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PubMed1992

An inside-out theory of attention.

The brain has two attentional systems; one attentional system is devoted to intrapersonal space and the second attentional system to extrapersonal space. The development of these two attentional systems with inward or outward focus arose from the hemispheral neural systems designed for attending to extrapersonal contralateral space. As a necessary consequence of the brain changes to develop language, one of the hemispheral attentional systems was altered for intrapersonal attention while the other hemispheral attentional system became obligated to attend to all of extrapersonal space. This conceptualization of attention provides a coherent explanation for the confusing hemispheral dominance proposed for attention on the basis of clinical hemineglect, i.e. that the left hemisphere attends to right extrapersonal space and that the right hemisphere attends to both left and right extrapersonal space. This conceptualization also provides a meaningful account of denial of limbs (anosognosia) and imagery.

Animals↗
PubMed2004

The attentional selection of spatial and non-spatial attributes in touch: ERP evidence for parallel and independent processes.

To investigate the functional relationship between spatial and non-spatial attentional selectivity in somatosensory processing, event-related potentials (ERPs) were recorded to mechanical tactile stimuli, which were delivered to the right or left hand, and were low or high in frequency (Experiment 1), or soft or strong in intensity (Experiment 2). Participants' task was to attend to a specific combination of one stimulus location and one non-spatial attribute. Spatial attention was reflected in enhanced N140 components followed by a sustained attentional negativity. ERP effects of non-spatial attention (enhanced negativities to the attended frequency or intensity) were observed in the same latency range, suggesting that the attentional selection of relevant spatial and non-spatial attributes occurs in parallel. Most importantly, ERP correlates of attention directed to stimulus frequency and intensity were unaffected by the current focus of spatial attention. In contrast to vision, where the selective processing of non-spatial attributes is hierarchically dependent on selection by location, but similar to auditory attention, spatial and non-spatial attentional selectivity appear to operate independently in touch.

Adult↗
PubMed2006

Spatiotemporal overlap between brain activation related to saccade preparation and attentional orienting.

Recent brain imaging studies provided evidence that the brain areas involved with attentional orienting and the preparation of saccades largely overlap, which may indicate that focusing attention at a specific location can be considered as an unexecuted saccade towards that location (i.e. the premotor theory of attention). Alternatively, it may be proposed that attentional orienting is simply relevant for preparing saccades, but the two processes may also be completely unrelated. In two experiments, we examined temporal activation of brain areas by measuring the electroencephalogram. Central cues indicated the likely side (left or right) at which a to-be-attended target would occur, or to which a saccade had to be prepared. Cue direction-related activity was determined, time-locked to cue onset. In addition, in our second experiment, delayed saccades had to be carried out, which allows to focus on processes strongly related to saccade execution. In nearly all tasks, an early directing attention negativity (EDAN), an anterior directing attention negativity (ADAN), and a late directing attention positivity (LDAP) were observed, time-locked to cue onset. Source analyses supported the view that this activity probably originates from areas within the ventral intraparietal sulcus (vIPS) and the frontal eye fields (FEF). The saccade-locked analysis also indicated that the FEF plays an important role in triggering saccades, but the role of vIPS appears to be minimal. The latter finding disfavors the premotor theory of attention, as it suggests that the relation between attention and action is less direct.

Adult↗
PubMed2006

The effect of visual task difficulty and attentional direction on the detection of acoustic change as indexed by the Mismatch Negativity.

