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. 2015 Mar 18;85(6):1332-43.
doi: 10.1016/j.neuron.2015.02.019. Epub 2015 Mar 5.

Gamma rhythms link prefrontal interneuron dysfunction with cognitive inflexibility in Dlx5/6(+/-) mice

Kathleen K A Cho  1 , Renee Hoch  2 , Anthony T Lee  1 , Tosha Patel  1 , John L R Rubenstein  2 , Vikaas S Sohal  3
Affiliations

Gamma rhythms link prefrontal interneuron dysfunction with cognitive inflexibility in Dlx5/6(+/-) mice

Kathleen K A Cho et al. Neuron. .

Abstract

Abnormalities in GABAergic interneurons, particularly fast-spiking interneurons (FSINs) that generate gamma (γ; ∼30-120 Hz) oscillations, are hypothesized to disrupt prefrontal cortex (PFC)-dependent cognition in schizophrenia. Although γ rhythms are abnormal in schizophrenia, it remains unclear whether they directly influence cognition. Mechanisms underlying schizophrenia's typical post-adolescent onset also remain elusive. We addressed these issues using mice heterozygous for Dlx5/6, which regulate GABAergic interneuron development. In Dlx5/6(+/-) mice, FSINs become abnormal following adolescence, coinciding with the onset of cognitive inflexibility and deficient task-evoked γ oscillations. Inhibiting PFC interneurons in control mice reproduced these deficits, whereas stimulating them at γ-frequencies restored cognitive flexibility in adult Dlx5/6(+/-) mice. These pro-cognitive effects were frequency specific and persistent. These findings elucidate a mechanism whereby abnormal FSIN development may contribute to the post-adolescent onset of schizophrenia endophenotypes. Furthermore, they demonstrate a causal, potentially therapeutic, role for PFC interneuron-driven γ oscillations in cognitive domains at the core of schizophrenia.

