Primary Visual Task Research Articles

Explicit attention interferes with selective emotion processing in human extrastriate cortex

BackgroundBrain imaging and event-related potential studies provide strong evidence that emotional stimuli guide selective attention in visual processing. A reflection of the emotional attention capture is the increased Early Posterior Negativity (EPN) for pleasant and unpleasant compared to neutral images (~150–300 ms poststimulus). The present study explored whether this early emotion discrimination reflects an automatic phenomenon or is subject to interference by competing processing demands. Thus, emotional processing was assessed while participants performed a concurrent feature-based attention task varying in processing demands.ResultsParticipants successfully performed the primary visual attention task as revealed by behavioral performance and selected event-related potential components (Selection Negativity and P3b). Replicating previous results, emotional modulation of the EPN was observed in a task condition with low processing demands. In contrast, pleasant and unpleasant pictures failed to elicit increased EPN amplitudes compared to neutral images in more difficult explicit attention task conditions. Further analyses determined that even the processing of pleasant and unpleasant pictures high in emotional arousal is subject to interference in experimental conditions with high task demand. Taken together, performing demanding feature-based counting tasks interfered with differential emotion processing indexed by the EPN.ConclusionThe present findings demonstrate that taxing processing resources by a competing primary visual attention task markedly attenuated the early discrimination of emotional from neutral picture contents. Thus, these results provide further empirical support for an interference account of the emotion-attention interaction under conditions of competition. Previous studies revealed the interference of selective emotion processing when attentional resources were directed to locations of explicitly task-relevant stimuli. The present data suggest that interference of emotion processing by competing task demands is a more general phenomenon extending to the domain of feature-based attention. Furthermore, the results are inconsistent with the notion of effortlessness, i.e., early emotion discrimination despite concurrent task demands. These findings implicate to assess the presumed automatic nature of emotion processing at the level of specific aspects rather than considering automaticity as an all-or-none phenomenon.

FMRI reveals that involuntary visual deviance processing is resource limited

Previous studies suggest that involuntary auditory attention evoked by unattended auditory stimuli is not influenced by the primary focus of attention. However, prior studies from our laboratory have found that processing of unattended auditory deviant tones in the auditory and frontal regions is modulated by top-down attentional demands and resource availability. Whether processing of unattended visual deviant stimuli is altered by the availability of attentional resources has not been established. The goal of the current study was to examine the automaticity of these activations, their modulation by attentional capacity, and the neuroanatomical distribution of any attentional effects upon visual deviance detection. We designed an event-related functional magnetic resonance imaging (fMRI) study during which subjects performed a continuous perceptual–motor–visual tracking task whose difficulty was modulated by changing the control dynamics of a joystick. Changes in the anatomical localization, spatial distribution, and intensity of the blood oxygenation level-dependent (BOLD) response associated with unattended infrequent visual changes were examined during low- and high-difficulty tracking conditions of the primary visual task. Results revealed that the unattended deviants elicited BOLD activation in the visual, fusiform, and parietal regions. In these regions, the intensity and extent of the activation evoked by the deviants decreased as a function of the demands of the primary visual task. These findings suggest that processing of unattended visual deviant stimuli is restricted by the attentional demands of a primary task, as previously demonstrated for unattended auditory deviant tones.

A methodology to control for individual differences in dual-task performance

A study was designed to test the effect of a secondary visual task on a primary visual task. In one condition, participants performed the dual-task, while assigning no weight to the secondary task. In the second condition, the primary task was performed simultaneously with the secondary task. The effect of the added workload was measured via the effect on primary task performance. In the baseline portion of the task, participants had their baseline (90% accuracy) of performance collected by adjusting the stimulus duration. The individual participant stimulus duration was then used as the experimental stimulus duration and the effect of secondary task performance on primary task performance was measured. In a third condition, practice was used as a method of controlling for individual differences. Participants performed the task as in the control condition, however they were given twice as much exposure to the task. Participants ran the study for the full duration twice. Only the performance from the second exposure was collected.

