T Pracki

Daytime Acute Non-Visual Alerting Response in Brain Activity Occurs as a Result of Short- and Long-Wavelengths of Light

Very recent preliminary findings concerning the alerting capacities of light stimulus with long-wavelengths suggest the existence of neural pathways other than melatonin suppression that trigger the nonvisual response. Though the nonvisual effects of light during the daytime have not been investigated thoroughly, they are definitely worth investigating. The purpose of the present study is to enrich existing evidence by describing how quantitative electroencephalography (EEG) signal analysis can give insight into the measurement of the acute nonvisual response observed in brain states generated during daytime exposure to light (when melatonin secretion is negligible). EEG changes were assessed in 19 subjects during the daytime while being exposed to both short- (blue, 72 &mgr;W/cm2) and long-wavelength (red, 18 &mgr;W/cm2) radiation. We showed that artificial light stimulus as low as 40 lux decreases the synchronization in the upper theta, lower alpha, and upper alpha EEG activity spectrum. The direction of change was consistent with an increased level of alertness. We can conclude that EEG analysis is an indicator of the acute nonvisual response to daytime light. Surprisingly, the response was more spread over the scalp during exposure to red light than to blue light. According to our study, the response to long-wavelength stimulus that inhibits sleepiness, thereby inducing alertness, also takes place at the bright part of the 24-hr day when human beings are naturally predisposed to be exposed to a high level of sunlight: between 12 and 4 PM. The absorption spectrum of the nonvisual system seems to have different characteristics than was previously suspected: it is not dominated by the short-wavelengths, but involves long-wavelengths. Since we observed the predominance of the red-light alerting effect over the blue-light in this experiment, we conclude that more than one mechanism, beyond the melatonin pathway, must be involved.

MEASURING THE CHRONOTYPE IN POLISH POPULATION

Chronotype is an attribute connected with an individual, preferred pattern of circadian activity on the continuum of morningness-eveningness. It mirrors the inter-individual differences in the course of circadian rhythms [1, 2]. The studies indicate its connections with sleep-wake cycle, i.e.: time of sleep onset, wake up time and duration of sleep [3, 4]. Two methods of describing human chronotypes are considered in this paper: a subjective – questionnaire method and an objective method – actigraphy that measures the gross motor activity. The aim of the study was to assess the relation between results of Polish adaptation of Horne and Ostberg Morningness-Eveningness Questionnaire [5] and circadian activity measured with actigraphs in order to compare and evaluate the usefulness of both methods in chronotype related studies. Also, the purpose was to assess the relation between chronotype and socio-demographic factors such as sex, age and education in Polish population. The research group included 150 healthy volunteers of genders, 75 women and 75 men. The age of the respondents fell between 19 and 60 years old (34.25±12.13 EX±SD). The obtained results confirmed the usefulness of actigraphy in chronotype related studies. Also they confirmed modulation of chronotype with age and revealed differences in circadian activity between men and women.

The Objective Measurement of Movement vs the Intensification of ADHD Symptoms in Assessment of Parents and Doctors

The purpose of this work was the objective actigraphic evaluation of movement at children with ADHD (Attention Deficit Hyperactivity Disorder) in relation to the evaluation of symptom intensification according to their parents (ADHD-RS IV) and a medical qualification to a subtype of ADHD (DSM IV TR). The motor activity of a child was evaluated by means of an actigraph - Actiwatch 4 produced by Cambridge Neurotechnology Ltd. The investigated group consisted of 37 children (32 boys, 5 girls). Results: there were no differences in the activity between the group of children with recognized ADHD combined subtype and the group of children with recognized ADHD predominantly inattentive subtype observed. More serious attention disorders occur in case of children, who in later hours of the day have the maximum activity intensity. The scores of items evaluating the hyperactivity and impulsiveness did not correlate with the results of activity measurement. The results of actigraphic measurement did not correlate with the evaluation of the activity intensification according to parents.