Slide 1
Slide 1
Abuzar Mahmood
Katz Lab
The Cortico- Amygdalar Interaction Dynamics underlying Taste Perception & Action
Illustrations courtesy of Katie Kimbrell
Slide 2
Cortex
Amy
Recent and Ongoing Projects
Slide 3
Rosenstein & Oster , 1988
Grossman et al, 2008
The Inevitable Sensorimotor Transformation of Taste Information
Sweet or salty – (yum!)
Vs
Bitter or sour – (yuck!)
Start around 750-1250ms post-stimulus delivery (with some variability)
Lick
Gape
Slide 4
Recurrent Connectivity in the Taste Circuit
GC
Sensory Signals from Cranial Nerves
Carleton et al. 2010
Merlo et al. 2015
Yang et al. 2025
Yan
Brainstem
Thalamus
Limbic Regions
Slide 5
Recurrent Connectivity in the Taste Circuit
GC
Sensory Signals from Cranial Nerves
Carleton et al. 2010
Merlo et al. 2015
Yang et al. 2025
Slide 6
Background
GC neural response dynamics
Dynamics linked to onset of behavior
GC-Amygdala link
Results
GC-Amygdala dynamics are tightly linked
- And yet...asymmetric
- Asymmetric influences demarcate response states
- Neurons most deeply embedded in circuit show strongest encoding
Preliminary
Intra-state dynamics
Outline
Slide 7
Suc
NaCl
CA
Quin
Adapted from Flores et al. 2018
Experimental Setup:
Data acquisition
Slide 8
-500 -250 0 250 500 750 1000 1250 —— —— — —– —– —– —— ——
5 — 4 3 2 1 0
Time post-stimulus delivery (ms)
Firing Rate (Hz)
Unpalatable
Palatable
GC
YUM
YUCK
Katz et al. 2001 | Jones et al. 2007 | Mahmood et al. 2023
GC taste response dynamics
Slide 9
Quinine
1 sec
10
9
8
7
6
5
4
3
2
1
Simultaneously recorded neurons
Katz et al. 2001 | Jones et al. 2007 | Mahmood et al. 2023
-500 -250 0 250 500 750 1000 1250 —— —— — —– —– —– —— ——
5 — 4 3 2 1 0
Time post-stimulus delivery (ms)
Firing Rate (Hz)
Unpalatable
Palatable
GC
YUM
YUCK
Deeper dive:
What happens on single trials?
Slide 10
Variable GC Dynamics across trials
Sadacca et al . 2016
Slide 11
Sadacca et al , 2016, Mahmood* Baas-Thomas* et al. 2026
Ensemble state transitions reflect taste decision-making
![Gaping Rat [IMAGE] | EurekAlert! Science News Releases](./hamilos/media/ppt/media/image21.jpg "Picture 2")
Palatability state
Gape
Also true for ingestive behaviors
Slide 12
Katz et al. 2001 | Jones et al. 2007 | Mahmood et al. 2023
BLA
-500 -250 0 250 500 750 1000 1250 —— —— — —– —– —– —— ——
2 —– 1.5 1 0.5
Time post-stimulus delivery (ms)
Firing Rate (Hz)
Palatable
YUM
YUCK
BLA Taste Response Dynamics
Unpalatable
Slide 13
Lin et al, 2021
BLA input is needed for emotional processing in GC
Intact
GC
Change in # of significant neurons
BLA
Slide 14
Background
GC neural response dynamics
Dynamics linked to onset of behavior
GC-Amygdala link
Results
BLA-GC interaction dynamics
Outline
Slide 15
GC is carrying out taste processing in concert with other regions
BLA and GC dynamics, on-average, appear to be coordinated
BLA input to GC is important for palatability processing
Need a direct test of BLA-GC coordination and characterization of directional influence
Where does this leave us?