Näätänen's model of auditory processing purports that attention does not affect the MMN. The present study investigates this claim through two different manipulations. First, the effect of visual task difficulty on the passively elicited MMN is assessed. Second, the MMNs elicited by stimuli under attended and ignored conditions are compared. In Experiment 1, subjects were presented with mixed sequences of equiprobable auditory and visual stimuli. The auditory stimuli consisted of standard (80 dB SPL 1000 Hz), frequency deviant (1050 Hz), and intensity deviant (70 dB SPL) tone pips. In a first instance, subjects were instructed to ignore the auditory stimulation and engage in an easy and difficult visual discrimination task (focused condition). Subsequently, they were asked to attend to both modalities and detect visual and auditory deviant stimuli (divided condition). The results indicate that the passively elicited MMN to frequency and intensity deviants did not significantly vary with visual task difficulty, in spite of the fact that the easy and difficult tasks showed a wide variation in performance. The manipulation of the attentional direction (focused vs. divided conditions) did result in a significant effect on the MMN elicited by the intensity, but not frequency, deviant. The intensity MMN was larger at frontal sites when subjects' attention was directed to both modalities as compared to only the visual modality. The attentional effect on the MMN to the intensity deviants only may be due to the specific deviant feature or the poorer perceptual discriminability of this deviant from the standard. Experiment 2 was designed to address this issue. The methods of Experiment 2 were identical to those of Experiment 1 with the exception that the intensity deviant (60 dB SPL) was made to be more perceptible than the frequency deviant (1016 Hz) when compared to the standard stimulus (80 dB SPL 1000 Hz). The results of Experiment 2 also demonstrated that the passively elicited MMN was not affected by large variations in visual task difficulty; this provides convincing evidence that the MMN is independent of visual task demands. Similarly to Experiment 1, the direction of attention again had a significant effect on the MMN. In Experiment 2, however, the frequency MMN (and not the intensity MMN) was larger at frontal sites during divided attention compared to focused visual attention. The most parsimonious explanation of these results is that attention enhances the discriminability of the deviant from the standard background stimulation. As such, small acoustic changes would benefit from attention whereas the discriminability of larger changes may not be significantly enhanced.

Acoustic Stimulation↗
PubMed2007

ERP correlates of shared control mechanisms involved in saccade preparation and in covert attention.

We investigated whether attention shifts and eye movement preparation are mediated by shared control mechanisms, as claimed by the premotor theory of attention. ERPs were recorded in three tasks where directional cues presented at the beginning of each trial instructed participants to direct their attention to the cued side without eye movements (Covert task), to prepare an eye movement in the cued direction without attention shifts (Saccade task) or both (Combined task). A peripheral visual Go/Nogo stimulus that was presented 800 ms after cue onset signalled whether responses had to be executed or withheld. Lateralised ERP components triggered during the cue-target interval, which are assumed to reflect preparatory control mechanisms that mediate attentional orienting, were very similar across tasks. They were also present in the Saccade task, which was designed to discourage any concomitant covert attention shifts. These results support the hypothesis that saccade preparation and attentional orienting are implemented by common control structures. There were however systematic differences in the impact of eye movement programming and covert attention on ERPs triggered in response to visual stimuli at cued versus uncued locations. It is concluded that, although the preparatory processes underlying saccade programming and covert attentional orienting may be based on common mechanisms, they nevertheless differ in their spatially specific effects on visual information processing.

Adult↗
PubMed2005

Unraveling the attentional functions of cortical cholinergic inputs: interactions between signal-driven and cognitive modulation of signal detection.

