In this context it is of interest that previous studies demonstrated that feedforward propagation of activity to higher cortical areas mainly utilizes the AMPA receptor, whereas feedback effects rely more on the NMDA receptor [85], which plays an important role in synaptic plasticity.

Specifically, the learning scheme predicts that feedback connections are important for the induction of tags on feedforward connections from sensory cortices to the association cortex (Fig.

At the start of every time step, feedforward connections propagate information from the sensory layer to the association layer through modifiable connections vij.

follows the same rule so that the strength of feedforward and feedback connections becomes similar during learning, in accordance With neurophysiological findings [33].

1B) enables the formation of tags on the feedforward connections onto the regular unit.

In the model, the new stimulus causes feedforward processing on the next time step t, which results in another set of Q-values.

The plasticity of the feedback connections 14/; and 14/2; from the Q-Value layer to the association layer follows the same rule as the updates of connections and wfifk and the feedforward and feedback connections between two units therefore become proportional during learning [14] .

As indicated above, learning makes the strength of feedforward and feedback connections similar so that can be estimated as the amount of feedback w’fj that unit j receives from the seA comparison to Eq.

In spite of their simple feedforward structure with only seven units in the association layer, AuGMEnT trained the networks to criterion in all simulations within a median of 11,550 trials.