|dc.description.abstract||A large variety of social signals, such as facial expression and body language, are
conveyed in everyday interactions and an accurate perception and interpretation of these
social cues is necessary in order for reciprocal social interactions to take place successfully
and efficiently. The present study was conducted to determine whether impairments in
social functioning that are commonly observed following a closed head injury, could at
least be partially attributable to disruption in the ability to appreciate social cues. More
specifically, an attempt was made to determine whether face processing deficits following
a closed head injury (CHI) coincide with changes in electrophysiological responsivity to
the presentation of facial stimuli.
A number of event-related potentials (ERPs) that have been linked specifically to
various aspects of visual processing were examined. These included the N170, an index of
structural encoding ability, the N400, an index of the ability to detect differences in serially
presented stimuli, and the Late Positivity (LP), an index of the sensitivity to affective
content in visually-presented stimuli. Electrophysiological responses were recorded while
participants with and without a closed head injury were presented with pairs of faces
delivered in a rapid sequence and asked to compare them on the basis of whether they
matched with respect to identity or emotion. Other behavioural measures of identity and
emotion recognition were also employed, along with a small battery of standard
neuropsychological tests used to determine general levels of cognitive impairment.
Participants in the CHI group were impaired in a number of cognitive domains that
are commonly affected following a brain injury. These impairments included reduced efficiency in various aspects of encoding verbal information into memory, general slower
rate of information processing, decreased sensitivity to smell, and greater difficulty in the
regulation of emotion and a limited awareness of this impairment.
Impairments in face and emotion processing were clearly evident in the CHI group.
However, despite these impairments in face processing, there were no significant
differences between groups in the electrophysiological components examined. The only
exception was a trend indicating delayed N170 peak latencies in the CHI group (p = .09),
which may reflect inefficient structural encoding processes. In addition, group differences
were noted in the region of the N100, thought to reflect very early selective attention. It
is possible, then, that facial expression and identity processing deficits following CHI are
secondary to (or exacerbated by) an underlying disruption of very early attentional
processes. Alternately the difficulty may arise in the later cognitive stages involved in the
interpretation of the relevant visual information. However, the present data do not allow
these alternatives to be distinguished.
Nonetheless, it was clearly evident that individuals with CHI are more likely than
controls to make face processing errors, particularly for the more difficult to discriminate
negative emotions. Those working with individuals who have sustained a head injury
should be alerted to this potential source of social monitoring difficulties which is often
observed as part of the sequelae following a CHI.||en_US