Eye movements of monkey observers viewing vocalizing conspecifics

Primates, including humans, communicate using facial expressions, vocalizations and often a combination of the two modalities. For humans, such bimodal integration is best exemplified by speech-reading - humans readily use facial cues to enhance speech comprehension, particularly in noisy environments. Studies of the eye movement patterns of human speech-readers have revealed, unexpectedly, that they predominantly fixate on the eye region of the face as opposed to the mouth. Here, we tested the evolutionary basis for such a behavioral strategy by examining the eye movements of rhesus monkeys observers as they viewed vocalizing conspecifics. Under a variety of listening conditions, we found that rhesus monkeys predominantly focused on the eye region versus the mouth and that fixations on the mouth were tightly correlated with the onset of mouth movements. These eye movement patterns of rhesus monkeys are strikingly similar to those reported for humans observing the visual components of speech. The data therefore suggest that the sensorimotor strategies underlying bimodal speech perception may have a homologous counterpart in a closely related primate ancestor.     

Neural modeling and imaging of the cortical interactions underlying syllable production

This paper describes a neural model of speech acquisition and production that accounts for a wide range of acoustic, kinematic, and neuroimaging data concerning the control of speech movements. The model is a neural network whose components correspond to regions of the cerebral cortex and cerebellum, including premotor, motor, auditory, and somatosensory cortical areas. Computer simulations of the model verify its ability to account for compensation to lip and jaw perturbations during speech. Specific anatomical locations of the model's components are estimated, and these estimates are used to simulate fMRI experiments of simple syllable production.     

The cognitive significance of resonating neurons in the cerebral cortex

Most neural fibers of the cerebral cortex engage in electric signaling, but one particular fiber, the apical dendrite of the pyramidal neuron, specializes in electric resonating. This dendrite extends upward from somas of pyramidal neurons, the most numerous neurons of the cortex. The apical dendrite is embedded in a recurrent corticothalamic circuit that induces surges of electric current to move repeatedly down the dendrite. Narrow bandwidths of surge frequency (resonating) enable cortical circuits to use specific carrier frequencies, which isolate the processing of those circuits from other circuits. Resonating greatly enhances the intensity and duration of electrical activity of a neuron over a narrow frequency range, which underlies attention in its various modes. Within the minicolumn, separation of the central resonating circuit from the surrounding signal processing network separates “having” subjective impressions from “thinking about” them. Resonating neurons in the insular cortex apparently underlie cognitive impressions of feelings.     

Masked and unmasked priming in schizophrenia

Dehaene et al. (2003) showed an absence of conscious, but not masked, conflict effects when patients with schizophrenia performed a number-categorisation priming task. We aimed to replicate these influential results using a different word-categorisation priming task. Counter to Dehaene et al.’s findings, 21 patients and 20 healthy controls showed similar congruence effects for both masked and visible primes. Within patients, a reduced congruence effect for visible primes associated with longer duration of illness and more severe behavioural disorganisation. Patients, unlike controls, were no slower to respond to targets that followed visible compared to masked primes. Conscious conflict effects on priming tasks are not universally reduced in schizophrenia but may associate with chronicity and behavioural disorganisation. That patients were no slower when the preceding primes were clearly visible accords with evidence elsewhere that information processing in schizophrenia is driven more by immediate conscious experience and constrained less by prior events.     

Transfer of Work Decrement in Motor Learning

Two experiments tested the hypothesis that the decremental effects of massed practice are due to the development of a negative drive (Hull’s I_r). The results indicated that the decremental effects of massed practice on either the pursuit rotor or the two-hand coordinator do not transfer to depress performance or reminiscence on the other task. The results did not support Hull’s drive interpretation but were explained by theories attributing decrement to a decreased level of arousal.     

Gender-Moderated Dorsolateral Prefrontal Reductions in 22q11.2 Deletion Syndrome: Implications for Risk for Schizophrenia

To investigate the impact of the microdeletion on morphology of the prefrontal cortex in 22q11.2 Deletion Syndrome (22q11.2 DS), high-resolution, anatomic magnetic resonance imaging was performed on 19 children and adolescents with 22q11.2 DS (11 females, 8 males) and 18 unaffected controls (10 females, 8 males). Tissue volumes of the dorsolateral, dorsomedial, orbitolateral, and orbitomedial prefrontal cortex were measured. Tasks of executive function and working memory were administered to investigate the association between anatomy and function. Whole brain volume and frontal lobe tissue volume were preserved in girls but reduced in boys with 22q11.2 DS relative to age-matched controls. Dorsolateral prefrontal cortex (DLPFC) volumes were reduced in participants with 22q11.2 DS, although the gender-by-diagnosis effect found for frontal lobe was not as robust for DLPFC. DLPFC volumes were associated with performance on tasks of planning and emotional facial recognition. Longitudinal studies are needed to clarify whether gender differences in frontal lobe and DLPFC persist with development, and whether the volumes of the DLPFC are associated with eventual deterioration in adaptive/psychosocial function that may presage the onset of schizophrenia, for which individuals with 22q11.2 DS are at a disproportionately high risk.     

