Signal Enhancement in the Output Stage of the Basal Ganglia by Synaptic Short-Term Plasticity in the Direct, Indirect, and Hyperdirect Pathways.

Signal enhancement in the output stage of the basal ganglia by synaptic short-term plasticity in the direct, indirect, and hyperdirect pathways.

Front Comput Neurosci. 2013; 7: 76
Lindahl M, Kamali Sarvestani I, Ekeberg O, Kotaleski JH

Many of the synapses in the basal ganglia display short-term plasticity. Still, computational models have not yet been used to investigate how this affects signaling. Here we use a model of the basal ganglia network, constrained by available data, to quantitatively investigate how synaptic short-term plasticity affects the substantia nigra reticulata (SNr), the basal ganglia output nucleus. We find that SNr becomes particularly responsive to the characteristic burst-like activity seen in both direct and indirect pathway striatal medium spiny neurons (MSN). As expected by the standard model, direct pathway MSNs are responsible for decreasing the activity in SNr. In particular, our simulations indicate that bursting in only a few percent of the direct pathway MSNs is sufficient for completely inhibiting SNr neuron activity. The standard model also suggests that SNr activity in the indirect pathway is controlled by MSNs disinhibiting the subthalamic nucleus (STN) via the globus pallidus externa (GPe). Our model rather indicates that SNr activity is controlled by the direct GPe-SNr projections. This is partly because GPe strongly inhibits SNr but also due to depressing STN-SNr synapses. Furthermore, depressing GPe-SNr synapses allow the system to become sensitive to irregularly firing GPe subpopulations, as seen in dopamine depleted conditions, even when the GPe mean firing rate does not change. Similar to the direct pathway, simulations indicate that only a few percent of bursting indirect pathway MSNs can significantly increase the activity in SNr. Finally, the model predicts depressing STN-SNr synapses, since such an assumption explains experiments showing that a brief transient activation of the hyperdirect pathway generates a tri-phasic response in SNr, while a sustained STN activation has minor effects. This can be explained if STN-SNr synapses are depressing such that their effects are counteracted by the (known) depressing GPe-SNr inputs. HubMed – depression


Enhanced representation of spectral contrasts in the primary auditory cortex.

Front Syst Neurosci. 2013; 7: 21
Catz N, Noreña AJ

The role of early auditory processing may be to extract some elementary features from an acoustic mixture in order to organize the auditory scene. To accomplish this task, the central auditory system may rely on the fact that sensory objects are often composed of spectral edges, i.e., regions where the stimulus energy changes abruptly over frequency. The processing of acoustic stimuli may benefit from a mechanism enhancing the internal representation of spectral edges. While the visual system is thought to rely heavily on this mechanism (enhancing spatial edges), it is still unclear whether a related process plays a significant role in audition. We investigated the cortical representation of spectral edges, using acoustic stimuli composed of multi-tone pips whose time-averaged spectral envelope contained suppressed or enhanced regions. Importantly, the stimuli were designed such that neural responses properties could be assessed as a function of stimulus frequency during stimulus presentation. Our results suggest that the representation of acoustic spectral edges is enhanced in the auditory cortex, and that this enhancement is sensitive to the characteristics of the spectral contrast profile, such as depth, sharpness and width. Spectral edges are maximally enhanced for sharp contrast and large depth. Cortical activity was also suppressed at frequencies within the suppressed region. To note, the suppression of firing was larger at frequencies nearby the lower edge of the suppressed region than at the upper edge. Overall, the present study gives critical insights into the processing of spectral contrasts in the auditory system. HubMed – depression



Depress Anxiety. 2013 Jun 25;
Forbes D, Alkemade N, Mitchell D, Elhai JD, McHugh T, Bates G, Novaco RW, Bryant R, Lewis V

Anger is a common emotional sequel in the aftermath of traumatic experience. As it is associated with significant distress and influences recovery, anger requires routine screening and assessment. Most validated measures of anger are too lengthy for inclusion in self-report batteries or as screening tools. This study examines the psychometric properties of a shortened 5-item version of the Dimensions of Anger Reactions (DAR), an existing screening tool.Responses to the DAR-5 were analysed from a sample of 486 college students with and without a history of trauma exposure.The DAR-5 demonstrated strong internal reliability and concurrent validity with the State Trait Anger Expression Inventory-2 (STAXI-2). Confirmatory factor analysis supported a single factor model of the DAR-5 for the trauma-exposed and nontrauma subsamples. A screening cut-off point of 12 on the DAR-5 successfully differentiated high and low scorers on STAXI-2 Trait Anger and PCL posttraumatic stress scores. Further discriminant validity was found with depression symptom scores.The results support use of the DAR-5 for screening for anger when a short scale is required. HubMed – depression


Interpersonal Factors Associated with Depression in Adolescents: Are These Consistent with Theories Underpinning Interpersonal Psychotherapy?

Clin Psychol Psychother. 2013 Jun 26;
O’Shea G, Spence SH, Donovan CL

The aim of this study was to investigate whether depressed adolescents differed from non-depressed adolescents in terms of constructs consistent with those that are proposed to underpin interpersonal psychotherapy. In particular, it was hypothesized that compared with non-depressed adolescents, depressed adolescents would demonstrate a greater number of negative life events associated with interpersonal loss and major life transitions, a more insecure attachment style and poorer communication skills, interpersonal relationships and social support. Thirty-one clinically diagnosed depressed adolescents were matched with 31 non-depressed adolescents on age, gender and socio-economic status. The 62 participants were aged between 12 and 19?years and comprised 18 male and 44 female adolescents. On a self-report questionnaire, depressed adolescents reported a greater number of negative interpersonal life events, a less secure attachment style and scored higher on all insecure attachment styles compared with the non-depressed adolescents. In addition, depressed adolescents demonstrated lower levels of social skill (on both adolescent and parent report), a poorer quality of relationship with parents (on both adolescent and parent report) and lower social competence (adolescent report only). Parents of depressed adolescents also reported more negative parental attitudes and behaviours towards their adolescent compared with parents of non-depressed adolescents. Thus, the results of this study are consistent with the constructs underlying interpersonal psychotherapy and suggest their usefulness in the assessment, conceptualization and treatment of adolescent depression. Clinical implications are discussed. Copyright © 2013 John Wiley & Sons, Ltd.Issues relating to interpersonal stress and loss, poor interpersonal relationships, insecure attachment style, and poor social skills are evident among depressed adolescents in comparison with their non-depressed peers.Although it is not clear whether these factors are causal in the development of depression or if they reflect a consequence or concomitant of the disorder, it is important that clinicians consider these variables in the case formulation.Interpersonal psychotherapy addresses these variables through a focus on handling interpersonal conflicts, role transitions and interpersonal losses, and building social support and social skills. HubMed – depression