Species-specific calls evoke asymmetric activity in the monkey's temporal poles

It has often been proposed that the vocal calls of monkeys are precursors of human speech, in part because they provide critical information to other members of the species who rely on them for survival and social interactions. Both behavioural and lesion studies suggest that monkeys, like humans, use the auditory system of the left hemisphere preferentially to process vocalizations. To investigate the pattern of neural activity that might underlie this particular form of functional asymmetry in monkeys, we measured local cerebral metabolic activity while the animals listened passively to species-specific calls compared with a variety of other classes of sound. Within the superior temporal gyrus, significantly greater metabolic activity occurred on the left side than on the right, only in the region of the temporal pole and only in response to monkey calls. This functional asymmetry was absent when these regions were separated by forebrain commissurotomy, suggesting that the perception of vocalizations elicits concurrent interhemispheric interactions that focus the auditory processing within a specialized area of one hemisphere.     

Localization of a human system for sustained attention by positron emission tomography

Positron emission tomographic (PET) studies of human attention have begun to dissect isolable components of this complex higher brain function, including a midline attentional system in a region of the anterior cingulate cortex. The right hemisphere may play a special part in human attention; neglect, an important phenomenon associated with damage to attentional systems, is more severe, extensive and long-lasting after lesions to the right hemisphere. Here we use PET measurements of brain blood flow in healthy subjects to identify changes in regional brain activity during simple visual and somatosensory tasks of sustained attention or vigilance. We find localized increases in blood flow in the prefrontal and superior parietal cortex primarily in the right hemisphere, regardless of the modality or laterality of sensory input. The anterior cingulate was not activated during either task. These data localize the vigilance aspects of normal human attention to sensory stimuli, thereby clarifying the biology underlying asymmetries of attention to such stimuli that have been reported in clinical lesions.     

Left hemisphere advantage in the mouse brain for recognizing ultrasonic communication calls

In humans, sound perceived as speech is processed preferentially by the right ear and the left hemisphere of the brain. Among animals, such an advantage of one hemisphere (lateralization) in processing communication sound from other members of the species has so far been demonstrated only in macaque monkeys. I report here that in the house mouse, which has a very much less elaborate forebrain than man or macaque monkey, the ultrasonic calls that are emitted by young mice to evoke maternal caring behavior are preferentially recognized by the left hemisphere. In females with no experience of pups, which have been trained to respond to the same ultrasonic calls by conditioning, no advantage for one hemisphere is detected. The results suggest that lateralization of this function evolved early in mammals and emphasize that an innate predisposition for perceiving communication sounds is connected with a left-hemisphere advantage in processing them. This experimental system is a readily-available animal model for studying lateralized auditory brain functions.     

Sign language aphasia during left-hemisphere Amytal injection

Although it has been established that the left cerebral hemisphere subserves spoken language, the nature of brain organization for sign language remains relatively unexplored. The issue is especially important because sign language displays the complex linguistic structure of spoken languages, but conveys it through manipulation of visuo-spatial relations, thereby exhibiting properties for which the hemispheres of hearing individuals show opposing specializations. We had the unique opportunity to study a hearing signer proficient in American sign language (ASL), during the left intracarotid injection of a barbiturate (the Wada test), and before and after a right temporal lobectomy. The subject was a strong right-hander. Neuropsychological and anatomical asymmetries suggested left cerebral dominance for auditory-based language. Emission tomography revealed lateralized activity of left Broca's and Wernicke's regions for spoken language. The Wada test, during which all left language areas were rendered inoperative, caused a marked aphasia in both English and ASL. After partial ablation of the right temporal lobe, the abilities to sign and understand signing were unchanged. These data add further support to the notion that anatomical structures of the left cerebral hemisphere subserve language in a visuo-spatial as well as an auditory mode.     

