Enhanced neural mechanisms of set shifting in musically trained adolescents and young adults: converging fMRI, EEG, and behavioral evidence.

Musically trained individuals have been found to outperform untrained peers in various tasks for executive functions. Here, we present longitudinal behavioral results and cross-sectional, event-related potential (ERP), and fMRI results on the maturation of executive functions in musically trained and untrained children and adolescents. The results indicate that in school-age, the musically trained children performed faster in a test for set shifting, but by late adolescence, these group differences had virtually disappeared. However, in the fMRI experiment, the musically trained adolescents showed less activity in frontal, parietal, and occipital areas of the dorsal attention network and the cerebellum during the set-shifting task than untrained peers. Also, the P3b responses of musically trained participants to incongruent target stimuli in a task for set shifting showed a more posterior scalp distribution than control group participants' responses. Together these results suggest that the musician advantage in executive functions is more pronounced at an earlier age than in late adolescence. However, it is still reflected as more efficient recruitment of neural resources in set-shifting tasks, and distinct scalp topography of ERPs related to updating and working memory after childhood.

Informal musical activities are linked to auditory discrimination and attention in 2-3-year-old children: an event-related potential study.

The relation between informal musical activities at home and electrophysiological indices of neural auditory change detection was investigated in 2-3-year-old children. Auditory event-related potentials were recorded in a multi-feature paradigm that included frequency, duration, intensity, direction, gap deviants and attention-catching novel sounds. Correlations were calculated between these responses and the amount of musical activity at home (i.e. musical play by the child and parental singing) reported by the parents. A higher overall amount of informal musical activity was associated with larger P3as elicited by the gap and duration deviants, and smaller late discriminative negativity responses elicited by all deviant types. Furthermore, more musical activities were linked to smaller P3as elicited by the novel sounds, whereas more paternal singing was associated with smaller reorienting negativity responses to these sounds. These results imply heightened sensitivity to temporal acoustic changes, more mature auditory change detection, and less distractibility in children with more informal musical activities in their home environment. Our results highlight the significance of informal musical experiences in enhancing the development of highly important auditory abilities in early childhood.

Neural correlates of music recognition in Down syndrome.

The brain mechanisms that subserve music recognition remain unclear despite increasing interest in this process. Here we report the results of a magnetoencephalography experiment to determine the temporal dynamics and spatial distribution of brain regions activated during listening to a familiar and unfamiliar instrumental melody in control adults and adults with Down syndrome (DS). In the control group, listening to the familiar melody relative to the unfamiliar melody, revealed early and significant activations in the left primary auditory cortex, followed by activity in the limbic and sensory-motor regions and finally, activation in the motor related areas. In the DS group, listening to the familiar melody relative to the unfamiliar melody revealed increased significant activations in only three regions. Activity began in the left primary auditory cortex and the superior temporal gyrus and was followed by enhanced activity in the right precentral gyrus. These data suggest that familiar music is associated with auditory-motor coupling but does not activate brain areas involved in emotional processing in DS. These findings reveal new insights on the neural basis of music perception in DS as well as the temporal course of neural activity in control adults.

The perception of invariant speech features in children with autism.

We investigated whether the good pitch-discrimination abilities reported in individuals with autism have adverse effects on their speech perception by compromising their ability to extract invariant phonetic features from speech input. The MMN, a brain response reflecting sound-discrimination processes, was recorded from children with autism and their controls for phoneme-category and pitch changes in speech stimuli under two different conditions: (a) when all the other features of the standard and deviant stimuli were kept constant, and (b) when constant variation with respect to an irrelevant feature was introduced to the standard and deviant stimuli. Children with autism had enhanced MMNs for pitch changes in both conditions, as well as for phoneme-category changes in the constant-feature condition. However, when the phoneme-category changes occurred in phonemes having pitch variation, the MMN enhancement was abolished in autistic children. This suggests that children with autism lose their advantage in phoneme discrimination when the context of the stimuli is speech-like and requires abstracting invariant speech features from varying input.

