Does the right hemisphere retain functional characteristics typical of the emotional adaptive system? An evolutionary approach to the problem of brain asymmetries.

The right and left hemispheres host two complementary adaptive systems with a right-sided prevalence of automatic and unconscious processing modes, typical of the 'emotional system', and a left-sided prevalence of propositional and conscious processing modes typical of the 'cognitive system' The principal right hemispheric syndromes (and the functioning modes typical of this hemisphere) are, indeed, characterized by automatic and unconscious processing modalities. Thus, the unilateral neglect syndrome discloses a defective automatic (and spared intentional) spatial orienting of attention; face and voice recognition disorders are due to disruption of mechanisms that automatically generate familiarity feelings and anosognosia seems due to the unconscious loss of personal significance attributed by the patient to the pathological event. Since emotions were the only adaptive system existing before the development of language (which is provided of a strong capacity to develop and shape cognition), the persistence in the right hemisphere of mechanisms typical of the emotional system strongly supports an evolutionary model of brain laterality. (160 words).

Emotions related to threatening events are mainly linked to the right hemisphere.

A recent meta-analysis of functional neuroimaging contrasts between emotional and neutral face processing has shown that the processing of facial emotions can be better classified according to threat detection than emotional valence, with the authors suggesting that their data are inconsistent with both the right-hemisphere and valence models of emotional laterality. I report empirical and theoretical data indicating that facial expressions are better classified according to threat detection than to the distinction between positive and negative emotions. I challenge, however, the claim that laterality effects provide little support to the right-hemisphere model of emotional laterality. This claim contrasts with neuropsychological and psychophysiological investigations that have shown that the right hemisphere has a graded prevalence for emotions provoked by threatening events. A reanalysis of data obtained in the target study suggests that the reported data are not necessarily inconsistent with a model assuming a graded, right-hemisphere dominance for emotions. I present a model of hemispheric asymmetries that could be consistent with the assumption that the right hemisphere's dominance for emotions may mainly be concerned with threatening events.

A historical approach to models of emotional laterality.

In this paper I discuss the main models that have tried to explain brain asymmetries for emotions. The first models, based on clinical observations, proposed either a general right hemisphere dominance for emotions (the'right hemisphere') model or a different specialization of the right hemisphere for negative and of the left hemisphere for positive emotions (the'valence' model). In more recent times new models, based on partly modified versions of the previous ones have been proposed. The revised version of the 'valence' model, labeled the 'approach-avoidance' model maintained that hemispheric asymmetries are not related to the valence of the emotional stimulus but to the motivational (approach vs avoidance) system that is engaged by that stimulus. On the contrary, revised versions of the 'right hemisphere' hypothesis proposed graded versions of this model, maintaining that only some kinds or some levels of emotions are clearly right lateralized. One version of these models (the'emotion type hypothesis') assumed that only elementary basic emotions should be subsumed by the right hemisphere, wheres more complex social emotions should be subtended by the left hemisphere. The other version (the 'schematic level of emotion hypothesis') assumed that the right hemisphere should subsume only the basic 'schematic' level of emotions, characterized by an automatic and unconscious processing, whereas the more propositional and conscious 'conceptual' level could be less lateralized or subsumed by the left hemisphere. This last model is supported by the obsevation that the right hemisphere reveals a modus operandi (i.e. a prevalence of the 'automatic' over the 'intentional' and of the 'unconscious' over the 'conscious' functional processing) that is typical of the 'schematic level of emotions.

Human Recognition: The Utilization of Face, Voice, Name and Interactions-An Extended Editorial.

The many stimulating contributions to this Special Issue of Brain Science focused on some basic issues of particular interest in current research, with emphasis on human recognition using faces, voices, and names [...].

Mainly Visual Aspects of Emotional Laterality in Cognitively Developed and Highly Social Mammals-A Systematic Review.

