Keeping in touch with the visual system: spatial alignment and multisensory integration of visual-somatosensory inputs.

Correlated sensory inputs coursing along the individual sensory processing hierarchies arrive at multisensory convergence zones in cortex where inputs are processed in an integrative manner. The exact hierarchical level of multisensory convergence zones and the timing of their inputs are still under debate, although increasingly, evidence points to multisensory integration (MSI) at very early sensory processing levels. While MSI is said to be governed by stimulus properties including space, time, and magnitude, violations of these rules have been documented.

Electrophysiological evidence for the action of a center-surround mechanism on semantic processing in the left hemisphere.

Physiological evidence was sought for a center-surround attentional mechanism (CSM), which has been proposed to assist in the retrieval of weakly activated items from semantic memory. The CSM operates by facilitating strongly related items in the "center" of the weakly activated area of semantic memory, and inhibiting less strongly related items in its "surround". In this study weak activation was created by having subjects acquire the meanings of new words to a recall criterion of only 50%.

Does the ventriloquist illusion assist selective listening?

Driver (1996) reported that the ventriloquist illusion can enhance selective listening of speech. Participants in his study listened to target and distractor words from a single loudspeaker while watching lip movements of the target words on a video monitor either above the loudspeaker or displaced to the left or right. He found that participants were more accurate in repeating the target words when the video was displaced from the loudspeaker than when the video was directly above the loudspeaker.

Mapping phonemic processing zones along human perisylvian cortex: an electro-corticographic investigation.

The auditory system is organized such that progressively more complex features are represented across successive cortical hierarchical stages. Just when and where the processing of phonemes, fundamental elements of the speech signal, is achieved in this hierarchy remains a matter of vigorous debate. Non-invasive measures of phonemic representation have been somewhat equivocal.

Identifying temporal and causal contributions of neural processes underlying the Implicit Association Test (IAT).

The Implicit Association Test (IAT) is a popular behavioral measure that assesses the associative strength between outgroup members and stereotypical and counterstereotypical traits. Less is known, however, about the degree to which the IAT reflects automatic processing. Two studies examined automatic processing contributions to a gender-IAT using a data driven, social neuroscience approach.

Regularity extraction from non-adjacent sounds.

The regular behavior of sound sources helps us to make sense of the auditory environment. Regular patterns may, for instance, convey information on the identity of a sound source (such as the acoustic signature of a train moving on the rails). Yet typically, this signature overlaps in time with signals emitted from other sound sources.

The representation of unattended, segmented sounds: a mismatch negativity (MMN) study.

The detection of an irregular, potentially relevant change (deviance) in the regular, unattended acoustic environment is ensured by the automatic deviance detection mechanism. It underlies the formation of a regularity representation and a comparison of an incoming sound with this representation. A mismatch outcome of this comparison evokes the mismatch negativity (MMN) of the event-related potential.

Right Hemispheric Contributions to Fine Auditory Temporal Discriminations: High-Density Electrical Mapping of the Duration Mismatch Negativity (MMN).

That language processing is primarily a function of the left hemisphere has led to the supposition that auditory temporal discrimination is particularly well-tuned in the left hemisphere, since speech discrimination is thought to rely heavily on the registration of temporal transitions. However, physiological data have not consistently supported this view. Rather, functional imaging studies often show equally strong, if not stronger, contributions from the right hemisphere during temporal processing tasks, suggesting a more complex underlying neural substrate.

Auditory scene analysis: the interaction of stimulation rate and frequency separation on pre-attentive grouping.

Segregation of auditory inputs into meaningful acoustic groups is a key element of auditory scene analysis. Previously, we showed that two interwoven sets of tones differing widely along multiple feature dimensions (duration, pitch and location) were pre-attentively separated into different groups, and that tones separated in this manner did not elicit the mismatch negativity component with respect to each other. Grouping was studied with human subjects using a stimulus rate too slow to induce streaming.

Perceptual load affects spatial and nonspatial visual selection processes: an event-related brain potential study.

One major question toward understanding selective attention regards the efficiency of selection. One theory contends that this efficiency in vision is determined primarily by the perceptual load (PL) imposed by the relevant stimuli; if this load is high enough to fill attentional capacity, irrelevant stimuli will be excluded before they interfere with task performance, but if this load is lower the spare capacity will be directed automatically to the irrelevant information, which will then interfere with task performance. The current study attempts to test and extend this theory in order to understand better the role of PL by examining its effects on event-related brain potentials (ERPs), voltage fluctuations recorded at the scalp that reflect underlying cognitive operations.

The effects of interstimulus interval on event-related indices of attention: an auditory selective attention test of perceptual load theory.

Objective: We examined the impact of perceptual load by manipulating interstimulus interval (ISI) in two auditory selective attention studies that varied in the difficulty of the target discrimination.

Methods: In the paradigm, channels were separated by frequency and target/deviant tones were softer in intensity. Three ISI conditions were presented: fast (300ms), medium (600ms) and slow (900ms).

Age-related changes in executive function: an event-related potential (ERP) investigation of task-switching.

Older adults have difficulty when executive control must be brought on line to coordinate ongoing behavior. To assess age-related alterations in executive processing, task-switching performance and event-related potential (ERP) activity were compared in young and older adults on switch, post-switch, pre-switch, and no-switch trials, ordered in demand for executive processes from greatest to least. In stimulus-locked averages for young adults, only switch trials elicited fronto-central P3 components, indicative of task-set attentional reallocation, whereas in older adults, three of the four trial types evinced frontal potentials.

Auditory processing in schizophrenia during the middle latency period (10-50 ms): high-density electrical mapping and source analysis reveal subcortical antecedents to early cortical deficits.

