PMID- 9893803
OWN - NLM
STAT- MEDLINE
DCOM- 19990208
LR  - 20190728
IS  - 0042-6989 (Print)
IS  - 0042-6989 (Linking)
VI  - 38
IP  - 23
DP  - 1998 Dec
TI  - Elongated physiological summation pools in the human visual cortex.
PG  - 3735-41
AB  - The visibility of gratings improves with increasing stimulus area. This effect is 
      usually interpreted as being due to probability summation between the outputs of 
      linear, independent spatial filters, although non-linear spatial summation can 
      have similar effects [1]. In order to distinguish between probabilistic and 
      physiological summation models, we measured contrast thresholds using the Visual 
      Evoked Potential (VEP). Our previous work [2] suggests that spatial summation in 
      the VEP is nonlinear and that it occurs preferentially for collinear 
      configurations. Traditional probability summation models predict that areal 
      summation will improve threshold independent of stimulus configuration. Contrast 
      thresholds were derived from VEP contrast response functions for either circular 
      or elongated Gabor patches with aspect ratios up to 6:1. The carrier orientation 
      was either the same as the patch envelope orientation (collinear) or orthogonal 
      to it. Response amplitudes were larger and contrast sensitivity was higher for 
      collinear configurations. The results are consistent with nonlinear, 
      configuration dependent summation that is more extensive along the axis of 
      orientation.
FAU - Polat, U
AU  - Polat U
AD  - Smith-Kettlewell Eye Research Institute, San Francisco, CA 94115, USA.
FAU - Norcia, A M
AU  - Norcia AM
LA  - eng
GR  - EY06579/EY/NEI NIH HHS/United States
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PT  - Research Support, U.S. Gov't, P.H.S.
PL  - England
TA  - Vision Res
JT  - Vision research
JID - 0417402
SB  - IM
MH  - Contrast Sensitivity
MH  - Evoked Potentials, Visual
MH  - Humans
MH  - Pattern Recognition, Visual/*physiology
MH  - Sensory Thresholds/physiology
MH  - Visual Cortex/*physiology
EDAT- 1999/01/20 00:00
MHDA- 1999/01/20 00:01
CRDT- 1999/01/20 00:00
PHST- 1999/01/20 00:00 [pubmed]
PHST- 1999/01/20 00:01 [medline]
PHST- 1999/01/20 00:00 [entrez]
AID - S0042-6989(97)00426-4 [pii]
AID - 10.1016/s0042-6989(97)00426-4 [doi]
PST - ppublish
SO  - Vision Res. 1998 Dec;38(23):3735-41. doi: 10.1016/s0042-6989(97)00426-4.