This seminar introduced a breadth of topics moving from cognition and consciousness to global workspace theory, cerebral networks, self organized criticality and scale free systems... and narrowed down to how the microstates approach to EEG analysis seems to provide evidence for the brain's function as a scale free phenomenon.
Ajay Kumar Nair (2nd year PhD scholar) presented his seminar on "Microstates - the atoms of thought? Studies in EEG, fMRI... A Conceptual Overview".
This seminar introduced a breadth of topics moving from cognition and consciousness to global workspace theory, cerebral networks, self organized criticality and scale free systems... and narrowed down to how the microstates approach to EEG analysis seems to provide evidence for the brain's function as a scale free phenomenon. Ajay Kumar (2nd year PhD Scholar) presented the progress of his PhD study on Well-being in Rajayoga practitioners.
Anshu Kumari (2nd year PhD Scolar) presented her seminar titled "Plasticity in Amygdala and Anxiety".
She gave a clear introduction to Anxiety disorders in terms of a psychiatric disorder as well as its neurobiology. From human studies to molecular mechanisms, the evidences seemed to show that anxiety is associated with an over active Amygdala which possibly have a detrimental effect on the hippocampus mediated cognitive network. Some of the interesting thoughts during the seminar were: 1) As anxiety prone individuals show increased Amygdala activity during presentation of happy as well as fearful images, Amygdala should not only be related to anxiety but stress response as a whole. 2) Do Amygdala on both sides act differently during anxiety. 3) Pre-exposure to mild stressors or exogenous cortisone could be benificial during a subsequent exposure. 4) Does BDNF get differentially elevated in different brain regions in response to stress? Please share your comments Dr. Shwetha Shankar (Wake Forest School of Medicine) presented her work on "Time course of a Perceptual Judgement and Factors affecting it" .
While, Reaction time (RT) studies have been in vogue for a long time, Donders was the first to try and get to extract processing time (time taken to identify the target) in the 1880s. The subtraction approach however has a number of limitations - there are multiple covert factors at play, high variability and speed-accuracy trade-offs that take place. Also visual stimuli tend to leave a after-image so the timing is unpredictable. To counter this people have tried using mask images but that introduces other confounds. Shwetha's group used a compelled-saccade task with a variable gap time between go and cue images to arrive at processing time (reaction time - gap time). They also created a Tachometric curve (with centre point, slope/rise time and maximum height) that graphed %correct responses as a function of processing time. This approach yields much more information than reaction time or psychometric curve (%correct vs gap time) studies. They manipulated three factors (motivation; stimulus discrimination and features; perceptual learning) that affect perception to see how the tachometric curve responds. Areas that need further work include effect of expectation, multisensory decision making and neural correlates of perceptual changes (areas and mechanisms). Shilpa BM (3rd year PhD Scholar) presented her seminar of "Enriched Environment and recovery of Brain functions".
A number of studies suggest that enriched environments ameliorate the effects of traumatic brain injury; neurodevelopment and ageing; neurodegenerative diseases such as Alzheimers and Huntington's; depression, fear and stress; addictions; epilepsy... and seem to function via increase of cognitive reserve. Benefits include increase in synaptic density, neurotrophic support, glial proliferation, neurogenesis, vasculature support. Several studies have been done in our labs (Subicular lesion studies by Anandh and Bindu B; Restraint stress by Ramkumar and Veena; Fear conditioning by Preethi; Depression by Mahati and now on Epilepsy as well). Dr Arun Sasidharan (3rd Year PhD Scholar) presented his seminar on Schizophrenia - what EEG and fMRI can tell us?
In this detailed and well spelt-out seminar, Arun started off with reviewing current research on Schizophrenia and the findings from EEG and fMRI studies in the field. He then described the classical view of Schizophrenia and then went for a deep dive into understanding how EEG, ERP, source localization and fMRI approaches work, the potential pitfalls to watchout for and the benefits of each approach in order to be able to interpret the results better. Dr Rukmani (1st year MPhil Scholar) presented her seminar on "Role of Thyroid Hormones on Brain Development".
