Role of Experience in Visual System Plasticity
Focus:
Learning Goals and General Plan: These papers were chosen for an upper level Developmental Neuroscience or Neural Plasticity course that I teach. They represent a historical line of research that led to multiple paradigm shifts in how we view the role of experience in sensory system development. I am quite familiar with this research area, and it can be used to discuss a number of concepts in systems-level neuroscience (which is another class that I teach, to first year PhD students). The methods are not overly complex, and should be accessible to Neuroscience, Biology, and Psychology majors.
Overview:
Day One. Goal is to learn the steps of scientific method and how to use them in your own work.
Exercise: Pick an interesting science or health article from the lay press that describes a published scientific study. Read it at home. Look up and define any unfamiliar words, then bring it to class. You will need to briefly explain the paper to your group members. As a group, pick one of the papers and together outline the logic of the study.
Practice cartooning the methods of this paper.
Day Two. Goal is to learn how to read a real scientific paper. Exercise: Get the actual scientific paper and read it at home. Make a concept map of terms and processes.
In class make a cartoon of the methods with your group. Does your cartoon look a lot different from the one you made from the lay article? You may be asked to present your cartoon to the class.
In class, practice annotating one or two figures with your group. Be sure to connect the methods to the results presented in each figure. You may be asked to present your annotations to the class.
Compare and contrast the title and conclusions in the lay article to those in the journal article. Can you detect any “spin” in either case?
Day Three. Time to dive in! Begin analysis of Paper 1 using your new skills. Our goals will include not only understanding major concepts of sensory pathway organization and development, but also the process of science in general, the methodological approach used in this particular study, the results obtained, and the conclusions that can or cannot be drawn. In each case you will follow a step by step sequence as below:
Ongoing analysis of Paper 1and next 3 papers using same approach.
Step 1 is to concept map the introduction. What Big Question is being asked? What is the hypothesis being tested?
Step 2 is to cartoon the Methods section
Step 3 is to cartoon Methods and Results for each individual figure using the template. What does the figure show? Are there any control groups? What alternative hypotheses do they control for? Given this data, what conclusions can be drawn? Do they support or refute the hypothesis?
Step 4, after going through all the figures, is to make a bullet point list that could be developed into a discussion section
Step 5 is to read and critique the actual Discussion, then review it in class.
Applicable for Courses:
Developmental Neuroscience or Neural PlasticityEducational Level:
Upper-levelRoadmap Objectives:
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- Article: LeVay S, Stryker MP, Shatz CJ. Ocular dominance columns and their development in layer IV of the cat's visual cortex: a quantitative study. J Comp Neurol. 1978 May 1;179(1):223-44.
- Content area/major concepts: Sensory pathways, visual pathways, brain development, critical periods, brain organization (labeled lines, topography, receptive fields), cortical organization, tract tracing, ethical animal use, histological preparation, light microscopy.
- Methods or technology used to obtain data: Discuss method (from http://psyc254.uconn.edu/lecture10/ ) Inject tritiated amino acid (like proline) into one eye. Amino acid travels trans-synaptically from retina to thalamus (LGN) to Primary visual cortex (V1). An alternative to tritiated amino acid is to just stain for metabolic activity with cytochrome oxidase to show V1 OD domains Post-humously remove V1 calcarine and flatten it. Cut away layers 1-3. (i.e. Layers I-III) to reveal layer 4 (layer IV) Examine the pattern of amino acid labeled OD stripes.
- How the CREATE strategy was used: Annotate and cartoon the figure Ocular Dominance Column Development in Primary Visual Cortex (V1) Introduce conflicting data: Monkeys are born with already intact OD columns! Rakic, P 1976 Prenatal genesis of connections subserving ocular dominance in the rhesus monkey. Nature 261(5560):467-71. (not necessary to read it) Question to ponder: How can it be that monkeys have columns at birth if visual experience is necessary to form them? Students generate testable hypotheses and experimental design. Then we explore how the same lab addressed the issue with a new idea.
- Biggest teaching challenge:
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- Article: Wong RO, Meister M, Shatz CJ. Transient period of correlated bursting activity during development of the mammalian retina. Neuron. 1993 Nov;11(5):923-38.
- Content area/major concepts: Ion channels, synaptic transmission, action potentials, role of calcium, gap junctions, neurotransmitters and their receptors, explant cultures, electrophysiological methods.
- Methods or technology used to obtain data:
- How the CREATE strategy was used: Ask students to try to develop possible hypotheses from the pondering question before reading. Historically the thinking was maybe the retina can instruct monkey OD columns in utero? Introduce conflicting data: But removing the eyes does not affect development of ocular dominance columns! Again students develop alternative hypotheses and experimental design. Ponder why, if ODC are formed w/o vision. Levay saw what they did? Turns out there may have been a methodological problem of proline leakage across LGN layers.
- Biggest teaching challenge:
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- Article: Crowley JC and Katz LC. Development of ocular dominance columns in the absence of retinal input. Nature Neuroscience, 2(12):1125-1130, 1999.
- Content area/major concepts: Not much additional content.
- Methods or technology used to obtain data:
- How the CREATE strategy was used:
- Biggest teaching challenge: