Cortical plasticity: Is it time for a change? Peter C Kind  Current Biology  Volume 9, Issue 17, Pages R640-R643 (September 1999) DOI: 10.1016/S0960-9822(99)80412-6

Figure 1 A simplified illustration of the BCM theory of synaptic plasticity in the visual cortex, in which the modification threshold is depicted as the pivot of a seesaw and postsynaptic activity as the platform. The level of postsynaptic activity increases from left to right across the platform, and the average level of postsynaptic activity is illustrated by the depth of red shading of the platform. When the level of postsynaptic activity is below the modification threshold, LTD is induced; when it is above the modification threshold, LTP is induced. The position of the modification threshold changes depending on the average postsynaptic activity and is shown for: (a) binocular experience; (b) binocular deprivation; and (c) monocular deprivation. In the normal situation of binocular experience (a), both LTD and LTP can be elicited and postsynaptic activity is relatively high. The modification threshold would slowly increase as presynaptic afferents increase their efficacy in driving the postsynaptic cell until some equilibrium is reached. During binocular deprivation (b), postsynaptic activity is low, so the modification threshold moves to the left. Thus, the system becomes biased towards LTP induction and the ability to induce LTD is all but eliminated. In contrast, during monocular deprivation (c), the postsynaptic activity is only slightly reduced, because the open eye continues to stimulate the postsynaptic cell. Current Biology 1999 9, R640-R643DOI: (10.1016/S0960-9822(99)80412-6)