Table Of ContentPROGRESS IN BRAIN RESEARCH
VOLUME 112
EXTRAGENICULOSTRIATE
MECHANISMS UNDERLYING
VISUALLY -GUIDED
ORIENTATION BEHAVIOR
EDITED BY
MASAO NORITA
Department of Neupbiology and Anatomy, Niigata University School of Medicine,A sahimachi
/ Niigata, Japan
TAKEHIKO BAND0
Department of Physiolw, Niigata University School of Medicine, Asahimachi Niigata, Japan
BARRY E. STEIN
Department of Neumbiology and Anatomy, The Bowman Gray School of Medicine, Wake Forest,
Wnston Salem, NC, USA
ELSEVIER
AMSTERDAM - LAUSANNE - NEW YORK - OXFORD - SHANNON -TOKYO
1996
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Library of Congress Cataloging-In-Publication Data
Extrageniculostriate mechanisms underlying visually-guided orientation
behavior / edited by Masao Norita. Takehiko Bando. Barry Stein.
p. cm. -- (Progress in brain research : v. 112)
Includes bibliographical references and index.
ISBN 0-444-82347-6 (volume : alk. paper). -- ISBN 0-444-80104-9
(series : alk. paper)
1. Visual cortex--Congresses. 2. Visual perception--Congresses.
I. Norlta. Masao. 11. Bando. Takehiko. 111. Stein, Barry E.
IV. Series.
[DNLM: 1. Visual Cortex--physiology--congresses. 2. Visual
Pathways--physiology--congresses. 3. Orientation--physiology-
-congresses. 4. Superior Colliculus-rghysiology--congresses.
5. Behavior, Animal--physiology--congresses. W1 PR667J v.112 1996
/ WL 307 E9515 19961
QP376.P7 vol. 112
[QP383.151
612.8'2 s--dc2O
r612.8'41
DNLMIDLC
for Library of Congress 96-414 10
CIP
Printed in The Netherlands on acid-free paper
V
List of Contributors
T. Bando, Department of Physiology, Niigata University School of Medicine, Asahi-machi,
Niigata, Niigata 951, Japan
M. Behan, Department of Comparative Biosciences and Center for Neuroscience, University of
Wisconsin, Madison, Wisconsin 53706, USA
Gy. Benedek, Department of Physiology, Albert Szent-Gyorgyi Medical University, Szeged,
Hungary
C.A. Bennett-Clarke, Department of Anatomy and Neurobiology, Medical College of Ohio,
Toledo, OH 43699-0008, USA
D. Boire, DCpartement de Psychologie and Centre de Recherche en Sciences Neurologiques,
Universitk de Montrkal H3C 357, and Department of Neurology and Neurosurgery, Montreal
Neurological Institute, McGill University, 3801 University St., Montreal, Canada
S. Carlile, University Laboratory of Physiology, Parks Road, Oxford OX1 3PT, UK
C. Casanova, Departments of Surgery-Ophthalmology and of Physiology and Biophysics,
Faculty of Medicine, University of Sherbrooke, Sherbrooke, Quebec, Canada, J1H 5N4
S. Chimoto, Department of Physiology, Institute of Basic Medical Sciences, University of
Tsukuba, Tsukuba, Ibaraki 305, Japan
. S. Chin, Department of Physiology, Hokkaido University School of Medicine, Sapporo 060,
Japan
V.M. Ciaramitaro, Department of Neuroscience, School of Medicine, University of Pennsylva-
nia, Philadelphia, PA 19104-6074, USA
R.L. Djavadian, Department of Anatomy and Histology, Institute for Biomedical Research, The
University of Sydney, N.S.W. 2006, Australia
B. Dreher, Department of Anatomy and Histology, Institute for Biomedical Research, The
University of Sydney, N.S.W. 2006, Australia
R. Fendrich, Center for Neuroscience, University of California, Davis CA 95616, USA
B.L. Finlay, Department of Psychology, Cornell University, Ithaca, NY 14853, USA
L. Fishcer-Szatmki, Department of Physiology, Albert Szent-Gyorgyi Medical University,
Szeged, Hungary
M.A. Frens, University of Nijmegen, Department of Medical Physics and Biophysics, Geert
Grooteplein 21, NL-6525 EZ Nijmegen, The Netherlands and Neurology Department,
University Hospital, CH 8091 Zurich, Switzerland
Y. Fukuda, Department of Physiology, Osaka University Medical School, Suita 565, Japan
J. Fukushima, Department of Physiology, Hokkaido University School of Medicine, Sapporo
060, Japan
K. Fukushima, Department of Physiology, Hokkaido University School of Medicine, Sapporo