Within- and between-session replicability of cognitive brain processes: An MEG study with an N-back task.

In the vast majority of electrophysiological studies on cognition, participants are only measured once during a single experimental session. The dearth of studies on test-retest reliability in magnetoencephalography (MEG) within and across experimental sessions is a preventing factor for longitudinal designs, imaging genetics studies, and clinical applications. From the recorded signals, it is not straightforward to draw robust and steady indices of brain activity that could directly be used in exploring behavioral effects or genetic associations. To study the variations in markers associated with cognitive functions, we extracted three event-related field (ERF) features from time-locked global field power (GFP) epochs using MEG while participants were performing a numerical N-back task in four consecutive measurements conducted during two different days separated by two weeks. We demonstrate that the latency of the M170, a neural correlate associated with cognitive functions such as working memory, was a stable parameter and did not show significant variations over time. In addition, the M170 peak amplitude and the mean amplitude of late positive component (LPP) also expressed moderate-to-strong reliability across multiple measures over time over many sensor spaces and between participants. The M170 amplitude varied more significantly between the measurements in some conditions but showed consistency over the participants over time. In addition we demonstrated significant correlation with the M170 and LPP parameters and cognitive load. The results are in line with the literature showing less within-subject fluctuation for the latency parameters and more consistency in between-subject comparisons for amplitude based features. The within-subject consistency was apparent also with longer delays between the measurements. We suggest that with a few limitations the ERF features show sufficient reliability and stability for longitudinal research designs and clinical applications for cognitive functions in single as well as cross-subject designs.

Middle latency response correlates of single and double deviant stimuli in a multi-feature paradigm.

OBJECTIVE: This study aimed to test single and double deviance-related modulations of the middle latency response (MLR) and the applicability of the optimum-2 multi-feature paradigm. METHODS: The MLR and the MMN to frequency, intensity and double-feature deviants of an optimum-2 multi-feature paradigm and the MMN to double-feature deviants of an oddball paradigm were recorded in young adults. RESULTS: Double deviants elicited significant enhancements of the Nb and Pb MLR waves compared with the waves elicited by standard stimuli. These enhancements equalled approximately the sum of the numerical amplitude differences elicited by the single deviants. In contrast, the MMN to double deviants did not show such additivity. MMNs elicited by double deviants of the multi-feature and the oddball paradigm showed no significant difference in amplitude or latency. CONCLUSIONS: The optimum-2 multi-feature paradigm is suitable for recording double deviance-related modulations of the MLR. Interspersed intensity and frequency deviants in the standard trace of the optimum-2 condition multi-feature paradigm did not weaken the double MMN. SIGNIFICANCE: The optimum-2 multi-feature paradigm could be especially beneficial for clinical studies on early deviance-related modulations in the MLR, due to its optimized utilization of the recording time.

Event-related brain responses while listening to entire pieces of music.

Brain responses to discrete short sounds have been studied intensively using the event-related potential (ERP) method, in which the electroencephalogram (EEG) signal is divided into epochs time-locked to stimuli of interest. Here we introduce and apply a novel technique which enables one to isolate ERPs in human elicited by continuous music. The ERPs were recorded during listening to a Tango Nuevo piece, a deep techno track and an acoustic lullaby. Acoustic features related to timbre, harmony, and dynamics of the audio signal were computationally extracted from the musical pieces. Negative deflation occurring around 100 milliseconds after the stimulus onset (N100) and positive deflation occurring around 200 milliseconds after the stimulus onset (P200) ERP responses to peak changes in the acoustic features were distinguishable and were often largest for Tango Nuevo. In addition to large changes in these musical features, long phases of low values that precede a rapid increase - and that we will call Preceding Low-Feature Phases - followed by a rapid increase enhanced the amplitudes of N100 and P200 responses. These ERP responses resembled those to simpler sounds, making it possible to utilize the tradition of ERP research with naturalistic paradigms.

Behavioral and electrophysiological indicators of auditory distractibility in children with ADHD and comorbid ODD.

