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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