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D W Zaidel

Publications and source records attributed to D W Zaidel.

At least 19 recordsLinked to original sources
PubMed2005

The face, beauty, and symmetry: perceiving asymmetry in beautiful faces.

The relationship between bilateral facial symmetry and beauty remains to be clarified. Here, straight head-on photographs of "beautiful" faces from the collections of professional modeling agencies were selected. First, beauty ratings were obtained for these faces. Then, the authors created symmetrical left-left and right-right composites of the beautiful faces and asked a new group of subjects to choose the most attractive pair member. "Same" responses were allowed. No difference between the left-left and right-right composites was revealed but significant differences were obtained between "same" and the left-left or right-right. These results show that subjects detected asymmetry in beauty and suggest that very beautiful faces can be functionally asymmetrical.

Adolescent↗
PubMed2003

Hemifield memory for attractiveness.

In order to determine whether or not facial attractiveness plays a role in hemispheric facial memory, 35 right-handed participants first assigned attractiveness ratings to faces and then performed a recognition test on those faces in the left visual half-field (LVF) and right visual half-field (RVF). We found significant interactions between the experimental factors and visual half-field. There were significant differences in the extreme ends of the rating scale, that is, the very unattractive versus the very attractive faces: Female participants remembered very attractive faces of both women and men, with memory being superior in the RVF than in the LVF. In contrast, the male participants remembered very unattractive faces of both women and men; RVF memory was better than the LVF for women faces while for men faces memory was superior in the LVF. The interactions with visual half-field suggest that hemispheric biases in remembering faces are influenced by degree of attractiveness.

Adult↗
PubMed2003

Relationship between facial asymmetry and judging trustworthiness in faces.

Nonverbal facial signals provide valuable information for successful social interactions. Previous findings showed left-right facial asymmetry in attractiveness, smiling, and health in faces, and here we investigated the asymmetrical status of trustworthiness. Pairs of left-left and right-right faces from 38 photographs were viewed by participants who judged which member of the pair looked the most trustworthy. The results were compared to attractiveness and smiling judgements (Zaidel, Chen, & German, 1995). We found that trustworthiness was more related to attractiveness than to smiling in the women's faces, but no significant asymmetry for trustworthiness was found; in the men's faces, trustworthiness was neither related to attractiveness nor to smiling, nor was there a significant asymmetry. Taken together, trustworthiness as a facial display is complex; even when it appears to confirm the "halo effect", its expression is not strongly left-right asymmetrical in contrast to attractiveness or smiling.

Journal Article↗
PubMed2001

Functional asymmetry in the human face: perception of health in the left and right sides of the face.

The expression of health on the human face, like beauty or emotions, is an important biological display. Previous findings of left-right functional asymmetry in facial attractiveness and the linkage of attractiveness and health in evolutionary biology notions have prompted the present study. A total of 38 pairs of left-left and right-right facial composites were viewed by 24 subjects on a computer screen, and the task was to decide which member of the pair looked healthier or there was no difference. The results revealed a significant interaction between face side and sex of face. Right-right composites of women's faces were judged significantly healthier than left-left, whereas in men's faces, no significant left-right difference emerged. As these results parallel previous findings of attractiveness in the identical set of faces, we propose that evolutionary biology notions linking the appearance of health and of attractiveness apply to the human face as well.

Journal Article↗
PubMed1999

Quantitative morphology of human hippocampus early neuron development.

Previous findings in adults revealed significant hemispheric asymmetry in the size of neuronal somata in hippocampal subfield CA2 (the resistant sector) with no age-related changes. A paucity of quantitative data on the developmental status of these protected neurons has led to the investigation of their morphology in comparison to neurons in adjacent subfield CA3, bilaterally. Bilateral coronal sections from postmortem hippocampus, 24 to 76 weeks postmenstrual age (gestational age plus postnatal age), were studied. The neurons were digitized and measured on a computer. Soma size correlated positively and significantly with age in CA2 and CA3, bilaterally. CA2 somata were significantly larger (left, 34%; right, 32%) than adjacent CA3 somata. Variability in soma form or size increased appreciably with age, in both subfields, bilaterally, while variability in soma orientation was weakly correlated with brain growth. The results suggest that in early development there are similarities in hemispheric growth patterns in CA2 and CA3. Large CA2 soma size implies axonal connectivity to distantly located targets very early in development. The results have functional implications, including memory, to brain development.

Adult↗
PubMed1999

Regional differentiation of neuron morphology in human left and right hippocampus: comparing normal to schizophrenia.

