Face activated neurodynamic cortical networks

Amplitude by Peak Interaction but No Evidence of Auditory Mismatch Response Deficits to Frequency Change in Preschool-Aged Children with Fetal Alcohol Spectrum Disorders

BACKGROUND

Prior studies indicate that the auditory mismatch response is sensitive to early alterations in brain development in multiple developmental disorders. Prenatal alcohol exposure is known to impact early auditory processing. The current study hypothesized alterations in the mismatch response in young children with fetal alcohol spectrum disorders (FASD).

METHODS

Participants in this study were 9 children with a FASD and 17 control children (Control) aged 3 to 6 years. Participants underwent magnetoencephalography and structural magnetic resonance imaging scans separately. We compared groups on neurophysiological mismatch negativity (MMN) responses to auditory stimuli measured using the auditory oddball paradigm. Frequent (1,000 Hz) and rare (1,200 Hz) tones were presented at 72 dB.

RESULTS

There was no significant group difference in MMN response latency or amplitude represented by the peak located ~200 ms after stimulus presentation in the difference time course between frequent and infrequent tones. Examining the time courses to the frequent and infrequent tones separately, repeated measures analysis of variance with condition (frequent vs. rare), peak (N100m and N200m), and hemisphere as within-subject factors and diagnosis and sex as the between-subject factors showed a significant interaction of peak by diagnosis (p = 0.001), with a pattern of decreased amplitude from N100m to N200m in Control children and the opposite pattern in children with FASD. However, no significant difference was found with the simple effects comparisons. No group differences were found in the response latencies of the rare auditory evoked fields.

CONCLUSIONS

The results indicate that there was no detectable effect of alcohol exposure on the amplitude or latency of the MMNm response to simple tones modulated by frequency change in preschool-aged children with FASD. However, while discrimination abilities to simple tones may be intact, early auditory sensory processing revealed by the interaction between N100m and N200m amplitude indicates that auditory sensory processing may be altered in children with FASD.

MEG-SIM: a web portal for testing MEG analysis methods using realistic simulated and empirical data

MEG and EEG measure electrophysiological activity in the brain with exquisite temporal resolution. Because of this unique strength relative to noninvasive hemodynamic-based measures (fMRI, PET), the complementary nature of hemodynamic and electrophysiological techniques is becoming more widely recognized (e.g., Human Connectome Project). However, the available analysis methods for solving the inverse problem for MEG and EEG have not been compared and standardized to the extent that they have for fMRI/PET. A number of factors, including the non-uniqueness of the solution to the inverse problem for MEG/EEG, have led to multiple analysis techniques which have not been tested on consistent datasets, making direct comparisons of techniques challenging (or impossible). Since each of the methods is known to have their own set of strengths and weaknesses, it would be beneficial to quantify them. Toward this end, we are announcing the establishment of a website containing an extensive series of realistic simulated data for testing purposes ( http://cobre.mrn.org/megsim/ ). Here, we present: 1) a brief overview of the basic types of inverse procedures; 2) the rationale and description of the testbed created; and 3) cases emphasizing functional connectivity (e.g., oscillatory activity) suitable for a wide assortment of analyses including independent component analysis (ICA), Granger Causality/Directed transfer function, and single-trial analysis.

Delays in auditory processing identified in preschool children with FASD

BACKGROUND

Both sensory and cognitive deficits have been associated with prenatal exposure to alcohol; however, very few studies have focused on sensory deficits in preschool-aged children. As sensory skills develop early, characterization of sensory deficits using novel imaging methods may reveal important neural markers of prenatal alcohol exposure.

METHODS

Participants in this study were 10 children with a fetal alcohol spectrum disorder (FASD) and 15 healthy control (HC) children aged 3 to 6 years. All participants had normal hearing as determined by clinical screens. We measured their neurophysiological responses to auditory stimuli (1,000 Hz, 72 dB tone) using magnetoencephalography (MEG). We used a multidipole spatio-temporal modeling technique to identify the location and timecourse of cortical activity in response to the auditory tones. The timing and amplitude of the left and right superior temporal gyrus sources associated with activation of left and right primary/secondary auditory cortices were compared across groups.

RESULTS

There was a significant delay in M100 and M200 latencies for the FASD children relative to the HC children (p = 0.01), when including age as a covariate. The within-subjects effect of hemisphere was not significant. A comparable delay in M100 and M200 latencies was observed in children across the FASD subtypes.

CONCLUSIONS

Auditory delay revealed by MEG in children with FASDs may prove to be a useful neural marker of information processing difficulties in young children with prenatal alcohol exposure. The fact that delayed auditory responses were observed across the FASD spectrum suggests that it may be a sensitive measure of alcohol-induced brain damage. Therefore, this measure in conjunction with other clinical tools may prove useful for early identification of alcohol affected children, particularly those without dysmorphia.