Functional characterization and synergic action of fungal xylanase and arabinofuranosidase for production of xylooligosaccharides.

Plant cell wall degrading enzymes are key technological components in biomass bioconversion platforms for lignocellulosic materials transformation. Cost effective production of enzymes and identification of efficient degradation routes are two economic bottlenecks that currently limit the use of renewable feedstocks through an environmental friendly pathway. The present study describes the hypersecretion of an endo-xylanase (GH11) and an arabinofuranosidase (GH54) by a fungal expression system with potential biotechnological application, along with comprehensive characterization of both enzymes, including spectrometric analysis of thermal denaturation, biochemical characterization and mode of action description. The synergistic effect of these enzymes on natural substrates such as sugarcane bagasse, demonstrated the biotechnological potential of using GH11 and GH54 for production of probiotic xylooligosaccharides from plant biomass. Our findings shed light on enzymatic mechanisms for xylooligosaccharide production, as well as provide basis for further studies for the development of novel enzymatic routes for use in biomass-to-bioethanol applications.

The Iowa Gambling Task and the somatic marker hypothesis: some questions and answers.

A recent study by Maia and McClelland on participants' knowledge in the Iowa Gambling Task suggests a different interpretation for an experiment we reported in 1997. The authors use their results to question the evidence for the somatic marker hypothesis. Here we consider whether the authors' conclusions are justified.

Pathological laughter and crying: a link to the cerebellum.

Patients with pathological laughter and crying (PLC) are subject to relatively uncontrollable episodes of laughter, crying or both. The episodes occur either without an apparent triggering stimulus or following a stimulus that would not have led the subject to laugh or cry prior to the onset of the condition. PLC is a disorder of emotional expression rather than a primary disturbance of feelings, and is thus distinct from mood disorders in which laughter and crying are associated with feelings of happiness or sadness. The traditional and currently accepted view is that PLC is due to the damage of pathways that arise in the motor areas of the cerebral cortex and descend to the brainstem to inhibit a putative centre for laughter and crying. In that view, the lesions 'disinhibit' or 'release' the laughter and crying centre. The neuroanatomical findings in a recently studied patient with PLC, along with new knowledge on the neurobiology of emotion and feeling, gave us an opportunity to revisit the traditional view and propose an alternative. Here we suggest that the critical PLC lesions occur in the cerebro-ponto-cerebellar pathways and that, as a consequence, the cerebellar structures that automatically adjust the execution of laughter or crying to the cognitive and situational context of a potential stimulus, operate on the basis of incomplete information about that context, resulting in inadequate and even chaotic behaviour.

A role for left temporal pole in the retrieval of words for unique entities.

Both lesion and functional imaging studies have implicated sectors of high-order association cortices of the left temporal lobe in the retrieval of words for objects belonging to varied conceptual categories. In particular, the cortices located in the left temporal pole have been associated with naming unique persons from faces. Because this neuroanatomical-behavioral association might be related to either the specificity of the task (retrieving a name at unique level) or to the possible preferential processing of faces by anterior temporal cortices, we performed a PET imaging experiment to test the hypothesis that the effect is related to the specificity of the word retrieval task. Normal subjects were asked to name at unique level entities from two conceptual categories: famous landmarks and famous faces. In support of the hypothesis, naming entities in both categories was associated with increases in activity in the left temporal pole. No main effect of category (faces vs. landmarks/buildings) or interaction of task and category was found in the left temporal pole. Retrieving names for unique persons and for names for unique landmarks activate the same brain region. These findings are consistent with the notion that activity in the left temporal pole is linked to the level of specificity of word retrieval rather than the conceptual class to which the stimulus belongs.

Neural correlates of naming actions and of naming spatial relations.

Ina [(15)O] water PET experiment, 10 normal subjects retrieved words denoting actions (performed with or without an implement), and another 10 normal subjects retrieved words denoting the spatial relations between objects. Our objective was to test the following hypothesis: that the salient neural activity associated with naming actions and spatial relations occurs in left frontal operculum and left parietal association cortices, but not in the left inferotemporal cortices (IT) or in the right parietal association cortices. There were two control tasks, one requiring a decision on the orientation of unknown faces (a standard control task in our laboratory) and another requiring the retrieval of words denoting the concrete entities used in the action and spatial relations tasks. In accordance with the hypothesis, both naming actions and spatial relations (using the face orientation task as control activated the left frontal operculum; naming actions also activated the left parietal lobe. However, sectors of the left posterior IT were also engaged in both naming actions and spatial relations. When the naming of concrete entities was subtracted from the naming of actions performed with such entities, area MT in the posterior temporo-occipital region was activated bilaterally. On the other hand, when naming of the concrete entities was subtracted from the naming of spatial relations, left parietal activation was found, and when two tasks of naming spatial relations were contrasted to each other bilateral parietal activation was seen, right when abstract stimuli were used and left when concrete objects were used. The activity in posterior IT is thought to be related to object processing and possibly name retrieval at a subconscious level.

