巨猿、化石人和智人牙齿的波动不对称：人类进化中压力源变化的意义

波动不对称（FA）是压力的随机性引发双侧完美对称偏离的现象,这是个体无力免受发展中不利因素（如早期营养不良）侵害的一个标志。比较个体口腔两侧牙齿的大小是一种测量FA的方法。本研究汇集了10个物种共296名个体的牙齿测量结果,测量对象包括黑猩猩（学名Pan troglodytes）、猩猩（学名Pongo pygmaeus）、大猩猩（学名Gorilla gorilla）、智人（学名Homo sapiens）,以及许多化石人。分析发现,猩猩样本牙齿的FA水平要显著低于大猩猩、黑猩猩、直立人、尼安德特人和智人样本的FA水平。而与之相反的是,智人与尼安德特人样本的牙齿FA水平要显著高于其它任何一种巨猿样本的FA水平。该文提出了有关缓和的选择压力的解释     

Frontal brain electrical activity (EEG) and heart rate in response to affective infant-directed (ID) speech in 9-month-old infants

Many studies have shown that infants prefer infant-directed (ID) speech to adult-directed (AD) speech. ID speech functions to aid language learning, obtain and/or maintain an infant's attention, and create emotional communication between the infant and caregiver. We examined psychophysiological responses to ID speech that varied in affective content (i.e., love/comfort, surprise, fear) in a group of typically developing 9-month-old infants. Regional EEG and heart rate were collected continuously during stimulus presentation. We found the pattern of overall frontal EEG power was linearly related to affective intensity of the ID speech, such that EEG power was greatest in response to fear, than surprise than love/comfort; this linear pattern was specific to the frontal region. We also noted that heart rate decelerated to ID speech independent of affective content. As well, infants who were reported by their mothers as temperamentally distressed tended to exhibit greater relative right frontal EEG activity during baseline and in response to affective ID speech, consistent with previous work with visual stimuli and extending it to the auditory modality. Findings are discussed in terms of how increases in frontal EEG power in response to different affective intensity may reflect the cognitive aspects of emotional processing across sensory domains in infancy.     

Lateralized cognition: asymmetrical and complementary strategies of pigeons during discrimination of the "human concept"

This study was aimed at revealing which cognitive processes are lateralized in visual categorizations of "humans" by pigeons. To this end, pigeons were trained to categorize pictures of humans and then tested binocularly or monocularly (left or right eye) on the learned categorization and for transfer to novel exemplars (Experiment 1). Subsequent tests examined whether they relied on memorized features or on a conceptual strategy, using stimuli composed of new combinations of familiar and novel humans and backgrounds (Experiment 2), whether the hemispheres processed global or local information, using pictures with different levels of scrambling (Experiment 3), and whether they attended to configuration, using distorted human figures (Experiment 4). The results suggest that the left hemisphere employs a category strategy and concentrates on local features, while the right hemisphere uses an exemplar strategy and relies on configuration. These cognitive dichotomies of the cerebral hemispheres are largely shared by humans, suggesting that lateralized cognitive systems already defined the neural architecture of the common ancestor of birds and mammals.     

Neural responses to morphological, syntactic, and semantic properties of single words: an fMRI study

Dissociations in the recognition of specific classes of words have been documented in brain-injured populations. These include deficits in the recognition and production of morphologically complex words as well as impairments specific to particular syntactic classes such as verbs. However, functional imaging evidence for distinctions among the neural systems underlying these dissociations has been inconclusive. We explored the neural systems involved in processing different word classes in a functional Magnetic Resonance Imaging study, contrasting four groups of words co-varying morphological complexity (simple, monomorphemic words vs complex derived or inflected words) and syntactic class (verbs vs nouns/adjectives). Subtraction of word from letter string processing showed activation in left frontal and temporal lobe regions consistent with prior studies of visual word processing. No differences were observed for morphologically complex and simple words, despite adequate power to detect stimulus specific effects. A region of posterior left middle temporal gyrus showed significantly increased activation for verbs. Post hoc analyses showed that this elevated activation could also be related to semantic properties of the stimulus items (verbs have stronger action associations than nouns, and action association is correlated with activation). Results suggest that semantic as well as syntactic factors should be considered when assessing the neural systems involved in single word comprehension.     

Executive Function and the Frontal Lobes: A Meta-Analytic Review

Currently, there is debate among scholars regarding how to operationalize and measure executive functions. These functions generally are referred to as “supervisory” cognitive processes because they involve higher level organization and execution of complex thoughts and behavior. Although conceptualizations vary regarding what mental processes actually constitute the “executive function” construct, there has been a historical linkage of these “higher-level” processes with the frontal lobes. In fact, many investigators have used the term “frontal functions” synonymously with “executive functions” despite evidence that contradicts this synonymous usage. The current review provides a critical analysis of lesion and neuroimaging studies using three popular executive function measures (Wisconsin Card Sorting Test, Phonemic Verbal Fluency, and Stroop Color Word Interference Test) in order to examine the validity of the executive function construct in terms of its relation to activation and damage to the frontal lobes. Empirical lesion data are examined via meta-analysis procedures along with formula derivatives. Results reveal mixed evidence that does not support a one-to-one relationship between executive functions and frontal lobe activity. The paper concludes with a discussion of the implications of construing the validity of these neuropsychological tests in anatomical, rather than cognitive and behavioral, terms.     