Neural correlates of stimulus response and stimulus outcome shifting in healthy participants and MS patients

Introduction

Adaptation to changing situations can be mediated by two strategies: (1) Evaluation of a response and (2) Evaluation of outcome values in relation to objects. Previous studies indicate that response shifting is associated with a network comprising the left frontal cortex and parietal cortex connected by the superior longitudinal fascicle, whereas outcome evaluation is associated with a network consisting of the orbitofrontal cortex, amygdala and uncinate fascicle. However, these studies rarely compared both kinds of adaptation directly and existing fMRI studies with healthy subjects are not informative about the role of the two fiber systems.

Methods

We analyzed stimulus response shifting and stimulus outcome shifting in two studies, one fMRI-study on healthy participants and one study on patients with MS involving structural MRI (Diffusion Tensor Imaging, Voxel Based Morphometry, Ventricular volumetry). Two tasks were used, identical in presentation but different in instruction, controlling for effects of lower level processing. In the SRS task, participants had to perform a “Go” or “NoGo” response depending on a stimulus change: if the stimulus remained the same, they had to continue with the former type of response, if it changed they had to adapt their response pattern. In the SOS task they had to perform a “Go” response only if the presented stimulus corresponded to that of an internal alternating series.

Results

fMRI findings showed that SRS is related to a bilateral parietal-premotor network. In the left hemisphere the prefrontal cortex was also involved. SOS was lateralized to the right hemisphere, particularly to the anterior temporal pole and amygdala, and the inferior parietal cortex. MS patients impaired on this task suffered from lesions in the right uncinate fascicle and showed an enlarged right frontal lateral ventricle.

Conclusion

With physically identical tasks, a functional neuronal segregation can be demonstrated for stimulus response shifting (bilateral activations with a focus in the left prefrontal cortex) and stimulus outcome shifting (right anterior temporal lobe and right supramarginal gyrus).     

The amygdalostriatal and corticostriatal effective connectivity in anticipation and evaluation of facial attractiveness

Decision-making consists of several stages of information processing, including an anticipation stage and an outcome evaluation stage. Previous studies showed that the ventral striatum (VS) is pivotal to both stages, bridging motivation and action, and it works in concert with the ventral medial prefrontal cortex (vmPFC) and the amygdala. However, evidence concerning how the VS works together with the vmPFC and the amygdala came mainly from neuropathology and animal studies; little is known about the dynamics of this network in the functioning human brain. Here we used fMRI combined with dynamic causal modeling (DCM) to investigate the information flow along amygdalostriatal and corticostriatal pathways in a facial attractiveness guessing task. Specifically, we asked participants to guess whether a blurred photo of female face was attractive and to wait for a few seconds (“anticipation stage”) until an unblurred photo of feedback face, which was either attractive or unattractive, was presented (“outcome evaluation stage”). At the anticipation stage, the bilateral amygdala and VS showed higher activation for the “attractive” than for the “unattractive” guess. At the outcome evaluation stage, the vmPFC and the bilateral VS were more activated by feedback faces whose attractiveness was congruent with the initial guess than by incongruent faces; however, this effect was only significant for attractive faces, not for unattractive ones. DCM showed that at the anticipation stage, the choice-related information entered the amygdalostriatal pathway through the amygdala and was projected to the VS. At the evaluation stage, the outcome-related information entered the corticostriatal pathway through the vmPFC. Bidirectional connectivities existed between the vmPFC and VS, with the VS-to-vmPFC connectivity weakened by unattractive faces. These findings advanced our understanding of the reward circuitry by demonstrating the pattern of information flow along the amygdalostriatal and corticostriatal pathways at different stages of decision-making.     

基于双加工理论解释下信念偏差效应的神经机制

信念偏差效应是指人们已有的知识信念对逻辑推理的影响现象.对此,双加工理论认为这是由于信念偏向系统和逻辑分析系统之间的冲突所导致的.近年来,该理论得到来自认知神经科学证据的有力支持:一方面,基于功能磁共振成像(fMRI)、近红外光谱(NIRS)以及重复性经颅磁刺激(rTMS)等技术的研究从不同角度证实右侧前额皮层与信念偏差抑制有关;另一方面,基于脑电(ERP)的研究表明,晚期正成分和晚期负成分可能参与了不同推理类型下信念偏差效应的认知加工.未来的研究可以从工作记忆、不同加工阶段、推理前提本身可信度、实验分析、实验材料生态学效度以及思维训练等方面对信念偏差效应作进一步探索.