AAV9-CAG-GCaMP6f

The auditory striatum is a sensory part of the dorsal striatum that plays a crucial role in learning and memory. However, in contrast to its role and underlying mechanisms in operant conditioning, little is known about its contribution to classical auditory fear conditioning. Here, researchers reveal the role of the auditory striatum in auditory-conditioned fear memory. They found that optogenetic inhibition of auditory striatal neurons impaired fear memory formation, which was mediated through the striatum-amygdala pathway. Using calcium imaging in behaving mice, researchers found that the responses of auditory striatal neurons to conditioned tones were enhanced during memory acquisition and expression. Furthermore, nigrostriatal dopaminergic projections play an important role in mediating conditioning-induced striatal enhancement. Together, these findings demonstrate the existence of a nigrostriatal-amygdala circuit for conditioned fear memory formation and expression.

Here, researchers injected AAV9-CAG-GCaMP6f into the auditory striatum and implanted a GRIN lens above the injection site (Figure 1a). Researchers allowed the virus to incubate and express for at least 3 weeks before implanting the baseplate. Seven days after baseplate implantation, mice were habituated to the camera mount for 4 days before auditory fear conditioning. GCaMP6f signals from auditory striatal neurons were recorded during each task session. In collected images, regions of interest (ROI) were detected by CNMF-E and registered using the CellReg function, which facilitated the recording of auditory striatal neurons throughout habituation, conditioning, and probe sessions (Figure 1b). Recordings from each neuronal ROI were aligned to the onset of the conditioning tone and sorted based on the amplitude of the tone response within a 1-second time window. The peak Z-score, which represents the change in fluorescence in response to the tone, was measured and plotted for each task session (Figure 1c, top). The number of neurons whose activity increased, decreased, or remained unchanged in response to the tone was quantified (Figure 1c, bottom). The number of neurons with increased responses to the conditioning tone increased significantly during the conditioning and first probe sessions (Figure 1d). Interestingly, tone responses increased gradually and significantly during the conditioning sessions for the eight conditioning tones (Figure 1e).

Figure 1. Auditory fear conditioning potentiates conditioned tone-induced activity in the auditory striatum. (Chen A P F, et al., 2023)