Connectionists: REMINDER: World wide VVTNS series (6th season): June 10 2026 | Learning to Compose: Geometric Reorganization of Prefrontal Dynamics Enables Flexible Multi-Task Control | Alexandre Leon Mahrach IDIBAPS, Barcelona

[David Hansel]

[image: VVTNS.png]
https://www.wwtns.online
<https://streaklinks.com/A9c7PbbpKY7PxB6PaAJWGD3-/https%3A%2F%2Fwww.wwtns.online>
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on twitter: wwtns at TheoreticalWide

You are cordially invited to the lecture

Alexandre Leon Mahrach
IDIBAPS, Barcelona

on the topic of
Learning to Compose: Geometric Reorganization of Prefrontal Dynamics  Enables
Flexible Multi-Task Control

The lecture will be held on Zoom on June 10, 2026 at *11:00 am ET *

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> To receive the link: https://www.wwtns.online/register-page
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*Abstract: *Complex behavior requires neural circuits to compose elementary
operations—maintaining memories, evaluating sensory cues, suppressing
premature actions—into context-appropriate programs. How prefrontal
dynamics reorganize to support such composition when task demands compete
within a shared neural population remains unclear. Here, we developed a
dual-task paradigm in mice that combined a delayed paired-association (DPA)
task with an olfactory Go/No-Go (GNG) discrimination embedded in the delay
period. Mice learned the dual task rapidly, with early errors dominated by
false alarms on unpaired DPA trials. Interference was asymmetric: Go cues
disrupted performance more than No-Go cues, pinpointing premature action
rather than memory failure as the central learning bottleneck. Population
calcium imaging from medial prefrontal cortex (mPFC) showed that sample
identity, choice tendency, and test identity occupied near-orthogonal
subspaces of a shared low-dimensional manifold. As training progressed,
sample
representations remained stable while delay-period activity shifted away
from the action-associated region. To probe the underlying circuit
mechanisms, we trained low-rank recurrent neural networks on the same
paradigm. Networks developed a circular manifold on which memories were
stored as attractors at distinct angular positions, and test stimuli acted
as compositional rotation operators, routing stored memories to appropriate
actions. Dual-task training relocated mnemonic attractors to a position
that a reduced geometric model identified as Pareto-optimal—revealing a
fundamental tradeoff in which optimizing one task necessarily impairs the
other. Consistently, optogenetic inhibition of ACC→mPFC projections during
the delay displaced attractor geometry and selectively biased DPA versus
GNG accuracy, matching the reduced model's prediction. Together, our
results reveal how prefrontal circuits dynamically reshape attractor
geometry through learning-dependent attractor fine-tuning, providing a
mechanistic framework for how cortex resolves competing cognitive demands.

*About VVTNS : Launched as the World Wide  Theoretical Neuroscience Seminar
(WWTNS) in November 2020 and renamed in homage to Carl van Vreeswijk in
Memoriam (April 20, 2022), Speakers have the occasion to talk about
theoretical aspects of their work which cannot be discussed in a setting
where the majority of the audience consists of experimentalists. The
seminars, **held on Wednesdays at 11 am ET,**  are 45-50 min long followed
by a discussion. The talks are recorded with authorization of the speaker
and are available to everybody on our YouTube channel.*


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