Non-attended Stimuli Research Articles

Visual Attention Modulates Glutamate-Glutamine Levels in Vestibular Cortex: Evidence from Magnetic Resonance Spectroscopy.

Attending to a stimulus enhances the neuronal responses to it, while responses to nonattended stimuli are not enhanced and may even be suppressed. Although the neural mechanisms of response enhancement for attended stimuli have been intensely studied, the neural mechanisms underlying attentional suppression remain largely unknown. It is uncertain whether attention acts to suppress the processing in sensory cortical areas that would otherwise process the nonattended stimulus or the subcortical input to these cortical areas. Moreover, the neurochemical mechanisms inducing a reduction or suppression of neuronal responses to nonattended stimuli are as yet unknown. Here, we investigated how attention directed toward visual processing cross-modally acts to suppress vestibular responses in the human brain. By using functional magnetic resonance spectroscopy in a group of female and male subjects, we find that attention to visual motion downregulates in a load-dependent manner the concentration of excitatory neurotransmitter (glutamate and its precursor glutamine, referred to together as Glx) within the parietoinsular vestibular cortex (PIVC), a core cortical area of the vestibular system, while leaving the concentration of inhibitory neurotransmitter (GABA) in PIVC unchanged. This makes PIVC less responsive to excitatory thalamic vestibular input, as corroborated by functional magnetic resonance imaging. Together, our results suggest that attention acts to suppress the processing of nonattended sensory cues cortically by neurochemically rendering the core cortical area of the nonattended sensory modality less responsive to excitatory thalamic input.SIGNIFICANCE STATEMENT Here, we address a fundamental problem that has eluded attention research for decades, namely, how the brain ignores irrelevant stimuli. To date, three classes of solutions to this problem have been proposed: (1) enhancement of GABAergic interneuron activity in cortex, (2) downregulation of glutamatergic cell activity in cortex; and (3) downregulation of neural activity in thalamic projection areas, which would then provide the cortex with less input. Here, we use magnetic resonance spectroscopy in humans and find support for the second hypothesis, implying that attention to one sensory modality involves the suppression of irrelevant stimuli of another sensory modality by downregulating glutamate in the cortex.

Spatial attention enhances cortical tracking of quasi-rhythmic visual stimuli

Successfully interpreting and navigating our natural visual environment requires us to track its dynamics constantly. Additionally, we focus our attention on behaviorally relevant stimuli to enhance their neural processing. Little is known, however, about how sustained attention affects the ongoing tracking of stimuli with rich natural temporal dynamics. Here, we used MRI-informed source reconstructions of magnetoencephalography (MEG) data to map to what extent various cortical areas track concurrent continuous quasi-rhythmic visual stimulation. Further, we tested how top-down visuo-spatial attention influences this tracking process. Our bilaterally presented quasi-rhythmic stimuli covered a dynamic range of 4–20 ​Hz, subdivided into three distinct bands. As an experimental control, we also included strictly rhythmic stimulation (10 vs 12 ​Hz). Using a spectral measure of brain-stimulus coupling, we were able to track the neural processing of left vs. right stimuli independently, even while fluctuating within the same frequency range. The fidelity of neural tracking depended on the stimulation frequencies, decreasing for higher frequency bands. Both attended and non-attended stimuli were tracked beyond early visual cortices, in ventral and dorsal streams depending on the stimulus frequency. In general, tracking improved with the deployment of visuo-spatial attention to the stimulus location. Our results provide new insights into how human visual cortices process concurrent dynamic stimuli and provide a potential mechanism – namely increasing the temporal precision of tracking – for boosting the neural representation of attended input.

A model for attentional information routing through coherence predicts biased competition and multistable perception.

Selective attention allows to focus on relevant information and to ignore distracting features of a visual scene. These principles of information processing are reflected in response properties of neurons in visual area V4: if a neuron is presented with two stimuli in its receptive field, and one is attended, it responds as if the nonattended stimulus was absent (biased competition). In addition, when the luminance of the two stimuli is temporally and independently varied, local field potentials are correlated with the modulation of the attended stimulus and not, or much less, correlated with the nonattended stimulus (information routing). To explain these results in one coherent framework, we present a two-layer spiking cortical network model with distance-dependent lateral connectivity and converging feed-forward connections. With oscillations arising inherently from the network structure, our model reproduces both experimental observations. Hereby, lateral interactions and shifts of relative phases between sending and receiving layers (communication through coherence) are identified as the main mechanisms underlying both biased competition as well as selective routing. Exploring the parameter space, we show that the effects are robust and prevalent over a broad range of parameters. In addition, we identify the strength of lateral inhibition in the first model layer as crucial for determining the working regime of the system: increasing lateral inhibition allows a transition from a network configuration with mixed representations to one with bistable representations of the competing stimuli. The latter is discussed as a possible neural correlate of multistable perception phenomena such as binocular rivalry.

Attention drives synchronization of alpha and beta rhythms between right inferior frontal and primary sensory neocortex.

The right inferior frontal cortex (rIFC) is specifically associated with attentional control via the inhibition of behaviorally irrelevant stimuli and motor responses. Similarly, recent evidence has shown that alpha (7-14 Hz) and beta (15-29 Hz) oscillations in primary sensory neocortical areas are enhanced in the representation of non-attended stimuli, leading to the hypothesis that allocation of these rhythms plays an active role in optimal inattention. Here, we tested the hypothesis that selective synchronization between rIFC and primary sensory neocortex occurs in these frequency bands during inattention. We used magnetoencephalography to investigate phase synchrony between primary somatosensory (SI) and rIFC regions during a cued-attention tactile detection task that required suppression of response to uncertain distractor stimuli. Attentional modulation of synchrony between SI and rIFC was found in both the alpha and beta frequency bands. This synchrony manifested as an increase in the alpha-band early after cue between non-attended SI representations and rIFC, and as a subsequent increase in beta-band synchrony closer to stimulus processing. Differences in phase synchrony were not found in several proximal control regions. These results are the first to reveal distinct interactions between primary sensory cortex and rIFC in humans and suggest that synchrony between rIFC and primary sensory representations plays a role in the inhibition of irrelevant sensory stimuli and motor responses.

Beyond P300: an auditory ERP paradigm with sequential stimulation

Event Abstract Back to Event Beyond P300: an auditory ERP paradigm with sequential stimulation Johannes Hoehne1* and Michael Tangermann2 1 Berlin Institute of Technology, Neurotechnology, Germany 2 University of Freiburg, Germany 1. Research Background: Brain-computer interfaces (BCIs) aim to establish communication channels which are independent of muscle movements, relying on the real-time analysis of brain signals instead. Typically, BCI paradigms which evaluate evoked potentials in the EEG follow the principles of the oddball paradigm with random sequences of target and non-target stimuli. We investigate whether this randomness can be removed, allowing a very user-friendly paradigm where the user knows the order of stimulation. 2. Methods We performed an EEG study with 10 subjects. The subjects listened to a rapid sequence (SOA=83,3ms) of 30 auditory stimuli with the task to attend to only one stimulus/letter. The spoken alphabet with each letter lasting 250 ms was used as stimuli, which were presented either in a pseudorandom order (condition 1) or in a sequential order (condition 2). 3. Results Despite the rapid stimulation sequence, we found that the oddball paradigm (condition 1) elicited typical class-discriminative ERP components, such as N200 and P300. The evoked potentials in the sequential condition also showed class discriminant features, such that the EEG signature from attended stimuli was different from non-attended stimuli. However Figure 1 depicts that the ERPs from the sequential condition were clearly distinct from those components observed in the oddball condition, since they were lacking N200 and P300 components. 4. Conclusions Striving for the simplest-possible setup, we describe that one can also remove any randomness from an ERP-based BCI paradigm, by presenting 30 characters which are presented in a fix sequential order. We find that this paradigm - called CharStreamer - also elicits class discriminant EEG features which were however different to an oddball paradigm as they were lacking N200 and P300 components. Keywords: Auditory Perception, EEG, ERP, Brain-Computer Interfacing, oddball, Sequential stimuli, non-randomly ordered stimulation Conference: XII International Conference on Cognitive Neuroscience (ICON-XII), Brisbane, Queensland, Australia, 27 Jul - 31 Jul, 2014. Presentation Type: Poster Topic: Cognition and Executive Processes Citation: Hoehne J and Tangermann M (2015). Beyond P300: an auditory ERP paradigm with sequential stimulation. Conference Abstract: XII International Conference on Cognitive Neuroscience (ICON-XII). doi: 10.3389/conf.fnhum.2015.217.00163 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 19 Feb 2015; Published Online: 24 Apr 2015. * Correspondence: Mr. Johannes Hoehne, Berlin Institute of Technology, Neurotechnology, Berlin, Germany, j.hoehne@tu-berlin.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Johannes Hoehne Michael Tangermann Google Johannes Hoehne Michael Tangermann Google Scholar Johannes Hoehne Michael Tangermann PubMed Johannes Hoehne Michael Tangermann Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Early Attentional Modulation of the Neural Network Evoked with the Auditory Paired-click Paradigm: An MEG Study

