Balanced tone-evoked synaptic excitation and inhibition in mouse auditory cortex

Inferring the role of inhibition in auditory processing of complex natural stimuli

“…Although the GNM uses extracellular data to infer indirectly the excitatory and inhibitory tuning properties, our results are consistent with previous characterizations of the spectral and temporal tuning of inhibition observed in intracellular studies (Sun et al 2010;Sutter et al 1999;Tan and Wehr 2009;Wehr and Zador 2003;Wu et al 2006). In particular, putative excitation and inhibition are usually cotuned, with inhibition and excitation peaking at the same frequency for 44% of the neurons in this study (41/94) and within ½ octave for an additional 35% (33/94).…”

“…The GNM characterization of the putative excitatory and inhibitory tuning is consistent with past observations, including comparisons of their spectral tuning (Wu et al 2008) and their relative timing (Oswald et al 2006;Tan and Wehr 2009;Wehr and Zador 2003;Zhang et al 2003) and mechanisms of intensity tuning (Tan et al 2007;Wu et al 2006). Importantly, the fact that these functional properties occur in the context of naturalistic stimuli demonstrates the relevance of intracellular dynamics to behaviorally relevant conditions.…”

“…1B), as expected from intracellular studies (Tan and Wehr 2009;Wehr and Zador 2003;Wu et al 2006). Furthermore, it captures exactly how each term is nonlinear, finding that the "internal nonlinearities" for both excitation and inhibition are typically rectifying and saturating (Fig.…”

“…3B), as also has been previously observed intracellularly (Oswald et al 2006;Tan and Wehr 2009;Wehr and Zador 2003). However, as described in more detail below, the difference in latency of the STRF itself is just part of the picture, and the overall delay of output of excitation and inhibition in complex stimulus contexts can also be influenced by other factors than the difference in their temporal peaks, including their shape and rising phase, as well as the dynamics of the stimulus and details of the nonlinear processing itself.…”

“…Here, we present a phenomenological model of A1 responses to naturalistic stimuli that characterizes the interplay of putative excitatory and inhibitory inputs, motivated by numerous intracellular studies demonstrating their importance in shaping neuronal tuning (Sun et al 2010;Tan et al 2007;Tan and Wehr 2009;Wehr and Zador 2003;Wu et al 2006). By incorporating these basic, physiologically motivated mechanisms, the model is able to explain several nonlinear response properties of A1 neurons, including intensity tuning and selectivity to stimulus dynamics.…”