Responses of Cortical Extrastriate Area 21a Neurons Specialized in Motion Detection
According to a generally accepted concept, the stationary structure of the receptive field of a visually sensitive central neuron predetermines transformation and central processing of the incoming information, including that related to moving visual stimuli. We found, however, that a small group...
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Інститут фізіології ім. О.О. Богомольця НАН України
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| Cite this: | Responses of Cortical Extrastriate Area 21a Neurons Specialized in Motion Detection / D.K. Khachvankian, H.R. Aslanian, B.A. Harutiunian-Kozak, A.L. Ghazaryan, J.A. Kozak // Нейрофизиология. — 2015. — Т. 47, № 3. — С. 233-239. — Бібліогр.: 22 назв. — англ. |
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Khachvankian, D.K. Aslanian, H.R. Harutiunian-Kozak, B.A. Ghazaryan, A.L. Kozak, J.A. 2019-02-17T17:08:10Z 2019-02-17T17:08:10Z 2015 Responses of Cortical Extrastriate Area 21a Neurons Specialized in Motion Detection / D.K. Khachvankian, H.R. Aslanian, B.A. Harutiunian-Kozak, A.L. Ghazaryan, J.A. Kozak // Нейрофизиология. — 2015. — Т. 47, № 3. — С. 233-239. — Бібліогр.: 22 назв. — англ. 0028-2561 https://nasplib.isofts.kiev.ua/handle/123456789/148195 612.84:612.825.5 According to a generally accepted concept, the stationary structure of the receptive field of a visually sensitive central neuron predetermines transformation and central processing of the incoming information, including that related to moving visual stimuli. We found, however, that a small group of visually sensitive neurons of the cat extrastriate cortical area 21a does not fit this statement and exhibits no responses to stationary visual stimuli while responding vigorously to moving images. The results of our experiments showed that response patterns of these neurons to moving stimuli display high degrees of diversification and processing of incoming visual information. We suppose that these neurons may be strictly specialized in the detection and central processing of visual information necessary for perception of moving images. Згідно із загальноприйнятою концепцією, стаціонарна структура рецептивного поля візуочутливого нейрона визначає специфіку трансформації та центральної обробки зорової інформації, що надходить, включно з інформацією про рухливі візуальні стимули. Ми, проте, виявили, що властивості невеликої групи візуочутливих нейронів у кортикальній екстрастріатній зоні 21a не узгоджуються з цим положенням; вони не генерують відповідей на пред’явлення стаціонарних зорових стимулів, але в той же час інтенсивно відповідають на пред’явлення рухомих зображень. Як показали результати наших експериментів, патерни відповідей даних нейронів на дію рухомих стимулів демонструють високі рівні диверсифікації та обробки візуальної інформації, що надходить. Ми вважаємо, що ці нейрони можуть бути високоспеціалізованими щодо детекції та центрального процесінгу зорової інформації, необхідної для перцепції рухомих зображень. en Інститут фізіології ім. О.О. Богомольця НАН України Нейрофизиология Responses of Cortical Extrastriate Area 21a Neurons Specialized in Motion Detection Відповіді кортикальних нейронів екстрастріатної зони 21а, спеціалізованих на детекції рухів Article published earlier |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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DSpace DC |
| title |
Responses of Cortical Extrastriate Area 21a Neurons Specialized in Motion Detection |
| spellingShingle |
Responses of Cortical Extrastriate Area 21a Neurons Specialized in Motion Detection Khachvankian, D.K. Aslanian, H.R. Harutiunian-Kozak, B.A. Ghazaryan, A.L. Kozak, J.A. |
| title_short |
Responses of Cortical Extrastriate Area 21a Neurons Specialized in Motion Detection |
| title_full |
Responses of Cortical Extrastriate Area 21a Neurons Specialized in Motion Detection |
| title_fullStr |
Responses of Cortical Extrastriate Area 21a Neurons Specialized in Motion Detection |
| title_full_unstemmed |
Responses of Cortical Extrastriate Area 21a Neurons Specialized in Motion Detection |
