# Regulation of Synaptic Plasticity in Visual Cortex

> **NIH NIH R01** · JOHNS HOPKINS UNIVERSITY · 2020 · $409,375

## Abstract

Visual experience during an early critical period is essential for the normal maturation of visual cortex,
such that altered vision at this stage can have deleterious consequences, including amblyopia. Previous
studies established that synaptic connections in the visual could be modified through a process that
depends on both neural activity (Hebbian synaptic plasticity) and long-range neuromodulatory inputs that
convey information on the behavioral state of the animals. The goal of this project is to elucidate the
cellular mechanisms by which two prominent neuromodulators, norepinephrine and serotonin, control the
induction Hebbian synaptic plasticity in the visual cortex. Specifically we will examine the hypothesis that
norepinephrine and serotonin can act retroactively as reward-like signals to reinforce recently activated
synapses.
This proposal builds upon our recent finding that in cortical slices certain patterns of synaptic activity
produce “eligibility traces” for synaptic modification. These eligibility traces are transient and silent tags
that can be converted into long-term potentiation if 2-adrenergic receptors (AR) are promptly activated,
or into long-term depression if 5HT2C serotonergic receptors are activated. This retroactive action of the
monoamines on Hebbian plasticity is a novel mechanism of neuromodulator that contrast and
complement the more traditional view of neuromodulators as enabling factor that prime of promote
subsequent plasticity. We plan to study the role of the induction/conversion of eligibility traces in visual
cortical plasticity in vivo and to assess its impact in visual cortical responses.
The findings resulting from the proposed can have translational consequences. In particular, the
possibility of inducing rapid and targeted cortical modifications with the aid of neuromodulators can be
relevant for restoring visual cortical functions in adults. Besides the obvious relevance of neural plasticity
to the development of visual capabilities, it is likely that similar processes may form the basis for some
forms of learning and memory in the adult brain.

## Key facts

- **NIH application ID:** 9961592
- **Project number:** 5R01EY012124-22
- **Recipient organization:** JOHNS HOPKINS UNIVERSITY
- **Principal Investigator:** Alfredo Kirkwood
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $409,375
- **Award type:** 5
- **Project period:** 1998-03-01 → 2022-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9961592

## Citation

> US National Institutes of Health, RePORTER application 9961592, Regulation of Synaptic Plasticity in Visual Cortex (5R01EY012124-22). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/9961592. Licensed CC0.

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