Sequential maturation of stimulus-specific adaptation in the mouse lemniscal auditory system

Abstract

Stimulus-specific adaptation (SSA), the reduction of neural activity to a common stimulus that does not generalize to other, rare stimuli, is an essential property of our brain. Although well characterized in adults, it is still unknown how it develops during adolescence and what neuronal circuits are involved. Using in vivo electrophysiology and optogenetics in the lemniscal pathway of the mouse auditory system, we observed SSA to be stable from postnatal day 20 (P20) in the inferior colliculus, to develop until P30 in the auditory thalamus and even later in the primary auditory cortex (A1). We found this maturation process to be experience-dependent in A1 but not in thalamus and to be related to alterations in deep but not input layers of A1. We also identified corticothalamic projections to be implicated in thalamic SSA development. Together, our results reveal different circuits underlying the sequential SSA maturation and provide a unique perspective to understand predictive coding and surprise across sensory systems.

Fig. 1.. SSA matures sequentially along the central auditory system.

(A) Schematic of mouse development with time points of hearing onset and electrophysiological recordings. (B) Schematic of mouse brain with the location of the ICC (green), MGV (blue), and A1 (pink). (C) Schematic of coronal slice location of ICC, MGV, and A1 with recording electrodes. (D) Schematic of oddball sequence paradigm. Representative example of 2 of the 10 sequences and corresponding raster plots of an example P20 MGV unit—1 and 4 standards (gray) preceding a deviant (magenta) tone. (E) Representative peristimulus time histogram of an MGV P20 unit’s response to the standard and deviant tone f₁ or f₂ for trials 1 and 2 (CSI = 0.344). (F to H) Average CSI for ICC, MGV, and A1, respectively. ICC: P20, 5 mice, 71 units; P30, 5 mice, 44 units; P40, 5 mice, 106 units; P50, 6 mice, 82 units; f = 0.51, df = 302. MGV: P20, 5 mice, 140 units; P30, 6 mice, 95 units; P40, 5 mice, 87 units; P50, 5 mice, 43 units; f = 12.58, df = 364. A1: P20, 7 mice, 96 units; P30, 6 mice, 183 units; P40, 5 mice, 154 units; P50, 7 mice, 183 units; f = 28.05, df = 615. One-way analysis of variance (ANOVA) with multiple comparisons. n.s., P ≥ 0.05; ***P < 0.0001. (I) CSI for ICC, MGV, and A1 across P20, P30, P40, and P50 ages. P20: ICC versus MGV/A1, f = 46.83, df = 309. P30: ICC versus MGV, f = 20.97, df = 321. P40: ICC versus MGV/A1, f = 62.75, df = 346. P50: ICC versus MGV, f = 10.39, df = 307. Ordinary one-way ANOVA with multiple comparisons. Numbers as in (F) to (H). ***P < 0.001; **P = 0.007; *P = 0.022. In the boxplots, lines represent median, 25th, and 75th percentiles, + represents mean, whiskers represent 10th and 90th percentiles, and points below or above the whiskers are drawn as individual points.

Fig. 2.. Adaptation of the responses to the standard does not fully explain the developmental changes of SSA.

(A) Average firing rate of the standard responses in the first 100 s of sessions, normalized to the first standard of the session. (B) Representative raster plot of a P20 MGV unit’s response to the 10 oddball sequences with standard f₁ and deviant f₂ (left) and standard f₂ and deviant f₁ (right). (C) Normalized spike rate of response to the deviant tone f₂ for each number of preceding tones (2 to 10) to the single standard sequence (1). (D) Normalized spike rate of response to the standard tone f₂ for each number of preceding standards (1 to 9) to the single standard sequence (0). n as in Fig. 1 (F to H). Data represent means ± SEM.

Fig. 3.. SSA maturation does not correlate with changes in spontaneous activity, response bandwidth, or threshold.

(A) Spontaneous activity across adolescence in ICC, MGV, and A1. n.s., P > 0.05, one-way ANOVA with multiple comparisons. ICC: f = 0.14, df = 302; MGV: f = 0.91, df = 364; A1: f = 2.52, df = 615. (B) Scatter plot of CSI versus spontaneous activity across brain areas. (C) Tuning bandwidth at 60-dB SPL across adolescence in ICC, MGV, and A1. ICC: P20 versus P40, P = 0.0001; P40 versus P50, P = 0.0490. P30 versus P40, P = 0.0063. MGV: n.s., P > 0.05. A1: P20 versus P50, P = 0.0003; P30 versus P50, P < 0.0001; P40 versus P50, P < 0.0001; one-way ANOVA with multiple comparisons. ICC: f = 7.48, df = 302; MGV: f = 1.24, df = 363; A1: f = 14.52, df = 603. (D) Scatter plot of CSI versus bandwidth across brain areas. (E) Response threshold across adolescence in ICC, MGV, and A1. ICC: n.s., P > 0.05. MGV: P20 versus P50, P = 0.0043. A1: P20 versus P50, P = 0.0012; one-way ANOVA with multiple comparisons. ICC: f = 1.18, df = 302; MGV: f = 4.45, df = 364; A1: f = 4.68, df = 615. (F) Scatter plot of CSI versus threshold across brain areas. For all panels, n as in Fig. 1. See table S1 for Pearson correlations of (B), (D), and (F). In the boxplots, lines represent median, 25th, and 75th percentiles, + represents mean, whiskers represent 10th and 90th percentiles, and points below or above the whiskers are drawn as individual points. *P < 0.05; **P < 0.01; ***P < 0.001.

Fig. 4.. Auditory experience affects SSA maturation in A1 but not in MGV.

(A) Schematic of mouse postnatal development continuous WN exposure. P0 to P20, mice reared in normal acoustic environment; P20 to P50, exposure to continuous WN; after P50, MGV and A1 extracellular electrophysiological recordings. (B) Scatter plot of SI f₁ and SI f₂ for MGV P50 control (left; as in fig. S2A) and WN-exposed P50 (right). (C) Average CSI for control MGV P20, P30, P40, and P50 (n as in Fig. 1G) and WN-exposed P50 (5 mice, 132 units). Control P20 versus P30/P40/P50, ***P < 0.0001; control P50 versus WN P50, n.s., P < 0.05. (D) Scatter plot of SI f₁ and SI f₂ for A1 P50 control (left; n as in fig. S2A) and WN-exposed P50 (right). (E) Averaged CSI for control A1 P20, P30, P40, and P50 (n as in Fig. 1H) and WN-exposed P50 (7 mice, 448 units). Control P20/P30/P40 versus P50, ***P < 0.0001; control P50 versus WN P50, ***P < 0.0001. (F) Schematic of mouse postnatal development oddball (Odd) exposure. P0 to P20, mice reared in normal acoustic environment; P20 to P50, exposure to oddball paradigm with fixed f₁ and f₂; after P50, A1 extracellular electrophysiological recordings. (G) Scatter plot of SI f₁ and SI f₂ for A1 P50 control (left; as in fig. S2A) and Odd-exposed P50 (right). (H) Average CSI for control A1 P20, P30, P40, and P50 (n as in Fig. 1H) and Odd-exposed P50 (4 mice, 306 units). Control P20 versus P30/P40/P50, ***P < 0.0001; control P50 versus Odd P50, ***P < 0.0001; one-way ANOVA with multiple comparisons for each area across age and unpaired t test to compare across exposure. In the boxplots, lines represent median, 25th, and 75th percentiles, + represents mean, whiskers represent 10th and 90th percentiles, and points below or above the whiskers are drawn as individual points.

Fig. 5.. A1 SSA maturation is specific to deep layers but not to cell type.