| title_sort |
responses of cortical extrastriate area 21a neurons specialized in motion detection |
| author |
Khachvankian, D.K. Aslanian, H.R. Harutiunian-Kozak, B.A. Ghazaryan, A.L. Kozak, J.A. |
| author_facet |
Khachvankian, D.K. Aslanian, H.R. Harutiunian-Kozak, B.A. Ghazaryan, A.L. Kozak, J.A. |
| publishDate |
2015 |
| language |
English |
| container_title |
Нейрофизиология |
| publisher |
Інститут фізіології ім. О.О. Богомольця НАН України |
| format |
Article |
| title_alt |
Відповіді кортикальних нейронів екстрастріатної зони 21а, спеціалізованих на детекції рухів |
| description |
According to a generally accepted concept, the stationary structure of the receptive field of a
visually sensitive central neuron predetermines transformation and central processing of the
incoming information, including that related to moving visual stimuli. We found, however, that a
small group of visually sensitive neurons of the cat extrastriate cortical area 21a does not fit this
statement and exhibits no responses to stationary visual stimuli while responding vigorously to
moving images. The results of our experiments showed that response patterns of these neurons
to moving stimuli display high degrees of diversification and processing of incoming visual
information. We suppose that these neurons may be strictly specialized in the detection and
central processing of visual information necessary for perception of moving images.
Згідно із загальноприйнятою концепцією, стаціонарна
структура рецептивного поля візуочутливого нейрона визначає специфіку трансформації та центральної обробки
зорової інформації, що надходить, включно з інформацією про рухливі візуальні стимули. Ми, проте, виявили, що
властивості невеликої групи візуочутливих нейронів у кортикальній екстрастріатній зоні 21a не узгоджуються з цим
положенням; вони не генерують відповідей на пред’явлення
стаціонарних зорових стимулів, але в той же час інтенсивно
відповідають на пред’явлення рухомих зображень. Як показали результати наших експериментів, патерни відповідей
даних нейронів на дію рухомих стимулів демонструють високі рівні диверсифікації та обробки візуальної інформації,
що надходить. Ми вважаємо, що ці нейрони можуть бути високоспеціалізованими щодо детекції та центрального процесінгу зорової інформації, необхідної для перцепції рухомих зображень.
|
| issn |
0028-2561 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/148195 |
| citation_txt |
Responses of Cortical Extrastriate Area 21a Neurons Specialized in Motion Detection / D.K. Khachvankian, H.R. Aslanian, B.A. Harutiunian-Kozak, A.L. Ghazaryan, J.A. Kozak // Нейрофизиология. — 2015. — Т. 47, № 3. — С. 233-239. — Бібліогр.: 22 назв. — англ. |
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NEUROPHYSIOLOGY / НЕЙРОФИЗИОЛОГИЯ.—2015.—T. 47, № 3 233
UDC 612.84:612.825.5
D. K. KHACHVANKIAN¹, H. R. ASLANIAN¹, B. A. HARUTIUNIANKOZAK¹, A. L. GHAZARYAN¹, J. A. KOZAK²
RESPONSES OF CORTICAL EXTRASTRIATE AREA 21a NEURONS
SPECIALIZED IN MOTION DETECTION
Received March 25, 2014
According to a generally accepted concept, the stationary structure of the receptive field of a
visually sensitive central neuron predetermines transformation and central processing of the
incoming information, including that related to moving visual stimuli. We found, however, that a
small group of visually sensitive neurons of the cat extrastriate cortical area 21a does not fit this
statement and exhibits no responses to stationary visual stimuli while responding vigorously to
moving images. The results of our experiments showed that response patterns of these neurons
to moving stimuli display high degrees of diversification and processing of incoming visual
information. We suppose that these neurons may be strictly specialized in the detection and
central processing of visual information necessary for perception of moving images.
Keywords: extrastriate cortical area 21a, visually sensitive neurons, receptive field,
moving stimuli.
¹ Laboratory of Sensory Physiology, Institute of Applied Problems of Physics,
National Academy of Sciences of Armenia, Yerevan, Armenia.
