First published online October 18, 2006
Journal of Experimental Biology 209, 4339-4354 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02517
A `bright zone' in male hoverfly (Eristalis tenax) eyes and associated faster motion detection and increased contrast sensitivity
Andrew D. Straw1,*,
Eric J. Warrant2 and
David C. O'Carroll1
1 Discipline of Physiology, School of Molecular and Biomedical Science, The
University of Adelaide, SA 5005, Australia
2 Vision Group, Department of Cell and Organism Biology, Lund University,
Lund, Sweden
View larger version (52K):
[in a new window]
|
Fig. 1. Optical characteristics of Eristalis tenax eyes showing the
`bright zone' of males, in which facet diameter is maximal in the
fronto-dorsal eye but is not associated with smallest interommatidial angle.
Interommatidial angles are given as the average of the angles across
horizontal and vertical sampling baselines. Data are from a single male and
single female fly and in close agreement with data from the other fly tested
of each sex. f=frontal, d=dorsal, l=lateral.
|
|
View larger version (10K):
[in a new window]
|
Fig. 2. Local preferred directions (LPD) and local motion sensitivities (LMS) of
Eristalis LPTCs. The direction of the arrow indicates the LPD and the
magnitude gives the LMS, as defined in the Materials and methods. The origin
of the arrows is displayed on a Mercator projection, but the direction and
magnitude are displayed using Euclidian geometry to facilitate LMS comparison
(male HSN, N=3; female HSN, N=5; male HSNE, N=3;
female HSNE, N=5). HSN, HSNE, horizontally sensitive N, NE
neurones.
|
|
View larger version (38K):
[in a new window]
|
Fig. 3. Response as a function of contrast of Gaussian windowed sinusoidal grating
(Gabor patch). (A) Single trials showing responses to traditional `contrast
step' stimulus. (B) `Contrast ramp' stimulus measures contrast-response
relationship more rapidly. Blue line shows mean response and gray fill shows
mean response ± instantaneous s.d. (C) Comparison of methods shown in A
and B plotted on logarithmic contrast axis. Smooth red line shows analytic fit
to contrast ramp data. Data are from frontal portion of the receptive field of
a single male HSN cell viewing sinusoidal grating at 0.1 cycles
deg.-1 at 5 Hz. Values are means ± s.d. from at least 3
trials. Az, azimuth; El, elevation.
|
|
View larger version (33K):
[in a new window]
|
Fig. 4. Summary of contrast-response relation under several conditions showing that
the contrast ramp method estimates contrast sensitivity similarly to the
contrast step method, but much more quickly. Data analyzed as in
Fig. 3C. All parameters as
listed, spatial frequency= 0.1 cycles deg.-1. (A-E) Data from two
HSNE cells from several retinal locations. (F) HSN cell from
Fig. 3 viewing laterally
positioned grating. All data from male flies. Values are means ±
instantaneous s.d. from a minimum of 3 trials. Az, azimuth; El, elevation.
|
|
View larger version (45K):
[in a new window]
|
Fig. 5. Responses to contrast ramp stimulus at a range of temporal (TF) and spatial
frequencies (SF) in the frontal portion of the receptive field of a single
male HSN neuron. The mean response to 3 or more trials is shown in black for
each combination of spatial and temporal frequency as plotted as in
Fig. 3C. Parameter fits are
shown in red. The data are plotted on logarithmic contrast axis. Minimum of 3
trials per trace; azimuth=0°, elevation=60°. Details of fitting
described in Materials and methods. Decade C, tenfold Michelson contrast
variation.
|
|
View larger version (18K):
[in a new window]
|
Fig. 6. Contrast-response surfaces of a single male HSN cell showing faster
temporal dynamics and higher spatial frequency tuning in the frontal portion
of the receptive field. The thick gray line in each panel is an iso-velocity
line at the preferred velocity, the optimal temporal frequency (TF) divided by
the optimal spatial frequency (SF). (A) Data are from the frontal portion of
the receptive field, azimuth=0°, elevation=60°. (B) Data are from the
lateral portion of the receptive field, azimuth=90°, elevation=60°.
Height of surface is the estimated response to a grating of Michelson contrast
1.0 based on fit parameters calculated at each spatial and temporal frequency.
Fit parameters for A are shown in Fig.
5. Contour interval=1.0 mV, with negative responses dotted.
|
|
View larger version (26K):
[in a new window]
|
Fig. 7. Comparison of temporal frequency (TF) tuning at two receptive field
locations of HSN cells showing sexually dimorphic contrast sensitivity and
temporal dynamics. Frontal receptive field (A,C,E) for HSN cells is defined as
0° azimuth and 60° elevation. Lateral receptive field (B,D,F) is
defined as 90° azimuth and 60° elevation. Responses were estimated for
Michelson contrasts 1.0 (A,B) and 0.2 (C,D) and the contrast sensitivity was
calculated for a criterion response of 2 mV (E,F). Estimated response and
contrast sensitivity were calculated from contrast ramp data (for details see
Materials and methods). Spatial frequency 0.1 cycles deg.-1. Values
are means ± s.e.m.; males, N=5 (filled squares), females,
N=6 (open circles).
|
|
View larger version (30K):
[in a new window]
|
Fig. 8. Comparison of spatial frequency (SF) tuning at two receptive field
locations of HSN cells showing sexually dimorphic contrast sensitivity and
lateral spatial frequency tuning. Estimated contributions from Type 1 and Type
2 EMDs are given as arrow thickness and again as the height of small bars. EMD
contributions and smooth curves were fit to the shown data with a two EMD
model constrained by interommatidial angle data taken from
Fig. 1. Free parameters were
total gain, relative EMD contribution, and saturation. These parameters can be
found in Table 1. Temporal
frequency 5 Hz. Values are means ± s.e.m.; males, N=5 (filled
squares), females, N=6 (open circles).
|
|
View larger version (25K):
[in a new window]
|
Fig. 9. Comparison of temporal frequency (TF) tuning at two receptive field
locations of HSNE cells showing little sexually dimorphic contrast sensitivity
or temporal dynamics. Spatial frequency 0.1 cycles deg.-1. Values
are means ± s.e.m.; males, N=4 (filled squares), females,
N=5 (open circles).
|
|
View larger version (28K):
[in a new window]
|
Fig. 10. Comparison of spatial frequency tuning at two receptive field locations of
HSNE cells showing little sexually dimorphic contrast sensitivity and lateral
spatial frequency tuning. Temporal frequency 5 Hz. Values are means ±
s.e.m.; males, N=4 (filled squares), females, N=5 (open
circles).
|
|
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati 
Twitter What's this?
© The Company of Biologists Ltd 2006