Involuntary switching of attention to distracting sounds was studied by measuring effects of these events on auditory discrimination performance and event-related brain potentials (ERPs) in 6-11-year-old boys with Attention Deficit-Hyperactivity Disorder (ADHD) and comorbid Oppositional Defiant Disorder (ODD) and in age-matched controls. The children were instructed to differentiate between two animal calls by pressing one response button, for example, to a dog bark and another button to a cat mew. These task-relevant sounds were presented from one of two loudspeakers in front of the child, and there were occasional task-irrelevant changes in the sound location, that is, the loudspeaker. In addition, novel sounds (e.g., a sound of hammer, rain, or car horn) unrelated to the task were presented from a loudspeaker behind the child. The percentage of correct responses was lower for target sounds preceded by a novel sound than for targets not preceded by such sound in the ADHD group, but not in the control group. In both groups, a biphasic positive P3a response was observed in ERPs to the novel sounds. The later part of the P3a appeared to continue longer over the frontal scalp areas in the ADHD group than in the controls presumably because a reorienting negativity (RON) ERP response following the P3a was smaller in the ADHD group than in the control group. This suggests that the children with ADHD had problems in reorienting their attention to the current task after a distracting novel sound leading to deterioration of performance in this task. The present study also indicates that children with ADHD and comorbid ODD show same kind of distractibility as found in previous studies for children with ADHD without systematic comorbid ODD.

The fast detection of rare auditory feature conjunctions in the human brain as revealed by cortical gamma-band electroencephalogram.

Natural environments typically contain temporal scatters of sounds emitted from multiple sources. The sounds may often physically stand out from one another in their conjoined rather than simple features. This poses a particular challenge for the brain to detect which of these sounds are rare and, therefore, potentially important for survival. We recorded gamma-band (32-40 Hz) electroencephalographic (EEG) oscillations from the scalp of adult humans who passively listened to a repeated tone carrying frequent and rare conjunctions of its frequency and intensity. EEG oscillations that this tone induced, rather than evoked, differed in amplitude between the two conjunction types within the 56-ms analysis window from tone onset. Our finding suggests that, perhaps with the support of its non-phase-locked synchrony in the gamma band, the human brain is able to detect rare sounds as feature conjunctions very rapidly.

Electrophysiological evidence of enhanced distractibility in ADHD children.

Abnormal involuntary attention leading to enhanced distractibility may account for different behavioral and cognitive problems in children with attention deficit hyperactivity disorder (ADHD). This was investigated in the present experiment by recording event-related brain potentials (ERPs) to distracting novel sounds during performance of a visual discrimination task. The overall performance in the visual task was less accurate in the ADHD children than in the control children, and the ADHD children had a higher number of omitted responses following novel sounds. In both groups, the distracting novel sounds elicited a biphasic P3a ERP component and a subsequent frontal Late Negativity (LN). The early phase of P3a (180-240 ms) had significantly smaller amplitudes over the fronto-central left-hemisphere recording sites in the ADHD children than in the control group presumably due to an overlapping enhanced left-hemisphere dominant negative ERP component elicited in the ADHD group. Moreover, the late phase of P3a (300-350 ms) was significantly larger over the left parietal scalp areas in the ADHD children than in the controls. The LN had a smaller amplitude and shorter latency over the frontal scalp in the ADHD group than in the controls. In conclusion, the ERP and behavioral effects caused by the novel sounds reveal deficient control of involuntary attention in ADHD children that may underlie their abnormal distractibility.

Reversal of cerebral asymmetry in schizophrenia measured with magnetoencephalography.

