Location
Suwanee, GA
Start Date
6-5-2025 1:00 PM
End Date
6-5-2025 4:00 PM
Description
Introduction: While the functions of many amygdalar circuits have been widely studied, the role of the direct amygdalo-auditory cortex (AM-AC) circuit is unknown.
Objective: Understand the function of the direct projection from the amygdala to the auditory cortex.
Methods: Two experiments were performed. In Experiment 1:Electrophysiology was utilized to record single and multi-unit responses from the auditory cortex. Optogenetic activation or deactivation of the amygdalo-auditory cortex circuit was then utilized to examine changes to auditory neuron firing rate during normal and deactivation scenarios. In Experiment 2, the protocols for experiment 1 were tested in animals with a sound-induced tinnitus to determine whether deactivation of the amygdalo-auditory cortex circuit would influence the tinnitus perception. In both experiments, fluorescent labeling from the optogenetic injection was examined in the amygdala and auditory cortex.
Results: The optogenetic vector construct provided both anterograde and retrograde labeling. The injection site was isolated to the lateral and basal nuclei of the amygdala. Labeled neurons included pyramidal and multipolar cells. Within the auditory cortex, a few pyramidal neurons were observed bilaterally throughout both primary and secondary areas of the auditory cortex. In addition, a large number of en-passant and terminal boutons were observed throughout layers 1-6 but predominantly in layers 5 and 6. Recording of neurons in the auditory cortex were characterized by best frequency. Deactivation of the amygdala projection to auditory cortex caused a significant inhibition of cortical firing rates in both multiunit and single-unit recordings. This inhibition occurred only during the time of the amygdala projection deactivation. In our tinnitus animals, the tinnitus was eliminated during the amygdala projection deactivation. However, the tinnitus immediately recovered when the pathway was released from deactivation.
Conclusion: While most of the amygdalar projection neurons to the auditory cortex are pyramidal (i.e., glutamatergic), the overall influence of the pathway was inhibitory. Therefore, this pathway is likely to contact inhibitory circuits within the cortex. The timing of inhibition and release from inhibition occurred within a manner of milliseconds. No long-term effects were observed. Therefore, we hypothesize that the amygdalo-auditory cortex circuit may provide quick modulatory influences on cortex that may help to prime cortical circuits for subsequent inputs from the nucleus basalis (a projection that has longer-lasting influences on cortical function).
Embargo Period
5-29-2025
Included in
Optogenetic deactivation of amygdalo-auditory cortex circuit
Suwanee, GA
Introduction: While the functions of many amygdalar circuits have been widely studied, the role of the direct amygdalo-auditory cortex (AM-AC) circuit is unknown.
Objective: Understand the function of the direct projection from the amygdala to the auditory cortex.
Methods: Two experiments were performed. In Experiment 1:Electrophysiology was utilized to record single and multi-unit responses from the auditory cortex. Optogenetic activation or deactivation of the amygdalo-auditory cortex circuit was then utilized to examine changes to auditory neuron firing rate during normal and deactivation scenarios. In Experiment 2, the protocols for experiment 1 were tested in animals with a sound-induced tinnitus to determine whether deactivation of the amygdalo-auditory cortex circuit would influence the tinnitus perception. In both experiments, fluorescent labeling from the optogenetic injection was examined in the amygdala and auditory cortex.
Results: The optogenetic vector construct provided both anterograde and retrograde labeling. The injection site was isolated to the lateral and basal nuclei of the amygdala. Labeled neurons included pyramidal and multipolar cells. Within the auditory cortex, a few pyramidal neurons were observed bilaterally throughout both primary and secondary areas of the auditory cortex. In addition, a large number of en-passant and terminal boutons were observed throughout layers 1-6 but predominantly in layers 5 and 6. Recording of neurons in the auditory cortex were characterized by best frequency. Deactivation of the amygdala projection to auditory cortex caused a significant inhibition of cortical firing rates in both multiunit and single-unit recordings. This inhibition occurred only during the time of the amygdala projection deactivation. In our tinnitus animals, the tinnitus was eliminated during the amygdala projection deactivation. However, the tinnitus immediately recovered when the pathway was released from deactivation.
Conclusion: While most of the amygdalar projection neurons to the auditory cortex are pyramidal (i.e., glutamatergic), the overall influence of the pathway was inhibitory. Therefore, this pathway is likely to contact inhibitory circuits within the cortex. The timing of inhibition and release from inhibition occurred within a manner of milliseconds. No long-term effects were observed. Therefore, we hypothesize that the amygdalo-auditory cortex circuit may provide quick modulatory influences on cortex that may help to prime cortical circuits for subsequent inputs from the nucleus basalis (a projection that has longer-lasting influences on cortical function).