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PubMed1996

Attention control: explorations of the work of an executive controller.

This contribution reviews three lines of studies set to investigate attention control and executive operations, in the general context of the interplay between bottom-up and top-down processes in the conduct of proficient behavior. One line of studies focused on the act of switching attention between tasks and the mental costs associated with it. A second group of experiments investigated attention strategies and resource management in coping with high load and concurrent task demands. A third line of studies examined the influence of enhanced knowledge and accumulated experience on coping with malfunctions and mishaps in system response. The experimental results of all studies lend strong support to the existence and influence of executive control processes. These types of processes operate on the established representations and knowledge bases of tasks, to make the best use of processing and response facilities. The experiments shed light on the nature of the processes and the variables that influence them. It is shown that proficient performance is far from being exclusively guided by automatic processing and response routines triggered directly by events in the environment. Instead it is a joint and non-trivial product of these two types of processes. Executive control is required not only in early stages of training, but also at high levels of mastery and proficiency. Automatism does not eliminate or reduce the importance of executive control and strategic behavior. A new and powerful class of processes comes into play at this level of expertise, with strong influence on modes of behavior and the overall efficiency of performance.

Adaptation, Psychological↗

PubMed2005

Age differences in stroop interference in working memory.

Working memory capacity can be conceptualized as the ability to use controlled attention in short term memory (Engle, Tuholski, Laughlin, & Conway, 1999). We tested this idea in young and older adults by combining the task demands of two neuropsychological tests, word span, and Stroop color-naming. Young and older adults were asked to name the colors of a series of congruent and incongruent color-words (between 2 and 6 words/trial). After all the color-words were presented participants attempted to recall the colors in their serial order. This task required inhibition of the prepotent word reading response (i.e., color naming), with a concurrent memory load (caused by the need to maintain already named colors in short-term memory). Older adults showed greater interference effects, and these interference effects increased as a function of memory load. Regression analyses showed that measures of working memory capacity and executive function accounted for unique variance in incongruent color-word errors for older adults. Defining working memory capacity as the ability to use controlled attention in short-term memory may be a fruitful way to think about this concept in studies of executive function.

Adult↗

PubMedDate not supplied

Visual search and dual tasks reveal two distinct attentional resources.

Most theories of visual processing assume that a target will "pop out" from an array of distractors ("parallel" visual search, e.g., color or orientation discrimination) if targets and distractors can be discriminated without attention. When the discrimination requires attention (e.g., rotated L vs. T or red-green vs. green-red bisected disks), "serial" examination is needed in visual search. Attentional requirements are also frequently assessed by measuring interference from a concurrently performed attentionally demanding task. It is commonly believed that attention acts equivalently in dual-task and visual search paradigms, based on the implicit assumption that visual attentional requirements can be defined along a single dimension. Here we show that there is no such equivalence: We report on targets that do not trigger pop-out, even though they can be discriminated from distractors with attention occupied elsewhere (natural scenes, color-orientation conjunctions); conversely, we show that certain targets that pop out among distractors need undivided attention to be effectively discriminated from distractors when presented in isolation (rotated L vs. +, depth-rotated cubes). In other words, visual search and dual-task performance reveal attentional resources along two independent dimensions. We suggest an interpretation of these results in terms of neuronal selectivities and receptive field size effects.

Attention↗

PubMed1996

The informational role of knowledge of results in motor learning.

An experiment is reported that was set-up to examine the informational role of knowledge of results (KR) in the learning of a single-limb movement timing task. A group with KR practiced 200 trials a day for 5 days prior to receiving a sixth day of practice without KR. The performance of this group was contrasted to another group that practiced 200 trials without KR for one day. Traditional movement error and time series analyses revealed that KR serves to calibrate the movement outcome to the task demands and modulate the performance outcome relation between trials. The degree of systematic trial-to-trial modulation was strongly dependent upon the degree of error exhibited on any given trial, and was enhanced under no-KR conditions. Information in KR has both immediate and persistent influences on learning and performance that are dependent upon the task constraints and the skill level of the performer.

Humans↗

PubMed2003

ERP correlates of form and rhyme letter tasks in impaired reading children: a critical evaluation.

