Guido Gainotti

It is generally accepted that emotions are represented more in the right than in the left hemisphere and that temporal and frontal brain structures play a prominent role in functions of representation and control of emotions. It is, however, unclear if the right hemisphere prevalence concerns both the generation and the control of emotions. To clarify this problem, studies dealing with the emotional and behavioural disorders of patients with a right/left and a temporal/frontal variant of frontotemporal degeneration were included in a structured narrative review. A strong prevalence of right-sided atrophy was found in patients with emotion comprehension disorders, but different categories of emotions were affected in patients with temporal and frontal lesions. In the first case, comprehension disorders mainly affected ‘basic emotions’, whereas in the second case they preferentially concerned social and cognitive ‘complex emotions’. A weaker prevalence of right-sided atrophy was found in patients with emotional generation disorders (apathy and empathy) and in those with defects of emotional control (disinhibition). This difference between results obtained on tasks of comprehension and of control of emotions can be due to the fact that ‘apathy’, ‘empathy’ and ‘disinhibition’ can be considered as ‘umbrella terms’, covering behavioural domains larger than those allowed by a strict definition of emotions. The methodological heterogeneity and the observational nature of the evidence proposed suggest to consider the observed temporal–frontal hierarchy as a hypothesis supported by converging but heterogeneous clinical and neuroimaging observations.

Introduction: It is generally accepted that emotions are represented more in the right than in the left hemisphere and that temporal and frontal brain structures play a prominent role in functions of representation and of control of emotions. It is, however unclear if the right hemisphere prevalence concerns both the generation and the control of emotions. Aims of the study: In this study, I tried to clarify this problem by reviewing the emotional and behavioral disorders shown by patients with a right/left and a temporal/frontal variant of frontotemporal degeneration. Results: A strong prevalence of right-sided atrophy was found in patients with emotion comprehesion disorders, but different emotional comprehension defects were observed in patients with temporal and with frontal lesions. In the first case the defect mainly affected the ‘basic emotions’, whereas in patients with frontal atrophy the defect concerned more social and cognitive ‘complex emotions’. A weaker prevalence of right-sided atrophy was found in patients with emotional generation disorders (apathy and empathy) and in those with defects of emotional control (disinhibition). Discussion: This quantitative difference between results obtained on tasks of ‘emotional comprehension’ and of generation and control of emotions can de due to the fact that some of the latter behavioral disorders (such as ‘apathy’, ‘empathy’ and ‘disinhibition’) cannot be precisely defined and identified, because they can be considered as ‘umbrella terms’, covering behavioral domains larger than those allowed by a strict definition of emotions.

Introduction: An association between recognition disorders of familiar people and other unique entities (UEs), such as famous buildings, is often reported in patients showing a right variant of frontotemporal degeneration (FTD). However, the clinical context and the modality-specific or semantic nature of these disorders have not been clarified by group studies of these patients. Aims of the study: Since a recent consensus statement from the International Working Group on FTD has called for the clarification of these issues, I undertook a review of single-case reports that explored this issue. This review allowed me to identify 11 papers reporting patients affected by a ‘semantic’ or a ‘behavioral’ variant of right FTD. Results: A detailed analysis of these patients suggested the following: (a) the incidence of this association is similar in the ‘semantic’ and ‘behavioral’ variants of right FTD; (b) this association is not systematically observed in patients with a ‘prosopagnosic’ form of the ‘semantic variant, whereas it is more frequent in the ‘properly semantic’ and in the ‘behavioral’ variants; and (c) in these two last groups of patients, the association between poor recognition of familiar people and of other unique entities is usually observed both in the verbal and in the pictorial modalities. Discussion: These results seem to indicate that recognition defects concerning both familiar people and other UEs are due to modality-specific and semantic disorders mainly affecting the right hemisphere’s pictorial knowledge.

