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PubMed2006

Attentional modulation of the amygdala varies with personality.

The amygdala is implicated in emotional processing, and its rich subcortical connections have led to suggestions that processing of emotional stimuli occurs independently of attention. Using a novel attentional manipulation in conjunction with fMRI, we showed that emotion-related amygdala activity was modulated by attention, but that the degree of such modulation correlated with the personality variable harm avoidance, associated with trait anxiety. Participants ignored emotional distractors while searching through a rapid stream of pictures for a target, about which they were provided either specific or nonspecific descriptive information (e.g., "look for a building" versus "look for a landscape or building"). Thus, they employed either a specific or a nonspecific attentional set in order to find the target and ignore distractors. In response to irrelevant emotional distractors, low harm-avoidant participants had relatively little emotion-related amygdala activity regardless of whether they maintained a specific or nonspecific attentional set. High harm-avoidant participants, however, showed strong emotion-related amygdala activity when maintaining a nonspecific attentional set and lower amygdala activity when maintaining a specific attentional set. This decrease was accompanied by increased activation of the rostral anterior cingulate cortex (ACC), which is often linked with the resolution of affective interference. In addition to demonstrating individual differences in attentional modulation of the amygdala, these results may indicate that the rostral ACC is sensitive to the increased effort that high harm-avoidant individuals must recruit in order to modulate amygdala responsivity.

Adult↗
PubMed2004

Hemodynamic differences in the activation of the prefrontal cortex: attention vs. higher cognitive processing.

Both simple attention tasks (e.g. letter cancellation) and most tasks of higher cognitive processing (e.g. word generation) are known to activate the dorsolateral prefrontal cortex (PFC). While attention and higher cognitive processing differ phenomenologically, with attention tasks requiring great subjective effort despite their simplicity, possible physiological differences in the activation of the PFC between the two types of cognitive processing have remained uninvestigated. Hemodynamic changes in the PFC during activation due to tasks of attention and those of higher cognitive processing were examined using near-infrared spectroscopy in 10 Japanese and 10 American healthy adults. In tasks of higher cognitive processing, which included both verbal and non-verbal tasks, the concentration of oxygenated hemoglobin ([HbO2]) increased, and that of deoxygenated hemoglobin ([HbR]) decreased, with an increase in the tissue hemoglobin saturation (THS). In tasks of attention, which consisted of the letter cancellation and continuous performance test, both [HbO2] and [HbR] increased, with no significant changes in the THS observed. The distinctive patterns of hemodynamic changes were not affected by the factors of task difficulty or language. The change in [HbR] may be a physiological marker of the prefrontal lobe activation that discriminates between attention and higher cognitive processing. The increase in [HbR] suggests increased oxygen consumption of the PFC during tasks of attention, which might be related to the disproportionately great subjective effort associated with sustained attention. The physiological alteration in hemodynamic patterns according to changes in cognition needs to be examined in subjects with prefrontal lobe dysfunction, such as schizophrenia and mood disorder.

Adolescent↗
PubMed2006

Attentional distraction reduces the affective but not the sensory dimension of perceived dyspnea.

The perception of dyspnea shows many similarities to the perception of pain. Both are multidimensional processes, which are not only influenced by sensory input but also by nonsensory factors like attention. Recent research has suggested that attentional distraction might reduce the perception of dyspnea but results are conflicting. Furthermore, the specific impact of attentional distraction on the distinct dimensions of perceived dyspnea has not been studied yet. Therefore, the present study examined the specific impact of changes in the attentional focus on the sensory and affective dimension of perceived dyspnea. Dyspnea was induced in forty-four healthy volunteers (mean age: 27.7 years, range: 18-47 years) by breathing through an inspiratory resistive load (3.57 kPa/L/s), while attention was directed either to breathing or distracted by reading texts. Inspiratory time (T(i)) and breathing frequency (f) were measured continuously. After each condition the experienced intensity (i.e., sensory dimension) and unpleasantness (i.e., affective dimension) of dyspnea were rated on separate visual analog scales (VAS), presented in randomized order. ANOVAs showed that attentional distraction during loaded breathing reduced the perceived unpleasantness of dyspnea (P<0.05), while the perceived intensity of dyspnea as well as T(i) and f remained unchanged. The results show that attentional distraction reduces the affective, but not the sensory dimension of induced dyspnea in healthy volunteers. Future studies are needed to clarify whether attentional distraction can effectively be used as intervention technique for reducing the unpleasant aspects of dyspnea in different patients groups.