Hypothyroidism is considered to be the most common cause of mental retardation. Thyroid appears to mature by 12th week post conception. Iodine is used in synthesis of thyroid hormones and is a dietary requirement. Iodine deficiency during the first (and to some extent the second) trimester has serious consequences. Most of T4 (thyroxine) is synthesized by thyroid and some T3 (triiodothyronine) as well. T4 and T3 crosses Blood Brain Barrier in Adults. In the developing brain, T4 passes more easily than T3 into the brain tissue. An increase in circulating T3 doesn't increase cerebral T3 in the developing brain. What gives these hormones much power is that they are able to delay gene transcription even though they don't stop it. For example, the Reelin gene that is necessary for ordered migration of developing cells across the cortical layers is regulated by thyroid hormones. In a normal cortex, the oldest neurons are in layer 6 while the newer ones traverse past to go to the layers above. In the Reeler cortex, the newest neurons fail to traverse older neurons in the lower layers and reach Layer II/III/IV/V. Interestingly, hypothyroidism is correlated with lesser myelination when the axonal diameters are less than a critical diameter. Thyroid seems to affect neuronal migration, proliferation, the laminar effect, synaptogenesis, neuritogenesis... regulates bdnf and nt3. Rukmani brought up an important point to note about comparing rodent and human studies. The rat model is very good for studying brain development as the sequence of events between rat and humans is similar, proportionate and comparable when we take onset of fetal thyroid action as a reference point. However, when we take birth as a reference point, we need to take into account that postnatal rat brain development is relatively more than human brain development. Dr Aparna Sharma (Research Associate) presented her concept seminar on "Are organotypic 3D cell culture models more suitable for the study of neuro degenerative diseases?"
Aparna started with an overview of the historical development of cell culture models. Tissue Cultures in Petri Dishes (in 2D layers) was started off by Wilhelm Roux in 1885. The field has moved onto organotypic slice models where tissue slices were grown and more recently onto 3D cultures where 3D scaffolds (10-30 micrometers) are provided for the cells to grow. Aparna cited a number of studies where 3D culture models with different types of scaffolds have been compared with the traditional 2D cell culture approaches. The 3D culture approach seems to be better for a number of reasons:
A number of 3D scaffolds are now commercially available - ranging from the natural Aragonite (bio-active, derived from the highly porous coral exoskeleton, made up of Calcium Carbonate and functions as a calcium supplement), Hydrogel (synthetic and used for neuronal cells), Human ECM (contains collagens, laminins etc) and PuraMatrix (considered to be self-assembling). Given the number and range of benefits accrued, Aparna concluded that organotypic 3D cell culture models are valuable for the study of neurodegenerative diseases. Poojashri Mishra (2nd year PhD scholar) presented her seminar on "Neuroinflammation".
Poojashri's started by focusing on the question if the CNS can be considered "immune privileged". She started with reviewing the early works in the field such as Shirai (1921) on rat sarcoma in heterogenous animals (these cells survived in the brain but were rejected in other areas) and by Medawar. She considered four aspects that might lend credence to immune priviledged position of the CNS:
She then reviewed the evidence of neuroinflammation and its molecular basis. In particular she explored the role of microglia (the "immune sensor") activation in phagocytosis, chemotaxis, morphological changes, cytotoxic changes etc. Neurons are also known to influence immune function by secretion of various CD class agents. Our own lab's work (Shobha etal 2010) has studied inflammatory response in ALS - reactive astrogliosis (increased NO synthase and S100Beta activity). Finally Poojashri considered the evidence for neuroprotective effects of neuroinflammation (for example detrimental effects in ALS could be helpful in MS or Parkinsonism). During the open discussion, NF-kB and its role in cellular homeostasis was discussed. Merlin PB (1st year MPhil Scholar) presented her first seminar on the "Structure and Function of Ion Channels".
Merlin discussed about the conductivity, selectivity and gating mechanisms of Ion channels, various types of ion channels based on function, different channel protein families related by structural similarity, channel agonists and antagonists and the developmental changes in ion channel properties. |
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August 2019
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