Localization of the brain calculation function area with MRI

The aim of this study is to define the anatomical localization of corresponding brain function area during calculating. The activating modes in brain during continuous silent calculating subtraction and repeated silent reading multiplication table were compared and investigated. Fourteen volunteers of right-handedness were enrolled in this experiment. The quite difference of reaction modes in brain area during the two modes of calculation reveal that there are different processing pathways in brain during these two operating actions. During continuous silent calculating, the function area is localized on the posterior portion of superior and middle gyrus of frontal lobe and the lobule of posterior parietal lobe (P < 0.01,T = 5.41). It demonstrates that these function areas play an important role in the performance of calculation and working memory. Whereas the activating of visual cortex shows that even in mental arithmetic processing the brain action is having the aid of vision and visual space association.     

Left neglect for near but not far space in man

It has been suggested that, among the many visual areas of the human brain, there might be one set of spatial maps specialized for 'near' (peripersonal) and another for 'far' (extrapersonal) space. A distinction between 'grasping distance' and 'walking distance', or between a 'reaching field' and a pointing or throwing field has commonly been made. Evidence for such a division has been found in monkeys. Unilateral ablation of the frontal eye field (area 8) produces a more prominent inattention (or 'neglect') for objects in contralesional far space than in near space; by contrast, unilateral ablation of frontal area 6, which receives direct projections from area 7b (the rostral part of the inferior parietal lobules) results in inattention to visual stimuli limited to contralesional near space. Despite predictions that comparable dissociations should be found in man, there has been no convincing evidence. We report here such evidence in a patient with a unilateral right hemisphere stroke. Within peripersonal space, he showed severe left visuo-spatial neglect on conventional tests, including the highly sensitive task of line bisection. When line bisection was performed in extrapersonal space, neglect was abolished or attenuated.     

Neural correlates of implied motion

Current views of the visual system assume that the primate brain analyses form and motion along largely independent pathways; they provide no insight into why form is sometimes interpreted as motion. In a series of psychophysical and electrophysiological experiments in humans and macaques, here we show that some form information is processed in the prototypical motion areas of the superior temporal sulcus (STS). First, we show that STS cells respond to dynamic Glass patterns, which contain no coherent motion but suggest a path of motion. Second, we show that when motion signals conflict with form signals suggesting a different path of motion, both humans and monkeys perceive motion in a compromised direction. This compromise also has a correlate in the responses of STS cells, which alter their direction preferences in the presence of conflicting implied motion information. We conclude that cells in the prototypical motion areas in the dorsal visual cortex process form that implies motion. Estimating motion by combining motion cues with form cues may be a strategy to deal with the complexities of motion perception in our natural environment.     

Neuronal correlate of visual associative long-term memory in the primate temporal cortex

In human long-term memory, ideas and concepts become associated in the learning process. No neuronal correlate for this cognitive function has so far been described, except that memory traces are thought to be localized in the cerebral cortex; the temporal lobe has been assigned as the site for visual experience because electric stimulation of this area results in imagery recall and lesions produce deficits in visual recognition of objects. We previously reported that in the anterior ventral temporal cortex of monkeys, individual neurons have a sustained activity that is highly selective for a few of the 100 coloured fractal patterns used in a visual working-memory task. Here I report the development of this selectivity through repeated trials involving the working memory. The few patterns for which a neuron was conjointly selective were frequently related to each other through stimulus-stimulus association imposed during training. The results indicate that the selectivity acquired by these cells represents a neuronal correlate of the associative long-term memory of pictures.     

Robust habit learning in the absence of awareness and independent of the medial temporal lobe

Habit memory is thought to involve slowly acquired associations between stimuli and responses and to depend on the basal ganglia. Habit memory has been well studied in experimental animals but is poorly understood in humans because of their strong tendency to acquire information as conscious (declarative) knowledge. Here we show that humans have a robust capacity for gradual trial-and-error learning that operates outside awareness for what is learned and independently of the medial temporal lobe. We tested two patients with large medial temporal lobe lesions and no capacity for declarative memory. Both patients gradually acquired a standard eight-pair object discrimination task over many weeks but at the start of each session could not describe the task, the instructions or the objects. The acquired knowledge was rigidly organized, and performance collapsed when the task format was altered.     

