University of Sussex
Bitzidou, Malamati.pdf (29.43 MB)

Neural activity underlying whisker-mediated sequence discrimination

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posted on 2023-06-09, 19:06 authored by Malamati Bitzidou
In the world around us natural stimuli unfold over time and their temporal patterning is key to making sense of them. When we hear a piece of music or passage of speech or scan a texture with our fingertip, physical features in the stimulus are concatenated in a particular order, and this defines a sequence, reflected in patterns of spiking evoked in sensory receptors. To allow sequence recognition, these spike patterns must be integrated and decoded at later stages of processing. How neuronal activity in vivo distinguishes between behaviourally relevant sensory sequences remains unknown. This thesis sought to increase our understanding of how sequences are processed by neuronal populations. To address this question, I first aimed to determine the capacity of mice to recognise ordered sequences of stimuli, by training them on different variants of a whisker-based sequence discrimination task. In these experiments, mice distinguish between “words” constructed from distinct whisker vibrotactile stimuli assembled in different orders and have to respond to one of them. Animals sometimes respond to the earliest cues allowing sequence discrimination, but improve their performance when deliberating for longer. Next, I sought to track the route of sensory information through the cortex during sequence recognition by suppressing neuronal activity in different cortical regions. To investigate this, I optogenetically activated inhibitory neuronal populations expressing channelrhodopsin in VGAT mice. Inactivating primary somatosensory “barrel” cortex (S1BC) and secondary somatosensory cortex (S2) abolished responses to sequence stimuli on interspersed light-on trials, but this effect was not specific to the target sequence. Thus, recognition of sequences occurs in brain areas downstream of S1BC. Finally, I aimed to identify the neuronal responses involved in processing the sequence by performing electrophysiology recordings of S1BC and posterior parietal cortex (PPC) during the behavioural task. These experiments led to a database of recordings that will be analysed as a continuation of my PhD research.


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University of Sussex

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