Slide 16
Predictions - Part 1
BLA population activity will evolve as a sequence of states
BLA-GC transition #2 will be coordinated
Slide 17
Mahmood et al. 2023
Stim-aligned
Transition-aligned
BLA
States in BLA Population Activity
Slide 18
BLA population activity will evolve as a sequence of states
BLA-GC transition #2 will be coordinated
Predictions - Part 1
Slide 19
Mahmood et al. 2023
Amygdala and GC couple into a unit to process palatability
GC
BLA
1
2
3
transition
% of datasets with high BLA-GC correlations
GC
BLA
GC
BLA
GC
BLA
Slide 20
Mahmood et al. 2023
Amygdala and GC couple into a unit to process palatability
1
2
3
transition
% of datasets with high BLA-GC correlations
Slide 21
Amygdala and GC couple into a unit to process palatability
1
2
3
transition
% of datasets with high BLA-GC correlations
Transition 1
GC
leads
BLA
leads
msec
Transition 2
Transition 3
msec
msec
Mahmood et al. 2026
Slide 22
What's next for BLA and GC?
Caveats of transition coordination analysis
Snapshots of interaction
Symmetric
Slide 23
BLA will be driving GC to transition into palatability state (driving transition #2), after which GC emits behavioral command *
Neurons involved in inter-region communication will have stronger taste encoding.
*
Lin et al. 2021
Bechara, et al. 1999
Schoeanbaum, et al. 1998
Predictions - Part 2
Slide 24
BLA influences GC on the way to amygdala-cortical coupling
Granger Causality
Region A
Region B
Signal
Amplitude
Time
C B * B history = B future
C A * A history +
Slide 25
BLA influences GC on the way to amygdala-cortical coupling
Spectral Granger Causality
Frequency (Hz)
Mahmood et al. 2026
-500 0 500 1000 1500
Slide 26
BLA will be driving GC to transition into palatability state (driving transition #2), after which GC emits behavioral command
Neurons involved in inter-region communication will have stronger taste encoding.
Predictions - Part 2
Slide 27
Input
History
History of
other neurons
History of
current neuron
…
Future of
current neuron
Embedding of neurons in the BLA-GC interactions is related to “tastiness”
Poisson Generalized Linear Modeling
Slide 28
Embedding of neurons in the BLA-GC interactions is related to “tastiness”
Output
to BLA
20%
12%
17%
Taste
Specificity
Palatability
GC neurons
Mean discriminability
Influenced
by BLA
Mean palatability (r)
Mahmood et al. 2026
Slide 29
Obligatory summary slide
GC taste responses reflect taste processing across successive epochs.
Ensemble analysis of single trials reveals coding to emerge suddenly across ensemble transition.
These transitions in turn drives behavior… probably by modulating a brainstem CPG .
The mechanism of construction of this transition involves coupling of GC and BLA into a functional unit.
System functions under spatial “hierarchies”
Slide 30
Background
GC neural response dynamics
Dynamics linked to onset of behavior
GC-Amygdala Link
Results
Preliminary
Intra-state dynamics
Calia-Bogan, Katz, and Mahmood (In Prep)
Outline
Slide 31
Incomplete list of papers from the lab using HMMs / changepoints for state transitions:
Jones, Lauren M., et al. “Natural Stimuli Evoke Dynamic Sequences of States in Sensory Cortical Ensembles.” Proceedings of the National Academy of Sciences, vol. 104, no. 47, Nov. 2007 , pp. 18772–77. DOI.org ( Crossref ), https://doi.org/10.1073/pnas.0705546104 .
Sadacca , Brian F., et al. “Sodium Concentration Coding Gives Way to Evaluative Coding in Cortex and Amygdala.” Journal of Neuroscience, vol. 32, no. 29, July 2012 , pp. 9999–10011. www.jneurosci.org, https://doi.org/10.1523/JNEUROSCI.6059-11.2012 .
Moran, Anan, and Donald B. Katz. “Sensory Cortical Population Dynamics Uniquely Track Behavior across Learning and Extinction.” The Journal of Neuroscience, vol. 34, no. 4, Jan. 2014 , pp. 1248–57. PubMed Central, https://doi.org/10.1523/JNEUROSCI.3331-13.2014 .
Sadacca , Brian F., et al. “The Behavioral Relevance of Cortical Neural Ensemble Responses Emerges Suddenly.” Journal of Neuroscience, vol. 36, no. 3, Jan. 2016 , pp. 655–69. www.jneurosci.org, https://doi.org/10.1523/JNEUROSCI.2265-15.2016 .
Mukherjee, Narendra, et al. “Impact of Precisely-Timed Inhibition of Gustatory Cortex on Taste Behavior Depends on Single-Trial Ensemble Dynamics.” eLife , edited by Laura L Colgin et al., vol. 8, June 2019 , p. e45968. eLife , https://doi.org/10.7554/eLife.45968 .
