Mechanisms of cognitive-behavioral therapy for obsessive-compulsive disorder involve robust and extensive increases in brain network connectivity

Cognitive-behavioral therapy (CBT) is effective for obsessive compulsive disorder (OCD); however, little is understood about its mechanisms related to brain network connectivity. We examined connectivity changes from resting-state functional magnetic resonance imaging data pre-to-post-CBT in 43 OCD participants, randomized to receive either 4 weeks of intensive CBT or 4 weeks waitlist followed by 4 weeks of CBT, and 24 healthy controls before and after 4 weeks of no treatment. Network-based-statistic analysis revealed large-magnitude increases in OCD connectivity in eight networks. Strongest increases involved connectivity between the cerebellum and caudate/putamen, and between the cerebellum and dorsolateral/ventrolateral prefrontal cortices. Connectivity increases were associated with increased resistance to compulsions. Mechanisms of CBT may involve enhanced cross-network integration, both within and outside of classical cortico-striatal-thalamo-cortical regions; those involving cerebellar to striatal and prefrontal regions may reflect acquisition of new non-compulsive goal-directed behaviors and thought patterns. Our findings have implications for identifying targets for enhancing treatment efficacy and monitoring treatment progress.

Functional connectivity for face processing in individuals with body dysmorphic disorder and anorexia nervosa

BACKGROUND

Body dysmorphic disorder (BDD) and anorexia nervosa (AN) are both characterized by distorted perception of appearance. Previous studies in BDD suggest abnormalities in visual processing of own and others' faces, but no study has examined visual processing of faces in AN, nor directly compared the two disorders in this respect.

METHOD

We collected functional magnetic resonance imaging data on 60 individuals of equivalent age and gender in each of three groups--20 BDD, 20 weight-restored AN, and 20 healthy controls (HC)--while they viewed images of others' faces that contained only high or low spatial frequency information (HSF or LSF). We tested hypotheses about functional connectivity within specialized sub-networks for HSF and LSF visual processing, using psychophysiological interaction analyses.

RESULTS

The BDD group demonstrated increased functional connectivity compared to HC between left anterior occipital face area and right fusiform face area (FFA) for LSF faces, which was associated with symptom severity. Both BDD and AN groups had increased connectivity compared to HC between FFA and precuneous/posterior cingulate gyrus for LSF faces, and decreased connectivity between FFA and insula. In addition, we found that LSF connectivity between FFA and posterior cingulate gyrus was significantly associated with thoughts about own appearance in AN.

CONCLUSIONS

Results suggest similar abnormal functional connectivity within higher-order systems for face processing in BDD and AN, but distinct abnormal connectivity patterns within occipito-temporal visual networks. Findings may have implications for understanding relationships between these disorders, and the pathophysiology underlying perceptual distortions.

Abnormalities of object visual processing in body dysmorphic disorder

BACKGROUND

Individuals with body dysmorphic disorder (BDD) may have perceptual distortions for their appearance. Previous studies suggest imbalances in detailed relative to configural/holistic visual processing when viewing faces. No study has investigated the neural correlates of processing non-symptom-related stimuli. The objective of this study was to determine whether individuals with BDD have abnormal patterns of brain activation when viewing non-face/non-body object stimuli.

METHOD

Fourteen medication-free participants with DSM-IV BDD and 14 healthy controls participated. We performed functional magnetic resonance imaging (fMRI) while participants matched photographs of houses that were unaltered, contained only high spatial frequency (HSF, high detail) information or only low spatial frequency (LSF, low detail) information. The primary outcome was group differences in blood oxygen level-dependent (BOLD) signal changes.

RESULTS

The BDD group showed lower activity in the parahippocampal gyrus, lingual gyrus and precuneus for LSF images. There were greater activations in medial prefrontal regions for HSF images, although no significant differences when compared to a low-level baseline. Greater symptom severity was associated with lower activity in the dorsal occipital cortex and ventrolateral prefrontal cortex for normal spatial frequency (NSF) and HSF images.

CONCLUSIONS

Individuals with BDD have abnormal brain activation patterns when viewing objects. Hypoactivity in visual association areas for configural and holistic (low detail) elements and abnormal allocation of prefrontal systems for details are consistent with a model of imbalances in global versus local processing. This may occur not only for appearance but also for general stimuli unrelated to their symptoms.