Single-neuron responses to emotional visual stimuli recorded in human ventral prefrontal cortex.

Both lesion and functional imaging studies in humans, as well as neurophysiological studies in nonhuman primates, demonstrate the importance of the prefrontal cortex in representing the emotional value of sensory stimuli. Here we investigated single-neuron responses to emotional stimuli in an awake person with normal intellect. Recording from neurons within healthy tissue in ventral sites of the right prefrontal cortex, we found short-latency (120-160 ms) responses selective for aversive visual stimuli.

A neural basis for the retrieval of words for actions.

Although much has been learned in recent years about the neural basis for retrieving words denoting concrete entities, the neural basis for retrieving words denoting actions remains poorly understood. We addressed this issue by testing two specific anatomical hypotheses. (1) Naming of actions depends not only on the classical implementation structures of the left frontal operculum, but also on mediational structures located in left premotor/prefrontal areas. (2) The neural systems subserving naming of actions and naming of concrete entities are segregated. The study used the lesion method and involved 75 subjects with focal, stable lesions in the left or right hemispheres, whose magnetic resonance data were analysed with a three-dimensional reconstruction method. The experimental tasks were standardised procedures for measuring action and object naming. The findings offered partial support for the hypotheses, in that: (1) lesions related to impaired action naming overlapped maximally in the left frontal operculum and in the underlying white matter and anterior insula; and (2) lesions of the left anterior temporal and inferotemporal regions, which produce impairments in naming of concrete entities, did not cause action naming deficits. A follow-up analysis indicated that action naming impairments, especially when they were disproportionate relative to concrete entity naming impairments, were not only associated with premotor/prefrontal lesions, but also with lesions of the left mesial occipital cortex and of the paraventricular white matter underneath the supramarginal and posterior temporal regions.

Subcortical and cortical brain activity during the feeling of self-generated emotions.

In a series of [15O]PET experiments aimed at investigating the neural basis of emotion and feeling, 41 normal subjects recalled and re-experienced personal life episodes marked by sadness, happiness, anger or fear. We tested the hypothesis that the process of feeling emotions requires the participation of brain regions, such as the somatosensory cortices and the upper brainstem nuclei, that are involved in the mapping and/or regulation of internal organism states. Such areas were indeed engaged, underscoring the close relationship between emotion and homeostasis. The findings also lend support to the idea that the subjective process of feeling emotions is partly grounded in dynamic neural maps, which represent several aspects of the organism's continuously changing internal state.

A role for somatosensory cortices in the visual recognition of emotion as revealed by three-dimensional lesion mapping.

Although lesion and functional imaging studies have broadly implicated the right hemisphere in the recognition of emotion, neither the underlying processes nor the precise anatomical correlates are well understood. We addressed these two issues in a quantitative study of 108 subjects with focal brain lesions, using three different tasks that assessed the recognition and naming of six basic emotions from facial expressions. Lesions were analyzed as a function of task performance by coregistration in a common brain space, and statistical analyses of their joint volumetric density revealed specific regions in which damage was significantly associated with impairment. We show that recognizing emotions from visually presented facial expressions requires right somatosensory-related cortices. The findings are consistent with the idea that we recognize another individual's emotional state by internally generating somatosensory representations that simulate how the other individual would feel when displaying a certain facial expression. Follow-up experiments revealed that conceptual knowledge and knowledge of the name of the emotion draw on neuroanatomically separable systems. Right somatosensory-related cortices thus constitute an additional critical component that functions together with structures such as the amygdala and right visual cortices in retrieving socially relevant information from faces.

Emotion, decision making and the orbitofrontal cortex.

The somatic marker hypothesis provides a systems-level neuroanatomical and cognitive framework for decision making and the influence on it by emotion. The key idea of this hypothesis is that decision making is a process that is influenced by marker signals that arise in bioregulatory processes, including those that express themselves in emotions and feelings. This influence can occur at multiple levels of operation, some of which occur consciously and some of which occur non-consciously. Here we review studies that confirm various predictions from the hypothesis. The orbitofrontal cortex represents one critical structure in a neural system subserving decision making. Decision making is not mediated by the orbitofrontal cortex alone, but arises from large-scale systems that include other cortical and subcortical components. Such structures include the amygdala, the somatosensory/insular cortices and the peripheral nervous system. Here we focus only on the role of the orbitofrontal cortex in decision making and emotional processing, and the relationship between emotion, decision making and other cognitive functions of the frontal lobe, namely working memory.

Long-term sequelae of prefrontal cortex damage acquired in early childhood.

