Neuronal correlates of repetitive whisker stimulation in wild type mice and models of schizophrenia C. Schreiner 1,2 , T. Bessaih 3,4 , S. Siegel 5 , D. Feldmeyer 1,2 , D. Contreras 4 , T. Abel 6 1 Dept. of Psychiatry, Psychotherapy and Psychosomatics, RWTH Aachen, Germany; 2 Inst. for Neurosci. and Med., Res. Ctr. Jülich, Germany; 3 CNRS, Univ. Pierre et Marie Curie, France; 4 Dept. of Neurosci., Univ. of Pennsylvania, USA; 5 Dept. of Psychiatry, Univ. of Pennsylvania; 6 Dept. of Biology, Univ. of Pennsylvania 385.20 TT9  The amplitude of the LFP onset response does not differ between NRG1+/- and WT mice Average local field potential (LFP) onset response measured during the first 50 ms across all frequencies. No significant difference is found between WT and NRG1+/- mice. 50 Hz 60 Hz 70 Hz 0.5 s 0.4 mV 0.4 mV 0.5 mV 0.5 mV NRG1 raw trace NRG1 average WT raw trace WT average NRG1 WT -0.0006 -0.0005 -0.0004 -0.0003 -0.0002 -0.0001 0 LFP onset amplitude (V)  Conclusions  Introduction Sensory encoding is altered in schizophrenia, leading to cognitive and behavioral disturbances (Javitt, 2009, AnnuRevClinPsychol 5:249-75). Mice heterozygous for the schizophrenia-risk gene Neuregulin 1 (NRG1+/-) display endophenotypes of schizophrenia, including auditory, mnemonic and social deficits (Ehrlichman et al., 2009, BrainRes 1294:116- 27). This study establishes a baseline for repetitive whisker-evoked responses in mice, which were previously studied only in rats, in order to compare NRG1+/- and wildtype mice (WT). In vivo tetrode recordings of layer 4 single- and multi-unit activity (SUA, MUA) in response to air puffs (1 s trains, 10-70 Hz) were acquired under isoflurane/fentanyl anesthesia. The results in WT mice indicate that stimulation frequency is encoded by the firing rate and by the temporal structure of the spike train. In NRG1+/- mice, neural responses are characterized by a smaller stimulus response compared to baseline firing, alterations in response adaptation and dynamics, and reduced phase locking. 70 Hz  Single and multi-unit responses are modulated by stimulation frequency in WT and NRG1+/- mice Mean SUA response Mean MUA response 0 10 20 30 40 50 60 70 80 90 10 Hz 20 Hz 30 Hz 40 Hz 50 Hz 60 Hz 70 Hz stimulation frequency NRG1 WT 0 5 10 15 20 25 30 35 10 Hz 20 Hz 30 Hz 40 Hz 50 Hz 60 Hz 70 Hz stimulation frequency * * * * * * * Mean number of spikes/trial counted over 0-50 ms for onset responses (left panel) and 50-1000 ms for sustained responses (right panel) over all MUAs (one MUA per tetrode) and normal- ized to baseline firing in two NRG1+/- mice (n=12 MUAs) and three WT mice (n=10 MUAs). High-freq. sus- tained responses are sig. different from 10 Hz (t-Test, p < 0.05). Mean MUA onset response Mean MUA sustained response mean MUA (spikes/trial) / baseline mean MUA (spikes/trial) / baseline 0 10 20 30 0 10 20 30 0 20 40 60 0 20 40 60 10 Hz WT (n=10) WT (n=10) NRG1 +/- (n=12) NRG1 +/- (n=12) 0 0.2 0.4 0.6 0 0.2 0.4 0.6 0 0.2 0.4 0.6 1 s 10 Hz train 70 Hz mean unit activity (spikes/trial) WT (n=38) WT (n=38) NRG1+/- (n=75) NRG1+/- (n=75) 0.0 0.2 0.4 0.6  NRG1+/- mice display smaller onset responses and smaller sustained responses 0 10 20 30 40 50 60 70 80 90 10 Hz 20 Hz 30 Hz 40 Hz 50 Hz 60 Hz 70 Hz stimulation frequency NRG1 WT * * * * * * * 0 5 10 15 20 25 30 35 10 Hz 20 Hz 30 Hz 40 Hz 50 Hz 60 Hz 70 Hz stimulation frequency * * * * * * * Mean MUA onset response Mean MUA sustained response mean MUA (spikes/trial) / baseline mean MUA (spikes/trial) / baseline Mean number of spikes/trial for MUA onset responses (left panel) and sustained responses (right panel) as described in box 3. WT onset and sustained responses are significantly larger than NRG1+/- re- sponses (t-Test, p < 0.05; p < 0.07).  Adaptive gating is reduced in NRG1+/- mice 0 0.5 1 1.5 2 2.5 3 3.5 4 MUA SUA 0 0.5 1 1.5 2 2.5 3 * adaptation ratio Adaptation of single and multi-unit activity was measured as a ratio of spikes fired in responses to first and second stimulus in a 10 Hz train. At the multi-unit level, NRG1+/- mice display a smaller reduction of the second, “gated” stimulus than WT mice (t-Test, p=0.06 NRG1 n=11 NRG1 n=15 WT n=10 WT n=44 1. 2. p = 0.06). The same trend can be observed at the single-unit level, where it does not reach significance, however.  NRG1+/- single and multi-unit responses appear less phase- locked to the stimulus, indicating lower firing precision  WT single- and multi-unit responses are phase-locked to the stimulus, indicating high firing precision 10 Hz 30 Hz 50 Hz 70 Hz MUA1 MUA2 SUA1 SUA2 SUA3 0 40 0 46.8 93.6 140.4 187.2 234 280.8 327.6 0 40 0 46.8 93.6 140.4 187.2 234 280.8 327.6 0 40 3.6 50.4 97.2 144 190.8 237.6 284.4 331.2 0 40 3.6 50.4 97.2 144 190.8 237.6 284.4 331.2 0 35 0 46.8 93.6 140.4 187.2 234 280.8 327.6 0 35 0 46.8 93.6 140.4 187.2 234 280.8 327.6 0 35 3.6 50.4 97.2 144 190.8 237.6 284.4 331.2 0 35 3.6 50.4 97.2 144 190.8 237.6 284.4 331.2 0 6 0 46.8 93.6 140.4 187.2 234 280.8 327.6 0 6 0 46.8 93.6 140.4 187.2 234 280.8 327.6 0 6 0 46.8 93.6 140.4 187.2 234 280.8 327.6 0 6 7.2 54 100.8 147.6 194.4 241.2 288 334.8 0 12 3.6 50.4 97.2 144 190.8 237.6 284.4 331.2 0 12 3.6 50.4 97.2 144 190.8 237.6 284.4 331.2 0 12 0 46.8 93.6 140.4 187.2 234 280.8 327.6 0 12 7.2 54 100.8 147.6 194.4 241.2 288 334.8 0 8 3.6 50.4 97.2 144 190.8 237.6 284.4 331.2 0 8 7.2 54 100.8 147.6 194.4 241.2 288 334.8 0 8 7.2 54 100.8 147.6 194.4 241.2 288 334.8 0 8 7.2 54 100.8 147.6 194.4 241.2 288 334.8 spikes phase 360 o 360 o 360 o 360 o 360 o WT phase histograms for 2 MUAs and 3 SUAs indicate that stimulation frequency is encoded by the temporal structure of the spike train. Phase-locking is calculated for sustained responses (0.95 s window, 0.05 s post- stimulus onset) to 10, 30 , 50 and 70 Hz stimulation. 360 o correspond to the time between two successive stimuli in a stimulus train. 