A striatal circuit balances learned fear in the presence and absence of sensory cues

  1. Michael Kintscher
  2. Olexiy Kochubey
  3. Ralf Schneggenburger

  • Curated by eLife

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    eLife assessment

    This paper will interest neuroscientists working in the field(s) of basal ganglia, amygdala, and fear learning. Overall this is an important study that examines the contribution of an understudied brain region to fear conditioning in male subjects. Some conclusions will benefit from additional verification and evaluation of the specificity of the findings to the amygdala-striatal transition zone relative to adjacent regions.

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Abstract

During fear learning, defensive behaviors like freezing need to be finely balanced in the presence or absence of threat-predicting cues (conditioned stimulus, CS). Nevertheless, the circuits underlying such balancing are largely unknown. Here, we investigate the role of the ventral tail striatum (vTS) in auditory-cued fear learning of male mice. In vivo Ca 2+ imaging showed that sizable sub-populations of direct (D1R+) and indirect pathway neurons (Adora+) in the vTS responded to footshocks, and to the initiation of movements after freezing; moreover, a sub-population of D1R+ neurons increased its responsiveness to an auditory CS during fear learning. In-vivo optogenetic silencing shows that footshock-driven activity of D1R+ neurons contributes to fear memory formation, whereas Adora+ neurons modulate freezing in the absence of a learned CS. Circuit tracing identified the posterior insular cortex (pInsCx) as an important cortical input to the vTS, and recording of optogenetically evoked EPSCs revealed long-term plasticity with opposite outcomes at the pInsCx synapses onto D1R+ - and Adora+ neurons. Thus, direct- and indirect pathways neurons of the vTS show differential signs of plasticity after fear learning, and balance defensive behaviors in the presence and absence of learned sensory cues.

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  1. Version published to 10.7554/elife.75703 on eLife
  2. eLife

    Author Response

    Reviewer #1 (Public Review):

    This work identifies distinct contribution of direct (D1+) and indirect (Adora+, D2+) amygdalostriatal medium spiny cells in fear learning and plasticity. The authors combined freely moving calcium imaging with auditory fear learning assay to reveal tone, foot-shock and behavior (movement)-evoked activity of the two MSN population. While D1+ cells show plastic changes driven by fear learning and reaching their maximum tone responsiveness (PSTH) at fear retrieval, Adore+ cells activation remained constant. Furthermore, using optogenetic silencing they showed that the two MSN groups differently contribute to retrieval of fear memory. Both cells receive topographically organized insular cortical inputs which go through learning-induced long-term synaptic changes with opposite direction: postsynaptic LTP at D1 cells, while presynaptic LTD at Adora+ cells. These synaptic changes provide some level of explanation for distinct behavioral contribution of the two cell types in fear learning.

    This study focuses on a so far neglected member of the 'extended' amygdalar circuitry, the amygdalostratal transition zone. The data is well-presented, the experiments are in logical order, built on each other and the paper is easy to read and follow.

    However, some information regarding the connectivity (and function) of Astr have been presented in recent and earlier papers are missing from, or contradicting with, the present work. One reason to explain these is that the targeted striatal regions vary between experiments, and so, it is difficult to judge when the Astr and when the other part of the caudal (tail) striatum is examined. As these striatal regions are involved in different neuronal networks, their functional consequences could also be distinct. Without precisely clarifying and consistently targeting the aimed striatal region, it is difficult to interpret the findings of the present study (though those are relevant and important).

    We thank this reviewer for his/her overall positive evaluation of our paper.

    We agree with the criticism that in the first submission, we have not stringently defined the anatomical region of the amygdala - striatal transition zone (AStria). After validating our previous data, and after performing new anatomical experiments studying the expression of Cre in the D1RCre and AdoraCre mouse lines used here (see Figure 1D; Figure 1 - figure supplement 1; Figure 3 - figure supplement 1), we now refer to the region targeted in our study as "ventral tail striatum" (vTS), as opposed to the more narrowly defined, and more ventrally located "AStria". Therefore, we have changed the word "AStria" to ventral tail striatum ("vTS") throughout the paper.

    We have also improved our introduction to the posterior striatum (p. 4 bottom, p. 5 top), and we briefly discuss the targeting of the vTS (as opposed to the AStria)(p. 19 top).

    Reviewer #2 (Public Review):

    Kintscher et al present a nice study on the responses of Adora2a and D1R expressing cells in the tail of the striatum/amygdala transition zone during auditory fear conditioning. Overall the conclusions are that (1) D1R cells show plasticity in activity patterns during the task, with the emergence of tone/movement co-modulated cells; (2) Adora2a cells show less of such changes; (3) gain of function of activity does little where (4) loss of function of activity in each cell class has moderate effects on the learned behavior (i.e. freezing to the CS). There is a nice section on rabies tracing which maps inputs to both cell types which then motivates an analysis of insular cortex inputs onto both cell types and reveals that (5) CS/US pairing alters insular inputs to both cell types.