The aim of the present review will consist of discussing the different forms of familiar people recognition disorders observed in the right and left variants of semantic dementia. The review will start with a summary of the main cognitive models of familiar people recognition and of the neuroanatomical correlates of the processing stages proposed by these models. In this section, the role played by ‘familiarity feelings’ and by the properly ‘semantic’ aspects of familiar people recognition in the recognition of familiar people will be taken separately into account. The different roles played by the right and left anterior temporal lobes in each of these components of the system will also be stressed. In the second part of the review, I will discuss results obtained by patients with right and left variants of semantic dementia on tasks assessing ‘familiarity feelings’ and the distinction between general and social knowledge, reaching the following conclusions: (a) recognition disorders shown by patients with a right variant of semantic dementia are due to more to the disruption of pre‐semantic mechanisms allowing the automatic generation of familiarity feelings than to properly semantic defects; (b) the right anterior temporal lobe (ATL) supports more the concrete than the abstract components of ‘social knowledge’; (c) the right ATL can store only information that can be represented in a concrete pictorial format whereas the left ATL mainly stores information that can be represented only through abstract linguistic propositions (240).

Anosognosia (from the ancient Greek—a-, “without,” nosos, “disease,” and gnōsis, “knowledge”) has been recognised as one of the most complex syndromes investigated from different theoretical and clinical perspectives in patients with brain damage since the beginning of the last century (see

Introduction: ‘Associative prosopagnosia’ and ‘associative phonagnosia’ are high-level post-perceptual face and voice recognition defects due to right anterior temporal lesions, but the relations between these two disorders are uncertain. It is, indeed, not clear if face and voice recognition disorders observed in these patients must be considered as independent modality-specific recognition defects or as fragments of a more general semantic disorder concerning the multimodal representation of known persons. Aims of this study: In this review, the relations between associative forms of face and voice recognition disorders were investigated in all patients with right anterior temporal lesions reported in the literature. A prevalence of ‘pure’ (modality-specific) forms could indicate that these are independent, modality-specific recognition defects, whereas a high frequency of voice- and face-associated disorders could suggest that they are components of a multimodal semantic disruption. Results: Results show that ‘associative prosopagnosia’ and ‘associative phonagnosia’ are observed sometimes as ‘pure’ forms, other times as associations between verbal and non-verbal defects of person recognition, and still other times as associations restricted to the non-verbal (face and voice) modalities of person recognition. Furthermore, in a patient with a multimodal face and voice recognition disorder, the lesion involved the right temporal pole, considered as the locus of convergence of face and voice recognition modalities. Discussion: These data suggest that specific lesions of the right anterior temporal lobes can disrupt the highest modality-specific levels of face and voice representations, whereas other equally selective lesions can disrupt the locus of convergence of face and voice recognition modalities.

In the original publication [...].

Background/Objectives: The aim of this investigation consisted of evaluating if the prevalence of anosognosia in right-brain-damaged patients is greater for tasks in which the right hemisphere plays a dominant role and if this prevalence is at least in part due to automatic processing mechanisms typical of this hemisphere. Methods: We assessed defective awareness of person-recognition disorders in 14 patients with the right variant (rv-SD) and 15 with the left variant (lv-SD) of Semantic Dementia. A battery exploring person-recognition disorders through familiarity judgement of faces, voices and names was applied. In patients with pathological performance in one of these modalities, anosognosia was assessed comparing the patients’ subjective judgment to the objective result of their performance (objective evaluation) and to the subjective judgment given by an informed caregiver (external comparison). Results: In the comparison between subjective awareness and objective scores in the various person-recognition modalities, only anosognosia for face recognition disorders was significantly more frequent of in patients with rv-SD. When compared to their caregivers, subjects with rv-SD were significantly less aware than caregivers of their difficulties only on face recognition. On the contrary, patients with a lv-SD showed a greater (non-significant) trend to be unaware of their name recognition deficit. Conclusions: These data show that the prevalence of anosognosia in right-brain-damaged patients is greater for face recognition in which the right hemisphere plays a dominant role and that this prevalence is at least in part due to automatic processing mechanisms (evocation of familiarity feelings) typical of this hemisphere.