Although numerous research studies have explored the functional attributes of the human duration perception, the spatio- temporal information on cortical networks underlying this process is still an open question. Moreover, the issue of possible differences in the nature of timing mechanisms responsible for perception of sub- and supra-second intervals requires the implementation of the functional brain imaging techniques with both high spatial and temporal resolution. Attention is very frequently used as a modulating factor for the perceived duration of a sensory stimulus. The non-attended stimuli appear to last shorter than the attended ones, increasing the perceived duration of a concurrent stimulus (Gorea, 2011). This study challenges the accepted model of early sensory responses, activated during the first 100ms after stimulus presentation, as preattentive, automatic processes which modulate the neural sensitivity to incoming stimuli (gating phenomena). We utilized Elekta Neuromag 306-channel whole-head system for magnetoencephalography (MEG) measurements and multi-dipole Calibrated Start Spatio Temporal (CSST) localization technique (Ranken et al., 2002) to investigate whether voluntary attention directed at the second tone of a pair in the standard paired-click paradigm could affect cortical networks underlying the gating out phenomenon. MEG recordings were obtained in a magnetically shielded room at the Biomagnetic Center in Jena, Germany. Two consecutive (ISI=500ms) identical short tonnes (S1 and S2; duration=20ms; f=1200Hz; ITI=8±1s) were used to evoke standard gating cortical responses in 19 healthy participants (21-38 years). In the second condition, the task was to direct attention toward the second tone and to respond to a rarely presented non-identical second tone of the pair (R=1300Hz, p(S1R)=0.3). MEG recordings showed transient early and middle latency responses with peak amplitudes over the temporo-parietal sensors followed by a peak of a sustained activity. Less prominent transient activity was recorded over the frontal sensors, accompanied with a more steady- state component from 100 until 400ms post-stimulus for both conditions. Preliminary results of the CSST spatio-temporal analyses revealed 4-6 brain regions activated during 20-500ms time interval including bilateral superior temporal gyrus (STG), bilateral and medial prefrontal (PF), bilateral parietal (PA) regions, and central motor cortex area. A cortical source underlying the steady-state component was identified in the left prefrontal region for S1 tone, and in central posterior regions (PA) for the repeated tone S2. During the standard paradigm the M50 gating suppression was observed only for bilateral STG sources while bilateral PF and PA sources did not show any reduction in the response during the first 100ms post-stimulus. Targeting the attention towards the second tone enhanced the M50 amplitude of the bilateral STG responses in respect to the repeated stimulus S2 and caused a change in the activated network evident by the emergence of a new generator in the medial PF area (orbitofrontal) instead of dorsolateral PF generators evoked in non-attended condition. These results demonstrate that voluntary attention can exert a topological and functional modulatory influence on the neural network even during early stages of auditory processing.

