The role of the parietal cortex in inhibitory processing in the vertical meridian: Evidence from elderly brain damaged patients

We explored the effects of parietal damage on inhibitory effects of visuospatial attention, inhibition of return (IOR) and inhibitory tagging (IT), in the vertical meridian. We combined a vertical spatial cue paradigm with a Stroop task employing three different temporal intervals between the spatial cue and the target (700, 1200 and 2000 ms) in two groups of patients, one with damage to the parietal cortex and underlying white matter (the parietal patients group) and the other with damage in other brain areas not including the parietal lobe (the control patient group), and a healthy control group. Healthy controls showed the expected inhibitory effects, IOR at the 700 and 1200 intervals and IT at the 1200 interval (as evidenced in a reduction in the magnitude of Stroop interference at the cued location). On the other hand, only the group of parietal patients showed delayed onset of inhibitory effects, IOR and IT appeared at the 1200 ms and 2000 ms intervals, respectively. These findings provide evidence for a role of the parietal cortex, and the underlying fibre tracts, in inhibitory processing in the vertical meridian, with damage to the parietal cortex altering the time course of attention-dependent inhibition.

Time course of the inhibitory tagging effect in ongoing emotional processing. A HD-tDCS study

When a cueing procedure that usually triggers inhibition of return (IOR) effects is combined with tasks that tap semantic processing, or involve response-based conflict, an inhibitory tagging (IT) emerges that disrupts responses to stimuli at inhibited locations. IT seems to involve the executive prefrontal cortex, mainly the left dorsolateral prefrontal cortex (DLPFC), in cognitive conflict tasks. Contrary to other inhibitory effects, IT has been observed with rather short intervals, concretely when the stimulus onset asynchrony (SOA) between the prime presented at the cued location, and the subsequent target is 250 ms. Here we asked whether IT is also applied to ongoing emotional processing, and whether the left DLPFC plays a causal role in IT using HD-tDCS. In two experiments with an emotional conflict task, we observed reduced conflict effects, the signature of IT, when the prime word was presented at the cued location, and once again when the prime-target SOA was just 250 ms. Also, the IT effect was eliminated when cathodal stimulation was applied to the left DLPFC. These findings suggest that the IT effect involves areas of the executive attention network and cooperates with IOR to favor attentional allocation to novel unexplored objects/locations, irrespective of their emotional content.

The Time Course of Inhibition of Return: Evidence from Steady-State Visual Evoked Potentials

Inhibition of return (IOR) refers to slower responses to targets at a previously cued location than that at an uncued location. The time course of IOR has long been a topic of interest in the field. Investigations into the time course of IOR are typically performed by examining the magnitude of IOR under various cue-target onset asynchrony (CTOA) conditions. Therefore, the results are vulnerable to influence of factors that could affect the target processes (e.g., the frequency of the target type). In the present study, steady-state visual evoked potentials (SSVEPs) were implemented to directly take a continuous measurement of the degree to which cued location is processed, eliminating the influence mentioned above. The results indicate that, relative to the baseline interval (−400 to 0 ms), the presence of peripheral cues generated a typical two-stage effect on the SSVEP amplitude evoked by a 20 Hz flicker. Specifically, after the onset of the peripheral cues, the SSVEP amplitude first showed a significant increase, which subsequently turned into a significant inhibition effect after 200 ms. These results provide a continuous time course diagram of the cueing effect and suggest an effective way for future investigations of controlling the masking effects of target stimuli processing on IOR.

Increased distractibility in schizotypy: Independent of individual differences in working memory capacity?

Individuals with schizophrenia typically show increased levels of distractibility. This has been attributed to impaired working memory capacity (WMC), since lower WMC is typically associated with higher distractibility, and schizophrenia is typically associated with impoverished WMC. Here, participants performed verbal and spatial serial recall tasks that were accompanied by to-be-ignored speech tokens. For the few trials wherein one speech token was replaced with a different token, impairment was produced to task scores (a deviation effect). Participants subsequently completed a schizotypy questionnaire and a WMC measure. Higher schizotypy scores were associated with lower WMC (as measured with operation span, OSPAN), but WMC and schizotypy scores explained unique variance in relation to the mean magnitude of the deviation effect. These results suggest that schizotypy is associated with heightened domain-general distractibility, but that this is independent of its relationship with WMC.

