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Trace Eyeblink Conditioning in Mice Is Dependent upon the Dorsal Medial Prefrontal Cortex, Cerebellum, and Amygdala: Behavioral Characterization and Functional Circuitry(1,2,3).

Siegel JJ, Taylor W, Gray R, Kalmbach B, Zemelman BV, Desai NS, Johnston D, Chitwood RA - eNeuro (2015)

Bottom Line: To identify the circuitry involved, we made restricted lesions of the medial prefrontal cortex (mPFC) and found that learning was prevented.Anatomical data from these critical regions showed that mPFC and amygdala both project to the rostral basilar pons and overlap with eyelid-associated pontocerebellar neurons.The data further reveal a specific role for the amygdala as providing a conditioned stimulus-associated input to the cerebellum.

View Article: PubMed Central - HTML - PubMed

Affiliation: Center for Learning and Memory, University of Texas at Austin , Austin, Texas 78712.

ABSTRACT
Trace eyeblink conditioning is useful for studying the interaction of multiple brain areas in learning and memory. The goal of the current work was to determine whether trace eyeblink conditioning could be established in a mouse model in the absence of elicited startle responses and the brain circuitry that supports this learning. We show here that mice can acquire trace conditioned responses (tCRs) devoid of startle while head-restrained and permitted to freely run on a wheel. Most mice (75%) could learn with a trace interval of 250 ms. Because tCRs were not contaminated with startle-associated components, we were able to document the development and timing of tCRs in mice, as well as their long-term retention (at 7 and 14 d) and flexible expression (extinction and reacquisition). To identify the circuitry involved, we made restricted lesions of the medial prefrontal cortex (mPFC) and found that learning was prevented. Furthermore, inactivation of the cerebellum with muscimol completely abolished tCRs, demonstrating that learned responses were driven by the cerebellum. Finally, inactivation of the mPFC and amygdala in trained animals nearly abolished tCRs. Anatomical data from these critical regions showed that mPFC and amygdala both project to the rostral basilar pons and overlap with eyelid-associated pontocerebellar neurons. The data provide the first report of trace eyeblink conditioning in mice in which tCRs were driven by the cerebellum and required a localized region of mPFC for acquisition. The data further reveal a specific role for the amygdala as providing a conditioned stimulus-associated input to the cerebellum.

No MeSH data available.


Related in: MedlinePlus

Example histology from two mice showing infusion sites targeting the central nucleus of the amygdala, the distribution of amygdala terminals in the basilar pons, and a lack of substantial label in the RTN and mPFC. A, Infusions of Alexa-conjugated dextran included the central nucleus in both cases. B, Amygdala terminal labeling was observed primarily in the anterior basilar pons, with sparse terminals observed in the caudal basilar pons and RTN. C, Terminal labeling as a result of amygdala central nucleus infusions was not observed in the region of mPFC critical for trace eyeblink conditioning. Br, Bregma; CeA, central nucleus of the amygdala; BLA, basolateral nuclues of the amygdala; ml, medial lemniscus; py, pyramidal tract; AGm, medial agranular cortex; AC, anterior cingulate cortex. Scale bar, 250 µm.
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Figure 12: Example histology from two mice showing infusion sites targeting the central nucleus of the amygdala, the distribution of amygdala terminals in the basilar pons, and a lack of substantial label in the RTN and mPFC. A, Infusions of Alexa-conjugated dextran included the central nucleus in both cases. B, Amygdala terminal labeling was observed primarily in the anterior basilar pons, with sparse terminals observed in the caudal basilar pons and RTN. C, Terminal labeling as a result of amygdala central nucleus infusions was not observed in the region of mPFC critical for trace eyeblink conditioning. Br, Bregma; CeA, central nucleus of the amygdala; BLA, basolateral nuclues of the amygdala; ml, medial lemniscus; py, pyramidal tract; AGm, medial agranular cortex; AC, anterior cingulate cortex. Scale bar, 250 µm.

Mentions: To further define the putative functional pathway between the mPFC and amygdala with cerebellar eyeblink regions in mice, we examined pontine regions for overlap between mPFC and amygdala terminal fields with cells that were retrogradely labeled during cerebellar control infusions (n = 6 mice in which muscimol infusions abolished CRs; Fig. 8A). To this end, mice receiving the chronically implanted cerebellar cannula were also injected in the mPFC with a rAAV to express the fluorescent protein tdTomato in prefrontal neurons and their axon terminals. The mPFC injections were targeted to the identical regions deemed necessary for acquisition of trace 50–250 from our lesion experiment (between bregma +1.75 and +0.75; Fig. 10A,B, left). Amygdala central nucleus terminal fields were anterogradely labeled with AlexaFluor-conjugated dextran during control infusions (n = 6 mice in which muscimol infusions disrupted CR expression; see Fig. 12A).


