Convergent Coding of Recent and Remote Fear Memory in the BLA

Convergent Coding of Recent and Remote Fear Memory in the Basolateral Amygdala

Jianfeng Liu, Michael S. Totty, Laila Melissari, Hugo Bayer, and Stephen Maren

Presentation by: Alexandra Rosas

BLA relevance to Fear memory (recent vs remote)

Introduction

Key Structures:

• Amygdala
• Basolateral amygdala

Previous figures:

• Extracellular recordings show that single BLA neurons show robust increases in spike firing to both CSremote and CSrecent.
• Fiber photometry recordings demonstrate that activity comes from principal neurons.

What next?

Fig 4

Hypothesis: Optogenetic silencing of bla principal neurons impairs short term memory, but not long term memory retrieval

Fig 4: Optoinhibition of BLA reduces freezing to both recent and remote CS in a within -subjects fear conditioning procedure.

4a

Experimental design

Methods

• Bilateral injections into the BLA ( one week prior to remote conditioning):

• Experimental group = Jaws (red shift inhibitory opsin)
• AAV9-CaMKII-Jaws-GFP

• Control Group = GFP virus
• AAV9-CaMKII-GFP

• Within-subject fear conditioning allows for comparison of neuronal and behavioral responses of recent and remote memories.

Timeline of the Experimental Design of Fig. 4

Day 1

Rats are microinjected with GFP or Jaws into the BLA.

Timeline of the Experimental Design of Fig. 4

Day 1

REMOTE CS: Subjects conditioned in context A.

<-*1 week*->

Day 7

Rats are microinjected with GFP or Jaws into the BLA.

Remote CS

• Subjects placed in "Context A"
• 3 min base line (BL)
• Tone-foot shock pairing (5x)

• CS remote:
• 10 s
• 80 dB
• 8 kHz
• Foot shock:
• 1 mA
• 2 s
• 70 s intertrial intervals (ITI)
• 60 s post shock period

Timeline of the Experimental Design of Fig. 4

Day 21

Day 1

REMOTE CS: Subjects conditioned in context A.

<-*2 weeks*->

RECENT CS: Subjects conditioned in context B.

Day 7

Rats are microinjected with GFP or Jaws into the BLA.

Recent CS

• Subjects placed in "Context B"
• 3 min base line (BL)
• Tone-foot shock pairing (5x)

• CS remote:
• 10 s
• 80 dB
• 2 kHz
• Foot shock:
• 1 mA
• 2 s
• 70 sec intertrial intervals (ITI)
• 60 sec post shock period

Timeline of the Experimental Design of Fig. 4

Day 21

Day 1

RETRIEVAL: 4 day counterbalancing procedure

REMOTE CS: Subjects conditioned in context A.

<-*1 day*->

RECENT CS: Subjects conditioned in context B.

Day 7

Day 22

Rats are microinjected with GFP or Jaws into the BLA.

Retrieval (Recent & Remote)

• Conducted one day after CS recent in "Context C"
• 4 day counterbalancing procedure
• Each session:
• 3 min BL
• 5x Tone alone (either recent or remote)
• 40 s ITIs
• Bilateral red light illumination (635 nm)
• Delivered 10 s before first tone onset, and persistet to end of testing session

Retrieval (Continued)

• Day 1 (Day 22): CSrecent with light ON
• Day 2 (Day 23): CSrecent with light OFF
• Day 3 (Day 24): CSremote with light ON
• Day 4 (Day 25): CSremote with light OFF

4b

Decreased firing rate due to Jaws.

• 35 cells (recorded BLA neurons in Jaws rats)

4c

Micrograph of the fiber placement and viral expression in BLA.

4d-i

Freezing data of CSrecent and CSremote during BLA manipulation of Jaws and GFP infected rats.

