High Conflict Conditions Research Articles

Math anxiety and deficient executive control: does reappraisal modulate this link?

The literature suggests an interplay between executive control functions and emotion regulation processes, with each playing a key role in math anxiety. We examined the relation between the use of two different emotion regulation strategies (reappraisal and suppression) and the ability to reduce emotional interference in high‐conflict situations (i.e., executive control of attention) in cases of math anxiety. A sample of 107 adults completed emotion regulation tendencies and math anxiety questionnaires and performed a flanker task following the priming of a math‐related or negative word. The findings revealed: (1) highly math‐anxious individuals had difficulty controlling emotional distractions induced by math information, even as simple as math‐related words, in high‐conflict conditions; and (2) the tendency to use reappraisal in everyday situations was associated with math‐anxious individuals’ ability to avoid heightened emotional reactions when encountering math‐related (i.e., threatening) information. These findings point to the efficacy of reappraisal‐focused intervention and suggest an innovative mechanism through which reappraisal reduces emotional reactions and improves performance among math‐anxious individuals, indicating a new way to approach interventions for math anxiety.

ADHD and Interfering Thoughts in High and Low Conflict Conditions

Background: Individuals with an ADHD diagnosis have increased levels of interfering thoughts, especially in the form of mind wandering. This was mostly investigated in sustained attention tasks; hence it is unclear whether the findings are only due to their difficulties in those types of tasks. Moreover, it is unclear how the amount of control invested in the task will affect those differences between control and ADHD groups. Method: ADHD and matched control groups performed the Stroop task under high and low conflict conditions while measuring their interfering thoughts level. Results: Individuals with ADHD have more interfering thoughts compared to a control group even when they are able to change their control level according to the task conflict. Conclusion: Interfering thoughts are an independent predictor of ADHD impairments, observed regardless of the degree of control invested in the task.

Modulation of Amygdala Response by Cognitive Conflict in Adolescents with Conduct Problems and Varying Levels of CU Traits

Adolescents with conduct problems and low callous-unemotional traits are characterised by high levels of reactive aggression. Prior studies suggest that they can have exaggerated neural and behavioural responses to negative emotional stimuli, accompanied by compromised affect regulation and atypical engagement of prefrontal areas during cognitive control. This pattern may in part explain their symptoms. Clarifying how neurocognitive responses to negative emotional stimuli can be modulated in this group has potential translational relevance. We present fMRI data from a cognitive conflict task in which the requirement to visually scan emotional (vs. calm) faces was held constant across low and high levels of cognitive conflict. Participants were 17 adolescent males with conduct problems and low levels of callous-unemotional traits (CP/LCU); 17 adolescents with conduct problems and high levels of callous-unemotional traits (CP/HCU, who typically show blunted reactivity to fear), and 18 typically developing controls (age range 10–16). Control participants showed typical attenuation of amygdala response to fear relative to calm faces under high (relative to low) conflict, replicating previous findings in a healthy adult sample. In contrast, children with CP/LCU showed a reduced (left amygdala) or reversed (right amygdala) attenuation effect under high cognitive conflict conditions. Children with CP/HCU did not differ from controls. Findings suggest atypical modulation of amygdala response as a function of task demands, and raise the possibility that those with CP/LCU are unable to implement typical regulation of amygdala response when cognitive task demands are high.

Memory effects of conflict and cognitive control are processing stage-specific: evidence from pupillometry.

An increasing number of studies in the conflict/control and perceptual desirable difficulty literatures show memory benefits for information in high-conflict task situations. Recent work suggests that increased conflict does not produce a task-wide encoding benefit; rather, conflict must focus high-level attention on to-be-tested information to produce an encoding benefit. We used pupil dilation measures to directly assess this stage-specific model of conflict-encoding effects. We show clear performance costs of incongruency (slower RT and larger pupil dilation) with both semantic and response distractors, but show memory benefits only with semantic conflict. Further, when participants were encouraged to focus more (eliciting greater endogenous effort and control for all trials, not just incongruent trials), we observe larger and more similar pupil responses and reduced memory differences between high versus low semantic conflict conditions. These data confirm and extend a stage-specific model of conflict-encoding effects, with converging behavioural and physiological data.