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Figures

Figure 1
Figure 1. Intrinsic properties of fast-spiking parvalbumin (PV) interneurons become abnormal following adolescence in Dlx5/6+/− mice
(A) A fast-spiking interneuron (FSIN) in layer 5 of adult (P71) mouse prefrontal cortex that was filled with biocytin (blue) and later confirmed to express PV (green); scale bar = 20 μm. Putative interneurons were initially identified by the expression of AAV-DlxI12b-mCherry (red). (B) Example current-clamp responses of adult FSINs to injection of depolarizing current in wild- type (black) and Dlx5/6+/− (blue) mice. (C) The action potential half-width, input resistance, membrane time constant, and action potential threshold, calculated from current clamp responses of P16-P20 (juvenile), P45-49 (adolescent), and P63-82 (adult) FSINs to brief current pulses (−50 pA for input resistance, 100 pA above spiking threshold for other parameters). (D) Whole-cell recordings were made from layer 5 pyramidal neurons (orange) in prefrontal brain slices from P63-88 mice, while stimulating ChR2 (yellow) in DlxI12b-expressing interneurons (red). Pyramidal neurons were voltage clamped at +10 mV. (E) Example inhibitory currents recorded from layer 5 pyramidal neurons in response to 40 Hz interneuron stimulation in WT (black) and Dlx5/6+/− (blue) mice. (F) Population average of the IPSC amplitudes evoked by 40 Hz optogenetic stimulation of interneurons. All data show means ± SEM. *p < 0.05, **p < 0.01, ***p < 0.001. See also Figures S1, S2.
Figure 2
Figure 2. Dlx5/6+/− mice exhibit a post-adolescent onset of increased anxiety and impaired cognitive flexibility
(A) 7 week old Dlx5/6+/− mice and their WT littermates spend similar amounts of time in the center of an open field. In a distinct 10 week old cohort, Dlx5/6+/− mice spend less time in the center than do WT littermates. (B) In the elevated plus maze, 7 week old Dlx5/6+/− mice and their WT littermates spend similar amounts of time in the open arms. In a distinct 10 week old cohort, Dlx5/6+/− mice spend less time in the open arms than do WT littermates. (C) Schematic illustrating the rule-shifting task, in which mice chose one of two bowls, each baited by an odor (O1 or O2) and a textured digging medium (TA or TB), to find a food reward (the stimulus associated with reward is indicated in red). Mice first learn an initial association (IA) between a stimulus (e.g., odor O1) and food reward. Once mice reach the learning criterion (8 correct out of 10 consecutive trials), this association undergoes an extra-dimensional rule shift (RS), e.g., from O1 to a texture (TA). Mice adapt to a reversed light/dark cycle, undergo food restriction, and are habituated to the bowls, textured digging media, and food rewards before beginning testing. (D) Performance in the initial association and rule-shift is similar for 7 week old Dlx5/6+/− and WT mice. (E) There is no significant difference in “perseverative” errors, i.e., errors that are consistent with the initial rule, for 7 week old Dlx5/6+/− and WT mice. (F) Performance of adult Dlx5/6+/− mice and their WT littermates on the initial association and rule shift. (G) During the rule-shift, Dlx5/6+/− mice made a preponderance of perseverative errors compared to “random errors,” i.e., errors that are inconsistent with both the old and new rules. All data show means ± SEM and analyzed using two-tailed Student's unpaired t-tests. *p < 0.05, **p < 0.01, ***p < 0.001. See also Figure S3.
Figure 3
Figure 3. Dlx5/6+/− mice are not impaired in rule reversals
(A) Schematic illustrating how we assayed rule reversals either before or after rule shifts. In all cases, mice first learn an initial association between the food reward and one stimulus, e.g., odor 1 (O1). In some cases (black arrows), the mice then experience a rule shift (RS) in which a previously irrelevant stimulus, e.g., texture A (TA), becomes associated with reward. In the other cases (blue arrows), immediately following the initial association, mice learn a rule reversal (RR), in which the stimulus that was unrewarded during the initial association, e.g., odor 2 (O2), now becomes associated with reward. In both cases, all three portions of the task (IA / RS / RR or IA / RR / RS) were completed consecutively on one day. The rule reversal always tested the ability of mice to learn a reversal of the association that they had successfully acquired during the IA, whereas the rule shift always tested mice on their ability to learn a rule based a stimulus that was previously irrelevant to the outcome of each trial. (B) Performance of adult Dlx5/6+/− mice and their wild-type littermates in the IA, followed by the RS, and RR. (C) Performance of adult Dlx5/6+/− mice in the IA, followed by the RR, and RS. (D) During the rule shift shown in (C), adult Dlx5/6+/− mice made a preponderance of perseverative errors, compared to random errors. All data show means ± SEM and are analyzed using two-tailed Student's t-tests. **p < 0.01, ***p < 0.001.
Figure 4
Figure 4. Adult (but not adolescent) Dlx5/6+/− mice exhibit abnormal baseline γ oscillations and deficient task-evoked prefrontal γ oscillations
(A) Schematic showing the placement of EEG recording electrodes at the dorsolateral border of PFC in adult mice. (B) Sample prefrontal EEG recordings from both adult Dlx5/6+/− and WT mice around the time of digging in the rule-shifting task; scale bars = 100 μV, 100 msec. (C) Log transform of the averaged, normalized power spectrum for prefrontal EEG recordings from Dlx5/6+/− (blue trace) and wild-type (black trace) mice. For this plot, the power spectrum from each mouse was normalized by the sum of all values from 0-120 Hz (excluding 58-62 Hz). (D) Adult Dlx5/6+/− mice exhibit an increase in the power of prefrontal baseline γ (30-120 Hz) oscillations compared to their age-matched WT littermates. (E) Change in unnormalized power (measured in log units) during the first ten trials of the rule- shifting portion of the task, compared to the baseline period, in 7-week old WT and Dlx5/6+/− mice. Task-evoked fast γ oscillations (62-120 Hz) are not significantly different between both genotypes. (F) During periods of social interaction, both 7-week old wild-type and age-matched Dlx5/6+/− mice show a similar increase in prefrontal γ oscillations (compared to baseline). (G) Task-evoked γ oscillations are significantly smaller in adult Dlx5/6+/− mice compared to age- matched WT littermates. (H) During periods of social interaction, adult WT mice show an increase in the power of