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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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Orchestrated Operations. (A) Motif performing an β€œOR” operation over the two input units X2 and X3 has the input unit X2 removed and X1 added by orchestrating feedback (magenta arrows) from unit Z1 which, like Y1, is initiated out-of-phase with the inputs. (B) Input-output table for the network in A. The input units (or cues), X1, X2, and X3, either receive feedforward input (1) or not (0), and the output unit Y1 is either activated (1) or not (0), in the cases where there is feedback or not from Z1. The final row indicates the number of inputs that the output unit's operation depends on (relevant inputs).
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Figure 5: Orchestrated Operations. (A) Motif performing an β€œOR” operation over the two input units X2 and X3 has the input unit X2 removed and X1 added by orchestrating feedback (magenta arrows) from unit Z1 which, like Y1, is initiated out-of-phase with the inputs. (B) Input-output table for the network in A. The input units (or cues), X1, X2, and X3, either receive feedforward input (1) or not (0), and the output unit Y1 is either activated (1) or not (0), in the cases where there is feedback or not from Z1. The final row indicates the number of inputs that the output unit's operation depends on (relevant inputs).

Mentions: Figure 5 shows the mechanisms by which external feedback adds or removes units from an operation. Without any external feedback, the operation performed is β€œX2 or X3.” By adding the external feedback, X2 is removed from the operation and X1 is added, making the operation β€œX1 or X3.” This could be orchestrating feedback from outside the network (as we have shown) but it could also be feedback from another output unit that is initiated with Y1.


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)

Orchestrated Operations. (A) Motif performing an β€œOR” operation over the two input units X2 and X3 has the input unit X2 removed and X1 added by orchestrating feedback (magenta arrows) from unit Z1 which, like Y1, is initiated out-of-phase with the inputs. (B) Input-output table for the network in A. The input units (or cues), X1, X2, and X3, either receive feedforward input (1) or not (0), and the output unit Y1 is either activated (1) or not (0), in the cases where there is feedback or not from Z1. The final row indicates the number of inputs that the output unit's operation depends on (relevant inputs).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 5: Orchestrated Operations. (A) Motif performing an β€œOR” operation over the two input units X2 and X3 has the input unit X2 removed and X1 added by orchestrating feedback (magenta arrows) from unit Z1 which, like Y1, is initiated out-of-phase with the inputs. (B) Input-output table for the network in A. The input units (or cues), X1, X2, and X3, either receive feedforward input (1) or not (0), and the output unit Y1 is either activated (1) or not (0), in the cases where there is feedback or not from Z1. The final row indicates the number of inputs that the output unit's operation depends on (relevant inputs).
Mentions: Figure 5 shows the mechanisms by which external feedback adds or removes units from an operation. Without any external feedback, the operation performed is β€œX2 or X3.” By adding the external feedback, X2 is removed from the operation and X1 is added, making the operation β€œX1 or X3.” This could be orchestrating feedback from outside the network (as we have shown) but it could also be feedback from another output unit that is initiated with Y1.

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