Firing Rate Homeostasis in Visual Cortex of Freely Behaving Rodents Keith B. Hengen, Mary E. Lambo, Stephen D. Van Hooser, Donald B. Katz, Gina G. Turrigiano  Neuron  Volume 80, Issue 2, Pages 335-342 (October 2013) DOI: 10.1016/j.neuron.2013.08.038 Copyright © 2013 Elsevier Inc. Terms and Conditions

Figure 1 Chronic Multiunit Recording from V1 of Freely Behaving Rats (A) Location of implanted microwires (arrowheads), overlaid with diagram of coronal section of rat V1m (modified from Paxinos and Watson, 1997). (B) Average LFP response from layer 2/3 to 50 × 50 ms light pulses delivered at 1 Hz (gray bar). (C) Raw traces collected on a single wire originating from two units. (D) Example of principal components clustering of units in (C). Individual spikes are represented as points in eigenspace defined by the first four principal components. The clustering algorithm identifies discrete clusters (pink and green). (E) Plot of spike trough-to-peak versus slope between 0.25 and 0.57 ms after the spike trough revealed a bimodal distribution that corresponds to pFS cells (pink) and RSUs (green). Inset: mean and peak firing rates of the RSU and pFS populations. (F) Heat map of 150 min of firing from five neurons recorded simultaneously on a single array. All error bars indicate ±SEM. Neuron 2013 80, 335-342DOI: (10.1016/j.neuron.2013.08.038) Copyright © 2013 Elsevier Inc. Terms and Conditions

Figure 2 Homeostatic Regulation of RSU Firing during MD (A) Experimental design. (B) Example heat maps of all recorded well-isolated RSUs from a single animal on baseline 3 (BL3), MD2, and MD6. (C and D) Average RSU firing rates in the nondeprived (control) hemisphere (C) and in the deprived hemisphere (D); here and below baseline is blue, MD is gray. Number of neurons contributing to each mean is indicated in white. (E) Distribution of mean RSU firing rates on BL3, MD2, and MD6. (F) Cumulative distribution of ISIs for BL3, MD2, and MD6; inset plots CV of ISIs, calculated for each cell and averaged. ∗, significantly different from BL3. All error bars indicate ±SEM. Neuron 2013 80, 335-342DOI: (10.1016/j.neuron.2013.08.038) Copyright © 2013 Elsevier Inc. Terms and Conditions

Figure 3 Layer and Cell-Type Specificity of Firing Rate Homeostasis (A) Top: example mEPSCs recorded ex vivo from L2/3 pyramidal neurons. Bar plot: mEPSC amplitude on MD2, MD4, and MD6 expressed as percentage of nondeprived hemisphere control values. ∗, significantly different from control. (B) Firing rates from RSUs in layers 2–4 for baseline (blue) and MD (gray). ∗, significantly different from BL3. (C) ISI distribution from pFS cells for BL3, MD1, and MD6. Inset shows CV of ISI by day. (D) A comparison of RSUs and pFS-normalized firing rates during baseline (blue bar) and MD (gray bar). ∗, significant difference between RSU and pFS. All error bars indicate ±SEM. Neuron 2013 80, 335-342DOI: (10.1016/j.neuron.2013.08.038) Copyright © 2013 Elsevier Inc. Terms and Conditions

Figure 4 Firing Rate Homeostasis Is Expressed across Sleep-Wake States (A and B) LFP delta (black trace, 1–4 Hz) (A) and gamma (B) “high” band powers during epochs of sleep (light green), quiet waking (yellow), and active wake (light blue). (C) Heat map of firing during the sleep-wake transition illustrated in (A) and (B). (D and E) RSUs (D) and pFS (E) firing rates during epochs of active wake (blue bars) and sleep (green bars) for baseline (dark blue horizontal bar) and 6 days of MD (gray horizontal bar). All error bars indicate ±SEM. Neuron 2013 80, 335-342DOI: (10.1016/j.neuron.2013.08.038) Copyright © 2013 Elsevier Inc. Terms and Conditions