Autonomic Responses to Affective Visual Stimuli

Thirty-two subjects were categorized by an objective questionnaire as high or low in fear of mutilation. These subjects viewed six slides each from three categories: neutral, incongruous, and mutilation. As predicted, fearful subjects' cardiac responses to mutilation were acceleratory and their counterparts' deceleratory. Both groups reacted to incongruous stimuli with heart rate deceleration. Unexpectedly, both samples displayed cardiac acceleration to the neutral category. Respiratory patterns of initial expiration characterized low-fear subjects whereas inspiration was typical in the high-fear group. However, respiratory activity did not vary over slide types. The high-fear sample emitted electrodermal responses of greater amplitude and slower recovery to mutilation slides than to the other categories. In both respects, the high-fear sample exceeded their counterparts. Finally, fearful subjects exhibited a more pronounced tendency to judge mutilation slides more aversive than incongruous or neutral materials. In general, responses to mutilation materials indicated reactions of defense in fearful subjects and orientation in low-fear persons.     

Attentional Modulation of Early ERP Components in Response to Faces: Evidence From the Attentional Blink Paradigm

The attentional blink (AB) is a transient attentional deficit that occurs when two stimuli that must both be detected are presented within an interval of less than 500 ms. Event-related potential (ERP) investigations have suggested that the AB affects a specific component, the P3, which is suppressed when targets are blinked. In view of the link between the P3 and working memory, it has been suggested that the AB might be due to the inability of the blinked target to access working memory. Interestingly, it seems that faces, due to their saliency, might escape the AB effect when cross-category detection is required (i.e., when the targets are composed of faces versus other categories of stimuli). In the present study we investigated this phenomenon in an event-related potential (ERP) study using upright and inverted faces as targets. In a first task, the participants were asked to identify two successive targets, the first composed of geometric shapes and the second of upright or inverted faces. A second control task, identical to the first was also performed, in which only the second targets had to be identified in order to compare ERPs. ERPs and scalp topographies of physically identical sequences of events, differing only by the attentional involvement, were thus compared. Behavioural results showed that faces indeed escape the AB while inverted faces do not. However, the electrophysiological findings showed that when attention was engaged in a previous stimulus (at the shortest lag times), both upright and inverted faces showed a decreased amplitude in the 150–260 ms time period, in addition to a lower P3. At longer lags, when the AB was no longer observed, no ERP differences were found. Our data demonstrate that, although faces escape the attentional blink, previous attentional involvement occurs much earlier than described for other categories of stimuli. This suggests that faces are subjected to an early selection which might allow rapid re-allocation of attention to the stimulus if it is deemed meaningful.     

Orienting and Defensive Responses to Visual Stimuli

Physiological responses were recorded while 10 females who feared spiders (Group SP) and 10 females who did not (Group NP) viewed 24 neutral and 6 spider slides. Group NP responded to the spider stimuli with heart rate (HR) deceleration and cephalic vasodilation (increase in pulse amplitude), while Group SP responded with HR acceleration and cephalic vasoconstriction. Neither group gave appreciable or systematic cardiovascular responses to the neutral stimuli. Palmar and dorsal skin conductance (SC) responses to the spider stimuli were larger than those given to the neutral slides, and tended to be larger and more resistant to habituation in Group SP than in Group NP. When considered along with post-experimental reports, the responses given by Group NP to the spider slides could be considered to be indicative of an orienting response (OR), while those given by Group SP were consistent with recent conceptions of the defensive response (DR). These response patterns, especially the latter one, were evident in both group data and in individual records.     

A Factor Analysis of Visual Evoked Responses

A factor analysis was performed on 19 visual evoked response (VER) variables and age, in order to identify patterns of relationships among the variables. The analysis resulted in a 7-factor Varimax solution. Subjects were 98 kindergarten children (50 girls and 48 boys) in upper-middle socio-economic class. Mean IQ was 119.5; mean age, 67.16 mo. The five cortical measures of amplitude, latency, correlation, complexity, and linearity, the latter two of which had not been previously measured, were recorded from three scalp locations in response to three types of visual stimulation. Four factors (amplitude, linearity, and two latency factors-one for each of two stimulus conditions) were obtained which showed significant loadings only within a given cortical measure. Three factors (one for each of the stimulus conditions) were obtained which showed significant loadings across different cortical measures. Examination of the correlation matrix, as well as the orthogonal (independent) factor solution, supported the main hypothesis that the VER is a multidimensional domain. Specifically, different stimulus conditions and/or different cortical measures of VER often produced variables which were uncorrelated across subjects.     