Introduction: Auditory sensory processing dysfunction is a core component of schizophrenia, with deficits occurring at 50 ms post-stimulus firmly established in the literature. Given that the initial afference of primary auditory cortex occurs at least 35 ms earlier, however, an essential question remains: how early in sensory processing do such deficits arise, and do they occur during initial cortical afference or earlier, which would implicate subcortical auditory dysfunction.

Objective: To establish the onset of the earliest deficits in auditory processing, we examined the time window demarcating the transition from subcortical to cortical processing: 10 ms to 50 ms during the so-called middle latency responses (MLRs).

Development of auditory selective attention: event-related potential measures of channel selection and target detection.

In this study, we examined developmental changes in auditory selective attention using both electrophysiological (Nd, P3b) and behavioral measures while two groups of children (9- and 12-year-olds) and adults were engaged in a two-channel selective attention task. Channel was determined by frequency (1000 or 2000 Hz). Targets in one condition were shorter than the standards (duration target) and in the other were softer (intensity target).

Rapid targeting followed by sustained deployment of visual spatial attention.

We investigated preparatory attention processes when a spatial discrimination was required at a cued location, by measuring electroencephalography following a central symbolic cue to deploy spatial attention. Electroencephalography activity in response to the cue revealed three cue-related activations: an early-onset positivity following the P1 at posterior scalp sites contralateral to the cued location, followed by cue-related frontal scalp activity and later-onset sustained activity at posterior scalp sites contralateral to the cued location. The early contralateral positivity may reflect rapid targeting of the cued location.

Preattentively grouped tones do not elicit MMN with respect to each other.

To promote preattenive grouping of two sets of tones, one set of tones with a combination of frequency and ear of delivery was intermixed with another set of tones with a different combination of frequency and ear of delivery. The ERPs elicited by tones delivered to one ear that were preceded by three or four tones delivered in a row to the other ear were associated with an enhanced N1, due to the changes in frequency and ear of delivery with respect to the immediately preceding tones. However, no mismatch negativity (MMN) was obtained, even though these tones differed from the previious tones on the two dimensions of frequency and ear of delivery.

Seeing voices: High-density electrical mapping and source-analysis of the multisensory mismatch negativity evoked during the McGurk illusion.

Seeing a speaker's facial articulatory gestures powerfully affects speech perception, helping us overcome noisy acoustical environments. One particularly dramatic illustration of visual influences on speech perception is the "McGurk illusion", where dubbing an auditory phoneme onto video of an incongruent articulatory movement can often lead to illusory auditory percepts. This illusion is so strong that even in the absence of any real change in auditory stimulation, it activates the automatic auditory change-detection system, as indexed by the mismatch negativity (MMN) component of the auditory event-related potential (ERP).

Brain potentials to sexually suggestive whistles show meaning modulates the mismatch negativity.

Electroencephalographic data suggest that spoken words produce an enhanced output of the brain's automatic deviance detection system, as reflected by the mismatch negativity. Using meaningful and nonmeaningful whistles, we sought to distinguish the effect of semantic content on the brain's deviance detection system from language-specific stimulus features. In the meaningful condition, study participants heard a human 'wolf whistle', which is commonly interpreted as an unsolicited expression of sexual attention.

Aging effects on the ERP correlates of involuntary attentional capture in speech sound analysis.

In an auditory oddball paradigm, 16 old and 16 young adults were asked to ignore binaurally presented disyllabic speech sounds and to watch a silent movie while event-related potentials (ERPs) were recorded. Four types of phonetic deviants occurred on, respectively: (1) the Stressed-First syllable, (2) the Unstressed-First syllable, (3) the Stressed-Second syllable and (4) the Unstressed-Second syllable. The nature of the phonetic change was the same across the four deviants.

ERP correlates of involuntary attention capture by prosodic salience in speech.

This study addressed whether temporally salient (e.g., word onset) or prosodically salient (e.

Grabbing your ear: rapid auditory-somatosensory multisensory interactions in low-level sensory cortices are not constrained by stimulus alignment.

Multisensory interactions are observed in species from single-cell organisms to humans. Important early work was primarily carried out in the cat superior colliculus and a set of critical parameters for their occurrence were defined. Primary among these were temporal synchrony and spatial alignment of bisensory inputs.

The neural circuitry of pre-attentive auditory change-detection: an fMRI study of pitch and duration mismatch negativity generators.

Electrophysiological studies have revealed a pre-attentive change-detection system in the auditory modality. This system emits a signal termed the mismatch negativity (MMN) when any detectable change in a regular pattern of auditory stimulation occurs. The precise intracranial sources underlying MMN generation, and in particular whether these vary as a function of the acoustic feature that changes, is a matter of some debate.

Feature versus gestalt representation of stimuli in the mismatch negativity system of 7- to 9-year-old children.

We examined preattentive auditory change detection in 7- to 9-year-old children. The question of interest was whether the preattentive comparison of stimuli indexed by the scalp-recorded mismatch negativity (MMN) was performed on representations of individual stimulus features or on gestalt representations of their combined attributes. The design of the study, based on a work by D.

Multisensory visual-auditory object recognition in humans: a high-density electrical mapping study.

Multisensory object-recognition processes were investigated by examining the combined influence of visual and auditory inputs upon object identification--in this case, pictures and vocalizations of animals. Behaviorally, subjects were significantly faster and more accurate at identifying targets when the picture and vocalization were matched (i.e.

Repetition and semantic priming of nonwords: implications for theories of N400 and word recognition.

ERPs were elicited by two types of orthographically legal, pronounceable nonwords. One nonword set was derived from and resembled real words, whereas the other set did not. Nonwords derived from related root words elicited N400 semantic priming effects similar to those obtained for words, indicating semantic activation of the root words.