It manifests as a failure to express feelings either verbally or nonverbally, especially when talking about issues that would normally be expected to engage emotions.
Whereas, individuals with schizophrenia with blunted affect show activation in the following brain regions when shown emotionally negative pictures: midbrain, pons, anterior temporal pole and extrastriate visual cortex.
[12] Individuals with schizophrenia with flat affect show decreased activation in the limbic system when viewing emotional stimuli.
In individuals with schizophrenia with blunted affect neural processes begin in the occipitotemporal region of the brain and go through the ventral visual pathway and the limbic structures until they reach the inferior frontal areas.
[12] Parts of the brainstem are responsible for passive emotional coping strategies characterized by disengagement or withdrawal from the external environment (quiescence, immobility, hyporeactivity), similar to what is seen in blunted affect.
Individuals with schizophrenia with blunted affect show activation of the brainstem during fMRI scans, particularly the right medulla and the left pons, when shown "sad" film excerpts.
When the connectivity between the midbrain and the medial prefrontal cortex is compromised in individuals with schizophrenia with blunted affect an absence of emotional reaction to external stimuli results.
[15] This lack of PFC activity in people with schizophrenia with blunted affect has been postulated to be related to the impaired emotional processing observed in such individuals.
Another study found that when speaking, individuals with schizophrenia with flat affect demonstrate less inflection than normal controls and appear to be less fluent.
[25] Post-traumatic stress disorder (PTSD) was previously known to cause negative feelings, such as depressed mood, re-experiencing and hyperarousal.
However, recently, psychologists have started to focus their attention on the blunted affects and also the decrease in feeling and expressing positive emotions in PTSD patients.
[26] Blunted affect is a response to PTSD, it is considered one of the central symptoms in post-traumatic stress disorders and it is often seen in veterans who served in combat zones.
[29][30] In making assessments of mood and affect the clinician is cautioned that "it is important to keep in mind that demonstrative expression can be influenced by cultural differences, medication, or situational factors";[5] while the layperson is warned to beware of applying the criterion lightly to "friends, otherwise [he or she] is likely to make false judgments, in view of the prevalence of schizoid and cyclothymic personalities in our 'normal' population, and our [US] tendency to psychological hypochondriasis".
[31] R. D. Laing in particular stressed that "such 'clinical' categories as schizoid, autistic, 'impoverished' affect ... all presuppose that there are reliable, valid impersonal criteria for making attributions about the other person's relation to [his or her] actions.
[34] "If the amygdala is severed from the rest of the brain, the result is a striking inability to gauge the emotional significance of events; this condition is sometimes called 'affective blindness'".