Physiological reactivity and the perception of emotional stimuli as they relate to social adaptive functioning after traumatic brain injury / y Melonie Jane Hopkins.
Abstract
Traumatic brain injury (TBI) often affects social adaptive functioning and
these changes in social adaptability are usually associated with general damage to the
frontal cortex. Recent evidence suggests that certain neurons within the orbitofrontal
cortex appear to be specialized for the processing of faces and facial expressions. The
orbitofrontal cortex also appears to be involved in self-initiated somatic activation to
emotionally-charged stimuli. According to Somatic Marker Theory (Damasio, 1994),
the reduced physiological activation fails to provide an individual with appropriate
somatic cues to personally-relevant stimuli and this, in turn, may result in maladaptive
behaviour. Given the susceptibility of the orbitofrontal cortex in TBI, it was
hypothesized that impaired perception and reactivity to socially-relevant information
might be responsible for some of the social difficulties encountered after TBL
Fifteen persons who sustained a moderate to severe brain injury were
compared to age and education matched Control participants. In the first study, both
groups were presented with photographs of models displaying the major emotions and
either asked to identify the emotions or simply view the faces passively. In a second
study, participants were asked to select cards from decks that varied in terms of how
much money could be won or lost. Those decks with higher losses were considered
to be high-risk decks. Electrodermal activity was measured concurrently in both
situations.
Relative to Controls, TBI participants were found to have difficulty
identifying expressions of surprise, sadness, anger, and fear. TBI persons were also
found to be under-reactive, as measured by electrodermal activity, while passively
viewing slides of negative expressions. No group difference,in reactivity to high-risk
card decks was observed.
The ability to identify emotions in the face and electrodermal reactivity to
faces and to high-risk decks in the card game were examined in relationship to social monitoring and empathy as described by family members or friends on the Brock
Adaptive Functioning Questionnaire (BAFQ). Difficulties identifying negative
expressions (i.e., sadness, anger, fear, and disgust) predicted problems in monitoring
social situations. As well, a modest relationship was observed between hypo-arousal
to negative faces and problems with social monitoring. Finally, hypo-arousal in the
anticipation of risk during the card game related to problems in empathy.
In summary, these data are consistent with the view that alterations in the
ability to perceive emotional expressions in the face and the disruption in arousal to
personally-relevant information may be accounting for some of the difficulties in
social adaptation often observed in persons who have sustained a TBI. Furthermore,
these data provide modest support for Damasio's Somatic Marker Theory in that
physiological reactivity to socially-relevant information has some value in predicting
social function. Therefore, the assessment of TBI persons, particularly those with
adaptive behavioural problems, should be expanded to determine whether alterations
in perception and reactivity to socially-relevant stimuli have occurred. When this is
the case, rehabilitative strategies aimed more specifically at these difficulties should
be considered.