Sensory Mechanisms in Early Orientation Discrimination in a Model of Visual Working Memory
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Sensory Mechanisms in Early Orientation Discrimination in a Model of Visual Working Memory E. S. Mikhailova, N. Yu. Gerasimenko, and A. V. Slavutskaya
UDC 612.821 + 612.014.423 + 843.7
Translated from Zhurnal Vysshei Nervnoi Deyatel’nosti imeni I. P. Pavlova, Vol. 69, No. 5, pp. 577–589, September–October, 2019. Original article submitted June 22, 2018. Revised version received November 1, 2018. Accepted November 20, 2018. An experimental model of working memory was used to study the time characteristics and topography of evoked electrical brain activity in early discrimination between two sequential orientations. Studies in 33 subjects analyzed the amplitudes of components P100 and N150 of sensory event-related potentials (ERP) in the occipital, parietal, and temporal areas of the cortex on solution of a task consisting of comparing two sequentially presented visual stimuli. Stimuli in experimental sessions were square grids with lines in different orientations; stimuli in control sessions were spatial patterns consisting of three circles with different positions on the screen. The neurophysiological correlate of the detection of discordance between the current orientation and the orientation held in memory was an increase in the amplitude of the early wave complex P100/N150 in the occipital cortex, which was combined with a less clear increase in the P100 in the temporal-parietal area. Discordance of patterns was accompanied by an increase in the amplitude of the later ERP component N150 in the visual areas, without clear zonal specificity in this effect. Thus, these studies demonstrated the specific involvement of the early visual cortex in the processing information on comparison of the current sensory visual sign – line orientation – with that stored in memory. The discordance signal, formed in the occipital area, may underlie the early detection of changes in basic visual characteristics. Keywords: humans, vision, orientation, working memory, event-related potentials, visual cortex.
Orientational characteristics constitute an important descriptive attribute of objects in the visual world, and their retention is an obligatory component of memory of complex objects and scenes. Retention of orientational properties in short-term memory is important in supporting the mechanisms maintaining stable visual representations in natural processes unexpectedly interrupting the sensory input, such as saccadic eye movements, fixation, and occlusion [Luck and Vogel, 1997; Hollingworth et al., 2008]. Data from psychophysical studies of working memory for orientation led to proposal of the “low-level perceptual memory” model [Magnussen, 2000, 2009]. According to this model, formation of representations of elementary visual signs, their storage, and their early implicit discrimina-
tion are all operations carried out at the level of visual sensory areas above V1, which corresponds to the presemantic level of signal processing. The importance of the early perceptual component in forming memory traces is well illustrated by
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