Lin, Jian-You, et al. “Perturbation of Amygdala-Cortical Projections Reduces Ensemble Coherence of Palatability Coding in Gustatory Cortex.” eLife , vol. 10, p. E65766. 2021 PubMed Central, https://doi.org/10.7554/eLife.65766. Accessed 25 Mar. 2025.
Mahmood, Abuzar, et al. “Coupled Dynamics of Stimulus-Evoked Gustatory Cortical and Basolateral Amygdalar Activity.” Journal of Neuroscience, vol. 43, no. 3, Jan. 2023 , pp. 386–404. www.jneurosci.org, https://doi.org/10.1523/JNEUROSCI.1412-22.2022 .
Svedberg, Daniel A., and Donald B. Katz. Neural Correlates of Rapid Familiarization to Novel Taste. bioRxiv , 9 May 2024 . bioRxiv , https://doi.org/10.1101/2024.05.08.593234 .
Baas-Thomas, Natasha, et al. “The Ingestive Response Reflects Neural Dynamics in Gustatory Cortex.” 2 Oct. 2025. Neuroscience, https://doi.org/10.1101/2025.10.01.679845.
Mahmood, Abuzar, et al. “Sensory and Palatability Coding of Taste Stimuli in Cortex Involves Dynamic and Asymmetric Cortico- Amygdalar Interactions.” 4 July 2025. Neuroscience, https://doi.org/10.1101/2025.07.01.662567 .
States in GC assuming uniform emissions
Slide 32
Egest
Ingest
Miller and Katz 2010; 2013, Mazzucato et al. 2015
I’d recommend not motivating this simply with “when you look closer…”; I’d go with something more theory-driven, about how it makes sense that there should be internal dynamics, and also talk about the problem of explaining why the state transitions happen when they happen (which you can then expand upon when you get to the slide about external vs internal driving).
Attractor dynamics
Slide 33
Potential Intra-state Dynamics
Slide 34
Adapted from Jones et al. 2007
Vincent Calia-Bogan
If we do look closer…
Slide 35
Intra-state dynamics underlie state transitions and decision-making in go/no go tasks in mice
Adapted from Luo et al. 2023. See also Lindermann et al. 2020 and Escola et al. 2011
Existing literature: various models with intra-state dynamics fit quite well
Gap: None of these models actually characterize how the state dynamics are related to neural processing.
Goal: link back to neural mechanisms underlying state transitions.
Z0
Z1
Current Literature
Slide 36
Competing mechanisms underlying intra-state dynamics
H1 : Observed state transitions are externally triggered
GC intra-state dynamics are “clipped” differently on different trials
H2 : Internal dynamics trigger state transitions
Intra-state dynamics reach an “end-point”
Adapted from Carlton et al. 2010 and Merlo et al. 2015
Internally vs Externally-driven Dynamics
Slide 37
Autoencoder --> N onlinear dimensionality reduction
LSTM --> temporal relationship
Population Dynamics: Autoencoder RNN
Slide 38
Trial 9
Trial 10
Lat 1
Lat 2
Lat 4
Lat 3
HMM <-> RNN Convergent results
Slide 39
Smooth, non-uniform dynamics
Alpha (8-10Hz) oscillations
Stay tuned for testing of mechanistic hypotheses
Lat 1
Lat 2
Lat 4
Lat 3
Lat 1
Lat 2
Lat 4
Lat 3
Two primary types of dynamics
Slide 40
Obligatory summary slide
GC taste responses reflect taste processing across successive epochs.
Ensemble analysis of single trials reveals coding to emerge suddenly across ensemble transition.
These transitions in turn drives behavior… probably by modulating a brainstem CPG .
The mechanism of construction of this transition involves coupling of GC and BLA into a functional unit.
System functions under spatial and temporal “hierarchies”
Slide 41
Amygdala as a modulator for learning rate / encoding volatility
Changes in Amygdala response / GC-BLA interaction through the session
GC-BLA-Thalamus interaction
Explanation in terms of Global Workspace Theory
Redundant vs. synergistic processing
Future directions
Slide 42
Taste-Dopamine axis questions / thoughts
Single-trial link between onset of behavior in passive taste paradigm and dopamine ramps?