0 200 0 54 108 162 216 270 324 0 200 0 54 108 162 216 270 324 0 200 3.6 57.6 111.6 165.6 219.6 273.6 327.6 0 200 7.2 57.6 108 158.4 208.8 259.2 309.6 0 350 0 54 108 162 216 270 324 0 350 3.6 57.6 111.6 165.6 219.6 273.6 327.6 0 350 7.2 57.6 108 158.4 208.8 259.2 309.6 0 350 10.8 61.2 111.6 162 212.4 262.8 313.2 0 5 14.4 57.6 100.8 144 187.2 230.4 273.6 316.8 0 5 7.2 54 100.8 147.6 194.4 241.2 288 334.8 0 5 7.2 54 100.8 147.6 194.4 241.2 288 334.8 0 5 7.2 54 100.8 147.6 194.4 241.2 288 334.8 0 3 7.2 54 100.8 147.6 194.4 241.2 288 334.8 0 3 7.2 54 100.8 147.6 194.4 241.2 288 334.8 0 3 10.8 57.6 104.4 151.2 198 244.8 291.6 338.4 0 3 7.2 54 100.8 147.6 194.4 241.2 288 334.8 0 3 7.2 54 100.8 147.6 194.4 241.2 288 334.8 0 3 10.8 57.6 104.4 151.2 198 244.8 291.6 338.4 0 3 7.2 54 100.8 147.6 194.4 241.2 288 334.8 0 3 7.2 54 100.8 147.6 194.4 241.2 288 334.8 MUA 1 MUA2 SUA1 SUA2 SUA3 10 Hz 30 Hz 50 Hz 70 Hz spikes phase 360 o 360 o 360 o 360 o 360 o NRG1+/- phase histograms for 2 MUAs and 3 SUAs. Phase-locking is calculated as described in box 8. NRG1+/- responses appear less strongly phase-locked to the stimulus than WT responses, suggesting a deficit in the temporal encoding of stimulation frequency.  NRG1+/- mice show a significantly smaller ratio of onset / sustained responses and altered stimulus response dynamics in the lower frequency ranges 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10 Hz 20 Hz 30 Hz 40 Hz 50 Hz 60 Hz 70 Hz onset / sustained response stimulation frequency Onset / sustained MUA response * * * * * * 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 10 Hz 20 Hz 30 Hz 40 Hz 50 Hz 60 Hz 70 Hz 50-500 ms / 500-1000 ms stimulation frequency NRG1 WT * * 1 st / 2 nd half of sustained MUA response 1. 2. 1. 2. Adaptation patterns of MUA. Left panel: Ratio of spikes fired to stimulus onset divided by sustained response. NRG1+/- mice show less adaptation (t-Test, p < 0.05). Right panel: Ratio of spikes fired during the first half of the sustained response (50-500 ms) divided by the second half (500- 1000 ms). NRG1+/- mice display altered adaptation dynamics at 10 and 20 Hz (p < 0.05).  NRG1+/- mice have a smaller ratio between spikes fired in response to stimulus onset and spontaneous activity Mean MUA (spikes/trial) during onset (0-50 ms) normalized to baseline firing across all frequencies is smaller in NRG1+/- than in WT mice (t-Test, p < 0.05). Mean MUA (spikes/trial) during baseline (spontaneous activity during 50 ms time window without stimulation) is larger in NRG1+/- than in WT mice (t-Test, p < 0.05). Mean MUA (spikes/trial) during onset (0-50 ms) measured across all frequencies is larger in NRG1+/- mice compared to WT mice (t-Test, p < 0.05). 0 1 2 3 4 5 6 7 8 9 10 NRG1 WT mean MUA (spikes/trial) onset NRG1 WT 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 NRG1 WT MFR baseline * NRG1 WT 0 10 20 30 40 50 60 70 NRG1 WT MFR onset/ baseline ratio * NRG1 WT * Mean firing rate (MFR) of average multi-unit activity (MUA) measured in NRG1 (n=12 MU) and WT (n=10) mice mean MUA (spikes/trial) during onset mean MUA (spikes/trial) during baseline mean MUA (spikes/trial) onset / baseline View publication stats View publication stats