² Department of Neuroscience, Cell Biology, and Physiology, Wright State
University, Dayton, USA.
Correspondence should be addressed to
D. K. Khachvankian (email: khachvankyan@mail.ru),
H. R. Aslanian (email: hayk_aslanyan@yahoo.com),
А. L. Ghazaryan (email: ana13am@yahoo.com),
B. A. HarutiunianKozak (email: rnigagik@gmail.com),
J. A. Kozak (email: ashotkozak@aim.com).
INTRODUCTION
Neurophysiological mechanisms underlying central
information processing in the visually sensitive
cortical areas, including the extrastriate area 21a, still
constitute a fundamental problem in neuroscience.
Since the pioneering studies of Hartline [1, 2� and
Hubel and Wiesel [35�, the “receptive field” (RF)
concept of a single visually sensitive neuron has
become the most important substrate for interpretation
of the mechanisms governing perception of stationary
and moving visual images. In their classic studies
of visually evoked responses of neurons in the cat
and monkey striate cortex, Hubel and Wiesel [4, 5�
classified cells on the basis of their response patterns
to presentation of stationary visual stimuli. Thus,
according to the proposed concept, the stationary
structure of the receptive field, as a rule, predetermines
transformation and central processing of incoming
visual information concerning the moving visual
stimuli. A number of subsequent studies have, in
general, confirmed this concept [69�. At the same
time, the experiments carried out by our group showed
that certain discrepancies in this approach are evident
[1012�. In our studies of information processing
related to moving visual images, we observed only a
weak correlation (in some cases, even almost complete
absence of correlation) between the stationary structure
of the neuronal RF and response patterns of the cell
to presentation of moving stimuli. In this report, we
describe further observations concerning a relatively
small group of neurons in the cat extrastriate area
21a, which did not react to stationary flashing light
spots positioned in their RFs (handheld stimuli) but
responded strongly to the moving visual stimuli. In
earlier studies, such neurons were reported to be found
in the ventral geniculate nucleus (VGN) [13� and striate
cortex [14�. We investigated in detail the qualitative
and quantitative characteristics of the activity of such
neurons with the aim to elucidate the function of
this group of neurons in central processing of visual
information with special attention to processing of the
moving image perception.
METHODS
The methods used were described in detail in our
earlier publications [11, 15�. The cats were initially
anaesthetized with αchloralose (60 mg/kg, i.m.).
Tracheotomy and cannulation of the femoral artery
NEUROPHYSIOLOGY / НЕЙРОФИЗИОЛОГИЯ.—2014.—T. 47, № 3234
D. K. KHACHVANKIAN, H. R. ASLANIAN, B. A. HARUTIUNIANKOZAK et al.
were performed. Throughout the experiment,
anaesthesia was maintained by additional chloralose
doses given i.v. (1020 mg/kg per hour). The animal’s
head was fixed in a stereotaxic apparatus (Horsley
Clarke, modified for visual research). A piece of
the bone (6 × 10 mm) was removed from the skull
above the posterior suprasylvian gyrus. The opening
was covered with 3% agar in 0.9% NaCl solution to
prevent brain pulsations and to provide visual control
of electrode penetrations into the cortical area 21a.
The animal was immobilized by i.m. injection of
7 mg/kg Ditilin (diiodide dicholine ester of succinic
acid). Artificial respiration was administered at
19 min1, with stroke volume 20 ml/kg body mass.
The body temperature was kept constant at 38° C
with a heating pad. The pupils were dilated by topical
application of 0.1% atropine solution, and the corneas
were protected from drying with zeropower contact
lenses. Nictitating membranes were retracted by
instilling NeoSynephrine (1%) into the conjunctival
sac. The arterial blood pressure was continuously
monitored and stabilized at 90100 mm Hg. The ECG
and EEG were continuously monitored throughout
the experiment. In some cases, a standard procedure
of labeling (electrocoagulation) of the successful
recording points and perfusion of the animal with a
fixative (10% formalin solution) was carried out. The
recording sites were identified after examination of
50μmthick histological sections of the brain.
