The right-side perceptual bias in aging determined in a laboratory setting and during a virtual driving task.

Spatial perceptual rightward bias which was originally described in Dichotic Listening studies seems to be a general phenomenon. This bias is age dependent, being evident in children with developing executive functions, and emerging again at older age as a function of aging and the declining executive functions. In the two studies presented here we compared the performance of young and elderly adults in spatial divided attention tasks with auditory and visual stimuli when the stimulus detection performance was measured in separate sessions in a laboratory setting (Study I), to performance when the same types of stimuli were mixed with a task in which the subject's primary objective was to drive a car in a virtual environment (virtual reality; Study II). The aim was to see if the perceptual bias could be detected and also to look at how it would differ in these two situations. 90 right-handed subjects (50 young and 40 elderly) participated in Study I and 84 subjects (64 young and 20 elderly) participated in Study II. Study I showed the rightward bias to be more evident in the elderly subjects in both modalities and in more demanding tasks. Study II revealed that in the triple task the spatial perceptual bias was evident in both modalities for the elderly participants when the conditions were more demanding. An interesting finding concerning the right-side perceptual bias was the simultaneous occurrence of left-side driving errors, i.e. crossing the lane border to the left especially by the elderly. Both of these biases may reflect the asymmetries of the attention-related neuronal networks.

Visual rightward spatial bias varies as a function of age.

Age-related changes in visual spatial biases in children, young adults, and older adults were studied with unilateral and bilateral stimulus conditions in fast-paced linguistic and non-linguistic attention tasks. Only rightward spatial biases were observed. The incidence of the biases changed as a function of age: in childhood and in old age the rightward spatial biases were more common than in young adulthood. The present rightward spatial biases were similar to those observed in the corresponding auditory spatial linguistic and non-linguistic attention tests (Takio, Koivisto, Laukka, & Hämäläinen, 2011) and in the dichotic listening forced-attention task (Takio et al., 2009). We suggest that the multimodal rightward spatial bias observed under intensive attentional load is related to a right hemispace preference and modulated by age-dependent changes in executive functions.

Modification of dichotic listening (DL) performance by musico-linguistic abilities and age.

To increase our understanding of the phonemic processing skills of musical and non-musical subjects, the Dichotic Listening task was performed in children and adults with varying degrees of musical aptitude. The roles of maturation and musical training were also investigated. The results showed superior left ear monitoring skills among the adults who practised music regularly. This may indicate altered hemispheric functioning. Other musically talented subjects did not have the ability to control left ear functioning in an equal manner, for instance, the performance of musical children and their non-musical controls in the forced-left / left ear condition did not differ. Thus, regular music practice may have a modulatory effect on the brain's linguistic organization and therefore, the beneficial effects of music on other cognitive skills should not be underestimated.

Blind individuals show enhanced perceptual and attentional sensitivity for identification of speech sounds.

We report on enhanced processing of speech sounds in congenitally and early blind individuals compared with normally seeing individuals. Two different consonant-vowel (CV) syllables were presented via headphones on each presentation. We used a dichotic listening (DL) procedure with pairwise presentations of CV syllables. The typical finding in this paradigm is a right ear advantage, indicating better processing of the CV-syllable stimuli in the left hemisphere. The dichotic listening procedure involved three different conditions, with instructions to pay attention to the right ear stimulus, the left ear stimulus or no specific instruction. The participants were 14 congenitally or early blind Finnish-speaking individuals that were compared with 129 normal seeing Finnish-speaking individuals. The blind participants reported overall significantly more correct syllables than seeing control subjects. When instructed to pay attention to the left ear stimulus and only report from the attended channel, they were again significantly better than the seeing control subjects. These findings indicate effects of hemispheric reorganization in blind individuals at both the sensory and cognitive levels of information processing in the auditory sensory modality.

The influence of executive functions on spatial biases varies during the lifespan.

Many perceptual processes, such as language or face perception, are asymmetrically organised in the hemispheres already in childhood. These asymmetries induce behaviourally observable spatial biases in which the observer perceives stimuli in one of the hemispaces more efficiently or more frequently than in the other one. Another source for spatial biases is spatial attention which is also asymmetrically organised in the hemispheres. The bias induced by attention is directed towards the right side, which is clearly demonstrated by patients with neglect but also in lesser degree by healthy observers in cognitively loading situations. Recent findings indicate that children and older adults show stronger spatial biases than young adults. We discuss how the development of executive functions might contribute to the manifestation of spatial biases during the lifespan. We present a model in which the interaction between the asymmetrical perceptual processes, the age-related development of the lateralised spatial attention and the development of the executive functions influence spatial perceptual performance and in which the development and decline of the executive processes during the lifespan modify the spatial biases.

Auditory rightward spatial bias varies as a function of age.

Age-related changes in auditory spatial perception of linguistic and non-linguistic stimuli in participants between 5 and 79 years of age were studied. The results show that the strength of the rightward perceptual bias in linguistic bilateral (dichotic) stimulus condition changes as a function of age. In childhood and old age also other rightward spatial biases were observed in linguistic as well as in non-linguistic stimulus conditions. We propose that the auditory rightward spatial biases are not specific to the language and are probably modulated by the early development and late decline of the executive functions.

The effect of age on attentional modulation in Dichotic listening.

The right-ear advantage (REA) in Dichotic listening (DL) reflects stimulus-driven bottom-up asymmetry in speech processing. The REA can be modified by top-down attentional control. We investigated attentional control in DL task as a function of age. A total of 186 participants between the ages of 5 and 79 years were tested. The youngest children demonstrated a REA that was not modified by attention, suggesting that bottom-up functional asymmetry was present. The 10-11-year-olds began to show ability to voluntarily modify DL, but only young adults were fully capable of doing so. In 59-79-year-olds, this top-down attentional control was lost again.

Pulsed and continuous wave mobile phone exposure over left versus right hemisphere: effects on human cognitive function.

The possible effects of continuous wave (CW) and pulse modulated (PM) electromagnetic field (EMF) on human cognition was studied in 36 healthy male subjects. They performed cognitive tasks while exposed to CW, PM, and sham EMF. The subjects performed the same tasks twice during each session; once with left-sided and once with right-sided exposure. The EMF conditions were spread across three testing sessions, each session separated by 1 week. The exposed hemisphere, EMF condition, and test order were counterbalanced over all subjects. We employed a double-blind design: both the subject and the experimenter were unaware of the EMF condition. The EMF was created with a signal generator connected via amplifier to a dummy phone antenna, creating a power output distribution similar to the original commercial mobile phone. The EMF had either a continuous power output of 0.25 W (CW) or pulsed power output with a mean of 0.25 W. An additional control group of 16 healthy male volunteers performed the same tasks without any exposure equipment to see if mere presence of the equipment could have affected the subjects' performance. No effects were found between the different EMF conditions, separate hemisphere exposures, or between the control and experimental group. In conclusion, the current results indicate that normal mobile phones have no discernible effect on human cognitive function as measured by behavioral tests.