060, Japan
S. Funaki, Department of Neurobiology and Anatomy, Niigata University School of Medicine,
Asahimachi, Niigata 951, Japan
M.S. Gazzaniga, Center for Neuroscience, University of California, Davis CA 95616, USA
N. Hara, Department of Physiology, Niigata University School of Medicine, Asahi-machi,
Niigata, Niigata 951, Japan
vi
M. Herbin, Dcpartement de Psychologie and centre de recherche en sciences neurologiques,
UniversitC de montr6al H3C 357, and Department of Neurology and Neurosurgery, Montreal
Neurological Institute, McGill University, 3801 University St., Montreal, Canada
T.P. Hicks, Tissue Regeneration Group, Institute of Biological Science, National Research
Council of Canada, Building M-54, 1200 Montreal Road, Ottawa, Ontario, Canada, K1A
OR6
S. Hirano, Department of Neurobiology and Anatomy, Niigata University School of Medicine,
Asahimachi, Niigata 951, Japan
K. Hoshino, Department of Neurobiology and Anatomy, Niigata University School of Medicine,
Asahimachi, Niigata 951, Japan
X. Huang, Department of Anatomy and Neurobiology, Medical College of Ohio, Toledo, OH
43699-0008, USA
R.-B. Illing, Unit for Morphological Brain Research, Department of Otorhinolaryngology,
University of Freiburg, 79106 Freiburg, Germany
Y. Inoue, Neuroscience Section, Electrotechnical Laboratory, Tsukubashi, Ibaraki 305, Japan
S. Ireland, Neuroregeneration Laboratory, Department of Anatomy, The University of Hong
Kong, 5 Sassoon Road, Hong Kong
Y. Ito, Department of Neuophysiology, Tokyo Metropolitan Institute for Neuroscience,
Musashidai 2-6, Fuchu-shi, Tokyo 183, Japan
Y. Iwamoto, Department of Physiology, Institute of Basic Medical Sciences, University of
Tsukuba, Tsukuba, Ibaraki 305, Japan
J.H. Gas, Department of Psychology, Vanderbilt University, Nashville, TN 37240, USA
S. Kakei, Department of Physiology and Orthopedic Surgery, School of Medicine, Tokyo
Medical and Dental University, Tokyo 113, Japan
M. Kase, Department of Neurobiology and Anatomy, Niigata University School of Medicine,
Asahimachi, Niigata 951, Japan
!
Y.Y. Katoh, Department of Anatomy, Fujita-Gakuen' Medical University, Toyoake, Japan
K. Kawano, Neuroscience Section, Electrotechnical Laboratory, Tsukubashi, Ibaraki 305, Japan
N.M. Kime, Department of Comparative Biosciences and Center for Neuroscience, University
of Wisconsin, Madison, Wisconsin 53706, USA
A.J. King, University Laboratory of Physiology, Parks Road, Oxford OX1 3PT, UK
T. Kitama, Neuroscience Section, Electrotechnical Laboratory, Tsukubashi, Ibaraki 305, Japan
Y. Kobayashi, ART Human Information Processing Research Laboratory, Kyoto 619-02, Japan
G. KOV~CSD, epartment of Physiology, Albert Szent-Gyorgyi Medical University, Szeged,
Hungary
S. Kurkin, Department of Physiology, Hokkaido University School of Medicine, Sapporo 060,
Japan
J.G. McHaffie, Department of Neurobiology and Anatomy, Bowman Gray School of Medicine,
Wake Forest University, Winston-Salem, NC 27157, USA
R. Meguro, Department of Neurobiology and Anatomy, Niigata University School of Medicine,
Asahimachi, Niigata 951, Japan
R.R. Mize, Departments of Anatomy and Opthalmology and the Neuroscience Center,
Louisiana State University Medical Center, 1901 Perdido Street, New Orleans, LA 70112,
USA
N. Mano, Department of Neuophysiology, Tokyo Metropolitan Institute for Neuroscience,
Musashidai 2-6, Fuchu-shi, Tokyo 183, Japan
R.D. Mooney, Department of Anatomy and Neurobiology, Medical College of Ohio, Toledo,
OH 43699-0008, USA
M. Mustari, University of Texas Medical Branch, Galveston, USA
vii
N. Muto, Department of Physiology and Orthopedic Surgery, School of Medicine, Tokyo
Medical and Dental University, Tokyo 113, Japan
K. Naito, Department of Neurophysiology, Tokyo Metropolitan Institute for Neuroscience,
Tokyo, Japan
M. Norita, Department of Neurobiology and Anatomy, Niigata University School of Medicine,
