Thesis defense Irene Onorato (Donders Series 629)

21 November 2023

Promotors: Prof. Dr. Martin Vinck and Prof. Dr. Francesco Battaglia 

Interaction between excitatory and inhibitory neuronal types in controlling cortical dynamics: An investigation in the early visual cortex of monkeys and mice

Local field potential (LFP) oscillations in the gamma-frequency band (30-90 Hz) are a spectral signature of the primary visual cortex (V1) , linked to high cognitive functions like attention and sensory processing. Although these oscillations are thought to emerge from the interactions between excitatory and inhibitory neurons, the distinct contributions of different neuronal types remain unclear. Hence, in my thesis I investigated the circuit mechanism underlying the generation of these oscillations in monkeys and mice V1. The analysis of spiking and LFP activity recorded from monkeys V1 revealed a sub-type of excitatory neuron with peculiar electrophysiological properties that may play a pivotal role in pace-making the network at gamma frequency and in encoding the stimulus information. To further unravel the role of interneuronal sub-types in the circuit mechanism of gamma generation I combined extracellular recordings with optogenetics to record from identified parvalbumin (PV)-expressing and somatostatin (Sst)-expressing interneurons in awake mice V1. With this approach I observed that PV interneurons constitute the primary source of rhythmic inhibition at gamma frequency to excitatory neurons. I also identified a specific temporal relationship between the activation of PV, Sst and excitatory neurons within each gamma cycle, suggesting that gamma oscillation may be the result of coordinated activity among these neuronal types. Overall, my thesis work provides insights into the specific roles of distinct excitatory and inhibitory neuronal populations in generating gamma oscillations in macaque and mouse V1.