prefrontal γ oscillations (relative to baseline) compared to no change or a slight decrease in prefrontal γ power in age-matched Dlx5/6+/− mice. To analyze changes in power during the baseline period (which was just before the social interaction task), we first used 2-way ANOVA and found significant effects of genotype (p<0.001), frequency (p<0.001), and genotype × frequency (p<0.05). We then checked for differences between genotypes for each frequency band using two-tailed, unpaired Student's t-tests. For the rule-shifting task, we used repeated measures ANOVA with mouse, condition / time during task (baseline or time relative to digging), and genotype × condition (baseline vs. task) as factors; asterisks indicate significance of the genotype × condition interaction. For social interaction, we used repeated measures ANOVA with mouse, task condition (baseline vs. social interaction), and genotype × condition (baseline vs. social interaction) as factors; asterisks indicate the significance of the genotype × condition interaction. All data show means ± SEM and are analyzed using two-tailed Student's unpaired t-tests or 2- way ANOVA or repeated measures ANOVA. **p < 0.01, ***p < 0.001. See also Figure S4.
Figure 5
Figure 5. Optogenetic inhibition of mPFC interneurons specifically disrupts rule shifts but not rule reversals
(A) Optogenetic inhibition alters the power spectrum of prefrontal EEG activity recorded from the PFC of an adult I12b-Cre mouse while in its home cage, not performing any task. Note that for this plot, each power spectrum was normalized by the sum of all values from 0-120 Hz (excluding 58-62 Hz). (B) Experimental design: we optogenetically inhibited interneurons by injecting Arch bilaterally into the PFC of I12b-Cre animals performing the IA and RS. (C) During constant illumination, Arch-expressing I12b-Cre mice are impaired on the rule shift portion of the task compared with controls. (D) While receiving optogenetic inhibition during the rule shift, Arch-expressing I12b-Cre mice make a preponderance of perseverative errors. (E) Optogenetic inhibition of mPFC interneurons has no effect on rule reversal in Arch-expressing I12b-Cre mice compared to controls. All data show means ± SEM and are analyzed using two-tailed Student's t-tests or repeated measures ANOVA. *p < 0.05, **p < 0.01, ***p < 0.001.
Figure 6
Figure 6. Pharmacologic augmentation of interneuron function rescues cognitive inflexibility in adult Dlx5/6+/− mice
(A) A single, I.P. injection of CLZ (0.0625 mg kg−1) did not significantly alter the time spent in the center of the open field by either adult Dlx5/6+/− mice or age-matched WT littermates. (B) CLZ did not alter the number of trials needed to learn the initial association in either adult Dlx5/6+/− mice or age-matched WT littermates. However, CLZ completely normalized the number of trials required for adult Dlx5/6+/− mice to learn the rule-shifting task. The number of trials to learn the rule reversal was not affected. (C) CLZ completely normalizes the number of errors made by adult Dlx5/6+/− mice during rule shifting. (D) Task-evoked fast γ oscillations (62-120 Hz) in adult Dlx5/6+/− mice were significantly larger in CLZ than in vehicle. (E) After CLZ treatment, task-evoked power in the 62-90 and 90-120 Hz bands was similar for adult Dlx5/6+/− and WT mice. All data show means ± SEM and are analyzed using two-tailed Student's t-tests or repeated measures ANOVA. *p < 0.05, **p < 0.01, ***p < 0.001. See also Figure S5.
Figure 7
Figure 7. Optogenetic augmentation of interneuron function rescues cognitive flexibility in adult Dlx5/6+/− mice
(A) Log transform of the normalized power spectrum for prefrontal EEG recordings from an adult Dlx5/6+/− mouse injected with AAV-I12b-mCherry in the mPFC during the first ten trials of the rule shift portion of the task in the absence of light stimulation on Day 1, in the presence of optogenetic stimulation (40 Hz, 5 msec) on Day 2, and in the absence of light stimulation on Day 3. For this plot, the power spectrum from each mouse was normalized by the sum of all values from 0-200 Hz (excluding 58-62 Hz). (B) Similar to (A) but shows power spectrum of prefrontal EEG recordings from an adult Dlx5/6+/− mouse injected with AAV-I12b-ChR2 in the mPFC. (C) Schematic illustrating the design of experiments using 40 Hz optogenetic stimulation of mPFC interneurons during rule shifting. Dual fiber-optic cannulae were implanted bilaterally in the mPFC of Dlx5/6+/− mice. AAV (yellow) was also injected into the PFC bilaterally to drive expression of either ChR2-eYFP or mCherry in interneurons using the I12b enhancer. On Day 1, animals performed the initial association (IA) and rule shift (RS) in the absence of optogenetic stimulation. On Day 2, after the 80% correct criterion was reached in the IA, optogenetic stimulation was switched on, and continued during three additional IA trials and the subsequent RS. On Day 3, animals again performed the IA and RS in the absence of optogenetic stimulation. Optogenetic stimulation = blue light flashes at 40 Hz. (D) Rule shift performance does not differ between Dlx5/6+/− mice that express ChR2 or mCherry in interneurons on Day 1, prior to optogenetic stimulation. However, 40 Hz stimulation on Day 2 selectively normalizes rule shifting in ChR2-expressing Dlx5/6+/− mice. Dlx5/6+/− mice that express ChR2 maintain improved cognitive flexibility on Day 3, even without additional light stimulation. (E) The improved rule-shifting performance in (D) is accompanied by a decrease in perseverative errors (P). (F) Similar to (C), the experimental design for experiments in which animals perform the IA and RS in the absence of optogenetic stimulation on Day 1, then receive 12.5 Hz optogenetic stimulation of PFC interneurons on Day 2, and 40 Hz optogenetic stimulation on Day 3. (G and H) Unlike 40 Hz stimulation, the 12.5 Hz pattern of stimulation depicted in (F) fails to improve either the number of trials required to learn the rule shift (G). Dlx5/6+/− mice that express ChR2 maintain improved cognitive flexibility on Day 10 (i.e., 7 days after 40 Hz stimulation), even in the absence of additional light stimulation (G). (I-K) 60 Hz optogenetic stimulation also improves learning of a rule shift and reduces preservative errors in ChR2-expressing Dlx5/6+/− mice. All data show means ± SEM and are analyzed using two-tailed Student's t-tests or repeated measures ANOVA. *p < 0.05, **p < 0.01, ***p < 0.001. See also Figures S6 and S7.
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References

