Emotion recognition, symptoms of depression, and fluid intelligence after frontal lobe lesions

Frontal lobe lesions have been associated with executive impairments and changes in emotional/social function. Empirical studies using emotion recognition tasks in people with frontal lesions have indeed reported impairments that are predominantly associated with medial lesions. However, work has also identified a fronto-parietal 'multiple demand' (MD) network that is engaged in a wide variety of cognitive tasks. Previous studies have shown that fluid intelligence (IQ) scores, treated as a marker of MD function, completely account for deficits in some, but not all, tests of putatively separate executive functions. Here, a group of 39 participants with frontal lesions showed significant impairments (relative to age, sex and premorbid IQ-matched controls) on a measure of fluid IQ and 4 emotion recognition tasks. They also had higher levels of depression symptoms. Depression symptoms did not account for emotion task impairment. Fluid IQ completely accounted for the impairments in one 'emotion task' of inferring the emotion likely to be experienced in each of a series of vignettes. However, whilst fluid IQ was correlated with the other emotion measures (tests of categorising emotional expression from faces, eyes, and non-verbal vocalisations), significant variance was left unexplained. The significant intercorrelations between these residual scores was suggestive of a common 'non-fluid IQ' factor that may have an association with left lateral frontal lesions. The results are discussed in terms of the importance of identifying common general cognitive influences on tests of ostensibly specific functions in clinical assessments and research studies.