An Optimal Preparation for Studying Optimization

release. Second, a predictive and detailed model is reor afterthought of transmission, but a crucial means by quired for understanding the functional circuit level conwhich inhibitory signals are evenly distributed in time. sequences of transmission dynamics. Before such a comprehensive model is possible, some additional details need to be resolved. For example, in the current Sacha Nelson model, synchronized and delayed release are assumed Department of Biology to share the same calcium dependence, but this asBrandeis University sumption appears not to hold at some other synapses Waltham, Massachusetts 02254 (Atluri and Regehr, 1999). Additional factors will also be required to explain differences in the kinetics of facilitation of synchronous and delayed release, and perhaps Selected Reading to explain multiple kinetic components of depression. Lu and Trussell’s results argue compellingly that inhiAtluri, P.P., and Regehr, W.G. (1998). J. Neurosci. 18, 8214–8227. bition is functioning in a sustained and global fashion Cobb, S.R., Buhl, E.H., Halasy, K., Paulsen, O., and Somogyi, P. to modify the bushy cell’s response to its excitatory (1995). Nature 378, 75–78. input. In this system, it may be important for inhibition Del Castillo, J., and Katz, B. (1954). J. Physiol. 124, 574–585. not to be precisely timed, since the firing of the inhibitory Dittman, J.S., Kreitzer, A.C., and Regehr, W.G. (2000). J. Neurosci. neurons are already not tightly phase locked to auditory 20, 1374–1385. input. Instead, inhibition in this circuit may provide gain Galarreta, M., and Hestrin, S. (1999). Nature 402, 72–75. control that is updated on a much slower time scale Gibson, J.R., Beierlein, M., and Connors, B.W. (1999). Nature 402, 75–79. than excitation. Is this more tonic mode of inhibitory transmission unique to brainstem auditory nuclei? ReGoda, Y., and Stevens, C.F. (1994). Proc. Natl. Acad. Sci. USA 91, 12942–12946. cent work on the functional role of inhibition in cortical