Asahimachi, Niigata 951, Japan
M. Oka, Department of Neurophysiology, Tokyo Metropolitan Institute for Neuroscience,
Tokyo, Japan
S. Onodera, Department of Anatomy, School of Medicine, Iwate Medical University, Morioka
020, Japan
A.J. Van Opstal, University of Nijmegen, Department of Medical Physics and Biophysics, Geert
Grooteplein 21, NL-6525 EZ Nijmegen, The Netherlands and Neurology Department,
University Hospital, CH 8091 Zurich, Switzerland
G.A. Orban, Laboratorium voor Neuro-en Psycho@siologie, Faculteit der Geneeskunde,
KULeuven, Campus Gasthuisberg, B-3000 Leuven, Belgium
C.K. Peck, Schoool of Optometry, University of Missouri-St. Louis, 8001 Natural Bridge Road,
St. Louis, MO 63121, USA
J. PerCnyi, Department of Physiology, Albert Szent-Gyorgyi Medical University, Szeged, Hun-
Pry
A. Ptito, Center for Neuroscience, University of California, Davis CA 95616, USA, and
Montreal Neurological Institute and Hospital, Montreal, Quebec H3A 2B4, Canada and
DCpartement de Psychologie and centre de recherche en sciences neurologiques, UniversitC
de montrkal, MontrCal H3C 357, Canada
M. Ptito, DCpartement de Psychologie and centre de recherche en sciences neurologiques,
UniversitC de montrCal H3C 357, and Department of Neurology and Neurosurgery, Montreal
Neurological Institute, McGill University, 3801 University St., Montreal, Canada
J.P. Rauschecker, Georgetown Institute for Cognitive and Computational Sciences 3970,
Reservoir Road, NW Washington, DC 20007-2197, and Section on Cognitive neuroscience
Laboratory of Neuropsychology, NIH/NIMH, Bldg. 49, Rm. 1B80, Bethesda, MD 20892-4415,
USA
R.W. Rhodes, Department of Anatomy and Neurobiology, Medical College of Ohio, Toledo,
OH 43699-0008, USA
A. Rosenquist, Department of Neuroscience, School of Medicine, University of Pennsylvania,
Philadelphia, PA 19104-6074, USA
S. Sasaki, Department of Neurophysiology, Tokyo Metropolitan Institute for Neuroscience,
Tokyo, Japan
T. Savard, Departments of Surgery-Ophthalmology and of Physiology and Biophysics, Faculty
of Medicine, University of Sherbrooke, Sherbrooke, Quebec, Canada, J1H 5N4
H. Sawai, Neuroregeneration Laboratory, Department of Anatomy, The University of Hong
Kong, 5 Sassoon Road, Hong Kong
J.W.H. Schnupp, University Laboratory of Physiology, Parks Road, Oxford OX1 3PT, UK
M.Y. Shi, Department of Anatomy and Neurobilogy, Medical College of Ohio, Toledo OH
43699-0008, USA
H. Shibutani, Department of Neuophysiology, Tokyo Metropolitan Institute for Neuroscience,
Musashidai 2-6, Fuchu-shi, Tokyo 183, Japan
H. Shimazu, Department of Neurophysiology, Tokyo Metropolitan Institute for Neuroscience,
2-6 Musashidai, Fuchu, Tokyo 183, Japan
Y. Shinoda, Department of Physiology, School of Medicine, Tokyo Medical and Dental
University, Tokyo 113, Japan
viii
A.L. Smith, University Laboratory of Physiology, Parks Road, Oxford OX1 3PT, UK
P.D. Spear, Department of Psychology and Center for Neuroscience, University of Wisconsin-
Madison, 1202 West Johnson St., Madison, WI 53706, USA
J.M. Sprague, Department of Neuroscience, University of Pennsylvania, School of Medicine,
Philadelphia, PA 19104-6058, USA
K.-F. So, Neuroregeneration Laboratory, Department of Anatomy, The University of Hong
Kong, 5 Sassoon Road, Hong Kong
B.E. Stein, Department of Neurobiology and Anatomy, Bowman Gray School of Medicine,
Wake Forest University, Winston-Salem, NC. 27157-1010, USA
M. Takagi, Department of Physiology, Niigata University School of Medicine, Asahi-machi,
Niigata, Niigata 951, Japan
A. Takemura, Neuroscience Section, Electrotechnical Laboratory, Tsukubashi, Ibaraki 305,
Japan
Y. Tamai, Department of Physiology, Wakayama Medical College, Wakayama 640, Japan
D. Tay, Neuroregeneration Laboratory, Department of Anatomy, The University of Hong
Kong, 5 Sassoon Road, Hong Kong