Inhibitory motor control in children with attention-deficit/hyperactivity disorder: event-related potentials in the stop-signal paradigm

BackgroundThe aim of the study was to investigate the inhibitory control of an ongoing motor response and to identify underlying neural deficiencies, manifested in event-related potentials, that cause poorer inhibitory performance in children with attention-deficit/hyperactivity disorder. MethodsA stop-signal paradigm with a primary visual task and auditory stop signal was used to compare performance in 13 children with attention-deficit/hyperactivity disorder and 13 control children, while event-related potentials were recorded simultaneously. ResultsChildren with attention-deficit/hyperactivity disorder showed poorer inhibitory performance through a slower inhibitory process. Inhibitory processing of auditory stop signals was marked by a frontal N2 component that was reduced in the attention-deficit/hyperactivity disorder group relative to controls. A central positive component (P3) was associated with the success of inhibiting a response, but there were no group differences in its amplitude or latency. ConclusionsFindings support the hypothesis of deficient inhibitory control in children with attention-deficit/hyperactivity disorder. Slower inhibitory processing appears to be due to a specific neural deficiency that manifests in the processing of the stop signal as attenuated negativity in the N2 latency range.

Controlling for Individual Differences in a Dual-Task Setting: Equating the Baselines of Single Task Performance

Individual differences in human performance is an issue that confounds many studies and has not been properly controlled in the ergonomics/human factors literature. This paper examines the concept of individual differences in performance primarily from the perspective of cognitive performance. A study was designed to test the effect of a secondary visual task on a primary visual task. In one condition, participants performed the dual task, while assigning no weight to the secondary task. In the second condition, the primary task was performed simultaneously with the secondary task. The effect of the added workload was measured via the effect on primary task performance. In the baseline portion of the task participants had their baseline (80–90% accuracy) of performance collected by adjusting the stimulus duration. The individual participant stimulus duration was then used as the experimental stimulus duration and the effect of secondary task performance on primary task performance was measured.

Individual differences in energetic arousal and sustained attention: a dual-task study

Abstract Studies of sustained attention and controlled visual search suggest that individual differences in energetic arousal are correlated with availability of resources for demanding attentional tasks. However, most of the evidence for this resource hypothesis is derived from studies of single tasks, in which it is difficult to distinguish effects of energy on resource availability from effects on the subject's strategy for allocation of resources across task components. We report a dual-task study of energy and sustained attention, which provides a more powerful test of the hypothesis. High and low energy individuals performed a primary visual vigilance task, in conjunction with either an auditory (n=52) or a visual (n=50) secondary reaction-time task. Primary task stimuli were presented at two levels of stimulus degradation, as a manipulation of resource limitation. No effects of energy were observed when the secondary task was auditory, but the primary task performance of high energy individuals was superior when the secondary task was visual and primary task stimulus discriminability was low. Results are consistent with previous work on energy and single-task performance suggesting that energetic arousal is associated with individual differences in resource availability, but they also illustrate the importance of careful control of task parameters.

Effects of face inversion on the structural encoding and recognition of faces: Evidence from event-related brain potentials

It was investigated how face inversion affects face-specific components of event-related brain potentials (ERPs) which are assumed to reflect the structural encoding and the recognition of faces. ERPs were recorded to upright and inverted photographs of familiar faces, unfamiliar faces, and houses. In Part I, participants had to detect infrequently presented targets (hands), in Part II, attention was either directed towards or away from the pictorial stimuli. When compared with upright unfamiliar faces, upright familiar faces elicited an enhanced negativity between 300 ms and 450 ms (‘N400f’) and an enhanced positivity between 450 and 650 ms post-stimulus (‘P600f’). It is suggested that these ERP modulations are generated by processes involved in the recognition of faces. Face inversion is known to disrupt face recognition processes. Accordingly, ‘N400f’ and ‘P600f’ were generally absent in response to inverted familiar and unfamiliar faces. The face-specific N170 component at lateral posterior electrodes was not affected by face familiarity, indicating that it reflects processing stages prior to face identification. N170 was delayed and enhanced for inverted relative to upright faces. While N170 enhancements were also observed for inverted relative to upright houses, the N170 latency shift caused by stimulus inversion was face-specific. Directing attention away from the faces towards a demanding primary visual task resulted in an N170 delay for inverted as well as for upright faces, suggesting that the time course of structural encoding of faces is affected by attentional factors. These results demonstrate that ERPs can be used as electrophysiological markers of specialised brain processes underlying the structural encoding and subsequent recognition of faces.

Source document position as it affects head position and neck muscle tension.