It has been suggested that schizophrenic patients fail to develop left-hemisphere dominance because of an early disturbance in neuronal development. This hypothesis has been supported by some post-mortem. CT and magnetic resonance imaging (MRI) studies, while other in-vivo studies have given contradicting results. We used 122-channel whole-head magnetoencephalography and MRI to locate the sources of auditory evoked responses in 19 schizophrenic patients and in 20 healthy controls. Auditory evoked responses were detected in all subjects. The left-right hemisphere asymmetry of cerebral sources for auditory evoked responses was markedly dispersed among patients when compared with controls. The source locations for left auditory cortex were clearly anterior with respect to the right hemisphere in 32% of the patients, while the corresponding prevalence of this abnormal asymmetry was 0% in controls (p = 0.008. Fisher's exact test). The reversed asymmetry appeared to be associated with a shorter anterior-posterior distance between the auditory cortex and the anterior tip of the temporal lobe in the left side when compared with the right side. The reversed asymmetry was associated with higher PANSS general psychopathological score, and especially with higher guilt feelings and motor retardation scores. The large 2.5-fold standard deviation in the inter-hemispheric anterior posterior difference in the location of the auditory cortex among patients (p 0.001 for the difference in the magnitude of variance between controls and patients) clearly reflects the dispersion of the left right asymmetry into both direction, and three of the patients with 'normal asymmetry' had a greater left-right asymmetry than any of the controls. Markedly greater reversal of hemispheric asymmetry among patients implies that regulation of the development of brain asymmetry is disturbed among schizophrenic patients. Abnormality in the cerebral asymmetry may be a crucial factor in the development of schizophrenic disorder in a substantial proportion of patients. The results suggest that the reversed asymmetry is associated with the higher severity of general psychopathological symptoms.

Mismatch negativity indexes auditory temporal resolution: evidence from event-related potential (ERP) and event-related field (ERF) recordings.

This study examined auditory temporal resolution as indexed by gap detection using the mismatch negativity (MMN) component of the auditory event-related potential (ERP) and its magnetic counterpart (MMNm). ERPs were recorded in 10 subjects who were presented with auditory stimuli. These stimuli were presented in sequences of repetitive continuous 'standard' sinusoidal tones interspersed with infrequently occurring 'deviant' stimuli that differed from standards only in that they contained a silent gap midway in the stimulus. The gap size varied in separate stimulus blocks and was either 3, 5 or 7 ms. The stimuli were presented monaurally either to the left or the right ear. In a separate session, event-related magnetic fields (ERFs) were recorded from eight subjects using a similar paradigm but with gap sizes of 3, 7 or 11 ms and with binaural stimulation. Both ERP and ERF recordings showed that the smallest gap size (3 ms) did not elicit as large or reliable MMN or MMNm as did the larger ones. There were no differences in the laterality of the MMN as might be predicted on the basis of previous behavioural studies, but this result is likely a reflection of differences in task requirements. Nonetheless, the findings suggest that MMN and MMNm successfully index auditory temporal resolution thresholds, as measures that are independent of attention.

Auditory stimuli activate parietal brain regions: a whole-head MEG study.

Previous studies using magnetoencephalographic (MEG) recordings have revealed neuronal populations responding to discrete auditory stimuli in the supratemporal cortex of the human brain. We used the novel whole-head magnetometer (Neuromag-122) to determine whether regions outside the auditory cortex are activated by auditory stimulation as well. In the present study we report evidence for activation of the parietal cortex of the human brain in response to auditory stimuli.

Changes in acoustic features and their conjunctions are processed by separate neuronal populations.

We investigated the relationship between the neuronal populations involved in detecting change in two acoustic features and their conjunction. Equivalent current dipole (ECD) models of the magnetic mismatch negativity (MMNm) generators were calculated for infrequent changes in pitch, perceived sound source location, and the conjunction of these two features. All of these three changes elicited MMNms that were generated in the vicinity of auditory cortex. The location of the ECD best describing the MMNm to the conjunction deviant was anterior to those for the MMNm responses elicited by either one of the constituent features. The present data thus suggest that at least partially separate neuronal populations are involved in detecting change in acoustic features and feature conjunctions.

Event-related potential correlates of sound duration: similar pattern from birth to adulthood.