I.D. Thompson, University Laboratory of Physiology, Parks Road, Oxford OX1 3PT, UK
H. Toda, Department of Physiology, Niigata University School of Medicine, Asahi-machi,
Niigata, Niigata 951, Japan
K.J. Turlejski, Department of Anatomy and Histology, Institute for Biomedical Research, The
University of Sydney, N.S.W. 2006, Australia
J.-G. Villemure, Center for Neuroscience, University of California, Davis CA 95616, USA, and
Montreal Neurological Institute and Hospital, Montreal, Quebec H3A 2B4, Canada
R. Vogels, Laboratorium voor Neuro- en Psychofysiologie,F aculteit der Geneeskunde, KU Leu-
ven, Campus Gasthuisberg, B-3000 Leuven, Belgium
M.T. Wallace, Department of Neurobiology and Anatomy, Bowman Gray School of Medicine,
Wake Forest University, Winston-Salem, NC. 27157-1010, USA
C. Wang, Department of Anatomy and Histology, Institute for Biomedical Research, The
University of Sydney, N.S.W. 2006, Australia
C.M. Wessinger, Center for Neuroscience, University of California, Davis CA 95616, USA, and
Montreal Neurological Institute and Hospital, Montreal, Quebec H3A 2B4, Canada
M. Xiong, Department of Psychology, Cornell University, Ithaca, NY 14853, USA
K. Yamamoto, Department of Physiology, Niigata University Sch'ool of Medicine, Asahi-machi,
Niigata, Niigata 951, Japan
K. Yoshida, Department of Physiology, Institute of Basic Medical Sciences, University of
Tsukuba, Tsukuba, Ibaraki 305, Japan
ix
Preface
It is, perhaps, no exaggeration to note that many of the most fundamental aspects of
our understanding of brain function and maturation have been developed as a result
of studies of the visual system. Thus, interest in the visual system derives not only
from our interest in visual processes per se, but also from it’s utility as a general
model of brain organization.
For many years the visual system was thought to be formed by a comparatively
small number of distinct pathways and target structures. The visual processes in the
midbrain were thought to be involved in reflexive responses to visual stimuli (e.g. eye
movements, pupillary changes) which facilitate the immediate responses necessary to
shift gaze and accommodate the stimulus and varying light levels. On the other hand,
the geniculostriate system and its immediate target structures were viewed as playing
the principal roles in all aspects of visual perception. For some time, a straightforward
hierarchical model was thought to be the most accurate reflection of the stream of
information along thalamocortical and corticocortical pathways. In this model the
thalamus directly activates primary sensory cortex (i.e. striate cortex), which in turn
activates secondary psychic-related para- and peristriate cortex, which directly acti-
vates multi-sensory association, or interpretive, cortex
Though this sort of uni-directional serial processing model remains an integral part
of current concepts of visual cortex organization, the last few years have seen a
dramatic increase in the number of areas known to be involved in mammalian vision,
a far greater understanding of the importance of reciprocal connections, intrinsic
connections, structure-specific modules and modules which span different structures,
as well as the introduction of parallel processing models within the thalamocortical
and corticocortical streams. At the same time, there have been substantial changes in
our views of midbrain functions, as well as the importance of cortical-midbrain (and
corticostriato-nigrotectal) interactions both in terms of sensory processing and
sensorimotor transduction.
These changes in our understanding of the visual system have been most extensive
in how we view the functional contributions of extrageniculostriate mechanisms to
vision and visually-guided behavior. The body of knowledge has become so vast, and is
growing so rapidly, that periodic updates are essential even for experts in the field.