Responses of Rabbit Visual Cortex Neurons to Changes in the Orientation and Intensity of Visual Stimuli

We report here studies of changes in the numbers of spikes in the early phasic discharges (50–90 msec from the moment of stimulus substitution) of neurons in the primary visual cortex of conscious rabbits in response to substitution of lines of different orientations (0–90°) but flashing at constant intensity on a screen, to substitution of lines of constant orientation but different intensities, and to substitutions of complex stimuli in which simultaneous changes were made to the orientation and intensity. Factor analysis of the results showed that the number of spikes in the early phasic discharges of some neurons allowed the two-dimensional sensory space of orientations to be reconstructed. This space was identified in 13 of the 43 neurons studied (30%). Five of the 30 cells studied (16.7%) showed both two-dimensional orientation sensory spaces and two-dimensional intensity spaces. Achromatic spaces were reconstructed by substituting lines of different intensity but constant orientation. On substitution of complex stimuli (intensity + orientation), four stimuli with initial orientations of 0–38.58° (0° corresponding to a vertical line) had an intensity of 5 cd/m², while the other four stimuli (with orientations of 51.44–90°) were presented at an intensity of 15 cd/m². On the plane of the sensory space formed by the first two significant factors, the two groups of stimuli with different intensities were located in opposite quadrants of a circle, while within the groups the stimuli were ordered in a sequence close to the order of increases in their slope angles, from smaller angles to greater. It is suggested that in this version, a single sensory plane space reflects the interaction between the orientation and intensity attributes of the visual stimulus, the intensity factor being predominant. A total of seven such cells were found among the 57 studied (12%).     

视觉反馈增益对力量输出影响的行为学研究

视觉反馈对运动功能执行的准确性有重要作用，而视觉反馈增益、反馈延迟时间及反馈频率都会影响运动功能的输出。通过测试不同增益的视觉反馈刺激对握力输出的影响，从行为学上研究视觉反馈增益在运动功能执行中的调节作用。作者设计了变化速度快慢不同的两种力量跟踪任务，在高低不同的两种视觉反馈增益下测定12个受试者力量输出的出错率和偏差两个参数。统计分析表明，视觉反馈增益对力量输出有显著影响；对同样的力量变化速度，视觉反馈增益提高使力量输出的调节作用增强。实验结果提示，视觉反馈增益变化会引起不同皮层区域参与运动功能的执行。     

Visual Evoked Responses (VERs) in Normal and Disabled Readers

The present study investigated the possibility that reading disabled children exhibit abnormal visual evoked responses (VERs). Comparisons were made between a group of disabled children and two control groups of normals, one group matched on age and IQ, and the other on reading level and IQ. VERs were obtained for flashes of light and word stimuli. Results indicated that the reading disabled children showed a significantly smaller amplitude in the negative wave at 180 msec following stimulus onset, for an electrode placed in the region of the left angular gyrus, compared to the two controls. All three groups showed significantly greater negative amplitudes at this latency for the word stimulus compared to the light flash. The results confirm some earlier findings and suggest that a neurological origin of reading disability is likely.     

Attentional Strategy Moderates Effects of Pain Catastrophizing on Symptom-Specific Physiological Responses in Chronic Low Back Pain Patients

In the present study, we examined whether experimentally-manipulated attentional strategies moderated relations between pain catastrophizing and symptom-specific physiological responses to a cold-pressor task among sixty-eight chronic low back patients. Patients completed measures of pain catastrophizing and depression, and were randomly assigned to sensory focus, distraction or suppression conditions during a cold pressor. Lumbar paraspinal and trapezius EMG, and cardiovascular responses to the cold pressor were assessed. Attentional strategies moderated the relation between pain catastrophizing and lumbar paraspinal muscle, but not trapezius muscle or cardiovascular responses. Only for participants in the suppression condition was catastrophizing related significantly to lumbar paraspinal muscle responses. Depressed affect did not account for this relation. These findings indicate that ‘symptom-specific’ responses among pain catastrophizers with chronic low back depend on how they attend to pain-related information. Specifically, it appears that efforts to suppress awareness of pain exaggerate muscular responses near the site of injury.     

Bilateral Asymmetry of Skin Conductance Responses During Auditory and Visual Tasks

Bilateral skin conductance (SC) was recorded while dextral subjects engaged in tasks designed to differentially engage the right (RH) and left (LH) hemispheres. Subjects compared strings of speech sounds (LH) and musical chords (RH). They also decided whether written words rhymed (LH) and viewed pictures of faces in a continuous recognition paradigm (RH). SCRs in the right hand were larger during the chords task than the syllables task. The left hand did not differ for the two stimuli. In the visual experiment a comparable effect was obtained in males only. SCRs in the left hand were larger for rhymes than faces; the right hand did not differentiate between stimuli. Sex differences in laterality are considered. Subjects who were more equally balanced in awareness of the two sides of their bodies and subjects with familial sinistrals were more likely to show task appropriate SC changes. Using rote repetition and visual imagery as mnemonics did not affect SC asymmetries.     

