The GAL4(DBD)::CaMTP hemidriver contains the DNA-binding domain from the Saccharomyces cerevisiae GAL4 gene ( SGDID:S000006169 ) fused to a calmodulin target peptide (CaMTP). It forms one half of a 'split driver' system that is designed to act as a transcriptional reporter of intracellular Ca[2+] (TRIC). The other half of the split system is a hemidriver containing a transcriptional activation domain fused to calmodulin (CaM). In the presence of Ca[2+], calmodulin binds to the target peptide, reconstituting a transcriptional activator that can drive expression of a downstream reporter or responder transgene. The reconstituted transcriptional activator binds specifically to the UAS regulatory sequence due to the presence of the GAL4 DNA-binding domain. The exact sequence of the GAL4(DBD)::CaMTP hemidriver may differ depending on the particular transgene or modified endogenous locus being used. For example, the particular calmodulin target peptide used may vary, and/or it may contain mutations that affect its binding to calmodulin. Different variants may be optimal for use in different neuronal cell types. The TRIC system may be particularly useful for monitoring and manipulating (via a downstream responder) neuronal responses that occur over long periods of time (FBrf0228535).