睡眠剥夺影响大脑功能区状态的非线性评价

采用近似熵研究睡眠剥夺（sleep deprivation，SD）对脑认知功能的影响，评价SD引起的大脑功能区状态的非线性变化．12名受试者在正常睡眠和一夜SD之后分别接受视觉注意力测试，记录自发脑电和诱发脑电，采用二维插值构建19导脑电近似熵脑信息图（brain information map，BIM）．结果表明，在SD状态下，自发脑电的近似熵在全脑范围内有不同程度的下降，额叶处大脑偏侧性发生变化，复杂度的中心从左脑转移到右脑；前额叶处诱发脑电近似熵值降低，而顶叶和颞叶处则升高．脑电近似熵可以作为指标来评价SD对脑认知功能的负向影响，BIM的变化趋势与从生理学及影像学角度的分析相吻合，与线性方法的研究结论一致，在一定程度上可以反映大脑功能状态，提供一条评价脑功能区状态变化趋势的思路．     

Attention modulates synchronized neuronal firing in primate somatosensory cortex

A potentially powerful information processing strategy in the brain is to take advantage of the temporal structure of neuronal spike trains. An increase in synchrony within the neural representation of an object or location increases the efficacy of that neural representation at the next synaptic stage in the brain; thus, increasing synchrony is a candidate for the neural correlate of attentional selection. We investigated the synchronous firing of pairs of neurons in the secondary somatosensory cortex (SII) of three monkeys trained to switch attention between a visual task and a tactile discrimination task. We found that most neuron pairs in SII cortex fired synchronously and, furthermore, that the degree of synchrony was affected by the monkey's attentional state. In the monkey performing the most difficult task, 35% of neuron pairs that fired synchronously changed their degree of synchrony when the monkey switched attention between the tactile and visual tasks. Synchrony increased in 80% and decreased in 20% of neuron pairs affected by attention.     

Global and fine information coded by single neurons in the temporal visual cortex.

When we see a person's face, we can easily recognize their species, individual identity and emotional state. How does the brain represent such complex information? A substantial number of neurons in the macaque temporal cortex respond to faces. However, the neuronal mechanisms underlying the processing of complex information are not yet clear. Here we recorded the activity of single neurons in the temporal cortex of macaque monkeys while presenting visual stimuli consisting of geometric shapes, and monkey and human faces with various expressions. Information theory was used to investigate how well the neuronal responses could categorize the stimuli. We found that single neurons conveyed two different scales of facial information in their firing patterns, starting at different latencies. Global information, categorizing stimuli as monkey faces, human faces or shapes, was conveyed in the earliest part of the responses. Fine information about identity or expression was conveyed later, beginning on average 51 ms after global information. We speculate that global information could be used as a 'header' to prepare destination areas for receiving more detailed information.     

Neurolinguistics: structural plasticity in the bilingual brain

Humans have a unique ability to learn more than one language--a skill that is thought to be mediated by functional (rather than structural) plastic changes in the brain. Here we show that learning a second language increases the density of grey matter in the left inferior parietal cortex and that the degree of structural reorganization in this region is modulated by the proficiency attained and the age at acquisition. This relation between grey-matter density and performance may represent a general principle of brain organization.     

Numerical representation for action in the parietal cortex of the monkey

The anterior part of the parietal association area in the cerebral cortex of primates has been implicated in the integration of somatosensory signals, which generate neural images of body parts and apposed objects and provide signals for sensorial guidance of movements. Here we show that this area is active in primates performing numerically based behavioural tasks. We required monkeys to select and perform movement A five times, switch to movement B for five repetitions, and return to movement A, in a cyclical fashion. Cellular activity in the superior parietal lobule reflected the number of self-movement executions. For the most part, the number-selective activity was also specific for the type of movement. This type of numerical representation of self-action was seen less often in the inferior parietal lobule, and rarely in the primary somatosensory cortex. Such activity in the superior parietal lobule is useful for processing numerical information, which is necessary to provide a foundation for the forthcoming motor selection.     