This was the impetus behind bringing together a group of researchers for a satellite
meeting of the Fourth World Congress of Neuroscience which was sponsored by the
International Brain Research Organization. The idea was not only to emphasize the
most current information regarding midbrain and extrastriate mechanisms underlying
vision and visually-guided behavior, but to place these data into the larger context of
how interrelated components of the visual system function to produce coherent visual
experiences and behavior. The international nature of the conference was under-
X
scored by participants from Australia, Canada, China, Eastern and Western Europe,
the U.S. and, of course, our host country, Japan.
The various perspectives of those utilizing different scientific methods made the
interactions quite lively, and several new collaborative arrangements resulted from
these discussions. This volume is, in part, the result of these discussions and interac-
tions. It contains new research findings that are unavailable elsewhere, as well as
reviews and broad perspectives in which existing data from multiple sources are
brought together in order to help us understand the structure and function of
extrageniculostriate visual areas.
The New Hotel Koshiji-So in Muikamachi, Niigata, Japan was a perfect setting for
this meeting. The relaxed atmosphere in this lovely mountainous region of Japan was
conducive to the active exchange of ideas bearing directly on which of the current
functional concepts are likely to endure and which must be discarded. For two-and-a-
half days participants attended all-day scientific sessions that were bracketed by
wonderful Japanese meals, Japanese baths, and the opportunity to climb any one of
several nearby mountains. Two highlights of the many delightful gastronomic experi-
ences were the soba extravaganza prepared by hand by Dr. Norita and his teacher
(under the scrutiny and kibitzing of most of us attending the conference), and the
extraordinary banquet that marked the official end to the conference. We are deeply
indebted to the students from Niigata University who contributed significantly to the
organization and coordination of the conference, to Yumiko Norita for organizing day
trips, and to the hotel staff for their unflagging patience, cheerful assistance, and
gracious attention to every detail.
Bany E. Stein
Niigata 1996
M. Norita, T. Bando and B. Stein (Eds.)
prOg...r in Brain Reseanh, Vol 112
8 1996 Elsevier Science BV. All rights reserved.
CHAPTER 1
Neural mechanisms of visual orienting responses
James M. Sprague
Depattments of Neuroscience, and Cell and Developmental Biology, School of Medicine, Uniwsity of Pennsylvania,
Philadebhia, PA 19104-6058, USA
Introduction tory, disturbed the salivary conditioned responses
he was studying. Initially Pavlov’s interest was
Visual orienting refers to the coordinated move- focused on the motor or directional component of
ment of eyes, head and body to explore the envi- the orienting reflex, but in later years he de-
ronment surrounding the animal or person, and is scribed a number of unspecific elements: pupil-
a response crucial to the development and the lary dilatation, EEG desynchronization, psy-
survival of the individual and species. Orienting chogalvanic response, increase in cerebral blood
has several components: (1) the reflexive response flow. In view of these so-called unspecific factors,
triggered by the appearance of an object in the Zernicki (1987) proposed the name of ‘arousal
visual field; (2) the internally programmed, ex- component’ of orienting for them. He went fur-
ploratory motor search which may occur without
ther and distinguished three components of the
a specific visual target; and (3) the shift of atten-
orienting response: (1) targeting (directional); (2)
tion which accompanies both reflex and search.
arousal; and (3) perceptual. The orienting re-
Thus we speak of visuomotor orienting and ori-
sponse has greatly interested Russian psy-
enting of attention as parts of the same response,
chologists and physiologists and has been studied
which also in the cat may consist of dilatation of
and reviewed by Sokolov (1960, 1963, 1975).
the pupils, widening of the palpebral hures,
Orienting is a function for exploration of the
pinnal movements, extension of the vibrissa
environment by telereceptors of eyes, ears and
around eyes and mouth, tensing muscles of the
nose and by receptors on the body surface; thus it
body in preparation for movement, general
is multimodal in operation-olfaction, vision,
arousal and with it changes in blood pressure and
acoustic and somesthetic. If the provoking stimuli
heart rate. Orienting can be considered as the
are repetitive and found to be uninteresting and
leading edge of the brain’s guidance of behavior,
and as such it provides a spatial framework upon unimportant, orienting shows rapid habituation,
which the more complex functions of perception, but is it highly sensitive to changes of the stimuli
discrimination, recognition, and visuomotor re- which will re-instate the response?