Measurements of head position, mechanical load at C7, and level of muscle EMG activity in the muscles of the neck were compared across six document positions in both a reading task and a typing (word processing) task. Source documents, identified as a primary visual task, were placed in two positions in front of the subject, flat on the table to each side of the keyboard, and on a document stand at each side of the keyboard. Each of the 20 subjects performed both a reading task and a typing task in each of these document positions while measurements were taken. It was found that the greatest variations in head position occurred in head rotation with documents flat on the table. This document position on each side also produced the greatest level of muscle tension in both the neck extensors and, to a lesser degree, the sternocleidomastoid muscles. In addition, greater variability between document position measures was found in the typing condition.

Regional differences in photoreceptor performance in the eye of the praying mantis

1. Photoreceptor spacing, and angular, spectral, absolute and relative sensitivities have been measured across the compound eye of the praying mantisTenodera australasiae using optical and electrophysiological techniques. 2. Together, the two compound eyes cover virtually all spatial directions. The huge binocular fields extend vertically 240° with a maximum horizontal overlap of 35° in the frontal part of the eye (Fig. 2). 3. Interommatidial angles (Δφ) range from 0.6° in the frontal eye region up to 2.5° in edge regions of the eye (Fig. 5; Table 1). The eye region with minimumΔφ-values is defined as a fovea. 4. The acceptance angles (Δρ) of light-adapted photoreceptors are almost equal to the interommatidial angles over the whole eye (Δρ is 0.7° in the fovea and 2.5° in the edge of the eye) (Fig. 6; Table 1). The measured values ofΔρ are close to those predicted by the theories of Snyder (1977) and Horridge and Duelli (1979) from the optical and anatomical dimensions of the eye. In this context, the facet diameters are larger and the crystalline cones are longer in the fovea than elsewhere, whereas the rhabdom diameters are smaller. It is concluded that diffraction limitsΔρ in the fovea, whereas the acceptance function of the rhabdom limitsΔρ in eye regions outside the fovea (Fig. 16). 5. The angular sensitivity depends on the state of light adaptation and the time of day. In a defined foveal region the photoreceptors have mean acceptance angles of 0.74° (S.D. = 0.1°) when light-adapted, 1.1° (S.D. = 0.2°) when dark-adapted in daytime, and 2° (S.D. = 0.4°) when dark-adapted at night. The corresponding angles for a defined dorsal eye region are 2.4° (S.D. = 0.3°), 3.2° (S.D. =0.3°), and 6° (S.D.= 0.5°) (Fig. 10). 6. All units recorded from have similar spectral sensitivities, with a maximum in the wavelength range 500 nm to 520 nm, and a weak secondary peak around 370 nm (Fig. 12). 7. Dark-adapted photoreceptors produce bumps whose mean amplitude varies from cell to cell from 1 to 3 mV. Retinular cells in the defined foveal and dorsal eye regions have almost identical quantum capture sensitivities (defined as number of bumps per incident peak axial photons per cm2). Consequently foveal photoreceptors must have a lower quantum capture efficiency (defined as the number of bumps per incident peak axial photons perfacet), because their ommatidia have larger facet diameters. The quantum capture efficiencies are 0.04 (S.D. = 0.02) in the fovea and 0.10 (S.D. = 0.02) in the dorsal eye (Fig. 13; Table 2). This finding supports theoretical predictions that the acceptance function of the rhabdom of foveal photoreceptors is narrowed to decreaseΔρ. 8. Absolute and relative sensitivities of photoreceptors, defined as the reciprocal of the quantal flux required to generate a voltage response of 50% maximum, were determined in the defined foveal and dorsal eye regions. To a point source dark adapted retinula cells from both eye regions have almost identical sensitivities (Fig. 14b, c; Table 3). However, to a large diffuse source, dark-adapted foveal photoreceptors with their relatively small acceptance angles are less sensitive than receptors in the dorsal eye with their largeΔρ values, and retinula cells of both eye regions are more sensitive at night than during the day because their fields of view are broadened (Fig. 14d, e; Table 4). 9. The primary visual task of the praying mantis is the recognition and localization of prey moving against a disrupted background. Prey capture mainly occurs during the day, while the sexual behaviour takes place at night. Some relations between the eye performance and the visual behaviour are discussed.