Neurophysiological studies demonstrated that increases in cholinergic transmission in sensory areas enhance the cortical processing of thalamic inputs. Cholinergic activity also suppresses the retrieval of internal associations, thereby further promoting sensory input processing. Behavioral studies documented the role of cortical cholinergic inputs in attentional functions and capacities by demonstrating, for example, that the integrity of the cortical cholinergic input system is necessary for attentional performance, and that the activity of cortical cholinergic inputs is selectively enhanced during attentional performance. This review aims at integrating the neurophysiological and behavioral evidence on the functions of cortical cholinergic inputs and hypothesizes that the cortical cholinergic input system generally acts to optimize the processing of signals in attention-demanding contexts. Such signals 'recruit', via activation of basal forebrain corticopetal cholinergic projections, the cortical attention systems and thereby amplify the processing of attention-demanding signals (termed 'signal-driven cholinergic modulation of detection'). The activity of corticopetal cholinergic projections is also modulated by direct prefrontal projections to the basal forebrain and, indirectly, to cholinergic terminals elsewhere in the cortex; thus, cortical cholinergic inputs are also involved in the mediation of top-down effects, such as the knowledge-based augmentation of detection (see Footnote 1) of signals and the filtering of irrelevant information (termed 'cognitive cholinergic modulation of detection'). Thus, depending on the quality of signals and task characteristics, cortical cholinergic activity reflects the combined effects of signal-driven and cognitive modulation of detection. This hypothesis begins to explain signal intensity or duration-dependent performance in attention tasks, the distinct effects of cortex-wide versus prefrontal cholinergic deafferentation on attention performance, and it generates specific predictions concerning cortical acetylcholine (ACh) release in attention task-performing animals. Finally, the consequences of abnormalities in the regulation of cortical cholinergic inputs for the manifestation of the symptoms of major neuropsychiatric disorders are conceptualized in terms of dysregulation in the signal-driven and cognitive cholinergic modulation of detection processes.

Acetylcholine↗
PubMed2005

Attention induces reciprocal activity in the human somatosensory cortex enhancing relevant- and suppressing irrelevant inputs from fingers.

OBJECTIVE: We studied whether attention regulates information processing in the human primary somatosensory cortex (SI) by selective enhancement of relevant- and suppression of irrelevant information. METHODS: Under successive and simultaneous electric stimuli to both the right index and middle fingers, tactile stimuli were randomly (20%) presented on one of the two fingers in separate two runs exchanging the finger. Subjects were requested to discriminate the tactile stimuli in an attention task to induce attention to one finger and to ignore the stimuli in a control task to avoid such an attention focus. Somatosensory evoked magnetic fields were measured only for the two-finger electric stimulation and an early component (M50) was analyzed. RESULTS: In spite of the two-finger simultaneous stimulation, attention to either the index or middle finger lowered or heightened the M50-sourse location, respectively. The attention task did not increase the M50 amplitude. CONCLUSIONS: Attention to a finger enhanced selectively the representation of the finger in the SI cortex. However, this SI activity did not increase the M50 amplitude, suggesting that the attention suppressed another finger region receiving the unattended inputs. SIGNIFICANCE: Attention regulates the SI activity by selectively enhancing the task-relevant information and by filtering out other noise inputs.

Adult↗
PubMed2004

Exogenous orienting of attention depends upon the ability to execute eye movements.

Shifts of attention can be made overtly by moving the eyes or covertly with attention being allocated to a region of space that does not correspond to the current direction of gaze. However, the precise relationship between eye movements and the covert orienting of attention remains controversial. The influential premotor theory proposes that the covert orienting of attention is produced by the programming of (unexecuted) eye movements and thus predicts a strong relationship between the ability to execute eye movements and the operation of spatial attention. Here, we demonstrate for the first time that impaired spatial attention is observed in an individual (AI) who is neurologically healthy but who cannot execute eye movements as a result of a congenital impairment in the elasticity of her eye muscles. This finding provides direct support for the role of the eye-movement system in the covert orienting of attention and suggests that whereas intact cortical structures may be necessary for normal attentional reflexes, they are not sufficient. The ability to move our eyes is essential for the development of normal patterns of spatial attention.

Adult↗
PubMed2004

Cognitive impairments in sober alcoholics: performance on selective and divided attention tasks.