The effects of sound duration on event-related potentials (ERP) were studied in newborns and adults. Increasing tone duration from 200 to 300 ms led to the enhancement of the N2 peak amplitude, whereas two peaks became distinguishable in the N2 response elicited by 400 ms long tones. The sound-duration related ERP changes most likely reflect contribution from the sustained potential, although the observed results can also be explained by assuming the elicitation of a sound-duration sensitive frontocentrally negative ERP component (duration-sensitive N2; DN2). The pattern of duration-related changes observed in newborn infants was very similar to that in adults, regardless of the structural differences between adult and infant ERPs. The results suggest that sound duration is processed already at birth in a similar way as in adulthood.

Preserved stimulus deviance detection in Alzheimer's disease.

Aging attenuates automatic auditory discrimination to duration change, whereas frequency change detection is relatively unimpaired in aging and in Alzheimer's disease (AD). Here we studied with a whole-head magnetometer whether cortical auditory discrimination to duration change as shown by magnetic mismatch negativity (MMNm) response is impaired in AD. Twenty AD patients with mild to moderate cognitive impairment and 18 age-matched healthy subjects were monaurally presented a sequence of frequent standard tones embedded with occasional deviants with shorter duration. MMNm was significantly delayed in the left hemisphere ipsilaterally to the ear stimulated in the patient group, whereas the MMNm amplitudes over both hemispheres were quite similar in both groups. This suggests that although MMNm is delayed in the left hemisphere, the automatic discrimination to duration change in the auditory cortex is not attenuated in the early stages of AD.

Alzheimer's disease affects parallel processing between the auditory cortices.

Auditory evoked magnetic fields (AEFs) were recorded from 11 patients with Alzheimer's disease (AD) and 11 age-matched controls using the 122-channel whole-head magnetometer. Auditory stimuli were monaurally presented with interstimulus intervals (ISI) of 0.5 and 2.5 s in different blocks. The peak latencies of P50m and N100m responses were significantly longer in AD patients than in controls over the ipsilateral but not over the contralateral auditory cortex with respect to the ear stimulated. This finding suggests that parallel auditory processing is impaired between the auditory cortices in AD patients. The present MEG measurement might provide an objective index to evaluate auditory dysfunction in AD.

Optimal resource allocation for novelty detection in a human auditory memory.

A theory of resource allocation for neuronal low-level filtering is presented, based on an analysis of optimal resource allocation in simple environments. A quantitative prediction of the theory was verified in measurements of the magnetic mismatch response (MMR), an auditory event-related magnetic response of the human brain. The amplitude of the MMR was found to be directly proportional to the information conveyed by the stimulus. To the extent that the amplitude of the MMR can be used to measure resource usage by the auditory cortex, this finding supports our theory that, at least for early auditory processing, energy resources are used in proportion to the information content of incoming stimulus flow.

Age-related functional differences between auditory cortices: a whole-head MEG study.

Auditory evoked magnetic fields (AEFs) were recorded from 10 healthy younger and 10 older subjects using a whole-head magnetometer. Two blocks of tone pips were presented to the left ear with constant inter-stimulus intervals (ISIs) of 0.5 and 2.5 s. The amplitude of P50m, unlike that of N100m, was larger in the older subjects. In both groups, the peak latencies of P50m and N100m responses were significantly shorter over the contralateral than ipsilateral cortex. The interhemispheric latency difference of N100m was significantly increased with age. These findings suggest that ageing delays signal processing in the ipsilateral auditory cortex and that ageing affects consecutive AEFs in a different manner.

Memory-related processing of complex sound patterns in human auditory cortex: a MEG study.

Responses of the human brain to a complex sound pattern were recorded with a 24 channel magnetometer. The sound pattern consisted of 9 successive 50 ms segments, each with a different frequency. An infrequent change in the frequency of one of the segments elicited a magnetic mismatch response (MMNm) which peaked at about 200 ms after the deviant segment onset and resembled the electrical mismatch negativity (MMN). The equivalent current dipole which best explained the MMNm was located in the supratemporal auditory cortex, suggesting that a memory trace for the sound pattern was stored in that region.