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BackgroundPast research indicates that when younger adults are engaged in a visual working memory task, they are less distracted by novel auditory stimuli than when engaged in a visual task that does not require working memory. The current study aimed to determine whether working memory affords the same protection to older adults.MethodWe examined behavioral and EEG responses in 16 younger and 16 older adults to distractor sounds when the listeners performed two visual tasks; one that required working memory (W1) and the other that did not (W0). Auditory distractors were presented in an oddball paradigm, participants were exposed to either standard tones (600 Hz: 80%) or various novel environmental sounds (20%).ResultsIt was found that: 1) when presented with novel vs standard sounds, older adults had faster correct response times in the W1 visual task than in the W0 task, indicating that they were less distracted by the novel sound; there was no difference in error rates. Younger adults did not show a task effect for correct response times but made slightly more errors when a novel sound was presented in the W1 task compared to the W0 task. 2) In older adults (but not the younger adults), the amplitude of N1 was smaller in the W1 condition compared to the W0 condition. 3) The working memory manipulation had no effect on MMN amplitude in older adults. 4) For the W1 compared to W0 task, the amplitude of P3a was attenuated for the older adults but not for the younger adults.ConclusionsThese results suggest that during the working memory manipulation older adults were able to engage working memory to reduce the processing of task-irrelevant sounds.

Background Deficits in emotional prosody processing have been observed in bipolar disorder (BD). While recent neural studies have explored impaired processing of facial expressions, little is known about deficits in emotional speech processing, or the specific stages of processing at which they occur. This study examined if pre-attentive detection and attention to emotional speech is impaired in BD, relative to healthy individuals. Methods The EEG data was collected from 14 individuals with BD and 14 healthy control (HC) participants while the auditory stimuli was presented via a passive three-stimulus oddball sequence which included emotionally (neutral, happy, sad) spoken syllables and acoustically matched nonvocal tones. Event-related potentials (ERPs) were evaluated in terms of Mismatch Negativity (MMN) and P3a (event-related potentials signals). Results Individuals with BD showed normal MMN amplitude, but significantly delayed MMN latency and reduced P3a amplitude in response to the emotional syllables compared to HC. Limitations Small sample size, lack of control of psychopharmacological intervention and no inclusion of an affective prosody-labelling task. Conclusions The finding that changes in emotional speech prosody in the pre-attentive stages of processing (MMN) were unimpaired in individuals with BD; while automatic orientation towards emotionally salient speech (P3a) was reduced compared to HC, suggests that vocal emotional cues may not be recognised as salient by individuals with BD, resulting in fewer attentional resources allocation to further processing. This may lead to poorer integration of auditory emotional cues and other sensory information and negatively impact interpersonal and psychosocial functions.

Adding frequency modulations (FM) cues to vocoded (AM) speech aids speech recognition for younger listeners. However, this may not be true for older listeners since they have poorer FM detection thresholds. We measured FM detection thresholds of young and older adults; and in a sentence context examined whether adding FM cues to vocoded speech would assist older adults. Young and old participants were presented vocoded sentences in quiet and multitalker-babble with/without FM cues. Older adults had elevated FM detection thresholds but received the same-size FM benefit as younger adults, showing that they have the capacity to benefit from FM speech cues.

Adolescence is a time of great change in the brain in terms of structure and function. It is possible to track the development of neural function across adolescence using auditory event-related potentials (ERPs). We measured passive auditory ERPs to pure tones and consonant–vowel (CV) syllables in 90 children and adolescents aged 10–18 years, as well as 10 adults. With one exception, the pattern of results were the same for tones and speech: Across adolescence, the P1 ERP peak decreased in size and latency, the N1 increased in size and decreased in latency, the P2 remained constant in size, and the N2 decreased in size but remained stable across adolescence. The exception was P2 latency, which increased for speech but remained stable for tones. Interesting step-like changes were observed for N1 latency for both tones and speech stimuli in 15- to 16-year-olds. These may stem from rapid hormonal changes that affect neurotransmitter activity of the ERP-generating neurons.

