Neural mechanisms for task structure abstraction and decision-making strategies in mouse frontal cortex

Hosted by Mostafa Nashaat

External speaker

Mohamady El-Gaby, PhD

Position: MRC Brain Network Dynamics Unit at the University of Oxford

Title: Cellular Basis for Mapping Behavioural Structure

To flexibly adapt to new situations, our brains must understand the regularities in the world, but also in our own patterns of behaviour. A wealth of findings is beginning to reveal the algorithms we use to map the outside world. In contrast, the biological algorithms that map the complex structured behaviours we compose to reach our goals remain enigmatic. Here we reveal a neuronal implementation of an algorithm for mapping abstract behavioural structure and transferring it to new scenarios. We trained mice on many tasks which shared a common structure organising a sequence of goals, but differed in the specific goal locations. Animals discovered the underlying task structure, enabling zero-shot inferences on the first trial of new tasks. The activity of most neurons in the medial Frontal cortex tiled progress-to-goal, akin to how place cells map physical space. These “goal-progress cells” generalised, stretching and compressing their tiling to accommodate different goal distances. In contrast, progress along the overall sequence of goals was not encoded explicitly. Instead a subset of goal-progress cells was further tuned such that individual neurons fired with a fixed task-lag from a particular behavioural step. Together, these cells acted as task structured memory buffers (SMBs), implementing an algorithm that instantaneously encoded the entire sequence of future behavioural steps, and whose dynamics automatically computed the appropriate action at each step. These dynamics mirrored the abstract task structure both on-task and during offline sleep. Our findings suggest that schemata mapping complex behavioural structures can be generated by sculpting progress-to-goal tuning into task-structured buffers of individual behavioural steps.

Local Berlin speaker

Mostafa Nashaat, PhD

Position: Larkum Lab, HU Berlin

Title: The Neural Mechanisms of Fast vs Slow Decision Making

Not all decisions are created equal; factors such as the difficulties or associated costs affect the time spent to make decisions. This is variously interpreted as speed/accuracy, fast/slow, or impulsivity/deliberateness tradeoffs according to different models of behaviour Regardless, it is generally assumed that decision latency reflects the neural mechanisms underlying behavioural strategy and cognitive investment. However, such investigations have been difficult in mice which are consistently impulsive. Here, we show that manipulating cost, using a novel floating-platform paradigm, overcomes the natural impulsivity of mice, more closely matching human behaviour. Furthermore, this approach allowed us simultaneously to measure the flow of activity from medial to lateral frontal cortex (MFC→LFC) and record sequences of single neuron activity with 2-photon imaging. Surprisingly, MFC display a different mode of operation, with high vulnerability to optical inhibition compared to LFC. Furthermore, the balance in choice coding at the beginning of sequences in MFC correlated with trial history and behavioural strategy. We found that for optimal performance, slow sequences in MFC showed declining numbers of active neurons whereas the opposite was true in LFC. Our results suggest that while LFC acts as an integrative motor threshold, MFC plays a larger cognitive role in the selection and timing of decisions than previously thought. Our study offers a methodological and mechanistic framework in mouse frontal cortex to understand the neural basis of voluntary decision making.

 

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This event is part of the PostDoc Network Speaker Series.

Guests are welcome!