Regional differentiation based on size, form, and orientation angle of the soma of individual neurons in human post-mortem hippocampus was determined through correlations between pairs of hippocampal subfields in each side separately. The neurons were previously measured on a computer. In the normal cases, a left-right asymmetrical pattern of regional differentiation based on soma size emerged, while for form and orientation angle, the patterns appeared symmetrical. In schizophrenia, regional soma size, form, and orientation variability were expressed largely symmetrically. Regional correlations based on neuronal density revealed an asymmetrical hemispheric pattern in the normal cases versus a nearly symmetrical pattern in schizophrenia. Taken together, the inter-regional correlations favor a hippocampal landscape that deviates in each side from connectivity based on the canonical trisynaptic hippocampal circuitry. It is proposed that during morphogenesis, rudimentary inter-regional networks are formed through specific interactions between regional neurons; these networks are present in the adult hippocampus and may be vulnerable in brain diseases.

Adult↗
PubMed1998

Observations on the relationship between verbal explicit and implicit memory and density of neurons in the hippocampus.

The relationship between neuronal density and verbal memory in left and right hippocampal subfields was investigated in patients who underwent surgery for alleviation of temporal lobe epilepsy. The surgery consisted of unilateral partial removal of the hippocampus along with the anterior temporal lobe and amygdala. Study 1 looked at post-surgical explicit vs implicit verbal memory for lists of words while Study 2 looked at pre- and post-surgical explicit memory for word pairs. Left subfield CA1 appeared to be the most consistently involved in explicit and implicit memory. The results of the two studies confirm presence of hemispheric asymmetry in verbal memory. The notion that hippocampal control of memory is most apparent in post-surgical performance is discussed.

Adult↗
PubMed1997

Art and science.

Explore the source record for details and available documents.

Brain↗
PubMed1997

Brain asymmetry and facial attractiveness: facial beauty is not simply in the eye of the beholder.

We recently reported finding asymmetry in the appearance of beauty on the face [Zaidel et al., Neuropsychologia, Vol. 33, pp. 649-655, 1995]. Here, we investigated whether facial beauty is a stable characteristic (on the owner's very face) or is in the perceptual space of the observer. We call the question 'the owner vs observer hypothesis'. We compared identity judgements and attractiveness ratings of observers. Subjects viewed left-left and right-right composites of faces and decided which most resembled the normal face (Experiment 1). Identity judgements (resemblance) are known to be associated with perceptual factors in the observer. Another group viewed the same normal faces and rated them on attractiveness (Experiment 2). In each experiment, there were two separate viewing conditions, original and reversed (mirror-image). Lateral reversal did affect the results of Experiment 1 (confirming previous findings [Bennett et al., Neuropsychologia, Vol. 25, pp. 681-687, 1987; Gilbert and Bakan, Journal of Anatomy, Vol. 183, pp. 593-600, 1993]) but did not affect the results of Experiment 2. The fact that lateral reversal did not affect the results of Experiment 2 suggests that facial attractiveness is more dependent on physiognomy (of the owner) and less dependent on an asymmetrical perceptual process (in the observer) than is facial identity. The results are discussed in the context of beauty's biological significance and facial processing in the brain.

Adolescent↗
PubMed1997

The hippocampus in schizophrenia: lateralized increase in neuronal density and altered cytoarchitectural asymmetry.

BACKGROUND: The histological basis of schizophrenia is unknown, but it appears to affect the hippocampal and neocortical cytoarchitecture. Some cytoarchitectural parameters normally differ between the two cerebral hemispheres. Moreover, schizophrenia is associated with altered structural cerebral asymmetry. However, few cytoarchitectural studies of schizophrenia have taken the question of asymmetry fully into account. METHODS: We performed a morphometric post mortem study of neuronal density in sections from the left and right hippocampus (dentate gyrus, CA4, CA3, CA1 and subiculum) of 22 schizophrenics and 18 normal subjects. We also determined the correlations of neuronal density between pairs of subfields as an index of their inter-relationship; a previous study had found correlations in the left but not the right hippocampus of normal subjects. RESULTS: There were three differences in the schizophrenics compared to the controls. (1) neuronal density was increased in right CA3 (by 25%) and right CA1 (by 22%); (2) neuronal density correlated strongly between homologous left and right subfields (i.e. inter-hippocampally) for CA4, CA3, CA1 and subiculum, in normals this occurs only for dentate gyrus and CA4; and (3) intrahippocampal correlations of neuronal density between pairs of subfields were similar in both hippocampi of the schizophrenia cases, unlike their asymmetrical distribution in controls. CONCLUSIONS: The alterations may be part of the histological substrate of schizophrenia. The nature of the findings is consistent with a neurodevelopmental origin, and with a disease process that affects cerebral asymmetry and leaves its imprint upon the hippocampal cytoarchitecture.

Aged↗
PubMed1997

Size, shape, and orientation of neurons in the left and right hippocampus: investigation of normal asymmetries and alterations in schizophrenia.

