اقدامات برانگیخته بالقوه و رفتاری از حواس پرتی در کودکان 5 ساله نارس و متولد

Abstract Executive and attention dysfunctions are common in very preterm children. We studied their involuntary attention process by using behavioral measurements and auditory event-related potentials (AERP) with a distraction paradigm at age five years. The active task was to distinguish between two animal sounds. As an irrelevant feature the sounds were presented from frequent (standard) or infrequent (deviant, 11%) direction from two loudspeakers. Of the 28 preterm children, only 75% could accomplish the task, whereas all full-term children (n = 15) could. When distinguishing the animal sounds, the reaction times were longer to the sounds from the deviant than from the standard direction in both groups, indicating involuntary distraction. The hit rates for the sounds from standard and deviant directions were similar in both groups. AERP amplitudes in the P1 interval and in the P3a interval elicited by standard and deviant stimuli were smaller in the preterm than in the control children. Deviants elicited P3a (indicating attentional orienting) and reorienting negativity (indicating attentional reorienting after distraction) in both groups. Comparable involuntary attentional orienting, distraction, and reorienting suggest similar maturation processes in 5-year-old preterm and full-term children. However, smaller AERP amplitudes in P1 and P3a interval suggest altered processing of auditory stimuli in those born preterm. As one-fourth of the preterm children could not accomplish the paradigm, less demanding paradigms should be used in studying children with increased distractibility.

Introduction Prematurity is a major risk factor for postnatal brain damage causing adverse neurodevelopmental outcome (Woodward et al., 2006). Preterm children are at an increased risk for attention executive dysfunction; they have difficulties in planning, self-regulation, accuracy, inhibition, and motor persistence (Marlow et al., 2007). Apart from neuropsychological tests, few tools exist to assess attention. Active-task auditory event-related potentials (AERPs) can be applied for studying involuntary and voluntary attention and distractibility (Escera et al., 2000). In an AERP, the exogenous positive (P) and negative (N) deflections are determined by the physical characteristics of the presented stimuli. Exogenous AERPs in children alter during the auditory tract maturation. AERPs of infants are characterized with a large broad positivity at 200–300 ms (P2) followed by a late negativity at 300–600 ms (N2) (Kurtzberg et al., 1984). AERP waveforms change in infancy first at midline according to the maturation of the primary auditory cortex, and later at temporal electrodes according to the secondary auditory cortical areas (Kurtzberg et al., 1984). The endogenous components reflect the cognitive processing of the stimulus paradigm that is related to learning, memory, and discrimination ability (Näätänen, 1992). Such endogenous deflections are P3a, elicited by an automatic attention shift (Escera et al., 1998), mismatch negativity, MMN, defined as a change detection process (Näätänen, 1992), and late negative response, RON, i.e. a response when reorienting from task-irrelevant sounds to task-relevant ones (Berti and Schröger, 2001). In children, AERPs consist of P1 (at 85–120 ms), N2 (at 200–240 ms), and N4 (at about 450 ms) when interstimulus interval less than 1 s is used (Ceponiene et al., 1998 and Korpilahti & Lang, 1994). P1, large in amplitude (Cunningham et al., 2000 and Kushnerenko et al., 2002), is generated in Heschl's gyrus and suggested to reflect primary auditory processing (Godey et al., 2001 and Liegeois-Chauvel et al., 1994). It decreases in latency and amplitude up to the age of 20 years, reaching the adult latency of approximately 50 ms (Ponton et al., 2002 and Sharma et al., 1997). At the age of five years, the first typical negative (N1) deflection in an adult AERP is not detectable (Ponton et al., 2002), whereas the negative peak N2 at about 250 ms is large, and diminishes thereafter (Ceponiene et al., 2001) In children, MMN latency is about 100–200 ms, and includes both temporal and frontal components (Gomot et al., 2000). Attention and distractibility are age-dependent (Wetzel et al., 2006) and related to maturation of the prefrontal cortex (Casey et al., 2005). Distractibility can be evaluated by behavioral and AERP responses to so-called distraction paradigms, in which the processing of task-relevant information is disturbed by task-irrelevant deviant or novel information (Escera et al., 2000). Such deviant or novel information impairs behavioral performance (reaction times and hit rates) in the primary task and elicits P3a, an indicator of involuntary attention shift from the primary task towards the distracting information, that is sometimes followed by reorienting negativity (RON), indicating the reorienting of attention to the primary task. P3a occurs around 300 ms after the onset of the deviant (Escera et al., 1998) generated in the auditory cortex with bilateral association regions prefrontally and temporoparietally (Escera et al., 2000). The frontal RON reflects reorienting and refocusing from task-irrelevant sound features to the primary task (Schröger and Wolff, 1998). Both P3a and a negativity resembling RON have been observable in school-aged children (Gumenyuk et al., 2005, Wetzel et al., 2004 and Wetzel et al., 2006). Previously, in visual ERP study, preterm children with attention deficit and hyperactivity disorder (ADHD) had the smallest P1 and P3, and those preterm without ADHD the second smallest P1 and P3 compared to full-term children with and without ADHD (Potgieter et al., 2003). In a passive oddball paradigm, we have found a smaller P1 in preterm children than in controls, and their amplitude correlated positively with verbal performance (Mikkola et al., 2007). Thus, preterm children seem to process sounds somewhat different from the full-term. We hypothesized that the behavioral responses and AERPs to the distraction paradigm in preschool-aged preterm children differ from those of full-term controls. Our aim was to investigate whether the auditory distraction paradigm that has been successfully applied to basic and clinical research with different populations of differing ages (Berti & Schröger, 2001, Roeber et al., 2003, Schröger & Wolff, 1998 and Schröger et al., 2000) including children (Wetzel et al., 2004 and Wetzel et al., 2006) can be used for assessing attention in 5-year-old preterm children.

5. Conclusion Attentional AERP components were recognizable in the control children and those preterm children who successfully completed the task. Differences occurred between groups in basic auditory processing, but responses reflecting involuntary attention shift and distraction seem to be similar in those born preterm and full-term. As the task was too challenging for one-fourth of the preterm cohort, further studies should address whether a simpler paradigm or later age would be more applicable in assessing distractibility in children at high risk for perinatal injury sequelae.