Princeton University Library Catalog
- Nikolic, Milos [Browse]
- Senior thesis
- Shaevitz, Joshua W. [Browse]
- Leifer, Andrew M. [Browse]
- Princeton University. Department of Physics [Browse]
- Class year:
- 45 pages
- Summary note:
- This thesis looks at the relationship between the neural activity and the behavior
of a freely moving roundworm Caenorhabditis elegans. We optically activate two
mechanosensory neurons in vivo and use advanced image and statistical analysis to
quantify the behavior, and consequently the behavioral changes that arise due to the
perturbation of the neurvous system. We outline the procedure to measure and identify
behaviors in a lower dimensional space, which allows us to explain the consequences of
the activity of specific neurons, and to potentially use this analysis to further investigate
functional structure of the animal nervous system.
Despite technological advances, the ways in which animal brains function remain
elusive due to the complexity of most animal nervous systems. The structure of most
brains is also rarely well known. Our model organism has one of the best researched
nervous systems in the animal kingdom. C. elegans is a transparent nematode whose
brain structure has been studied in detail  and all of its 302 neurons and their
connections have been identified. Yet, we still have only a limited knowledge of the
neural dynamics and functions that specific neurons perform.
One of the most interesting scientific questions today is how does the brain activity
correlate with the behavior. Many experiments have been done in this field, like that
of Sawin , but so far they have relied on subjective categorizations of behavior. We
employ dimensionality reduction by Principal Component Analysis to objectively and
mathematically categorize the most important components of animal behavior robustly
[23, 25, 26, 27].
We find that the laser stimulation of the OLQ and CEP neuron alters the values
of behavioral components we measure in a complex way, illustrating a non-trivial relationship
between the activity of these two neurons and the motor activity of C. elegans.
Moreover, we identify the behavior that the optogenetic stimulation of CEP neuron
causes. Our ability to reconstruct the exact behavioral response thus draws a strong
quantitative connection between the brain activity and behavior of C. elegans.