Attentional orienting and response inhibition: insights from spatial-temporal neuroimaging

Attentional orienting and response inhibition have largely been studied separately. Each has yielded important findings, but controversy remains concerning whether they share any neurocognitive processes. These conflicting findings may originate from two issues: (1) at the cognitive level, attentional orienting and response inhibition are typically studied in isolation; and (2) at the technological level, a single neuroimaging method is typically used to study these processes. This article reviews recent achievements in both spatial and temporal neuroimaging, emphasizing the relationship between attentional orienting and response inhibition. We suggest that coordinated engagement, both top-down and bottom-up, serves as a common neural mechanism underlying these two cognitive processes. In addition, the right ventrolateral prefrontal cortex may play a major role in their harmonious operation.

Inhibition of return: Twenty years after

When responding to a suddenly appearing stimulus, we are slower and/or less accurate when the stimulus occurs at the same location of a previous event than when it appears in a new location. This phenomenon, often referred to as inhibition of return (IOR), has fostered a huge amount of research in the last 20 years. In this selective review, which introduces a Special Issue of Cognitive Neuropsychology dedicated to IOR, we discuss some of the methods used for eliciting IOR and its boundary conditions. We also address its debated relationships with orienting of attention, succinctly review findings of altered IOR in normal elderly and neuropsychiatric patients, and present results concerning its possible neural bases. We conclude with an outline of the papers collected in this issue, which offer a more in-depth treatment of behavioural, neural, and theoretical issues related to IOR.

Abnormal inhibition of return: A review and new data on patients with parietal lobe damage

The study of the performance of patients with neurological disorders has been fruitful in revealing the nature and neural basis of inhibition of return (IOR). Thus, in recent years, studies have reported abnormal IOR in patients with Alzheimer's disease, patients diagnosed with schizophrenia, and brain-damaged patients. In the present study, we investigated the hypothesis that a spatial "disengagement deficit" (DD; Posner, Walker, Friedrich, & Rafal, 1984) contributed to the pattern of impaired IOR in the ipsilesional field of parietal patients, found in a previous work (Vivas, Humphreys, & Fuentes, 2003). In a first experiment, we replicated the attenuation of IOR for ipsilesional targets on those trials with a lateralized IOR procedure. With stimuli vertically aligned about fixation, we found intact IOR for both up and down targets. Most important, when we ameliorated the potential impact of a spatial DD by presenting both cues and target in the same hemifield, still we found impaired IOR in the ipsilesional field. We interpret these findings in terms of unilateral parietal damage leading to an imbalance of the relative salience of signals represented in a spatial map for directing attention.

[Production of rhythms in schizophrenia: the central role of attention]

BACKGROUND

Schizophrenia is a psychiatric illness that is characterised by a deficit in the fluent sequencing of thought and action. This problem of discoordination might be due to unreliable timing processes associated with a difficulty in allocating sufficient attention. In the present study, we placed ourselves within the hypothesis that schizophrenic patients may have difficulties in producing rhythmic tapping actions and that this deficit may be correlated with the degree of attention abnormalities.

METHOD

Subjects were required to tap in rhythm with alternating force levels and/or alternating time intervals (<1s) during trials lasting 24s. In addition, all patients performed an attention task (D2 test). A qualitative analysis of the tap trials was conducted in order to characterise the nature of the deficits that patients revealed.

RESULTS

Results showed that all patients revealed significant difficulties in performing the tapping trials. The number of trials removed was correlated with the level of attention dysfunction. Finally, our qualitative analysis revealed that 60% of patients presented attentional lapses - which were never observed in the healthy controls.

CONCLUSION

This study revealed deficits in the timing of action that resemble, at least on a behaviour level, the clinical lapses observed in schizophrenia. These lapses seem to be correlated to the degree of attention deficits. Future studies are now required in order to gain better understanding of the nature of the attention deficits in schizophrenia. More specifically, a better definition of the possible functional relationship between clinical lapses, cognitive lapses and action freezing is needed to develop innovating tools for rehabilitation.

Deficient inhibition of return in chronic but not first-episode patients with schizophrenia

BACKGROUND

Inhibition of return (IOR) has been tested in patients with schizophrenia with contradictory results. Some studies indicated that patients with schizophrenia have normal levels of IOR; however, other studies reported delayed or blunted IOR. Inconsistency in findings might be due to differences across studies in relevant aspects associated with disease, such as heterogeneity of the disorder, different medications, onset and severity of the illness. The present study was to explore different patterns of IOR in antipsychotic medication free first-episode schizophrenia and chronic schizophrenia.

METHODS

Forty two patients with first-episode schizophrenia, 44 patients with chronic schizophrenia, and 38 healthy controls were included in the study. All subjects went through a covert orienting of attention task with seven stimulus onset asynchrony (SOA) intervals (400 ms, 500 ms, 600 ms, 700 ms, 800 ms, 1200 ms and 1500 ms).