Effect of dopamine ramps on behavior is dependent on inter-region connections / network context?
That’s why activating VTA by itself does not generate behavior?
Existence of vectorized / contextualized RPE in VTA suggests top-down modulated (Langdon and Schoenbaum)
What influences? Any feedback from reward circuit to sensory?
- Competition between learned task and urgency for consumption occurs at what level?
Slide 43
- The Katz
- The Katz lab
- Jessica Steindler
- Hannah Germaine
- Vincent Calia-Bogan
Acknowledgements
Rattus Norvegicus
Slide 44
Thank you for your attention.
GC taste response dynamics
-500 -250 0 250 500 750 1000 1250 —— —— — —– —– —– —— ——
5 — 4 3 2 1 0
Time post-stimulus delivery (ms)
Firing Rate (Hz)
Unpalatable
Palatable
GC
YUM
YUCK
Katz et al. 2001 | Jones et al. 2007 | Mahmood et al. 2023
Population Dynamics: PCA
PCA limitations:
No temporal dependencies (as part of model)
Only linear relationships
Single trial
Supplemental: RNN works well
Comparison of binned firing rates and RNN-inferred firing rates:
Time (bins)
Firing rate
Time (bins)
Time (bins)
Unit 1
Unit 2
Unit 3
Unit 2
RNN
Binned
Population dynamics: cleaning via PCA
RNN Single trial
Slide 49
Effect of BLA perturbation on GC processing
- Bechara, A., et al. “ Different Contributions of the Human Amygdala and Ventromedial Prefrontal Cortex to Decision-Making. “ 1999, https://doi.org/10.1523/JNEUROSCI.19-13-05473.1999.
- Schoenbaum, G., et al. “ Neural Encoding in Orbitofrontal Cortex and Basolateral Amygdala during Olfactory Discrimination Learning .” 1999, https://doi.org/10.1523/JNEUROSCI.19-05-01876.1999.
Slide 50
Alignment of ingestive behaviors and GC dynamics
Slide 51
GLM Fit Quality Assessment
Slide 52
STATES IN BLA POPULATION ACTIVITY
Mahmood et al. 2023
Destroy population coordination
Destroy sharp changes
Trial 1
Trial 2
Slide 53
Samuelsen 2013
Slide 54
Saravani 2019, epoch
Slide 55
Forseth 2021 – distributed interaction
Slide 56
Global Workspace Theory
(Gaillard 2009)
Bouaichi 2020, Licking-related GC Dynamics
Slide 58
Mahmood et al, 2022
GC
BLA
Ctx
Amyg
Ctx
Amyg
Ctx
Amyg
Amygdala and GC become a unit to process palatability
GC
BLA
Slide 59
0.25
Gustatory cortical (GC) response dynamics culminate in decision-related firing
Mahmood, et al. , 2022
Slide 60
Palatability state probability
Ensemble state transitions reflect taste decision-making
Sadacca et al , 2016
Gaping period!
Slide 61
Testing this characterization of GC taste processing
By manipulating palatability
Fontanini & Katz, 2006 (Reduction of arousal)
Grossman et al ., 2008, Moran & Katz, 2014 (taste aversion)
By challenging identity
Yoshida & Katz, 2010 (Taste discrimination [2AFC])
By directly changing gape latency
Li et al., 2016 (cuing aversive taste)
By perturbing GC activity
Mukherjee et al., 2019 (0.5 sec optogenetic silencing)
Slide 62
Sadacca , et al ., 2016
Mahmood, et al. , 2022
Single-neuron responses change suddenly when looked at in this way
Slide 63
Session 1
Session 2
Svedberg, in prep
Scariest fact: taste response dynamics evolve over brief experience
Trial order: top to bottom
Slide 64
This evolution impacts taste response discriminability
Chance
Svedberg, in prep
Slide 65
Sadacca et al , 2016, Baas-Thomas*, Mahmood* et al. 2026
Ensemble state transitions reflect taste decision-making
Palatability state
Gape
Also true for ingestive behaviors
Slide 66
GC is causally involved in initiation of behavior
GC
Mukherjee et al , 2019
None
Before
Transition
After
Transition
Slide 67
Peri-transition time ( ms )
Lin et al, 2021
BLA is necessary for sharp transitions in GC
Onset of palatability response
Intact
BLA-> GCx
Intact
GC
BLA