A model for selective visual attention predicts information routing

A remarkable feature of the brain is its ability to flexibly process information in a context-dependent manner. For example, selective attention allows to focus on relevant information, and to ignore distracting features of a visual scene. Here we develop a model to investigate a putative neural mechanism by which attention might dynamically change the functional configuration of networks in visual cortex. Since efferents from multiple neurons in an early visual area converge onto the same neuron in a higher area, synaptic input induced by an attended object should be more efficient in driving the post-synaptic neuron than an input induced by a simultaneously presented, but unattended object. In fact, it has been found that the firing rate of a post-synaptic neuron in such a situation is similar to its activity when the unattended stimulus is absent. However, if no attention is directed while two stimuli are present, the firing rate of the post-synaptic neuron is approximately at the mean of the rates at which it would fire if each of two stimuli were presented alone (biased competition [1,2]). Attention is thus assumed to selectively promote information transfer between visual areas. Recent experiments support this idea by showing that V4 local field potentials are correlated with a temporal modulation of the attended stimulus and not with the temporal modulation of a non-attended stimulus in the same receptive field (gating [3]). Several models were proposed to explain the effect of biased competition and information routing [4,5]. However, here we construct a biophysically plausible model that specifically reproduces both experimental results within the same framework. It comprises four populations of recurrently coupled networks of conductance-based spiking neurons with lateral inhibition. Upon activation, these populations engage in oscillatory activity. The first two networks correspond to a lower visual area with non-overlapping receptive fields, which both project to the third and the fourth network corresponding to higher area populations with larger receptive fields. We assume attention to manifest as an additional input to one lower area population. Deployment of attention consequently results in a bias of firing rates between the populations in the lower area. This bias induces a phase relation between the lower and the higher area that is more suitable for information transmission from the attended stimulus. We show that this mechanism is capable to explain both, the biased competition effect of the firing rate, and selective gating of information flow. We thus propose a combination of cortical network topology, neuronal population dynamics, and selective additional input as putative neural underpinnings of attention.

Age-related loss in attention-based modulation of tactile stimuli at early stages of somatosensory processing

Normal aging has been linked to impairments in gating of irrelevant sensory information and neural markers of diminished cognitive processing. Whilst much of the research in this area has focussed on visual and auditory modalities it is unclear to what degree these findings apply to somatosensation. Therefore we investigated how age impacts early event-related potentials (ERPs) arising from relevant or irrelevant vibrotactile stimuli to the fingertips. Specifically, we hypothesised that older adults would demonstrate reduced attention-based modulation of tactile ERPs generated at early stages of cortical somatosensory processing. In accord with previous research we also expected to observe diminished P300 responses to attended targets and behavioural deficits. Participants received vibrotactile stimulation to the second and fifth digit on the left hand and reported target stimuli on one digit only (as instructed) with comparisons between two age groups: (1) Young adults (age range 20–39) and (2) Older adults (age range 62–89). ERP amplitudes for the P50, N70, P100, N140 and long latency positivity (LLP) were quantified for attended and non-attended trials at several electrodes (C4, CP4, CP3 and FC4). The P300 in response to attended target stimuli was measured at CPZ. There was no effect of attention on the P50 and N70 however the P100, N140 and LLP were modulated with attention. In both age groups the P100 and LLP were more positive during trials where the stimuli were attended to, whilst the N140 was enhanced for non-attended stimuli. Comparisons between groups revealed a reduction in P100 attention-based modulation for the older adults versus the young adults. This effect was due to a loss of suppression of the non-attended stimuli in older subjects. Moreover, the P300 was both slower and reduced in peak amplitude for older subjects in response to attended targets. Finally, older adults demonstrated impaired performance in terms of both reduced target detection accuracy and in reporting more false positives. Overall, present results reveal a deficit in suppressing irrelevant tactile information during an attention-demanding task which possibly relates to reduced markers of performance. Such a loss of inhibitory function is consistent with age-related change associated with a decline in executive control via prefrontal regions.

Transient inhibition of the dorsolateral prefrontal cortex disrupts attention-based modulation of tactile stimuli at early stages of somatosensory processing

Damage to the dorsolateral prefrontal cortex (DLPFC) impairs gating of irrelevant sensory information at early cortical processing stages. We investigated how transient inhibition of DLPFC impacts early event-related potentials (ERPs) arising from relevant or irrelevant vibrotactile stimuli to the fingertips. Specifically, we hypothesized that suppression of DLPFC using continuous theta burst stimulation (cTBS) would result in reduced attention-based modulation of tactile ERPs generated at early stages of cortical somatosensory processing. Participants received vibrotactile stimulation to the second and fifth digit on the left hand and reported target stimuli on one digit only (as instructed) in one of three groups following: (1) cTBS over DLPFC (40s; 600 pulses of 3 stimuli at 50Hz repeated at 5Hz using 80% of resting motor threshold for abductor pollicis brevis), (2) sham stimulation, or (3) no stimulation. ERP amplitudes for the P50, N70, P100, N140 and long latency positivity (LLP) were quantified for attended and non-attended trials at C4, CP4, and CP3 electrodes. There was no effect of attention on the P50 and N70 however the P100, N140 and LLP were modulated with attention. The P100 and LLP were significantly more positive during trials where the stimuli were attended to, while the N140 was enhanced for non-attended stimuli. Comparisons between groups revealed a reduction in P100 attention-based modulation for the cTBS group versus sham and no-stimulation groups. While the P100 was clearly reduced for non-attended stimuli relative to attended stimuli in the sham and no-stimulation groups, this effect was attenuated following cTBS. The reduction in attentional modulation of the P100 following cTBS suggests that the DLPFC contributes to filtering irrelevant somatosensory information at early cortical processing stages. Notably the influence of the DLPFC in attention-based modulation was evident even within digits of the same hand. The present results support the use of cTBS as an effective means of transiently suppressing DLPFC excitability.

Routing of information flow by selective visual attention in LFPs of monkey area V4

Routing of information flow by selective visual attention in LFPs of monkey area V4

Separable Codes for Attention and Luminance Contrast in the Primary Visual Cortex

The visual system encodes the features of visual stimuli as well as their behavioral relevance. Stimuli with a high luminance contrast evoke more activity in the visual cortex than stimuli with a low contrast. At the same time, attended stimuli evoke more activity than nonattended stimuli. There is a debate about how visual features and attention jointly determine neuronal activity in the visual cortex. Some studies suggested that attention increases apparent contrast (Reynolds et al., 2000), others that attention amplifies responses by a constant factor (Williford and Maunsell, 2006), and yet others that attention and contrast have largely additive effects (Buracas and Boynton, 2007; Thiele et al., 2009). The influence of attention on contrast sensitivity differs between neurons, raising the possibility that attention and contrast could be coded conjointly in a population of neurons. Here we investigate this possibility by recording neuronal activity at multiple sites in the primary visual cortex of macaque monkeys using multielectrode recording techniques and support vector machines to decode attended stimuli as well as stimulus contrast. We find that many, but not all, V1 neurons are influenced by attention and that the effects of attention and contrast are additive on average. Stimulus contrast can be decoded from neuronal responses not strongly modulated by attention, whereas the attended stimulus can be decoded as the difference in activity of cells that are influenced by attention and cells that are not. The success of the approach suggests that visual attention and stimulus contrast are represented by largely separable codes.

P3a and P3b of event-related potentials in persons with Asperger disorder

Although numerous research studies have explored the functional attributes of the human duration perception, the spatio- temporal information on cortical networks underlying this process is still an open question. Moreover, the issue of possible differences in the nature of timing mechanisms responsible for perception of sub- and supra-second intervals requires the implementation of the functional brain imaging techniques with both high spatial and temporal resolution. Attention is very frequently used as a modulating factor for the perceived duration of a sensory stimulus. The non-attended stimuli appear to last shorter than the attended ones, increasing the perceived duration of a concurrent stimulus (Gorea, 2011). This study challenges the accepted model of early sensory responses, activated during the first 100 ms after stimulus presentation, as preattentive, automatic processes which modulate the neural sensitivity to incoming stimuli (gating phenomena). We utilized Elekta Neuromag 306-channel whole-head system for magnetoencephalography (MEG) measurements and multi-dipole Calibrated Start Spatio Temporal (CSST) localization technique (Ranken et al., 2002) to investigate whether voluntary attention directed at the second tone of a pair in the standard paired-click paradigm could affect cortical networks underlying the gating out phenomenon. MEG recordings were obtained in a magnetically shielded room at the Biomagnetic Center in Jena, Germany. Two consecutive (ISI=500 ms) identical short tonnes (S1 and S2; duration=20ms; f=1200 Hz; ITI=8±1s) were used to evoke standard gating cortical responses in 19 healthy participants (21-38 years). In the second condition, the task was to direct attention toward the second tone and to respond to a rarely presented non-identical second tone of the pair (R=1300 Hz, p(S1R)=0.3). MEG recordings showed transient early and middle latency responses with peak amplitudes over the temporo-parietal sensors followed by a peak of a sustained activity. Less prominent transient activity was recorded over the frontal sensors, accompanied with a more steady- state component from 100 until 400 ms post-stimulus for both conditions. Preliminary results of the CSST spatio-temporal analyses revealed 4-6 brain regions activated during 20-500 ms time interval including bilateral superior temporal gyrus (STG), bilateral and medial prefrontal (PF), bilateral parietal (PA) regions, and central motor cortex area. A cortical source underlying the steady-state component was identified in the left prefrontal region for S1 tone, and in central posterior regions (PA) for the repeated tone S2. During the standard paradigm the M50 gating suppression was observed only for bilateral STG sources while bilateral PF and PA sources did not show any reduction in the response during the first 100 ms post-stimulus. Targeting the attention towards the second tone enhanced the M50 amplitude of the bilateral STG responses in respect to the repeated stimulus S2 and caused a change in the activated network evident by the emergence of a new generator in the medial PF area (orbitofrontal) instead of dorsolateral PF generators evoked in non-attended condition. These results demonstrate that voluntary attention can exert a topological and functional modulatory influence on the neural network even during early stages of auditory processing.

Highly selective processing of temporal information from attended stimuli in macaque’s visual area V4

Highly selective processing of temporal information from attended stimuli in macaque’s visual area V4

Attention modulates the phase coherence between macaque visual areas V1 and V4

Event Abstract Back to Event Attention modulates the phase coherence between macaque visual areas V1 and V4 Simon Neitzel1*, Sunita Mandon1 and Andreas K. Kreiter1 1 University of Bremen, Brain Research Institute, Departement of Theoretical Neurobiology, Germany In a complex visual scene, typically multiple objects are present in the large receptive fields (RFs) of neurons in higher visual areas. Selective processing of the behaviourally relevant object is therefore faced with the problem that often only a small part of the entire synaptic input carries the relevant signals. It is therefore very remarkable that neurons are able to respond to the attended object, as if no others would be present (Moran & Desimone, 1985; Science, 229, 782-784). We therefore hypothesize that attention enhances dynamically the effective connectivity of such a neuron with those afferents representing the attended object and diminishes effective connectivity with others carrying irrelevant signals. Recently it has been proposed that changes of neuronal synchronization in the gamma-frequency range (40-100 Hz) may serve this purpose (Kreiter, 2006; Neural Networks, 19, 1443-1444). To test this hypothesis, we recorded local field potentials (LFPs) with multiple intracortical electrodes from visual areas V1 and V4 of a macaque monkey performing an attentionally demanding shape-tracking task. Two objects going through a sequence of continuous deformations of their shape were presented extrafoveally and simultaneously (see also Taylor et al., 2005; Cerebral Cortex, 15, 1424-1437). Both objects had the size of a classical V1 RF and were placed close to each other to fit into one V4 RF. The monkey had to respond to the reoccurrence of the initial shape for the cued object. Because the shapes were continuously morphing, and shape perception depends critically on attention (Rock & Gutman, 1981; Journal of Experimental Psychology: Human Perception and Performance, 7, 275-285), the monkey had to attend the cued stream continuously in order to recognize the reappearance of the target shape. We used Morlet-wavelets to extract phase information from the recorded LFPs for estimating the phase coherence as a measure of synchronization between V1 and V4 recordings sites. We found that the two populations of V1 neurons driven by the attended and by the non-attended stimulus showed strongly different strength of synchronization with the V4 population getting synaptic input from both of them. If the recorded V1 population was representing the attended stimulus robust phase coherence was measured. If the same population was representing the non-attended stimulus the phase coherence was strongly diminished. The stronger coupling between neurons in area V4 and that part of their afferent neurons in V1 carrying the behaviourally relevant information supports the hypothesis that information flow in the visual system is modulated by attention-dependent changes of neuronal synchronization. Thus, differential synchronization may serve as a mechanism to switch between different patterns of effective connectivity within the network of anatomical connections and thereby to route signals and information according to the quickly varying demands of information processing. Acknowledgments:Supported by BMBF Bernstein Group Bremen, "Functional adaption of the visual system" Conference: Bernstein Conference on Computational Neuroscience, Frankfurt am Main, Germany, 30 Sep - 2 Oct, 2009. Presentation Type: Poster Presentation Topic: Information processing in neurons and networks Citation: Neitzel S, Mandon S and Kreiter AK (2009). Attention modulates the phase coherence between macaque visual areas V1 and V4. Front. Comput. Neurosci. Conference Abstract: Bernstein Conference on Computational Neuroscience. doi: 10.3389/conf.neuro.10.2009.14.061 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 26 Aug 2009; Published Online: 26 Aug 2009. * Correspondence: Simon Neitzel, University of Bremen, Brain Research Institute, Departement of Theoretical Neurobiology, Bremen, Germany, neitzel@brain.uni-bremen.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Simon Neitzel Sunita Mandon Andreas K Kreiter Google Simon Neitzel Sunita Mandon Andreas K Kreiter Google Scholar Simon Neitzel Sunita Mandon Andreas K Kreiter PubMed Simon Neitzel Sunita Mandon Andreas K Kreiter Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Spatial attention increases performance but not subjective confidence in a discrimination task

