A data-driven hypothesis-free genome-wide association (GWA) approach in imaging genetics studies allows screening the entire genome to discover novel genes that modulate brain structure, chemistry, ...and function. However, a whole brain voxel-wise analysis approach in such genome-wide based imaging genetic studies can be computationally intense and also likely has low statistical power since a stringent multiple comparisons correction is needed for searching over the entire genome and brain. In imaging genetics with functional magnetic resonance imaging (fMRI) phenotypes, since many experimental paradigms activate focal regions that can be pre-specified based on a priori knowledge, reducing the voxel-wise search to single-value summary measures within a priori ROIs could prove efficient and promising. The goal of this investigation is to evaluate the sensitivity and reliability of different single-value ROI summary measures and provide guidance in future work. Four different fMRI databases were tested and comparisons across different groups (patients with schizophrenia, their siblings, vs. normal control subjects; across genotype groups) were conducted. Our results show that four of these measures, particularly those that represent values from the top most-activated voxels within an ROI are more powerful at reliably detecting group differences and generating greater effect sizes than the others.
Abstract This study examined the effects of training in a pure tone discrimination task on relations between behavioral performance and the magnitude of auditory event-related potentials (ERPs). ...Participants performed both passive (listening) and active (detecting) oddball tasks in a pretest and two posttests (1 and 9 weeks after training). Training produced a long-term benefit in both perceptual sensitivity and reaction times (RT). Training enhanced the amplitude of the P2 ERP component to both standards and deviants at both early and delayed posttests. Importantly, P2 enhancement was strongly associated with discrimination RT, suggesting that experience facilitates rapid, preattentive access to perceptual representations. Training also elevated the mismatch negativity, possibly due to the strengthening of acoustic traces. Finally, training enhanced the amplitude of the P3 component to deviants across posttests, indicating a long-lasting effect of discrimination training on stimulus salience.
Abstract Behavioral and electrophysiological measures of target and distractor processing were examined in an auditory selective attention task before and after three weeks of distractor suppression ...training. Behaviorally, training improved target recognition and led to less conservative and more rapid responding. Training also effectively shortened the temporal distance between distractors and targets needed to achieve a fixed level of target sensitivity. The effects of training on event-related potentials were restricted to the distracting stimulus: earlier N1 latency, enhanced P2 amplitude, and weakened P3 amplitude. Nevertheless, as distractor P2 amplitude increased, so too did target P3 amplitude, connecting experience-dependent changes in distractor processing with greater distinctiveness of targets in working memory. We consider the effects of attention training on the processing priorities, representational noise, and inhibitory processes operating in working memory.
Speech prosody is processed in neither a single region nor a specific hemisphere, but engages multiple areas comprising a large-scale spatially distributed network in both hemispheres. It remains to ...be elucidated whether hemispheric lateralization is based on higher-level prosodic representations or lower-level encoding of acoustic cues, or both. A cross-language (Chinese; English) fMRI study was conducted to examine brain activity elicited by selective attention to Chinese intonation (I) and tone (T) presented in three-syllable (I3, T3) and one-syllable (I1, T1) utterance pairs in a speeded response, discrimination paradigm. The Chinese group exhibited greater activity than the English in a left inferior parietal region across tasks (I1, I3, T1, T3). Only the Chinese group exhibited a leftward asymmetry in inferior parietal and posterior superior temporal (I1, I3, T1, T3), anterior temporal (I1, I3, T1, T3), and frontopolar (I1, I3) regions. Both language groups shared a rightward asymmetry in the mid portions of the superior temporal sulcus and middle frontal gyrus irrespective of prosodic unit or temporal interval. Hemispheric laterality effects enable us to distinguish brain activity associated with higher-order prosodic representations in the Chinese group from that associated with lower-level acoustic/auditory processes that are shared among listeners regardless of language experience. Lateralization is influenced by language experience that shapes the internal prosodic representation of an external auditory signal. We propose that speech prosody perception is mediated primarily by the RH, but is left-lateralized to task-dependent regions when language processing is required beyond the auditory analysis of the complex sound.
It remains a matter of controversy precisely what kind of neural mechanisms underlie functional asymmetries in speech processing. Whereas some studies support speech-specific circuits, others suggest ...that lateralization is dictated by relative computational demands of complex auditory signals in the spectral or time domains. To examine how the brain processes linguistically relevant spectral and temporal information, a functional magnetic resonance imaging study was conducted using Thai speech, in which spectral processing associated with lexical tones and temporal processing associated with vowel length can be differentiated. Ten Thai and 10 Chinese subjects were asked to perform discrimination judgments of pitch and timing patterns presented in the same auditory stimuli under two different conditions: speech (Thai) and nonspeech (hums). In the speech condition, tasks required judging Thai tones (T) and vowel length (VL); in the nonspeech condition, homologous pitch contours (P) and duration patterns (D). A remaining task required listening passively to nonspeech hums (L). Only the Thai group showed activation in the left inferior prefrontal cortex in speech minus nonspeech contrasts for spectral (T vs. P) and temporal (VL vs. D) cues. Thai and Chinese groups, however, exhibited similar fronto-parietal activation patterns in nonspeech hums minus passive listening contrasts for spectral (P vs. L) and temporal (D vs. L) cues. It appears that lower level specialization for acoustic cues in the spectral and temporal domains cannot be generalized to abstract higher order levels of phonological processing. Regardless of the neural mechanisms underlying low-level auditory processing, our findings clearly indicate that hemispheric specialization is sensitive to language-specific factors.
Abstract Two experiments investigated the effects on auditory selection of varying distractor values in memory. Participants performed a set of control (single distractor) and distractor-variation ...(multiple distractors) tasks, classifying targets by pitch (Experiments 1A and 2) or loudness (Experiment 1B) while ignoring previously presented (and spatially separate) distractors. When both targets and distractors varied in pitch, the degree of variation among the distractors increasingly disrupted classification accuracy and reaction time to the targets. Physiologically, the degree of distractor variation boosted the N1 response to distractors, the P2 response to both targets and distractors, and the slow-wave response to targets (400–600 ms after stimulus onset). The results suggest that target representations are diminished in distinctiveness as distractors activate a wider range of the task-relevant continuum in working memory.
Differences in hemispheric functions underlying speech perception may be related to the size of temporal integration windows over which prosodic features (e.g., pitch) span in the speech signal. ...Chinese tone and intonation, both signaled by variations in pitch contours, span over shorter (
local) and longer (
global) temporal domains, respectively. This cross-linguistic (Chinese and English) study uses functional magnetic resonance imaging to show that pitch contours associated with tones are processed in the left hemisphere by Chinese listeners only, whereas pitch contours associated with intonation are processed predominantly in the right hemisphere. These findings argue against the view that all aspects of speech prosody are lateralized to the right hemisphere, and promote the idea that varying-sized temporal integration windows reflect a neurobiological adaptation to meet the ‘prosodic needs’ of a particular language.
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