Several studies have shown that emotions are asymmetrically represented in the human brain and have proposed three main models (the 'right hemisphere hypothesis', the 'approach-withdrawal hypothesis' and the 'valence hypothesis') that give different accounts of this emotional laterality. Furthermore, in recent years, many investigations have suggested that a similar emotional laterality may also exist in different animal taxa. However, results of a previous systematic review of emotional laterality in non-human primates have shown that some of these studies might be criticized from the methodological point of view and support only in part the hypothesis of a continuum in emotional laterality across vertebrates. The aim of the present review therefore consisted in trying to expand this survey to other cognitively developed and highly social mammals, focusing attention on mainly visual aspects of emotional laterality, in studies conducted on the animal categories of horses, elephants, dolphins and whales. The 35 studies included in the review took into account three aspects of mainly visual emotional laterality, namely: (a) visual asymmetries for positive/familiar vs. negative/novel stimuli; (b) lateral position preference in mother-offspring or other affiliative interactions; (c) lateral position preference in antagonistic interactions. In agreement with data obtained from human studies that have evaluated comprehension or expression of emotions at the facial or vocal level, these results suggest that a general but graded right-hemisphere prevalence in the processing of emotions can be found at the visual level in cognitively developed non-primate social mammals. Some methodological problems and some implications of these results for human psychopathology are briefly discussed.

Is Anosognosia for Left-Sided Hemiplegia Due to a Specific Self-Awareness Defect or to a Poorly Conscious Working Mode Typical of the Right Hemisphere?

This review aimed to evaluate whether the association between 'anosognosia for hemiplegia' and lesions of the right hemisphere points to a special self-awareness role of the right side of the brain, or could instead be due to a working mode typical of the right hemisphere. This latter viewpoint is consistent with a recently proposed model of human brain asymmetries that assumes that language lateralization in the left hemisphere might have increased the left hemisphere's level of consciousness and intentionality in comparison with the right hemisphere's less conscious and more automatic functioning. To assess these alternatives, I tried to ascertain whether anosognosia is greater for left-sided hemiplegia than for other disorders provoked by right brain lesions, or whether unawareness prevails in tasks more clearly related to the disruption of the right hemisphere's more automatic (and less conscious) functioning. Data consistent with the first alternative would support the existence of a specific link between anosognosia for hemiplegia and self-awareness, whereas data supporting the second option would confirm the model linking anosognosia to a poorly conscious working mode typical of the right hemisphere. Analysis results showed that the incidence of anosognosia of the highly automatic syndrome of unilateral neglect was greater than that concerning the unawareness of left hemiplegia, suggesting that anosognosia for left-sided hemiplegia might be due to the poorly conscious working mode typical of the right hemisphere.

Why the use of ideographic codes does not improve communicative skills in patients with severe aphasia?

In his target article, Morin claims that ideographic codes are exceedingly difficult to use. In my commentary I will show that the use of Bliss symbols does not improve the communicative abilities of aphasic patients with severe language disorders. This failure to remediate communication disorders may result from disruption of inner language allowing to translate ideographic codes into spoken language.

Transcranial Direct Current Stimulation Effects on the Neural Substrate of Conceptual Representations.

The aim of this study was to shed light on the neural substrate of conceptual representations starting from the construct of higher-order convergence zones and trying to evaluate the unitary or non-unitary nature of this construct. We used the 'Thematic and Taxonomic Semantic (TTS) task' to investigate (a) the neural substrate of stimuli belonging to biological and artifact categories, (b) the format of stimuli presentation, i.e., verbal or pictorial, and (c) the relation between stimuli, i.e., categorial or contextual. We administered anodal transcranial direct current stimulation (tDCS) to different brain structures during the execution of the TTS task. Twenty healthy participants were enrolled and divided into two groups, one investigating the role of the anterior temporal lobes (ATL) and the other the temporo-parietal junctions (TPJ). Each participant underwent three sessions of stimulation to facilitate a control condition and to investigate the role of both hemispheres. Results showed that ATL stimulation influenced all conceptual representations in relation to the format of presentation (i.e., left-verbal and right-pictorial). Moreover, ATL stimulation modulated living categories and taxonomic relations specifically, whereas TPJ stimulation did not influence semantic task performances.

Apperceptive and Associative Forms of Phonagnosia.

PURPOSE OF REVIEW: Pronagnosia is a rare acquired or developmental pathological condition that consists of a selective difficulty to recognize familiar people by their voices. It can be distinguished into two different categories: apperceptive phonagnosia, which denotes a purely perceptual form of voice recognition disorder; and associative phonagnosia, in which patients have no perceptual defects, but cannot evaluate if the voice of a known person is or not familiar. The neural substrate of these two forms of voice recognition is still controversial, but it could concern different components of the core temporal voice areas and of extratemporal voice processing areas. This article reviews recent research on the neuropsychological and anatomo-clinical aspects of this condition. RECENT FINDINGS: Data obtained in group studies or single case reports of phonagnosic patients suggest that apperceptive phonagnosia might be due to disruption of the core temporal voice areas, bilaterally located in the posterior parts of the superior temporal gyrus, whereas associative phonagnosia might result from impaired access to structures where voice representations are stored, due to a disconnection of these areas from structures of the voice extended system. Although these results must be confirmed by further investigations, they represent an important step toward understanding the nature and neural substrate of apperceptive and associative forms of phonagnosia.