Event-related potentials (ERPs) were obtained from 15 electrode sites in six average and six impaired reading children, 12 years of age, during visual letter discrimination tasks. Subjects responded to target letters with an enclosed area in the form task and to letters that rhymed with "e" in the rhyme task. Response accuracy was similar between the groups. Reaction time was relatively longer for the impaired group during the rhyme task. At lateral sites, condition differences were evident as greater negative shifts in the rhyme task than the form at 170 and 470 ms as well as a delayed late positivity for the rhyme. In terms of reading ability, the average readers' ERPs were more negative than those of the impaired group at 270 and 450 ms. Inter-hemispheric variations were also seen between the groups, with the average readers more negative than the impaired readers at right hemisphere sites. Contrary to expectations, group differences in the ERP did not vary substantially as a function of condition, and task demands were evaluated in view of these findings.

Adolescent↗

PubMed1981

Response programming and reaction time.

A feature common in the literature is that, prior to responding, subjects have been able to preview the parameters of the movement they are required to make. This introduces the possibility of programming the movement before entering the reaction time period. It is argued that this has contributed to confusion in the literature, making it difficult to detect a consistent relationship between reaction time and motor task demands. Two experiments were conducted to clarify the position. Experiment I concealed the movement parameters prior to subjects responding ("no-preview" model), and this was contrasted with a study in the typical "preview" mode (Experiment II). It was concluded that the no-preview design is more appropriate to detecting changes in reaction time dependent on task parameters, and that the observed effects on reaction time reflect programming difficulty. A third experiment supported this conclusion

Journal Article↗

PubMed2004

Experiences of demand and control in daily life as correlates of subclinical carotid atherosclerosis in a healthy older sample.

Daily experiences of demand and control were examined as correlates of carotid artery atherosclerosis among healthy adults (ages 50-70). Mediating effects of ambulatory blood pressure (ABP) were also explored. Participants (n=337) collected ABP and recorded daily experiences, using electronic diaries, over two 3-day periods. Carotid artery intima-medial thickness (IMT) was assessed using ultrasonography. Participants reporting higher task demands during daily life showed larger IMT, after adjustment for demographic covariates. This association was not limited to workplace ratings or to employed individuals. The association was mediated, in part, by daytime systolic blood pressure. Previous findings linking job stress with cardiovascular disease may reflect the broader impact of daily psychological demands, not necessarily associated with the workplace.

Activities of Daily Living↗

PubMedDate not supplied

Involvement of the rat anterior cingulate cortex in control of instrumental responses guided by reward expectancy.

The anterior cingulate cortex (ACC) plays a critical role in stimulus-reinforcement learning and reward-guided selection of actions. Here we conducted a series of experiments to further elucidate the role of the ACC in instrumental behavior involving effort-based decision-making and instrumental learning guided by reward-predictive stimuli. In Experiment 1, rats were trained on a cost-benefit T-maze task in which they could either choose to climb a barrier to obtain a high reward (four pellets) in one arm or a low reward (two pellets) in the other with no barrier present. In line with previous studies, our data reveal that rats with quinolinic acid lesions of the ACC selected the response involving less work and smaller reward. Experiment 2 demonstrates that breaking points of instrumental performance under a progressive ratio schedule were similar in sham-lesioned and ACC-lesioned rats. Thus, lesions of the ACC did not interfere with the effort a rat is willing to expend to obtain a specific reward in this test. In a subsequent task, we examined effort-based decision-making in a lever-press task where rats had the choice between pressing a lever to receive preferred food pellets under a progressive ratio schedule, or free feeding on a less preferred food, i.e. lab chow. Results show that sham- and ACC-lesioned animals had similar breaking points and ingested comparable amounts of less-preferred food. Together, the results of Experiment 1 and 2 suggest that the ACC plays a role in evaluating how much effort to expend for reward; however, the ACC is not necessary in all situations requiring an assessment of costs and benefits. In Experiment 3 we investigated learning and reversal learning of instrumental responses guided by reward predictive stimuli. A reaction time (RT) task demanding conditioned lever release was used in which the upcoming reward magnitude (five vs. one food pellet) was signalled in advance by discriminative visual stimuli. Results revealed that rats with ACC lesions were able to discriminate reward magnitude-predictive stimuli and to adapt instrumental behavior to reversed stimulus-reward magnitude contingencies. Thus, in a simple discrimination task as used here, the ACC appears not to be required to discriminate reward magnitude-predictive stimuli and to use the learned significance of the stimuli to guide instrumental behavior.

