Adaptive resonance theory: How a brain learns to consciously attend, learn, and recognize a changing world III

Grossberg, S. (2012) Adaptive resonance theory: How a brain learns to consciously attend, learn, and recognize a changing world. Neural Networks.

Section 18.

Now we are getting into how ART is embedded in the microcircuitry of cortex and thalamus. This also begins to combine ART with FACADE (Form-And-Color-And-DEpth), which introduces horizontal interactions.

Boundaries are completed inwardly between oriented and collinear cell populations. Surfaces are completed outwardly in uncorrelated manner until reaching boundaries. Boundaries form through interblobs in V1 to pale stripes in V2 and beyond to V4. Surfaces go through blobs in V1 to thin stripes in V2 and beyond to V4.

All boundaries are invisible (In a consciousness sense). Surfaces are visible. This is because surfaces are part of surface-shroud resonances, where consciousness needs a resonant state. (I guess boundaries aren't resonances? Or they are resonances, but not all resonances are consciousness).

Cortico-cortical feedback tend to preferentially originate in layer 6 of a higher area and terminate in layer 1 of a lower area. This top-down feedback is "modulatory". Goes through apical dendrites of layer 5, to layer 6 then is "folded" back up into layer 4.

5a: LGN has two excitatory pathways to L4. L6 activates L4 though modulatory on-center, off-surround network. L4 is driven by direct LGN inputs. This circuit "contrast-normalizes" the inputs that layer 4 receives from LGN.

5b/d: cortical feedback signals are carried through L6 back to L4. A similar attentional feedack occurs between L6 of V1 and LGN.

5c: Layer 2/3 possess long-range horizontal connections that are used for perceptual grouping of contours, textures, and shading. (Pattern completion). They ensure "boundaries are invisible" (not sure what this means). 2/3 also sends back to "folded-feedback path", with direct routes to L6 and indirect routes to L5.

5e: hierarchical propagation of priming: V2 repeats laminar pattern of V1, but at larger spatial scale. Since top-down signals are modulatory then the top of the hierarchy (e.g. prefrontal cortex) can potentially modulate all the way down.

Pre-attentive grouping. Both intercortical attentional feedback and intracortical grouping feedback share the same competitive selection circuit from L6-to-L4. L2/3 acts as the attentional prime needed for learning, without feedback from higher cortical areas. Both L2/3 and higher areas act on the same L4-to-L6 selection circuit. "The pre-attentive grouping is its own attentional prime".

Balance of excitation and inhibition. L23 cells fire only if they get direct bottom-up input, or if co-linear inputs from pairs or more are of bipole populations. (You only see the edge if you have pac-men at both ends).

Cortex exists at a "cusp of excitability" in the resting state.

Unambiguous scene is processed - fast sweep up cortical hierarchy directly through L4 to L2/3 and then to L4 to L2/3 in higher areas. Multiple possible groupings the feedback competition arises due to inhibitory interactions in L4 and L2/3. Competitive circuits are self-normalizing. "they tend to conserve the total activity in hte circuit".

self-normalizing circuits carry out a type of "real-time probability theory". Amplitude of cell activity covaries with the certainty of the network's selection/decision about a grouping. Amplitude, in turn, is translated into processing speed and coherence of cell activations.

next is section 31.