RESULTS

Compared with healthy controls, the magnitude and onset of IOR in first-episode patients with schizophrenia were intact. However, in patients with chronic schizophrenia, there was an attenuated cuing effect especially at SOA 700 ms; in addition, there was a robust IOR until at SOAs 800 ms or above. Moreover, the illness duration and the number of psychotic episodes were significantly correlated with the validity effect at SOAs 400 ms and 600 ms.

CONCLUSION

Our study suggests that deficient IOR presents in chronic but not in first-episode patients with schizophrenia. IOR deficit in schizophrenia may begin during the course of illness and deteriorate over the course of illness. Our findings are consistent with the neurodegenerative model of schizophrenia.

Gaze cueing of attention in schizophrenia: individual differences in neuropsychological functioning and symptoms

Inhibition of return (IOR) represents a well-known mechanism of human perception that biases attentional orienting to novel locations in the environment. Behaviorally, IOR reflects slower reaction time (RT) to stimuli presented in previously cued locations. In this study, we examined within patients with schizophrenia this inhibitory aftereffect using two different cue types--eye gaze and standard peripheral cues. Results indicated that patients showed evidence of IOR, as reflected in a 3.2% slowing in RT to previously peripherally cued locations. However, for eye gaze, patients failed to show evidence of IOR and instead had 1.7% faster RT to targets presented following delay in locations that had been previously cued. This inhibitory failure correlated strongly with reduced neuropsychological performance and global symptoms ratings of attention and bizarre behavior. Reduced inhibitory aftereffect in RT for eye-gaze cues may reflect disease-related abnormalities in social attention.

A repetition-suppression account of between-trial effects in a modified Stroop paradigm

Theories that postulate cognitive inhibition are very common in psychology and cognitive neuroscience [e.g., Hasher, L., Lustig, C., & Zacks, R. T. (2007). Inhibitory mechanisms and the control of attention. In A. Conway, C. Jarrold, M. Kane, A. Miyake, A. Towse, & J. Towse (Eds.), Variation in working memory (pp. 227-249). New York, NY: Oxford, University Press], although they have recently been severely criticized [e.g., MacLeod, C. M., Dodd, M. D., Sheard, E. D., Wilson, D. E., & Bibi, U. (2003). In opposition to inhibition. In H. Ross (Ed.), The psychology of learning and motivation (Vol. 43, pp. 163-214). Elsevier Science]. This paper poses and attempts to answer the question whether a research program with cognitive inhibition as its main theoretical assumption is still worth pursuing. We present a set of empirical data from a modified Stroop paradigm that replicates previously reported findings. These findings refer to between-trial effects previously described in the literature on Stroop, negative priming, and inhibition-of-return. Existing theoretical accounts fail to explain all these effects in an integrated way. A repetition-suppression mechanism is proposed in order to account for these data. This mechanism is instantiated as a computational cognitive model. The theoretical implications of this model are discussed.

Inhibition and facilitation in schizotypy

Participants scoring high and low on a schizotypy scale (n=18 in each group) switched between naming words and naming colors in a Stroop task in congruent, neutral, and incongruent conditions. The findings were that, while being slower and less accurate overall than low schizotypes, the high schizotypy group did not display disproportionately greater Stroop inhibition or facilitation, suggesting intact selective attention. However, the high schizotypy group suffered disproportionately larger switching costs. The results provide evidence for similarities between schizotypy and schizophrenia, specifically that the problem in schizotypy is to do with switching rather than selecting attention, because of a difficulty either in selecting task-relevant information or in inhibiting inappropriate response alternatives.

Attentional capture in schizophrenia and schizotypy: effect of attentional load

INTRODUCTION

We examined the effect of attentional load on attentional capture in schizophrenia. On the basis of the ''resource limitations hypothesis'' in schizophrenia, we propose that attentional capture by an irrelevant distractor will be differentially affected by the attentional load for patients and healthy controls.

METHOD

70 patients with schizophrenia, 15 schizotypals, and 54 controls were asked to attend to a central task while a lateral distractor moved. Participants were instructed either (i) to localise a black square (low-load condition), or (ii) to locate the larger number between two 1-digit numbers (medium-load condition), or (iii) to locate the larger number between two several-digit numbers (high-load condition). In the baseline condition, no distractor moved.

RESULTS

All groups showed attentional capture in the low-load condition. Patients and schizotypals resisted interference from the distractor in the medium and highload conditions. Controls resisted interference in the high-load condition.

CONCLUSION

The results suggest that attentional modulation is impaired in schizophrenia and in the schizophrenia spectrum.