Extracellular recordings of singleunit activity
were provided by tungsten microelectrodes coated
with vinyl varnish leaving a 13 µm bare tip
(impedance 1015 MΩ). Action potentials (APs) were
conventionally amplified, triggered, and passed to a
digital analyzer for online analysis and data storage
using a poststimulus time histogram (PSTH) mode;
16 realizations for each stimulus type were averaged.
The RF borders for each visually responsive cell were
defined by presentation of handheld stimuli and
plotted on a perimeter screen. Positions of the optic
disc and area centralis (AC) were also plotted on the
screen, and the RF position within the visual field
was referenced to the AC location [16, 17�. For initial
characterization, the RF borders of a visually sensitive
single cell were outlined in detail by presentation of
stationary flashing light spots (0.52.0 deg) positioned
consecutively across the handplotted RF area. Then,
moving visual stimuli (spots, bars, edges, and slits of
different sizes and contrasts) were presented with the
speed of motion 20 deg/sec. The direction sensitivity
index (DSI) for each neuron was calculated according
to the formula DSI = (1 – Rnpr/Rpr) ∙ 100 [8�, where
Rnpr and Rpr are responses to the nonpreferred and
preferred directions, respectively. Neurons with DSI =
= 100 were classified as unidirectional, with DSI =
= 20 to 99 as asymmetric directional, and with DSI = 0
to 19 as bidirectional units. The contrast specificity
index (CSI) was calculated for light (L), and dark (D)
stimuli according to the contrast specificity = (ΣL/ΣL +
+ ΣD) × 100 [17�, where indices of 100, about 50, and
0 characterized units responding to light only, with
approximately equal response intensities to light and
dark, and responding to dark only, respectively.
The values of contrast for the light and dark
stimuli against the background were kept constant
with the contrast defined as (Lmax – Lmin)/(Lmax +
+ Lmin), where Lmax and Lmin are the maximum and
minimum luminances, respectively. The bright stimuli
were 15 lx against a 2 lx background, and the dark
stimuli were, conversely, 2 lx luminance against a
15 lx background.
RESULTS
A total of 152 visually sensitive neurons was examined
within the extrastriate area 21a of the cat cortex. As
a first step, careful determination of the RF borders
and of its position within the visual coordinate
system was performed for each cell using a handheld
visual stimulus. Afterwards, the response patterns of
neurons were investigated by applying stationary and
moving visual stimuli of constant contrast. The RF
borders and the stationary functional RF structure
were outlined by stationary flashing light spots
(0.5–2 deg) positioned consequently in the test
zones over the entire RF surface. A great majority
of the examined neurons (144 of 152) showed clear
cut responses to both stationary flashing light spots
and moving visual stimuli. A small group of neurons
(8 of 152) demonstrated, however, a complete
absence of response to stationary flashing light
spots but generated intense AP bursts to presentation
of moving visual stimuli. Moreover, these neurons
with the absence of the stationary RF structure were
able to discriminate contrasts, sizes, and contours
of visual stimuli and direction of their motion. In
this report, results of detailed investigation of the
response profiles of such neurons to moving visual
stimuli are described with the aim to elucidate their
possible role and significance in central processing
of visual information.
NEUROPHYSIOLOGY / НЕЙРОФИЗИОЛОГИЯ.—2015.—T. 47, № 3 235
RESPONSES OF CORTICAL EXTRASTRIATE AREA 21a NEURONS
In Fig. 1, the response patterns of a neuron of this
type are shown. As can be seen, there were no reactions
to a stationary flashing spot (2 deg) positioned
sequentially across the handplotted RF (Fig. 1A, 2,
black dots); only the PSTH of the activity obtained by
stimulation of the RF central position is presented. By
contrast, when dark and bright spots (2 deg) moved
along the horizontal axis of the handplotted RF, bursts
of neuronal discharges were elicited (Fig. 1B, 14).
The moving dark spot evoked nondirectional responses
of the cell at two opposite movement directions (Fig.