Adolescent↗
PubMed2006

The speed of visual attention in schizophrenia: electrophysiological and behavioral evidence.

Schizophrenia is characterized by a substantial slowing of manual response times and by impairments in attention. However, prior research has not investigated whether attention itself is slowed in schizophrenia, and this was the goal of the present study. In Experiment 1, the N2pc component of the event-related potential waveform-an electrophysiological correlate of the focusing of attention-was recorded from 24 schizophrenia spectrum patients and 13 control subjects. Although behavioral response times were delayed by over 100 ms in the patient group, the onset latency of the N2pc component was virtually identical across groups, and no reduction in N2pc amplitude was observed in the patient group. In Experiment 2, a new cueing paradigm was developed to provide a behavioral measure of the speed of attention in 22 schizophrenia spectrum patients and 13 control subjects. We found that the average time required to allocate attention to a cued location was only 19 ms greater for the patient group than for the control group, with most patients within the range of the control subjects. Together, these experiments revealed little or no slowing of the allocation of visual-spatial attention in patients with schizophrenia. Thus, the mechanisms responsible for allocating attention to salient visual targets appear to be largely unaffected by the illness, and the well documented slowing of manual response times in schizophrenia cannot easily be explained by a slowing of attention.

Adult↗
PubMed2004

Effects of attention on motion repulsion.

Motion repulsion involves interaction between two directions of motion. Since attention is known to bias interactions among different stimuli, we investigated the effect of attentional tasks on motion repulsion. We used two overlapping sets of random dots moving in different directions. When subjects had to detect a small speed-change or luminance change for dots along one direction, the repulsive influence from the other direction was significantly reduced compared with the control case without attentional tasks. However, when the speed-change could occur to either direction such that subjects had to attend both directions to detect the change, motion repulsion was not different from the control. A further experiment showed that decreasing the difficulty of the attentional task resulted in the disappearance of the attentional effect in the case of attention to one direction. Finally, over a wide range of contrasts for the unattended direction, attention reduced repulsion measured with the attended direction. These results are consistent with the physiological finding that strong attention to one direction of motion reduces inhibitory effects from the other direction.

Attention↗
PubMed2006

Comparing the time course and efficacy of spatial and feature-based attention.

We investigated the time course of feature-based attention and compared it to the time course of spatial attention in an experiment with identical stimuli and task. Observers detected a speed increment in a compound motion stimulus preceded by cues that indicated either the target location or direction. The cue-target stimulus-onset-asynchrony (SOA) was varied to assess the time course of the attentional effect. We found that spatial attention was deployed earlier than feature-based attention and that both types of attention improved performance to a similar extent at a longer SOA. Results indicate that attention is a flexible mechanism allowing us to efficiently select task-relevant information based on either spatial or feature dimensions, but that spatial attention exert its effects faster.

Attention↗
PubMed1991

Attention, not anxiety, influences pain.

Four hypotheses about the influences of anxiety and attention on pain impact were tested in a critical experiment: (1) anxiety increases pain; (2) anxiety decreases pain; (3) attention to pain increases pain; (4) only the combination of anxiety and attention to pain increases pain (interaction hypothesis). In a 2 x 2 design, anxiety (low vs high) and attention (attention vs distraction from the pain) were experimentally manipulated. Subjects received 20 electrically produced painful stimuli. Subjective pain experiences, skin conductance responses and heart rate responses gave no support for a pain impact increasing effect of anxiety. The anxiety-attention interaction hypothesis did not receive any support either. There was some support, only from the heart rate responses, that anxiety reduces pain impact. The critical factor appeared to be attention. Attention to the pain stimulus was related to a stronger pain impact (indicated by all measures) and to less subjective habituation, compared to distraction.