A nitric oxide-independent and beta-adrenergic receptor-sensitive form of metaplasticity limits theta-frequency stimulation-induced LTP in the hippocampal CA1 region

The induction of long-term potentiation (LTP) and long-term depression (LTD) at excitatory synapses in the hippocampus can be strongly modulated by patterns of synaptic stimulation that otherwise have no direct effect on synaptic strength. Likewise, patterns of synaptic stimulation that induce LTP or LTD not only modify synaptic strength but can also induce lasting changes that regulate how synapses will respond to subsequent trains of stimulation. Collectively known as metaplasticity, these activity-dependent processes that regulate LTP and LTD induction allow the recent history of synaptic activity to influence the induction of activity-dependent changes in synaptic strength and may thus have an important role in information storage during memory formation. To explore the cellular and molecular mechanisms underlying metaplasticity, we investigated the role of metaplasticity in the induction of LTP by theta-frequency (5-Hz) synaptic stimulation in the hippocampal CA1 region. Our results show that brief trains of theta-frequency stimulation not only induce LTP but also activate a process that inhibits the induction of additional LTP at potentiated synapses. Unlike other forms of metaplasticity, the inhibition of LTP induction at potentiated synapses does not appear to arise from activity-dependent changes in NMDA receptor function, does not require nitric oxide signaling, and is strongly modulated by beta-adrenergic receptor activation. Together with previous findings, our results indicate that mechanistically distinct forms of metaplasticity regulate LTP induction and suggest that one way modulatory transmitters may act to regulate synaptic plasticity is by modulating metaplasticity.

Postsynaptic complex spike bursting enables the induction of LTP by theta frequency synaptic stimulation

Long-term potentiation (LTP), a persistent enhancement of synaptic transmission that may be involved in some forms of learning and memory, is induced at excitatory synapses in the CA1 region of the hippocampus by coincident presynaptic and postsynaptic activity. Although action potentials back-propagating into dendrites of hippocampal pyramidal cells provide sufficient postsynaptic activity to induce LTP under some in vitro conditions, it is not known whether LTP can be induced by patterns of postsynaptic action potential firing that occur in these cells in vivo. Here we report that a characteristic in vivo pattern of action potential generation in CA1 pyramidal cells known as the complex spike burst enables the induction of LTP during theta frequency synaptic stimulation in the CA1 region of hippocampal slices maintained in vitro. Our results suggest that complex spike bursting may have an important role in synaptic processes involved in learning and memory formation, perhaps by producing a highly sensitive postsynaptic state during which even low frequencies of presynaptic activity can induce LTP.

5-Hz stimulation of CA3 pyramidal cell axons induces a beta-adrenergic modulated potentiation at synapses on CA1, but not CA3, pyramidal cells

In mouse hippocampal slices, long-term potentiation (LTP) at Schaffer collateral fiber synapses onto CA1 pyramidal cells could be induced by brief trains of 5-Hz synaptic stimulation (30 s) or by longer trains of 5-Hz stimulation (3 min) delivered during beta-adrenergic receptor activation. In contrast, 5-Hz stimulation, either alone or in the presence of the beta-adrenergic receptor agonist isoproterenol, failed to induce LTP at associational-commissural (assoc-com) fiber synapses onto CA3 pyramidal cells. Our results suggest that although CA3 pyramidal cells give rise to both the Schaffer collateral fiber synapses in CA1 and the assoc-com fiber synapses in CA3, the induction of LTP at these synapses may be regulated by different activity- and modulatory neurotransmitter-dependent processes.

Activity-dependent beta-adrenergic modulation of low frequency stimulation induced LTP in the hippocampal CA1 region

beta-Adrenergic receptor activation has a central role in the enhancement of memory formation that occurs during heightened states of emotional arousal. Although beta-adrenergic receptor activation may enhance memory formation by modulating long-term potentiation (LTP), a candidate synaptic mechanism involved in memory formation, the cellular basis of this modulation is not fully understood. Here, we report that, in the CA1 region of the hippocampus, beta-adrenergic receptor activation selectively enables the induction of LTP during long trains of 5 Hz synaptic stimulation. Protein phosphatase inhibitors mimic the effects of beta-adrenergic receptor activation on 5 Hz stimulation-induced LTP, suggesting that activation of noradrenergic systems during emotional arousal may enhance memory formation by inhibiting protein phosphatases that normally oppose the induction of LTP.