INVESTIGADORES
FARINA Walter Marcelo
artículos
Título:
The response of the hawk moth Macroglossum stelllatarum to translotory movements of stripe patterns
Autor/es:
FARINA WALTER M.; KRAMER, D; VARJU, D
Revista:
JOURNAL OF COMPARATIVE PHYSIOLOGY A-SENSORY NEURAL AND BEHAVIORAL PHYSIOLOGY
Editorial:
SPRINGER
Referencias:
Lugar: Berlin; Año: 1995 vol. 176 p. 551 - 562
ISSN:
0340-7594
Resumen:
The European hawk moth Macroglossum
stellatarum, while collecting nectar in hovering flight in
front of flowers, follows moving stripe patterns in the
lateral visual field. This response counteracts a second
one, that is the animals' effort to stabilize their distance
from dummy flowers. We investigated the response to
motion stimuli in the lateral visual field using
sinusoidally oscillating stripe patterns (Fig. 1), as
well as its interaction with the distance stabilizing
response.
2. In both responses moths attempt to compensate
for image speed. The balance between the two depends
on the number of elementary motion detectors stimulated
by the dummy flower and the stripe pattern,
respectively. Increasing the diameter of the dummy
flower (Figs. 2 to 4) or the spatial frequency of the stripe
pattern (Fig. 7) shifts the balance in favour of distance
stabilization. The reverse is true when the length of the
stripes in the pattern (Fig. 5) or their number is increased
(Fig. 6). It does not matter whether the stripe
pattern is presented in the lateral (Fig. 4A) or in the
dorsal and ventral visual field (Fig. 4B).
3. The gain-frequency relations of the response to
the lateral stripe pattern obtained with dummies in two
different positions within the drum have their maxima
around 3 Hz and decline rapidly towards lower and
higher frequencies like the response of a bandpass filter.
The distance stabilizing response also has bandpass
properties, but with a broad plateau between 0.15 and
5 Hz (Fig. 8). The most likely explanation for this
W. M. Farina 1 9 D. Kramer 2 9 D. Varjfl ([~)
Universit~it Tiibingen, Lehrstuhl fiir Biokybernetik,
Auf der Morgenstelle 28, D-72076 Tiibingen, Germany
Permanent address:
l Departamento de Ciencias Biol6gicas, Universitad de Buenos
Aires, Ciudad Universitaria, CP 1428, Buenos Aires, Argentina
Present address:
2Universifiits-Augenklinik, Abteilung Neuroophthalmologie, Sektion
Visuelle Sensorik, R6ntgenweg 11, D-72076 Tiibingen, Germany
difference is that there is a regional or direction-dependent
variation of motion detector properties.
4. The responses to ramp-like stimuli are phasic in
accordance with the amplitude frequency characteristics,
but the responses to progressive (front to back)
and regressive motion of the pattern differ (Figs 9, 10).
5. The response appears to depend on the azimuthal
position of the stripe pattern within the visual field
(Fig. 11). It is strongest when the pattern covers equally
large parts of the frontal and caudal visual fields. The
optomotor sensitivity to translational pattern motion
is higher in the frontal than in the caudal visual field
(Fig. 12, Table 1).
6. When the stripe pattern on one side is removed,
the response amplitude is halved. There is no detectable
turning response around the vertical axis to the oscillation
of the stripe pattern (Fig. 13, Table 2).
7. The possible role of the response to pattern movements
parallel to the longitudinal body axis under
natural conditions is discussed.