Fig. 5.

A simple model showing how attention-centered coordinates can be useful for object recognition. For all panels, the bottom rectangle represents a one-dimensional visual field where patterns consisting of vertical and horizontal bars may appear. Squares in the above grid represent neurons that respond either to a horizontal or a vertical bar shown in their receptive field; these units are gain-modulated by attention. Blue arrows indicate the location where attention is directed. The circles on the right represent downstream neurons, each driven by three rows of gain-modulated units. Bars and circles to the left of a indicate, respectively, the selectivities and preferred attentional locations of the six rows of neurons. Thus, to obtain the maximal response from a neuron in the top row, a vertical bar must be shown in its receptive field and attention must be directed one receptive field to the right; to obtain the maximal response from a neuron in the second row, a horizontal bar must be shown in its receptive field and attention must be directed directly to it, and so on. Black squares show active neurons. a and b, The three-bar pattern shown activates the bottom downstream neuron (orange). The response is the same wherever the pattern is shown, as long as attention is directed to it. c, The bottom downstream neuron is still activated when a second pattern is presented simultaneously, if attention is focused on the preferred pattern. d, The bottom downstream neuron stops responding because attention is focused on the nonpreferred pattern, but another neuron selective for this pattern is now active. According to a more realistic version of this model (Salinas and Abbott 1997a, 1997b), neurons in V4 that are gain-modulated by attention (Connor and others 1996, 1997) may give rise to responses in the inferotemporal cortex that are highly selective and translation invariant (Desimone and others 1984; Tovee and others 1994).