Adolescent↗
PubMed2006

Verbal dichotic listening in right and left-handed adults: laterality effects of directed attention.

Dichotic listening performance of consonant vowel stimuli was studied in 51 adult right- and left-handers in three attention conditions: non-directed and directed to either the right or left ear. In the non-directed condition, a significant right-ear advantage was found in both handedness groups with a stronger asymmetry in right-handers. There are at least three explanations for this ear bias. The classic or structural hypothesis suggests that to the right ear projects more strongly to the language dominant left hemisphere. The callosal relay hypothesis is based on the influence of inhibitory connections via the corpus callosum. The attentional hypothesis suggests that each hemisphere primarily directs attention to contralateral space and because the left hemisphere is dominant for language in both groups, and is aroused by speech stimuli, attention is primarily directed to the right ear. Neither hypothesis can explain why greater than 95% of right-handers have left hemisphere language dominance, but only 70-80% have a right ear bias. Our results demonstrate that in the directed attention conditions both groups increased their lateral biases when directed to either the right or left. The classic or structural hypothesis cannot account for these changes, thereby providing support for the attentional hypothesis. In addition, the right-handed subjects exhibited a greater shift of bias than did the left-handed subjects, when directing their attention leftward. This finding suggests that right-handed people are better able to shift their attention than left-handed people.

Adult↗
PubMedDate not supplied

Differential impairment on measures of attention in patients with paranoid and nonparanoid schizophrenia.

The purpose of the present study is to investigate whether patients with different subtypes of schizophrenia are differentially impaired on measures of attention. Forty-eight patients with schizophrenia (19 paranoid and 29 nonparanoid) and 48 healthy controls (matched on chronological age, sex, and years of education) were administered five measures of attention including the Stroop Color-Word Test (SCWT; Stroop, 1935), the Digit Vigilance Test (DVT; Lewis, 1992), the Symbol Digit Modalities Test (SDMT; Smith, 1982), the Backward Digit Span Test (BDST; Wechsler, 1987), and the Color Trails Test (CTT; D'Elia et al., 1996) to assess selective attention, sustained attention, switching attention, and attentional control processing by the latter two tests respectively. Results from the present study showed that patients with schizophrenia performed poorer on the SCWT, the DVT, and the SDMT, relative to their healthy counterparts. Furthermore, patients with different subtypes of schizophrenia also had different degrees of attentional impairment. While patients with paranoid schizophrenia performed worse on the SCWT, those with nonparanoid schizophrenia performed worse on the SDMT. Nevertheless, these findings may suggest that patients with paranoid and nonparanoid schizophrenia may have different profiles with respect to their performances on measures of attention.

Adult↗
PubMed2001

Testing cognitive models of visual attention with fMRI and MEG.

Neuroimaging techniques can be used not only to identify the neural substrates of attention, but also to test cognitive theories of attention. Here we consider four classic questions in the psychology of visual attention: (i) Are some 'special' classes of stimuli (e.g. faces) immune to attentional modulation?; (ii) What are the information units on which attention operates?; (iii) How early in stimulus processing are attentional effects observed?; and (iv) Are common mechanisms involved in different modes of attentional selection (e.g. spatial and non-spatial selection)? We describe studies from our laboratory that illustrate the ways in which fMRI and MEG can provide key evidence in answering these questions. A central methodological theme in many of our fMRI studies is the use of analyses in which the activity in certain functionally-defined regions of interest (ROIs) is used to test specific cognitive hypotheses. An analogous sensor-of-interest (SOI) approach is applied to MEG. Our results include: evidence for the modulation of face representations by attention; confirmation of the independent contributions of object-based and location-based selection; evidence for modulation of face representations by non-spatial selection within the first 170 ms of processing; and implication of the intraparietal sulcus in functions general to spatial and non-spatial visual selection.