Frontal lobe dysfunction is often invoked as a contributing factor in developmental disorders characterized by chronic maladaptive behavior, but interpretation of relevant neuropsychological findings has been hampered by the limited information available regarding the consequences of focal prefrontal damage early in life. We describe here the long-term behavioral and cognitive sequelae of damage to prefrontal cortex in two young adult patients who had sustained their brain damage prior to 16 months of age. In the context of normal neurological examinations, both cases had remarkable histories of impaired decision making, behavioral dyscontrol, social defects, and abnormal emotion. Performances were primarily normal on a broad range of neuropsychological measures (intellect, memory, language, academic achievement, visual perception, and visuoconstruction), but selective impairments of executive function were evident. Early dysfunction in the prefrontal region may result in severe and chronic social maladjustment despite largely normal cognitive abilities. These findings can help inform neuropsychological evaluation of patients with possible prefrontal dysfunction in the setting of developmental disabilities or early brain trauma.

Impairment of social and moral behavior related to early damage in human prefrontal cortex.

The long-term consequences of early prefrontal cortex lesions occurring before 16 months were investigated in two adults. As is the case when such damage occurs in adulthood, the two early-onset patients had severely impaired social behavior despite normal basic cognitive abilities, and showed insensitivity to future consequences of decisions, defective autonomic responses to punishment contingencies and failure to respond to behavioral interventions. Unlike adult-onset patients, however, the two patients had defective social and moral reasoning, suggesting that the acquisition of complex social conventions and moral rules had been impaired. Thus early-onset prefrontal damage resulted in a syndrome resembling psychopathy.

Recognition of facial emotion in nine individuals with bilateral amygdala damage.

Findings from several case studies have shown that bilateral amygdala damage impairs recognition of emotions in facial expressions, especially fear. However, one study did not find such an impairment, and, in general, comparison across studies has been made difficult because of the different stimuli and tasks employed. In a collaborative study to facilitate such comparisons, we report here the recognition of emotional facial expressions in nine subjects with bilateral amygdala damage, using a sensitive and quantitative assessment. Compared to controls, the subjects as a group were significantly impaired in recognizing fear, although individual performances ranged from severely impaired to essentially normal. Most subjects were impaired on several negative emotions in addition to fear, but no subject was impaired in recognizing happy expressions. An analysis of response consistency showed that impaired recognition of fear could not be attributed simply to mistaking fear for another emotion. While it remains unclear why some subjects with amygdala damage included here are not impaired on our task, the results overall are consistent with the idea that the amygdala plays an important role in triggering knowledge related to threat and danger signaled by facial expressions.

Different contributions of the human amygdala and ventromedial prefrontal cortex to decision-making.

The somatic marker hypothesis proposes that decision-making is a process that depends on emotion. Studies have shown that damage of the ventromedial prefrontal (VMF) cortex precludes the ability to use somatic (emotional) signals that are necessary for guiding decisions in the advantageous direction. However, given the role of the amygdala in emotional processing, we asked whether amygdala damage also would interfere with decision-making. Furthermore, we asked whether there might be a difference between the roles that the amygdala and VMF cortex play in decision-making. To address these two questions, we studied a group of patients with bilateral amygdala, but not VMF, damage and a group of patients with bilateral VMF, but not amygdala, damage. We used the "gambling task" to measure decision-making performance and electrodermal activity (skin conductance responses, SCR) as an index of somatic state activation. All patients, those with amygdala damage as well as those with VMF damage, were (1) impaired on the gambling task and (2) unable to develop anticipatory SCRs while they pondered risky choices. However, VMF patients were able to generate SCRs when they received a reward or a punishment (play money), whereas amygdala patients failed to do so. In a Pavlovian conditioning experiment the VMF patients acquired a conditioned SCR to visual stimuli paired with an aversive loud sound, whereas amygdala patients failed to do so. The results suggest that amygdala damage is associated with impairment in decision-making and that the roles played by the amygdala and VMF in decision-making are different.

Investigating the biology of consciousness.

The fact that consciousness is a private, first-person phenomenon makes it more difficult to study than other cognitive phenomena that, although being equally private, also have characteristic behavioural signatures. Nonetheless, by combining cognitive and neurobiological methods, it is possible to approach consciousness, to describe its cognitive nature, its behavioural correlates, its possible evolutionary origin and functional role; last but not least, it is possible to investigate its neuroanatomical and neurophysiological underpinnings. In this brief essay I distinguish between two kinds of consciousness: core consciousness and extended consciousness. Core consciousness corresponds to the transient process that is incessantly generated relative to any object with which an organism interacts, and during which a transient core self and transient sense of knowing are automatically generated. Core consciousness requires neither language nor working memory, and needs only a brief short-term memory. Extended consciousness is a more complex process. It depends on the gradual build-up of an autobiographical self, a set of conceptual memories pertaining to both past and anticipated experiences of an individual, and it requires conventional memory. Extended consciousness is enhanced by language.