Multiscale mapping of frequency sweep rate in mouse auditory cortex

Abstract

Functional organization is a key feature of the neocortex that often guides studies of sensory processing, development, and plasticity. Tonotopy, which arises from the transduction properties of the cochlea, is the most widely studied organizational feature in auditory cortex; however, in order to process complex sounds, cortical regions are likely specialized for higher order features. Here, motivated by the prevalence of frequency modulations in mouse ultrasonic vocalizations and aided by the use of a multiscale imaging approach, we uncover a functional organization across the extent of auditory cortex for the rate of frequency modulated (FM) sweeps. In particular, using two-photon Ca2+ imaging of layer 2/3 neurons, we identify a tone-insensitive region at the border of AI and AAF. This central sweep region behaves fundamentally differently from nearby neurons in AI and AII, responding preferentially to fast FM sweeps but not to tones or bandlimited noise. Together these findings define a second dimension of organization in the mouse auditory cortex for sweep rate complementary to that of tone frequency.

Reciprocal connectivity between secondary auditory cortical field and amygdala in mice

“…Moreover, previous studies have reported that A2 neurons have long latencies (Kubota et al, 2008;Guo et al, 2012;Tsukano et al, 2015), wide bandwidth (Issa et al, 2014;Ohga et al, 2018), and a less-ordered tonotopic arrangement (Issa et al, 2014;Ohga et al, 2018). These data confirm that mouse A2 has properties of a higher-order region, and also support the idea that auditory cortical subregions are functionally specialized in mice (Honma et al, 2013;Baba et al, 2016;Issa et al, 2017). Given that primary-like regions have few feedforward or feedback connections with the amygdala, they may work to analyze auditory information, as previously proposed.…”

Functional imaging of neuronal activity of auditory cortex by using Cal-520 in anesthetized and awake mice

“…Among these reasons, the use of different indicators might be animportant possibility, although this aspect seems to be often ignored in the community. The use of indicators with a low SNR and detection sensitivity, e.g., OGB-1 and GCaMP3 [14,19,20], may result in a low detection rate of responding neurons in the sensory cortex, thereby yielding an incomplete activity map. In addition, the use of fluo-4, a commonly used indicator for astrocytes [34], may cause a significant contamination of neuronal signals by astrocytes.…”

“…So far, various Ca 2+ indicators including rhod-2 [6], fura-2 [7,8], OGB-1 [9][10][11][12][13], fluo-2 [14], fluo-4 [9,15,16], Alexa Fluor 594 together with fluo-5F [17,18], and genetically encoded Ca 2+ indicators (GCaMP3 [1] and GCaMP6s [3]) [14,19,20] have been widely used in studies of the Au1 with two-photon Ca 2+ imaging in both in vitro and in vivo conditions. The in vivo experiments, particularly the functional mapping experiments, have provided important insights into the topographic organization of the Au1, but the degree of precision in tonotopic mapping has been controversial.…”

Spatial organization of the mouse auditory cortex to sound dynamics revealed using automated image segmentation

“…ACX neurons can be sensitive to amplitude modulation, frequency modulation or sound duration (He et al, 1997;Heil et al, 1992;Schreiner and Urbas, 1986). A systematic organization with regard to frequency sweep rate has been identified in mouse ACX (Issa et al, 2017) while a map of periodicity has been proposed in cat ACX (Langner et al, 2009). At other levels of the auditory pathway such as the inferior colliculus, topographic organizations of amplitude modulation (Heil et al, 1995;Langner et al, 2002;Schreiner and Langner, 1988) and frequency modulation (Hage and Ehret, 2003) exist.…”

“…Recent optical studies provided detailed descriptions of the organization of ACX and primarily A1 on the macro-and meso-scale level in mice (Bandyopadhyay et al, 2010;Issa et al, 2014;Issa et al, 2017;Rothschild et al, 2010;Tsukano et al, 2015;Winkowski and Kanold, 2013). Conventionally the segmentation of ACX into regions of interest (ROIs) is based on snapshots of activity following stimulus presentations, thus capturing only the on-responses.…”