Animals↗

PubMed2005

Hemispheric specialization of human inferior temporal cortex during coarse-to-fine and fine-to-coarse analysis of natural visual scenes.

Recent models of visual recognition have suggested that perceptual analysis may start with a parallel extraction of different spatial frequencies (SF), using a preferential coarse-to-fine (low-to-high SF) sequence of processing. A rapid extraction of low spatial frequency (LSF) information may thus provide an initial and crude parsing of the visual scene, subsequently refined by slow but more detailed high spatial frequency (HSF) information. However, the sequence of SF analysis could be flexible, a high-to-low (HtL) being sometimes preferred to a low-to-high (LtH) SF sequence depending on task demands. Furthermore, it has also been suggested that the right vs. left hemisphere might be differentially specialized in LSF vs. HSF analysis, respectively. By manipulating the temporal succession of LSF and HSF stimuli, the present fMRI study investigated whether such hemispheric specialization may underlie the flexible use of different time-course in SF analysis. Participants performed a matching task between two successive images of natural scenes (LSF or HSF) that were displayed either in an LtH (LSF scene presented first and HSF scene second) or in a reverse HtL sequence. A direct inter-hemispheric comparison of the neural responses evoked by each SF sequence revealed greater activations within the right occipito-temporal cortex for the LtH sequence and within the left occipito-temporal cortex for the HtL sequence. These fMRI results suggest that the hemisphere preferentially engaged during the sequential processing of different SF might be determined by the initial SF-band appearing in this sequence, and that both a coarse-to-fine and fine-to-coarse analysis might independently take place in the two hemispheres.

Adult↗

PubMed2001

Grip force scaling and sequencing of events during a manipulative task in Huntington's disease.

The aim of the study was to investigate force regulation and sequencing of events in Huntington's disease (HD) patients when performing a drawer opening task using the precision grip. Results revealed that HD patients used excessive grip force levels that were unrelated to the actual task demands. Also, they demonstrated a higher grip force value at load force onset in addition to an increased delay between initiation of grip force and load (pulling) force. These data indicate a deficit in the coordinated activation of both forces due to HD. Furthermore, the patients showed bradykinesia along with a prolonged interval between the movement phases underlying the task, denoting an impairment in encoding serially ordered events. Together, these results illustrate the deteriorating effect of striatal pathology on manual function. Accordingly, an amended control of grasping forces and serial encoding of movement-related events due to HD are likely to affect the proficiency of common manipulative skills.

Adult↗

PubMed2003

Rapid task-related plasticity of spectrotemporal receptive fields in primary auditory cortex.

We investigated the hypothesis that task performance can rapidly and adaptively reshape cortical receptive field properties in accord with specific task demands and salient sensory cues. We recorded neuronal responses in the primary auditory cortex of behaving ferrets that were trained to detect a target tone of any frequency. Cortical plasticity was quantified by measuring focal changes in each cell's spectrotemporal response field (STRF) in a series of passive and active behavioral conditions. STRF measurements were made simultaneously with task performance, providing multiple snapshots of the dynamic STRF during ongoing behavior. Attending to a specific target frequency during the detection task consistently induced localized facilitative changes in STRF shape, which were swift in onset. Such modulatory changes may enhance overall cortical responsiveness to the target tone and increase the likelihood of 'capturing' the attended target during the detection task. Some receptive field changes persisted for hours after the task was over and hence may contribute to long-term sensory memory.

Acoustic Stimulation↗

PubMed1995

Neural mechanisms for stimulus selection in cortical areas of the macaque subserving object vision.

