Brain activity dynamics in adults and children in attentional and motor control tasks Dmitry Dyachkov, Sergey Tamozhnikov, Evgeny Levin, Alexander Savostyanov State Research Institute of Physiology and Fundamental Medicine, Siberian Branch of Medical Sciences, Novosibirsk, Russian Federation Novosibirsk School of Psychology Address for correspondence: firstname.lastname@example.org; email@example.com The state of system of attention in the junior schoolchildren to a large degree determines their success in education. In addition, there is necessity of development of methods for diagnostics of attentional disorders in children. One of such methods is an analysis of event-related brain activity in conditions of discrimination between target and non-target stimuli (oddball paradigm, Naatanen, 1998). The aim of this study was to compare brain and behavioral reactions in the junior schoolchildren in condition of recognition of monophonic and polyphonic sound signals. Also, the reactions in conditions of Stop-signal paradigm (Logan et al., 1984; Savostyanov et al., 2009) were analyzed. Methods Results Participants: 57 children (6-8 years old, 35 boys) participated in experiments. All were schoolchildren in first class of elementary school in Novosibirsk, Russia. 31 of them received a learning program according to educational standard of Russian Federation (“ordinary class”). Another 25 children received an experimental learning program, elaborated by school psychologist V.V. Stepanova (“experimental class”). The parents of all children gave informed written consent prior to the experiment that satisfied the requirements of the human subject research ethics committee at the Institute of Physiology and Fundamental Medicine, Novosibirsk, Russia. Each child participated in two experimental session – in the beginning (autumn, September-November) and the end (spring, March-May) of educational year. Experimental procedures: Brain event-related potentials (ERPs) were recorded in auditory oddball paradigm when the target (20% of stimuli) or non-target (80%) sound stimuli were randomly presented to a child. Children were asked to press the button after presentation of a target signal and not react after non-target signal. Two variants of oddball test were separately presented to each child: 1) recognition of monophonic sounds: target signal – a sound with 1000 Hz frequency and non-target signal – a sound in 500 Hz; 2) recognition of polyphonic sounds: target signal — voice of cat ("meow“), non-target signal — voice of frog ("qua“). • Besides, all children participated in EEG records during execution of Stop-signal paradigm (SSP) [Logan et al., 1984] which was applied to investigate processes connected with activation and inhibition of motor reactions. It was designed in the form of the game. Children were asked to “feed” the animal (rabbit or tiger) which appears on the screen with appropriate food (carrots or meat) by pressing one of two buttons. In 15 out of 80 trials, target presentation was followed by a stop-signal, indicating that this time animal shouldn’t be fed, i.e. children had to refrain from a prepared motor response in this case. EEG/ERP Recording: • EEGs were recorded using 64-channels (EEG + VEOG) via Ag/AgCl electrodes. The EEG electrodes were placed on 63 head sites according to the extended International 10-10 system and referred to Cz with ground at FzA. The Quik-Cap128 NSL was used for electrode fixation. The signals were amplified using “Neuroscan” (USA) amplifiers, with 0.1-100 Hz analog bandpass filtering and digitized at 1000 Hz. • Behavioral data analysis: • Analysis of reaction speed in oddball test showed that in some of children several reactions were abnormally fast (sometimes less than 10 ms). We assumed, that these reactions were due to “chaotic” pressing of the button, i.e. without relation to stimuli. We estimated minimal reaction time necessary for task execution, using data from subgroup of children with not less than 90% of correct responses (9 children in whole group). The minimal latency of correct reaction was a little more than 200 ms in this subgroup, therefore we considered 200 ms as a threshold to suggest all faster reactions as been made “chaotically”. More or less reactions of this kind were obtained in most of children during monophonic condition, but they were almost absent in polyphonic condition. • In accordance with proportion of “chaotic” reactions children were divided into three groups: (1) “chaotic” with more than 30% of abnormally fast reactions, (2) “semichaotic” with 10 to 30% of such reactions and (3) “regular” with less than 10% of such reactions. Behavioral patterns and task-related brain activity in children from “chaotic”, “semichaotic” and “regular” groups: Percent of correct responses in the whole oddball test (left panel) and in the middle of this test (right panel) in groups with chaotic, semichaotic and regular reactions. Percents of pressing after non-target stimulus (left) and missed pressing after target stimulus (right) in oddball test in groups with chaotic, semichaotic and regular reactions. Total score (left) and percent of correctly chosen reactions to target stimulus (right)in the “Stop-signal” test in groups with chaotic, semichaotic and regular reactions in monophonic oddball test. Cortical topography of ERPs in 300-400 ms time interval in monophonic oddball test in the children from groups with chaotic, semichaotic and regular reactions. Cortical topography of ERPs in 300-400 ms time interval in polyphonic oddball test (sounds “meow” and “qua”) in the children from groups with chaotic, semichaotic and regular reactions. Average latency of correct reactions (left) and its standard deviation (right) in oddball test in groups with chaotic, semichaotic and regular reactions. Figures used in the Stop-signal game. Images of food were continuously present on the bottom of the screen according to the side of appropriate button, while images of animals and stop-signal were presented transiently. Conclusions Changes in behavioral patterns after one educational year: Individual differences in work of system of attention were found in children by analysis of the behavioral data from oddball test with monophonic auditory stimulation. Both oddball and SSP tests showed between-group behavioral differences even though groups were formed using response patterns only from oddball test. Between-group differences in ERPs were obtained both at monophonic, and at polyphonic stimulation. Children with "chaotic" behavioral strategy of behavior are characterized by decrease in amplitude of P300 peak in reply to target stimulus in comparison with children who have shown "regular" behavioral strategy. After one year of education significant decrease in number of "chaotical” responses was obtained. Different approaches to education showed significant differences in changes of behavioral reactions, which are related with attention and motor control systems. The change of behavior in oddball task during one educational year. Chi2=15.5, df=2, p=0.0004 The dependency between reactions in odd-ball and SSP in different groups during firs and second testing. Changes in average percent of chaotic reactions in experimental and ordinary classes.