Establishing the functional connectivity of the frontotemporal network in pre-attentive change detection with Transcranial Magnetic Stimulation and event-related optical signal.

Current theories of pre-attentive deviant detection postulate that before the Superior Temporal Cortex (STC) detects a change, the Inferior Frontal Cortex (IFC) engages in stimulus analysis, which is particularly critical for ambiguous deviations (e.g., deviant preceded by a short train of standards).

Homeostatic plasticity in human extrastriate cortex following a simulated peripheral scotoma.

Neuroimaging and patient work over the past decade have indicated that, following retinal deafferentation, the human visual cortex undergoes a large-scale and enduring reorganization of its topography such that the classical retinotopic organization of deafferented visual cortex remaps to represent non-classical regions of visual space. Such long-term visual reorganization is proposed to occur through changes in the functional balance of deafferented visual circuits that engage more lasting changes through activity-dependent neuroplasticity. Here, we investigated the short-term changes in functional balance (short-term plasticity; homeostatic plasticity) that occur within deafferented human visual cortices.

Spatial Scaling of the Profile of Selective Attention in the Visual Field.

Neural mechanisms of selective attention must be capable of adapting to variation in the absolute size of an attended stimulus in the ever-changing visual environment. To date, little is known regarding how attentional selection interacts with fluctuations in the spatial expanse of an attended object. Here, we use event-related potentials (ERPs) to investigate the scaling of attentional enhancement and suppression across the visual field.

Bootstrap Signal-to-Noise Confidence Intervals: An Objective Method for Subject Exclusion and Quality Control in ERP Studies.

Analysis of event-related potential (ERP) data includes several steps to ensure that ERPs meet an appropriate level of signal quality. One such step, subject exclusion, rejects subject data if ERP waveforms fail to meet an appropriate level of signal quality. Subject exclusion is an important quality control step in the ERP analysis pipeline as it ensures that statistical inference is based only upon those subjects exhibiting clear evoked brain responses.

The influence of posterior parietal cortex on extrastriate visual activity: A concurrent TMS and fast optical imaging study.

The posterior parietal cortex (PPC) is a critical node in attentional and saccadic eye movement networks of the cerebral cortex, exerting top-down control over activity in visual cortex. Here, we sought to further elucidate the properties of PPC feedback by providing a time-resolved map of functional connectivity between parietal and occipital cortex using single-pulse TMS to stimulate the left PPC while concurrently recording fast optical imaging data from bilateral occipital cortex. Magnetic stimulation of the PPC induced transient ipsilateral occipital activations (BA 18) 24-48ms post-TMS.

Effects of subcallosal cingulate deep brain stimulation on negative self-bias in patients with treatment-resistant depression.

Background: The cognitive neuropsychological model states that antidepressant treatment alters emotional biases early in treatment, and after this initial change in emotional processing, environmental and social interactions allow for long-term/sustained changes in mood and behavior.

Objective: Changes in negative self-bias after chronic subcallosal cingulate (SCC) deep brain stimulation (DBS) were investigated with the hypothesis that treatment would lead to changes in emotional biases followed by changes in symptom severity.

Methods: Patients (N = 7) with treatment-resistant depression were assessed at three time points: pre-treatment; after one month stimulation; and after six months stimulation.

Concurrent application of TMS and near-infrared optical imaging: methodological considerations and potential artifacts.

The simultaneous application of transcranial magnetic stimulation (TMS) with non-invasive neuroimaging provides a powerful method for investigating functional connectivity in the human brain and the causal relationships between areas in distributed brain networks. TMS has been combined with numerous neuroimaging techniques including, electroencephalography (EEG), functional magnetic resonance imaging (fMRI), and positron emission tomography (PET). Recent work has also demonstrated the feasibility and utility of combining TMS with non-invasive near-infrared optical imaging techniques, functional near-infrared spectroscopy (fNIRS) and the event-related optical signal (EROS).

Enhancement and suppression in the visual field under perceptual load.

The perceptual load theory of attention proposes that the degree to which visual distractors are processed is a function of the attentional demands of a task-greater demands increase filtering of irrelevant distractors. The spatial configuration of such filtering is unknown. Here, we used steady-state visual evoked potentials (SSVEPs) in conjunction with time-domain event-related potentials (ERPs) to investigate the distribution of load-induced distractor suppression and task-relevant enhancement in the visual field.

Frontal theta cordance predicts 6-month antidepressant response to subcallosal cingulate deep brain stimulation for treatment-resistant depression: a pilot study.

Deep brain stimulation (DBS) of subcallosal cingulate white matter (SCC) may be an effective approach for treatment-resistant depression (TRD) that otherwise fails to respond to more conventional therapies, but DBS is invasive, costly, and has potential for adverse effects. Therefore, it is important to identify potential biomarkers for predicting antidepressant response before intervention. Resting-state EEG was recorded from 12 TRD patients at pre-treatment baseline, after 4 weeks SCC DBS, and after 24 weeks SCC DBS.

Neural mechanisms of short-term plasticity in the human visual system.

