Hippocampal Non-Theta-Contingent Eyeblink Classical Conditioning: A Model System for Neurobiological Dysfunction

The homogenous hippocampus: How hippocampal cells process available and potential goals

We present here a view of the firing patterns of hippocampal cells that is contrary, both functionally and anatomically, to conventional wisdom. We argue that the hippocampus responds to efference copies of goals encoded elsewhere; and that it uses these to detect and resolve conflict or interference between goals in general. While goals can involve space, hippocampal cells do not encode spatial (or other special types of) memory, as such. We also argue that the transverse circuits of the hippocampus operate in an essentially homogeneous way along its length. The apparently different functions of different parts (e.g. memory retrieval versus anxiety) result from the different (situational/motivational) inputs on which those parts perform the same fundamental computational operations. On this view, the key role of the hippocampus is the iterative adjustment, via Papez-like circuits, of synaptic weights in cell assemblies elsewhere.

A cross-cultural fMRI investigation of cannabis approach bias in individuals with cannabis use disorder

Introduction

As cannabis policies and attitudes become more permissive, it is crucial to examine how the legal and social environment influence neurocognitive mechanisms underlying cannabis use disorder (CUD). The current study aimed to assess whether cannabis approach bias, one of the mechanisms proposed to underlie CUD, differed between environments with distinct recreational cannabis policies (Amsterdam, The Netherlands (NL) and Dallas, Texas, United States of America (TX)) and whether individual differences in cannabis attitudes affect those differences.

Methods

Individuals with CUD (NL-CUD: 64; TX-CUD: 48) and closely matched non-using controls (NL-CON: 50; TX-CON: 36) completed a cannabis approach avoidance task (CAAT) in a 3T MRI. The cannabis culture questionnaire was used to measure cannabis attitudes from three perspectives: personal, family/friends, and state/country attitudes.

Results

Individuals with CUD demonstrated a significant behavioral cannabis-specific approach bias. Individuals with CUD exhibited higher cannabis approach bias-related activity in clusters including the paracingulate gyrus, anterior cingulate cortex, and frontal medial cortex compared to controls, which was no longer significant after controlling for gender. Site-related differences emerged in the association between cannabis use quantity and cannabis approach bias activity in the putamen, amygdala, hippocampus, and insula, with a positive association in the TX-CUD group and a negative association in the NL-CUD group. This was not explained by site differences in cannabis attitudes.

Conclusions

Pinpointing the underlying mechanisms of site-related differences-including, but not limited to, differences in method of administration, cannabis potency, or patterns of substance co-use-is a key challenge for future research.

Reasons for recovery and readiness to change among adolescents and young adults engaging in self-injury

Background

Non-suicidal self-injury (NSSI) typically begins during adolescence and the process of treatment and recovery can be challenging. We examine NSSI through the lens of the Transtheoretical Model of Change, a framework that views the process of change as five stages, with differing degrees of readiness to change.

Methods

Thirty participants, both adolescents and young adults (14 to 35 years), were recruited from a tertiary care neuropsychiatric hospital. The participants were predominantly female and had self-injured at least once in the last year. They completed the Inventory of Statements about Self Injury, the University of Rhode Island Change Assessment and the Reasons to Stop Self-Injury Questionnaire.

Results

Seventy-three percent were in the contemplation stage with respect to their readiness to change, while the rest were in the pre-contemplation stage. Participants endorsed a range of vulnerability and resilience related reasons to stop injuring; reasons related to self-efficacy, the addictive nature of NSSI, self-efficacy and impact on interpersonal relationships were prominent levers for the recovery process. Preliminary trends indicated that participants in the contemplation stage endorsed reasons to stop self-injuring more strongly than those in pre-contemplation.

Conclusion

The findings carry implications for assessment, the amplification of reasons for recovery and individualized interventions to support the recovery process with individuals who engage in NSSI.

PHQ-9 DIAGNOSTIC ACCURACY AND OPTIMAL CUT-OFF FOR DEPRESSION AMONG PATIENTS WITH STROKE IN NIGERIA

Background

Depression is one of the most common and devastating consequences among stroke survivors. In spite of the availability of treatment for depression, the non- or under-detection precludes patients from benefiting from it.

Objectives

This study sought to validate the Patient Health Questionnaire (PHQ- 9) as a tool for detecting depression among patients with stroke.

Methodology

A cross-sectional design comprising of adult patients diagnosed with stroke, who were attending the Neurology out-patient clinic of the University of Port Harcourt Teaching Hospital was employed in the study. The Receiver Operator Characteristics (ROC) curve and validity tests were performed using the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders (SCID-DSM IV) as the gold standard. The optimal PHQ-9 cut-off was determined using Youden Index. Kappa statistics was performed at p<0.05.