    1. Assaf M, Jagannathan K, Calhoun VD, Miller L, Stevens MC, Sahl R, O'Boyle JG, Schultz RT, Pearlson GD. Abnormal functional connectivity of default mode sub-networks in autism spectrum disorder patients. Neuroimage. 2010;53:247–256. - PMC - PubMed
    1. Belforte JE, Zsiros V, Sklar ER, Jiang Z, Yu G, Li Y, Quinlan EM, Nakazawa K. Postnatal NMDA receptor ablation in corticolimbic interneurons confers schizophrenia-like phenotypes. Nature neuroscience. 2010;13:76–83. - PMC - PubMed
    1. Bissonette GB, Martins GJ, Franz TM, Harper ES, Schoenbaum G, Powell EM. Double dissociation of the effects of medial and orbital prefrontal cortical lesions on attentional and affective shifts in mice. J Neurosci. 2008;28:11124–11130. - PMC - PubMed
    1. Bissonette GB, Schoenbaum G, Roesch MR, Powell EM. Interneurons Are Necessary for Coordinated Activity During Reversal Learning in Orbitofrontal Cortex. Biological psychiatry. 2014 - PMC - PubMed
    1. Cardin JA, Carlen M, Meletis K, Knoblich U, Zhang F, Deisseroth K, Tsai LH, Moore CI. Driving fast-spiking cells induces gamma rhythm and controls sensory responses. Nature. 2009;459:663–667. - PMC - PubMed

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