Receptive Field Dynamics in
Adult Primary Visual Cortex
CHARLES D. GILBERT & TORSTEN N. WIESEL
GROUP B6
MARGARITA BLAJEVA
CAITLIN H. CHEONG
PARI CHOWDHARY
WISSAM A. SAMAD
BROOKE THORNTON
Presentation Outline
 Background
 Critiques
 Related Study: Macular Degeneration
 Other Areas of Interest
Pari
Research Issue
Pari
Does the primary visual cortex reorganize its cortical
topography as a result of changes to its afferent
input?
Are these results applicable to humans?
Experimental Method & Hypothesis
Pari
Methods
-Lesion: Focal Binocular retinal lesions.
(Parafoveal, 8 mm wide)
-Testing: Vertical Electrode penetrations into V1 & LGN.
(Before lesion, immediately after, and months later)
Hypothesis
- Removing afferent input through a retinal lesion
results in a rearrangement of cortical and
subcortical topography.
Pari
Empirical Evidence and Theoretical Conculsions
 Cortical rearrangement around edges of retinal scotoma
 Recovery of silenced areas months later.
 Silent region remained in LGN
(Does NOT support hypothesis)
Theoretical assumption: Horizontal cortical connections
responsible for topographic reorganization.
Lateral Geniculate Nucleas
Wissam
- Located in thalamus
- Main organized relay
pathway to V1.
- Study: indicates no
topographical
rearrangement.
-
Anatomical study?
-
Geniculocortical
afferents insufficient to
account for cortical
recovery.
Adapted from Ullal, G. (2008). Lecture 6: Vision and Retinal Processing [Power Point Slides]. Retrieved from McMaster Learnlink.
Wissam
What did the anatomical studies yield?
 Deafferentation
or Wallerian
Degeneration?
 New axon
sprouting?
Adapted from Newell, K. (2008). Lecture 9: Visial System [PDF]. Retrieved from SOLS Wollongong University (Australia).
What About the many connections of
the LGN?
Wissam
Other LGN
connections
- To brainstem
- Massively
overweigh
retinal input.
Necessary LGN
organization
- Change is not
good?
Adapted from Derrington, A. (2001). The lateral geniculate nucleus. Current Biology , 11 (16), pp. R635-7.
Margarita
Horizontal Cells vs. Connections
Horizontal Cells
● present in
the retina
● lateral
inhibition
Horizontal Connections
 arise in
pyramidal cells
 cortical cell
communication
Adapted from Ullal, G. (2008). Lecture 6: Vision and Retinal Processing [Power Point Slides]. Retrieved from McMaster Learnlink.
Further Research by Gilbert et al. (1994)
Cellular Mechanisms of Cortical Reorganization
Margarita
 FOCUS:
o Intracortical axonal sprouting in the horizontally projecting
plexus of cortical neurons
 Reorganized vs. Normal cortex
 RESULTS:
Very abundant terminal branching
 Denser axon fibres in reorganized cortex

Further Research by Gilbert et al. (1995)
Visual Pathway Reorganization Loci
Margarita
 FOCUS: Determine reorganization loci
 Comparing topographic alterations in the
Primary Visual Cortex and dorsal LGN
 Thalamocortical afferents involvement?
Caitlin
Age-Related
Macular
Degeneration
(McManus et al., 2008)
Adapted from McManus, J. N., Ulmann, S., & Gibert, C. D. (2008). A computational model of perceptual
fill-in following retinal degeneration. Journal of Neurophysiology , 99 (5), 2086-2100.
Computational model displayed that
topographic reorganization occurs in humans
with age-related macular degeneration
(AMD)
- Human subjects with macular degeneration
do not receive visual input from damaged
portions of their retinae yet their vision is
complete and continuous
Caitlin
Impressive Methodology
Eliminated bias by choosing
receptive fields unaffected by
simple eye movement
Wissam & Margarita
Could the
reverse be true
for the retina
in terms of
cellular
reorganization
and plasticity
if the cortex
was lesioned?
Area MT (V5)?
References
Bear, M. F., Connors, B., & Pardiso, M. (2006). Neuroscience: exploring the brain (3rd
Edition ed.). Philadelphia: Lippincott Williams & Wilkins.
Buonomano, D. V., & Merzenich, M. M. (1998). Cortical plasticity: from synapses to maps.
Annual Review of Neuroscience , 21, 149-86.
Darian-Smith, C., & Gilbert, C. D. (1994). Axonal sprouting accompanies functional
reorganization in adult cat striate cortex. Letters to Nature , 368, 737-740.
Darian-Smith, C., & Gilbert, C. D. (1995). Topographic reorganization in the striate cortex
of the adult cat and monkey is cortically mediated. The Journal of Neuroscience , 15
(3), 1631-1647.
Derrington, A. (2001). The lateral geniculate nucleus. Current Biology , 11 (16), pp. R6357.
Gilbert, C. D. (1998). Adult Cortical Dynamics. Physiological Reviews , 78, 467-485.
Gilbert, C.D., Das, A., Ito, M., Kapadia, M., & Westheimer, G. (1996). Spatial integration
and cortical dynamics. Proceedings of the National Academy of Sciences, 93, 615622.
Gilbert, C. D., & Wiesel, T. N. (1992). Receptive field dynamics in adult primary visual
cortex. Letters to Nature , 356, 150-152.
McManus, J. N., Ulmann, S., & Gibert, C. D. (2008). A computational model of perceptual
fill-in following retinal degeneration. Journal of Neurophysiology , 99 (5), 2086-2100.
Other Areas of Interest
Margarita
 Limiting Visual Input to One Eye (Gilbert, 1998)
 VPA Rat Study and Horizontal Connections
(Personal Communication, Dr. D. Day, 2008)
 Area MT
 perception of movement and visuospatial behaviour
(Gilbert, 1998)