1B, 1, 2), with a weak inhibitory phase after the
AP bursts. The bright spot movement also evoked
a nondirectional response pattern, but with a strong
inhibitory phase before the cell discharges (Fig. 1B,
3, 4). When analyzing the response profiles described
above, one may suggest that the stationary RF of this
neuron should be characterized as a homogeneous
“off” RF. As is shown in Fig. 1A, 1, this is, however,
not the case when a stationary flashing spot is
presented. Furthermore, quantitative measurements
of the numbers of APs indicated that this neuron is,
probably, capable of discriminating the contrast of
A
B C
D
1
1
2
3
1
2
3
2
2º
3º
2º 2º 2º3º 3º 3º7º 7º 7º
7º
100
50C
S
I
D
S
I
D
S
I
0
100
50
0
100
50
0
7º
3º
2º
20º RF
AC
V
H
10º
80º 70º
40
40
40
A
B
1
1
3
2
2
4
V
H
20º
RF
AC
10º
80º
2º
2º 2.5 sec
2º
2º
50º
70º
40
F i g. 1. Response patterns of an area 21a neuron to presentation of
stationary and moving visual stimuli. A, 1) Absence of responses of
the neuron to the stationary flashing light spot (2 deg) positioned
in the receptive field center (outlined by handheld stimuli). A,
2) Handplotted position of the neuronal RF within the visual
coordinate system; black dots indicate consecutive positions (test
zones) of the flashing spot across the RF. B, 1, 2) PSTHs of the
responses of the same neuron to the dark spot (2 deg) across the
RF horizontal axes moving leftward (1) and rightward (2). B, 3, 4)
PSTHs of the neuron responses to the movement of the bright spot
(2 deg) in two opposite directions. Arrows indicate the direction
moving of the visual stimulus. Explanations are the same for the
following figures.
Р и с. 1. Патерни відповідей нейрона зони 21а на пред’явлення
стаціонарних та рухомих зорових стимулів.
F i g. 2. Response patterns of a neuron insensitive to presentation of
a stationary flashing light spot but highly sensitive to moving visual
stimuli. A, 1) Lack of neuronal responses to a stationary visual
stimulus. A, 2) Handplotted position of the neuronal RF within the
visual coordinate system. B, 13) PSTH of the neuronal responses
to presentation of moving bright spots of different sizes indicated
under the histograms. C, 13) PSTH of the responses of the same
neuron to the movement of dark spots of different sizes. D, 13)
Plots of the contrast specificity index (CSI) measured for different
sizes of applied moving stimuli (1), and the direction sensitivity
index (DSI) for bright (2) and dark (3) moving stimuli. Explanations
for the following figures are the same.
Р и с. 2. Патерни відповідей нейрона, не чутливого до
пред’явлення стаціонарної світлової блимаючої плями, але
високочутливого до візуальних рухомих стимулів.
2.5 sec
50º
NEUROPHYSIOLOGY / НЕЙРОФИЗИОЛОГИЯ.—2014.—T. 47, № 3236
D. K. KHACHVANKIAN, H. R. ASLANIAN, B. A. HARUTIUNIANKOZAK et al.
the applied stimulus. The bright stimulus is preferable
considering the greater number of APs compared to
that related to the dark stimulus (CSI=58).
In Fig. 2, the response patterns of another neuron
of this group are illustrated. As is seen in Fig. 2A, 1,
the neuron did not respond to the stationary flashing
bright spot (2 deg). At the same time, moving 2deg
spots of two opposite contrasts elicited intense
discharges of the neuron at two opposite motion
directions (Fig. 2B, 1, C, 1). When the size of moving
spots was increased to 3 deg, nondirectional responses
of the neuron to a dark moving stimulus were elicited
(Fig. 2C, 2), while a bright spot elicited clearcut
directionally asymmetric responses (DSI = 65.5),
with the preferred direction from the right to the left
(Fig. 2B, 2). A further increase in the size of the
stimulus (7 deg) led to a clearcut directionselective
response pattern of the neuron. As is seen in Fig. 2B, 3,
both bright spot and dark spot motions (Fig. 2C, 3)
elicited directionally asymmetric responses of the
neuron with the same rightward preferred direction
(DSI =100 for the bright spot and 74.3 for the dark
spot; Fig. 2D and D, 3). Thus, the neuron clearly
reveals certain abilities to discriminate the contrasts
and motion directions of the applied visual stimuli.