AIMS: The aim of this study was to investigate performance on neuropsychological tasks and tasks measuring different aspects of attention in a representative sample of sober alcoholics. METHODS: The study followed a between-groups design whereby sober alcoholics were compared to a matched non-alcoholic control group. The alcoholics were recruited from a six-week residential rehabilitation unit for addicts. A total of 98 alcoholics (64 males) and 30 non-alcoholic controls (22 males) participated in the study. The alcoholics were assessed on four standard neuropsychological tasks and three attention tasks from cognitive experimental literature targeted towards measuring attention. RESULTS: In comparison to a non-alcoholic control group the alcoholics were significantly impaired on all neuropsychological tasks, the divided attention task and the Stroop task. However, a normal pattern of performance for the alcoholics appears in the Eriksen task, a measure of selective attention. Alcoholics also showed elevated levels of negative affect at treatment intake. CONCLUSION: It is concluded that a representative sample of alcoholics show specific deficits of attention as opposed to a general decline of attention at treatment intake. Thus, sober alcoholics appear to be as efficient as controls at selecting on the basis of location. Nonetheless when they are required to select on the basis of semantic information, as in the Stroop task, or required to respond to two independent sources of information, as in the divided attention task, they are at a deficit. This study has added to previous research by highlighting the specific attentional processes impaired in alcoholics.

Adult↗
PubMed2005

Attention and executive functions in remitted major depression patients.

BACKGROUND: Although deficits in attention and executive functions in patients with Major Depressive Disorder (MDD) are well confirmed [Veiel, H.O.F., 1997. A preliminary profile of neuropsychological deficits associated with major depression. Journal of Clinical and Experimental Neuropsychology 19, 587-603.]. The database regarding the relationship between impairments and the duration of disease or the number of episodes is inconsistent. Furthermore, the role of long-term cognitive impairments in MDD during remitted state is not well understood [Elliott, R., 2002. The neuropsychological profile in primary depression. Taylor and Francis, London, pp. 273-293.]. There is consequently a lack of studies accounting for different courses of illness in the euthymic state and considering the influence of possible attentional deficits on executive performance. METHODS: 40 euthymic patients with MDD diagnosis according to DSM-IV (20 patients with 1-2 episodes and 20 severe depressives with at least three episodes) as well as 20 healthy controls matched for education and age were administered three tests for attention (attentional shift, Stroop task, sustained attention) and three for executive functions (BADS, word fluency, memory span). The methods selected were theory based with regard to an involvement of frontal-subcortical networks in MDD, attention, and executive functions, respectively. RESULTS: Euthymic patients with MDD showed deficits in all tests related to attentional and executive functions compared to healthy controls. The patient groups did not differ with regard to attentional performance. Executive functions in severe depressives were more impaired than in mild depressives. LIMITATIONS: Differing performances of the patient groups in the subtests of the executive test battery (BADS) can only be interpreted to a limited extent. CONCLUSIONS: The results support the assumption that deficits in attention and executive functions in MDD show an increase in trait character and executive function during chronic course. Implications for differential diagnosis and cognitive psychotherapy are discussed.

Adult↗
PubMed2006

The relationship between cognitive avoidance and attentional bias for snake-related thoughts.

Building on the work of Lavy and van den Hout (Lavy, E. H., & van den Hout, M. A. (1994a). Cognitive avoidance and attentional bias: Causal relationships. Cognitive Therapy and Research, 18 (2) 179-191; Lavy, E. H., & van den Hout, M. A. (1994b). Cognitive avoidance and attentional bias: Causal relationships. Behavior Therapy, 24, 645-657), the purpose of the present study was to examine a functional relationship between thought suppression and attentional bias for snake-related thoughts. It was hypothesized that thought suppression is causally involved in the emergence of attentional bias. An experiment was conducted with 71 snake-fearful and non-snake-fearful participants to investigate whether instructions for suppression were sufficient to induce an attentional bias toward snake-related words. Thirty-five participants were instructed to suppress all snake-related thoughts, while 36 participants received control instructions. Both groups then completed a 5-min stream of consciousness exercise followed by a dot-probe attention task including snake words, general emotion words, and neutral words. Results indicated that participants instructed to suppress snake-related thoughts exhibited a more pronounced attentional bias toward snake-related word pairs. The same participants did not exhibit an attentional bias toward general emotion or neutral words. Moreover, there was a significant negative correlation between snake-related thoughts and probe detection latency. Results are interpreted as providing support for a causal relationship between thought suppression and attentional bias for snake-related thoughts.

