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Analysis and Comparison of the Role of SNr and vlPFC in Value Learning and Memory and Value Guided Saccade

Kheirkhah Ravandi, Mohammad Ali | 2022

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 55376 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Ghazizadeh, Ali
  7. Abstract:
  8. Learning the value of the objects in the living environment of animals has a great significance in guiding the behavior of animals. Therefore, understanding the mechanisms and structures involved in this phenomenon in the brain is one of the topics of interest in modern neuroscience. One of the most important structures known in the mammalian brain that plays an important role in learning the value of objects is the Basal ganglia. The value signal of objects has been observed in different areas of this structure. Another important area of the brain, whose role in learning the value of objects has recently been investigated, is the area of the Ventrolateral Prefrontal Cortex (vlPFC). On the other hand, from the knowledge of monkey brain anatomy, we know that these two structures are placed in a loop so that the activity of each affects the other. But the existential function of this ring and the role of each of the areas involved in it are still unknown. In this research, we have used two monkeys that were trained to perform a value learning task. During the experiment, single-unit extracellular recordings of these regions were made while monkeys were learning value of objects. We have divided objects into two categories, good and bad. Good objects correspond to high rewards and bad objects correspond to low rewards. We show that although we did not differentiate between the objects within the same category, the monkeys implicitly assigned different values to different objects within the same category. For example, some good objects were more valuable than other good objects for monkeys. We show that the Ventrolateral Prefrontal Cortex does not distinguish between value of objects within each category, but the Substantia Nigra Reticulata (SNr) region in the Basal ganglia encodes the difference in implicit value of objects within the same category. Furthermore, we show that value learning in vlPFC saturates after a few trials, while continues in SNr monotonically, resembling explicit and implicit learning respectively. Thus, the vlPFC is related to learning categorical value of objects or explicit learning, and SNr is involved in learning the implicit value of objects.

  9. Keywords:
  10. Reward Training ; Object Value Categization ; Explicit Value ; Implicit Value ; Substantia Nigra Reticulata (SNr) ; Ventrolateral Prefrontal Cortex (vlPFC)

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