Results

The study had a total of 197 stroke cases with PHQ-9 and SCID-DSM IV findings. The median age was 54 years (range: 35-76 years). ROC Curve for PHQ-9 revealed an Area under the Curve (AUC) value of 0.93(95% CI: 0.88- 0.98). The optimal cut off value of six was obtained based on Youden Index. Sensitivity, specificity, positive predictive and negative predictive values at the optimal cut-off were 88.7%, 93.1%, 82.5% and 95.7% respectively. The Kappa statistics yielded 0.80 (95% CI: 0.68-0.86).

Conclusion

PHQ-9 is a useful screening tool for identifying depression among patients with stroke. An optimal cut-off score of six for PHQ-9 should be adopted for patients with stroke in Nigeria to identify depression, and the provision of holistic care.

Hippocampal non-theta state: The "Janus face" of information processing

The vast majority of studies on hippocampal rhythms have been conducted on animals or humans in situations where their attention was focused on external stimuli or solving cognitive tasks. These studies formed the basis for the idea that rhythmical activity coordinates the work of neurons during information processing. However, at rest, when attention is not directed to external stimuli, brain rhythms do not disappear, although the parameters of oscillatory activity change. What is the functional load of rhythmical activity at rest? Hippocampal oscillatory activity during rest is called the non-theta state, as opposed to the theta state, a characteristic activity during active behavior. We dedicate our review to discussing the present state of the art in the research of the non-theta state. The key provisions of the review are as follows: (1) the non-theta state has its own characteristics of oscillatory and neuronal activity; (2) hippocampal non-theta state is possibly caused and maintained by change of rhythmicity of medial septal input under the influence of raphe nuclei; (3) there is no consensus in the literature about cognitive functions of the non-theta-non-ripple state; and (4) the antagonistic relationship between theta and delta rhythms observed in rodents is not always observed in humans. Most attention is paid to the non-theta-non-ripple state, since this aspect of hippocampal activity has not been investigated properly and discussed in reviews.

Spontaneous recovery of conditioned eyeblink responses is associated with transiently decreased cerebellar theta activity in guinea pigs

Behavioral studies have demonstrated that extinguished conditioned eyeblink responses (CR) can spontaneously recover after extinction. However, the neural mechanisms underlying this process are still unclear. We have shown that spontaneous cerebellar theta activity was predictive of subsequent CR extinction. Here, we sought to further evaluate the association between spontaneous recovery and cerebellar theta activity in behaving guinea pigs. It was found that trace conditioning training significantly diminished the degree of spontaneous recovery during extinction sessions as compared to delay training. Moreover, by recording local field potential in the cerebellum of guinea pigs undergoing an eyeblink conditioning extinction task, we found that spontaneous recovery of delay-paradigm CRs was associated with transiently decreased CS-evoked theta activity in the cerebellum. These findings suggest that decreased CS-evoked cerebellar theta activity may contribute to the neural process that is important for the spontaneous recovery of extinguished motor memory. Future studies are needed to clarify the neural mechanism underlying changed cerebellar theta activity during altered behavioral contingencies.

Sedentary behavior and physical activity predicting depressive symptoms in adolescents beyond attributes of health-related physical fitness

BACKGROUND

Sedentary behavior (SB), physical activity (PA), and attributes of physical fitness have been shown to be related to depressive symptoms in adolescents. The purpose of the present study was to investigate whether SB and fitness-producing activity predicted depression in active adolescents over and above gender and fitness attributes.

METHODS

Participants were 249 adolescents (age: 12.85 ± 0.89 years, mean ± SD) from 3 public middle schools who wore Actical accelerometers to assess their SB and PA. Participants also completed the FITNESSGRAM health-related fitness assessment and a brief depression questionnaire. A 3-step hierarchical regression analysis was conducted with gender and fitness attributes (i.e., body mass index (BMI), maximal volume oxygen uptake (VO_2max), curlups, and pushups), moderate- and vigorous-intensity activity, and SB entered in respective steps.

RESULTS

Regression analysis indicated activity variables (i.e., moderate- and vigorous-intensity activity) significantly predicted depression (ΔR ² = 0.12, p < 0.01) beyond gender and fitness attributes. Overall, gender, fitness attributes, activity variables, SB explained 31% of the variance in depression. Structure coefficients revealed VO_2max (r _s = -0.77), moderate-intensity activity (r _s = -0.67), vigorous-intensity activity (r _s = -0.81), and SB (r _s = 0.57) were substantially correlated with the criterion variable; thus, they were the strongest predictors of depression.

CONCLUSION

The findings of the current study indicated SB and PA were both significant predictors of depression; however, sufficient fitness-producing activity and adequate cardiorespiratory fitness may nullify the negative influence of SB on depressive symptoms in active adolescents.