Attention↗
PubMed2002

Grey scales uncover similar attentional effects in homonymous hemianopia and visual hemi-neglect.

Multi-component models of visual hemi-neglect have postulated that visual hemi-neglect is characterised by various attentional deficits. A grey scales task has been developed to quantify the early, automatic, (perhaps obligatory) ipsilesional orienting of visual attention, frequently assumed as the first of these attentional deficits. Explanations for this attentional imbalance are up until now mainly formulated in terms of right hemisphere activation. This lateral attentional bias has also been demonstrated in controls, in whom it is expressed as a leftward perceptual asymmetry. We reproduced previous literature findings on a grey scales task, considering controls and neglect patients. Three patients with neglect showed an extreme ipsilesional lateral bias. This bias did not change during or after cognitive rehabilitation. Additionally, we presented this grey scale task to 32 patients with left- and right-sided homonymous hemianopia (HP). HP is the loss of sight in one visual hemi-field. The HH patients had no clinical signs of impaired lateralised attention. Results revealed that HH patients showed a similar ipsilesional bias, albeit to a lesser degree than in neglect. Left-sided HH patients presented a quantitatively similar, but qualitatively opposite bias than the right-sided HH patients. We suggest that sensory effects can be an alternative source of attentional imbalance, which can interact with the previously proposed (right) hemispheric effects. This suggests that the perceptual asymmetry in the grey scales task is not necessarily an indicator of impaired right hemisphere attention. It rather suggests a pattern of functional cerebral asymmetry, which can also be caused by asymmetric sensory input.

Adolescent↗
PubMed2002

Effects of divided attention on episodic memory in chronic traumatic brain injury: a function of severity and strategy.

Eleven patients with mild traumatic brain injury (MTBI) and 13 patients with moderate-to-severe TBI (STBI) were compared to 10 matched controls on episodic memory for pictorial scene-object associations (e.g. kitchen-bread) and a range of standardized neuropsychological tests of memory and frontal-lobe functions. We tested the hypothesis that deficits in episodic memory result from impaired attentional resources and/or strategic control by manipulating attentional load at encoding (focused versus divided attention) and environmental support at retrieval (free recall and recalled cued by scene versus recognition of object and scene). Patients with TBI were disproportionately affected by the divided attention manipulation, but this effect was modulated by injury severity and encoding strategy. Overall, MTBI patients were impaired only when items were encoded under divided attention, indicating memory deficits that were secondary to deficits in the executive control. STBI patients could be differentiated into two distinct functional subgroups based on whether they favored a strategy of attending to the encoding or digit-monitoring task. The subgroup favoring the digit-monitoring task demonstrated deficits in the focused attention condition, and disproportionate memory deficits in the divided attention condition. In contrast, the subgroup favoring the encoding task demonstrated intact performance across all memory measures, regardless of attentional load, and despite remarkable similarity to the other STBI subgroup on demographic, neuropsychological, and acute injury severity measures. We discuss these outcome differences in terms of the relationship between strategy and executive control and highlight the need for more sensitive anatomical and behavioral measurement at both acute and chronic stages of injury.

Adult↗
PubMed1997

The left parietal cortex and motor attention.