Delta phase reset predicts conflict-related changes in P3 amplitude and behavior

When multiple competing responses are activated, we respond more slowly than if only one response is activated (response conflict). Conflict-induced slowing is reduced for consecutive high-conflict stimuli, an effect known as conflict adaptation. Verguts and Notebaert’s (2009) adaptation by binding theory suggests this is due to Hebbian learning of cognitive control, potentiated by the response of the locus coeruleus norepinephrine (NE) system. Phasic activity of the NE system can potentially be measured non-invasively in humans by recording the P3 component of the event-related potential (ERP), and the P3 is sensitive to conflict adaptation. Bouret and Sara’s (2005) network reset theory suggests that phasic NE might functionally reset ongoing large-scale network activity, generating synchronous neural population activity like the P3. To examine the possibility that network reset contributes to conflict effects in the P3, we recorded high-density EEG data while subjects performed a flanker task. As expected, conflict and conflict adaptation modulated P3 amplitudes. Brain-behavior correlation analyses indicated that activity during the rise of the P3 was related to RT and predicted RT differences due to conflict. More importantly, phase of delta oscillations not only predicted reaction time differences between low-conflict and high-conflict conditions, but delta phase reset also predicted the amplitude of the P3. Delta oscillations exhibited dominant peaks both pre and post-stimulus, and delta at stimulus onset predicted the post-stimulus ERP, in particular the N2 and P3. This result bridges human EEG with basic mechanisms suggested by computational neural models and invasive patient recordings, namely that salient cognitive events might reset ongoing oscillations leading to the generation of the phase-locked evoked potential. We conclude that partial phase reset is a cortical mechanism involved in monitoring the environment for unexpected events, and this response contributes to conflict effects in the ERP. These results are in line with theories that phasic NE release might reset ongoing cortical activity, leading to the generation of ERP components like the P3.

H. Ellenberger et le rêve du savoir. À propos de… « Ethno-psychiatrie. Édition critique d’Emmanuel Delille » d’Henri Ellenberger

Le trouble obsessionnel-compulsif (TOC) se caractérise par sa fréquence relativement élevée en population générale, son évolution généralement chronique, sa réponse souvent partielle aux stratégies thérapeutiques usuelles. Mieux en comprendre la physiopathologie représente alors un enjeu majeur. Les avancées les plus marquées ont été réalisées grâce aux techniques de neuro-imagerie fonctionnelle qui ont contribué à apporter un éclairage nouveau sur l’importance des boucles fronto-sous-corticales dans la pathogénie du TOC grâce à l’identification de certains processus dysfonctionnels, comme la flexibilité cognitive, l’inhibition comportementale ou la détection de l’erreur, actuellement reconnus pour jouer un rôle majeur dans l’expression clinique de cette affection psychiatrique. Un regard attentif a également été porté aux comportements répétitifs de vérification, qui représentent la forme de compulsions la plus fréquemment observée dans le TOC, avec l’identification de leurs déterminants anatomo-fonctionnels. Cette démarche de recherche permet de proposer aujourd’hui de nouvelles cibles corticales pour la stimulation cérébrale profonde, technique neurochirurgicale récemment utilisée pour prendre en charge les cas sévères et résistants de TOC.Obsessive-compulsive disorder (OCD) is characterized by: (i) a relatively high frequency in the general population; (ii) a chronic or recurrent course; and, (iii) a poor clinical response to conventional therapeutic strategies primarily consisting in the combination of serotonin reuptake inhibitors (SSRIs) and cognitive behavioral therapies (CBT). Better understand the pathophysiology of obsessive-compulsive disorder (OCD) is therefore a major issue in this context that could further serve to deep brain stimulation proposed for treating resistant cases of OCD. The most significant advances have been made thanks to the contribution of neuroimaging techniques helping identifying profound functional disturbances within the frontal-sub-cortical loops. It has been found in patients with OCD that there are an enhanced metabolic activity within several cortical and sub-cortical regions especially including the orbitofrontal and anterior cingulate cortices, the caudate nucleus and the thalamus, in either resting or symptom provocation conditions. Also, increased functional connectivity implicating both orbitofrontal and anterior cingulate cortices and the ventral caudate nucleus has been reported in OCD patients. Correlations have been established with the clinical severity of OCD and related anxiety. However, such functional abnormalities could be reversed in response to antidepressant treatments with SSRIs and CBT along with the improvement in OCD symptom intensity. These data contrast with the deficit in activation within various cortical areas, such as the ventrolateral prefrontal cortex, which was observed during the instrumental tasks specifically exploring either cognitive flexibility or behavioral inhibition. Importantly, this lack of cortical activation was associated with impaired behavioral performances in both OCD patients and unaffected first-degree relatives. However, overactivation within the supplementary motor area has been described, though assumed not to be sufficient to compensate the deterioration of behavioral inhibition observed in OCD patients. Hyperactivity was also found within the dorsal and rostral anterior cingulate cortex of the OCD patients in high-conflict conditions, especially when they have responded correctly to the given instruction, therefore reflecting the high level of uncertainty that drives them. Finally, repetitive checking behaviors represent the most frequently observed forms of compulsions in OCD patients. When placed in a potential situation of unrestricted repetitive checking, OCD patients experiencing daily checking compulsions show a greater number of verification and a longer response time for choice before checking than control subjects. Also, external error signals or checking behaviors have no impact on the degree of uncertainty, as evinced by an unchanged activity within the ventrolateral prefrontal cortex of OCD patients, when the choice is made at the subsequent trial. Taken together, these findings have contributed to shed new light on the importance of the cortico-sub-cortical loops in the pathogenesis of OCD by identifying some dysfunctional processes recognized today to play a major role in the clinical expression of OCD. They also offer the advantage to propose novel anatomical targets for neurosurgical procedures such as deep brain stimulation that is now considered as a promising therapeutic strategy for the management of resistant OCD.