Selective attention to a target yields faster and more accurate responses. Faster response times, in turn, are usually associated with increased subjective confidence. Could the decrease in reaction time in the presence of attention therefore simply reflect a shift toward more confident responses? We here addressed the extent to which attention modulates accuracy, processing speed, and confidence independently. To probe the effect of spatial attention on performance, we used two attentional manipulations of a visual orientation discrimination task. We demonstrate that spatial attention significantly increases accuracy, whereas subjective confidence measures reveal overconfidence in non-attended stimuli. At constant confidence levels, reaction times showed a significant decrease (by 15-49%, corresponding to 100-250 ms). This dissociation of objective performance and subjective confidence suggests that attention and awareness, as measured by confidence, are distinct, albeit related, phenomena.

Characteristics of activation in the parietal areas of the cortex in humans in different types of visual attention

The state of cortical activation in the parietal and temporal areas was assessed using evoked potentials (EP) during the tasks of selection of lateralized visual stimuli requiring three different types of attention: to stimulus shape, to stimulus position, and to both. Studies in 15 young, healthy subjects involved recording of EP in six cortical leads: P3, P4, T3, T4, T5, and T6, with analysis of the endogenous EP components CNV, N1, P3, and the EP complex [N1-P3] (according to standard terminology). Changes in EP components in response to the attended and non-attended stimulus features were compared. Differences between them were assessed using the index of selectivity of attention to one or another feature of the visual stimuli. In the parietal area, selectivity was seen in conditions of attention to stimulus position and attention to stimulus shape. In conditions of simultaneous attention, the indexes of selectivity were essentially equal to the sum of the indexes of selectivity of attention to shape and position. The most marked endogenous EP components (CNV, N1, and P3) in visual selection were seen in the parietal areas, with a greater gradient of increased activation of the parietal areas of the cortex as the need for attention increased, along with a lower threshold for the action of attention, and anticipatory development of the P3 wave in the parietal area as compared with the temporal area. These results suggest that the parietal cortex has priority in the visual attention system and that the magnocellular (M) pathway forms the most important visual input to the dorsal parietal area of the neocortex.

