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1.
D. K. Khachvankyan B. A. Arutyunyan-Kozak R. L. Dzhavadyan G. G. Grigoryan 《Neurophysiology》1982,14(3):205-210
The structure of receptive fields of single neurons in the lateral suprasylvian area of the cat's cortex was studied. Receptive fields of neurons in this area are larger (up to 2000 deg2 or more) than those of the visual projection cortex. A difference was found in the sizes of these fields of the same neuron when measured by presentation of a black object and spot of light. Experimental results showed that most neurons of the area (104 of 148) that are sensitive to visual stimulation respond clearly to flashes of a stationary spot of light. Because of this feature the structure of the receptive fields of the neurons were studied by point by point testing of their whole surface. Intensities of on- and off-components of on-off neurons were found to differ. Only 16% of receptive fields had equal numbers of discharges in on- and off-components of the on-off response. Dominance of one component was observed in 84% of on-off neurons. Receptive fields with several discharge centers are a characteristic feature of neurons in this area. A concentric organization of the receptive fields was found in 11% of neurons.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan, Translated from Neirofiziologiya, Vol. 14, No. 3, pp. 278–283, May–June, 1982. 相似文献
2.
Neuronal organization in the Clare-Bishop cortical association area was studied by consecutive vertical penetration of an electrode and analysis of unit responses to photic stimulation during each penetration. Activity of one or two neurons was recorded during 131 penetrations, and activity of over 3 neurons responding to photic stimulation (visually driven) during 55 penetrations. In 8 of the 55 penetrations all neurons discovered in each had identical characteristics; this type of organization corresponded most of all to the columnar organization of the cortical neurons. In 24 penetrations the neurons were arranged in groups: two or three neurons of one type intermingled with neurons of other types. In 18 penetrations considerable overlapping of the receptive fields of neurons in the same column was observed. A chaotic distribution of neurons with different characteristics was found in 5 penetrations. It is suggested that the organization of neurons in the Clare-Bishop area in columns as functional units of cortical structure is not the principal type of their organization.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 11, No. 4, pp. 297–302, July–August, 1979. 相似文献
3.
D. K. Khachvankyan Yu. A. Kozak A. L. Kazaryan A. B. Sharanbekyan Z. A. Vagramyan B. A. Kharutyunyan-Kozak 《Neurophysiology》2012,44(1):33-41
Using extracellular recording of spike activity from single neurons of field 21a of the cat neocortex, we examined in detail
the spatial organization of receptive fields (RFs) of such cells after conditions of presentation of an immobile blinking
light spot (a static RF) and moving visual stimuli (dynamic RFs). As was shown, the excitability of different RF subfields
of a group of neurons possessing homogeneous on–off organization of the static RF changes significantly depended on the contrast, shape, dimension, orientation, and direction
of movement of the applied mobile visual stimulus. This is manifested in changes in the number of discharge centers and shifts
of their spatial localization. A hypothesis on the possible role of synchronous activation of the neurons neighboring the
cell under study in the formation of an additional neuronal mechanism providing specialization of neuronal responses is proposed. 相似文献
4.
Khachvankyan D. K. Martirosyan L. V. Harutiunian-Kozak B. A. Ékimyan A. A. Kazaryan A. L. Vagramyan Z. A. 《Neurophysiology》2004,36(1):40-49
We studied the responses of neurons of the extrastriate cortical area 21b of the cat to changes in orientation of the movements of visual stimuli within the receptive field (RF) of the neuron under study. Our experiments demonstrated that 24 of 108 cells (22%) responded differentially to a certain extent to orientation of the movements of visual stimuli. As a whole, neurons of the area 21b did not demonstrate fine tuning on the optimum angle of orientation. In many cases, neuronal responses to different orientations of the movement of visual stimulus depended significantly on specific parameters of this stimulus (its shape, dimensions, and contrast). Some directionally sensitive neurons responded to a change in orientation of the movement of visual stimuli by modification of the index of directionality. We also studied spatial organization of the RF of neurons with the presentation of stationary visual stimuli. Comparison of the neuronal responses to a change in orientation of the movements of stimuli and to presentation of stationary stimuli showed that the correlation between the orientation sensitivity of the neuron under study and the stationary functional organization of its RF was insignificant. We hypothesize that inhibitory processes and subthreshold influences from a space surrounding the RF play a special role in the formation of the neuronal responses generated in the associative visual cortical regions to visual stimulation. 相似文献
5.
B. A. Harutiunian-Kozak D. L. Khachvankyan A. A. Ékimyan J. A. Kozak L. V. Martirosyan Z. A. Vagramyan É. G. Bagdasaryan 《Neurophysiology》2002,34(6):406-415
On cats with pretrigeminal brainstem transection, we studied the properties of visually sensitive neurons of the extrastriate associative cortical area 21b. The dimensions and spatial distribution of the receptive fields (RF) of the neurons within the vision field were determined. It was found that large-sized RF prevailed within the area 21b (10 to 200 deg2, 61%; greater than 200 deg2, 22%), whereas small-sized RF (1 to 10 deg2) constituted 17% of all the studied RF. Stationary visual stimuli evoked on–off, off, and on responses in 43, 30, and 27% neurons of the area 21b, respectively. In the cases where moving stimuli were presented, 35% of the neurons demonstrated directional sensitivity; the rest of the neurons (65%) were directionally insensitive. We also found a group of neurons that were capable of differentiating not only the direction of the stimulus movement along the RF but also the dimension, shape, and orientation of a complicated moving stimulus. Taking into account the data obtained, we discuss the functional role of the neurons, which demonstrated a specific (specialized with respect to a set of the parameters of visual stimulus, and not to a single parameter) response in central processing of the sensory information. 相似文献
6.
B. A. Arutyunyan-Kozak D. K. Khachvankyan A. S. Oganyan A. G. Tutundzhyan 《Neurophysiology》1978,10(1):16-22
Electrical activity of single unit in the Clare-Bishop visual association area of the cortex was studied in acute experiments on cats immobilized with Flaxedil and after pretrigeminal sections. The method of extracellular recording of action potentials of single units was used. The experimental results showed that 95.5% of cells responding to visual stimulation responded to movement of a spot of light in the receptive field of the neurons, and 55% of the cells responded selectively to the direction of movement. Some neurons responded to movement of a stimulus only when it entered and left the receptive field. About 85.3% of cells responded to a flashing spot of light, and also to a general change in the intensity of illumination of the receptive field. The receptive field of neurons of the Clare-Bishop area in most cases were in the form of stripes with their long axis horizontal. The results point to the important role of this cortical association area in the central analysis of visual information.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSSR, Erevan. Translated from Neirofiziologiya, Vol. 10, No. 1, pp. 22–29, January–February, 1978. 相似文献
7.
D.?K.?Khachvankyan B.?A.?Harutiunian-KozakEmail author L.?V.?Martirosyan A.?A.?Ekimyan G.?G.?Grigoryan J.?A.?Kozak E.?G.?Bagdasaryan 《Neurophysiology》2005,37(3):194-204
Organization of the receptive fields (RFs) of neurons of the extrastriate associative region 21b of the cerebral cortex was
studied in cats. Most neurons under study (63%) were “monocular,” while 37% of the cells were “binocular” units. Among 178
neurons examined in detail, heterogeneous RF functional organization was typical of about 76% of the units; point-to-point
testing of the entire RF area by stationary stimuli resulted in the generation of various types of responses (on, off, or on-off). The rest of the neurons (24%) generated homogeneous responses. The dimension, form, and functional organization of RFs
of the neurons under study depended to a certain extent on the parameters of visual stimuli used for the measurements. Examination
of the influence of the visual space, which surrounded the RF, on responses of the neurons evoked by stimulation of the RF
per se showed that darkening of the visual space adjacent to the RF inhibited neuronal responses to moving stimuli; in some cases
the responses were totally suppressed. Analysis of spatial overlapping of the RF sequentially recorded in the course of each
insertion of the electrode showed that the density of distribution of the overlapping RF areas of neighboring neurons with
the RF of the examined neuron is irregular, and that the RF is of a mosaic nature. We hypothesize that the visual space surrounding
the RF plays a significant role in the formation of responses of visually sensitive neurons to presentation of moving stimuli.