Resting state functional connectivity and cognitive task-related activation of the human claustrum

Structural and functional analyses of the human claustrum, a poorly understood telencephalic gray matter structure, are hampered by its sheet-like anatomical arrangement. Here, we first describe a functional magnetic resonance imaging (fMRI) method to reveal claustrum signal with no linear relationship with adjacent regions in human subjects. We applied this approach to resting state functional connectivity (RSFC) analysis of the claustrum at high resolution (1.5 mm isotropic voxels) using a 7T dataset (n = 20) and a separate 3T dataset for replication (n = 35). We then assessed claustrum activation during performance of a cognitive task, the multi-source interference task, at 3T (n = 33). Extensive functional connectivity was observed between claustrum and cortical regions associated with cognitive control, including anterior cingulate, prefrontal and parietal cortices. Cognitive task performance was associated with widespread activation and deactivation that overlapped with the cortical areas showing functional connectivity to the claustrum. Furthermore, during high cognitive conflict conditions of the task, the claustrum was significantly activated at the onset of the task, but not during the remainder of the difficult condition. Both of these findings suggest that the human claustrum can be functionally isolated with fMRI, and that it may play a role in cognitive control, and specifically task switching, independent of sensorimotor processing.

P112. Modulatory effects of anodal transcranial direct current stimulation on fronto-striatal gain control of the interplay between selective attention and perception

Carrying conversations in public spaces with a plethora of competing sensory inputs demands flexible interactions between attention and perception for selectively processing goal-relevant information. We postulate that the fronto-striatal network plays a key role in regulating this interaction. However, to date the underlying gain control mechanisms are not yet well understood. Neuronal gain control can be fine-tuned by membrane potential regulated changes in neuronal excitability. Anodal transcranial current stimulation (atDCS) has been shown to cause a depolarization of resting membrane potentials, which increases neuronal excitability. In the present study, we applied off-line atDCS over the right inferior frontal gyrus (IFG) in healthy young adults in a single-blinded sham-controlled study to investigate atDCS-induced effects on fronto-striatal gain control of auditory attention. We recorded high-density EEG recordings during a dichotic listening task in which both perceptual saliency and attentional focus were varied, creating conditions of low and high perceptual-attentional conflict. Compared to sham stimulation, pilot results suggest that atDCS enhanced auditory perception and attentional regulation: Specifically, atDCS increased discrimination ability of inter-aural intensity differences and enhanced performance in high conflict conditions. These behavioral effects were reflected by EEG correlates associated with attentional and perceptual processing.

Modulation of amygdala response to task-irrelevant emotion.

It has been shown that as cognitive demands of a non-emotional task increase, amygdala response to task-irrelevant emotional stimuli is reduced. However, it remains unclear whether effects are due to altered task demands, or altered perceptual input associated with task demands. Here, we present fMRI data from 20 adult males during a novel cognitive conflict task in which the requirement to scan emotional information was necessary for task performance and held constant across levels of cognitive conflict. Response to fearful facial expressions was attenuated under high (vs low) conflict conditions, as indexed by both slower reaction times and reduced right amygdala response. Psychophysiological interaction analysis showed that increased amygdala response to fear in the low conflict condition was accompanied by increased functional coupling with middle frontal gyrus, a prefrontal region previously associated with emotion regulation during cognitive task performance. These data suggest that amygdala response to emotion is modulated as a function of task demands, even when perceptual inputs are closely matched across load conditions. PPI data also show that, in particular emotional contexts, increased functional coupling of amygdala with prefrontal cortex can paradoxically occur when executive demands are lower.

