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UBC Theses and Dissertations

Spatial and temporal details of spontaneous cortical activity provide insights into functions in the adult and developing brain McVea, David


While the body rests, the mind remains active. In fact, the brain exhibits a rich pattern of structured activity despite having few immediate sensory or motor tasks. During infancy, this brain activity appears tailored to assist in the maturation of neural systems. In the adult, it influences memory consolidation and maintenance of synaptic connections. In this thesis, I address these differences by using voltage-sensitive dye imaging to record spontaneous cortical activity in rodents during development and adulthood. In the adult, I examine slow-wave activity, a key form of spontaneous activity. I show that functionally related regions of the cortex activate synchronously, forming a core set of structures that underlie spontaneous activation. I also show that sensory connections shape the patterns of this activity. These effects hold true in the quietly awake mouse, to a lesser extent. These findings are consistent with an active role for slow-wave activity in the maintenance of cortical connections. In the infant, I examine a dominant form of brain activity, the spindle burst. This pattern of activity follows spontaneous sensory inputs generated by the developing sensory systems, including small twitches in the limbs and tail. It is generally thought to remain localized with the appropriate cortical sensory system, but using wide-field imaging, I show it spreads medially across the cortex. This suggests a potential role in the maturation of connections between sensory and motor regions. I explored this possibility more closely by recording activity in early life from the whisker system of the rat. In the adult, connections exist between the sensory and motor regions of the whisker system. To gain insight into whether the spontaneous activation of these systems contributed to their development, I compared the activity evoked by stimulation to the spontaneous activation of these systems. I found synchronized spontaneous activation of motor and sensory areas that were not yet functionally connected. This suggests that other structures synchronize these areas to promote the maturation of connections between them. Overall, this work reveals details about spontaneous activity that provide clues to why the brain devotes time and energy to activity disconnected from the outside world.

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