Emotion Recognition in Low-Spatial Frequencies Is Partly Preserved following Traumatic Brain Injury

Abstract

After a Traumatic Brain Injury (TBI), emotion recognition is typically impaired. This is commonly attributed to widespread multifocal damage in cortical areas involved in emotion processing as well as to Diffuse Axonal Injury (DAI). However, current models suggest that emotional recognition is subserved by a distributed network cantered on the amygdala, which involves both cortical and subcortical structures. While the cortical system is preferentially tuned to process high spatial frequencies, the subcortical networks are more sensitive to low-spatial frequencies. The aim of this study was to evaluate whether emotion perception from low-spatial frequencies underpinning the subcortical system is relatively preserved in TBI patients. We tested a group of 14 subjects with severe TBI and 20 matched healthy controls. Each participant was asked to recognize the emotion expressed by each stimulus that consisted of happy and fearful faces, filtered for their low and high spatial frequencies components. Results in TBI patients' performances showed that low-spatial frequency expressions were recognized with higher accuracy and faster reaction times when compared to high spatial frequency stimuli. On the contrary, healthy controls did not show any effect in the two conditions, neither for response accuracy nor for reaction times. The outcomes of this study indicate that emotion perception from low-spatial frequencies is relatively preserved in TBI, thereby suggesting spare of functioning in the subcortical system in mediating emotion recognition.

Figure 1

Lesion reconstruction images from MRI or CT scans projected onto the normalized MNI template for the 10 TBI patients with detectable focal lesions.

Figure 2

Location and overlap of brain lesions projected onto axial slices of the standard MNI brain (a). The arrows indicate the location of the amygdala (b), pulvinar (c), and superior colliculus (d) and document that these structures were spared in all patients with focal lesions.

Figure 3

Example of happy and fearful faces unfiltered (BSF), filtered by low-spatial frequencies (LSF) and by high spatial frequencies (HSF).

Figure 4

TBI participants' mean accuracy (filled squares) and single patients' performance (empty circles) in the three spatial frequency conditions for happy and fearful faces separately.

Figure 5

Healthy controls' mean accuracy (filled squares) and single participants' performance (empty circles) in the three spatial frequency conditions for happy and fearful faces separately.

Figure 6

TBI participants' mean reaction times (filled squares) and single patients' performance (empty circles) in the three spatial frequency conditions for happy and fearful faces separately.

Figure 7

Healthy controls' mean reaction times (filled squares) and single participants' performance (empty circles) in the three spatial frequency conditions for happy and fearful faces separately.