Local origin of field potentials in visual cortex.
The local field potential (LFP) is increasingly used to measure the combined activity of neurons within a region of tissue. Yet, available estimates of the size of this region are highly disparate, ranging from several hundred microns to a few millimeters. To measure the size of this region directly, we used a combination of multielectrode recordings and optical imaging. We determined the orientation selectivity of stimulus-evoked LFP signals in primary visual cortex and were able to predict it on the basis of the surrounding map of orientation preference. The results show that > 95% of the LFP signal originates within 250 microm of the recording electrode. This quantitative estimate indicates that LFPs are more local than often recognized and provides a guide to the interpretation of the increasing number of studies that rest on LFP recordings.
Katzner
Steffen
S
Smith-Kettlewell Eye Research Institute, San Francisco, CA 94115, USA.
Nauhaus
Ian
I
Benucci
Andrea
A
Bonin
Vincent
V
Ringach
Dario L
DL
Carandini
Matteo
M
D000818:Animals; D002415:Cats; D004566:Electrodes; D004594:Electrophysiology / Q000379:methods; D005074:Evoked Potentials, Visual / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D014793:Visual Cortex / Q000166:cytology / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology