Effects of total sleep deprivation on components of top-down attentional control using a flexible attentional control task

Sleep deprivation consistently decreases vigilant attention, which can lead to difficulty in performing a variety of cognitive tasks. However, sleep-deprived individuals may be able to compensate for degraded vigilant attention by means of top-down attentional control. We employed a novel task to measure the degree to which individuals overcome impairments in vigilant attention by using top-down attentional control, the Flexible Attentional Control Task (FACT). The FACT is a two-choice task that has trials with valid, invalid, and neutral cues, along with an unexpected switch in the probability of cue validity about halfway in the task. The task provides indices that isolate performance components reflecting vigilant attention and top-down attentional control. Twelve healthy young adults completed an in-laboratory study. After a baseline day, the subjects underwent 39 hours of total sleep deprivation (TSD), followed by a recovery day. The FACT was administered at 03:00, 11:00, and 19:00 during sleep deprivation (TSD condition) and at 11:00 and 19:00 after baseline sleep and at 11:00 after recovery sleep (rested condition). When rested, the subjects demonstrated both facilitation and interference effects on cued trials. While sleep deprived, the subjects showed vigilant attention deficits on neutral cue trials, and an impaired ability to reduce these deficits by using predictive contextual cues. Our results indicate that the FACT can dissociate vigilant attention from top-down attentional control. Furthermore, they show that during sleep deprivation, contextual cues help individuals to compensate partially for impairments in vigilant attention, but the effectiveness of top-down attentional control is diminished.     

Effects of the cholinergic agonist nicotine on reorienting of visual spatial attention and top-down attentional control

The cholinergic agonist nicotine facilitates detection of invalidly cued trials in location-cueing paradigms and reduces the associated neural activity in human inferior parietal cortex. By using functional magnetic resonance imaging we test the hypothesis that the nicotinic modulation of attentional reorienting may result from reduced use of top-down information derived from prior cues. In a within subjects design non-smoking volunteers were given either placebo or nicotine (Nicorette 2 mg gum) prior to performing a cued target discrimination task. Attention was either validly (80%) or invalidly (20%) cued to the right or left visual hemifield. The difference in reaction times to invalidly and validly cued targets is termed the 'validity effect' and indicates the costs for attentional reorienting. Nicotine reduced the validity effect and reorienting-related neural activity in right inferior parietal cortex. Further regions consistently modulated in their activity by nicotine were the right middle temporal gyrus, left middle frontal gyrus, left parahippocampal gyrus and right cerebellum. The effects of nicotine upon top-down modulation were investigated by comparing occipital activity when attending to the right vs. left visual hemifield under placebo and nicotine. If nicotine reduced the use of top-down information attentional modulation in occipital cortex should be smaller under nicotine as compared with placebo. Even though an attention-related modulation of neural activity was observed in the fusiform and middle occipital gyrus we found no evidence for differences in attentional modulation under placebo and nicotine. Our data support a role of nicotinic cholinergic receptors in facilitating several subcomponents of attentional reorienting via modulation of right inferior parietal, temporal and frontal brain activity. In contrast, the findings in the occipital cortex do not support the hypothesis that the effects of nicotine on attentional reorienting are due to reduced reliance on top-down information derived from prior cues.     

Deficits in attentional control: cholinergic mechanisms and circuitry-based treatment approaches

The cognitive control of attention involves maintaining task rules in working memory (or "online"), monitoring reward and error rates, filtering distractors, and suppressing prepotent, and competitive responses. Weak attentional control increases distractibility and causes attentional lapses, impulsivity, and attentional fatigue. Levels of tonic cholinergic activity (changes over tens of seconds or minutes) modulate cortical circuitry as a function of the demands on cognitive control. Increased cholinergic modulation enhances the representation of cues, by augmenting cue-evoked activity in thalamic glutamatergic afferents, thereby increasing the rate of detection. Such cholinergic modulation is mediated primarily via α4β2* nicotinic acetylcholine receptors. Animal experiments and clinical trials in adult patients with ADHD indicate that attentional symptoms and disorders may benefit from drugs that stimulate this receptor. Tonic cholinergic modulation of cue-evoked glutamatergic transients in prefrontal regions is an essential component of the brain's executive circuitry. This circuitry model guides the development of treatments of deficits in attentional control.     

Volitional saccades and attentional mechanisms in schizophrenia patients and healthy control subjects

Schizophrenia (SZ) patients showed increased volitional saccade latencies, suggesting deficient volitional initiation of action. Yet increased volitional saccade latencies may also result from deficits in attention shifts. To dissociate attention shifting and saccade initiation, we asked 25 SZ patients and 25 healthy subjects to make saccades toward newly appearing (onset) targets and toward the loci of disappearing (offset) targets. Similar onsets and offsets were also used as attention cues in a Posner-type manual task. As expected, onsets and offsets had similar effects on attention. In contrast, saccade latencies were considerably longer with offset compared to onset targets, reflecting additional time for volitional saccade initiation. Unexpectedly, SZ patients had normal saccade latencies. Presumably, the expected deficit was compensated by decreased fixation-related neural activity, which was induced by the disappearance of fixation stimuli.     

The human pulvinar and stimulus-driven attentional control

The present study compared the behavioral effects of sudden motion onsets or color changes (i.e., featural changes) with the effects of new objects (i.e., multiple changes). Experiments 1 and 2 showed that lesions of the pulvinar affect stimulus-driven attentional control only when it is triggered by featural changes, but not by new objects. Experiment 3 revealed that when appended on a new object, a featural change is processed as a part of a more massive new object: Its attentional effects are larger and remain undisturbed by lesions of the pulvinar. In Experiment 4 a temporal superiority effect was found for featural changes, but not for new objects in healthy subjects. These results suggest that featural changes and new objects may be processed through different pathways and that the pulvinar may be particularly involved in stimulus-driven attentional control by sudden events entailing featural changes.     

Importance of attentional mechanisms in audiovisual links

 The effect of auditory cues at different levels of visual processing was examined by using a visual ”conjunction of features” discrimination task (experiment 1) and a ”feature” discrimination task (experiment 2). In both experiments the visual target, appearing either on the left or the right of Ss’ midline, was preceded by a brief tone either spatially proximal or distal to the target. In the ”conjunction” task, subjects had to discriminate the orientation of a T flanked with T distractors of different orientations. In this task, assumed to require focused attention, discrimination accuracy was increased when the sound cue occurred at the subsequent visual target location and was decreased when it occurred at its alternative location. In the ”feature” experiment, subjects had to discriminate the orientation of a line segment (±45°) presented among line segment distractors. Accuracy was not affected, either when the sound was proximal or when it was distal to the location of the visual target. Results suggest that the early processing of sensory information is modality specific and that interference of auditory stimulation with visual stimuli is more pronounced as the processing of visual stimuli requires focused attention. Received: 5 June 1998 / Accepted: 12 January 1999     

A distributed neural system for top-down face processing

Evidence suggests that the neural system associated with face processing is a distributed cortical network containing both bottom-up and top-down mechanisms. While bottom-up face processing has been the focus of many studies, the neural areas involved in the top-down face processing have not been extensively investigated due to difficulty in isolating top-down influences from the bottom-up response engendered by presentation of a face. In the present study, we used a novel experimental method to induce illusory face-detection. This method allowed for directly examining the neural systems involved in top-down face processing while minimizing the influence of bottom-up perceptual input. A distributed cortical network of top-down face processing was identified by analyzing the functional connectivity patterns of the right fusiform face area (FFA). This distributed cortical network model for face processing includes both “core” and “extended” face processing areas. It also includes left anterior cingulate cortex (ACC), bilateral orbitofrontal cortex (OFC), left dorsolateral prefrontal cortex (DLPFC), left premotor cortex, and left inferior parietal cortex. These findings suggest that top-down face processing contains not only regions for analyzing the visual appearance of faces, but also those involved in processing low spatial frequency (LSF) information, decision-making, and working memory.     

Verbal instructions and top-down saccade control

Few studies have addressed the interaction between instruction content and saccadic eye movement control. To assess the impact of instructions on top-down control, we instructed 20 healthy volunteers to deliberately delay saccade triggering, to make inaccurate saccades or to redirect saccades—i.e. to glimpse towards and then immediately opposite to the target. Regular pro- and antisaccade tasks were used for comparison. Bottom-up visual input remained unchanged and was a gap paradigm for all instructions. In the inaccuracy and delay tasks, both latencies and accuracies were detrimentally impaired by either type of instruction and the variability of latency and accuracy was increased. The intersaccadic interval (ISI) required to correct erroneous antisaccades was shorter than the ISI for instructed direction changes in the redirection task. The word-by-word instruction content interferes with top-down saccade control. Top-down control is a time consuming process, which may override bottom-up processing only during a limited time period. It is questionable whether parallel processing is possible in top-down control, since the long ISI for instructed direction changes suggests sequential planning.     

Dopaminergic mechanisms of neural plasticity in respiratory control: transgenic approaches

Data supporting the hypothesis that dopamine-2 receptors (D(2)-R) contribute to time-dependent changes in the hypoxic ventilatory response (HVR) during acclimatization to hypoxia are briefly reviewed. Previous experiments with transgenic animals (D(2)-R 'knockout' mice) support this hypothesis (J. Appl. Physiol. 89 (2000) 1142). However, those experiments could not determine (1) if D(2)-R in the carotid body, the CNS, or both were involved, or (2) if D(2)-R were necessary during the acclimatization to hypoxia versus some time prior to chronic hypoxia, e.g. during a critical period of development. Additional experiments on C57BL/6J mice support the idea that D(2)-R are critical during the period of exposure to hypoxia for normal ventilatory acclimatization. D(2)-R in carotid body chemoreceptors predominate under control conditions to inhibit normoxic ventilation, but excitatory effects of D(2)-R, presumably in the CNS, predominate after acclimatization to hypoxia. The inhibitory effects of D(2)-R in the carotid body are reset to operate primarily under hypoxic conditions in acclimatized rats, thereby optimizing O(2)-sensitivity.     

Neurophysiological mechanisms in the emotional modulation of attention: the interplay between threat sensitivity and attentional control

Processing task-irrelevant emotional information may compromise attention performance, particularly among those showing elevated threat sensitivity. If threat-sensitive individuals are able to recruit attentional control to inhibit emotional processing, however, they may show few decrements in attention performance. To examine this hypothesis, attention performance was measured in three domains--alerting, orienting, and executive attention. Task-irrelevant fearful, sad, and happy faces were presented for 50 ms before each trial of the attention task to create a mildly competitive emotional context. Electroencephalographic recordings were made from 64 scalp electrodes to generate event-related potentials (ERPs) to the faces. Participants reporting high threat sensitivity showed enhanced ERPs thought to reflect emotional processing (P200) and attentional control (P100 and N200). Enhanced N200 following fearful faces was linked to sustained and even slightly improved executive attention performance (reduced conflict interference) among high threat-sensitive individuals, but with decrements in executive attention among low threat-sensitive individuals. Results are discussed in terms of cognitive processing efficiency and the balance between threat sensitivity and attentional control in relation to executive attention performance. Results may have implications for understanding automatic and voluntary attentional biases related to anxiety.     

Intactness of inhibitory attentional mechanisms following severe closed-head injury

Attentional problems are a common sequelae of closed-head injury (CHI). Research in the area of selective attention has pointed to the role of inhibitory mechanisms in the suppression of irrelevant information. In the current study, a negative priming paradigm was used to assess the inhibitory mechanisms of individuals suffering from a severe CHI. Twenty participants with severe CHIs (greater than 1 year postinjury) and 20 matched controls completed a negative priming task, as well as several other standardized tests of cognitive functioning. Within the negative priming task, 2 conditions were used to elicit information regarding facilitation by attended and ignored information and 1 condition was used to elicit inhibition of ignored information, as compared with a neutral control condition. Despite poorer performances on several tests of attention, there were no significant differences in the amount of inhibition displayed by the CHI participants as compared with the controls. Findings suggest that inhibitory processing deficits may not underlie the selective attention difficulties commonly seen following a severe CHI.     

Cerebellar control of saccadic eye movements: its neural mechanisms and pathways

Microstimulation studies on monkeys have shown that the cerebellar cortex which is related to saccadic function is located in lobules VIc and VII of the vermis. This vermal area is designated as the oculomotor vermis and characterized by low thresholds (less than 10 microA) and by saccade-related neuronal activity. The saccade evoked by the vermal stimulation has been shown to be the result of activation of Purkinje-cell axons. On the other hand, an anterograde WGA-HRP transport study has indicated that the Purkinje-cell axons of the oculomotor vermis terminate almost exclusively in a fatigial region which is designated as the fastigial oculomotor region (FOR). Microstimulation of the oculomotor vermis and the ventromedial aspect of the FOR results in saccades which differ in their horizontal directions, with vermal stimulation resulting in ipsilateral and fastigial stimulation resulting in contralateral saccades. Since the ipsilateral saccades evoked from the caudal part of the FN were suppressed by bicuculline, they were the results of stimulation of the Purkinje axons. It has been also shown that stimulation of the oculomotor vermis causes inhibition of FOR neurons. Furthermore, fastigial neurons bursting with saccades can be recorded only within the anatomical confines of the FOR. These data are consistent with the concept that signals from the vermis are transmitted to the saccadic nuclei of the brainstem via the FOR. Neurons in the FOR have been shown to project to various saccade-related nuclei, including the riMLF and PPRF. Some neurons in the FOR have divergent axon collaterals which terminate in both the vertical and horizontal preoculomotor nuclei. When the initial eye position is changed by stimulating the FN prior to visually-guided saccades, monkeys cannot compensate for the stimulation-induced movement. When the stimulation is delived 75-130 ms after the target presentation, saccades are triggered prematurely. The visuomotor processing for saccades seems to be completed during this period, which is approximately half the latency of normal saccades. When saccades were triggered prematurely at an early stage of information processing, the eyes moved first in the direction of evoked saccade and then changed the direction toward the location of the target without any intervening period. The retinal error information sampled before the stimulation was not disturbed by the cerebellar stimulation. These observations suggest that cerebellar output impulses are projected downstream to saccade-programming circuits where visual information has already been converted into motor-command signals. The cerebellum is a domain for parallel processing of visuomotor information.     

