| Summary: | Sensory experience at different stages during development can alter structures and
functions of the nervous system in different ways suggesting that the timing of the
occurring experience is critical. In these studies, I used the nematode Caenorhabditis
elegans as a model organism to demonstrate the effects of deprivation of mechanosensory
experience on behaviour and development; I identified critical and sensitive periods for
reversing the detrimental effects of deprivation by introducing mechanosensory
experience during development. Earlier studies found that worms reared in isolation,
without the mechanosensory stimulation from conspecifics, respond significantly less to a
mechanical tap stimulus and are significantly shorter in body length than worms raised in
age-matched colonies. An examination of elements of the synapse between the
mechanosensory neurons and the command interneurons showed that in isolate-raised
worms, this synapse was weaker (fewer post-synaptic glutamate receptors and fewer pre
synaptic vesicles) than the synapses of worms raised in a colony condition. In this thesis,
brief mechanical stimulation at any time during development reversed the effects of
isolation on the behavioral response to tap and glutamate receptor expression suggesting
there is no critical period for these two measures. In addition low levels of stimulation
early in development (at the beginning of larval stage LI), but not later, rescued presynaptic
vesicular marker pmec-7::SNB-1::GFP vesicle expression suggesting there is a
period during which brief mechanosensory stimulation can reverse the effects of isolation
very easily. Larger amounts of mechanosensory stimulation resulting from rearing worms
in isolation and transferring them to a colony at the start of LI, L2 or L3 rescued the
effects of isolation on body growth suggesting there is a critical period to reverse the
effects of isolation on worm length that ends during L 3 . These results suggest that
development of different systems follow different rules/time courses. Rescuing one
aspect of development will not necessarily reverse the total effects of isolation on the
developing organism. Different aspects of development will require varying amounts of
stimuli at varying time points in development, which would all need to be taken into
account to fully rescue the effects of deprivation on the organism. === Arts, Faculty of === Psychology, Department of === Graduate
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