Dissociation of response conflict, attentional selection, and expectancy with functional magnetic resonance imaging

Two different attentional networks have been associated with visuospatial attention and conflict resolution. In most situations either one of the two networks is active or both are increased in activity together. By using functional magnetic resonance imaging and a flanker task, we show conditions in which one network (anterior attention system) is increased in activity whereas the other (visuospatial attention system) is reduced, showing that attentional conflict and selection are separate aspects of attention. Further, we distinguish between neural systems involved in different forms of conflict. Specifically, we dissociate patterns of activity in the basal ganglia and insula cortex during simple violations in expectancies (i.e., sudden changes in the frequency of an event) from patterns of activity in the anterior attention system specifically correlated with response conflict as evidenced by longer response latencies and more errors. These data provide a systems-level approach in understanding integrated attentional networks.

Positron-emission tomography studies of cross-modality inhibition in selective attentional tasks: closing the "mind's eye".

It is a familiar experience that we tend to close our eyes or divert our gaze when concentrating attention on cognitively demanding tasks. We report on the brain activity correlates of directing attention away from potentially competing visual processing and toward processing in another sensory modality. Results are reported from a series of positron-emission tomography studies of the human brain engaged in somatosensory tasks, in both "eyes open" and "eyes closed" conditions. During these tasks, there was a significant decrease in the regional cerebral blood flow in the visual cortex, which occurred irrespective of whether subjects had to close their eyes or were instructed to keep their eyes open. These task-related deactivations of the association areas belonging to the nonrelevant sensory modality were interpreted as being due to decreased metabolic activity. Previous research has clearly demonstrated selective activation of cortical regions involved in attention-demanding modality-specific tasks; however, the other side of this story appears to be one of selective deactivation of unattended areas.

Inactivation of the superior cerebellar peduncle blocks expression but not acquisition of the rabbit's classically conditioned eye-blink response.

The localization of sites of memory formation within the mammalian brain has proven to be a formidable task even for simple forms of learning and memory. Recent studies have demonstrated that reversibly inactivating a localized region of cerebellum, including the dorsal anterior interpositus nucleus, completely prevents acquisition of the conditioned eye-blink response with no effect upon subsequent learning without inactivation. This result indicates that the memory trace for this type of learning is located either (i) within this inactivated region of cerebellum or (ii) within some structure(s) efferent from the cerebellum to which output from the interpositus nucleus ultimately projects. To distinguish between these possibilities, two groups of rabbits were conditioned (by using two conditioning stimuli) while the output fibers of the interpositus (the superior cerebellar peduncle) were reversibly blocked with microinjections of the sodium channel blocker tetrodotoxin. Rabbits performed no conditioned responses during this inactivation training. However, training after inactivation revealed that the rabbits (trained with either conditioned stimulus) had fully learned the response during the previous inactivation training. Cerebellar output, therefore, does not appear to be essential for acquisition of the learned response. This result, coupled with the fact that inactivation of the appropriate region of cerebellum completely prevents learning, provides compelling evidence supporting the hypothesis that the essential memory trace for the classically conditioned eye-blink response is localized within the cerebellum.

Attentional processes associated with victimization history and posttraumatic symptomatology in women exposed to intimate partner violence

Exposure to intimate partner violence (IPV) puts women at risk for severe and chronic physical and mental health consequences, including elevations in IPV-related psychopathology and increased risk for future victimization. Previous research has examined attention as one of the key information processing mechanisms associated with elevated psychopathology and risk for victimization; however, the nature of attentional processing in response to IPV-related information in women exposed to IPV is poorly understood. Therefore, the current study aimed to further understanding of associations between attentional processing, IPV exposure, and related distress using measures of eye movement and subjective interpretations of IPV-related information. A sample of women exposed to IPV (n = 57) viewed sets of negative, positive, and neutral relationship images for 15 s each while having their eye movements monitored and later provided subjective ratings and interpretations of levels of risk and safety in those images. We examined associations of outcome measures with proximal victimization experiences and IPV-related psychopathology (i.e., depression, posttraumatic stress disorder (PTSD), anxiety, and dissociation). Results indicated a bias to attend to negative relationship images relative to positive and neutral images, though this attention bias fluctuated over time and varied as a function of symptomatology such that depression corresponded with increases in attention to negative images over time and PTSD corresponded with decreases in attention to negative images. The general attention bias for negative images appeared to be explained by rumination on and/or difficulty disengaging from negative images, which was related to general elevations in psychopathology as well as exposure to revictimization by different perpetrators. Subjective interpretations and perception of danger cues were related to victimization history and level and type of IPV-related distress. We replicated these procedures with a sample of undergraduate students without IPV histories or related symptomatology (n = 33) and found that the overall attention bias for negative images was not replicated, despite general similarities in patterns of attention over time. Results therefore indicated associations between attentional processing and IPV exposure and related symptomatology. Implications for models of IPV-related psychopathology and attentional processing as well as directions for future study and interventions are discussed.

A high-resolution binocular video-oculography system: assessment of pupillary light reflex and detection of an early incomplete blink and an upward eye movement

Background: The pupillary light reflex characterizes the direct and consensual response of the eye to the perceived brightness of a stimulus. It has been used as indicator of both neurological and optic nerve pathologies. As with other eye reflexes, this reflex constitutes an almost instantaneous movement and is linked to activation of the same midbrain area. The latency of the pupillary light reflex is around 200 ms, although the literature also indicates that the fastest eye reflexes last 20 ms. Therefore, a system with sufficiently high spatial and temporal resolutions is required for accurate assessment. In this study, we analyzed the pupillary light reflex to determine whether any small discrepancy exists between the direct and consensual responses, and to ascertain whether any other eye reflex occurs before the pupillary light reflex. Methods: We constructed a binocular video-oculography system two high-speed cameras that simultaneously focused on both eyes. This was then employed to assess the direct and consensual responses of each eye using our own algorithm based on Circular Hough Transform to detect and track the pupil. Time parameters describing the pupillary light reflex were obtained from the radius time-variation. Eight healthy subjects (4 women, 4 men, aged 24–45) participated in this experiment. Results: Our system, which has a resolution of 15 microns and 4 ms, obtained time parameters describing the pupillary light reflex that were similar to those reported in previous studies, with no significant differences between direct and consensual reflexes. Moreover, it revealed an incomplete reflex blink and an upward eye movement at around 100 ms that may correspond to Bell’s phenomenon. Conclusions: Direct and consensual pupillary responses do not any significant temporal differences. The system and method described here could prove useful for further assessment of pupillary and blink reflexes. The resolution obtained revealed the existence reported here of an early incomplete blink and an upward eye movement.

Blink rate as a measure of fatigue: a review.

Federal Aviation Administration, Washington, D.C.

The role of semantic context and attentional resource distribution in semantic comprehension in Swedish pre-schoolers

Research on semantic processing focused mainly on isolated units in language, which does not reflect the complexity of language. In order to understand how semantic information is processed in a wider context, the first goal of this thesis was to determine whether Swedish pre-school children are able to comprehend semantic context and if that context is semantically built up over time. The second goal was to investigate how the brain distributes attentional resources by means of brain activation amplitude and processing type. Swedish preschool children were tested in a dichotic listening task with longer children’s narratives. The development of event-related potential N400 component and its amplitude were used to investigate both goals. The decrease of the N400 in the attended and unattended channel indicated semantic comprehension and that semantic context was built up over time. The attended stimulus received more resources, processed the stimuli in more of a top-down manner and displayed prominent N400 amplitude in contrast to the unattended stimulus. The N400 and the late positivity were more complex than expected since endings of utterances longer than nine words were not accounted for. More research on wider linguistic context is needed in order to understand how the human brain comprehends natural language. 