Furthermore, two of eight neurons investigated
showed significant qualitative and quantitative
differences between the discharge patterns in relation
to opposite contrasts and also in relation to the
movement orientation of applied visual stimuli. Figure
3 illustrates the response patterns of one of these
neurons to stationary and moving visual stimuli. The
neuron responded by a bimodal discharge pattern to a
3deg bright spot moving in two opposite directions,
which means that there are two spatially distinct
discharge centers in the RF separated from each other
by an about 16deg angular distance (Fig. 3B, 1). A
dark moving spot of the same dimension (3 deg) evoked
monomodal responses of the neuron (Fig. 3B, 2).
The same neuron generated no responses when the
orientation of stimulus movement changed from
the horizontal to the vertical one (Fig. 3B, 3, 4). In
other words, both stimuli (bright and dark) became
ineffective in this case. Thus, the neuron not only
discriminated the contrast of the applied stimulus,
demonstrating qualitatively and quantitatively
different pattern properties at two opposite contrasts,
but was also able to discriminate orientations of the
stimulus motion within the visual space. Again, it
was difficult to propose a conceptual interpretation
of the observed phenomenon because we could not
characterize the stationary RF organization.
For the next neuron, the response patterns to
moving visual stimuli of different sizes were tested.
As can be seen in Fig. 4A, 1, this neuron generated no
spike responses to the flashing light spot positioned in
the RF test zones (Fig. 4A, 2, black dots). However,
a bright rectangle (2 deg × 4 deg) moving along the
horizontal axis of the RF of this unit (determined by
presentation of handheld stimuli) elicited AP bursts
when the stimulus entered and left the RF; strong
inhibition of background spiking of the neuron was
observed at the movement along the RF horizontal axis
in both rightward and leftward directions (Fig. 4B, 1).
The movement of the same rectangle at an oblique
orientation (135 deg visual angle) evoked almost the
same response pattern, namely inhibition of background
discharges when crossing the RF (Fig. 4B, 2).
The opposite contrast of the same stimulus (dark
rectangle) induced excitatory responses of the neuron
A
B
3º 3º
3º 3º
RF
AC
20º
V
H
10º
80º 70º
40
40
F i g. 3. Response patterns of a neuron to the movement of as visual
stimulus in the horizontal and vertical directions. A, 1) PSTH of
neuronal activity at presentation of a stationary flashing spot. A, 2)
The position of the handplotted RF within the visual coordinate
system. B, 1, 2) PSTHs of neuronal responses to the movement of
bright (1) and dark (2) spots along the RF horizontal axis. B, 3, 4)
PSTHs of the responses to the movement of bright (3) and dark (4)
spots along the RF vertical axis.
Р и с. 3. Патерни відповідей нейрона на рухи візуального
стимулу в горизонтальному та вертикальному напрямках.
2.5 sec
50º
1
1
2
3
42
NEUROPHYSIOLOGY / НЕЙРОФИЗИОЛОГИЯ.—2015.—T. 47, № 3 237
RESPONSES OF CORTICAL EXTRASTRIATE AREA 21a NEURONS
at both horizontal and 135 degorientation motions
(Fig. 4C, 1, 2).
An unexpected result was observed when the size
of the rectangles was changed. The same neuron
responded by excitation with AP bursts to the
movement of a 6 deg × 11 deg bright rectangle along
the horizontal axis across the RF (Fig. 5A, 1) and to
the oblique (135 deg) movement of such stimulus
through the RF (Fig. 5A, 2). An excitatory effect of
the stimulus movement along the horizontal axis of
the RF was observed when the opposite contrast of the
stimulus (dark) was used (Fig. 5B, 1). A change in the
motion orientation to 135 deg of the visual coordinate
system, on the other hand, evoked clearcut inhibition
of background neuronal activity upon crossing the RF
central region, while excitation was observed when
the stimulus entered and left RF borders (Fig. 5B, 2).