Trait anxiety and the dynamics of attentional control

According to recent theoretical approaches dispositional anxiety is fundamentally linked to neural mechanisms of cognitive control ( [Braver et al., 2007] and [Eysenck et al., 2007]). The present study was conducted to further investigate this topic by focusing on the relation between trait anxiety, conflict-processing and dynamic adjustments in attentional allocation. Participants completed a modified version of the face-word Stroop task while an electroencephalogram was recorded. We analyzed behavioral and electrophysiological correlates of conflict processing and conflict-driven modulations in target and distractor processing. Anxiety was not related to general conflict-sensitivity but to individual differences in conflict-driven adjustments in attentional allocation: following a high level of stimulus-response conflict, highly anxious participants allocated more attentional resources to the processing of predominantly task-relevant information and withdrew attention from the processing of predominantly task-irrelevant information. Thus, trait anxiety appears to be closely related to individual differences in dynamic adjustments of attentional control.     

Opposite effect of conflict context modulation on neural mechanisms of cognitive and affective control

This study investigated the neural effect of conflict context modulation of cognitive and affective conflict processing by recording evoked‐response potentials in cognitive and affective versions of a flanker task. By varying the proportion of congruent and incongruent trials in a block, we found different patterns of the context effect on evoked potentials during cognitive and affective conflict processing. For posterior N1 amplitude, frequent incongruent trials produced a larger effect only in the affective task. The opposite pattern of the context effect was observed for the central N450, which was enhanced by frequent cognitive but reduced by frequent affective contexts. We found similar context effect on the parietal sustained potential in both tasks. Overall, our findings suggest that cognitive and affective conflict processing engage a context‐dependent attentional control mechanism but a common conflict response system.     

Inhibition versus attentional momentum in cortical and collicular mechanisms of IOR

Inhibition of return (IOR)-the automatic bias against returning attention or gaze to recently visited locations-is thought to have both collicular and cortical components and has been associated with the oculomotor system. Recently, distinct IOR mechanisms have been revealed that may have collicular and cortical origins: While standard luminance stimuli cause IOR in both manual and saccadic eye movement responses, "S cone" stimuli, which are invisible to the direct collicular pathway, caused manual IOR but not saccadic IOR. However, it has not been shown that the separate mechanisms are both inhibition of return, rather than facilitation due to attentional momentum or a visual motion transient. Here, we examined this question using four target and cue locations instead of two. Inhibition at the cued location predicts that responses for all noncued locations should be similar, whereas facilitation at the location opposite the cue predicts that the perpendicular locations would be more similar to the cued location than to the opposite location. Our results conform to the former prediction for both saccadic IOR and S cone generated IOR, demonstrating that both mechanisms of IOR are indeed inhibitory.     

The neural mechanisms of percept-memory comparison in visual working memory

The perception of internal bodily signals (interoception) plays a relevant role for emotion processing and feelings. This study investigated changes of interoceptive awareness and cardiac autonomic activity induced by short-term food deprivation and its relationship to hunger and affective experience. 20 healthy women were exposed to 24 h of food deprivation in a controlled setting. Interoceptive awareness was assessed by using a heartbeat tracking task. Felt hunger, cardiac autonomic activity, mood and subjective appraisal of interoceptive sensations were assessed before and after fasting. Results show that short-term fasting intensifies interoceptive awareness, not restricted to food cues, via changes of autonomic cardiac and/or cardiodynamic activity. The increase of interoceptive awareness was positively related to felt hunger. Additionally, the results demonstrate the role of cardiac vagal activity as a potential index of emotion related self-regulation, for hunger, mood and the affective appraisal of interoceptive signals during acute fasting.