Multiple landmarks, the encoding of environmental geometry and the spatial logics of a dual brain

A series of place learning experiments was carried out in young chicks (Gallus gallus) in order to investigate how the geometry of a landmark array and that of a walled enclosure compete when disoriented animals could rely on both of them to re-orient towards the centre of the enclosure. A square-shaped array (four wooden sticks) was placed in the middle of a square-shaped enclosure, the two structures being concentric. Chicks were trained to ground-scratch to search for food hidden in the centre of the enclosure (and the array). To check for effects of array degradation, one, two, three or all landmarks were removed during test trials. Chicks concentrated their searching activity in the central area of the enclosure, but their accuracy was inversely contingent on the number of landmarks removed; moreover, the landmarks still present within the enclosure appeared to influence the shape of the searching patterns. The reduction in the number of landmarks affected the searching strategy of chicks, suggesting that they had focussed mainly on local cues when landmarks were present within the enclosure. When all the landmarks were removed, chicks searched over a larger area, suggesting an absolute encoding of distances from the local cues and less reliance on the relationships provided by the geometry of the enclosure. Under conditions of monocular vision, chicks tended to rely on different strategies to localize the centre on the basis of the eye (and thus the hemisphere) in use, the left hemisphere attending to details of the environment and the right hemisphere attending to the global shape.This contribution is part of the special issue “Animal Logics” (Watanabe and Huber 2006).     

Time ordering in frontal lobe patients: a stochastic model approach

Frontal lobe patients reproduced a sequence of capital letters or abstract shapes. Immediate and delayed reproduction trials allowed the analysis of short- and long-term memory for time order by means of suitable Markov chain stochastic models. Patients were as proficient as healthy subjects on the immediate reproduction trial, thus showing spared encoding and short-term memory. They failed, instead, on the delayed trials with capital letters, but not with random shapes, suggesting that their long-term memory impairment did not depend on primary deficits for ordering, but on inability to benefit from the organisational strategies that improve the retention and retrieval in normal subjects.     

Perceptual asymmetries are preserved in memory for highly familiar faces of self and friend

We investigated the effect of familiarity on people's perception of facial likeness by asking participants to choose which of two mirror-symmetric chimeric images (made from the left or right half of a photograph of a face) looked more like an original image. In separate trials the participants made this judgment for their own face and for the face of a close friend; half of them matched to a true image of the original and half matched to a mirror image of the original. In the case of matching to a friend's face presented in the familiar orientation, over 80% of participants chose the left-left composite to be a better likeness to the original, whereas only 62% showed the same left-side bias when matching to a mirror image. The difference is significant, and the result contrasts markedly with a second experiment where participants who were unfamiliar with the faces showed comparable left-side biases when matching to true or mirror reversed images. The result suggests that perceptual asymmetries are retained in our long-term memory for highly familiar faces. While matching to images of self also showed an effect of familiarity, the data in this condition show less evidence of perceptual asymmetry and are discussed in relation to recent research on the representation of one's own face.     

Semantic representations of word meanings by the cerebral hemispheres

Two priming experiments investigated kind and strength of semantic knowledge underlying known, frontier, and unknown low frequency words. Results from Experiment 1 suggest that known words reflect categorical knowledge, but frontier and unknown words reflect thematic knowledge. Thematic knowledge for frontier words appears to be stronger than that for unknown words. Experiment 2 entailed visual half-field presentation of targets. All facilitory effects were restricted to the lvf/RH, and inhibitory effects to the rvf/LH. Experiment 1 findings were mirrored by the RH. Thematic knowledge appears to precede categorical knowledge for the RH, but the opposite may be true of the LH. Results are also discussed in terms of the RH role in meaning acquisition and metacontrol.     

Asymmetrical hemisphere activation enhances global–local processing

Decades of research focusing on the neurophysiological underpinnings related to global–local processing of hierarchical stimuli have associated global processing with the right hemisphere and local processing with the left hemisphere. The current experiment sought to expand this research by testing the causal contributions of hemisphere activation to global–local processing. To manipulate hemisphere activation, participants engaged in contralateral hand contractions. Then, EEG activity and attentional scope were measured. Right-hand contractions caused greater relative left-cortical activity than left-hand contractions. Participants were more narrowly focused after left-hemisphere activation than after right-hemisphere activation. Moreover, N1 amplitudes to local targets in the left hemisphere were larger after left-hemisphere activation than after right-hemisphere activation. Consistent with past research investigating hemispheric asymmetry and attentional scope, the current results suggest that manipulating left (right) hemisphere activity enhanced local (global) attentional processing.