The posterior parietal cortex, particularly in the right hemisphere, is crucially important for covert orienting; lesions impair the ability to disengage the focus of covert orienting attention from one potential saccade target to another (Posner, M. I. et al., Journal of Neuroscience, 1984, 4, 1863-1874). We have developed a task where precues allow subjects to covertly prepare subsequent cued hand movements, as opposed to an orienting or eye movement. We refer to this process as motor attention to distinguish it from orienting attention. Nine subjects with lesions that included the left parietal cortex and nine subjects with lesions including the right parietal cortex were compared with control subjects on the task. The left hemisphere subjects showed the same ability as controls to engage attention to a movement when they were forewarned by a valid precue. The left hemisphere subjects, however, were impaired in their ability to disengage the focus of motor attention from one movement to another when the precue was incorrect. The results support the existence of two distinct attentional systems allied to the orienting and limb motor systems. Damage to either system causes analogous problems in disengaging from one orienting/movement target to another. The left parietal cortex, particularly the supramarginal gyrus, is associated with motor attention. All the left hemisphere subjects had ideomotor apraxia and had particular problems performing sequences of movements. We suggest that the well documented left hemisphere and apraxic impairment in movement sequencing is the consequence of a difficulty in shifting the focus of motor attention from one movement in a sequence to the next.

Adult↗
PubMed2001

Differential effect of attention to translation and expansion on motion aftereffects (MAE).

Recent fMRI findings have shown that selective attention to translating dots enhances V1 and MT complex activity whereas attention to expansion enhances MT complex activity rather than V1 (Watanabe et al., Proceedings of the National Academy of Sciences of the USA, (1998a) 95(19), 11489-11492). In order to clarify whether or not attention actually enhances the neural mechanism for the attended motion direction(s), we took advantage of the motion aftereffect (MAE), using superimposed groups of translating and expanding dots as the adaptation stimulus. During the adaptation stage, the subject was instructed to direct attention to one-way translation, expansion, or no particular motion or location, while gazing at the fixation point. The strength of the MAE in the attended monocular condition was greater than the sum of the unattended monocular MAE and the attended binocular MAE. In another experiment the monocular and binocular components showed linear additivity. These results suggest that attention enhances the monocular mechanism for the attended translational direction and that bottom-up monocular signals and top-down attentional signals simply add linearly. In contrast, no significant monocular contribution was found for attention to expansion. This is not only in accord with previous fMRI findings (Watanabe et al., 1998a), but also supports the thesis that attention to translation or expansion enhances the activation of the mechanism for the attended motion, rather than simply increasing arousal as a result of a heavier task load.

Adult↗
PubMed2001

Automatic gain control contrast mechanisms are modulated by attention in humans: evidence from visual evoked potentials.

This study investigated the effect of attention on the contrast response curves of steady-state visual evoked potentials (VEPs) to counter-phased sinusoidal gratings. The 1 cyc/deg gratings were modulated either in luminance or chromaticity (equiluminant red-green). The luminance grating counter-phased at 9 Hz (to favour activation of the magno-cellular system), and the chromatic grating at 2.5 Hz (to favour activation of the parvo-cellular system). Attention was directed towards the gratings (displayed in the left visual field) by requiring subjects to detect and respond to randomly occurring changes in contrast. In the control condition, attention towards the grating was minimised by requiring subjects to detect a target letter amongst distracters briefly flashed in the contra-lateral visual field. Attention increased VEP amplitudes for both luminance and chromatic stimuli, more so at high than at low contrasts, increasing the slope of the contrast amplitude curves (over the non-saturating range of contrasts). The estimates of contrast threshold from extrapolation of amplitudes were unaffected by attention. Attention also changed the VEP phases, but only for luminance gratings, where it acted to reduce the magnitude of phase advance with contrast. Attention had no effect on the average phases for chromatic gratings. The results are consistent with the notion that attention acts on cortical gain control mechanisms, which are known to be different for the magno- and parvo-cellular systems.

Adult↗
PubMed2006

Dynamics of emotional effects on spatial attention in the human visual cortex.