Exploring the alcohol-behaviour link: Myopic self-enhancement in the absence of alcohol consumption as a function of past alcohol use

Dual process accounts of the alcohol-behaviour link hypothesise that differences in drinking patterns will moderate the effects of exposure to alcohol-related cues on behaviour, such as when a placebo is administered. We test this hypothesis by adapting a paradigm used in alcohol myopia research to examine the effects of alcohol-related priming on self-enhancement behaviour amongst social drinkers. Participants were asked to engage in a computerised self-rating task prior to being exposed to alcohol related and/or motivational primes. A staged computer error then occurred, and participants were then asked to complete their self ratings again – this method allowed for an immediate assessment of the impact of alcohol and motivational primes on self enhancement. As predicted by alcohol myopia theory, the overall effect of priming with alcohol-related cues was not significant irrespective of response-conflict manipulations. However, drinker type moderated this effect such that heavier drinkers self-enhanced more after exposure to alcohol-related cues, but only in high-conflict conditions. This suggests that the efficacy of a placebo may be significantly moderated by individual differences in reactions to alcohol-related stimuli, and that dual process accounts of the effects of alcohol on behaviour better explains this variation than alcohol myopia theory.

Attention-Deficit/Hyperactivity Disorder Remission Is Linked to Better Neurophysiological Error Detection and Attention-Vigilance Processes

BackgroundThe processes underlying persistence and remission of attention-deficit/hyperactivity disorder (ADHD) are poorly understood. We examined whether cognitive and neurophysiological impairments on a performance-monitoring task distinguish between ADHD persisters and remitters.MethodsOn average 6 years after initial assessment, 110 adolescents and young adults with childhood ADHD (87 persisters, 23 remitters) and 169 age-matched control participants were compared on cognitive-performance measures and event-related potentials of conflict monitoring (N2) and error processing (error-related negativity and positivity) from an arrow flanker task with low-conflict and high-conflict conditions. ADHD outcome was examined with parent-reported symptoms and functional impairment measures using a categorical (DSM-IV) and a dimensional approach.ResultsADHD persisters were impaired compared with controls on all cognitive-performance and event-related potential measures (all p < .05). ADHD remitters differed from persisters and were indistinguishable from control participants on the number of congruent (low-conflict) errors, reaction time variability, error-related negativity, and error-related positivity (all p ≤ .05). Remitters did not differ significantly from the other groups on incongruent (high-conflict) errors, mean reaction time, and N2. In dimensional analyses on all participants with childhood ADHD, ADHD symptoms and functional impairment at follow-up were significantly correlated with congruent errors, reaction time variability, and error-related positivity (r = .19–.23, p ≤ .05).ConclusionsCognitive and neurophysiological measures of attention-vigilance and error detection distinguished ADHD remitters from persisters. These results extend our previous findings with other tasks and indicate that such measures are markers of remission and candidates for the development of nonpharmacological interventions.

Lexical conflict resolution in children with specific language impairment

The aim of our study is to examine the effect of conflict on naming latencies in children with specific language impairment (SLI) and typically developing (TD) children and to explore whether deficits in conflict resolution contribute to lexical problems in SLI. In light of previous results showing difficulties with inhibitory functions in SLI, we expected higher semantic conflict effect in the SLI than in the TD group. To investigate this question 13 children with SLI and 13 age- and gender-matched TD children performed a picture naming task in which the level of conflict was manipulated and naming latencies were measured. Children took longer to name pictures in high conflict conditions than in low conflict conditions. This effect was equally present in the SLI and TD groups. Our results suggest that word production is more effortful for children when conflict resolution is required but children with SLI manage competing lexical representations as efficiently as TD children. This result contradicts studies, which found difficulties with inhibitory functions and is in line with findings of intact inhibitory abilities in children with SLI. Further studies should rule out the possibility that in SLI lower level of conflict resulting from weaker lexical representations masks impairments in inhibition, and investigate the effect of linguistic conflict in other areas.

