Abstract View

COMPARTMENTAL DIFFERENCES IN SPINE MOTILITY OF LAYER 5 NEURONS IN VISUAL CORTEX FOLLOWING BRIEF MONOCULAR DEPRIVATION. S.Oray*; A.Majewska; M.Sur Dept. of Brain & Cognitive Sci., MIT, Cambridge, MA, USA Dendritic spines receive the large majority of excitatory inputs in the mammalian cortex and changes in spine dynamics appear to be correlated with the restructuring of synaptic connections. One system in which synaptic rearrangements are well-characterized is that of monocular deprivation in the visual cortex. Monocular lid suture during a plastic period of development causes a rapid electrophysiological shift of responses towards the open eye. Moreover, it has been suggested that these changes occur first in the superficial and deep layers of the cortex (layers 2/3, 5 and 6), followed by changes in thalamic-recipient layer 4. We have studied spine motility in this system following brief periods of monocular deprivation using transgenic mice expressing GFP in a subset of layer 5 pyramidal neurons. Using two-photon microscopy, spines were imaged in the binocular visual cortex in acute brain slices following short (2-3 day) monocular lid suture during the height of the critical period (starting at P26). We find that spine dynamics on layer 5 pyramidal neurons, quantified as a change in spine length per unit time, exhibit different motilities based on their laminar distribution. Spines representing putatively intracortical synapses, such as those on the distal parts of the apical dendrite (in layer 2/3), or near the soma on proximal dendrites (in layer 5), show increased motility in deprived cortex as compared to control spines at matching dendritic locations in nondeprived cortex. This is in contrast to spines in a middle region of the apical dendrite (in layer 4), which show no change in spine motility following brief monocular deprivation. These data are consistent with the hypothesis that rapid changes in synaptic efficacy following activity imbalance occur first at intracortical synapses, and are a precursor to changes in feedforward connections during critical period plasticity. Support Contributed By: Grants from the NIH (MS) and a Whiteman Fellowship (AM). Citation: S. Oray, A. Majewska, M. Sur. COMPARTMENTAL DIFFERENCES IN SPINE MOTILITY OF LAYER 5 NEURONS IN VISUAL CORTEX FOLLOWING BRIEF MONOCULAR DEPRIVATION. Program No. 266.8. 2003 Abstract Viewer/Itinerary Planner. Washington, DC: Society for Neuroscience, 2003. Online.