Following circumscribed retinal damage, extensive reorganization of topographically organized visual cortical areas has been demonstrated in several species of mammals (including humans). Although reorganization is often studied over extended time scales, neural response properties change within seconds of retinal deafferentation. Understanding the mechanisms underlying these short-term effects is essential for developing a complete picture of representational plasticity.

Examining cortical dynamics and connectivity with simultaneous single-pulse transcranial magnetic stimulation and fast optical imaging.

Transcranial magnetic stimulation (TMS) is a widely used experimental and clinical technique that directly induces activity in human cortex using magnetic fields. However, the neural mechanisms of TMS-induced activity are not well understood. Here, we introduce a novel method of imaging TMS-evoked activity using a non-invasive fast optical imaging tool, the event-related optical signal (EROS).

Dynamics of target and distractor processing in visual search: evidence from event-related brain potentials.

When multiple objects are present in a visual scene, salient and behaviorally relevant objects are attentionally selected and receive enhanced processing at the expense of less salient or less relevant objects. Here we examined three lateralized components of the event-related potential (ERP) - the N2pc, Ptc, and SPCN - as indices of target and distractor processing in a visual search paradigm. Participants responded to the orientation of a target while ignoring an attentionally salient distractor and ERPs elicited by the target and the distractor were obtained.

Anger management: age differences in emotional modulation of visual processing.

Although positive and negative images enhance the visual processing of young adults, recent work suggests that a life-span shift in emotion processing goals may lead older adults to avoid negative images. To examine this tendency for older adults to regulate their intake of negative emotional information, the current study investigated age-related differences in the perceptual boost received by probes appearing over facial expressions of emotion. Visually-evoked event-related potentials were recorded from the scalp over cortical regions associated with visual processing as a probe appeared over facial expressions depicting anger, sadness, happiness, or no emotion.

Event-related potentials dissociate effects of salience and space in biased competition for visual representation.

Background: Selective visual attention is the process by which the visual system enhances behaviorally relevant stimuli and filters out others. Visual attention is thought to operate through a cortical mechanism known as biased competition. Representations of stimuli within cortical visual areas compete such that they mutually suppress each others' neural response.

Human transsaccadic visual processing: presaccadic remapping and postsaccadic updating.

With every movement of the eye the visual field is drastically displaced in space. However, our visual experience is stable rather than constantly jittering with every saccade. One neural mechanism thought to underlie such spatial constancy across saccades is predictive remapping in which visual receptive fields remap to non-classical future locations in anticipation of a forthcoming saccade.

Steady-state signatures of visual perceptual load, multimodal distractor filtering, and neural competition.

The perceptual load theory of attention posits that attentional selection occurs early in processing when a task is perceptually demanding but occurs late in processing otherwise. We used a frequency-tagged steady-state evoked potential paradigm to investigate the modality specificity of perceptual load-induced distractor filtering and the nature of neural-competitive interactions between task and distractor stimuli. EEG data were recorded while participants monitored a stream of stimuli occurring in rapid serial visual presentation (RSVP) for the appearance of previously assigned targets.

Competitive interaction degrades target selection: an ERP study.

Localized attentional interference (LAI) occurs when attending to a visual object degrades processing of nearby objects. Competitive interaction accounts of LAI explain the phenomenon as the result of competition among objects for representation in extrastriate cortex. Here, we examined the N2pc component of the event-related potential (ERP) as a likely neural correlate of LAI.

Visual perceptual load modulates an auditory microreflex.

The postauricular reflex (PAR) is a vestigial microreflex evoked by an abrupt auditory onset. Previous studies have indicated that the PAR is unaffected by auditory selective attention. Here, we report that the PAR can be modulated by a crossmodal manipulation of attentional demands within the visual modality.

The importance of temporal distinctiveness for forgetting over the short term.

Rapidly forgetting information once attention is diverted seems to be a ubiquitous phenomenon. The cause of this rapid decline has been debated for decades; some researchers claim that memory traces decay as a function of time out of the focus of attention, whereas others claim that prior memory traces cause confusability by interfering with the current trace. Here we demonstrate that performance after a long delay can be better than performance after a short delay if the temporal confusability between the current item and previous items is reduced.

Electrophysiological correlates of presaccadic remapping in humans.

Saccadic eye movements cause rapid displacements of space, yet the visual field is perceived as stable. A mechanism that may contribute to maintaining visual stability is the process of predictive remapping, in which receptive fields shift to their future locations prior to the onset of a saccade. We investigated electrophysiological correlates of remapping in humans using event-related potentials.

Attending to depth: electrophysiological evidence for a viewer-centered asymmetry.

It has been proposed that the configuration of visuospatial attention in depth is viewer-centered such that an attentional gradient is concentrated between an observer and attended depth, trailing off steeply beyond. To investigate this asymmetry, event-related potentials were recorded while participants attended to far or near depths in a pictorial scene. The attention-sensitive visual components, P1 (100-160 ms) and N1 (160-220 ms), were assessed for amplitude differences.