Inhibitory tagging in inhibition of return: evidence from flanker interference with multiple distractor features

Fuentes, Vivas, and Humphreys (1999) proposed a distinction between inhibition of return (IOR) and inhibitory processing taking place at a location subject to IOR. This latter mechanism, inhibitory tagging (IT), would act at a late level of processing related to response selection. In the present study, we examined whether IT was applied only to the target-relevant properties of the stimuli (e.g., to its color) or whether it was applied to other features of the stimulus as well (e.g., to its shape). Both when the task was to respond to the target's color (Experiment 1) as well as when it was to respond to the target's shape (Experiment 2), there was evidence of IT (reversal of the typical flanker effect at the cued location, relative to the uncued location) only to task-relevant features of the target. These findings suggest that IT is a central process of control constrained by task demands and current goals.

Distinct Neural Correlates for Resolving Stroop Conflict at Inhibited and Noninhibited Locations in Inhibition of Return

It is well documented that the anterior cingulate cortex (ACC) and the dorsolateral prefrontal cortex (DLPFC) are intensively involved in conflict control. However, it remains unclear how these “executive” brain regions will act when the conflict control process interacts with spatial attentional orienting. In the classical spatial cueing paradigm [Posner, M. I., & Cohen, Y. (1984). Components of visual orienting. In H. Bouma & D. G. Bouwhuis (Eds.), Attention and performance X (pp. 531–556). Hillsdale, NJ: Erlbaum], response to a target is delayed when it appears at the cued location compared with at the uncued location, if the time interval between the cue and the target is greater than 300 msec. This effect of inhibition of return (IOR) can alter the resolution of Stroop conflict such that the Stroop interference effect disappears at the cued (inhibited) location [Vivas, A. B., & Fuentes, L. J. Stroop interference is affected in inhibition of return. Psychonomic Bulletin and Review, 8, 315–323, 2001]. In this event-related functional magnetic resonance study, we investigate the differential neural mechanisms underlying interactions between pre-response interference, response interference, and spatial orienting. Two types of Stroop words [incongruent response-eligible words (IE), incongruent response-ineligible words (II)] and neutral words were presented either at the cued or uncued location. The significant pre-response interference at the uncued location activated the left rostral ACC as compared with at the cued location. Moreover, although the IE words which have conflicts at both pre-response and response levels did not cause significant behavioral interference at the cued location, they activated the left DLPFC as compared with at the uncued location. Furthermore, neutral words showed significant IOR effects behaviorally, and they activated the left frontal eye field (FEF) at the uncued location relative to the cued location. These results suggest that the left rostral ACC is involved in the interaction between pre-response conflict and IOR, whereas the left DLPFC is involved in the interaction between response conflict and IOR. Moreover, the FEF is involved in shifting attentional focus to novel locations during spatial search.

Directed forgetting in schizophrenia: prefrontal memory and inhibition deficits

Schizophrenia is associated with cognitive deficits in the domains of working memory, strategic memory and other executive functions. In the current study we used a computerised and item-cued variant of the directed forgetting (DF) task to assess inhibitory processes in verbal memory. Twenty-five patients with schizophrenia and a group of matched controls were tested. Recognition memory was better for to-be-remembered (TBR) than for to-be-forgotten (TBF) words in both patients and controls. As compared to healthy controls the patients with schizophrenia showed overall memory deficits and difficulties to inhibit memories as indicated by a significant group by cue interaction and a smaller DF effect. The DF effect was associated with disease duration but not with symptom severity. Memory-related inhibition problems are difficult to assess in patients with schizophrenia and might be related to fronto-temporal disconnection.

Differential Age Effects on Attention-Based Inhibition: Inhibitory Tagging and Inhibition of Return

The purpose of this study was to determine whether 2 forms of attentional inhibition, inhibition of return (IOR) and inhibitory tagging, are differentially affected by the aging process. The authors tested 24 younger adults (mean age = 22 years) and 24 older adults (mean age = 69 years) on a combined IOR and Stroop task (Vivas & Fuentes, 2001). As predicted, younger adults' performance was consistent with inhibitory tagging of objects at inhibited locations. Although older adults demonstrated intact IOR, there was no evidence of inhibitory tagging. The results suggest that age deficits in inhibition are selective.

