1 research outputs found
Neural substrate of emotion in man : a study in methodology
Emotional behaviour has several components, which include
emotional perception, emotional expression, autonomic reactivity, and inner
subjective experience. It is hypothesised that these different processes can be
selectively disturbed after brain damage. However, emotional and cognitive
deficits usually co-exist in a particular patient, and the relationship between
cognition and emotion is discussed.
Animal data indicate that, following an initial sensory analysis in
primary and association cortex, a stimulus acquires emotional significance by
interfacing with "limbic" processes through multimodal cortex. Emotional
expressions also develop in the course of similar multistage integrations
between motor and limbic processes. This suggests three possible relationships
between cognitive and emotional deficit. First, an inability to either perceive or
express emotion may be directly due to various primary "non-emotional"
perceptuo-motor deficits. Secondly, damage to neural sites where limbic and
sensori-motor systems interface may produce deficits which are
simultaneously cognitive and emotional. For example, perseverative behaviour
in the Wisconsin Card Sorting Test and inability to control emotional impulses
may be different aspects of a single deficit, which is indissociably cognitive and
emotional. Thirdly, there may be a class of "pure" emotional deficits, which are
not associated with perceptuo-motor or cognitive deficit.
Tests based on the above classification approach were used to
assess the effect of lesion site on emotional functioning. Cognitive function,
emotional perception, emotional expression, subjective response, and
autonomic reactivity were assessed in 48 patients with focal brain lesions, and
10 matched non-brain injured controls. Patients with anterior lesions were
impaired relative to posteriors and controls in emotional perception and
expression. These frontal deficits remained after statistical control of lesion
variables (size, aetiology, and degree of bilateral involvement), and
non-emotional perceptual, motor or cognitive impairments. Though such
statistical controls provide suggestive evidence of a specific emotional deficit,
they cannot completely eliminate the possibility that the frontal deficit is
secondary to perceptuo-motor or cognitive impairment. Experimental
strategies designed to provide more positive evidence of a specific emotional
disorder were employed, and met with partial success.
Dysphasia affected performance on tests of emotional perception
and expression after left brain damage. Following right hemisphere damage,
visual perceptual deficit contributed to impairment in emotional perception.
There were indications that hemispheric perceptual-cognitive asymmetries may
not account for all right-left differences on the emotional subtests. However no
current model of hemispheric emotional asymmetries could fully explain the
present findings. For example, the data on emotional perception supported the
view that the right hemisphere is specialised for attentional/emotional
processes (Heilman et al, 1983), but neglect and emotional expression were not
correlated. Also, the present data generally contradicted the hypothesis that
positive and negative emotions are lateralised in the left and right hemispheres,
respectively.
The final chapter assesses the extent to which the data fit the
proposed system for categorising emotional disorder. Limitations to the
methods used in making this evaluation were discussed, and possible ways of
overcoming these restrictions were briefly considered