An ERP Investigation of Semantic Priming, Repetition Priming, and Negative Priming in Schizophrenic Patients

The processing of attended and nonattended stimuli in schizophrenic patients was examined with event-related potentials (ERPs) in a lexical decision task. In positive semantic and repetition priming the N400 amplitude did not differ between a group of 17 medicated schizophrenic patients and a group of 20 matched healthy controls. However, negative priming affected the N400 only in controls. Reaction time effects were dissociated from these ERP effects, with patients showing stronger positive priming than controls but identical negative priming. The semantic processes related to the N400 appear to be intact in schizophrenic patients, but patients seem to incorporate less context information (about the nonattended prime) in their episodic memory traces. A stronger increase of the posterior late positive complex in parallel to the stronger positive priming in schizophrenic patients may reflect relatively stronger automatic memory retrieval processes in patients.

Evidence for split foci of attention in a priming paradigm

Most models of visuospatial attention include the notion that attention is dedicated to a single location in space. However, several researchers have found evidence that under appropriate circumstances, attention may be allocated to noncontiguous locations (e.g., Awh & Pashler, 2000; Bichot, Cave, & Pashler, 1999; Kramer & Hahn, 1995). In the present experiments, the spatial distribution of attention was assessed by a novel method, perceptual latency priming: the latency benefit of an attended visual stimulus, as compared with a nonattended stimulus. Experiment 1 assessed whether observers are able to attend to two nonadjacent regions or a region of variable size. Experiment 2 tested whether, when two distant locations are attended to, the region between them is necessarily also in the focus of attention. Two further experiments controlled for objections against the method used and replicated the main results of the first two experiments. The experiments showed a robust attentional priming effect at two noncontiguous locations of the visual field, simultaneous with little or no priming of the intervening location.

Frontal and temporal lobe sources for a marker of controlled auditory attention: the negative difference (Nd) event-related potential.

Frontal and temporal lobe sources for electrical activity associated with auditory controlled attention (negative difference, Nd) were sought for comparison with those reported to arise from the earlier detection of stimulus-change (mismatch negativity, MMN: Jemel et al. 2002). In two sessions a month apart (T1 and T2), 14 subjects were presented with a 3-tone oddball passively, then as a discrimination task. In EEG recordings (32 sites), Nd was calculated by subtraction of the event-related potential elicited by a non-attended stimulus from that after the same frequency-deviant as target Putative generators in the 180-228 ms latency-range were modelled with brain electrical source analysis and mapped to the modified Montreal brain-atlas. Initial T1-analyses located bilateral Nd dipoles in the superior temporal gyrus (BA22) and the dorsolateral prefrontal cortex (BA8). Re-test allowed estimates of the temporal and spatial extension of activity. Peak activity occurred 14 ms later. Step-by-stepanalysis showed that the best spatial fit for the inverse-solutions extended 3-6 mm from the point sources, but for temporal lobe sources this increased 15 mm caudally. The right mid-frontal source (BA10) was rostral and ventral from that in the left superior frontal gyrus (BAB). T1 and T2 dipole strengths were well correlated. Nd measures of controlled attention localised to areas associated with sustained attention, problem-solving and working-memory. Temporal lobe sources were later and more posterior and medial than for automatic change-detection. Frontal Nd sources were more dorsal on the right and more rostral on the left than MMN dipoles reported for the right inferior frontal and left anterior cingulate. The sequence of information processing is reviewed.

Neural correlates of object-based attention.

Much research has been directed toward disentangling the "units" of attention: Is attention directed to locations in space, visual objects, or to individual features of an object? Moreover, there is considerable interest in whether attention increases the gain of neural mechanisms (signal enhancement) or acts by other means, such as reducing noise or narrowing channel tuning. To address these questions, we used a direct measure of signal strength: the amplitude of visual evoked potentials and a task in which selection could be based on a depth order cue but not on location. Attended and nonattended stimuli were presented at different temporal frequencies, and, thus, responses to the two stimuli could be analyzed separately even though they were presented simultaneously. Attention increased the amplitude of the second harmonic component of the response, but not the fourth harmonic. In addition, responses measured at the second harmonic, but not at the fourth harmonic, were larger for stimuli seen as behind. The results are consistent with the fourth harmonic being generated at a stage of processing that is not accessible to attention and where depth order has not been extracted. The second harmonic, on the other hand, is modifiable by attention and shows evidence for differential encoding of depth order.