Academic journal article Cognitive, Affective and Behavioral Neuroscience

Ambiguous Emotion Recognition in Temporal Lobe Epilepsy: The Role of Expression Intensity

Academic journal article Cognitive, Affective and Behavioral Neuroscience

Ambiguous Emotion Recognition in Temporal Lobe Epilepsy: The Role of Expression Intensity

Article excerpt

Abstract The lateralization of emotion processing is cur- rently debated and may be further explored by examining facial expression recognition (FER) impairments in temporal lobe epilepsy (TLE). Furthermore, there is also debate in the literature whether FER deficits in individuals with TLE are more pronounced in the right than in the left hemisphere. Individuals with TLE were tested with an FER task designed to be more sensitive than those classically used to shed light on this issue. A total of 25 right- and 32 left-TLE patients, candidates for surgery, along with controls, underwent an FER task composed of stimuli shown not only at full-blown inten- sities (100 %), but also morphed to lower-intensity display levels (35 %, 50 %, and 75 %). The results showed that, as compared to controls, right-TLE patients showed deficits in the recognition of all emotional categories. Furthermore, when considering valence, right-TLE patients were impaired only in negative emotion recognition, but no deficits for positive emotions were highlighted in left-TLE patients. Finally, only the right-TLE patients' impairment was found to be related to the age of epilepsy onset. Our work demonstrates that the FER deficits in TLE span multiple emotional categories and show manifestations dependent on the laterality of the epileptic focus. Taken together, our findings provide the strongest evi- dence for the right-hemisphere model, but they also partially support the valence model. We suggest that current models are not exhaustive at explaining emotional-processing cere- bral control, and further that multistep models should be developed.

Keywords Emotional dominance . Facial expressions . Facial emotion recognition . Temporal lobe epilepsy . Expression intensity . Emotional lateralization

Although initial research had indicated a dominant role of the right hemisphere in emotional processing, more recent research has indicated that both hemispheres contribute to such processing (Demaree, Everhart, Youngstrom, & Harrison, 2005). Brain structures that are critically involved in emotional processing, such as the amygdala and the temporal cortices (Adolphs, 2010; Haxby, Hoffman, & Gobbini, 2000; Olson, Plotzker, & Ezzyat, 2007), are affect- ed by temporal lobe epilepsy (TLE), which is typically lateralized in focus, making the condition a window for the understanding of the laterality of emotion processing. As compared to cerebrovascular damage and transcranial magnetic stimulation (TMS), epilepsy presents several advantages. For instance, cerebrovascular damage is usually associated with a number of diverse cognitive impairments, particularly in the acute phase (Ferro, 2001). Furthermore, it is quite rare to observe a stroke patient presenting emotional deficits that are limited to "recognition," while it is usually reported that patients are affected by productive symptoms concerning emotions (such as the "catastrophic" reaction or the "depressive" reaction; Chemerinski & Robinson, 2000). Finally, aphasia is quite common after left stroke, and this could hinder the use of a labeling task to explore FER (de Freitas, 2012). On the other hand, it is quite difficult to reach subcortical structures with techniques such as TMS, because the impairments caused by single-pulse TMS are usually restricted to cortical areas (Walsh & Cowey, 2000). Furthermore, exact stimulation of the desired area cannot be guaranteed unless fMRI-guided TMS is used (Beauchamp, Nath, & Pasalar, 2010). In summary, for sev- eral good reasons, TLE, a neurological disease affecting "emotional" areas, may be considered a good and conve- nient model to study emotional-processing disturbances and hemispheric dominance.

According to the right-hemisphere model (RHM), the right hemisphere is responsible for the perception, expres- sion, and experience of emotions (Borod, Koff, & Caron, 1983; Gainotti, 1983; Heilman & Bowers, 1990;Wager, Phan, Liberzon, & Taylor, 2003). …

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