Date: March 3rd at 12pm

In-Person Location: Singleton Auditorium 46-3002

Title: Elucidating laminar motifs of aperiodic and oscillatory activity in humans and mice

Abstract: The neocortex is the “crowning jewel” of mammalian evolution, enabling complex thought and higher cognitive processes. Across species and areas, it’s composed of six cortical layers with distinct cell types and connectivity. Despite this highly stereotyped anatomical motif, we do not know how the cortex organizes its activity. One potential mechanism is aperiodic processing, utilizing characteristic time constants to integrate information across different temporal scales. Another are cortical rhythms, implicated in diverse functions such as attention or plasticity. Both are seen throughout the mammalian neocortex. How these characteristic features of cortical processing vary across the cortical depth is largely unknown. This thesis will elucidate physiological motifs of aperiodic spectral slope and 3-5Hz cortical rhythms using laminar recordings in humans and mice. First, we characterize conserved features of aperiodic activity as captured by 1/f power scaling of the local field potential across cortical layers and species. We find that the timescale and magnitude of aperiodic activity decrease with cortical depth in humans, mice and macaques. These effects can be parsimoniously captured by a simple model derived from the time-constants and densities of prevalent postsynaptic receptors. This chapter was adapted from a preprint. Second, we investigate the physiology of a 3-5Hz rhythm which controls spiking throughout mouse neocortex. Despite being elicited by visual stimuli, 3-5Hz spiking is highly separable from sensory-evoked activity. Instead, the rhythm is driven by large (but not small) stimuli, and reflects highly synchronous cortical spiking led by layer 5. In thalamus, the oscillation is dominated by long-latency burst spiking. The rhythm is highly stereotyped across areas, and has key physiological similarities between V1 and M2. Then, I provide a proof-of-principle demonstration that the oscillation can be imaged at the single spine level across days using a novel glutamate sensor. Together, this work contributes to understanding laminar motifs of cortical processing across species and areas.

Zoom: https://mit.zoom.us/j/3052710804

Thesis Committee: : Professor, Mark Harnett, Professor Emery Brown, Professor Steve Flavell, and Pressor Ueli Rutishauser