The present article reviews some recent work on the neuronal mechanisms underlying space-based and feature-based stimulus selection in the primate occipito-temporal pathway of cortical visual processing. Clear evidence demonstrates that activity in areas V4 and IT is high for a stimulus which is selected either for its position in space or for its features, while it is considerably suppressed for other, irrelevant stimuli. Data are discussed within a conceptual framework whereby objects in the visual field always compete for focal resources. According to task demands, any kind of input (objects of a certain category, objects with a certain form, color or motion, objects at a certain location) can be behaviorally relevant. A short-term description (working memory) of the currently relevant object properties controls competitive bias in the visual system, such that inputs matching that description are favored to the disadvantage of task-irrelevant inputs. This framework emphasizes a tight, causal link between memory signals and mechanisms for stimulus selection in visual cortex. In all cases gating of neural activity was constrained by spatial factors. In area V4, responses to an ignored stimulus in the receptive field of the recorded neuron were maximally suppressed when the monkey attended to a second stimulus located within the boundary of the same receptive field, while suppression was virtually absent when attention was directed to a second stimulus well outside the receptive field border. In IT cortex, suppressed responses depended on both the selected and ignored stimuli being within the hemifield contralateral to the recorded hemisphere, while suppression was much reduced when the stimuli were presented across the vertical midline. These spatial constraints on the occurrence of modulation of visual responses may reflect limitations imposed by the local pattern of reciprocal inhibitory connections, which are supposed to underlie competitive interactions among objects in the field, that is among object representations in cortex.

Animals↗

PubMed2001

Context-specific interference on reversal learning of a stimulus-response habit.

Learning occurs in a particular place and time. In most learning situations, information about the training context is encoded along with the task demands and solution. However, the extent to which context contributes to the acquisition and expression of a particular learned response is unclear. In the present paper we examined two fundamental issues underlying the importance of context information and its role in expression of discrimination learning and reversal learning. Rats were trained on a stimulus-response (S-R) habit task designed for the eight-arm radial maze and after reaching a set criterion different context manipulations were performed. Results from Section 2.2.1 revealed that although rats detected a change in context, the learning was not context specific. Results from Section 2.2.2 showed that S-R reversal learning was enhanced when animals were reversed in a context that was different from the one used during original training. Animals that were reversed in a different context showed a renewal effect to the initial S-R when brought back to the original training context.

Animals↗

PubMed2000

The use of cognitive context in schizophrenia: an investigation.

BACKGROUND: Cognitive deficits in schizophrenia have recently been ascribed to impaired representation and use of cognitive context. Context is defined as relevant information held temporarily in mind to mediate appropriate but often non-habitual responses. METHODS: Parallel studies in a variety of cognitive domains were designed in order to explore the generality of any schizophrenic deficit in context use. In all of the tasks (a Stroop task, a Continuous Performance Task and a cued spatial location task), we examined how performance was affected by the time for which contextual information must be held in mind, and by whether context or task demands were consistent or varying between trials. It was predicted that manipulation of these variables would produce tests especially sensitive to schizophrenic attentional problems. RESULTS: Predictions were partially confirmed. Although increasing contextual demands failed in most cases to produce disproportionate slowing of performance in patients, error data were largely in line with predictions. At the same time, the data did not suggest a simple unitary context deficit. Instead, different aspects of context--the time over which contextual information must be held in mind and the consistency of context--were differentially important in different tasks. CONCLUSIONS: The cognitive impairments of schizophrenic patients cannot be simply characterized as a generalized context deficit. A more differentiated, if not task specific, picture of schizophrenic deficits is suggested.

Adult↗

PubMed1997

The effect of fixation condition manipulations on antisaccade performance in schizophrenia: studies of diagnostic specificity.

This series of studies evaluated (1) hypotheses that poor antisaccade performance is attributable to confounding variables (e.g., visual attention deficits, incomplete understanding of task demands) and (2) the specificity of poor antisaccade performance to schizophrenia. In addition to self-correcting errors before being cued to do so, schizophrenia patients also showed the expected saccadic reaction time changes to fixation condition manipulations: decreased latencies for gap and increased latencies for overlap trials. These data suggest that schizophrenia patients are adequately engaged in and understand the antisaccade task. Schizophrenia patients made fewer correct antisaccade responses than other psychiatric patients (obsessive-compulsive and bipolar disorder) and normal subjects. The first-degree relatives of schizophrenia patients also generated a decreased proportion of correct antisaccade responses compared with normal subjects. For schizophrenia patients who performed below the range of normal subjects, 26% of their relatives also performed below the normal range. Conversely, patients who performed normally did not have a single poor-performing relative. These data suggest that increased antisaccade error rates may index a liability for schizophrenia within a subset of families.

