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Biomedical subjects

A K Anderson

Publications and source records attributed to A K Anderson.

At least 19 recordsLinked to original sources
PubMed2007

Human and computer recognition of facial expressions of emotion.

Neuropsychological and neuroimaging evidence suggests that the human brain contains facial expression recognition detectors specialized for specific discrete emotions. However, some human behavioral data suggest that humans recognize expressions as similar and not discrete entities. This latter observation has been taken to indicate that internal representations of facial expressions may be best characterized as varying along continuous underlying dimensions. To examine the potential compatibility of these two views, the present study compared human and support vector machine (SVM) facial expression recognition performance. Separate SVMs were trained to develop fully automatic optimal recognition of one of six basic emotional expressions in real-time with no explicit training on expression similarity. Performance revealed high recognition accuracy for expression prototypes. Without explicit training of similarity detection, magnitude of activation across each emotion-specific SVM captured human judgments of expression similarity. This evidence suggests that combinations of expert classifiers from separate internal neural representations result in similarity judgments between expressions, supporting the appearance of a continuous underlying dimensionality. Further, these data suggest similarity in expression meaning is supported by superficial similarities in expression appearance.

Artificial Intelligence↗
PubMed2006

Positive affect increases the breadth of attentional selection.

The present study examined the thesis that positive affect may serve to broaden the scope of attentional filters, reducing their selectivity. The effect of positive mood states was measured in two different cognitive domains: semantic search (remote associates task) and visual selective attention (Eriksen flanker task). In the conceptual domain, positive affect enhanced access to remote associates, suggesting an increase in the scope of semantic access. In the visuospatial domain, positive affect impaired visual selective attention by increasing processing of spatially adjacent flanking distractors, suggesting an increase in the scope of visuospatial attention. During positive states, individual differences in enhanced semantic access were correlated with the degree of impaired visual selective attention. These findings demonstrate that positive states, by loosening the reins on inhibitory control, result in a fundamental change in the breadth of attentional allocation to both external visual and internal conceptual space.

Adult↗
PubMed2003

Dissociated neural representations of intensity and valence in human olfaction.

Affective experience has been described in terms of two primary dimensions: intensity and valence. In the human brain, it is intrinsically difficult to dissociate the neural coding of these affective dimensions for visual and auditory stimuli, but such dissociation is more readily achieved in olfaction, where intensity and valence can be manipulated independently. Using event-related functional magnetic resonance imaging (fMRI), we found amygdala activation to be associated with intensity, and not valence, of odors. Activity in regions of orbitofrontal cortex, in contrast, were associated with valence independent of intensity. These findings show that distinct olfactory regions subserve the analysis of the degree and quality of olfactory stimulation, suggesting that the affective representations of intensity and valence draw upon dissociable neural substrates.

Adult↗
PubMed2003

Transient lupus anticoagulant: an unusual cause of bruising in children.

A child presented with excessive bruising and prolonged activated partial thromboplastin time. Mixing studies in plasma were positive for phospholipid dependence of the anticoagulant, confirming a diagnosis of lupus anticoagulant. Factor II level was reduced. Laboratory findings normalised after three months, with spontaneous resolution of bruising. This case demonstrates a transient antiphospholipid antibody syndrome as a rare presentation of bleeding diathesis in a previously healthy child, and should be considered in children with new onset bruising and prolonged activated partial thromboplastin time.

Antibodies, Antiphospholipid↗
PubMed2001

Lesions of the human amygdala impair enhanced perception of emotionally salient events.

Commensurate with the importance of rapidly and efficiently evaluating motivationally significant stimuli, humans are probably endowed with distinct faculties and maintain specialized neural structures to enhance their detection. Here we consider that a critical function of the human amygdala is to enhance the perception of stimuli that have emotional significance. Under conditions of limited attention for normal perceptual awareness-that is, the attentional blink-we show that healthy observers demonstrate robust benefits for the perception of verbal stimuli of aversive content compared with stimuli of neutral content. In contrast, a patient with bilateral amygdala damage has no enhanced perception for such aversive stimulus events. Examination of patients with either left or right amygdala resections shows that the enhanced perception of aversive words depends specifically on the left amygdala. All patients comprehend normally the affective meaning of the stimulus events, despite the lack of evidence for enhanced perceptual encoding of these events in patients with left amygdala lesions. Our results reveal a neural substrate for affective influences on perception, indicating that similar neural mechanisms may underlie the affective modulation of both recollective and perceptual experience.