Instrumental Heart Rate Responses and Visual Perception: A Preliminary Study

Five subjects (Ss) were trained to raise and lower their heart rates over a number of operant conditioning sessions. Geometric forms were superimposed upon the conditioned stimuli during the final operant training session. For the conditioning trials, Ss detected significantly more tachistoscopic stimuli during heart rate deceleration trials than during heart rate acceleration trials. During extinction trials, there were no differences in tachistoscopic recognition between acceleration and deceleration trials. The results are discussed in terms of Lacey's hypothesis concerning the instrumental effect of heart rate change on environmental attention.     

Neural Mechanisms of Attentional Switching Between Pain and a Visual Illusion Task: A Laser Evoked Potential Study

Previous studies demonstrated that pain induced by a noxious stimulus during a distraction task is affected by both stimulus-driven and goal-directed processes which interact and change over time. The purpose of this exploratory study was to analyse associations of aspects of subjective pain experience and engagement with the distracting task with attention-sensitive components of noxious laser-evoked potentials (LEPs) on a single-trial basis. A laser heat stimulus was applied to the dorsum of the left hand while subjects either viewed the Rubin vase-face illusion (RVI), or focused on their pain and associated somatosensory sensations occurring on their stimulated hand. Pain-related sensations occurring with every laser stimulus were evaluated using a set of visual analogue scales. Factor analysis was used to identify the principal dimensions of pain experience. LEPs were correlated with subjective aspects of pain experience on a single-trial basis using a multiple linear regression model. A positive LEP component at the vertex electrodes in the interval 294–351 ms (P2) was smaller during focusing on RVI than during focusing on the stimulated hand. Single-trial amplitude variations of the P2 component correlated with changes in Factor 1, representing essential aspects of pain, and inversely with both Factor 2, accounting for anticipated pain, and the number of RVI figure reversals. A source dipole located in the posterior region of the cingulate cortex was the strongest contributor to the attention-related single-trial variations of the P2 component. Instantaneous amplitude variations of the P2 LEP component during switching attention towards pain in the presence of a distracting task are related to the strength of pain experience, engagement with the task, and the level of anticipated pain. Results provide neurophysiological underpinning for the use of distraction analgesia acute pain relief.     

Respiratory Sinus Arrhythmia Predicts Heart Rate and Visual Responses during Visual Attention in 14 and 20 Week Old Infants

The prediction of cardiac attentional responses by respiratory sinus arrhythmia was tested in infants at 14 and at 20 weeks of age. Heart rate, heart rate variability, and respiratory sinus arrhythmia were measured in a 5-min baseline period. Respiration and heart rate responses were recorded during the habituation of infant visual attention. The level of respiratory sinus arrhythmia in the baseline was significantly correlated with the cardiac deceleration, especially in the 20-week-old infants. The relationship between cardiac and respiratory responses during attention was stronger in the 20-week-olds, paralleling the increase in respiratory sinus arrhythmia at this age. Visual fixation durations were also significantly correlated with measures of heart rate variability from the baseline. These results imply that cardiac variability not only predicts the level of cardiac attentional responsivity, but may be useful in the indexing of individual differences in the responsivity of more general attentional systems.     

Visual Signals in the Retina: From Photons to Synapses

The ability to see the world around us is an immediate and striking example of the abilities of the nervous system, and perhaps for this reason, vision is one of the most intensively studied aspects of brain function (Hubel, 1995). This paper examines some of the earliest steps in vision occurring in the retina (Dowling, 1987; Rodieck, 1998).     

Structure of Reciprocal Connections of Visual Cortical Fields 17 and 18 in the Cat

Microiontophoretic application of horseradish peroxidase to individual columns in fields 17 and 18 of the cat cortex was used to identify the distribution by area and layer of retrograde labeled cells in both fields. After application of marker to fields 17 or 18, the area of labeled cells in field 17 (in the tangential plane) was extended and orientated along the projection of the horizontal meridian of the field of vision. The area of labeled cells in field 18 in these cases was orientated along the projections of the vertical meridian. Similar differences in the organization of the connections of fields 17 and 18 were seen in the projection zone of the central 10° of the field of vision at different elevations. Thus, the spatial distributions of internal and external connections in each field coincide and their orientations in fields 17 and 18 are mutually perpendicular. It is suggested that field 17 performs the more detailed analysis of information on the horizontal components of an image and communicates this to field 18, while field 18 is responsible for the more detailed analysis of information about the vertical components of the same image, communicating this to field 17.