Human mesostriatal response tracks motivational tendencies under naturalistic goal conflict.

Goal conflict situations, involving the simultaneous presence of reward and punishment, occur commonly in real life, and reflect well-known individual differences in the behavioral tendency to approach or avoid. However, despite accumulating neural depiction of motivational processing, the investigation of naturalistic approach behavior and its interplay with individual tendencies is remarkably lacking. We developed a novel ecological interactive scenario which triggers motivational behavior under high or low goal conflict conditions. Fifty-five healthy subjects played the game during a functional magnetic resonance imaging scan. A machine-learning approach was applied to classify approach/avoidance behaviors during the game. To achieve an independent measure of individual tendencies, an integrative profile was composed from three established theoretical models. Results demonstrated that approach under high relative to low conflict involved increased activity in the ventral tegmental area (VTA), peri-aquaductal gray, ventral striatum (VS) and precuneus. Notably, only VS and VTA activations during high conflict discriminated between approach/avoidance personality profiles, suggesting that the relationship between individual personality and naturalistic motivational tendencies is uniquely associated with the mesostriatal pathway. VTA-VS further demonstrated stronger coupling during high vs low conflict. These findings are the first to unravel the multilevel relationship among personality profile, approach tendencies in naturalistic set-up and their underlying neural manifestation, thus enabling new avenues for investigating approach-related psychopathologies.

L’imagerie au service de la stimulation cérébrale profonde

Obsessive-compulsive disorder (OCD) is characterized by: (i) a relatively high frequency in the general population; (ii) a chronic or recurrent course; and, (iii) a poor clinical response to conventional therapeutic strategies primarily consisting in the combination of serotonin reuptake inhibitors (SSRIs) and cognitive behavioral therapies (CBT). Better understand the pathophysiology of obsessive-compulsive disorder (OCD) is therefore a major issue in this context that could further serve to deep brain stimulation proposed for treating resistant cases of OCD. The most significant advances have been made thanks to the contribution of neuroimaging techniques helping identifying profound functional disturbances within the frontal-sub-cortical loops. It has been found in patients with OCD that there are an enhanced metabolic activity within several cortical and sub-cortical regions especially including the orbitofrontal and anterior cingulate cortices, the caudate nucleus and the thalamus, in either resting or symptom provocation conditions. Also, increased functional connectivity implicating both orbitofrontal and anterior cingulate cortices and the ventral caudate nucleus has been reported in OCD patients. Correlations have been established with the clinical severity of OCD and related anxiety. However, such functional abnormalities could be reversed in response to antidepressant treatments with SSRIs and CBT along with the improvement in OCD symptom intensity. These data contrast with the deficit in activation within various cortical areas, such as the ventrolateral prefrontal cortex, which was observed during the instrumental tasks specifically exploring either cognitive flexibility or behavioral inhibition. Importantly, this lack of cortical activation was associated with impaired behavioral performances in both OCD patients and unaffected first-degree relatives. However, overactivation within the supplementary motor area has been described, though assumed not to be sufficient to compensate the deterioration of behavioral inhibition observed in OCD patients. Hyperactivity was also found within the dorsal and rostral anterior cingulate cortex of the OCD patients in high-conflict conditions, especially when they have responded correctly to the given instruction, therefore reflecting the high level of uncertainty that drives them. Finally, repetitive checking behaviors represent the most frequently observed forms of compulsions in OCD patients. When placed in a potential situation of unrestricted repetitive checking, OCD patients experiencing daily checking compulsions show a greater number of verification and a longer response time for choice before checking than control subjects. Also, external error signals or checking behaviors have no impact on the degree of uncertainty, as evinced by an unchanged activity within the ventrolateral prefrontal cortex of OCD patients, when the choice is made at the subsequent trial. Taken together, these findings have contributed to shed new light on the importance of the cortico-sub-cortical loops in the pathogenesis of OCD by identifying some dysfunctional processes recognized today to play a major role in the clinical expression of OCD. They also offer the advantage to propose novel anatomical targets for neurosurgical procedures such as deep brain stimulation that is now considered as a promising therapeutic strategy for the management of resistant OCD.