(A) Schematic of mouse brain connectivity. (B) Schematic of A1 layer organization (L1/L2/3, superficial; L4, input; L5/L6, deep) and representative electrode shaft. Simplified A1 intracortical (black), thalamocortical (orange), and corticothalamic (brown) projections. (C) Example of CSD analysis (traced vertical lines, sound duration). (D) CSI for superficial (control: P20, 7 mice, 6 units; P30, 6 mice, 23 units; P40, 5 mice, 12 units; P50, 7 mice, 7 units; WN: P50, 7 mice, 20 units; Odd: P50, 4,11; f = 2.29, df = 78), input (control: P20, 9 units; P30, 12 units; P40, 10 units; P50, 6 units; WN: P50, 20 units; Odd: P50, 13 units; f = 0.68, df = 64), and deep (control: P20, 81 units; P30, 148 units; P40, 132 units; P50, 170 units; WN: P50, 325 units; Odd: P50, 282 units; f = 32.29, df = 1137) layers. n.s., P > 0.05; *P = 0.0120; ***P < 0.0001. (E) Histogram of spike peak-to-trough duration (in milliseconds) for FS and RS units (dashed black line, threshold for classification). Inset: Example waveforms of FS and RS units. (F) CSI of FS and RS units for all layers [control: P20, 8 mice, 12 FS units, 84 RS units; P30, 6 mice, 30 FS units, 153 RS units; P40, 5 mice, 14 FS units, 140 RS units; P50, 7 mice, 27 FS units, 156 RS units; WN: P50, 7 mice, 69 FS units, 379 RS units; Odd: P50, 4 mice, 39 FS units, 267 RS units]. ***P < 0.0001; #P = 0.06. (G) CSI of FS and RS neurons for deep layers [control: P20, 11 FS units, 70 RS units; P30, 27 FS units, 121 RS units; P40, 10 FS units, 122 RS units; P50, 26 FS units, 144 RS units; WN: P50, 50 FS units, 275 RS units; Odd: P50, 35 FS units, 247 RS units; f = 2.21, df = 398]. *P = 0.0023; ***P < 0.0001, one-way ANOVA with multiple comparisons for each area across age and unpaired t test to compare across exposure. In the boxplots, lines represent median, 25th, and 75th percentiles, + represents mean, whiskers represent 10th and 90th percentiles, and points below or above the whiskers are drawn as individual points.

Fig. 6.. Corticothalamic projections are implicated in SSA maturation.

(A) Schematic of coronal slice including MGV (blue) and A1 (pink) location, light activation of PV-expressing ChR2 units, silencing of A1 corticofugal projections (brown), and parallel recordings in MGV. (B) Example schematic of light on condition for 2 of the 10 total oddball sequences. Light (473 nm) constantly on (blue) for the length of each sequence, turned off 50 ms after Deviant tone offset, and turned back on after 250 ms for the onset of standard tone. (C) Average CSI of light off–light on for MGV P20, P30, P40, and P50 (P20: 7 mice, 101 units; P30: 7 mice, 142 units; P40: 6 mice, 80 units; P50: 5 mice, 105 units). P20, P = 0.0001; P30, P < 0.0001; P40, P = 0.0003; P50, P = 0.0004; parametric paired t test light off versus light on per age. ***P < 0.001 (D) Average CSI for light on condition. n.s., P > 0.05, f = 1.60, df = 424; one-way ANOVA with multiple comparisons. (E) Schematic of coronal slice including ICC (green) and A1 (pink) location, light activation of PV-expressing ChR2 cells, silencing of A1 corticofugal projections (brown), and parallel recordings in IC. (F) Average CSI of light off–light on for ICC P40 (6 mice, 163 units). n.s, P > 0.05, parametric paired t test light off versus light on. (G) Schematic of coronal slice including MGV (blue) and A1 (pink) location, light (589 nm; green) inhibition of L6 Ntsr1-expressing cells projecting to MGV (brown), and parallel recordings in this area. (H) Averaged CSI spike rate of light off–light on for MGV P40 (5 mice, 71 units). Parametric paired t test light off versus light on; *P < 0.05. The bar graphs represent means ± SEM.

Fig. 7.. Sequential maturation of SSA in the central auditory areas of adolescent mice.

Schematic of connectivity organization and strength between the central auditory areas—ICC, MGV, and A1—during the adolescent period of mouse development. Color code: ICC, green; MGV, blue; A1, pink. Gradient of MGV and A1 color code: darker to lighter color, higher to lower CSI. Our data suggest that the feedforward connectivity (orange arrows) from ICC to MGV and from MGV to A1 and feedback connectivity (dashed red arrows) from A1 to ICC do not change significantly during adolescence. CSI of A1 deep layers decreases at P50. CSI in MGV decreases at P30. Feedback connectivity (red arrows) increase in strength throughout adolescence development with up-regulated percentage of CSI reduction in MGV with A1 silencing (20 to 34%).