"Fotografie" della depressione

Questo articolo scritto da un neurologo parla di "Neuroimaging of
depression". L'argomento mi pare affascinante. Vedi in particolare il
capitolo sul ruolo dell'amigdala, che mi par di capire sia in un certo
senso la parte del cervello depositaria delle "aspettative negative",
correggetemi se sbaglio. Mi chiedo anche se queste ricerche di neuroimaging
possano aprire nuove prospettive terapeutiche in concreto. Che ne pensate?

http://yassermetwally.wordpress.com/neuroimaging-of-depression/

[...]

The Amygdala

One of the most consistent neuroimaging findings in patients with
depression is an increase in the amygdala activation, particularly in the
left hemisphere, both at rest and during emotional processing with or
without sad mood induction [26,41,42,45,46]. Increased amygdalar activity
has been described in response to sad [41,42,45,47], as well as happy
stimuli [26], and also during the expectation of a sad stimulus [46].
Further, a positive correlation has been reported between clinical
symptomatology and amygdalar activity before pharmacologic treatment
[48,49]. A reduction in amygdalar activity was demonstrated in patients
whose symptoms had remitted following standard antidepressant therapy
[41,49,50]. Interestingly, increased amygdala activation persisted if
symptomatology persisted during treatment [46]. It has been proposed that
increased left amygdalar activation in depressive disorders may be
associated with a dysfunction in the neurotransmitter modulatory systems
[51].

The amygdala is a critical brain area for ascribing emotional significance
to stimuli and influencing affective responsiveness and emotional learning
[52,53]. Neuroimaging studies of healthy adults have shown that the
amygdala often produces increased activation in response to aversive
conditioning [54,55] and is activated consistently during the perception of
fearful facial expressions [56,57,58], but also during perception of
positive stimuli [59]. Taken together, the fMRI studies described earlier
in this article suggest that abnormal amygdala activation could mediate the
sustained processing of emotional (particularly sad) information noted in
depressed patients and contribute to an array of depressive symptoms.
Depressed patients demonstrate elaborative processing of negative
information, forming associations with a broader number of stimuli [26,47].
A positive correlation has been described between amygdalar activity and
the memory for emotional stimuli, particularly for negatively valenced
stimuli [60] (for review see references [61,62]). The increased and
sustained amygdalar activation observed in depressed patients may
contribute to their clinical symptoms and may be the result of implicit and
explicit attentional biases toward sad stimuli [63], increased emotional
arousal [64], and/or enhanced rehearsal of negative information. Moreover,
abnormal amygdalar activation during the expectation of a negative stimulus
could be related to altered cognition and negative attitudes toward the
future [46].
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