A Neural Model of how Horizontal and Interlaminar Connections of Visual Cortex Develop into Adult Circuits that Carry Out Perceptual Grouping and Learning

Abstract

A neural model suggests how horizontal and interlaminar connections in visual cortical areas V1 and V2 develop within a laminar cortical architecture and give rise to adult visual percepts. The model suggests how mechanisms that control cortical development in the infant lead to properties of adult cortical anatomy, neurophysiology and visual perception. The model clarifies how excitatory and inhibitory connections can develop stably by maintaining a balance between excitation and inhibition. The growth of long-range excitatory horizontal connections between layer 2/3 pyramidal cells is balanced against that of short-range disynaptic interneuronal connections. The growth of excitatory on-center connections from layer 6-to-4 is balanced against that of inhibitory interneuronal off-surround connections. These balanced connections interact via intracortical and intercortical feedback to realize properties of perceptual grouping, attention and perceptual learning in the adult, and help to explain the observed variability in the number and temporal distribution of spikes emitted by cortical neurons. The model replicates cortical point spread functions and psychophysical data on the strength of real and illusory contours. The on-center, off-surround layer 6-to-4 circuit enables top-down attentional signals from area V2 to modulate, or attentionally prime, layer 4 cells in area V1 without fully activating them. This modulatory circuit also enables adult perceptual learning within cortical area V1 and V2 to proceed in a stable way.

Consciousness CLEARS the mind

“…As noted above, this latter circuit plays an important role in attention ( Figure 2b) and in the pre-attentive selection of a correct perceptual grouping in response to a complicated scene (Figure 2c). Grossberg and Williamson (2001) proposed that such balanced circuits are needed for the cortex to develop and learn in a stable way, and simulated how such balanced connections could grow during cortical development. Indeed, if inhibition if inhibition develops to be too weak, then excitation can propagate uncontrollably, whereas if it is too strong, then cells cannot get sufficiently activated.…”

Linking Attention to Learning, Expectation, Competition, and Consciousness

“…479-482) (Dubin and Cleland, 1977;Weber, Kalil, and Behan, 1989); see Figure 2d. (Grossberg, 1999a;Grossberg and Raizacla, 2000;Grossberg and Seitz, 2003;Grossberg and Williamson, 2001;Raizacla and Grossberg, 2001). Three important implications of this result are as follows: These grouping interactions are often cited as the basis of "non-classical" receptive fields that are sensitive to the context in which individual features are found (Bosking, et al, !997;Grosof, Shapley, and Hawken, 1993;Kapadia, et al, 1995;Knierim and van Essen, !992;Peterhans and von cler Heydt, 1989;Polat, el al., 1998;Sheth, el al., 1996;von cler Heydt, Peterhans, and Baumgartner, 1984;Sillito, et al, 1995).…”

“…It is thus of interest that the intracortical and intercortical feedback circuits that control this property have been shown in modeling studies to help stabilize infant development and adult perceptual learning within multiple cortical areas, including cortical areas VI and V2 (Carpenter and Grossberg, 1991;Grossberg, 1999a;I999b;Grossberg and Williamson, 2001). …”

From working memory to long-term memory and back: Linked but distinct

“…I suggest that these claims are not entirely true, even though they overcome an even greater error. Three decades of neural modeling of behavioral and brain data about STM and LTM (e.g., Bradski et al, 1994;Brown et al, 1999;Carpenter and Grossberg, 1991;Fiala, et al, 1996;Grossberg, 1968Grossberg, , 1980Grossberg, , 1987Grossberg, , 1988Grossberg, , 1999Grossberg and Myers, 2000;Page, 2000;Grossberg and Williamson, 2001) suggest that STM and L TM are intimately linked, but embody different organizational principles, are realized by different mechanisms, and obey different laws. Available models clarifY cellular neural mechanisms of STM/L TM and their integration into brain systems, including how STM per se differs fi:om prefrontal working memory that can temporarily store multiple events and their order in STM.…”