An efficient detection of threat is crucial for survival and requires an appropriate allocation of attentional resources toward the location of potential danger. Recent neuroimaging studies have begun to uncover the brain machinery underlying the reflexive prioritization of spatial attention to locations of threat-related stimuli. Here, we review functional brain imaging experiments using event-related potentials (ERPs) and functional magnetic resonance imaging (fMRI) in a dot-probe paradigm with emotional face cues, in which we investigated the spatio-temporal dynamics of attentional orienting to a visual target when the latter is preceded by either a fearful or happy face, at the same (valid) location or at a different (invalid) location in visual periphery. ERP results indicate that fearful faces can bias spatial attention toward threat-related location, and enhance the amplitude of the early exogenous visual P1 activity generated within the extrastriate cortex in response to a target following a valid rather than invalid fearful face. Furthermore, this gain control mechanism in extrastriate cortex (at 130-150 ms) is preceded by an earlier modulation of activity in posterior parietal regions (at 40-80 ms) that may provide a critical source of top-down signals on visual cortex. Happy faces produced no modulation of ERPs in extrastriate and parietal cortex. fMRI data also show increased responses in the occipital visual cortex for valid relative to invalid targets following fearful faces, but in addition reveal significant decreases in intraparietal cortex and increases in orbitofrontal cortex when targets are preceded by an invalid fearful face, suggesting that negative emotional stimuli may not only draw but also hold spatial attention more strongly than neutral or positive stimuli. These data confirm that threat may act as a powerful exogenous cue and trigger reflexive shifts in spatial attention toward its location, through a rapid temporal sequence of neural events in parietal and temporo-occipital areas, with dissociable neural substrates for engagement benefits in attention affecting activity in extrastriate occipital areas and increased disengagement costs affecting intraparietal cortex. These brain-imaging results reveal how emotional signals related to threat can play an important role in modulating spatial attention to afford flexible perception and action.

Attention↗
PubMed2001

Crossmodal links in endogenous and exogenous spatial attention: evidence from event-related brain potential studies.

The adaptive control of behaviour in response to relevant external objects and events often requires the selection of information delivered by different sensory systems, but from the same region in external space. This can be facilitated by crossmodal links in the attentional processing of information across sensory modalities. Results from recent event-related potential (ERP) studies are reviewed that investigated mechanisms underlying such crossmodal links in spatial attention between vision, audition and touch. Crossmodal attention effects were observed for early modality-specific visual, auditory, and somatosensory ERP components, indicating that crossmodal links in spatial attention affect sensory-perceptual processes within modality-specific cortical regions. ERP modulations prior to target events but sensitive to the direction of an attentional shift were remarkably similar during anticipatory covert shifts of visual, auditory, or tactile attention. These results suggest that such attentional shifts are mediated by supramodal frontoparietal control mechanisms. Finally, ERP evidence is reviewed suggesting that effects of crossmodal links in endogenous (voluntary) as well as exogenous (involuntary) spatial attention are mediated by a representations of external space which are updated across postural changes.

Animals↗
PubMed1994

Electrophysiological correlates to cued attentional shifts in the visual and auditory modalities.

Reaction time (RT) is usually speeded and slowed to correctly and incorrectly cued target stimuli, respectively, in experiments on attention shift (Posner, 1988). When targets occur in a spatial location different from the cue, shifting attention from the cued location to the target location involves interrupt of ongoing activity, move attention to the new location, and reengage attention. The present study investigated whether the cognitive operations involved in cued vs uncued attentional shifts also were detectable in the event-related potentials (ERPs). Two experiments are reported, one with visual and one with auditory stimuli. In the visual modality, the cue and target were a lit-up square and an asterisk, respectively, shown on a computer screen. In the auditory modality, the cue was a tone in either the left or right ear, followed by the target noise in either the same or the opposite ear. The results from the visual experiment showed shorter RTs to correctly cued (Valid) targets and longer RTs to incorrectly cued (Invalid) targets. Invalidly cued targets elicited enhanced P3 amplitudes, with a frontocentral distribution. Reduced P3 amplitudes were observed on Valid trials, largest reduction for parietooccipital leads. The auditory experiment showed P3 enhancement frontally and reduced amplitudes at temporal and parietal leads. No RT differences were seen to Valid and Invalid trials. The existence of an anterior attention system involved in interrupt and disengage of attention, and a posterior attention facilitation system related to cue presentation is discussed.

Adult↗