Receptive Field Dynamics in Adult Primary Visual

CortexGroup A3

Presenters: Anastasia Christopher, Carol Rego, Sarah McNeilTechnical Experts: Bonnie Chan, Herman Gill, Marisa Leung

Brief overview of Module 3 Background information and important

definitions Anatomy of the brain Lateral Geniculate Nucleus

◦ Method◦ Results

Primary Visual Cortex◦ Method◦ Results

Conclusion

Table of ContentsAnastasia Christopher

By: Charles Gilbert and Torsten Wiesel

Receptive Field Dynamics in Adult Primary Visual Cortex

Anastasia Christopher

Important Definitions

Receptive Field Size

Cortical Topography

Binocular Retinal Lesion

Scotoma

Anastasia Christopher

Is the locus of change in regards to sensory input located at the cortical level (Primary Visual

Cortex) or at a prior stage in the sensory pathway (Lateral

Geniculate Nucleus)?

Anastasia Christopher

Lateral Geniculate Nucleus (LGN)

Anastasia Christopher

Primary Visual CortexAnastasia Christopher

Immediately After Lesion 2 Months After Lesion

LGN

Primary Visual Cortex

Anastasia Christopher

Studied 2 cats and 1 monkey

Topographical mapping of the LGN

Multiple electrode penetrations across the LGN

Two injections of retrograde tracers in V1

LGN - MethodsCarol Rego

Large silent area about 1mm in diameter

Shift in RF position

LGN – Electrode Readings Carol Rego

Immediately After Lesion 2 Months After Lesion

LGN

________________

• Large silent area

• Shift in RF position

• No evidence in plasticity observed

Primary Visual Cortex

________________ ________________

Carol Rego

Studied 4 cats and 6 monkeys

RF maps were made using vertical electrode penetration

RF maps were made at the same sites before, immediately after, and 2 months after making the lesion

Primary Visual Cortex - Methods

Sarah McNeil

Immediately after:

◦ Inactivity in original sites

◦ 5X larger sites

◦ Centrifugal shift

Primary Visual Cortex - Results

Sarah McNeil

Before lesion

Immediately after lesion

2 months after:

◦ RF field size shrunk

◦ 5˚ centrifugal shift in position

◦ Area of activity expanded beyond affected area

Primary Visual Cortex - Results

Sarah McNeil

Before Lesion 2 Months

After Lesion

Initial shock

Long term consolidation

Sarah McNeil

Immediately After Lesion 2 Months After Lesion

LGN

________________

• Large silent area

• Shift in RF position

• No evidence in plasticity observed

Primary Visual Cortex

• 5X larger in RF sites

• Centrifugal shift >1˚

• RF field size shrunk to several times the original size

• Area of activity expanded

• Centrifugal shift 5˚

Sarah McNeil

Anastasia Christopher

Is the locus of change in regards to sensory input located at the cortical level (Primary Visual

Cortex) or at a prior stage in the sensory pathway (Lateral

Geniculate Nucleus)?

Brain is high in plasticity

Compensation of damaged tissue as a result of binocular retinal lesions does not take place in LGN

Takes place at the cortical level of V1

ConclusionAnastasia Christopher