OBJECTIVE: Schizophrenia may involve the two cerebral hemispheres differentially. This study was conducted to determine whether left and right hippocampal neuronal size, shape, and orientation are normally asymmetrical or asymmetrically affected in schizophrenia. METHOD: The authors examined postmortem tissue from the left and right hippocampus of 17 normal individuals and 14 individuals with schizophrenia. They measured the size, shape, and variability in orientation of pyramidal neurons in hippocampal subfields CA1-CA4 and the subiculum in computer images of 10-micron coronal sections stained with cresyl violet. RESULTS: Both neuronal size and shape showed significant effects of diagnosis and a three-way interaction between diagnosis, hemisphere, and subfield. Neurons of the schizophrenic subjects were smaller than those of the normal subjects in the left CA1, left CA2, and right CA3 subfields; their shape differed from that of the normal subjects in the left CA1, left subiculum, and right CA3 subfields. There were no group differences in variability of neuronal orientation, but neurons in the CA3 genu in the schizophrenic subjects were less variable on the right than on the left. In the normal subjects, except for larger neurons in the left than in the right CA2 subfield and some left-right differences in variability of neuronal orientation, no statistically significant asymmetries were observed. CONCLUSIONS: The data confirm that hippocampal neuronal size is decreased in schizophrenia and reveal that the shape of neurons is altered, supporting the view that hippocampal cytoarchitectural abnormalities may be part of the cerebral substrate of schizophrenia. They also provide further evidence that the abnormalities are localized and lateralized.

Adult↗
PubMed1995

The interpretation of sentence ambiguity in patients with unilateral focal brain surgery.

Interpretations of ambiguous sentences were studied in patients with unilateral anterior temporal lobectomy or selective amygdalo-hippocampectomy. The sentences represented lexical and syntactic ambiguities. In both left- and right-sided groups, regardless of type of surgery, total mean score on the test was below normal. Left-sided cases, regardless of type of surgery, provided significantly fewer alternative interpretations than right-sided cases. The results suggest greater left than right hemisphere specialization in both lexical and syntactic processing, but also suggest right hemisphere involvement in resolution of lexical ambiguity.

Adult↗
PubMed1995

She is not a beauty even when she smiles: possible evolutionary basis for a relationship between facial attractiveness and hemispheric specialization.

The asymmetrical status of facial beauty has rarely been investigated. We studied positive facial characteristics, attractiveness and smiling, through the use of left-left and right-right composites of unfamiliar faces of women and men with natural expressions. Results showed that women's right-right composites were judged significantly more attractive than left-left composites while there was no left-right difference in men's composites (Experiment 1). On the other hand, left-left composites were judged to have more pronounced smiling expressions than right-right composites in both women's and men's faces (Experiment 2). The results confirm previous findings for leftward facial expressiveness and show for the first time asymmetry in facial attractiveness and a difference in its manifestation in women's and men's faces. The findings have biological implications for the relationship between the appearance of the sides of the face and hemispheric specialization. The organization of beauty in the human face may have been shaped by evolutionary pressures on facial asymmetries, especially as they pertain to mate selection.

Adolescent↗
PubMed1995

Alien hand syndrome: interhemispheric motor disconnection due to a lesion in the midbody of the corpus callosum.

The neuroanatomic substrate of the alien hand syndrome has remained controversial due to the noncircumscribed nature of cerebral injuries present in most cases. There have been few cases studied in which damage was restricted to portions of the body of the callosum, and most of those involved surgical callosotomy for tumors or epilepsy. We report the case of a woman with a transient alien hand syndrome caused by a stroke limited to the middle and posterior portions of the body of the corpus callosum. This case provides supportive evidence for damage to the midbody of the corpus callosum as the anatomic basis of nondominant alien hand syndrome and conforms to a model of interhemispheric motor disconnection as the essential component of this unusual behavioral syndrome. This disconnection can occur with injuries involving interhemispheric premotor and motor fibers traveling in the midportion of the callosum in individuals with left hemisphere dominance for motor activities.

Aged↗
PubMed1995

Hemispheric semantics: effects on pictorial organization of patients with unilateral brain damage.

Memory for incongruous scenes (violating "knowledge-of-the-world") versus unorganized (jumbled) arrays was tested in war veterans with unilateral penetrating missile wounds of the brain in order to assess hemispheric differences in semantic schemas in long-term memory. Left brain-damaged (LBD) patients were selectively impaired in remembering unorganized scenes compared to right brain-damage (RBD) patients. There was no significant LBD-RBD difference in remembering incongruous scenes. The results confirm the presence of hemispheric asymmetry for semantic schemas in long-term memory, even in pictorial material. However, some features in the organization of semantic schemas are common to both hemispheres and suggests presence of similar knowledge systems. The asymmetry is discussed in terms of intact left hemisphere specialization for assigning meaning to a visual scene when obvious meaning appears to be absent.

Aged↗