**3. Use of golgi impregnation techniques to study spines**

There is increasing evidence that the processes underlying learning and memory involve neural plasticity, which includes neurogenesis and dendritic remodeling. Ultimately memory seems to require dendritic remodeling which leads to an increase in LTP and synaptic strength (See Figure 3, schematic of a spine). This idea that memory requires alterations in dendritic spines is supported by the demonstration that the acquisition of new memories is associated with changes in dendritic spine density in the CA1 hippocampal region in adult male rats (Leuner et al, 2003; Jedlicka et al, 2008; Beltran-Campos, 2011). In addition, there is increasing evidence that existing spines undergo structural alterations that result in LTP (Jedlicka et al, 2008; Morgado-Bernal, 2011). Spine assembly involves a complex sequence of events and many proteins which have been demonstrated to be altered following memory tasks (Hotulainen and Hoogenraad, 2010; Morgado-Bernal, 2011). For example the polymerization of actin, which is highly concentrated in dendritic spines, appears to be required for the induction of LTP (reviewed by Fortin et. al, 2011).
