Fig. 4.

Hypothesized difference between tuning functions at different parts of single neuron. The BOLD signal is primarily reflecting glutamate release and is thus sensitive to dendritic input. This input may be much wider tuned than the output (Jia et al. 2010). Moreover, in the cerebral cortex, signal decay along the dendrites render the soma less sensitive to distal than to proximal dendritic inputs (Williams and Stuart 2002). In addition, distal inputs may come from a wider set of cortical sources (Petreanu et al. 2009, 2012; Spruston 2008) and thus be less selective than the proximal inputs. This may result in larger bandwidth, i.e., a wider tuning in the dendrites than in the soma, as depicted in the figure. The tuning function may further narrow, when the membrane depolarization at the axon initial segment is turned into an action potential firing probability with an exponential function (Anderson et al. 2000; Miller and Troyer 2002).