at Harvard Medical School

Benefactor Report

October 2025

The ability to navigate the world is essential to the well-being of most animals, including humans, and is one of the first cognitive functions disrupted in neurodegenerative disorders like Alzheimer’s disease. Today’s neurobiologists have a solid understanding of how the brain forms maps of the world and processes spatial relationships. However, they still know little about how the brain performs the more complex aspects of navigation, like making decisions about where to go or planning the best route to a destination.

With the generous support of a Moorhead Seed Grant, Christopher Harvey’s lab has developed a new paradigm to answer these questions. In this paradigm, mice navigate mazes toward reward sites containing desirable food, while experimenters introduce moment-by-moment changes to the maze—such as new walls, dead ends, and shortcuts—to test the mouse’s planning and decision-making abilities. Dr. Harvey’s team uses cutting-edge electrode technology to measure the function of thousands of brain cells across many regions of the brain while mice plan and make decisions. With the development of this new technology, they have discovered that two brain areas in particular play a critical role in navigation planning and decision-making: the posterior parietal cortex and the retrosplenial cortex.

Dr. Harvey is now investigating how the cells in these brain areas communicate to make plans and decisions, and how these brain areas interact with parts of the brain responsible for forming maps of the world, sensing visual landmarks, and executing locomotor movements. The team is well-positioned to understand how neurodegenerative diseases disrupt these brain circuits. They also aim to define the principles underlying natural intelligence and to understand how these principles can aid the development of better artificial intelligence. ​

Learned, cross-modal associations between visual and auditory stimuli dictate human perception. The McGurk effect, for example, shows that what one sees overrides what one hears: the mouth movements a person observes when looking at another person’s face as they speak influence what the observer hears, particularly if they can see the speaker more clearly than they can hear them. The neural circuit mechanisms responsible for such cross-modal interactions remain poorly understood, even though disruptions to these mechanisms can have devastating consequences for perception and drive mental disorders. Neurobiologists have established that the retrosplenial cortex, which connects reciprocally with the visual and auditory cortices, is essential for forming associations between visual and auditory stimuli and is necessary for memory formation and retrieval. Aleena Garner’s investigates the function of retrosplenial cortex feedback to the auditory cortex during visual–auditory associative learning.

The mammalian cortex generates substantial, non-random neural activity that arises independently from sensory inputs, and such activity can influence sensory processing. Dr. Garner aims to understand specifically how this activity regulates processing and sensory perception. Evidence from humans and other organisms suggests that a substantial portion of this internally generated activity corresponds to experience and memory activation. Dr. Garner’s team will examine how different types of memories regulate sensory processing, expanding their studies from associations with multisensory objects to  associations with specific spatial locations. Their work seeks to unveil how disruptions in cortical computations lead to disruptions in normal perception and to multisensory processing disorders. ​