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VISUAL CORTICAL PLASTICITYOCULAR DOMINANCE AND OTHER VARIETIES
REVIEW OF HIPPOCAMPAL LTP
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“…when an axon of cell A is near enough to excite a cell B and repeatedly and consistently takes part in firing it, some growth or metabolic change takes place… such that A’s efficiency, as one of the cells firing B, is increased.”
-Donald Hebb, 1949
i.e., Fire together, Wire togetherUse it or lose it
ACTIVITY-DEPENDENT SYNAPTIC PLASTICITY
Input Layer
Target
Competition or Cooperation?
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PROPERTIES OF LTP IN CA1
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Whitlock et al. show mimicry and occlusion
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OCULAR DOMINANCE PLASTICITYCRITICAL PERIOD REGULATION OF PLASTICITY
VISUAL PATHWAYSVISUAL PATHWAYS
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Visual map refinement:Neighboring neurons in the retinotopic map
fire together and wire together
Retina SC Retina SC
BINOCULAR VISION
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OCULAR DOMINANCE COLUMN ASSAYS
Development of Ocular Dominance Columns-Anatomy
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Development of Ocular Dominance Columns-Physiology
from Sanes et al. 2005
ACTIVITY-DEPENDENCE
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SPONTANEOUS RETINAL ACTIVITY
3-eyed frogs: induction of OD columns
from Constantine-Paton et al. 1978
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REPRESENTATION OF HEBB'S POSTULATE AS IT MIGHT OPERATE DURING DEVELOPMENT OF THE VISUAL SYSTEM
EFFECTS OF MONOCULAR DEPRIVATION ON OD COLUMNS
OCULAR DOMINANCE PLASTICITY
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Binocular deprivation has a minor effect-Evidence for interocular competition
from Sanes et al. 2005
Strabismus prevents binocularity-Interocular coordination is necessary
from Sanes et al. 2005
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OCULAR DOMINANCE PLASTICITY EXHIBITS A CRITICAL PERIOD
from Purves et al. 2004
CRITICAL PERIOD FOR OD PLASTICITY
Juvenile
Adult
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Common forms of synaptic plasticity in slices of adult rat hippocampus (A) and adult rat visual cortex (B).
Bear M PNAS 1996;93:13453-13459
MECHANISM:LTP/LTD?
BCM Sliding Threshold Model
Bear M PNAS 1996;93:13453-13459
©1996 by National Academy of Sciences
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HEBBIAN PLASTICITY IN V1
Kirkwood A, Bear MF. Hebbian synapses in visual cortex. J Neurosci. 1994
Kirkwood A1, Lee HK, Bear MF. Co-regulation of long-term potentiation and experience-dependent synaptic plasticity in visual cortex by age and experience.Nature. 1995
SUPPORTING EVIDENCE
• NMDAR-dependence
• 2B 2A
• Occlusion
• Critical period timing matches
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LTP/LTD in Sensory Cortex Exhibits a Critical Period
from Sanes et al. 2005
LTP in Visual Cortex is Disrupted by NMDAR Blockade
Hensch TK et al. J Neurosci 1998
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DO NMDA RECEPTORS HAVE A CRITICAL FUNCTION IN VISUAL CORTICAL PLASTICITY?“…THE OPERATION OF NMDA RECEPTORS IS DIFFERENT IN THE INTACT ANIMAL THAN IN VITRO. FOR EXAMPLE, NMDA RECEPTORS ARE ACTIVATED AT LOW LEVELS OF SENSORY INPUT IN INTACT ANIMALS BUT ONLY BY HIGH LEVELS OF INPUT IN SLICE PREPARATIONS. RECENT RESULTS SUGGEST THAT A RE-EVALUATION OF THE ROLE OF NMDA RECEPTORS IN NEOCORTICAL PLASTICITY IS REQUIRED.”
FOX K, DAW NW. TRENDS NEUROSCI. 1993
WHAT CAUSES THE CRITICAL PERIOD TO OPEN AND CLOSE?HOW COULD ADULT PLASTICITY BE PROMOTED?
