Anhedonia i układ nagrody cz2

23.06.09, 13:40
Najświeższe badanie na ten temat 2009 Jun 16

Neural representation of reward in recovered depressed patients.


McCabe C, Cowen PJ, Harmer CJ.

University Department of Psychiatry, Warneford Hospital, University
of Oxford, Oxford, UK, ciara.mccabe@psych.ox.ac.uk.

INTRODUCTION: Anhedonia, a loss of interest and pleasure in normally
rewarding stimuli, is a key diagnostic criterion for major
depression. It has been suggested that deficits in the processing of
reward-relevant stimuli could represent an endophenotype for
depression. We hypothesized that people at risk of depression by
virtue of a personal history of the illness would show impaired
neural responses to a primary rewarding stimulus. MATERIALS AND
METHODS: Using functional magnetic resonance imaging, we measured
the neural response to the sight and flavor of chocolate, and their
combination, in 13 unmedicated recovered patients with a history of
major depression and 14 healthy controls matched for age and gender.
We also examined a control aversive condition consisting of the
sight of moldy strawberries and a corresponding unpleasant taste.
Participants simultaneously recorded subjective ratings
of "pleasantness," "intensity," and "wanting." RESULTS AND
DISCUSSION: Despite no differences between the groups in stimulus
ratings, patients showed decreased neural responses to the pleasant
stimulus in the ventral striatum and increases in the caudate
nucleus to the aversive stimulus. Furthermore, patients had a
diminished neural supralinearity response (the potentiation produced
by simultaneous presentation of the sight and flavor of the stimuli)
in the prefrontal cortex for both aversive and pleasant conditions.
Patients recovered from depression appear to have deficits in the
neural basis of reward and may also have impairments in the cross-
modal integration of sensory stimuli. CONCLUSION: These findings
support the view that abnormal neural responses to reward may be an
endophenotype for depression and a potential target for intervention
and prevention strategies.
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Bardzo ciekawe jest to, że pacjenci byli jakby wyleczeni, oraz że
ich oceny bodzców nie rózniły się, czyli, że w zasadzie nie mieli
anhedonii, to mimo to ich mózgi reagowały inaczej na bodźce, zarówno
te przyjemne jak i nieprzyjemne.
------

The role of the nucleus accumbens and rostral anterior cingulate
cortex in anhedonia: integration of resting EEG, fMRI, and
volumetric techniques.


Wacker J, Dillon DG, Pizzagalli DA.

Department of Psychology, Philipps-Universitaet, Marburg, Germany.

Anhedonia, the reduced propensity to experience pleasure, is a
promising endophenotype and vulnerability factor for several
psychiatric disorders, including depression and schizophrenia. In
the present study, we used resting electroencephalography,
functional magnetic resonance imaging, and volumetric analyses to
probe putative associations between anhedonia and individual
differences in key nodes of the brain's reward system in a non-
clinical sample. We found that anhedonia, but not other symptoms of
depression or anxiety, was correlated with reduced nucleus accumbens
(NAcc) responses to rewards (gains in a monetary incentive delay
task), reduced NAcc volume, and increased resting delta current
density (i.e., decreased resting activity) in the rostral anterior
cingulate cortex (rACC), an area previously implicated in positive
subjective experience. In addition, NAcc reward responses were
inversely associated with rACC resting delta activity, supporting
the hypothesis that delta might be lawfully related to activity
within the brain's reward circuit. Taken together, these results
help elucidate the neural basis of anhedonia and strengthen the
argument for anhedonia as an endophenotype for depression.

Reduced caudate and nucleus accumbens response to rewards in
unmedicated individuals with major depressive disorder.


Pizzagalli DA, Holmes AJ, Dillon DG, Goetz EL, Birk JL, Bogdan R,
Dougherty DD, Iosifescu DV, Rauch SL, Fava M.

Department of Psychology, Harvard University, 1220 William James
Hall, 33 Kirkland St., Cambridge, MA 02138, USA. dap@wjh.harvard.edu

OBJECTIVE: Major depressive disorder is characterized by impaired
reward processing, possibly due to dysfunction in the basal ganglia.
However, few neuroimaging studies of depression have distinguished
between anticipatory and consummatory phases of reward processing.
Using functional MRI (fMRI) and a task that dissociates anticipatory
and consummatory phases of reward processing, the authors tested the
hypothesis that individuals with major depression would show reduced
reward-related responses in basal ganglia structures. METHOD: A
monetary incentive delay task was presented to 30 unmedicated
individuals with major depressive disorder and 31 healthy comparison
subjects during fMRI scanning. Whole-brain analyses focused on
neural responses to reward-predicting cues and rewarding outcomes
(i.e., monetary gains). Secondary analyses focused on the
relationship between anhedonic symptoms and basal ganglia volumes.
RESULTS: Relative to comparison subjects, participants with major
depression showed significantly weaker responses to gains in the
left nucleus accumbens and the caudate bilaterally. Group
differences in these regions were specific to rewarding outcomes and
did not generalize to neutral or negative outcomes, although
relatively reduced responses to monetary penalties in the major
depression group emerged in other caudate regions. By contrast,
evidence for group differences during reward anticipation was
weaker, although participants with major depression showed reduced
activation to reward cues in a small sector of the left posterior
putamen. In the major depression group, anhedonic symptoms and
depression severity were associated with reduced caudate volume
bilaterally. CONCLUSIONS: These results suggest that basal ganglia
dysfunction in major depression may affect the consummatory phase of
reward processing. Additionally, morphometric results suggest that
anhedonia in major depression is related to caudate volume.

Pewinie dla ochwatego i dala.tata et al. te badania nic nie
udowadniają, cóż jestem świadom, że jak ktoś jest uparty to nic go
nie przekona. Niech każdy oceni sobie sam co z tych badań wynika.
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