idealized version of the functional architecture that we consider in this paper.


Goal-directed control with cortical units that are gated by both top-down feedback and oscillatory coherence.

Kerr RR, Grayden DB, Thomas DA, Gilson M, Burkitt AN - Front Neural Circuits (2014)

Goal-directed Network. An illustration of the proposed cortical architecture. Sensory, feedforward input (left) is mapped to percepts, actions, and finally motor responses (right), and this mapping is controlled by goal-dependent feedback (top). In the diagram, blue, red, and magenta arrows correspond to feedforward, internal feedback and external feedback (feedback corresponding to the goals of the system) connections, respectively. It should be noted that only the connections from active or searching units have been shown and they would exist other connections which have not been shown. White, green, and red units correspond to resting, active, and searching units, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4126059&req=5

Figure 2: Goal-directed Network. An illustration of the proposed cortical architecture. Sensory, feedforward input (left) is mapped to percepts, actions, and finally motor responses (right), and this mapping is controlled by goal-dependent feedback (top). In the diagram, blue, red, and magenta arrows correspond to feedforward, internal feedback and external feedback (feedback corresponding to the goals of the system) connections, respectively. It should be noted that only the connections from active or searching units have been shown and they would exist other connections which have not been shown. White, green, and red units correspond to resting, active, and searching units, respectively.
Mentions: In this paper, we consider that the previously defined cortical units are organized into architectures similar to that presented in Figure 2. Here, the system receives sensory inputs (left) and produces motor outputs (right). Units in the system represent abstract concepts, such as percepts and actions, that depend on the sensory inputs and determine the behavior, respectively. In Figure 2, we divided the architecture into levels (using vertical black lines). These levels embody a hierarchy in the processing of information. Feedforward connections are made from units in lower levels to units in higher levels while the reverse is true for feedback connections. Here, the number of levels depicted is arbitrary and for illustrative purposes; the actual number of levels is most likely much greater. Similarly, the multiple vertical lines between the sensory and the percepts, and between the actions and motor, are only intended to indicate that there would be a number of levels of processing (e.g., for the visual pathway: those in the retina, LGN, V1, etc.) in between. The levels aim to convey the idealized version of the functional architecture that we consider in this paper.

Bottom Line: We demonstrate that more sophisticated and flexible top-down control is possible when the gain of units is modulated by not only top-down feedback but by coherence between the activities of the oscillating units.With these types of units, it is possible to not only add units to, or remove units from, a higher-level unit's logic operation using top-down feedback, but also to modify the type of role that a unit plays in the operation.Based on this, we make predictions about the likely connectivities between certain brain regions that have been experimentally observed to be involved in goal-directed behavior and top-down attention.

View Article: PubMed Central - PubMed

Affiliation: NeuroEngineering Laboratory, Department of Electrical and Electronic Engineering, The University of Melbourne Melbourne, VIC, Australia ; Centre for Neural Engineering, The University of Melbourne Melbourne, VIC, Australia ; NICTA, Victoria Research Lab, The University of Melbourne Melbourne, VIC, Australia.

ABSTRACT
The brain is able to flexibly select behaviors that adapt to both its environment and its present goals. This cognitive control is understood to occur within the hierarchy of the cortex and relies strongly on the prefrontal and premotor cortices, which sit at the top of this hierarchy. Pyramidal neurons, the principal neurons in the cortex, have been observed to exhibit much stronger responses when they receive inputs at their soma/basal dendrites that are coincident with inputs at their apical dendrites. This corresponds to inputs from both lower-order regions (feedforward) and higher-order regions (feedback), respectively. In addition to this, coherence between oscillations, such as gamma oscillations, in different neuronal groups has been proposed to modulate and route communication in the brain. In this paper, we develop a simple, but novel, neural mass model in which cortical units (or ensembles) exhibit gamma oscillations when they receive coherent oscillatory inputs from both feedforward and feedback connections. By forming these units into circuits that can perform logic operations, we identify the different ways in which operations can be initiated and manipulated by top-down feedback. We demonstrate that more sophisticated and flexible top-down control is possible when the gain of units is modulated by not only top-down feedback but by coherence between the activities of the oscillating units. With these types of units, it is possible to not only add units to, or remove units from, a higher-level unit's logic operation using top-down feedback, but also to modify the type of role that a unit plays in the operation. Finally, we explore how different network properties affect top-down control and processing in large networks. Based on this, we make predictions about the likely connectivities between certain brain regions that have been experimentally observed to be involved in goal-directed behavior and top-down attention.

Show MeSH