Neural substrates of global perception are modulated by local element grouping

THE GLOBAL PERCEPTION OF HIERARCHICALLY ORGANIZED STIMULI CAN BE DIFFERENT FROM THE LOCAL PERCEPTION IN THAT GLOBAL RESPONSES ARE FASTER THAN LOCAL RESPONSES AND THE GLOBAL-TO-LOCAL INTERFERENCE IS STRONGER THAN THE RE-VERSE[1]. THIS GLOBAL PRECEDENCE EFF…     

Guarding the gateway to cortex with attention in visual thalamus

The massive visual input from the eye to the brain requires selective processing of some visual information at the expense of other information, a process referred to as visual attention. Increases in the responses of visual neurons with attention have been extensively studied along the visual processing streams in monkey cerebral cortex, from primary visual areas to parietal and frontal cortex. Here we show, by recording neurons in attending macaque monkeys (Macaca mulatta), that attention modulates visual signals before they even reach cortex by increasing responses of both magnocellular and parvocellular neurons in the first relay between retina and cortex, the lateral geniculate nucleus (LGN). At the same time, attention decreases neuronal responses in the adjacent thalamic reticular nucleus (TRN). Crick argued for such modulation of the LGN by observing that it is inhibited by the TRN, and suggested that "if the thalamus is the gateway to the cortex, the reticular complex might be described as the guardian of the gateway", a reciprocal relationship we now show to be more than just hypothesis. The reciprocal modulation in LGN and TRN appears only during the initial visual response, but the modulation of LGN reappears later in the response, suggesting separate early and late sources of attentional modulation in LGN.     

Functional brain laterality for sequential movements： Impact of transient practice

The impact of learning on brain functional laterality has not been systematically investigated. We employed an event-related functional magnetic resonance imaging combined with a delayed sequential movement task to investigate brain activation pattern and laterality during a transient practice in 12 subjects. Both hemispheres, involving motor areas and posterior parietal cortex, were engaged during motor preparation and execution, with larger activation volume in the left hemisphere than in the right. Activation volume in these regions significantly decreased after a transient practice, with more reduction in the right hemisphere resulting increase in left lateralization. The theoretical implications of these findings are discussed in relation to the physiological significance of brain functional laterality.     

STROOP测验在正常人和脑损伤患者应用结果的特征分析

目的 通过正常人群了解Stroop测验的结果是否存在性别、年龄和学历上存在差异;通过单纯额叶、颞叶和顶叶卒中的病人了解是Stroop测验可能的神经功能区域.方法 研究采用中文版Stroop测验和简易智能量表,数据处理采用SPSS13.0软件据包进行分析和处理.结果 正常人Stroop测验结果与性别无关（P〉0.05）,与年龄有关（P 〈0.05）,与教育程度有关（P 〈0.05）.卒中的病人按照左右半球损害分组无差异（P 〉0.05）,按照损害额叶、颞叶和顶叶分组无差异（P 〈0.05）.结论 正常人群Stroop测验结果与年龄和学历有关,无性别的差异.Stroop测验结果没有左右半球的差异,但是存在功能分区的差异,在额叶、颞叶和顶叶中,额叶的影响可能更大.     

Neural encoding of individual words and faces by the human hippocampus and amygdala

Patients with lesions in the medial temporal lobe (MTL) of the brain, which includes the hippocampus, amygdala and parahippocampal gyrus, are severely impaired in their ability to remember and recognize words or faces which they saw only a short time ago. These lesions also prevent the effect of word repetition on cortical event-related potentials that are associated with these tasks. We have been able to study the response of individual neurons in the human medial temporal lobe to such delayed recognition tasks in epileptic patients undergoing neurosurgery. We found that some MTL neurons preferentially fired on sight of one particular word from a set of ten words used in a memory task, and others fired in response to one particular face. This stimulus-specific firing was maximal during the time that the neocortical event potentials are most sensitive to stimulus repetition, suggesting that the MTL contributes specific information to the cortex during the retrieval of recent memories.     

A back-propagation programmed network that simulates response properties of a subset of posterior parietal neurons

Neurons in area 7a of the posterior parietal cortex of monkeys respond to both the retinal location of a visual stimulus and the position of the eyes and by combining these signals represent the spatial location of external objects. A neural network model, programmed using back-propagation learning, can decode this spatial information from area 7a neurons and accounts for their observed response properties.