Adult↗
PubMed2001

International study in premedical education.

This study surveyed medical school admission deans about the desirability of international study. Most agreed that an international study program in the premedical years was beneficial, but most were neutral concerning science courses taken in international programs.

Attitude of Health Personnel↗
PubMed2001

Effects of phonological length on the attentional blink for words.

The authors tested whether the attentional blink (AB), a deficit in the ability to report a second target appearing within half a second of a first target, may reflect limitations for consolidating visual stimuli into working memory and awareness. Previous research has shown that people are severely limited in the rate that they can identify and report visual events presented in rapid succession. Word length was examined, a variable known to affect verbal working memory. Experiment 1 showed that the AB was modulated by the phonological length of the first target. Phonologically longer pseudowords triggered larger blink deficits. Experiment 2 also demonstrated the word-length effect on the AB using real-world stimuli, anagrams, that controlled for low-level visual differences between conditions. These data support proposals that the AB reflects a difficulty in consolidating information into working memory.

Attention↗
PubMed2000

Contribution of the anteromedial temporal lobes to the evaluation of facial emotion.

Amygdala damage can result in impairments in evaluating facial expressions largely specific to fear. In contrast, right-hemisphere cortical lesions result in a more global deficit in facial emotion evaluation. This study addressed these 2 contrasting findings by investigating amygdala and adjacent cortical contributions to the evaluation of facial emotion in 12 patients with right and 11 patients with left unilateral anteromedial temporal lobectomy (RTL and LTL, respectively) and 23 normal controls. RTL but not LTL patients revealed impaired intensity ratings that included but were not exclusive to fear, with the most severe deficits confined to expressions related to affective states of withdrawal-avoidance. This suggests that affective hemispheric specializations in cortical function may extend to subcortical limbic regions. In addition, the right amygdala and adjacent cortex may be part of a neural circuit representing facial expressions of withdrawal.

Adult↗
PubMed2000

Expression without recognition: contributions of the human amygdala to emotional communication.

A growing body of evidence from humans and other animals suggests the amygdala may be a critical neural substrate for emotional processing. In particular, recent studies have shown that damage to the human amygdala impairs the normal appraisal of social signals of emotion, primarily those of fear. However, effective social communication depends on both the ability to receive (emotional appraisal) and the ability to send (emotional expression) signals of emotional state. Although the role of the amygdala in the appraisal of emotion is well established, its importance for the production of emotional expressions is unknown. We report a case study of a patient with bilateral amygdaloid damage who, despite a severe deficit in interpreting facial expressions of emotion including fear, exhibits an intact ability to express this and other basic emotions. This dissociation suggests that a single neural module does not support all aspects of the social communication of emotional state.

Amygdala↗
PubMed1998

Intact recognition of vocal expressions of fear following bilateral lesions of the human amygdala.

A recent case study found that bilateral damage to the amygdala impairs the normal appraisal of vocal expressions of fear. However, the single source of evidence for this auditory emotion-processing impairment is from a patient with extra-amygdaloid damage that may include the basal ganglia, which have been shown to be important for prosody evaluation. In this study we provide evidence of preserved evaluation of vocal expressions of fear in a female patient (S.P.) with bilateral damage to the amygdala but with intact basal ganglia. This same patient has previously been shown to be impaired in the evaluation of facial expressions, including fear. These results indicate that the analysis of nonverbal signals of fear from different input channels are dissociable, being at least partially dependent on different brain structures. We suggest that the amygdala, in conjunction with the basal ganglia, may support the normal appraisal of auditory signals of danger.

Acoustic Stimulation↗
PubMed1996

Changes in cortical activity during mental rotation. A mapping study using functional MRI.