A recent meta-analysis emphasises that meditation can improve attention in healthy adults (Sedlmeier et al., 2012). The findings of a study by Cahn and Polich (2009) suggests that there is an effect of a meditative state on three event-related potential (ERP) brain markers of low-level auditory attention in expert meditators: the N1, the P2, and the P3a. The current study built on these findings by examining the trait and state effects of meditation on the passive auditory mismatch negativity (MMN), N1, and P2 ERPs. We found that the MMN was significantly larger in meditators than non-meditators regardless of whether they were meditating or not (a trait effect), and that the N1 was significantly attenuated during meditation in non-meditators but not meditators (an interaction between trait and state). These outcomes suggest that low-level attention is superior in long-term meditators in general. In contrast, low-level attention is reduced in non-meditators when they are asked to meditate for the first time, possibly due to cognitive overload.

Adolescence represents the period of transition from childhood to adulthood and is characterized by significant changes in brain structure and function. We studied changes in the functional visual processing in the brain across adolescence. Visual evoked potentials (VEPs) to three types of pattern reversal checkerboard stimuli were measured in 90 adolescents (10-18 years) and 10 adults. Across adolescence, the N75 and P100 VEP peaks decreased in size while the N135 peak increased slightly in size. The latency of VEP peaks showed no reliable change across adolescence. The results suggest that even very basic visual sensory function continues to develop throughout adolescence. The results indicate significant changes in visual parvocellular and magnocellular pathways across adolescence.

Adolescents experience significant changes in various physiological and psychological domains due to changes in their brain’s structure and function. A lot is known about structural changes in the brain across adolescence. However, less research has investigated changes in brain function during this period. In this study, we tracked the maturation of the auditory mismatch negativity (MMN) and P3a brain responses – both posited as neural indices of auditory discrimination – in 90 adolescents aged 10–18 years. We found that P3a mean amplitude and latency decreased significantly across adolescence, but there was no reliable change in the MMN. These results suggest that neural processes associated with passive auditory processing continue to develop well into adolescence.

The current study used event-related potentials (ERP) in combination with a variable viewing position paradigm (VVPP) to direct fixations to specific face parts (eyes or mouths) in upright or inverted whole faces. The N170 elicited by the VVPP was greater to faces than to non-face objects (wristwatches), and was delayed and enhanced in response to face inversion. A larger N170 response was elicited when the participants׳ fixation was directed to the eyes than when directed to the mouths of both upright and inverted faces, an effect that was also modulated by the spatial location of the face in the visual field. The N170 face inversion effect (upright minus inverted) was greater when fixations were directed to the mouth than when directed to the eyes, suggesting that the point of fixation within a face modulates brain potentials due to contributions from the features themselves, as well as their relative location in the visual field.

Electrical activity from the human brain can be recorded via electrodes on the scalp. It is important to reduce the impedance of each electrode to minimize unwanted noise in the recording. Electrode impedance can be improved by abrading the skin to remove dead skin cells. In this experiment, we tested if abrading the skin by combing the scalp leads to a significant reduction in electrode impedance. We compared the mean electrode impedance values of 20 subjects whose scalps were combed prior to electrode cap placement, with 20 subjects whose scalps were not combed. Combing significantly reduced the impedances at central, right, and left areas of the scalp. This finding supports the use of scalp combing to reduce the time and subject discomfort that can be associated with placing scalp electrodes. This is particularly important for experiments testing children.

Auditory selective attention enables task-relevant auditory events to be enhanced and irrelevant ones suppressed. In the present study we used a frequency tagging paradigm to investigate the effects of attention on auditory steady state responses (ASSR). The ASSR was elicited by simultaneously presenting two different streams of white noise, amplitude modulated at either 16 and 23.5 Hz or 32.5 and 40 Hz. The two different frequencies were presented to each ear and participants were instructed to selectively attend to one ear or the other (confirmed by behavioral evidence). The results revealed that modulation of ASSR by selective attention depended on the modulation frequencies used and whether the activation was contralateral or ipsilateral. Attention enhanced the ASSR for contralateral activation from either ear for 16 Hz and suppressed the ASSR for ipsilateral activation for 16 Hz and 23.5 Hz. For modulation frequencies of 32.5 or 40 Hz attention did not affect the ASSR. We propose that the pattern of enhancement and inhibition may be due to binaural suppressive effects on ipsilateral stimulation and the dominance of contralateral hemisphere during dichotic listening. In addition to the influence of cortical processing asymmetries, these results may also reflect a bias towards inhibitory ipsilateral and excitatory contralateral activation present at the level of inferior colliculus. That the effect of attention was clearest for the lower modulation frequencies suggests that such effects are likely mediated by cortical brain structures or by those in close proximity to cortex.