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CRITICAL PERIODS AND GABA
GABA-AR function is necessary
CRITICAL PERIODS AND GABAToyoizumi T1, Miyamoto H, Yazaki-Sugiyama Y, Atapour N, Hensch TK, Miller KD.A theory of the transition to critical period plasticity: inhibition selectively suppresses spontaneous activity. Neuron 2013
What causes critical periods (CPs) to open? For the best-studied case, ocular dominance plasticity in primary visual cortex in response to monocular deprivation (MD), the maturation of inhibition is necessary and sufficient. How does inhibition open the CP? We present a theory: the transition from pre-CP to CP plasticity arises because inhibition preferentially suppresses responses to spontaneous relative to visually driven input activity, switching learning cues from internal to external sources. This differs from previous proposals in (1) arguing that the CP can open without changes in plasticity mechanisms when activity patterns become more sensitive to sensory experience through circuit development, and (2) explaining not simply a transition from no plasticity to plasticity, but a change in outcome of MD-induced plasticity from pre-CP to CP. More broadly, hierarchical organization of sensory-motor pathways may develop through a cascade of CPs induced as circuit maturation progresses from "lower" to "higher" cortical areas.
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PARVALBUMIN+ GABA+ BASKET NEURONS
Figure 1 Bistable Network Configurations of PV-Expressing Neurons in Brain Plasticity (A) Network configurations favoring plasticity. (B) Network configurations favoring stability
Takao K. Hensch TK Cell 2014
Bistable Parvalbumin Circuits Pivotal for Brain Plasticity
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Selective Rearing Biases Response Properties
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PLASTICITY IN THE AUDITORY PATHWAY
Selective rearing experiments in the auditory system
from Sanes et al. 2005
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Barn Owls – model system to study mechanisms of sound localization and neural plasticity in the midbrain.
Barn Owl – The Silent Hunter
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Barn owl sound localization assay
Azimuth - ITD; Elevation - IID
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Barn owl
Azimuth - ITD; Elevation - IID
Barn owl – space map in ICx
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Barn owl sound localization: Parallel pathways for IID and ITD
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Juvenile Plasticity-Behavior
Juvenile Plasticity-Electrophysiology
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Juvenile Plasticity-Anatomy
Instructive Signals to ICx from ICc, Tectum
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Physiological traces of learningin prism-reared adults
Effect of age and prior experience on ITD map plasticity
“Sensitive period”
ANATOMICAL TRACES OF LEARNINGIN PRISM-REARED ADULTS
Linkenhoker BA, von der Ohe CG, Knudsen EI.Anatomical traces of juvenile learning in the auditory system of adult barn owls.
Nat Neurosci. 2005
Prism-induced shift Retrograde tracer Anterograde tracer
Shifted neurons
New terminals
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Incremental Training in Adults
Linkenhoker BA, Knudsen EI.Incremental training increases the plasticity of the auditory space map in adult barn owls.
Nature 2002
Incremental Training in Adults
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Copyright ©2005 Society for Neuroscience
Figure 1. Effect of prism experience with and without hunting on ITD tuning in the OT of an adult barn owl. Bergan, J. F. et al. J. Neurosci. 2005 [arrows in B, D, E indicate expected ITD shift]
FACILITATION BY HUNTING
PLASTICITY IN THE SOMATOSENSORY PATHWAY
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Somatotopic maps
After Woolsey & van der Loos, 1970
Rat Somatosensory Pathway
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BARREL CORTEX PLASTICITY
Woolsey & van der Loos, Science, 1973
Normal Spared C and β Lesion C row
BARREL CORTEX PLASTICITY
Fig. 4. Supernumerary whiskers and extra barrels in an Ad-cShh-infected embryo. From Ohsaki et al 2002 Devel Brain ReS
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Somatotopic map plasticity is Hebbian
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Somatotopy matches lifestyle
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VISUAL ACUITY
Visual Stimulation and Single Unit RecordingVisual Stimulation and Single Unit Recording
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Visual ModulesVisual Modules