These data point to a high level of discrimination of
incoming visual information related to the size and
orientation of the moving visual stimuli across the RF,
even though the examined neuron did not demonstrate
a conventional stationary RF organization.
In summary, the presented data show that there is a
relatively small population of neurons (about 5%) in
the area 21a that do not respond to stationary visual
stimuli but reveal a strong ability to detect moving
images and to discriminate their contrasts, sizes,
directions, and orientations of motion of such visual
images. It is likely that these neurons participate in
A
C
B
6º×11º
6º×11º 6º×11º
6º×11º
6º×11º
6º×11º
40
2.5 sec
50º
1 1
2 2
1 2 3
100
50C
S
I
D
S
I
D
S
I
0
100
50
0
100
50
0
F i g. 5. Response patterns of the same neuron, as in Fig. 4, to the
movements of bright and dark rectangles of a greater dimension. A,
1, 2) PSTHs of neuronal responses to the horizontal (1) and oblique
(135 deg) (2) movements of a bright rectangle (6 deg × 11 deg).
B, 1, 2) PSTHs of the responses to horizontal (1) and oblique (2)
movements of a dark rectangle (6 deg × 11 deg). C, 13) Contrast
specificity index (1) and direction sensitivity index measured for the
movements of 6 deg × 11 deg bright (2) and dark (3) rectangles in
the horizontal and a 135 deg directions.
Р и с. 5. Патерни відповідей того самого нейрона, що й на рис.
4, на рухи яскравих та темних прямокутників більшого розміру.
A
B C
D
2º×4º
2º×4º 2º×4º
2º×4º 2º×4º
2º×4º
RF
AC
20º
V
H
10º
80º 70º
40
40
2.5 sec
50º
1
11
2
22
1 2 3
100
50C
S
I
D
S
I
D
S
I
0
100
50
0
100
50
0
F i g. 4. Response patterns of a neuron to presentation of moving
bright and dark rectangles. A, 1) Lack of responses to a stationary
flashing light spot. A, 2) Position of the handplotted RF within the
visual coordinate system. B, 1, 2) PSTHs of neuronal responses to
a (2 deg × 4 deg) bright rectangle moving in the horizontal (1) and
oblique (135 deg) directions (2) across the RF. C, 1, 2) PSTHs of
the responses of the same neuron to the horizontal (1) and oblique
(2) movements of the dark (2 deg × 4 deg) rectangle. D, 13)
Contrast specificity index (CSI) (1) and direction sensitivity index
(DSI) for presentation of bright (2) and dark (3) rectangles moving
in the horizontal and oblique directions.
Р и с. 4. Патерни відповідей нейрона на пред’явлення яскравих
та темних рухомих прямокутників.
NEUROPHYSIOLOGY / НЕЙРОФИЗИОЛОГИЯ.—2014.—T. 47, № 3238
D. K. KHACHVANKIAN, H. R. ASLANIAN, B. A. HARUTIUNIANKOZAK et al.
central processing of visual information by acting as
highly specialized motion detectors.
DISCUSSION
It has already been reported by Fries and Albus [19�
that a stationary map of the RF of a visually sensitive
neuron in the cat striate cortex is insufficient to
explain the response characteristics of this unit to
moving stimuli. Dynamic properties of the neuron are
much more complicated. In an earlier communication
[10�, we also emphasized that there is a group of
darksensitive neurons in the cat lateral suprasylvian
cortical area, which showed extremely low sensitivity
to stationary flashing spots but could be effectively
triggered by moving visual stimuli. The results
of the experiments described above agree with
such observations and, importantly, indicate that a
relatively small group of neurons in the extrastriate
area 21a is also insensitive to stationary flashing light
spots (thus, in fact, having no stationary RF) but react
vigorously and with diversified patterns of activity to
presentation of moving visual stimuli.
