Journal: iScience

Article Title: Amplitude- and frequency-dependent activation of layer II/III neurons by intracortical microstimulation

doi: 10.1016/j.isci.2023.108140

Figure Lengend Snippet: Spatial characterization of neuronal responses to electrical stimulation (A) Heat maps of calcium signals from TPM evoked by different current amplitudes of stimulation (20, 40, and 100 μA) at different locations away from the stimulation electrode (outside of the field of view on the top). (B) Neurons’ maximal calcium responses in relation to their distance to the stimulating electrode. Note that the responses peak at ∼200 μm away from the stimulating electrode and remarkably decrease at ∼500 μm away. (C) Amplitudes of calcium signals evoked by various levels of stimulation in relation to the distance to the stimulating electrode. Data are shown as LOWESS fitting curves (GraphPad Prism 9). (D) Activation threshold versus neuronal location relative to the stimulating electrode. Note that the activation threshold increases fast over 400 μm away. (E) Ratio of activated neurons with buildup, sustained, and transient types of calcium responses in relation to the distance to the stimulating electrode. (F) Amplitude-dependent dynamics of responses of two examples cells located at different distances from the stimulation electrode. The orange insets show zoomed in review of responses to 20 μA stimulation. (G) Ratio of neurons with buildup, sustained, and transient types of calcium responses in relation to stimulation amplitude at different distances from the stimulation electrode. Data are shown as mean ± SEM of six animals with a total of 2275 activated neurons (379 ± 53 neurons in each animal) analyzed in B, D, and E. Gray lines in B and D represent individual animal.

Article Snippet: Solid lines are LOWESS fitting curves (GraphPad Prism 9). (G) Enlarged view of (F) to show that 4 out of 6 animals showed saturated calcium responses at around 400 V/m.

Techniques: Activation Assay

Journal: iScience

Article Title: Amplitude- and frequency-dependent activation of layer II/III neurons by intracortical microstimulation

doi: 10.1016/j.isci.2023.108140

Figure Lengend Snippet: Relationship between neuronal responses and local electrical field (E-field) (A) E-field simulation configuration. Electrode shank angle and stimulation electrode depth were determined by OCT image. E-field at the TPM imaging plane was simulated. (B) An example E-field map of 100 μA stimulation at the TPM imaging plane with the center directly at the stimulation electrode in x and y locations. (C) E-field map of a 100 μA stimulation in the ROIs of TPM imaging of an example animal. x and y axes show the relative distance to the stimulating electrode. (D) Calcium responses to the electrical stimulation corresponding to (C). Note the alignment of E-field strength in (C) and calcium response amplitude in (D). (E) Relationship between calcium response and E-field at different stimulation amplitudes extracted from the example animal in (C) and (D). Regardless of the stimulation amplitude, the relationship between calcium response and E-field remains the same. (F) Summary of the relationship between calcium response and E-field of 6 animals at a stimulation level of 100 μA. Each color represents one animal. Solid lines are LOWESS fitting curves (GraphPad Prism 9). (G) Enlarged view of (F) to show that 4 out of 6 animals showed saturated calcium responses at around 400 V/m. One animal started showing saturation at about 175 V/m. (H) Linear regression demonstrated that below 400 V/m, calcium responses are linearly correlated to the E-field with a narrow range of slope. Each line represents one animal, and the black line is the linear regression analysis of all neurons from 6 animals.

Article Snippet: Solid lines are LOWESS fitting curves (GraphPad Prism 9). (G) Enlarged view of (F) to show that 4 out of 6 animals showed saturated calcium responses at around 400 V/m.

Techniques: Imaging