Classic Stroop Negative Priming Effects for Children and Adults Diverge With Less-Conflicting and Nonconflicting Conditions

Negative priming indexes an inhibition process that aids target selection by reducing distractor interference. To date, children have produced negative priming only in tasks where distractor response tendencies are consistently greater than or equal to targets and not in tasks containing a substantial proportion of low-conflict distractors. To establish the exact parameters under which children's negative priming attenuates relative to adults, we varied processing demands across 2 experiments involving children and adults. Negative priming was comparable when 100% high-conflict conditions were encountered (Experiment 1) and was intact in adults but not children when a ratio of 50:50 high- to low-conflict conditions was encountered (Experiment 2). Compared with adults, children seem induced to divide attention more generally when low-conflict attentional conditions are included, attenuating negative priming.

Deep Brain Stimulation for Parkinson's Disease: Where Do We Stand?

Deep Brain Stimulation for Parkinson's Disease: Where Do We Stand?

Hold Your Horses: Impulsivity, Deep Brain Stimulation, and Medication in Parkinsonism

Deep brain stimulation (DBS) of the subthalamic nucleus markedly improves the motor symptoms of Parkinson's disease, but causes cognitive side effects such as impulsivity. We showed that DBS selectively interferes with the normal ability to slow down when faced with decision conflict. While on DBS, patients actually sped up their decisions under high-conflict conditions. This form of impulsivity was not affected by dopaminergic medication status. Instead, medication impaired patients' ability to learn from negative decision outcomes. These findings implicate independent mechanisms leading to impulsivity in treated Parkinson's patients and were predicted by a single neurocomputational model of the basal ganglia.

The neural basis of risky decision-making in a blackjack task

To investigate the neural substrates of risky decision making in gambling tasks, we recorded event-related potentials while participants engaged in a modified blackjack game. We focused on the high-conflict condition (probability of losing approximately 50%) and low-conflict condition (probability of losing approximately 20%). We were also interested in the difference between risky and conservative responses under high-conflict conditions. In the 220-320 and 500-600 ms time windows, high-conflict conditions elicited more negative event-related potential deflections than low-conflict conditions. In the latter time window, risky conditions elicited more negative event-related potential deflections than conservative conditions. The N2 (220-320 ms) and N500 (500-600 ms) provide evidence for the dissociation of neural circuits between perceptual and response conflicts.

Methylphenidate improves deficient error evaluation in children with ADHD: An event-related brain potential study

Children with ADHD make more errors than control children in response-conflict tasks. To explore whether this is mediated by enhanced sensitivity to conflict or reduced error-processing, task-related brain activity (N2, Ne/ERN, Pe) was compared between 8- to 12-year-old children with ADHD and healthy controls during performance of a flanker task. Furthermore, effects of methylphenidate were investigated in ADHD children in a second study.ADHD children made more errors, especially in high-response-conflict conditions, without showing post-error slowing. N2 amplitudes were enhanced on trials resulting in an error response, Ne/ERN amplitude was unaffected and Pe amplitude was reduced in the ADHD group. Methylphenidate reduced errors in both low- and high-conflict conditions and normalized Pe amplitudes in children with ADHD. It was concluded that the inaccurate behaviour of ADHD children in conflict tasks might be related to reduced error-awareness and higher sensitivity to response conflict. Methylphenidate's ameliorating effects might be established through its influence on brain networks including posterior (parietal) cortex, enabling children with ADHD to allocate more attention to significant events.

Target spatial frequency determines the response to conflicting defocus- and convergence-driven accommodative stimuli

Asthenopia, or visual fatigue, is a frequent complaint from observers of stereoscopic three-dimensional displays. It has been proposed that asthenopia is a consequence of anomalous oculomotor responses generated by conflict between accommodative and convergence stimuli. The hypothesis was examined by measuring accommodation and convergence continuously with a Shin-Nippon SRW5000 infrared autorefractor and a limbus tracking device. Subjects viewed a high contrast Maltese Cross target at three levels of Gaussian filter target blur under conditions of relatively low- and high-conflict between accommodation and convergence stimuli, the latter inducing the sensation of stereopsis. Under the low-conflict conditions accommodation was stable, but convergence-driven accommodation was dominant when the target was extremely blurred. Under the high-conflict conditions the role of convergence-driven accommodation increased systematically with the degree of target blur. It is proposed that defocus-driven accommodation becomes weak when the target comprises low spatial frequency components. Large accommodative overshoots to step stimuli that are not blurred or only mildly blurred were consistently observed and are attributed to the initial accommodative response being convergence-driven. Whereas the possibility that high-conflict conditions are a cause of asthenopia has been previously reported, this is the first evidence that they specifically affect accommodative responses while viewing stereoscopic displays.