As a working hypothesis, we suggest that activation
of neighboring neurons brought up by the moving
stimuli crossing the RF surrounding may exert certain
influences on the neuronal activity under investigation.
Earlier, it was well established by different research
groups that excitation of the RF surrounding area
exerts significant effects on the neuronal response
patterns by modulating the activity profile [15, 20
22�. Thus, it seems probable that a neuron, being
insensitive to the stationary visual stimuli, probably
undergoes transient changes in its excitability when
moving visual stimuli activate the neighboring groups
of neurons by crossing their RFs within the visual
space before entering the RF of the examened.
Our results show that there are significant
quantitative and qualitative differences in the intensity
of evoked spiking of the described neurons depending
on the size and contrast of the applied visual stimuli.
Thus, a high degree of information diversification
does exist in this case. These results allow us to
suggest that relatively small groups of neurons in the
central visual pathways, while being unresponsive to
stationary visual stimuli, are strictly specialized in
motion dеtection. Probably, this feature is provided
by modulatory influences of the adjacent activated
neurons having RFs overlapping the RF of the neuron
under investigation. It is likely that such interactions
are transient events occurring within the time interval
of moving of the visual image. Evidently, interaction
within a group of neurons can provide a more precise
and efficient estimation and processing of incoming
visual information than the activity of a single isolated
neuron might be expected to. Further investigations are
needed to elucidate the nature and neurophysiological
mechanisms underlying such specialized temporary
influences in central processing of visual information.
The study was carried out in accordance with the statements
of the Council Directive regarding the protection of animals
used for experimental and other scientific purposes (86/609/
EEC, 1986, Strasbourg) and respective regulations of the Ethics
Committee at the Institute of Applied Problems of Physics,
National Academy of Sciences of Armenia, Yerevan, Armenia.
The authors of this study, D. K. Khachvankian, H. R. Aslanian,
B. A. HarutiunianKozak, A. L. Ghazaryan and J. A. Kozak,
confirm that the research and publication of the results were not
associated with any conflicts regarding commercial or financial
relations, relations with organizations and/or individuals who
may have been related to the study, and interrelations of co
authors of the article.
Д. К. Хачванкян¹, Г. Р. Асланян¹, Б. A. АрутюнянКозак¹,
A. Л. Газарян¹, Ю. А. Козак²
ВІДПОВІДІ КОРТИКАЛЬНИХ НЕЙРОНІВ
ЕКСТРАСТРІАТНОЇ ЗОНИ 21А, СПЕЦІАЛІЗОВАНИХ НА
ДЕТЕКЦІЇ РУХІВ
¹ Інститут прикладних проблем фізики НАН Вірменії,
Єреван (Республіка Вірменія).
² Державний університет Райт, Дейтон (США).
Р е з ю м е
Згідно із загальноприйнятою концепцією, стаціонарна
структура рецептивного поля візуочутливого нейрона ви
значає специфіку трансформації та центральної обробки
зорової інформації, що надходить, включно з інформаці
єю про рухливі візуальні стимули. Ми, проте, виявили, що
властивості невеликої групи візуочутливих нейронів у кор
тикальній екстрастріатній зоні 21a не узгоджуються з цим
положенням; вони не генерують відповідей на пред’явлення
стаціонарних зорових стимулів, але в той же час інтенсивно
відповідають на пред’явлення рухомих зображень. Як пока
зали результати наших експериментів, патерни відповідей
даних нейронів на дію рухомих стимулів демонструють ви
сокі рівні диверсифікації та обробки візуальної інформації,
що надходить. Ми вважаємо, що ці нейрони можуть бути ви
сокоспеціалізованими щодо детекції та центрального про
цесінгу зорової інформації, необхідної для перцепції рухо
мих зображень.
NEUROPHYSIOLOGY / НЕЙРОФИЗИОЛОГИЯ.—2015.—T. 47, № 3 239
RESPONSES OF CORTICAL EXTRASTRIATE AREA 21a NEURONS
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