sponses operate effectively. Orienting can be directed ahead of the animal,
The concept of the orienting reflex originated above, below or to either side. It is obvious that a
in Russia in Pavlov’s laboratory around the turn response cannot be directed to both sides at the
of the century (he mentioned it for the first time same time, so that the neuronal discharge must
in a lecture given in St. Petersburg in 1910). He be facilitated on one side of the brain (con-
found that unexpected stimuli, frequently audi- tralateral to the orienting movement) and inhib-
2
ited on the opposite side. The side to which receive a reward. Fixation is strengthened by tap-
orienting is directed will be attended to, the op- ping the forceps holding the food, and once it is
posite area of space or body will be largely unat- predictable, a second food stimulus is introduced
tended or neglected. In the normal animal, ori- into a segment of right or left visual field, which
enting responses shift in this reciprocal manner elicits an orientation of head, eyes and body
from side to side as the animal responds to vari- toward the stimulus. The animal is released and
ous stimuli in the environment and explores the rewarded at the site of the 2nd stimulus (see
world around it. Loss of orienting may result from Sprague and Meikle, 1965; Sherman, 1974, 1977;
lesions in the brain, which if unilateral, cause a Wallace et al., 1989 for details). In addition to
neglect of extrapersonal or body space contralat- visual perimetry, the following capacities were
era1 to the lesion (see Sprague et al., 1973). examined open field visual following, visual plac-
Contralateral visual neglect follows lesions in ing, blink-to-threat, ability to localize stationary
many areas of the brain-prefrontal cortex, frontal stimuli, relative neglect of the left or right hemi-
eye fields, somesthetic Area I, parietal and occipi- field to the presentation of two simultaneous sti-
tal lobes, hypothalamus, thalamus, intralaminar muli in opposite fields, eye movements, pupillary
nuclei, basal ganglia (striatum, substantia nigra), symmetry and responsiveness, and open fieM visu-
superior collidus and tegmentum-although dif- ally guided behavior (jumping to floor, etc.). These
ferent neurological mechanisms are operative for auditory capacities were assessed startle re-
each area. Therefore, visual orienting responses, sponse, accuracy of auditory localization, and pin-
including shifts of attention, are generated by nae mobility. The following tactile tests were per-
widely distributed networks that include all of formed localization of stimuli of the body and
these regions of the brain (see Mesulam, 1981). limbs and tactile placing of the four limbs. In
Neuronal processing in the visual cortex is ex- addition, the animal's spontaneous motor behav-
tensively distriiuted and involves virtually half of ior was observed for postural asymmetries, cir-
the brain of many mammals, including those which cling, ataxia, etc. Finally, the following standard
have been intensely studied in the laboratory - reflexes were examined pinnal, vibrissal, buccal,
rat, gerbil, hamster, tree shrew, cat, bush baby, palpebral, righting, hopping, blink-to-bright light,
owl monkey and macaque. In the cat some 20 and withdrawal to touch and light pinch of all
areas of cortex have been identified as involved in limbs (see Sprague, 1966b).
vision. Many of these areas are retinotopically
organized, and contain spatial maps ranging from
Cortex involved in visual orienting
fine-grained to coarse in representation of the
structure of the environment. It is likely that most
of these areas are 'looking' into contralateral Unilateral lesions were placed in specific cortical
visual space and are sensitive to events occurring areas which have been defined anatomically and
there. This conclusion is supported by the deficits physiologically (Otsuka and Hassler, 1962; Sanides
in orienting which follow lesions in the visual and Hoffman, 1969; Tusa et al., 19811, and the
cortical areas of the cat, the results of which are animals were rigorously tested over many months.
summarized below. The experimental plan was first to extirpate the
Visuomotor orienting in the cat has been mea- so-called 'primary' visual cortex which in the cat
sured in perimetxy tests in which the visual fields consists of areas 17 and 18; this cortex receives an
are divided into segments (15-30"). The food-de- exclusive projection from laminae A and A1 of
prived animal is trained to accept handling and the dorsolateral geniculate (WNJ and a signifi-
restraint with the eyes aligned along a horizontal cant projection from lamina C, as well as smaller
line, and to fixate a food stimulus directly ahead projections from C1 to C2 and the medial inter-
at 0" and when released to go rapidly forward to laminar nucleus, MIN (see Sprague et al., 1977;