Mental imagery is an important cognitive method for problem solving, and the mental rotation of complex objects, as originally described by Shepard and Metzler (1971), is among the best studied mental imagery tasks. Functional MRI was used to observe focal changes in blood flow in the brains of 10 healthy volunteers performing a mental rotation task. On each trial, subjects viewed a pair of perspective drawings of three-dimensional shapes, mentally rotated one into congruence with the other, and then determined whether the two forms were identical or mirror-images. The control task, which we have called the 'comparison' condition, was identical except that both members of each pair appeared at the same orientation, and hence the same encoding, comparison and decision processes were used but mental rotation was not required. These tasks were interleaved with a baseline 'fixation' condition, in which the subjects viewed a crosshair. Technically adequate studies were obtained in eight of the 10 subjects. Areas of increased signal were identified according to sulcal landmarks and are described in terms of the Brodmann's area (BA) definitions that correspond according to the atlas of Talaraich and Tournoux. When the rotation task was contrasted with the comparison condition, all subjects showed consistent foci of activation in BAs 7a and 7b (sometimes spreading to BA 40): 88% had increased signal in middle frontal gyrus (BA 8) and 75% showed extrastriate activation, including particularly BAs 39 and 19, in a position consistent with area V5/human MT as localized by functional and histological assays. In more than half of the subjects, hand somatosensory cortex (3-1-2) was engaged, and in 50% of subjects there was elevated signal in BA 18. In frontal cortex, activation was above threshold in half the subjects in BAs 9 and/or 46 (dorsolateral prefrontal cortex). Some (four out of eight) subjects also showed signal increases in BAs 44 and/or 46. Premotor cortex (BA 6) was active in half of the subjects during the rotation task. There was little evidence for lateralization of the cortical activity or of engagement of motor cortex. These data are consistent with the hypothesis that mental rotation engages cortical areas involved in tracking moving objects and encoding spatial relations, as well as the more general understanding that mental imagery engages the same, or similar, neural imagery as direct perception.

Adult↗
PubMed1994

Identifying objects seen from different viewpoints. A PET investigation.

Positron emission tomography scans were acquired when subjects performed three tasks, each in a separate block of trials. They decided whether words named pictures of objects viewed from a canonical perspective, decided whether words named pictures of objects viewed from a non-canonical (unusual) perspective or saw random patterns of lines and pressed a pedal when they heard the word (this was a baseline condition). The dorsolateral prefrontal region was activated when subjects identified objects seen from non-canonical perspectives, as expected if the frontal lobes are involved in top-down perceptual processing. In addition, several areas in the occipital, temporal and parietal lobes were selectively activated when subjects identified objects seen from non-canonical perspectives, as specifically predicted by a recent theory. Overall, the pattern of results supported the view that the human brain identifies objects by using a system of areas similar to that suggested by studies of other primates.

Adolescent↗
PubMed1984

Percutaneous absorption of iodochlorhydroxyquin in humans.

Iodochlorhydroxyquin (I) is used in the treatment of diaper rash and other skin disorders, and is presumed to undergo little or no percutaneous absorption. The absorption of (I) from a 3% cream was studied in 5 normal male subjects after a single application of the cream for 12 h. Plasma levels of the drug were followed for 24 h after initial application while urinary excretion was measured for 54 h. (I) was extracted from plasma and urine and assayed by high-performance liquid chromatography. The drug in the range of 0.37-0.56 micrograms/ml was detected in plasma 2 h after application and persisted throughout the treatment period. The mean excretion rate after 12 h of application was 58.4 micrograms/h and the excretion rate was 8.8 micrograms/h at 42 h posttreatment. The elimination rate constant was calculated to be 0.15 h-1. Approximately 40% of the drug was absorbed over the 12-h application period. From the above results it is apparent that significant percutaneous absorption of (I) occurs.

Absorption↗
PubMed1983

Stability of vitamin and mineral concentrations of a low-birth-weight infant formula during continuous enteral feeding.

The stability of several vitamins and minerals of a new formula for premature infants, Similac Special Care, was examined following passage through a simulated continuous infusion apparatus designed to duplicate that used for continuous enteral feeding in infants. The concentrations of calcium, iron, zinc, copper, magnesium, vitamin A, vitamin C, and vitamin E were measured before and after infusion at rates appropriate for delivering 120 calories/kg to infants weighing 733 and 1,000 g. Following passage through this apparatus, significant reductions were noted for calcium (44-54%), iron (23-34%), and zinc (18-32%). Concentrations of copper, magnesium, and vitamins A, C, and E remained stable. When another formula commonly used for premature infants, Similac 24LBW, was subjected to similar analysis, the concentrations of all vitamins and minerals studied remained stable. Our study demonstrates that infants fed Similac Special Care by continuous infusion may not receive the quantity of calcium, iron, and zinc implied by the product label.

Calcium↗