Attentional bias toward fear-related stimuli: An investigation with nonselected children and adults and children with anxiety disorders

Research investigating anxiety-related attentional bias for emotional information in anxious and nonanxious children has been equivocal with regard to whether a bias for fear-related stimuli is unique to anxious children or is common to children in general. Moreover, recent cognitive theories have proposed that an attentional bias for objectively threatening stimuli may be common to all individuals, with this effect enhanced in anxious individuals. The current study investigated whether an attentional bias toward fear-related pictures could be found in nonselected children (n = 105) and adults (n = 47) and whether a sample of clinically anxious children (n = 23) displayed an attentional bias for fear-related pictures over and above that expected for nonselected children. Participants completed a dot-probe task that employed fear-related, neutral, and pleasant pictures. As expected, both adults and children showed a stronger attentional bias toward fear-related pictures than toward pleasant pictures. Consistent with some findings in the childhood domain, the extent of the attentional bias toward fear-related pictures did not differ significantly between anxious children and nonselected children. However, compared with nonselected children, anxious children showed a stronger attentional bias overall toward affective picture stimuli. (C) 2004 Elsevier Inc. All rights reserved.

The effects of lead stimulus and reflex stimulus modality on modulation of the blink reflex at very short, short, and long lead intervals

The blink reflex is modulated if a weak lead stimulus precedes the blink-eliciting stimulus. In two experiments, we examined the effects of the sensory modality of the lead and blink-eliciting stimuli on blink modulation. Acoustic, visual, or tactile lead stimuli were followed by an acoustic (Experiment 1) or an electrotactile (Experiment 2) blink-eliciting stimulus at lead intervals of -30, 0, 30, 60, 120, 240, 360, and 4,500 msec. The inhibition of blink magnitude at the short (60- to 360-msec) lead intervals and the facilitation of blink magnitude at the long (4,500-msec) lead interval observed for each lead stimulus modality was relatively unaffected by the blink-eliciting stimulus modality. The facilitation of blink magnitude at the very short (-30- to 30-msec) lead intervals was dependent on the combination of the lead and the blink-eliciting stimulus modalities. Modality specific and nonspecific processes operate at different levels of perceptual processing.

Attentional bias to pictures of fear-relevant animals in a dot probe task

Attentional bias to fear-relevant animals was assessed in 69 participants not preselected on self-reported anxiety with the use of a dot probe task showing pictures of snakes, spiders, mushrooms, and flowers. Probes that replaced the fear-relevant stimuli (snakes and spiders) were found faster than probes that replaced the non-fear-relevant stimuli, indicating an attentional bias in the entire sample. The bias was not correlated with self-reported state or trait anxiety or with general fearfulness. Participants reporting higher levels of spider fear showed an enhanced bias to spiders, but the bias remained significant in low scorers. The bias to snake pictures was not related to snake fear and was significant in high and low scorers. These results indicate preferential processing of fear-relevant stimuli in an unselected sample.

The association between early minor motor difficulties in extreme low birth weight infants and school age attentional difficulties

Introduction: Extremely premature infants of normal intellectual ability have an increased prevalence of motor and attentional difficulties. Knowledge of the relationship between early motor difficulties and measures of attention at school age would enhance understanding of these developmental pathways, their interrelationship and opportunities for intervention. Objective: This study examines whether an association exists between early findings of minor motor difficulties and school age clinical and psychometric measures of attention. Methodology: 45/60 eligible ELBW(1000 g) or preterm (< 27/40 gestation) infants born at the Mater Mother's Hospital were assessed at 12 and 24 months for minor motor deficits (using NSMDA) and at 7-9 years for attention, using clinical (Conners and Du Paul Rating Scales) and psychometric (assessing attention span, selective and divided attention) measures. Results: NSMDA at 12 months was only associated with the psychometric measures of verbal attention span. It was not associated with later clinical measures of attention. NSMDA at 24months was strongly associated with specific clinical measures of attention at school age, independent of biological and social factors. It was not associated with psychometric measures of attention. Conclusion: The major finding of this study is that motor difficulties in ELBW infants at 2 years are associated with later clinical measures of attention. Possible mechanisms underlying this relationship are considered. Crown Copyright (c) 2005 Published by Elsevier Ireland Ltd. All rights reserved.

