The Influence of the Right/Left and of the Frontal/Temporal Atrophy on the Generation and Control of Emotions: A Review of Data Gathered in Patients with Fronto-Temporal Degeneration

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.