The Dynamic Interplay between Loss of Semantic Memory and Semantic Learning Capacity: Insight from Neologisms Learning in Semantic Variant Primary Progressive Aphasia.

Semantic Variant of Primary Progressive Aphasia (svPPA) has often been considered as a loss of knowledge stored in semantic memory, but might also be due to a general disruption of mechanisms allowing the acquisition, storage, and retrieval of semantic memories. In order to assess any parallelism in svPPA patients between loss of semantic knowledge and inability to acquire new semantic information, we administered a battery of semantic learning tasks to healthy individuals and svPPA patients, where they were requested to learn new conceptual representations and new word forms, and to associate the former with the latter. A strong relation was found between loss of semantic knowledge and disruption of semantic learning: (a) patients with severe svPPA had the lowest scores in the semantic learning tasks; (b) significant correlations were found between scores obtained in semantic learning tasks and scores obtained in semantic memory disorders in svPPA patients.

Some historical notes orienting towards brain mechanisms that could underlie hemispheric asymmetries.

The first minor aim of this synthetical historical survey consisted in showing that the discovery of the internal organization of language within the left hemisphere has been mainly determined by theoretical models and cultural factors, whereas the discovery of the left lateralisation of language and of the right lateralization of emotions and of other cognitive and perceptual functions has been mainly determined by empirical observations. A second more relevant aim of the survey consisted in discussing historical and more recent data suggesting that the different lateralisation of language and emotions has influenced not only the asymmetrical representation of other cognitive, affective and perceptual functions, but also (thank to the shaping influence of language on human cognition) of asymmetries regarding more general aspects of thought (such as the distinctions between 'propositional vs automatic' and 'conscious vs unconscious' ways of functioning). In the last part of the review, these data will be included in a more general discussion, concerning the brain functions that could be subsumed by the right hemisphere for three main reasons: (a) to avoid conflicts with the language mediated activities of the left hemisphere; (b) because of unconscious and automatic aspects of its non-verbal organisation or (c) due to the competition for cortical space determined by the development of language within the left hemisphere.

The Right Temporal Lobe and the Enhancement of Voice Recognition in Congenitally Blind Subjects.

BACKGROUND: Experimental investigations and clinical observations have shown that not only faces but also voices are predominantly processed by the right hemisphere. Moreover, right brain-damaged patients show more difficulties with voice than with face recognition. Finally, healthy subjects undergoing right temporal anodal stimulation improve their voice but not their face recognition. This asymmetry between face and voice recognition in the right hemisphere could be due to the greater complexity of voice processing. METHODS: To further investigate this issue, we tested voice and name recognition in twelve congenitally blind people. RESULTS: The results showed a complete overlap between the components of voice recognition impaired in patients with right temporal damage and those improved in congenitally blind people. Congenitally blind subjects, indeed, scored significantly better than control sighted individuals in voice discrimination and produced fewer false alarms on familiarity judgement of famous voices, corresponding to tests selectively impaired in patients with right temporal lesions. CONCLUSIONS: We suggest that task difficulty is a factor that impacts on the degree of its lateralization.

Which components of famous people recognition are lateralized? A study of face, voice and name recognition disorders in patients with neoplastic or degenerative damage of the right or left anterior temporal lobes.

We administered to large groups of patients with neoplastic or degenerative damage affecting the right or left ATL, the 'Famous People Recognition Battery' (FPRB), in which subjects are required to recognize the same 40 famous people through their faces, voices and names, to clarify which components of famous people recognition are lateralized. At the familiarity level, we found, as expected, a dissociation between a greater impairment of patients with right ATL lesions on the non-verbal (face and voice) recognition modalities and of those with left ATL lesions on name familiarity. Equally expected were results obtained at the naming level, because the worse naming scores for faces and voices were observed in left-sided patients. Less foregone were, for two reasons, results obtained at the semantic level. First, no difference was found between the two hemispheric groups when scores obtained on the verbal (name) and non-verbal (face and voice) recognition modalities were account for. Second, the face and voice recognition modalities showed a different degree of right lateralization. All groups of patients showed, indeed, both at the familiarity and at the semantic level, a greater difficulty in the recognition of voices regarding faces, but this difference reached significance only in patients with right ATL lesions, suggesting a greater right lateralization of the more complex task of voice recognition. A model aiming to explain the greater right lateralization of the more perceptually demanding voice modality of person recognition is proposed.