Covariation and interference between physiological reflexes: Eye-blink startle cardiac defense, and skin conductance

Comparative studies of autonomic and somatic reflexes, such as cardiac defense and motor startle, are rare. However, examination of the pattern of covariation, independence, or interference among physiological reflexes may help to clarify their functional significance and elucidate their complex modulation by psychological factors. Here we report the results of a study that examined the pattern of interference of eye-blink startle on subsequent cardiac defense. Participants were 63 students (31 women) distributed into three groups according to the sensory modality of the eliciting stimulus during the startle trials: acoustic high intensity (105 dB), acoustic low intensity (65 dB), and visual modality. Startle trials consisted of 12 presentations of the eliciting stimulus with a duration of 50 ms, instantaneous risetime, and a variable inter-stimulus interval of 16 – 20 s.Defense trials began 20 s after the last startle trial and consisted, for all groups, of 3 presentations of the high intensity acoustic stimulus with a duration of 500 ms and an inter-stimulus interval of 215 s. Results showed a clear interference of the startle trials on the subsequent defense trials when both types of trials shared identical sensory modality (acoustic) independently of intensity: the expected pattern of cardiac defense in the first trial only appeared in the visual modality. Similar interference effects were observed in the skin conductance response. Subjective reactivity to the defense stimulus did not detect differences between conditions.

Acquisition of negative valence and modified attentional processing by non fear relevant stimuli

The current research examined valence and attentional processing of a priori fear relevant stimuli and investigated the extent to which these characteristics can be acquired by non fear relevant stimuli across an aversive learning episode. The first experiment compared pictures of snakes and spiders with pictures of birds and fish using affective priming, visual search and detection of a dot probe. Snakes and spiders were more negative than birds and fish as indexed by affective priming, and were preferentially attended to in the visual search task. The second experiment exposed the non fear relevant animal pictures, birds and fish, in an aversive learning episode involving an aversive shock US. Skin conductance responding was measured during acquisition. After acquisition, conditioned non fear relevant animal stimuli, CS1, and non conditioned, non fear relevant animal stimuli, CS, were compared across affective priming, visual search and dot probe tasks. During acquisition, skin conductance responses were larger during CS1 than during CS across all three response intervals. After acquisition, CS1 non fear relevant animal pictures were more negative than CS non fear relevant animal pictures as indexed by affective priming, and were preferentially attended to in a dot probe task. These studies provide evidence that negative valence and modified attentional processing can be acquired in a brief aversive learning episode.

Effects of reflex stimulus intensity and stimulus onset asynchrony on prepulse inhibition and perceived intensity of the blink-eliciting stimulus

Prepulse inhibition of the blink reflex is widely applied to investigate information processing deficits in schizophrenia and other psychiatric patient groups. The present experiment investigated the hypothesis that prepulse inhibition reflects a transient process that protects preattentive processing of the prepulse. Participants were presented with pairs of blinkeliciting noises, some preceded by a prepulse at a variable stimulus onset asynchrony (SOA), and were asked to rate the intensity of the second noise relative to the first. Inhibition of blink amplitude was greater for a 110-dB (A) noise than for a 95-dB(A) noise with a 120-ms SOA, whereas there was no difference with a 30-ms SOA. The perceived intensity was also lower for the 110-dB(A) noise than for the 95-dB(A) noise with the 120-ms SOA, but not with the 30-ms SOA. The parallel results support a relationship between prepulse inhibition of response amplitude and perceived intensity. However, the prepulse did not reduce intensity ratings relative to control trials in some conditions, suggesting that prepulse inhibition is not always associated with an attenuation of the perceived impact of the blink-eliciting stimulus.