Informational Powerpoint presented with oral presentation to Neurobiology class outlining the use of optogenetics, chemogenetics and behavioral analysis in mapping neural circuits.

1. Exploring the Neural Circuitry
of Predatory Pursuit, Capture,
and Kill
Ashley Kent Williamson

2. Obstacle
The decision to pursue prey in a natural habitat relies on
a complex combination of sensory stimulation and can
be difficult to replicate in a laboratory environment.
Solution
Using the techniques of chemogenetics and optogenetics
to bypass this obstacle, researchers at Yale University
were able to determine that the process of predatory
pursuit, capture, and kill occurs within two distinct
neural networks originating from the central nucleus of
the amygdala (CeA).

3. Overview of the techniques
Optogenetic Method
• Used viral vector to genetically
modify target neurons to respond
when stimulated by a specific
wavelength of light (480nm) by
inserting light-gated ion channel
(Channelrhodopsin2)
• Inserted optical fibers to transmit
light from laser to target site of CeA
within the medial temporal lobe.
• Used for studying immediate
behavioral effects because of the
short duration between applying
the light stimulus and the activation
or deactivation of target neurons.

4. Overview of the techniques continued
Chemogenetic Method
• Used Cre-dependent virus specifically targeted for a
specific receptor (glutamatergic or GABAergic) in
combination with the viral vector that would insert
Channelrhodopsin2 into only the neurons containing
those targeted receptors.
• Cre-dependent virus, when activated by clozapine N-
oxide (CNO), can be used to chemically lesion neurons by
encoding caspases, that cause specific targeted cells to
enter programmed cell death.
• Most appropriate in long-term behavioral studies

5. How to remember the two pathways being discussed:
CeA to parvocellular reticular formation (PCRt)
• parvo = small
• pathway associated with delivering lethal bites to “small” prey
(crickets)
CeA to periaqueductal grey (PAG)
• peri = surrounding or around
• pathway associated with pursuing prey “all around”

6. CeA=>PCRt only
Results of Activation
• Induced fictive feeding in
absence of food
• Sustained mastication
(chewing) of non-food items
Results of Inactivation
• Can pursue prey but unable to
deliver a lethal bite
• Catches prey with forepaws
and head kept close to body
What do the results indicate?
• Indicates that this pathway
controls the jaws and neck
movements involved in
predatory capture and kill
Example of “fictive feeding”
Example: Inability to deliver lethal bites

7. CeA => PAG
Results of Activation
• Increased speed of pursuit
• Shortened latency to pursue
• Overall duration of hunting reduced
Results of Inactivation
• Ten-fold increase in latency to pursue
What do these results indicate?
• Indicates that this pathway controls decision to pursue and coordination of the
body to effectively capture prey

8. Both pathways stimulated
CeA=>PCRt + CeA=>PAG
Results (as expected)
• Reduced time to initiate pursuit and
time to deliver lethal bite (overall
hunting efficiency increased)
• Attack of inanimate objects when no
food was accessible
• Fictive feeding observed when no
inanimate objects or food was
accessible
Unexpected Results
• No attacks on conspecifics
• Hungry mice demonstrated a more
intense pursuit, capture, and kill than
satiated mice but did not eat more
overall
What are the possible indications from the
unexpected results?
• Lack of conspecific attack indicates that
these two pathways are distinct from
aggression
• Lack of increased intake of food
indicates that predatory pursuit, capture
and kill is opportunistic and involved in
obtaining food not necessarily increasing
appetite

9. Discussion of Experimental Results
• Supports that CeA =>PCRt pathway controls the cervical-mandibular
neuromuscular command during predatory hunting based on both the
increased effectiveness of using the neck and jaw when activated and inability
to coordinate these muscles correctly when inactivated.
• Supports CeA => PAG pathway controls the decision to initiate pursuit of prey
and capture based on decreased time to initiate pursuit and use of forepaws in
lieu of jaws to capture when activated. And by the ten-fold increase in time to
initiate pursuit when inactivated.
• Unexpected results of lack of conspecific attack and no increase of intake of
food unlocks possibilities for future behavioral studies to pursue.
• Overall, an excellent example of how experimental methods of chemogenetics,
optogenetics and behavioral observation can be used together to study the
effects of neuronal circuitry.

10. References
Han, W. et al., (2017). Integrated control of predatory hunting
by the central nucleus of the amygdala. Cell, 168(1-2), 311-
324.e18. doi:10.1016/j.cell.2016.12.027
Acrobat mouse performs splits over two leaves in adorable
photos. (2018, July 2). Retrieved December 1, 2019, from
http://www.storytrender.com/60555/acrobat-mouse-
performs-splits-over-two-leaves-in-adorable-photos/.