Journal: bioRxiv

Article Title: Role of Posterior Medial Thalamus in the Modulation of Striatal Circuitry and Choice Behavior

doi: 10.1101/2024.03.21.586152

Figure Lengend Snippet: (A) Schematic detailing pAAV-ChR2-EYFP injection unilaterally into POm ( Right ), and optogenetic stimulation of POm-striatal afferents whilst recording from identified and unidentified neurons via ex vivo slice of posterior DLS (AP range: −0.34 to −1.22 relative to Bregma; Left ). See . Illumination (2.5ms pulses of 470nm light, ~0.6mW intensity) was delivered through the 40x objective. (B) Representative injection site (orange) in POm ( Left ), and viral spread of all electrophysiology injections within highlighted POm (purple; Right ). S1BF = S1 Barrel Field. Scale = 1mm. (C) Red box inset from panel (B) highlighting stereotypical POm-cortical projection pattern to S1BF L1 and L5a. , , Right : POm-striatal axons within posterior DLS. CC = corpus callosum. Scale = 200µm. (D) Representative cell type-specific PSPs to SP stimulation. Colored lines = average PSP of 20 sweeps. Gray lines = 20 individual traces. Solid vertical and dashed horizontal lines = latency and amplitude, respectively. Red dashed line = 0mV. Blue tick = photostimulation (PS). Time scale = 10ms. Voltage scale = 4mV. (E) Amplitudes evoked by each cell type were similar (D1-SPNs = 20 cells from 6 mice, D2-SPNs = 11 cells from 5 mice, PVs = 17 cells from 7 mice, unidentified SPNs = 7 cells from 4 mice). Inset shows grand average PSPs. Time scale = 10ms. Voltage scale = 2mV. (F) Latency to maximum PSP amplitude is significantly quicker in PVs than all other cell types. (G-H) Representative responses of (G) D1-SPN ( Top ) and D2-SPN ( Bottom ), and (H) PV ( Top ) and putative SPN ( Bottom ) to PPR stimulation. PPR is defined as the ratio of PSP amplitude of pulse 2 over the ratio of PSP amplitude of pulse 1. PPR PS parameters = five 2.5ms pulses with 50ms interpulse intervals (20Hz). Time scale = 100ms. Voltage scale = 2mV. See . (I) Stimulation of POm-striatal afferents evokes similar PPR responses. (J-K) Representative responses of (J) D1-SPN ( Top ) and D2-SPN ( Bottom ), and (K) PV ( Top ) and putative SPN ( Bottom ) to train stimulation. Colored lines = average of 5 individual gray traces. Train PS parameters = thirty 2.5ms pulses with 64.2ms interpulse intervals (15Hz). Time scale = 1000ms. Voltage scale = 2mV. (L) Relative PSP amplitude (average of pulses 5-15 compared to pulse 1) is significantly larger than both SPNs. Data are mean ± SEM. *p < 0.05, ** p < 0.01, *** p < 0.001, **** p < 0.0001.

Article Snippet: ChR2 in the POm axon terminals was stimulated via illumination with a 2.5 ms, 470 nm LED light pulse (~0.6 mW measured after the objective; Thorlabs) delivered through the 40X objective lens.

Techniques: Injection, Ex Vivo

Journal: bioRxiv

Article Title: Role of Posterior Medial Thalamus in the Modulation of Striatal Circuitry and Choice Behavior

doi: 10.1101/2024.03.21.586152

Figure Lengend Snippet: (A) Schematic detailing pAAV-hSyn-JAWS-KGC-GFP-ER2 (JAWS) injection unilaterally into POm ( Right ) and a 200µm cannula implanted in the left posterior DLS ( Left ). For the No Stim cohort, only the cannula was implanted in the left posterior DLS. Activation of the inhibitory JAWS opsin was performed constantly on for 1s before and after texture arrival in the whisker field. JAWS activation probability per trial = 0.50. (B) Representative injection site in POm ( Left ), and the cannula placement in the posterior DLS along with ascending POm axons ( Right ). Scale = 1mm. Red inset shows ascending POm axons underneath the optic cannula. Inset scale = 200µm. (C) Top: Stimulation timing (constant illumination for 2s, centered around texture arriving at its endpoint) and texture movement representation during a trial. Note that no light is presented for the No Stim cohort as no stimulation occurred. Bottom: Outcomes for each stimulus-response pair. (D) Schematic representing texture movement and potential outcomes during a single trial. (E) Changes in Hit Rate, FA Rate, Sensitivity (d’), and Bias of all JAWS cohort mice (n = 4) as they transition from the Learning to the Expert phase in box-and-whisker plots. Note that mice are classified as Expert when they achieve a Hit Rate ≥ 0.80 and a FA Rate ≤ 0.30 for two consecutive sessions. Red line = 0. See . (F) Probability density function for overall licking-related activity at each behavioral time point for the JAWS cohort. Vertical black line = sound cue representing trial start as the texture moves towards the whisker field. Vertical red lines = start (texture arrival at endpoint in whisker field) and end (texture departure towards starting point) of the PT window (time where mice can respond by licking). Colored boxes = 500ms grace period (licking does not trigger any outcomes). (G-H) Same as in E, F for the No Stim cohort. (I) JAWS cohort requires significantly more training sessions for expert discrimination compared to the FP and No Stim cohorts. (J) Longitudinal representation of sessions required for expert discrimination. (K) Comparison of Hit Rate, FA Rate, Sensitivity (d’), and Bias during the Learning and Expert phases. (L) Average RT is slower during photoinactivation than non-photoinactivated trials. Data are mean ± SEM. * p < 0.05.

Article Snippet: ChR2 in the POm axon terminals was stimulated via illumination with a 2.5 ms, 470 nm LED light pulse (~0.6 mW measured after the objective; Thorlabs) delivered through the 40X objective lens.

Techniques: Injection, Activation Assay, Whisker Assay, Activity Assay, Comparison