Hemispheric asymmetries for emotions in non-human primates: A systematic review.

A systematic review of investigations evaluating hemispheric asymmetries for emotions in primates was undertaken to individuate the most consistent lines of research allowing to check the hypothesis of a continuum in emotional lateralization across vertebrates. We reviewed studies on the lateralization of emotional expression (N = 31) and perception (N = 32) and of markers of emotional activation (N = 9), trying to distinguish those which had given respectively more consistent or more conflicting outcomes. Furthermore, we tried to identify the most strongly supported model of emotional lateralization. The most consistent results were obtained in studies investigating asymmetries in emotional expression at the facial level and in the perception of emotional facial expressions, whereas the most disappointing data were obtained in investigations evaluating possible neurophysiological markers of lateralized emotional activation. These results supported more the hypothesis of a continuity between humans and non-human primates than the more general hypothesis of a continuum between humans and all vertebrates. Furthermore, results supported more the 'right hemisphere' than the 'valence' model of emotional lateralization.

Emotions and the Right Hemisphere: Editorial.

The hypothesis assuming that the right hemisphere may play a critical role in emotional processing was raised by clinical data which showed that patients with right brain lesions often show abnormal patterns of emotional behavior [...].

Is There a Causal Link between the Left Lateralization of Language and Other Brain Asymmetries? A Review of Data Gathered in Patients with Focal Brain Lesions.

This review evaluated if the hypothesis of a causal link between the left lateralization of language and other brain asymmetries could be supported by a careful review of data gathered in patients with unilateral brain lesions. In a short introduction a distinction was made between brain activities that could: (a) benefit from the shaping influences of language (such as the capacity to solve non-verbal cognitive tasks and the increased levels of consciousness and of intentionality); (b) be incompatible with the properties and the shaping activities of language (e.g., the relations between language and the automatic orienting of visual-spatial attention or between cognition and emotion) and (c) be more represented on the right hemisphere due to competition for cortical space. The correspondence between predictions based on the theoretical impact of language on other brain functions and data obtained in patients with lesions of the right and left hemisphere was then assessed. The reviewed data suggest that different kinds of hemispheric asymmetries observed in patients with unilateral brain lesions could be subsumed by common mechanisms, more or less directly linked to the left lateralization of language.

The Difficult Integration between Human and Animal Studies on Emotional Lateralization: A Perspective Article.

Even if for many years hemispheric asymmetries have been considered as a uniquely human feature, an increasing number of studies have described hemispheric asymmetries for various behavioral functions in several nonhuman species. An aspect of animal lateralization that has attracted particular attention has concerned the hemispheric asymmetries for emotions, but human and animal studies on this subject have been developed as independent lines of investigation, without attempts for their integration. In this perspective article, after an illustration of factors that have hampered the integration between human and animal studies on emotional lateralization, I will pass to analyze components and stages of the processing of emotions to distinguish those which point to a continuum between humans and many animal species, from those which suggest a similarity only between humans and great apes. The right lateralization of sympathetic functions (involved in brain and bodily activities necessary in emergency situations) seems consistent across many animal species, whereas asymmetries in emotional communication and in structures involved in emotional experience, similar to those observed in humans, have been documented only in primates.

The relations between cognitive and motivational components of anosognosia for left-sided hemiplegia and the right hemisphere dominance for emotions: A historical survey.

Since the description of anosognosia for hemiplegia by Babinski (who also stressed the links between anosognosia and right hemisphere damage) both motivational and cognitive mechanisms have been advanced to explain this awareness disorder. In this review I will discuss first the neurophysiological mechanisms that can impede the discovery of the motor deficits contralateral to the brain lesion and then suggest that some instances of anosognosia for left-sided hemiplegia may also be due to motivational mechanisms of denial. Among the cognitive mechanisms, sensory feedback and intentional feed-forward disorders can lead to a poor awareness of the motor defects, whereas denial mechanisms could result from an interaction between the right hemisphere dominance for emotions and the anxiety raised by the catastrophic consequences of the brain damage. In particular, a maladaptive reaction to the personal implications of the brain lesion could be revealed by the presence of an implicit acknowledgement of the motor defect.