    Overall the paper is well done and the conclusions are believable. Furthermore, this brain area is understudied yet potentially very important.

    The analysis of the fluorescence transients is heavy handed. This leads to potential for error and could obscure what appear to be large differences that could be extracted more easily. In some instances, the data are interpreted too optimistically, especially that the silencing experiments implicate plasticity of the neurons rather than the need for activity.

    We thank the reviewer for his/her positive evaluation of our paper. For the revision, we have re-analyzed the Ca-imaging data, and we have made changes in the text to avoid a too optimistic interpretation of our data.

  3. eLife

    eLife assessment

    This paper will interest neuroscientists working in the field(s) of basal ganglia, amygdala, and fear learning. Overall this is an important study that examines the contribution of an understudied brain region to fear conditioning in male subjects. Some conclusions will benefit from additional verification and evaluation of the specificity of the findings to the amygdala-striatal transition zone relative to adjacent regions.

  4. eLife

    Reviewer #1 (Public Review):

    This work identifies distinct contribution of direct (D1+) and indirect (Adora+, D2+) amygdalostriatal medium spiny cells in fear learning and plasticity. The authors combined freely moving calcium imaging with auditory fear learning assay to reveal tone, foot-shock and behavior (movement)-evoked activity of the two MSN population. While D1+ cells show plastic changes driven by fear learning and reaching their maximum tone responsiveness (PSTH) at fear retrieval, Adore+ cells activation remained constant. Furthermore, using optogenetic silencing they showed that the two MSN groups differently contribute to retrieval of fear memory. Both cells receive topographically organized insular cortical inputs which go through learning-induced long-term synaptic changes with opposite direction: postsynaptic LTP at D1 cells, while presynaptic LTD at Adora+ cells. These synaptic changes provide some level of explanation for distinct behavioral contribution of the two cell types in fear learning.

    This study focuses on a so far neglected member of the 'extended' amygdalar circuitry, the amygdalostratal transition zone. The data is well-presented, the experiments are in logical order, built on each other and the paper is easy to read and follow.

    However, some information regarding the connectivity (and function) of Astr have been presented in recent and earlier papers are missing from, or contradicting with, the present work. One reason to explain these is that the targeted striatal regions vary between experiments, and so, it is difficult to judge when the Astr and when the other part of the caudal (tail) striatum is examined. As these striatal regions are involved in different neuronal networks, their functional consequences could also be distinct. Without precisely clarifying and consistently targeting the aimed striatal region, it is difficult to interpret the findings of the present study (though those are relevant and important).

  5. eLife

    Reviewer #2 (Public Review):

    Kintscher et al present a nice study on the responses of Adora2a and D1R expressing cells in the tail of the striatum/amygdala transition zone during auditory fear conditioning. Overall the conclusions are that (1) D1R cells show plasticity in activity patterns during the task, with the emergence of tone/movement co-modulated cells; (2) Adora2a cells show less of such changes; (3) gain of function of activity does little where (4) loss of function of activity in each cell class has moderate effects on the learned behavior (i.e. freezing to the CS). There is a nice section on rabies tracing which maps inputs to both cell types which then motivates an analysis of insular cortex inputs onto both cell types and reveals that (5) CS/US pairing alters insular inputs to both cell types.

    Overall the paper is well done and the conclusions are believable. Furthermore, this brain area is understudied yet potentially very important.

    The analysis of the fluorescence transients is heavy handed. This leads to potential for error and could obscure what appear to be large differences that could be extracted more easily. In some instances, the data are interpreted too optimistically, especially that the silencing experiments implicate plasticity of the neurons rather than the need for activity.

  6. eLife

    Reviewer #3 (Public Review):

    Schneggenburger and colleagues set out to reveal roles for D1R+ and Adora+ amygdala-striatal transition zone neurons in fear learning. In the first two experiments, the authors expressed fluorescent calcium indicators in D1R+ or Adora+ neurons, measuring change in fluorescence during habituation, training and testing of tone-shock conditioning. In the next experiments, the authors expressed archeorhodopsin (or a control fluorophore) in D1R+ or Adora+ neurons and illuminated with yellow light just before and after foot shock delivery. Freezing was quantified during training and retrieval. Finally, retrograde tracing was performed to reveal direct synaptic inputs on D1R+ and Adora+ neurons.

    The paper is potentially interesting. However, some important weaknesses include: the authors use of only male mice, the lack of validation of the Cre lines used in the study, and the data acquisition pipeline.

  7. Version published to 10.1101/2021.12.09.471922v2 on bioRxiv
  8. Version published to 10.1101/2021.12.09.471922v1 on bioRxiv