Research Overview

Neuronal mechanisms underlying the generation, maintenance, monitoring, and transformation of mental representations in working memory

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Our brain has the extraordinary ability to actively maintain and manipulate mental representations of sensory or abstract/conceptual nature. This ability is known as working memory. The mental image of a person we just met, or an address we are driving to, or today’s to-do list, or the sentence we are constructing to say next—they can all be maintained in working memory, even without the use of our senses. Representations in working memory can be manipulated by transforming them (e.g., mentally performing a mathematical calculation) or monitoring them (e.g., mentally going over a to-do list), among others. Our ability to manipulate representations—not to simply maintain or store them—is what makes working memory fundamental for other cognitive abilities such as attention, problem-solving, decision-making and action-planning, and is the core of human intelligence, imagination, and creativity.

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​One of the central research aims of the Mendoza-Halliday Lab is to understand the mechanisms underlying the manipulation (transformation and monitoring) of working memory representations at the level of single neurons, microcircuits, and neuronal populations across multiple brain regions. We also aim to understand the relationship between the mechanisms of working memory maintenance and manipulation, as well as how working memory mechanisms interact with and support other brain functions such as perception, attention, decision-making, and action-planning, among others.

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​To examine these mechanisms, we simultaneously monitor the activity of large numbers of individual neurons across cortical layers and across multiple brain regions using high-density laminar electrophysiological methods during the performance of complex visual cognitive tasks requiring the maintenance and manipulation (transformation or monitoring) of mental representations in working memory. This allows us to investigate how electrophysiological activity in different neurons, neuron types, cortical layers, and brain regions, as well as their communication, relates to these cognitive functions. To examine the causal role that neurons in different brain regions play in working memory maintenance and manipulation, we experimentally inactivate or activate these neurons using customized large-scale optogenetic methods we developed.