Freezing Data from Fig. 4 (Continued)

vs

• Rats expressing Jaws or GFP acquired similar levels of freezing during both CSrecent and CSremote.
• Open circle = GFP (control group)
• Filled circle = Jaws (experimental group)

Freezing Data from Fig. 4 (Continued)

vs

• Continuous optoinhibition of Jaws subjects reduced freezing significantly.
• Open circle = light OFF
• Filled circle = light ON

Freezing Data from Fig. 4 (Continued)

vs

Fig. S3 & S4 from Supplemental Information

Fig. S4

Fig. S3

Fig 5

Hypothesis: Inhibitory PV interneurons in BLA are potent inhibitors for pyramidal neurons, thus acting as a constraint for fear memory ensembles.

Fig 5: Optogenetic stimulation of PV interneurons in the BLA reduces conditioned freezing to a remote CS.

5a

Experimental design

Methods used in Fig. 5a

• Bilateral injections into the BLA of PV-cre transgenic mice (three weeks prior to remote conditioning):

• Control Group = tdTomato
• AAV8-FLEX-tdTomato
• blank control virus

• Experimental group = ChR2
• AAV8-DIO-ChR2-mCherry
• Cre-dependent excitatory opsin

Methods used in Fig. 5a

• Within-subjects fear conditioning procedure (CS-US pairing in "Context A"):
• 3 min base line (BL)
• Tone-foot shock pairing (5x)
• CS remote: 10 s, 80 dB, 2 kHz
• Foot shock: 1 mA, 2 s
• 70 s intertrial intervals (ITI)
• 60 s post shock period
• Remote memory retrieval tested 7 days later in "Context B":
• Counterbalanced manner
• Bilateral blue light illumination (450 nm)
• Delivered 10 s before tone onset and terminated at tone offset
• NOTE: No recent retrieval test conducted

5b

Micrograph depicting ChR2-mCherry expression and fiber placement.

5c

Micrograph showing that Cre-dependednt expression of ChR2-mCherry is specific to PV+ neurons.

5d-f

Freezing data of Cre-dependent rats infected with tdTomato and ChR2.

• Fig. 5d: tdTomato and ChR2 show freezing patterns during conditioning.
• Fig. 5e: During remote retrieval testing, optogenetic stimulation of BLA PV interneurons reduce freezing.
• Open = laser OFF
• Closed = laser ON
• Fig. 5f: Analysis of Fig. 5e summarizing that optogenetic stimulation of PV neurons impaired fear memory retrieval.

Conclusion (Continued)

• Optoinhibition of the BLA reduces freezing in both recent and remote CS in a within-subjects fear conditionig procedure
• Supports findings of first three figures:
• Convergent coding of recent and remote memory
• Recent and remote memory induce similar levels of c-Fos expression and CS-caused Ca2+ in BLA neurons.

• Optogenetic stimulation of PV interneurons in the BLA reduces conditioned freezing to a remote CS.
• Recent memory not needed for remote memory retrieval.

Conclusion (Continued)

Possible shortcomings/issues:

• Methological
• Morphological

New directions:

• Mechanisms behind function of BLA
• Neuromodulators
• Neuronal input to BLA during regulation of recent/remote memory retrieval.

Provides evidence that that BLA is a long term storage for emotional (fear) memory.

Works Cited

Liu, Jianfeng et al. “Convergent Coding of Recent and Remote Fear Memory in the Basolateral Amygdala.” Biological psychiatry vol. 91,9 (2022): 832-840. doi:10.1016/j.biopsych.2021.12.018Rajbhandari, Abha Karki. “Aversive Memory Storage in the Basolateral Amygdala: The Nut May Be Cracked.” Biological psychiatry vol. 91,9 (2022): e39-e40. doi:10.1016/j.biopsych.2022.02.958

Thank you :)

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With Genially templates, you can include visual resources to wow your audience. You can also highlight a particular sentence or piece of information so that it sticks in your audience’s minds, or even embed external content to surprise them: Whatever you like! Do you need more reasons to create dynamic content? No problem! 90% of the information we assimilate is received through sight and, what’s more, we retain 42% more information when the content moves.

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