Adolescent↗
PubMed2005

Control of attention in schizophrenia.

The deficits of attention contribute significantly to the clinical picture of functional disability seen in schizophrenia, but there is no consensus as to whether this cognitive function can be fractionated to allow further characterisation of the impairment. We examined fifteen patients with chronic schizophrenia and fifteen controls using paired tasks designed to measure four hypothetical aspects of attentional control: the ability to focus attention, to resist distraction, to shift attention, and to divide attention. The group with schizophrenia showed a significant improvement in accuracy on a digit span repetition task when a simultaneous box-crossing task was added (divided attention condition). Although the patient group showed impaired performance across nearly all of the tasks, they were not disproportionately impaired during the task conditions assumed to demand greater attention. These results suggest that the aspects of attention and executive function under study are not significantly affected by schizophrenia and indicate the need for further characterisation of the impairment usually reported using conventional tests of attention on those with schizophrenia.

Adult↗
PubMedDate not supplied

Separate neural definitions of visual consciousness and visual attention; a case for phenomenal awareness.

What is the relation between visual attention and visual awareness? It is difficult to imagine being aware of something without attending to it, and by some, visual consciousness is simply equated to what is in the focus of attention. However, findings from psychological as well as from neurophysiological experiments argue strongly against equating attention and visual consciousness. From these experiments clearly separate neural definitions of visual attention and visual consciousness emerge. In the model proposed here, visual attention is defined as a convolution of sensori-motor processing with memory. Consciousness, however, is generated by recurrent activity between cortical areas. The extent to which these recurrent interactions involve areas in executive or mnemonic space depends on attention and determines whether a conscious report is possible about the sensory experience, not whether the sensory experience is there. This way, a strong case can be made for a pure non-cognitive form of seeing, independent of attentional selection, called phenomenal awareness. This can be dissociated from the reportable form, depending on attention, called access awareness. The hypothesis explains why attention and consciousness seem so intricately related, even though they are fully separate phenomena.

Attention↗
PubMed2005

The interaction of attention and emotion.

We analyse emotions from the viewpoint of how emotion and attention interact in the brain. Much has been learnt about the brain structures involved in attention, especially in vision. In particular the manner in which attention functions as a high-level control system, able to make cognitive processing so effective, has been studied both at a global level by brain imaging (fMRI, PET, MEG and EEG), at a local single cell level in monkeys and lower animals, and computationally by a variety of models. The manner in which emotions impinge on this attention control system is not so well analysed, although numerous new results are now emerging from using the same tools. Here we use an engineering control approach to attention to model it in a global manner but with relatively sure local foundations at singe neuron level. The manner in which emotional value (as coded in amygdale and orbito-frontal cortex) can interact with the attention control circuitry is analysed using results of various experimental paradigms. A general model of this interaction is first developed and tested against a list of paradigms, and then more detailed computations are performed using more specific features of the attention control system and the limbic value coding. These computations are completed by a simulation of the emotional attentional blink, a demanding paradigm for any model of attention alone, but made more so by the presence of emotional value codes for stimuli. We conclude the paper with a general discussion of further avenues of research.

Animals↗
PubMed2006

Changing channels: an fMRI study of aging and cross-modal attention shifts.

