Target-specific membrane potential dynamics of neocortical projection neurons during goal-directed behavior

Abstract

Goal-directed behavior involves distributed neuronal circuits in the mammalian brain, including diverse regions of neocortex. However, the cellular basis of long-range cortico-cortical signaling during goal-directed behavior is poorly understood. Here, we recorded membrane potential of excitatory layer 2/3 pyramidal neurons in primary somatosensory barrel cortex (S1) projecting to either primary motor cortex (M1) or secondary somatosensory cortex (S2) during a whisker detection task, in which thirsty mice learn to lick for water reward in response to a whisker deflection. Whisker stimulation in 'Good performer' mice, but not 'Naive' mice, evoked long-lasting biphasic depolarization correlated with task performance in S2-projecting (S2-p) neurons, but not M1-projecting (M1-p) neurons. Furthermore, S2-p neurons, but not M1-p neurons, became excited during spontaneous unrewarded licking in 'Good performer' mice, but not in 'Naive' mice. Thus, a learning-induced, projection-specific signal from S1 to S2 may contribute to goal-directed sensorimotor transformation of whisker sensation into licking motor output.

Keywords: goal-directed sensorimotor learning; mouse; neocortical projection neurons; neuroscience; primary somatosensory barrel cortex; secondary somatosensory cortex; whisker motor cortex; whole-cell membrane potential recordings.

Figure 1.. Target-specific V_m dynamics in S1 projection neurons during task performance.

(A) Top, the experimental setup. Bottom, a representative two-photon image of a CTB-labeled M1-p neuron (green) with a recording pipette (red). (B) Detection task trial structure (FA: false alarm, CR: correct rejection). (C) Behavioral performance during whole-cell recordings (HR: hit rates, FAR: false alarm rates, GP: ‘Good performer’, N: ‘Naive’). (D, E) Left, grand average changes in V_m (thick line: mean, thin lines: ± sem) and action potential (AP) firing rate for hit trials recorded from S2-p neurons (red) and M1-p neurons (blue) in ‘Good performer’ (D) and ‘Naive’ (E) mice (Arrow: 1 ms stimulation of the C2 whisker). A box plot indicates reaction time (1st lick). Right, box plots for postsynaptic potential (PSP) amplitude, secondary late V_m depolarization quantified at 0.05–0.25 s, V_m depolarization during the lick period (at 0.25–1.0 s), and evoked AP rates at early (0–0.05 s), late (0.05–0.25 s) and lick (0.25–1.0 s) periods. DOI: http://dx.doi.org/10.7554/eLife.15798.003

Figure 1—figure supplement 1.. Hit V_m traces from S1 projection neurons in ‘Good performer’ mice.

(A) Left and middle, example V_m traces obtained from two individual S2-p neurons on two representative hit trials. Right, the averaged subthreshold V_m trace is superimposed with individual traces. APs are truncated. PSTHs for corresponding AP rates and the distribution of the first lick timings are also shown. (B) Same as A, but for M1-p neurons. DOI: http://dx.doi.org/10.7554/eLife.15798.007

Figure 1—figure supplement 2.. Hit V_m traces from S1 projection neurons in ‘Naive’ mice.

(A) Left and middle, example V_m traces obtained from two individual S2-p neurons on two representative hit trials. Right, the averaged subthreshold V_m trace is superimposed with individual traces. APs are truncated. PSTHs for corresponding AP rates and the distribution of the first lick timings are also shown. (B) Same as A, but for M1-p neurons. DOI: http://dx.doi.org/10.7554/eLife.15798.008

Figure 1—figure supplement 3.. Average hit V_m traces and PSTHs.

(A) Average hit V_m traces obtained from individual cells (thin lines) from S2-p (left) and M1-p (right) neurons of ‘Good performer’ mice. The grand average V_m traces (thick lines) are superimposed. The dotted line indicates the stimulus onset. (B) Left, grand average of subthreshold responses from S2-p (red) and M1-p (blue) neurons are shown at high temporal resolution (superimposed with the baseline V_m subtracted). An arrow indicates the onset of whisker stimulation. Middle, grand average PSTHs at high temporal resolution with the baseline AP rates subtracted. Time 0 is the onset of whisker stimulation. Right, quantification of evoked AP rate at initial 20 ms after whisker deflection. (C and D) Same as A and B, but for ‘Naive’ mice. (E) Quantification of △V_m and △AP rate at 0.05 – 0.35 s and 0.35 – 1.0 s on hit trials in ‘Naive’ mice. (F) PSP amplitude, V_m depolarization at the late (0.05–0.25 s) and lick (0.25 – 1.0 s) periods and evoked AP rates at early (0 – 0.05 s), late (0.05 – 0.25 s) and lick (0.25 – 1.0 s) periods were analyzed on a mouse-by-mouse basis for ‘Good performer’ mice (n = 9 mice for M1-p neurons; n = 17 mice for S2-p neurons). (G) Same as F, but for ‘Naive’ mice (n = 6 mice for M1-p neurons; n = 9 mice for S2-p neurons). DOI: http://dx.doi.org/10.7554/eLife.15798.009

Figure 1—figure supplement 4.. Target-specific changes of hit responses with task learning.

(A and B) Left, grand average changes in V_m (thick line: mean, thin lines: ± sem) and AP rate for hit trials recorded from S2-p neurons (A) and M1-p neurons (B) in ‘Good performer’ (colored) and ‘Naive’ (black) mice (Arrow: 1 ms stimulation of the C2 whisker). Right, box plots for PSP amplitude, V_m depolarization at the late (0.05–0.25 s) and lick (0.25 – 1.0 s) periods and evoked AP rates at early (0 – 0.05 s), late (0.05 – 0.25 s) and lick (0.25 – 1.0 s) periods. DOI: http://dx.doi.org/10.7554/eLife.15798.010

Figure 2.. Target-specific V_m correlation with task execution.