Trace Eyeblink Conditioning in Mice Is Dependent upon the Dorsal Medial Prefrontal Cortex, Cerebellum, and Amygdala: Behavioral Characterization and Functional Circuitry(1,2,3).

Siegel JJ, Taylor W, Gray R, Kalmbach B, Zemelman BV, Desai NS, Johnston D, Chitwood RA - eNeuro (2015)

Example histology from two mice showing infusion sites targeting the central nucleus of the amygdala, the distribution of amygdala terminals in the basilar pons, and a lack of substantial label in the RTN and mPFC. A, Infusions of Alexa-conjugated dextran included the central nucleus in both cases. B, Amygdala terminal labeling was observed primarily in the anterior basilar pons, with sparse terminals observed in the caudal basilar pons and RTN. C, Terminal labeling as a result of amygdala central nucleus infusions was not observed in the region of mPFC critical for trace eyeblink conditioning. Br, Bregma; CeA, central nucleus of the amygdala; BLA, basolateral nuclues of the amygdala; ml, medial lemniscus; py, pyramidal tract; AGm, medial agranular cortex; AC, anterior cingulate cortex. Scale bar, 250 µm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4596016&req=5

Figure 12: Example histology from two mice showing infusion sites targeting the central nucleus of the amygdala, the distribution of amygdala terminals in the basilar pons, and a lack of substantial label in the RTN and mPFC. A, Infusions of Alexa-conjugated dextran included the central nucleus in both cases. B, Amygdala terminal labeling was observed primarily in the anterior basilar pons, with sparse terminals observed in the caudal basilar pons and RTN. C, Terminal labeling as a result of amygdala central nucleus infusions was not observed in the region of mPFC critical for trace eyeblink conditioning. Br, Bregma; CeA, central nucleus of the amygdala; BLA, basolateral nuclues of the amygdala; ml, medial lemniscus; py, pyramidal tract; AGm, medial agranular cortex; AC, anterior cingulate cortex. Scale bar, 250 µm.
Mentions: To further define the putative functional pathway between the mPFC and amygdala with cerebellar eyeblink regions in mice, we examined pontine regions for overlap between mPFC and amygdala terminal fields with cells that were retrogradely labeled during cerebellar control infusions (n = 6 mice in which muscimol infusions abolished CRs; Fig. 8A). To this end, mice receiving the chronically implanted cerebellar cannula were also injected in the mPFC with a rAAV to express the fluorescent protein tdTomato in prefrontal neurons and their axon terminals. The mPFC injections were targeted to the identical regions deemed necessary for acquisition of trace 50–250 from our lesion experiment (between bregma +1.75 and +0.75; Fig. 10A,B, left). Amygdala central nucleus terminal fields were anterogradely labeled with AlexaFluor-conjugated dextran during control infusions (n = 6 mice in which muscimol infusions disrupted CR expression; see Fig. 12A).

Bottom Line: To identify the circuitry involved, we made restricted lesions of the medial prefrontal cortex (mPFC) and found that learning was prevented.Anatomical data from these critical regions showed that mPFC and amygdala both project to the rostral basilar pons and overlap with eyelid-associated pontocerebellar neurons.The data further reveal a specific role for the amygdala as providing a conditioned stimulus-associated input to the cerebellum.

View Article: PubMed Central - HTML - PubMed

Affiliation: Center for Learning and Memory, University of Texas at Austin , Austin, Texas 78712.

ABSTRACT
Trace eyeblink conditioning is useful for studying the interaction of multiple brain areas in learning and memory. The goal of the current work was to determine whether trace eyeblink conditioning could be established in a mouse model in the absence of elicited startle responses and the brain circuitry that supports this learning. We show here that mice can acquire trace conditioned responses (tCRs) devoid of startle while head-restrained and permitted to freely run on a wheel. Most mice (75%) could learn with a trace interval of 250 ms. Because tCRs were not contaminated with startle-associated components, we were able to document the development and timing of tCRs in mice, as well as their long-term retention (at 7 and 14 d) and flexible expression (extinction and reacquisition). To identify the circuitry involved, we made restricted lesions of the medial prefrontal cortex (mPFC) and found that learning was prevented. Furthermore, inactivation of the cerebellum with muscimol completely abolished tCRs, demonstrating that learned responses were driven by the cerebellum. Finally, inactivation of the mPFC and amygdala in trained animals nearly abolished tCRs. Anatomical data from these critical regions showed that mPFC and amygdala both project to the rostral basilar pons and overlap with eyelid-associated pontocerebellar neurons. The data provide the first report of trace eyeblink conditioning in mice in which tCRs were driven by the cerebellum and required a localized region of mPFC for acquisition. The data further reveal a specific role for the amygdala as providing a conditioned stimulus-associated input to the cerebellum.

No MeSH data available.


Related in: MedlinePlus