Neirofiziologiya/Neurophysiology, Vol. 37, No. 3, pp. 223–234, May–June, 2005. 相似文献
8.
B. A. Harutiunian-Kozak D. K. Khachvankyan G. G. Grigoryan J. A. Kozak A. B. Sharanbekyan 《Neurophysiology》2010,42(3):175-184
We studied changes in the spatial parameters of receptive fields (RFs) of visually sensitive neurons in the associative area
21a of the cat cortex under conditions of presentation of moving visual stimuli. The results of experiments demonstrated that
these parameters are dynamic and depend, from many aspects, on the pattern of the stimulus used for their estimation. Angular
lengths of the horizontal and vertical axes of the RFs measured in the case of movement of the visual stimuli exceeded many
times those determined by presentation of stationary blinking stimuli. As is supposed, a visual stimulus, when moving along
the field of vision, activates a certain number of the neurons synaptically connected with the examined cell and possessing
RFs localized along the movement trajectory. As a result, such integrated activity of the neuronal group can change the excitation
threshold and discharge frequency of the studied neuron. It seems probable that correlated directed activation of the neuronal
groups represents a significant neurophysiological mechanism providing dynamic modifications of the RF parameters of visually
sensitive neurons in the course of processes of visual perception and identification of moving objects within the field of
vision. 相似文献
9.
D. K. Khachvankyan J. A. Kozak G. G. Grigoryan A. B. Sharanbekian T. K. Kipriyan B. A. Harutiunian-Kozak 《Neurophysiology》2008,40(2):105-114
In neurons of the extrastriate area 21a of the cat cortex, we examined the mode of initiation and peculiarities of inhibitory
components in responses of these units to visual stimulation. About 31% of the studied neurons generated complex responses
to mobile visual stimuli; the parameters of inhibitory components in these responses (location and duration) were different
and depended on the contrast, dimension, and shape of the visual stimuli presented. We compared in detail the stationary spatial
organization of receptive fields (RFs) and parameters of neuronal responses to presentation of moving stimuli in order to
estimate the correlation between static and dynamic characteristics of the activity generated by the studied neurons. Our
experiments showed that in most cases the neurons possessing identical homogeneous static characteristics of the RFs with
off, on-off, and on responses could demonstrate quite different patterns of responses to moving stimuli, which differed from each other both
in localization of inhibitory zones and discharge centers within the RFs and in time parameters of the components of these
responses. The obtained data allow us to hypothesize that the dynamic characteristics of visually sensitive neurons in the
extrastriate associative cortical regions are formed due to complex processes of spatial interaction between their “classic”
RFs and the surrounding visual space.
Neirofiziologiya/Neurophysiology, Vol. 40, No. 2, pp. 119–129, March–April, 2008. 相似文献
10.
D. K. Khachvankyan A. B. Sharambekyan G. G. Grigoryan A. G. Harutiunian J. A. Kozak S. A. Aramyan B. A. Harutiunian-Kozak 《Neurophysiology》2006,38(1):53-62
We examined responses of neurons of the field 21b of the cat brain cortex to presentation of moving visual stimuli of different
forms. Characteristics of the responses of about 54% of the studied neurons showed that in these cases configurations of the
contours of moving stimuli were to a certain extent discriminated. Most neurons selectively reacting to changes in the form
of the stimulus were dark-sensitive units (they generated optimum responses to presentation of dark visual stimuli on the
light background). Detailed examination of the spatial infrastructure of receptive fields (RFs) of the neurons and comparison
of this structure with the selectivity of neuronal responses showed that there is no significant correlation between static
organization of the RF and responses of the neuron to the movements of stimuli of different forms. We hypothesize that the
dynamic infrastructure of the RF and the combined activity of functional groups of neurons, whose RFs spatially overlap the
RF of the neuron under study, play a definite role in the mechanisms responsible for neuronal discrimination of the form of
the visual stimulus.
Neirofiziologiya/Neurophysiology, Vol. 38, No. 1, pp. 61–71, January–February, 2006. 相似文献