(A) Left, grand average V_m traces (thick line: mean, thin lines: ± sem) of S2-p neurons during hit (red) and miss (black) trials for ‘Good performer’ mice. Right, data for each cell (thin lines) and box plots for PSP amplitude and V_m depolarization at the late (0.05–0.25 s) and lick periods (0.25–1.0 s) on hit (H) and miss (M) trials. (B) Same as A, but for M1-p neurons. (C) Same as A, but for S2-p neurons in ‘Naive’ mice. (D) Same as C, but for M1-p neurons. DOI: http://dx.doi.org/10.7554/eLife.15798.011

Figure 2—figure supplement 1.. Representative hit/miss V_m traces.

(A) Example average subthreshold V_m traces on hit (colored) and miss (black) trials from four individual S2-p neurons in trained ‘Good performer’ mice. Arrows: the onset of whisker stimulus. Insets: PSPs of corresponding traces at high temporal resolution. (B) Same as A, but for M1-p neurons. (C) Same as A, but for S2-p neurons in ‘Naive’ mice. (D) Same as C, but for M1-p neurons. DOI: http://dx.doi.org/10.7554/eLife.15798.014

Figure 2—figure supplement 2.. Mouse-by-mouse analysis of hit/miss responses.

(A) Data from S2-p neurons in ‘Good performer’ mice averaged for each mouse (thin lines, n = 14 mice) and box plots for PSP amplitude and V_m depolarization at the late (0.05–0.25 s) and lick periods (0.25–1.0 s) on hit (H) and miss (M) trials. (B) Same as A, but for M1-p neurons (n = 7 mice). (C) Same as A, but for S2-p neurons in ‘Naive’ mice (n = 9 mice). (D) Same as C, but for M1-p neurons (n = 6 mice). DOI: http://dx.doi.org/10.7554/eLife.15798.015

Figure 3.. Target-specific V_m depolarization during spontaneous unrewarded licking.

(A, B) Left, grand average change in V_m (thick line: mean, thin lines: ± sem) and AP rate aligned at the onset of detected spontaneous licking (dotted line) in M1-p and S2-p neurons of ‘Good performer’ (A) and ‘Naive’ (B) mice. Right, quantifications at ± 0.1 s around the detected lick onset. DOI: http://dx.doi.org/10.7554/eLife.15798.016

Figure 3—figure supplement 1.. Licking-related V_m dynamics of S2-p and M1-p neurons in ‘Good performer’ mice.

(A) Left, an example V_m trace (below) from an S2-p neuron during spontaneous unrewarded licking and the corresponding lick-sensor signal (above). Right, individual lick-sensor signals (above) and Vm traces (below, thin lines; APs are truncated) aligned and superimposed at the onset of detected licking (the time when the tongue first contacted the water spout; dotted line), obtained from the cell shown on the left. The average subthreshold V_m trace (thick line) is superimposed. (B) Another example from an S2-p neuron different from the cell shown in A. (C) Same as A, but for an M1-p neuron. (D) Another example from an M1-p neuron different from the cell shown in C. DOI: http://dx.doi.org/10.7554/eLife.15798.019

Figure 3—figure supplement 2.. Licking-related V_m dynamics of S2-p and M1-p neurons in ‘Naive’ mice.

(A) Left, an example V_m trace (below) from an S2-p neuron during spontaneous unrewarded licking and the corresponding lick-sensor signal (above). Right, individual lick-sensor signals (above) and V_m traces (below, thin lines; APs are truncated) superimposed and aligned at the onset of detected licking (the time when the tongue first contacted the water spout; dotted line), obtained from the cell shown on the left. The average subthreshold V_m trace (thick line) is superimposed. (B) Another example from an S2-p neuron different from the cell shown in A. (C) Same as A, but for an M1-p neuron. (D) Another example from an M1-p neuron different from the cell shown in C. DOI: http://dx.doi.org/10.7554/eLife.15798.020

Figure 3—figure supplement 3.. Further analysis of V_m dynamics during spontaneous unrewarded licking.

(A, B) Left, grand average change in V_m (thick line: mean, thin lines: ± sem) and AP rate aligned at the onset of detected spontaneous licking (dotted line) in S2-p (A) and M1-p (B) neurons of ‘Good performer’ and ‘Naive’ mice. Right, quantifications at ± 0.1 s around the detected lick onset. (C) The lick-related change of V_m and AP rate was analyzed on a mouse-by-mouse basis for ‘Good performer’ mice (n = 7 mice for M1-p neurons; n = 15 mice for S2-p neurons). (D) Same as C, but for ‘Naive’ mice (n = 7 mice for M1-p neurons; n = 9 mice for S2-p neurons). DOI: http://dx.doi.org/10.7554/eLife.15798.021

Figure 4.. Schematic summary of target-specific output signals from S1 during execution of the whisker detection task, together with speculative hypothesis relating to possible cortico-cortical signalling pathways from S1 to tongue/jaw area of motor cortex.

Left, In ‘Good performer’ mice, S2-p neurons, not M1-p neurons, in S1 develop depolarization correlated with task performance. The activities of S2-p neurons could be routed toward the tongue/jaw area of M1/M2 (tjM1/M2). Right, In ‘Naive’ mice, M1-p neurons, not S2-p neurons, exhibit depolarization correlated with task execution. wM1: whisker M1. DOI: http://dx.doi.org/10.7554/eLife.15798.022