Research
Background
Our brain experiences innumerable auditory experiences from the surrounding environment , but it is not possible for the brain to process all of them. Sounds that are repeating in nature gets adapted with time while the response to those that occurs will less probability or are unexpected remain unchanged . Stimulus specific adaptation (SSA) refers to reduction in responsiveness of a neuron to a common or repetitive stimulus while the neuron remains highly sensitive to rare sounds . SSA could result simply from the depression of the responses to the standard. Alternatively, there may be an increase in the responses to the deviant stimulus due to the violation of expectations set by the standard, indicating the presence of true deviance detection. A macrolevel manifestation of deviant sensitivity is mismatch negativity (MMN) which can be detected through EEG. Our natural environment is oddball in nature where such deviant or important stimuli occurs with less probability .The ability to flexibly adapt to the dynamically changing environment in a goal-directed manner and to shape our neural circuits during development based on experience is fundamental to our survival and smooth functioning.
A particular period in development, during the formation of cortical circuitry have been termed as critical period given the immense capability of adaptation or plasticity during these developmental windows. The critical period is a time during early postnatal life when the development and maturation of structural and functional properties of the brain, its 'plasticity', is strongly dependent on sensory experience resulting in irreversible changes that persists till adulthood. Talking about auditory cortical development the known critical period lies between p12 - p16 after ear canal opening (ECO). But evidence shows the presence of a similar developmental epoch before ECO as well where subplate neurons (SPN) play an important role in shaping the neural circuits. They are the earliest born cortical neurons that respond to sound, are largely transient in nature and are shown to be deviance detectors. They play an extremely crucial role in scaffolding thalamocortical transfer of axonal afferents. Further, SPNs are also vulnerable to specific damage during birth from hypoxia and have been implicated in multiple disorders like autism spectrum disorders, epilepsy, and schizophrenia . Exposure to oddball stimulus before ECO manifests itself as change in the strength of response to deviant sounds at adulthood. Thus SPN selectively guide auditory cortical development based on deviant low probability or relatively novel sounds in the auditory environment.
Broad Objective
My research seek to decipher if the presence of context is important for deviance detection .
Confirmation of SPN activity before and after ECO with immediate early gene cfos expression and also to confirm the plasticity related changes through behavioral analysis.
Characterizing cortical spontaneous activity changes in typically and altered developing mice .
Characterizing altered development by manipulating SPN cytoarchitecture and establish the behavioral significance of such early experiences.
Techniques
In- vivo extracellular electrophysiology , Immunohistochemistry, 2- photon calcium imaging , Behavioral analysis in mice