Age-related deficits in visual selective attention suggest that the efficiency of inhibitory processes is particularly affected by aging. To investigate whether processing inefficiencies observed in visual attention are similar in auditory attention and when shifting attention across modalities, we conducted an fMRI study with healthy young and older adults using a task that required sustained auditory and visual selective attention and cross-modal attention shifts. Older adults in this study performed as well as the younger adults, but showed age-related differences in BOLD responses. The most striking of these differences were bilateral frontal and parietal regions of significantly increased activation in older adults during both focused and shifting attention. Our data suggest that this increased activation did not reflect new recruitment, but reliance on brain regions typically used by younger adults when task demands are greater. Older adults' activation patterns suggested that even during focused attention conditions they were "shifting" attention to stimuli in the unattended modality. Increased activation during processing of both task-relevant and task-irrelevant information implies age-related loss of processing selectivity. These patterns may reflect both task-specific compensatory neural recruitment and degradation of sensory inhibition.

Acoustic Stimulation↗
PubMed2006

The effect of visuospatial attentional load on the processing of irrelevant acoustic distractors.

This work investigated the role of cognitive control functions in selective attention when task-relevant and -irrelevant stimuli come from different sensory modalities. We parametrically manipulated the load of an attentive tracking task and investigated its effect on irrelevant acoustic change-related processing. While subjects were performing the visual attentive tracking task, event-related potentials (ERPs) were recorded for frequent standard tones and rare deviant tones presented as auditory distractors. The deviant tones elicited two change-related ERP components: the mismatch negativity (MMN) and the P3a. The amplitude of the MMN, which indexes the early detection of irregular changes, increased with increasing attentional load, whereas the subsequent P3a component, which indicates the involuntary orienting of attention to deviants, was significant only in the lowest load condition. These findings suggest that active exclusion of the early detection process of irrelevant acoustic changes depends on available resources of cognitive control, whereas the late involuntary orienting of attention to deviants can be passively suppressed by high demand on central attentional resources. The present study thus reveals opposing visual attentional load effects at different temporal and functional stages in the rejection of deviant auditory distractors and provides a new perspective on the resolution of the long-standing early versus late attention selection debate.

Adult↗
PubMed2004

Attention enhances adaptability: evidence from motion adaptation experiments.

Several previous psychophysical and neurophysiological studies have investigated the separate effects of attention and adaptation on visual processing. Here, we investigated the combined effects of attention and adaptation on motion processing by measuring the effects of spatial attention on the duration of the motion after-effect (MAE) over a wide range of stimulus contrasts. MAE duration was compared between two conditions: full-attention, subjects were required to pay attention to the adapting motion stimulus, and poor-attention, subjects performed a difficult vowel detection task at the center of gaze and ignored the adapting motion stimulus. Attention was found to increase the MAE duration by a factor of 1.4, which was approximately constant over a wide range of stimulus contrasts (3.22-80.6%). Notably, this included contrasts for which the MAE duration had reached its asymptotic value. We show that a quantitative model based on known properties of directionally selective MT neurons can explain these results by assuming that attention enhances the effects of adaptation, a phenomenon we refer to as "adaptation gain". Specifically, attending to an adapting motion stimulus shifts the semi-saturation point (C50) of the underlying contrast response function (CRF) of motion detectors roughly 1.4-fold more to the right than does ignoring that same stimulus. By enhancing the effects of adaptation in this fashion, attention is predicted to enhance the adaptability of the visual motion system.

Adaptation, Physiological↗
PubMed1988

The effects of orientation and maintenance of attention on hemispheric asymmetry for speech perception.

The contributions of orientation and maintenance of attention to the measurement of ear asymmetry was investigated in 20 right handed subjects. The subject listened to dichotic lists and had to respond to a target word in either the male or the female voice only (focused attention), or both voices (divided attention). At random positions throughout the lists the voices changed ears. A switch in voices from one side of space to the other interfered with speech processing during focused attention, but facilitated the detection of targets during divided attention. The interference was greater for the left than the right ear during focused attention. Likewise, facilitation during divided attention was asymmetrical, with right targets receiving faster processing. The qualitative differences of attention strategy on ear asymmetry during dichotic listening may be due to hemispheric differences in preferred attentional modes.

Adult↗