Adult↗

PubMed2005

Adaptive modulation of color salience contingent upon global form coding and task relevance.

Extensive research on local color aftereffects has revealed perceptual consequences of opponent color coding in the retina and the LGN, and of orientation-and/or spatial-frequency-contingent color coding in early cortical visual areas (e.g., V1 and V2). Here, we report a color aftereffect that depends crucially on global-form-contingent color processing. Brief viewing of colored items (passively viewed, ignored, or attended) reduced the salience of the previewed color in a subsequent task of color-based visual search. This color-salience aftereffect was relatively insensitive to variations (between color preview and search) in local image features, but was substantially affected by changes in global configuration (e.g. the presence or absence of perceptual unitization); the global-form dependence of the aftereffect was also modulated by task demands. The overall results suggest that (1) color salience is adaptively modulated (from fixation to fixation), drawing attention to a new color in visual-search contexts, and (2) these modulations seem to be mediated by global-form-and-color-selective neural processing in mid to late stages of the ventral visual pathway (e.g., V4 and IT), in combination with task-dependent feedback from higher cortical areas (e.g., prefrontal cortex).

Attention↗

PubMed2004

Validation of the Detroit Area Study Discrimination Scale in a community sample of older African American adults: the Pittsburgh healthy heart project.

This study examined the construct validity of the Detroit Area Study Discrimination Questionnaire (DAS-DQ) in 49 healthy African American adults, with respect to its association with global measures and daily experiences of psychological demand. Daily experiences of psychological demand were obtained using ecological momentary assessment (EMA) methods. Everyday Mistreatment, as measured by the DAS-DQ, was significantly related to global reports of perceived stress and depression but was unrelated to measures of hostility and social desirability. Everyday Mistreatment was significantly related to average EMA score measures of Negative Affect and Social Conflict but was unrelated to daily experiences of Task Demand or Decisional Control. Negative Affect mediated the relation between Everyday Mistreatment and global reports of perceived stress. In contrast, Lifetime History of Discrimination, as measured by the DAS-DQ, was unrelated to global measures or daily experiences of stress. Thus, this study lends support to the construct validity of the DAS-DQ.

Aged↗

PubMed1998

The effects of emotional behaviour on components of the respiratory cycle.

The present study was designed to examine affect-related respiratory responses during film scenes, reaction time (RT) and cold pressor (CP) tasks. In addition, I investigated whether affect-related respiratory responses could be characterised by a number of underlying dimensions, such as positive versus negative affect and active versus passive coping. Respiratory output was indexed by a detailed analyses of various volumetric and timing components of the breathing cycle. There were fundamental differences in respiratory responses to different types of affective and cognitively demanding tasks. The emotionally loaded film stimuli showed clear effects on respiration whenever the films elicited amusement and disgust. That is, amusement (laughter) induced a decrease in inspiratory time and tidal volume, whereas disgust could be linked to a prolongation of inspiratory pauses (breath-holding). Relative to a pretask baseline, RT performance elicited a relatively fast, shallow and regular breathing pattern. The pattern of breathing in response to CP was in stark contrast to the RT task, in that a substantial increase in tidal volume, minute ventilation, mean inspiratory flow and breathing irregularity was accompanied by no change in total cycle duration. The implications of these results are discussed with regard to specificity and dimensional models. It is suggested that specificity models might apply to phasic respiratory activity such as breath-holding in disgust and pain. On the other hand, breathing irregularity and expiratory pause duration appears to correspond to emotion dimensions (positive versus negative affect) that cut across the boundaries of emotion categories. Lastly, there were the respiratory patterns that could be more readily interpreted in terms of a task-involvement or active versus passive coping attitude.

Adolescent↗