Inhibitory processing following damage to the parietal lobe

We investigated inhibitory properties of spatial attention in a group of four patients with lesions involving the posterior parietal lobe. In a first experiment, a double cue inhibition of return (IOR) procedure was employed. The parietal patients showed an IOR effect only when they had to detect targets that appeared on the contralesional side. In a second experiment, we combined an IOR procedure with a Stroop task [Psychon. Bull. Rev. 8 (2001) 315] to explore the neural basis of "inhibitory tagging" as described by Fuentes et al. [Q. J. Exp. Psychol. Hum. Exp. Psychol. 52 (1999) 149]. The results from the control participants replicated the findings of Vivas and Fuentes, Stroop interference was reduced at the cued location, relative to the uncued location. The parietal patients showed a similar result, but only for contralesional targets. These findings suggest that IOR is modulated by the parietal lobe, and that, through this process, the parietal cortex influences the application of inhibitory tagging to stimuli.

Cognitive interference is associated with neuronal marker N-acetyl aspartate in the anterior cingulate cortex: an in vivo (1)H-MRS study of the Stroop Color-Word task

The neurobiology of cognitive interference is unknown. Previous brain imaging studies using the Stroop Color-Word (SCW) task indicate involvement of the cingulate cortex cognitive division. The present study examines interrelationships between regional brain N-Acetyl aspartate (NAA) levels (as identified by in vivo proton magnetic resonance spectroscopy in the right and left anterior cingulate cortex (ACC), dorsolateral prefrontal cortex, orbitofrontal cortex and thalamus) and cognitive interference (as measured by the SCW task) in 15 normal subjects. The results show that brain chemistry depends on cognitive interference levels (high vs low). Reduction of NAA levels was demonstrated in the right ACC (ie, cognitive midsupracallosal division) of high interference subjects, as compared to the low interference group (P < 0.01, two-tailed t-test). Chemical-cognitive relationships were analyzed by calculating correlations between regional NAA levels and the SCW task scores. Cognitive interference was highly correlated with the right anterior cingulate NAA (r = 0.76, P < 0.001), and was unrelated to other studied regional NAA, including the left ACC (P < 0.025; comparing the difference between r values in the right and left ACC). The interrelationships between NAA across brain regions were examined using correlation analysis (square matrix correlation maps), which detected different connectivity patterns between the two groups. These findings provide evidence of ACC involvement in cognitive interference suggesting a possibility of neuronal reorganization in the physiological mechanism of interference (most likely due to genetically predetermined control of the number of neurons, dendrites and receptors, and their function). We conclude that spectroscopic brain mapping of NAA, the marker of neuronal density and function, to the SCW task measures differentiates between high and low interference in normal subjects. This neuroimaging/cognitive tool may be useful for documentation of interference in studying cognitive control mechanisms, and in diagnosis of neuropsychiatric disorders where dysfunction of cingulate cortex is expected.

Stroop interference is affected in inhibition of return

In previous research, we have shown that the processing of targets that are presented to locations subject to inhibition of return (IOR) is affected by an inhibitory tagging mechanism. This mechanism acts by disconnecting activated representations of stimuli at inhibited locations from their associated responses. In two experiments, we assessed whether this inhibitory tagging mechanism of visual attention is also applied to task-irrelevant but prepotent dimensions of target stimuli, such as words in the Stroop task. To test this hypothesis, we examined the Stroop effect in an IOR procedure. The results showed that (1) IOR can be found in a color discrimination task, (2) the Stroop interference was reduced (Experiment 1) or eliminated (Experiment 2) when stimuli appeared at cued locations, as compared with cases in which they were presented at uncued locations, and (3) the effect of inhibitory tagging was limited to the shortest stimulus onset asynchrony value, replicating previous findings. These results agree with the idea that inhibitory tagging, occurring in IOR, affects the efficiency with which color words compete for responses in Stroop-like situations.

Inhibitory processing in visuospatial attention in healthy adults and schizophrenic patients

This study assessed visuospatial attention in healthy adults and medicated schizophrenic patients. Participants performed a visual orientation task in which a peripheral cue was followed. at different intervals, by a target presented either at valid or invalid locations. When the long stimulus onset asynchrony (SOA) was used, participants were presented with either a single peripheral cue (single-cue condition) or two cues, the peripheral cue followed by a central cue (the double-cue condition). Healthy adults showed marginal facilitation effects with the short SOA and similar inhibition of return effects with the long SOA in both single-cue and double-cue conditions. Schizophrenic individuals showed a big facilitation effect with the short SOA and normal inhibition of return with the long SOA in both cue conditions. Results with the short SOA replicated previous findings (Huey, E.D., Wexler, B.E., 1994. Schizophrenia Research 14, 57-63) but, in contrast, we did not observe blunted inhibition of return with the long SOA. An inspection of the differences in the procedures used in both studies may help both to account for the discrepancies and to reveal what processes involved in visuospatial attention are affected in schizophrenia.