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Differentiating Signals Recorded from Rat Brain in Response to Different Olfactory Stimuli

Arman Mehr, Matin | 2025

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 57853 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Karbalaei Aghajan, Hamid
  7. Abstract:
  8. The olfactory sense in rats provides crucial information for identifying food sources, detecting threats, and facilitating social interactions. The olfactory bulb is one of the key brain regions involved in the initial processing of olfactory information and its transmission to higher brain areas for more complex processing. However, more advanced cognitive processes such as evaluation and decision-making rely on interactions between other brain regions. Among these, the striatum, as a part of the basal ganglia, plays a role in reward evaluation, reward-based learning, and shaping behaviors associated with sensory stimuli. This region contributes to learning, decision-making, and action formation through its connections with cortical areas and other brain regions by integrating sensory and cognitive information. Specifically, the dorsal striatum is critical for controlling motor behaviors, coordinating sensorimotor information, and modulating goal-directed and habit-based behaviors. Despite extensive neuroscience research on the functioning of the olfactory system, many aspects of olfactory information encoding and processing, particularly the interaction of olfactory regions with cognitive and dopaminergic brain areas and their roles in decision-making and behavior, remain unclear. Moreover, the role of the dorsal striatum in processing olfactory information and its influence on decision-making and stimulus-evoked behaviors is among the topics that have been less studied. This research aims to address these gaps. By recording local field potentials from the brains of rats, this study investigates the role of the dorsal striatum and its interactions with the medial prefrontal cortex and hippocampus in response to two olfactory stimuli: lemon (a neutral odor) and peanut butter (an appetitive odor). The methods for analyzing brain data include calculating the instantaneous theta-band power and assessing functional and effective connectivity using measures such as transfer entropy and phase-amplitude coupling to identify temporal changes in functional connectivity among these regions. The results show that sniffing peanut butter odor increases theta-band oscillations in the dorsal striatum and medial prefrontal cortex. Additionally, transfer entropy from the dorsal striatum to the prefrontal cortex in response to this odor increased compared to lemon, and phase-amplitude coupling between the amplitude of the dorsal striatum and the phase of other regions was also increased in response to peanut odor. These findings, along with increase of behavioral activity in rats exposed to the appetitive odor, highlight the role of the olfactory sense in driving exploratory and reward-related behaviors
  9. Keywords:
  10. Phase-Amplitude Coupling (PAC) ; Multivariate Transfer Entropy ; Medial Prefrontal Cortex ; Theta Oscillations ; Dorsal Striatum

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